yacht rudder type

4 Rudder Types for Sailboats

Rudder Types for Sailboats | Life of Sailing

Last Updated by

Daniel Wade

June 15, 2022

A rudder is an ancient piece of technology that people still use to steer sailboats today. Modern sailboats use many different types of rudders.

If you turn the rudder to the left, the stern will turn right, and vice versa. You can use either a steering wheel or a tiller to move the rudder. Not every type of boat has the same kind of rudder, nor should every boat - different boats need significantly different rudders.

There are several different types of rudders in common use. Sailboats use full keel rudders, spade rudders, outboard rudders, and skeg-mounted rudders, plus variations on each type. What type of rudder is best depends on the shape of the hull and the boat's size.

Table of contents

Different rudder types and their advantages

Full keel rudders.

Many sailboats have a full keel rather than a fin keel, which requires a particular type of rudder. A full keel is the standard type of keel, or flat blade at the bottom of a sailboat. A full keel is designed for stability, not speed - it can keep you safe in rough water.

A generation or two ago, nearly all cruising boats had full keels. However, this is no longer true. Many customers today prefer fin keels, which are designed with speed rather than stability in mind.

A fin keel is smaller than a full keel and shaped differently. Fin keels are more popular today because many sailors today never go far from the coast. If you are near the coast, fin keels are relatively safe.

With a full keel sailboat , the rudder appears to be part of the keel. It is attached with a hinge and looks like a continuation of the keel. There may be a hole between the keel and the rudder, where the propeller is, although not all boats use this design.

What is the advantage of a full keel rudder?

A full keel rudder is strong and protects the boat from harm. A full keel rudder helps a boat survive a storm. Any debris floating by will not snag on a full keel rudder as it will snag on some other rudders.

Do full keel rudders have any disadvantages?

It is harder to move a full rudder than to move other types of rudders. Water flowing by the boat puts a great deal of pressure on a full keel rudder and makes the rudder hard to move. It takes a lot of force to push the rudder against the water moving past the boat.

Spade rudders

Spade rudders are for fin keel boats rather than full keel boats. A spade rudder sticks straight down into the water. A spade rudder can rotate left or right with a rudder post that extends into the hull.

Advantages and disadvantages of spade rudders

The most obvious advantage of the spade rudder is that it can be part of a fin keel boat. A full keel rudder requires a full keel - you could not attach a rudder of this type to another type of boat.

It is also not nearly as difficult to turn a spade rudder as it is to turn a full keel rudder. The water does not put all of its force on one side of the rudder, so it does not take as much force to turn it.

One disadvantage is that debris floating in the water can get caught on a spade rudder. Spade rudders are more delicate than full keel rudders in many ways. Debris can damage a spade rudder.

A spade rudder can also be damaged by rough water. Large waves may exert enough pressure on a spade rudder that it will break. A large wave can bend the rudder post, and after that happens, your rudder becomes useless.

Outboard rudders

An outboard rudder is not part of the boat's hull and is mounted outside of it, at the back of the boat. Usually, an outboard rudder is not hooked up to a steering wheel.

Instead, it is hooked up to a tiller, which is a steering lever. A tiller can take a bit of getting used to if you are used to a steering wheel, but a tiller is not hard to use. Many sailors prefer a tiller, especially for smaller boats.

Advantages and disadvantages of outboard rudders

If an outboard rudder is damaged, it is not likely to damage the rest of the boat. Since there is no rudder post running through the hull, damage to the rudder usually won't mean damage to anything else as well.

You may also be able to remove and fix a damaged outboard rudder while you are still out at sea. There is no way to remove a rudder that is part of the hull and beneath the boat, but a rudder attached to the boat with hinges may be possible to fix at sea.

Outboard rudders are not necessarily weaker than and can be stronger than other types of rudders. The hinges that hold an outboard rudder in place may be stronger than a rudder post.

In some ways, an outboard rudder is worse than either a spade rudder or a full keel rudder. Unlike a full keel rudder, things like rope floating in the water can get caught on an outboard rudder. Objects floating by can also hit and damage an outboard rudder more easily than they can damage a more durable full keel rudder.

Compared to a spade rudder, the outboard rudder is harder to turn. The water pressure will always be on one side of the rudder; this is not always the case with spade rudders.

Skeg mounted rudders

Skeg rudders are both durable and possible to use on fin keel rather than full keel boats. Skeg mounted rudders are more durable than the spade rudders you usually find on fin keel boats.

Skeg mounted rudders have the same disadvantage as full keel rudders and outboard rudders, which is that they require more energy to turn. The water will put all of its pressure on one side of the rudder. Only spade rudders avoid this problem.

Is a tiller better than a wheel?

Either for inexperienced or veteran sailors, a tiller can work better. With a tiller, you will get immediate feedback. If you turn a wheel, the boat won't turn right away, which can confuse or annoy a new sailor.

The tiller should be long enough, as it is harder to turn if it is shorter. In strong winds, you need a long lever to turn your boat without it taking a great deal of strength.

It is easier to turn a wheel than to turn a tiller, as there is more leverage with a steering wheel. Therefore, wheels are better for larger boats; as a tiller is harder to turn with a bigger boat.

A tiller's advantage is that it is more responsive than a wheel, even though it is harder to turn. The boat will start to change direction almost immediately if you use a tiller. In racing, it is normal to use a tiller because you can change direction more quickly.

How does a rudder work?

A rudder works through water pressure. If you turn the rudder, the pressure becomes higher on one side of the rudder than the other. The rudder then moves toward the side with the lower pressure, which causes the boat to change direction.

When a sailboat turns, it pivots around a point near the middle of the boat. Both the stern and the bow move simultaneously, with the middle of the boat not moving. You have to take this into account while sailing, or else you might swing the end of your ship into another boat.

What is the purpose of the keel?

The keel keeps the boat stable. Without a keel sticking down from the boat into the water, it would be easy for the wind to push the boat around. Without a keel, the wind could easily push you sideways and make the ship much harder to control.

A keel is also weighted. The keel is full of ballast, which is weight that keeps the boat from flipping over. Without ballast, a boat would be top-heavy and unsafe.

Keels are usually made out of the same material as the rest of the boat - if the boat is aluminum, the keel will be as well. The ballast is usually lead.

While full keels are better in rough weather in most ways, a fin keel does a better job of preventing the wind from blowing your boat around. Wind can create leeway, which is sideways movement of the boat. Leeway is most likely if you are sailing into the wind.

Do rudders often fail at sea?

Yes, a rudder failure is one of the more common hazards you might encounter at sea. Not every sailboat has a good, durable rudder. The rudders on cheap boats, especially cheap fiberglass boats, can fail.

The rudder pole should neither be too weak nor too strong. If the rudder pole is too weak, it will bend easily. If it is too strong, it may damage the hull rather than bend, which is even more dangerous.

A rudder has a metal framework inside of it. If the framework breaks, the rudder will become unusable. With a cheaper boat, the metal framework may not be welded together properly.

Make sure you buy a sailboat that has a reputation for safety. Don't buy the cheapest boat you can find - look into whether or not the boat is safe to take out to sea.

I've personally had thousands of questions about sailing and sailboats over the years. As I learn and experience sailing, and the community, I share the answers that work and make sense to me, here on Life of Sailing.

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What are boat rudders?

Boat rudders are an essential component of the vessel's steering system. They are hydrofoil-like structures located at the stern (rear) of the boat, underwater. The primary function of the rudder is to control the direction of the boat by redirecting the flow of water as the boat moves forward.

The role of boat rudders in steering

Boat rudders play a vital role in steering a ship. When the helmsman turns the wheel or tiller, the rudder changes its angle, redirecting the water flow on one side of the boat, creating more resistance on that side, and causing the boat to turn in the opposite direction.

Types of boat rudders

Spade rudders: Spade rudders are simple and streamlined rudders attached directly to the hull. They are commonly found in modern sailboats and provide excellent maneuverability and responsiveness.

Skeg rudders: Skeg rudders are partially submerged and supported by a skeg, a vertical extension of the hull. These rudders offer increased protection and are often used in larger motorboats and trawlers.

Balanced rudders: Balanced rudders have a portion of the rudder forward of the pivot point, which balances the force applied by the helmsman. This design reduces the effort required to steer the boat.

Barn door rudders: Barn door rudders are large, flat, and wide rudders resembling barn doors. They are commonly seen in traditional fishing vessels and provide excellent control in rough seas.

Spade hung rudders: Spade hung rudders are free-floating rudders attached to the boat only at the top, allowing them to swing freely. They are commonly used in high-performance sailing yachts.

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Components and mechanics of boat rudders

A typical boat rudder consists of several key components:

Rudder blade: The rudder blade is the flat, vertical surface responsible for redirecting the water flow. It is the most critical part of the rudder and comes in various shapes and sizes.

Rudder stock: The rudder stock is a sturdy vertical shaft that connects the rudder blade to the steering mechanism. It provides the necessary support and stability for the rudder.

Tiller or wheel: The tiller or wheel is the steering control operated by the helmsman. When turned, it causes the rudder to change its angle and steer the boat.

Rudder bearings: Rudder bearings are the mechanisms that allow the rudder to pivot smoothly on the rudder stock. Properly lubricated and maintained bearings ensure easy steering.

Steering linkage: The steering linkage consists of rods or cables connecting the tiller or wheel to the rudder stock. It transmits the helmsman's steering inputs to the rudder.

Steering a ship: The interaction between rudder and helm

The process of steering a ship involves a coordinated effort between the rudder and the helm. When the helmsman turns the wheel or tiller, the rudder angle changes, causing a difference in water flow on either side of the boat. This creates a force imbalance, turning the boat in the desired direction.

The effectiveness of the steering system depends on various factors, such as the rudder's size, shape, and angle, the vessel's speed, and the water conditions. Proper coordination between the helmsman and the rudder is essential for precise maneuvering.

Maintaining and repairing boat rudders

Regular maintenance is crucial to ensure the optimal performance and longevity of boat rudders. Here are some maintenance tips:

Inspect for damage: Regularly inspect the rudder blade, stock, and bearings for any signs of wear, damage, or corrosion.

Lubrication: Ensure the rudder bearings are well-lubricated to prevent friction and allow smooth movement.

Antifouling: Apply antifouling paint to the rudder to prevent marine growth, which can negatively impact performance.

Check steering linkage: Inspect and adjust the steering linkage regularly to maintain precise control.

Address issues promptly: If any problems or abnormalities are detected, address them promptly to prevent further damage.

Rudder design innovations

Advancements in technology have led to innovative rudder designs aimed at improving performance and efficiency. Some notable innovations include:

Hydrodynamic profiles: Rudder blades are now designed with advanced hydrodynamic profiles to reduce drag and enhance maneuverability.

Rudder fins: Some rudders are equipped with additional fins or foils to improve stability and minimize yawing motion.

Retractable rudders: Certain sailboats feature retractable rudders, which can be raised when sailing in shallow waters, reducing the risk of grounding.

Steer-by-wire systems: Modern vessels are adopting steer-by-wire systems, replacing traditional mechanical linkages with electronic controls for smoother steering.

The influence of rudder size and shape on turning radius

The size and shape of the rudder directly impact the vessel's turning radius. Larger rudders with greater surface area provide more steering force and can turn the boat more quickly. However, larger rudders also create more drag, which can affect overall speed and fuel efficiency. The optimal rudder size depends on the boat's size, weight, and intended use.

Rudder efficiency and hydrodynamics

The hydrodynamics of the rudder significantly affect its efficiency. Smooth and streamlined rudder designs minimize drag and turbulence, resulting in improved performance and fuel economy. Advanced hydrodynamic analysis and simulation tools help optimize rudder shapes for various vessels and operating conditions.

Common rudder issues and troubleshooting

Like any mechanical component, boat rudders can experience issues over time. Some common problems and troubleshooting tips include:

Stiff steering: If the steering feels stiff or unresponsive, check for obstructions in the rudder bearings or linkage.

Vibrations: Vibrations during steering may indicate misaligned rudder blades or bent rudder stocks.

Leaking bearings: Leaking rudder bearings require immediate attention to prevent water ingress and corrosion.

Excessive play: Excessive play in the rudder could be due to worn steering linkage or loose connections.

Reduced maneuverability: Reduced maneuverability may result from a fouled or damaged rudder blade.

Rudder steering systems

Various steering systems are employed in conjunction with rudders, each offering unique advantages:

Tiller steering: Common in smaller boats, tiller steering directly connects the tiller to the rudder stock, providing direct and responsive control.

Wheel steering: Larger boats often use wheel steering, which utilizes a mechanical or hydraulic system to transfer steering inputs to the rudder.

Hydraulic steering: Hydraulic steering systems offer smooth and effortless steering, ideal for larger vessels.

Electric steering: Electric steering systems, also known as electro-hydraulic steering or electronic power steering (EPS), utilize electric motors to assist in steering the boat. These systems work in conjunction with hydraulic components, making steering more effortless and responsive for the boat operator.

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FAQs about rudders

Types of Rudders Used For Ships

Have you ever noticed that ships, unlike most aeroplanes do not have the same kinds of rudders? The type of rudder that would suit a particular ship is a decision that needs to be based on various factors like hull form , speed, propeller design , the structural arrangement of the stern , clearance between the propeller and the stern, and also a few hydrodynamic factors that dictate the flow of water aft of the propeller.

How ship designers go about deciding the type of rudder, is actually an iterative process. In the concept ship design stage, we actually do not (or cannot afford to) decide the suitable rudder for the ship. So what designers and naval architects do is, estimate a very approximate dimension of the rudder along with the propeller. But as we enter the preliminary design of the ship, the rudder and propeller dimensions are almost fixed, giving us an almost clear idea of the type of rudder that would best fit the design problem.

However, what becomes significantly important from a designer’s point of view, is deciding on the type and location of the rudder, depending on the hull and propeller design.

Let’s try to understand this in a simple way.

The selection of the proper type of rudder is as important as the location of the rudder behind the propeller. The location of the rudder should be such that it is properly oriented within the propeller’s outflow, so as to produce the required turning moment on the ship (Before we go ahead, you might like to read How does a rudder work on a ship? ). A slight change in the rudder type, dimension, and position can bring about a huge variation in the ship’s response to the rudder, as well as the turning ability of the ship. So, optimization is the key.

Types of Rudders For Ships

To broadly categorize conventional rudders, there are two types of ship rudders:

1. Spade or Balanced Rudder

A spade rudder is basically a rudder plate that is fixed to the rudder stock only at the top of the rudder. In other words, the rudder stock (or the axis of the rudder) doesn’t run down along the span of the rudder. The position of the rudder stock along the chord of the rudder (width meaning, from the forward to aft end of the rudder) actually decides whether the rudder is balanced of semi-balanced one. In balanced rudders, (which spade rudders generally are) the rudder stock is at such a position such that 40% of the rudder area is forward of the stock and the remaining is aft of it.

A genuine question that must have come up in your mind is, why is such a position chosen for the rudder stock? The answer lies in simple physics. The centre of gravity of the rudder will lie somewhere close to 40% of its chord length from its forward end. If the axis of the rudder is placed near to this location, the torque required to rotate the rudder will be much lesser than what is required to move it, had the axis been placed at the forward end of the rudder. So, the energy requirement of the steering gear equipment is reduced, therefore lowering the fuel consumption of the ship .

2. Unbalanced Rudders

These rudders have their stocks attached at the forward most point of their span. Unlike balanced rudders, the rudder stock runs along the chord length of the rudder. The reason is simple. In this case, the torque required to turn the rudder is way higher than what is required for a corresponding balanced rudder. So, the topmost part of the rudder has to be fixed to the spindle so as to prevent it from vertical displacement from its natural position. However, unbalanced rudders are not widely used now.

Having discussed the conventional types of rudders, let us shift into something yet more interesting. Researchers and ship operators had found significant problems with the balanced and unbalanced rudders. That is, in case there was a failure of the steering gear mechanism while turning a ship. The rudder would remain still with its angle of attack in that condition. The solution to this was found in designing an optimized Semi-Balanced Rudder.

a. Semi- Balanced Rudder:

If you have been able to visualize a balanced and unbalanced rudder by now, it should be pretty easy to visualize a semi-balanced rudder. In fact, the rudder you see on most ships are semi-balanced in the modern industry. The name semi-balanced itself implies, that the rudder is partly balanced and partly unbalanced. If you refer to the figure below, you’ll see that a portion of the chord length from the top is unbalanced, and the remaining chord length is balanced. Why? Read on.

The top part being unbalanced will help in acting as structural support to the rudder from vertical displacement. And the balanced part will render less torque in swinging the rudder. As a result, a semi-balanced rudder returns to the centreline orientation on its own if the steering gear equipment fails during a turn.

Note in the above figure the Rudder horn. Semi-balanced rudders are again of two types depending upon the depth of the horn (which affects the response and torque characteristics of the rudder). A shallow horn rudder will have a horn which extends hardly half the chord length of the rudder from the top. Whereas, a deep horn rudder will feature a horn deeply extending up to more than 50 % of its chord length from the top of the rudder.

Apart from these, designers have developed some other, rather unconventional rudder systems, which gets more interesting to look into.

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b. Flaps Rudder:

You must have watched an aeroplane’s wings closely. Did you watch those flaps coming in and out of the aft end of the wing? Why do you think they do that? Primarily to change the effective angle of attack of the entire aerofoil section of the wing. You’ll see, during a takeoff, how all the flaps are completely deployed. That actually helps in attaining the effective angle of attack so as to get the maximum lift force.

The same principle, when used in rudders, provides a similar result. Just that, in case of rudders, the flaps are not retractable and they have their significant effects when the rudder is given some angle of attack.

c. Pleuger Rudder:

Perhaps one of the most innovative rudder mechanisms you will ever come across. Suppose you have a ship, too large to be manoeuvre in a basin with size constraints, such that the ship cannot use its propeller during the manoeuvre. This situation often arises in case of large ships operating in space-constrained basins, or in any case of low-speed manoeuvres.

So, a Pleuger rudder (as you can see in the figure below), has a smaller auxiliary propeller housed within it (which runs by a motor). As this housing is mounted on the rudder itself, it generates a thrust (which is smaller than what is generated by the ship’s main engine propeller) in a direction that is oriented along the rudder, therefore allowing effective manoeuvre in slow speed condition.

Such a rudder can be used in normal conditions also. Just that, in normal speeds, the Pleuger is not operated. However, when the Pleuger is run, the main engine propeller must not be operated simultaneously, which will otherwise cause the Pleuger to be torn away.

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Voith Propulsion:

You must be wondering why a propulsion system has popped into the discussion when we are interested in rudder systems. Well, that’s something you need to thank the researchers for. Because this propulsion system is one of a kind, which acts as a rudder itself. It doesn’t need a rudder control surface to change the direction of the ship. How? Read on.

As you can see in the figure below, this propeller has a completely different orientation. To visualize it in simple terms, it consists of a number of hydrofoil blades mounted on a disc, which is in turn, mounted onto the hull. The disc rotates in a horizontal plane, about a horizontal axis, and therefore imparts a rotation into the blades.

But how does a rotation in horizontal plane impart thrust to the ship? Here’s the answer. The blades themselves can be adjusted to have a varying angle of attacks during the operation of the propeller. Depending on that, the direction and magnitude of thrust are varied. Well, if we are manipulating the direction of the thrust too, then we don’t actually need a rudder. Which is actually why a Voith propeller acts as a combined propulsion and steering system for the ship.

It is of no doubt that propulsion and steering systems have been innovated and invented to a great extent when compared to many other aspects in the ship design industry which still require the eyes of modern technological applications. However, as we are transiting into an era of faster, and environmentally safer technologies, newer hull forms are being developed. This has given the industry a wider scope to develop and design newer steering systems for the future.

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Disclaimer: The authors’ views expressed in this article do not necessarily reflect the views of Marine Insight. Data and charts, if used, in the article have been sourced from available information and have not been authenticated by any statutory authority. The author and Marine Insight do not claim it to be accurate nor accept any responsibility for the same. The views constitute only the opinions and do not constitute any guidelines or recommendation on any course of action to be followed by the reader.

The article or images cannot be reproduced, copied, shared or used in any form without the permission of the author and Marine Insight.

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If you can try and give the semi balance rudder pintles clearances which we have to keep maximum and minimum. If you can give me in detail I would be mush happy. Thank you

Distance of rudder from the stern frame should be how much ?

by seeing how we find which type of rudder it is

can u plz explain how does the load is transmitted to rudder from steering gear?????

@Subhash: Please check this article: https://www.marineinsight.com/naval-architecture/understanding-steering-gear-ships/

It was informative. I like your materials very much. I think a few more things could be added here. You mentioned nothing about so called Rotor Rudders, nor the T-Rudders ( combination of Flap + Rotor). Also Schilling rudders, which have very specific hydrodinamic shape, could be mentioned. Combination of Twin Schilling rudders is actually astonishingly mobile.

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The Types of Sailboat Rudders

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Full Keel Rudder

On a sailboat , as the rudder is moved to one side by means of the tiller or steering wheel, the force of the water striking one edge of the rudder turns the stern in the other direction to turn the boat. Different types of rudders have different advantages and disadvantages. The type of rudder is often related to the boat’s type of keel.

Rudder on Full-Keel Sailboat

As shown in this photo, the rudder of a full-keel boat is usually hinged to the aft edge of the keel, making a continuous surface. The engine’s propeller is usually positioned in an aperture between the keel and rudder.

Advantages of Full Keel Rudder

The primary benefit of this rudder configuration is the strength and protection provided to the rudder. It is hinged at top and bottom, well distributing the forces on the rudder. Rope (such as lobster pot warps) or debris in the water cannot snag on the rudder.

Disadvantage of Full Keel Rudder

Because the sideways force of the water on the rudder is entirely behind the rudder’s pivoting point at its leading edge, putting all the force on one side of the rudder, it takes more energy to move the rudder. This is one reason why larger boats seldom have tillers—because it can require much force to “push” the rudder out against the water streaming past the keel.

Spade Rudder

Most fin keel boats have a spade rudder, which extends straight down from the aft hull section. The rudder post comes down through the hull into the rudder itself, allowing the entire rudder to rotate to either side, pivoting around the post.

Advantages of Spade Rudder

The spade rudder is self-standing and does not require a full keel or skeg for its mounting. The rudder post inside the rudder can be moved aft from the leading edge (see next page on Balanced Rudder) so that the force of the water is not all on one side when the rudder is turned. This requires less energy to steer than with a keel- or skeg-mounted rudder.

Disadvantage of Spade Rudder

A spade rudder is more vulnerable to debris or objects in the water, which may strike the rudder and exert a force on the rudder post, the only structure supporting the whole rudder. Even the force of water when the boat “falls” off a wave can exert damaging stress on a spade rudder. If the rudder post is bent, the rudder may jam and become useless.

Balanced Spade Rudder

Note the clear air space at the top of the leading edge of this balanced spade rudder. The rudder post is several inches back from the front of the rudder. When the rudder is turned, the leading edge rotates to one side of the boat while the trailing edge rotates to the other side. While the turning action on the boat is the same, the forces on the helm are more nearly balanced, making it very easy to steer.

Skeg-Mounted Rudder

Some fin keel sailboats have a skeg-mounted rudder like the one shown. The skeg offers the same advantages as a keel mounted rudder: the rudder is protected from objects in the water and has more structural strength than a rudder mounted only on the rudder post.

It also has the same disadvantage: because it is not “balanced” as a spade rudder may be, with water forces distributed on both sides, it requires more force to turn the rudder.

Outboard Rudder

An outboard rudder is mounted outside the hull on the boat’s stern, such as shown in this photo, rather than below the hull using a rudder post or hinges to the keel or skeg. Most outboard rudders are turned with a tiller rather than a steering wheel since there is no rudder post to which to gear a wheel.

Advantages of Outboard Rudder

An outboard rudder does not require a hole through the hull for a rudder post and thus is less likely to cause trouble if damaged. The rudder can often be removed or serviced while the boat is still in the water. Hinges at the top and bottom of the rudder section may provide more strength than a single rudder post.

Disadvantages of Outboard Rudder

Like a spade rudder, an outboard rudder is vulnerable to being struck by or caught in objects or rope in the water. Unlike a spade rudder it cannot be balanced in the water flow, so the force of water is always on one side of the pivot point, requiring more energy for turning the rudder.

A rudder is often related to keel shape .

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New Rudders

Replacement Sailboat Rudders and Centerboards

Four Types of Rudders On Sailboats

The four rudder types are: full rudder, spade rudder, skeg rudder, and outboard rudder. We will discuss the advantages and disadvantages of each.

Full Rudder

The full or full keel rudder is at the aft end of a full length keel. The keel-rudder runs along the entire length of the bottom of the boat’s hull. This full length rudder is safe and more resistant to damage. The leading edge of the keel protects the rudder from debris. The full rudder is a trademark of offshore cruisers like Cabo Ricos and Wetsails. Damage may be avoided even when grounding. The boat will rest safely on its side until the tide returns and lifts the boat off the shoal.

Spade Rudder

The spade rudder rests below the transom separate from the keel. A spade rudder turns easily because the water rushes both against its fore and aft edges – good when using a tiller. There’s less wet area so the spade rudder is fast. The spade, along with partial spade rudders are becoming popular in many sailboat designs.

Skeg Rudder

Compared to other styles, the skeg rudder is modern in safety and performance and popular on current production boats. The skeg rudder is similar to a spade keel and is fast. The skeg rudder’s fore edge is protected by a “faux keel” that extends from aft of the hull. Hylas yachts are known for their skeg rudders.

Outboard Rudder

Outboard rudders are used on smaller boats. They are attached to the transom of the boat, hanging off the stern. Racing prams employ outboard rudders. They are also easy to jerry rig as emergency rudders. Any long piece of metal and flat piece of wood, as in a cabin door, can work.

Each type of rudder has its advantages and disadvantages. Most importantly, inspect your rudder regularly and carry a spare.

Foss Foam products can create a replacement rudder for your sailboat. Contact us for more information.

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Choosing a Blue Water Yacht – Rudder Type

Posted Wednesday 15th July 2015

Over the last few weeks, Grabau International has taken you through a variety of subjects which encompass choosing the right yacht for blue water adventures. This guide is not written to dictate what to choose, or to supply a comprehensive encyclopedia of every option and variable, but simply a basic explanation of the main options and some guidance on what to look out for. Finding a yacht will always be a battle of your head over your heart, so the purpose of this guide is to give your head some questions to ask in the hope that an amicable compromise can be made with your heart. Part 4 of this guide looks at the question of rudders and steering .

Yachts use aft-mounted rudders to change direction and to counter the effects of weather-helm (where the yacht naturally tries to turn into wind when pressed to windward). Using either a wheel connected to the rudder stock via a linkage system or a tiller attached directly to the rudder post, the rudder can be turned creating a force of water striking one edge of the rudder blade to turn the stern in the opposite direction.

The type of rudder and fitted to a yacht is often directly related to the type of keel which was covered in part 3 of this guide , and the type of steering is usually dictated by the size and position of the cockpit and space directly beneath or aft of it.

As always, due to the huge variety of yachting pursuits, different rudder types work for different purposes. Those looking to go racing will almost certainly require a high aspect fully-balanced rudder whilst blue water sailors may wish to seek the additional strength and protection afforded by a fully or semi-skegged rudder blade.

Spade Rudder

Where the blade hangs down beneath the yacht and is self-supported by the stock. By moving the rudder stock aft from the leading edge, a spade rudder becomes a balanced rudder.

Balanced Rudder

The ‘balanced’ part comes in by virtue that the axis of rotation is behind the leading edge which means that when the rudder is turned, the pressure of water caused by the yacht’s movement through the water acts upon the forward part to counteract the force of resistance exerted by the larger aft section. The end result is a very light and reactive helm which is perfect for more performance-orientated yachts. Balanced rudder configurations are also usually married with fin keel profiles to further aid maneuverability and performance.

The downsides with spade and balanced spade rudders are the complete reliance upon the rudder stock to maintain structural integrity and the lack of protection to the leading edge of the blade from underwater impacts. Having seen a car drive into the rudder blade of a Volvo 70 (whilst ashore!) and the damage caused to the car whilst no apparent damage was caused to the rudder blade, a well-designed balanced rudder should offer few concerns for the cruising yachtsman.

Balanced rudder on a Frers-designed Nautor Swan

Skegged (semi or full) Rudder

A slightly more traditional and ‘belt & braces’ approach where the rudder is further supported, either at the bottom of the blade (fully-skegged) or midway down the blade (semi-skegged). This will usually be stronger and provide better resilience against impact. The moulded skeg can often help to guide any lobster pot or fishing lines downwards towards the bottom of the blade rather than jamming themselves against the stock. Most fully-skegged rudders are not balanced, so they may take a little more effort to steer, but it is possible with semi-skegged rudders to place the stock far enough aft to provide a balancing effect.

Semi skeg rudder on Malo 46

Full skeg rudder

Full keel rudder

Yachts with long-keels, such as Island Packet and most classics, have a rudder which is hinged to the aft edge of the keel, forming a continuous surface. The engine’s propeller is then usually positioned in an aperture at the aft end of the keel, but forward of the rudder blade. This configuration offers immense strength and protection, but the steering can be quite heavy as there is no balancing effect.

Full keel rudder on Tradewind 35

Outboard rudder

Mostly found on yachts beneath 30ft, outboard rudders are mounted outside of the hull on the yacht’s stern. Most outboard rudders are turned using a tiller rather than a wheel as there is no rudder post to connect the steering gear. Outboard rudders do not require a hole through the hull for a rudder post and are less likely to cause structural issues if damaged, but they are more exposed and therefore vulnerable and it is very difficult to balance them, so steering can be heavier than with a fully-balanced spade rudder.

Outboard (transom-hung) rudder on Hunter 707 sportsboat

Twin Rudders

Increasingly common on cruising as well as racing yachts as transom-profiles get broader. Twin rudders can be either spade or skeg-hung and can be reinforced to allow the yacht to take the ground when used with a lifting keel profile. Yachts fitted with twin rudders will lose the benefit of ‘prop wash’ to aid maoeuvering astern, but the practical benefits in terms of sailing to windward and (in some cases) drying out make them the only option in many cases.

Twin rudders on a modern Southerly lift keel yacht

Steering Systems

Wheel Steering

Now almost universal on all but the smallest of yachts. Large yachts (or those with broader transoms) will often have twin wheels which have their advantages -they do not encroach on cabin space beneath the cockpit sole, and also allowing clear & unobstructed passage from the cockpit the bathing platform. Wheel steering systems can be connected to the rudder stock through a variety of linkages including rod, cable, chain and even hydraulic steering systems.

Twin wheel steering on an Italia Yachts 15.98

Tiller Steering

Rarely found much above 28 feet unless for racing duties (where they can appear on yachts even as larger as TP52’s), but definitely appealing to those who like the K.I.S. (keep it simple) approach thanks to direct connection to the rudder stock. The downside is that generally the area either athwartships or aft of the tip of the tiller is a ‘no go zone’ to anyone other than the helmsman.

Tiller steering on an Italia Yachts 9.98

Rudder Stocks

These can be alloy, stainless steel or composite. Alloy is popular on high-end yachts as it is strong and light. Stainless is much heavier but perhaps less susceptible to pitting and swelling, but can suffer crevice corrosion. Composite can be found on mass-production yachts or custom high performance yachts. There is no ‘best option’, but be sure to inspect the stock very carefully before embarking on any serious ocean mileage.

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My Cruiser Life Magazine

All About the Rudder on a Sailboat

The rudder on a sailboat is one of those important parts that often gets overlooked. It’s hidden underwater most of the time and usually performs as expected when we ask something of it.

But when was the last time you seriously considered your sailboat rudder? Do you have a plan if it fails? Here’s a look at various designs of sail rudder, along with the basics of how it works and why it’s there.

How are sailboat rudders different than keels, how does the rudder work, wheel steering vs. tiller steering, full keel rudder sailboat, skeg-hung rudders, spade rudder, variations on designs, emergency outboard rudder options, looking to sail into the sunset grab the wheel, steer your sail boat rudder, and get out there, sail boat rudder faqs.

What Is a Boat Rudder?

The rudder is the underwater part of the boat that helps it turn and change direction. It’s mounted on the rear of the boat. When the wheel or tiller in the cockpit is turned, the rudder moves to one side or another. That, in turn, moves the boat’s bow left or right.

When it comes to sailing, rudders also offer a counterbalance to the underwater resistance caused by the keel. This enables the boat to sail in a straight line instead of just spinning around the keel.

Sailboat hull designs vary widely when you view them out of the water. But while the actual shape and sizes change, they all have two underwater features that enable them to sail–a rudder and a keel.

The rudder is mounted at the back of the boat and controls the boat’s heading or direction as indicated by the compass .

The keel is mounted around the center of the boat. Its job is to provide a counterbalance to the sails. In other words, as the wind presses on the sails, the weight of the ballast in the keel and the water pressure on the sides of the keel keeps the boat upright and stable.

When sailing, the keel makes a dynamic force as water moves over it. This force counters the leeway made by air pressure on the sails and enables the boat to sail windward instead of only blowing downwind like a leaf on the surface.

The rudder is a fundamental feature of all boats. Early sailing vessels used a simple steering oar to get the job done. Over the years, this morphed into the rudder we know today.

However, thinking about a rudder in terms of a steering oar is still useful in understanding its operation. All it is is an underwater panel that the helmsperson can control. You can maintain a course by trailing the oar behind the boat while sailing. You can also change the boat’s heading by moving it to one side or the other.

The rudders on modern sailboats are a little slicker than simple oars, of course. They are permanently mounted and designed for maximum effectiveness and efficiency.

But their operating principle is much the same. Rudders work by controlling the way water that flows over them. When they move to one side, the water’s flow rate increases on the side opposite the turn. This faster water makes less pressure and results in a lifting force. That pulls the stern in the direction opposite the turn, moving the bow into the turn.

Nearly all boats have a rudder that works exactly the same. From 1,000-foot-long oil tankers to tiny 8-foot sailing dinghies, a rudder is a rudder. The only boats that don’t need one are powered by oars or have an engine whose thrust serves the same purpose, as is the case with an outboard motor.

Operating the Rudder on a Sailboat

Rudders are operated in one of two ways–with a wheel or a tiller. The position where the rudder is operated is called the helm of a boat .

Ever wonder, “ What is the steering wheel called on a boat ?” Boat wheels come in all shapes and sizes, but they work a lot like the wheel in an automobile. Turn it one way, and the boat turns that way by turning the rudder.

A mechanically simpler method is the tiller. You’ll find tiller steering on small sailboats and dinghies. Some small outboard powerboats also have tiller steering. Instead of a wheel, the tiller is a long pole extending forward from the rudder shaft’s top. The helmsperson moves the tiller to the port or starboard, and the bow moves in the opposite direction. It sounds much more complicated on paper than it is in reality.

Even large sailboats will often be equipped with an emergency tiller. It can be attached quickly to the rudder shaft if any of the fancy linkages that make the wheel work should fail.

Various Sail Boat Rudder Designs

Now, let’s look at the various types of rudders you might see if you took a virtual walk around a boatyard. Since rudders are mostly underwater on the boat’s hull, it’s impossible to compare designs when boats are in the water.

Keep in mind that these rudders work the same way and achieve the same results. Designs may have their pluses and minuses, but from the point of view of the helmsperson, the differences are negligible. The overall controllability and stability of the boat are designed from many factors, and the type of rudder it has is only one of those.

You’ll notice that rudder design is closely tied to keel design. These two underwater features work together to give the boat the sailing characteristics the designer intended.

The classic, robust offshore sailboat is designed with a full keel that runs from stem to stern. With this sort of underwater profile, it only makes sense that the rudder would be attached to the trailing edge of that enormous keel. On inboard-powered sailboats, the propeller is usually mounted inside an opening called the aperture between the keel and rudder.

The advantages of this design are simplicity and robustness. The keel is integrated into the hull and protects the rudder’s entire length. Beyond reversing into an obstacle, anything the boat might strike would hit the keel first and would be highly unlikely to damage the rudder. Not only does the keel protect it, but it also provides a very strong connection point for it to be attached to.

Full keel boats are known for being slow, although there are modern derivatives of these designs that have no slow pokes. Their rudders are often large and effective. They may not be the most efficient design, but they are safe and full keels ride more comfortably offshore than fin-keeled boats.

Plenty of stout offshore designs sport full keel rudders. The Westsail 38s, Lord Nelsons, Cape Georges, Bristol/Falmouth Cutters, or Tayana 37s feature a full keel design.

A modified full keel, like one with a cutaway forefoot, also has a full keel-style rudder. These are more common on newer designs, like the Albergs, Bristols, Cape Dorys, Cabo Ricos, Island Packets, or the older Hallberg-Rassys.

A design progression was made from full keel boats to long-fin keelboats, and the rudder design changed with it. Designers used a skeg as the rudder became more isolated from the keel. The skeg is a fixed structure from which you can mount the rudder. This enables the rudder to look and function like a full keel rudder but is separated from the keel for better performance.

The skeg-hung rudder has a few of the same benefits as a full keel rudder. It is protected well and designed robustly. But, the cutaways in the keel provide a reduced wetted surface area and less drag underwater, resulting in improved sailing performance overall.

Larger boats featuring skeg-mounted rudders include the Valiant 40, Pacific Seacraft 34, 37, and 40, newer Hallberg-Rassys, Amels, or the Passport 40.

It’s worth noting that not all skegs protect the entire rudder. A partial skeg extends approximately half the rudder’s length, allowing designers to make a balanced rudder.

With higher-performance designs, keels have become smaller and thinner. Fin keel boats use more hydrodynamic forces instead of underwater area to counter the sail’s pressure. With the increased performance, skegs have gone the way of the dinosaurs. Nowadays, rudders are sleek, high aspect ratio spade designs that make very little drag. They can be combined with a number of different keel types, including fin, wing keels , swing keels, or bulb keels.

The common argument made against spade rudders is that they are connected to the boat by only the rudder shaft. As a result, an underwater collision can easily bend the shaft or render the rudder unusable. In addition, these rudders put a high load on the steering components, like the bearings, which are also more prone to failure than skeg or full keel designs. For these reasons, long-distance cruisers have traditionally chosen more robust designs for the best bluewater cruising sailboats .

But, on the other hand, spade rudders are very efficient. They turn the boat quickly and easily while contributing little to drag underwater.

Spade rudders are common now on any boat known for performance. All racing boats have a spade rudder, like most production boats used for club racing. Pick any modern fin keel boat from Beneteau, Jeanneau, Catalina, or Hunter, and you will find a spade rudder. Spade rudders are common on all modern cruising catamarans, from the Geminis to the Lagoons, Leopards, and Fountaine Pajots favored by cruisers and charter companies.

Here are two alternative designs you might see out on the water.

Transom-Hung or Outboard Rudders

An outboard rudder is hung off the boat’s transom and visible while the boat is in the water. Most often, this design is controlled by a tiller. They are common on small sailing dingies, where the rudder and tiller are removable for storage and transport. The rudder is mounted with a set of hardware called the pintle and gudgeon.

Most outboard rudders are found on small daysailers and dinghies. There are a few classic big-boat designs that feature a transom-hung rudder, however. For example, the Westsail 38, Alajuela, Bristol/Falmouth Cutters, Cape George 36, and some smaller Pacific Seacrafts (Dana, Flicka) have outboard rudders.

Twin Sailing Rudder Designs

A modern twist that is becoming more common on spade rudder boats is the twin sailboat rudder. Twin rudders feature two separate spade rudders mounted in a vee-shaped arrangement. So instead of having one rudder pointed down, each rudder is mounted at an angle.

Like many things that trickle down to cruising boats, the twin rudder came from high-performance racing boats. By mounting the rudders at an angle, they are more directly aligned in the water’s flow when the boat is healed over for sailing. Plus, two rudders provide some redundancy should one have a problem. The twin rudder design is favored by designers looking to make wide transom boats.

There are other, less obvious benefits of twin rudders as well. These designs are easier to control when maneuvering in reverse. They are also used on boats that can be “dried out” or left standing on their keel at low tide. These boats typically combine the twin rudders with a swing keel, like Southerly or Sirius Yachts do. Finally, twin rudders provide much better control on fast-sailing hulls when surfing downwind.

Unbalanced vs. Balanced Rudders

Rudders can be designed to be unbalanced or balanced. The difference is all in how they feel at the helm. The rudder on a bigger boat can experience a tremendous amount of force. That makes turning the wheel or tiller a big job and puts a lot of strain on the helmsperson and all of the steering components.

A balanced rudder is designed to minimize these effects and make turning easier. To accomplish this, the rudder post is mounted slightly aft of the rudder’s forward edge. As a result, when it turns, a portion of the leading edge of the rudder protrudes on the opposite side of the centerline. Water pressure on that side then helps move the rudder.

Balanced rudders are most common in spade or semi-skeg rudders.

Sail Rudder Failures

Obviously, the rudder is a pretty important part of a sailboat. Without it, the boat cannot counter the forces put into the sails and cannot steer in a straight line. It also cannot control its direction, even under power.

A rudder failure of any kind is a serious emergency at sea. Should the rudder be lost–post and all–there’s a real possibility of sinking. But assuming the leak can be stopped, coming up with a makeshift rudder is the only way you’ll be able to continue to a safe port.

Rudder preventative maintenance is some of the most important maintenance an owner can do. This includes basic things that can be done regularly, like checking for frayed wires or loose bolts in the steering linkage system. It also requires occasionally hauling the boat out of the water to inspect the rudder bearings and fiberglass structure.

Many serious offshore cruisers install systems that can work as an emergency rudder in extreme circumstances. For example, the Hydrovane wind vane system can be used as an emergency rudder. Many other wind vane systems have similar abilities. This is one reason why these systems are so popular with long-distance cruisers.

There are also many ways to jury rig a rudder. Sea stories abound with makeshift rudders from cabinet doors or chopped-up sails. Sail Magazine featured a few great ideas for rigging emergency rudders .

Understanding your sail rudder and its limitations is important in planning for serious cruising. Every experienced sailor will tell you the trick to having a good passage is anticipating problems you might have before you have them. That way, you can be prepared, take preventative measures, and hopefully never deal with those issues on the water.

What is the rudder on a sailboat?

The rudder is an underwater component that both helps the sailboat steer in a straight line when sailing and turn left or right when needed.

What is the difference between a rudder and a keel?

The rudder and the keel are parts of a sailboat mounted underwater on the hull. The rudder is used to turn the boat left or right, while the keel is fixed in place and counters the effects of the wind on the sails.

What is a rudder used for on a boat?

The rudder is the part of the boat that turns it left or right

Matt has been boating around Florida for over 25 years in everything from small powerboats to large cruising catamarans. He currently lives aboard a 38-foot Cabo Rico sailboat with his wife Lucy and adventure dog Chelsea. Together, they cruise between winters in The Bahamas and summers in the Chesapeake Bay.

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Different Types of Rudders: A Comprehensive Look at Ship Steering

October 10, 2023

The rudder is crucial in determining how a ship will move amid the vastness of the sea. The standard rudder, a seemingly simple piece of gear, is available in a variety of forms and designs, each one suitable for specific vessels and navigational requirements. In this write-up, we delve into the world of ship rudders, learning about their significance, their purposes, and the various types that keep maritime boats on course. Every shipowner or someone planning to invest in a ship must gather as much information as possible on all aspects of a ship, so aside from reading this article, it is also important to hire a ship broker company in Norway for a successful purchase .

Let’s get started.

The Role of Rudders

Let’s take a moment to understand the basics of ship steering before delving into the many types of rudders. One of the main elements of a ship’s steering system is the rudder. Its primary function is to guide the direction the ship goes through the water, and it is normally found towards the stern (rear) of the boat.

Rudders function by changing the direction of the water’s flow as the ship travels. The water’s flow is diverted by angling the rudder to the left or right, producing a lateral force that rotates the ship in the desired direction. The mobility and handling characteristics of a ship are greatly influenced by the size, shape, and design of the rudder.

For more information, take a look at the below section, or contact a top shipbroker company in Norway .

Different Types of Rudders on Ships

Now, take a look at the various types of rudders used on ships.

1. Spade Rudder

Modern ships frequently use the spade rudder style of rudder. It is immediately linked to the vessel’s hull and distinguished by the look of a blade. Spade rudders are perfect for a variety of ship types, including sailboats, yachts, and smaller vessels. They provide outstanding maneuverability and responsiveness.

2. Skeg- Mounted Rudder

Skeg-hung or mounted rudders are supported in part by the ship’s skeg, which is a vertical extension of the hull. The rudder is given more stability by this design, which makes underwater obstructions less likely to hurt it. Sailing yachts and some motorboats frequently employ skeg-hung rudders.

3. Balanced Rudder

The effort needed to control a ship is lessened by balanced rudders. They have a pivot point on the rudder stock-forward portion of the rudder blade. With this design, the water pressure on the aft portion of the blade is reduced, making it simpler to turn the rudder. Larger vessels frequently have balanced rudders because of their effectiveness and precise control.

4. Full Spade Rudder

As the name suggests, full spade rudders have a rudder blade that spans the entire length of the vessel’s hull. The efficiency and control of the rudder are maximized by this design. Larger ships, such as commercial cargo ships and cruise ships, where precise agility is crucial, frequently have full spade rudders.

5. Semi Balanced Rudder

The balanced and unbalanced rudders both had their share of issues when the steering gear system failed, which led to the development of the semi-balanced rudder. The ship’s rudders, both balanced and unbalanced, would remain stationary as it turned. A semi-balanced rudder has a balanced chord length overall, but the upper portion of the chord length is unbalanced. This is so that the balanced half will allow the least amount of torque to move the rudder, and the unbalanced part will extend the proper structural support. Thus, when the steering gear system malfunctions during a course change, the semi-balanced rudder automatically returns to the centerline. These days, this kind of rudder is typically found on ships.

6. Twin Rudders

Some ships have two rudders that are placed side by side. Twin rudders offer improved control and stability, particularly during choppy seas. They enable better handling and less drag and are frequently utilized in contemporary sailing boats and certain motor vessels.

7. Spade Rudder With Bulb

A specific kind of rudder used on ships and boats is a spade rudder with a bulb. The rudder blade’s bottom has a bulb or extension in this configuration. The bulb’s function is to improve the stability and performance of the rudder. It boosts the rudder’s effectiveness by increasing mass and surface area to the lower part of the blade, especially in rough sea conditions. Spade rudders with bulbs are a good choice for larger sailboats and racing yachts because they enhance stability and control.

8. Flap Rudder

The trailing edge of the rudder blade has an extra flap in flap rudder designs. The ship’s steering qualities can be fine-tuned by adjusting this flap. In bigger vessels, where precise control and effectiveness are crucial, flap rudders are frequently used.

In conclusion, ship steering is an essential component of marine engineering, and the choice of the rudder has a big impact on how manoeuvrable and controlled a ship is. Each kind of rudder—from twin to spade—serves a particular function and meets the varying demands of different kinds of vessels. If you are planning to purchase a ship, then knowing about the different rudders would help you make a successful purchase. And, for detailed information, it would be best if you consult expert ship brokers. If you are based out of Norway, you can get in touch with any top ship broker companies in Norway .

What is a Boat Rudder? – Types & Important Facts to Know

A boat rudder is a flat or curved piece of material, usually made of metal, wood, or composite materials, attached to the stern (rear) of a boat or ship to control its direction of movement.

Table of Contents

The rudder can be turned left or right using a steering mechanism, such as a tiller or a wheel, and its movement redirects the flow of water passing over the boat’s hull, causing the boat to turn in the desired direction.

The size and shape of a rudder can vary depending on the size and type of boat or ship it is installed on, as well as the intended use of the vessel.

Smaller boats may have a single, smaller rudder, while larger vessels may have multiple rudders or a more extensive, more complex rudder system.

Additionally, some boats, such as sailboats, may have a retractable or removable rudder to minimize drag when sailing.

Boat Rudder – Definition and History

The history of the boat rudder dates back to ancient times when boats were first developed for transportation and trade.

The earliest rudders were simple oars or paddles that were used to steer the boat by dragging them through the water. Later, larger boats and ships required a more efficient method of steering, and the rudder was developed.

The first known depiction of a rudder comes from a Han dynasty tomb model in China, dated to the 1st century AD.

This early rudder was made of wood and was attached to the hull by a yoke, which allowed the rudder to pivot from side to side.

Over time, the design of the rudder evolved, with improvements in materials and technology leading to more efficient and effective steering systems.

In the Middle Ages, European ships began using a sternpost rudder, which was mounted on the sternpost and allowed for more precise steering control.

By the 19th century, iron and steel were being used to make rudders, which were stronger and more durable than their wooden predecessors.

Today, boats and ships of all sizes use a variety of rudder designs and materials, ranging from small fiberglass rudders on recreational sailboats to massive steel rudders on ocean-going cargo ships.

The basic principles of the rudder remain the same, however, providing boats and ships with the ability to navigate and maneuver through the water.

How Rudders Work Types Of Rudders And Their Advantages

Rudders work by redirecting the flow of water passing over a boat’s hull, creating a force that turns the boat in the desired direction.

When the rudder is turned, it creates a pressure differential on either side of the rudder, which causes the water to flow around the rudder and deflects the water in the opposite direction, thus changing the direction of the boat.

There are several types of rudders used on boats and ships, each with its advantages and disadvantages:

1-Balanced Rudder

A balanced rudder is a type of rudder used on boats and ships that are designed to reduce the force required to turn the rudder and improve steering efficiency.

A balanced rudder has a smaller surface area, which reduces the amount of water resistance and drag created by the rudder, making it easier to turn.

The balance of the rudder is achieved by using a counterweight or a smaller rudder at the front of the main rudder. The counterweight or front rudder offsets the force created by the pressure differential on the main rudder, making it easier to turn.

Balanced rudders are commonly used on sailing vessels, where precise steering control is important. They can also be found on powerboats and larger ships, where they provide improved maneuverability and reduced drag.

One of the main advantages of a balanced rudder is that it requires less force to turn than a conventional rudder, which reduces the amount of energy required to steer the vessel. This can result in improved fuel efficiency and reduced operating costs.

Additionally, the smaller size of the rudder can make it less effective in high winds or rough seas.

2-Unbalanced Rudder

An unbalanced rudder is a type of rudder used on boats and ships that do not have a counterweight or a smaller rudder to offset the force created by the pressure differential on the rudder.

Unbalanced rudders are simpler in design and less expensive to manufacture than balanced rudders, but require more force to turn and are less efficient.

Unbalanced rudders have a larger surface area than balanced rudders, which creates more water resistance and drag when turning. This can make the boat more difficult to steer and can reduce the overall speed and efficiency of the vessel.

Unbalanced rudders are commonly used on smaller boats and recreational vessels, where the reduced manufacturing costs and simplicity of design are important factors.

However, larger vessels such as commercial ships and military vessels typically use balanced rudders or other more advanced steering systems to provide greater maneuverability and control.

Overall, unbalanced rudders have the advantage of being less complex and less expensive than other types of rudders, but their larger size and greater resistance can make them less efficient and more difficult to control.

Proper maintenance and care of the rudder are important to ensure it operates effectively and safely.

3-Semi-Balanced Rudder

A semi-balanced rudder is a type of rudder used on boats and ships that combines features of both balanced and unbalanced rudders.

Semi-balanced rudders have a smaller surface area than unbalanced rudders, which reduces the amount of water resistance and drag created by the rudder, making it easier to turn.

However, unlike unbalanced rudders, semi-balanced rudders have a small counterweight or a smaller rudder at the front to partially offset the force created by the pressure differential on the main rudder.

Semi-balanced rudders are commonly used on smaller to medium-sized boats and ships, where maneuverability and ease of use are important factors, but the cost is also a concern.

The smaller size of the rudder allows for improved efficiency and reduced drag, while the partial balance provided by the counterweight or smaller rudder at the front makes it easier to turn than an unbalanced rudder.

Semi-balanced rudders can provide a good balance between efficiency and ease of use, but they may not be as effective in extreme conditions as fully-balanced rudders. They also require proper maintenance and care to ensure that they operate effectively and safely.

4-Skeg-Mounted Rudder

A skeg-mounted rudder is a type of rudder used on boats and ships that are attached to a vertical structure, called a skeg, which extends from the bottom of the boat’s hull. The skeg provides support and stability for the rudder and helps to protect it from damage.

Skeg-mounted rudders are commonly used on larger boats and ships, such as commercial vessels and yachts. They are typically mounted near the stern of the boat, and the skeg extends downward from the hull to provide additional support for the rudder.

This design allows for greater maneuverability and control, particularly in rough or choppy waters.

One of the main advantages of a skeg-mounted rudder is its ability to provide a stable and secure attachment for the rudder, which can reduce the risk of damage or failure. Additionally, the skeg can help to protect the propeller and other underwater components from damage.

However, the additional structure required for a skeg-mounted rudder can increase the weight and complexity of the boat, which can affect performance and efficiency.

Skeg-mounted rudders can also be more difficult to repair or replace than other types of rudders, particularly if damage occurs to the skeg itself.

5-Transom or Outboard Rudder

A transom or outboard rudder is a type of rudder used on boats where the rudder is mounted on the transom or the exterior of the hull, rather than being attached to a skeg or other support structure.

Transom or outboard rudders are commonly used on small boats, such as sailboats and motorboats, and are particularly common on boats with outboard motors.

The main advantage of a transom or outboard rudder is that it is relatively simple and inexpensive to install and maintain. This type of rudder can also provide good maneuverability and responsiveness, particularly at lower speeds.

However, transom or outboard rudders can be less effective at higher speeds, as they can create more drag and turbulence.

They may also be more susceptible to damage from impact with objects in the water and may require more frequent maintenance and replacement than other types of rudders.

6-Flaps Rudder

Boats also have flaps and rudders, but they work slightly differently from those on aircraft.

Boat flaps, also known as trim tabs, are small hinged surfaces attached to the stern of a boat that can be adjusted up or down to change the angle of the boat’s hull in the water.

By changing the angle of the hull, the boat can be made to ride higher or lower in the water, which can improve stability, reduce drag, and improve fuel efficiency. Boat flaps are typically used to adjust the boat’s trim while underway, especially in rough water or when carrying a heavy load.

The rudder on a boat is a hinged surface attached to the stern that can be turned left or right to steer the boat.

Unlike aircraft rudders, boat rudders are not used to control yaw or side-to-side movement, but rather to turn the boat left or right. The size and shape of the rudder affect the boat’s turning ability, and some boats have more than one rudder to improve maneuverability.

In summary, boat flaps and rudders are used to adjust the boat’s trim and steer the boat, respectively, and work differently from their counterparts on aircraft.

7-Spade Rudder

A spade rudder is a type of boat rudder that is designed with a single blade that is attached to the hull of the boat. The term “spade” refers to the shape of the rudder, which is narrow and tapered like a spade or shovel.

Compared to other types of rudders, such as skeg-mounted or transom-mounted rudders, a spade rudder offers several advantages.

Because it is mounted on the hull rather than the keel or transom, a spade rudder can be positioned farther aft and closer to the propeller, which can improve the boat’s maneuverability and reduce the turning radius.

Additionally, a spade rudder is typically lighter and more responsive than other types of rudders, which can make it easier to control the boat in a variety of conditions.

However, there are also some potential drawbacks to spade rudders. Because they are mounted directly to the hull, they can be vulnerable to damage from impacts or groundings.

Additionally, they may require more maintenance than other types of rudders due to their complex design and construction.

8-Twin Rudders

Boats with twin rudders have two separate rudders mounted on the stern of the boat, usually one on each side of the keel. This arrangement offers several advantages over a single rudder configuration.

One of the primary benefits of twin rudders is improved maneuverability. Because each rudder can be angled independently, the boat can be steered more precisely and with greater responsiveness, making it easier to navigate in tight spaces or rough water.

Additionally, twin rudders can provide greater stability and control when the boat is heeled over or sailing at high speeds.

Another advantage of twin rudders is redundancy. If one rudder becomes damaged or fails, the boat can still be steered using the other rudder, which can be a critical safety feature in emergencies.

However, there are also some potential drawbacks to twin rudder configurations. They can be more complex and expensive to design and install than a single rudder and may require additional maintenance to keep both rudders operating smoothly.

Additionally, twin rudders can create more drag than a single rudder, which can reduce the boat’s speed and fuel efficiency.

However, they may not be necessary or practical for all types of boats and applications.

How Does a Rudder Work?

A rudder is a hinged surface located at the stern (rear) of a boat that is used to control the direction of the boat. When the rudder is turned to one side, the force of the water flowing past it creates a turning moment that causes the boat to turn in the opposite direction.

The principle behind how a rudder works are based on the Bernoulli principle, which states that as the speed of a fluid (such as water) increases, its pressure decreases.

When the boat is moving forward, water flows past the rudder at a higher speed on one side than the other.

This creates a pressure differential, with higher pressure on the side where the water is flowing more slowly and lower pressure on the side where the water is flowing more quickly. The resulting force on the rudder creates a turning moment that causes the boat to turn.

To turn the boat to the left, the rudder is turned to the right, creating a higher pressure on the right side of the rudder and a lower pressure on the left side, which turns the boat to the left.

Conversely, turning the rudder to the left creates a higher pressure on the left side of the rudder and a lower pressure on the right side, which turns the boat to the right.

The size and shape of the rudder, as well as the speed and direction of the water flow, all affect the turning ability and responsiveness of the boat.

Additionally, other factors such as wind, currents, and the boat’s weight and balance can also influence how a rudder works and how effectively it can steer the boat.

The advantages of rudders include improved steering and maneuverability, greater control over the direction and speed of the boat, and increased safety and stability.

However, rudders can also create drag and resistance, which can reduce the boat’s speed and efficiency, particularly in light winds or calm waters. Proper maintenance and care of the rudder are important to ensure it operates effectively and safely.

Hi, My name is Steve. Boating is my hobby :). Bought and sold many bots during the last 15 years. You can find the most current and old boat sales here. I am working hard to find the best gift ideas, to analyze the latest gadgets and accessories, and to provide reviews and recommendations to improve your boating experience. I hope you enjoy my site.

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Readers' Questions

How to calculate rudder area for a performance cruising catamaran?

Calculating the rudder area for a performance cruising catamaran involves considering factors such as the boat's length, displacement, and desired maneuverability. Here is a general approach to calculating rudder area: Determine the displacement of the catamaran: Displacement refers to the weight of the boat when it is fully loaded. Measure or obtain the displacement of the catamaran in pounds or kilograms. Calculate the wetted surface area: Wetted surface area refers to the surface area of the hulls that are in contact with water. Use the catamaran's length, beam, and draft to estimate the wetted surface area. This can be done using empirical formulas specific to catamarans or by using more precise methods, such as integrating the hull shape's cross-sections. Determine the Lateral Plane Area Coefficient (LPAC): LPAC is a coefficient used to determine the rudder area based on the wetted surface area. It depends on the desired maneuverability and varies for different types of vessels. For performance cruising catamarans, a typical LPAC value ranges from 0.03 to 0.05. Calculate the rudder area: Multiply the wetted surface area by the LPAC to obtain the rudder area. The formula is as follows: Rudder Area = Wetted Surface Area x LPAC For example, if the wetted surface area of a catamaran is 500 square feet, and the LPAC is 0.04: Rudder Area = 500 x 0.04 = 20 square feet. Remember that this is a general approach, and it is always recommended to consult with naval architects or boat designers who have expertise in catamarans for more precise calculations specific to your vessel.

Do rudders mounted underneath the bridgedeck of a wharram catamaran work?

Yes, they do work. Rudders mounted underneath a catamaran's bridgedeck can provide the same directional control as rudders mounted at the stern of a single-hulled vessel. This is especially true for sailing catamarans, which are designed with a long bridgedeck that extends forward of the transoms to create a wide platform for steering and control. Because this bridgedeck extends far enough out of the water, it can accommodate a rudder and provide the same steering capabilities as a traditional rudder.

How to tune catamaran rudders?

First, check your boat's steering system and adjust the rudder angle as needed. Check the tension on the steering cables and make sure they are properly adjusted. Make sure the rudders are properly aligned with the waterline. Trim the sails to the optimal angle for the prevailing conditions. Place the rudders at the correct angle to the waterline. Test the steering at slow and fast speeds. If necessary, make adjustments to the rudder angle to ensure maximum response. Test the steering at different angles of heel to determine if the helm is balanced. Make sure the rudders are kept in good condition and regularly maintained.

How to build mini keels for a catamaran?

Building mini keels for a catamaran requires precise measurements, proper materials, and some woodworking skills. Here's a step-by-step guide on how to build mini keels for a catamaran: Gather the materials: You will need marine-grade plywood, epoxy resin, fiberglass cloth, sandpaper, and marine paint. Measure and design: Decide the size and shape of the mini keels based on your catamaran's specifications. Measure the keel's length, width, and thickness. Sketch the design on paper. Cut the plywood: Using a jigsaw or a hand saw, cut the marine-grade plywood according to the dimensions outlined in your design. Make sure to cut two identical shapes for each keel. Shape the keel: Using sandpaper, smooth the edges and shape the plywood according to your design. Take your time to achieve the desired keel shape. Apply epoxy resin: Coat both sides of each keel with epoxy resin to seal the plywood. Follow the epoxy resin manufacturer's instructions for mixing and applying the resin. Allow it to cure completely. Apply fiberglass cloth: Cut fiberglass cloth slightly larger than the keel's dimensions. Apply epoxy resin to the keel's surface and lay the fiberglass cloth over it. Smooth out any air bubbles or wrinkles using a squeegee or putty knife. Apply more epoxy resin on top of the fiberglass to fully saturate it. Allow it to cure. Sand and paint: Once cured, sand the keel to remove any rough spots or imperfections. Make sure the surface is smooth and ready for painting. Apply marine paint to the keel, using several coats to ensure durability. Install the keels: Consult your catamaran's design or consult with a boat builder to determine the optimal placement for the mini keels. Install the keels onto the catamaran's hulls using marine-grade screws or bolts. Make sure they are securely fastened. Final touch-ups: Give a final sanding to the keels after they are installed to ensure a smooth finish. Apply additional coats of marine paint if necessary. Remember to take safety precautions, such as wearing gloves and protective eyewear, when working with epoxy resin and power tools. Additionally, consulting a boat builder or experienced sailor for advice and guidance is recommended to ensure the mini keels are correctly designed and installed for optimal performance and stability.

How weel do twin rudders track?

Twin rudders usually track very well, as the two rudders create an increased force and rudder area compared to a single rudder. This allows for more precise control and little to no lateral drift.

Do catamarans have keels?

No, catamarans do not have keels.

Can rudder propeller be used for catamaran boats?

Yes, rudder propellers can be used for catamaran boats. They are commonly used as a propulsion system to provide thrust and maneuverability. Rudder propellers are typically designed with two propeller blades mounted on a common shaft. The two blades can be adjusted independently, allowing the boat to move forward and backward, as well as turn.

How to makea catamaran rudder?

To make a catamaran rudder, you will need the following materials and tools: Materials: - Marine-grade plywood or fiberglass sheet - Stainless steel or aluminum for the rudder stock - Nuts, bolts, and washers - Epoxy resin and hardener - Fiberglass cloth - Sandpaper - Marine-grade paint or varnish Tools: - Jigsaw or handsaw - Drill - Router or file - Screwdriver - Paintbrush - Sanding block or power sander Here are the general steps to make a catamaran rudder: Design the rudder: Determine the size and shape of the rudder. Make sure it is suitable for the specific catamaran design and sailing conditions. Create a template: Trace the outline of the rudder on a piece of cardboard or plywood to create a template. Cut it out and refine the shape until you are satisfied with the design. Transfer the template to the rudder material: Place the template on the marine-grade plywood or fiberglass sheet. Use a pencil or marker to trace the outline onto the material. Cut out the rudder shape: Use a jigsaw or handsaw to carefully cut along the traced outline. Take your time and ensure smooth, even cuts. Sanding and shaping: Use sandpaper or a power sander to smooth the edges and shape the rudder. Round the leading and trailing edges for better hydrodynamics. Take your time and regularly check the symmetry and balance of the rudder. Prepare the rudder stock: Cut and shape the stainless steel or aluminum for the rudder stock. Drill holes in the stock for attaching to the rudder and boat. Attach the rudder stock: Use epoxy resin to bond the rudder stock to the rudder. Reinforce with fiberglass cloth and more epoxy for added strength. Finishing touches: Sand the entire rudder surface to create a smooth finish. Apply multiple coats of marine-grade paint or varnish for protection against water and UV rays. Allow each coat to dry completely before applying the next. Install the rudder: Attach the rudder to the catamaran using appropriate nuts, bolts, and washers. Ensure it is securely fastened and aligned properly for optimal performance. Remember to consult any specific plans or guidelines provided by your boat's manufacturer or a professional boat builder.

Do catamarans have rudders?

Yes, catamarans typically have two rudders located at the back of the hulls.

Do catamarans need rudder?

Yes, catamarans need rudders for navigational control. The rudder is connected to a steering system which helps to control the direction of the vessel.

Do a catamaran need one or two rudders?

A catamaran typically has two rudders.

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Different Types of Rudders Used For Ships

As humanity continues to explore the vast oceans, the need for efficient and precise ship maneuvering becomes increasingly vital. One of the key components responsible for controlling the direction and stability of a ship is the rudder. A rudder is a primary steering device that enables ships to change their course and maintain stability amidst changing maritime conditions. In this article, we will delve into the world of ship rudders, exploring their types, functions, and the latest advancements in this essential maritime technology.

The Basics of Ship Rudders

Before diving into the various types of ship rudders, let’s understand their fundamental purpose. A rudder is typically located at the stern (rear) of a ship and is attached to the vessel’s hull through hinges or pintles. Its primary function is to control the ship’s yaw motion, allowing it to change direction while maintaining stability and maneuverability.

Balanced Rudders

Balanced rudders are commonly used in modern ship designs due to their effectiveness in enhancing maneuverability and reducing steering forces. These rudders feature an additional surface area ahead of the rudder stock, known as the balance or skeg. The balance helps to minimize the forces acting on the rudder, allowing for smoother steering.

The balanced rudder design comes in two variations: semi-balanced and fully balanced rudders. Semi-balanced rudders have a smaller balance area, resulting in a trade-off between maneuverability and reduced steering forces. Fully balanced rudders, on the other hand, offer excellent maneuverability and reduced steering forces but may require more complex control systems.

Spade Rudders

Spade rudders, also known as unbalanced rudders, are another popular type widely employed in the maritime industry. As the name suggests, these rudders resemble a spade or a flat plate and are attached directly to the hull without any additional balance area. Spade rudders are known for their simplicity and easy installation, making them a cost-effective choice for many ship designs.

Although spade rudders are generally efficient, they can generate high steering forces, particularly at high speeds or in adverse weather conditions. To mitigate these challenges, ship designers often incorporate additional stabilization systems or implement advanced materials and hydrodynamic profiles.

Conventional Rudders

Conventional rudders are the traditional and most widely recognized type of rudder design. They consist of a single plate attached to the ship’s stern and are hinged to allow for controlled movement. While conventional rudders offer simplicity and reliability, they are generally less efficient than more modern designs, especially at higher speeds.

To enhance the maneuverability of conventional rudders, some ships incorporate specialized profiles, such as bulbous or streamline shapes, to improve hydrodynamic performance and reduce drag. Additionally, auxiliary rudders, also known as twin rudders, can be installed alongside conventional rudders to provide increased maneuverability and redundancy.

Flap Rudders

Flap rudders represent an innovative design that combines the characteristics of both balanced and unbalanced rudders. These rudders feature a separate flap mounted aft of the main rudder, which can be controlled independently. The flap can be adjusted to different angles, providing additional steering control and improving maneuverability.

The flexibility of flap rudders allows for improved efficiency, as they can be adjusted to optimize hydrodynamic performance based on specific operating conditions. This adjustability is particularly beneficial in challenging situations, such as when maneuvering in narrow channels, adverse weather, or strong currents.

Retractable Rudders

In some specialized ship designs, retractable rudders are employed to optimize performance and reduce hydrodynamic drag. These rudders can be partially or fully retracted into the hull, reducing the ship’s resistance when higher speeds are desired. Retractable rudders are commonly found in vessels that require both high maneuverability in restricted areas and enhanced speed in open waters, such as luxury yachts or military ships.

The retractable mechanism allows ships to transition smoothly between different operational modes, providing optimal performance for various maritime environments. However, the additional complexity of retractable rudders increases the maintenance requirements and overall cost of the vessel.

Ship rudders are vital components in the maritime world, allowing vessels to navigate through vast oceans with precision, stability, and control. From balanced and unbalanced designs to conventional, flap, and retractable variations, each rudder type brings its own set of advantages and considerations. As technology continues to advance, ship designers are constantly seeking innovative solutions to enhance maneuverability, reduce steering forces, and improve hydrodynamic performance.

Whether it’s a massive cargo ship, a sleek luxury yacht, or a powerful naval vessel, the choice of rudder design plays a crucial role in ensuring safe and efficient maritime operations. By understanding the various types of rudders available, naval architects, shipbuilders, and seafarers can make informed decisions to optimize ship performance, adapt to changing conditions, and navigate the seas with confidence.

As we sail into the future, the evolution of ship rudder technology will undoubtedly continue, presenting new possibilities and advancements that will shape the way we explore and harness the power of the world’s oceans.

Related FAQs

What is the primary purpose of a ship's rudder.

The primary purpose of a ship’s rudder is to control the direction and stability of the vessel. It helps in changing the ship’s course by deflecting the flow of water passing over it, allowing the ship to navigate through the water effectively.

What are the different types of rudders used for ships?

There are several types of rudders used for ships, including balanced rudders, spade rudders, conventional rudders, flap rudders, and retractable rudders. Each type offers unique characteristics and advantages, catering to specific ship designs and operational requirements.

How does a balanced rudder differ from an unbalanced rudder?

A balanced rudder features an additional surface area, known as the balance or skeg, ahead of the rudder stock. This balance helps reduce the steering forces and provides smoother steering. On the other hand, an unbalanced rudder, also called a spade rudder, lacks the additional surface area and is directly attached to the ship’s hull.

What are the benefits of using a flap rudder?

Flap rudders offer improved maneuverability and control. They have a separate flap mounted aft of the main rudder, which can be adjusted independently. This adjustability allows for optimized hydrodynamic performance, particularly in challenging situations such as strong currents or narrow channels.

When are retractable rudders used in ship designs?

Retractable rudders are commonly used in ships that require both high maneuverability in restricted areas and enhanced speed in open waters. These rudders can be partially or fully retracted into the hull, reducing hydrodynamic drag and improving the ship’s speed. They are often found in luxury yachts and military vessels.

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Sailboat rudder types – full, spade, skeg, outboard.

The four rudder types are: full, spade, skeg, and outboard. This article discusses the advantages and disadvantages of each.

Full The full or full keel rudder lies at the aft end of a full length keel. The keel-rudder streches along the entire length of the bottom of the hull. The full rudder is safe and nearly invulnerable to damage. The leading edge of the keel protects the rudder from flotsam. The full rudder is quintessential of offshore cruisers like Wetsails and Cabo Ricos. Even grounding may not cause damage. The boat will sit comfortable on its side until the tide returns and floats the boat back up.

Spade The spade rudder lies at the aft separate from the keel. A spade rudder is easy to turn because the water rushes both against its fore and aft edges – great for using a tiller. A spade rudder is also fast as the wet area less than a full keel. The boat racing along with less resistance. Spade and partial spades are becoming the most popular rudder type. The Hylas 70 has a partial spade rudder as well as early 54’s.

Skeg A skeg rudder is more modern in performance and safety. It is the most popular and common type of rudder on production boats these days. The rudder is fast and looks like a spade keel. Except, the skeg rudder has a fake keel which extends from the hulls aft and protects the fore edge. Most Hylas yachts have skeg rudders.

Outboard Outboard rudders are seen on smaller boats. They simply hang over the stern of the boat. For example, racing prams use outboard rudders. They are easy to fasion as emergency rudders. You can make one out of a handlerail and cabin door.

Conclusion A rudder is either full, spade, skeg, or outboard. Each type has its benefits. The most important part is make sure she is in good condition and have a spare.

4 Replies to “Sailboat Rudder Types – Full, Spade, Skeg, Outboard”

Ahoy Mateys, it’s Fox Axel the Pirate. I’ve got a swashbuckling yarn to tell ye. Me was drifting along way out at sea. Me had lost me steering while pillaging a friendly ship. The knaves canon knocked me rudder off. Me had nought to to turn to. The authorities would hang me, the villainous lot. But, me was getting desperate out of grub and rum, nothing to sage me drunken pirate ways. I had lost me last vestige of sanity.

Finally, me saw in the distance a giant whaler coming. The big ship sailed straight at me. “Ahoy mateys!” me spake. The freighter came near, too near. Shiver me timbers. The goulish crew must be drunk out of thee minds. Me could not steer away. She rammed straight slicing me ship in twain. Down to Davy Jones’ locker we went. Take care with ye rudders mateys – the Pirate of Monkey Isle.

Ok ye swabs ave a told me to finish me story. Ere dis da rest. As the freighter tore away leaving me to perish in the sea. I climbed on a board of driftwood from me sinkin’ ship. I passed out adrift, alone. When I came to, I found meself shipwrecked on a deserted island. I stumbled around and ran into, who of all? Big Red, me pirate enemy! Aye, I’m shipping as mate with his goulish fleet until I can betray and kill him. Aye, hope Big Red ain’t reading dis here blog. Black Fox the Pirate.

I am ye swab. I am too sharp for some ere fool like ye. I ain’t gots no book learning, but me hast carniving ways from many years below the mast. Iffen ye be trying to betray me, I am a gonna get ye.

Thank you for sharing this article.It’s quite easy to understand the difference.

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Professional BoatBuilder Magazine

The rudimentaries of rudders.

By Steve D'Antonio , Jul 12, 2018

Even stoutly constructed rudders are vulnerable to deterioration over time, especially when mild steel or high-carbon-stainless steel is buried in composite foil sections, which inevitably become saturated with seawater.

Like other systems and gear aboard cruising and commercial vessels, rudders have terms to identify their parts and functions. When measuring a rudder, the span and chord are the vertical height and fore-and-aft width, respectively, while the top of portion closest to the hull is referred to as the root , and the bottom is called the tip . Another term frequently used when discussing rudder design, particularly for sailing vessels, is aspect ratio —simply the square of the rudder’s span divided by the rudder’s area. As a rule of thumb, longer, narrower rudders are more efficient than short, wide rudders, and the aspect ratio describes precisely this relationship. Thus, rudders on high-performance sailing vessels are said to have a high-aspect ratio. Walking around a boatyard one day and measuring a few cruising sailboat rudders, I came up with aspect ratios of between 1.7 and 2.1, while one high-performance sailing vessel’s rudder came in at 3.5. The 20-knot semi-displacement lobster yacht’s rudder I measured yielded an even 2.0 aspect ratio, which is considered respectable for this application.

More identifiable rudder components include the stock ; web or armature ; rudderport or log ; stuffing box or compression tube ; bearing ; gudgeon ; and pintle . Not every rudder has all these components.

Rudderstocks

The rudderstock is essentially a shaft or tube that protrudes from the top and sometimes the bottom, depending upon type, of many rudder designs. Because this component provides the primary connection between the rudder’s blade (the flat section that imparts the steering force) and the vessel’s steering system, its design, construction, and material are consequential.

Most stocks are made of stainless steel, bronze, or aluminum, while some are carbon fiber, and they may be solid or hollow. Stainless steel is by far the most common, but it has a penchant for crevice corrosion when exposed to oxygen-depleted water. Insidiously, corrosion nearly always occurs in places where it cannot easily be seen—such as inside many composite (fiberglass and core material) rudder blades and beneath flax-type stuffing-box packing (the problem is exacerbated when the vessel is used infrequently).

This all-stainless rudderstock and webbing is well crafted and ready to be covered with its composite shell.

Of the stainless steel alloys, some resist this corrosion better than others. Stainless-steel rudderstocks should be manufactured with strong, highly corrosion-resistant proprietary shafting alloys such as A22. The next best choice is 316L stainless steel, which also resists crevice corrosion well. Critically important is the L suffix, meaning “low carbon,” a requirement if it is to be welded, as nearly every rudderstock must be, to the support within composite rudders, or to all-metallic plate-steel rudders. Failure to source low-carbon stainless steel for the stock or the web leads to weld decay, sometimes referred to as carbide precipitation, where the region around the weld loses its resistance to corrosion and rusts when exposed to water.

Aluminum rudderstocks are nearly always tubular. Common on aluminum vessels to reduce the likelihood of galvanic corrosion, aluminum stocks are also relatively common on fiber reinforced plastic (FRP) vessels, particularly large ones. Rudder blades, particularly on aluminum vessels, are often fabricated from aluminum. Of the various aluminum alloys, only a few possess the necessary corrosion-resistance and strength necessary for use as rudderstocks. Of these, the 6000 series, and 6082 in particular—an alloy of aluminum, manganese, and silicon—are popular for this application.

Because aluminum, like stainless steel, suffers from corrosion, it should not be used as stock or web material in composite rudders. Referred to as poultice corrosion, it occurs when aluminum is exposed to oxygen-depleted water. Because oxygen is what allows aluminum to form its tough, corrosion-resistant oxide coating, the metal should never be allowed to remain wet and starved of air as it would be inside a composite rudder blade after water makes its way in around the stock and pintle.

Rudderstock material can corrode in way of the oxygen-starved environment around the packing in a stuffing box.

Bronze, a once popular rudderstock material, is no longer common in today’s production vessels. Although strong and exceptionally corrosion resistant (immune to crevice corrosion), bronze is not easily welded to attach to a rudder’s internal structural webbing, and has thus been supplanted by stainless alloys. Bronze rudderstocks, particularly those that have seen many sea miles, are also known for wearing, or hourglassing, within stuffing boxes, where the flax rides against the stock. If a bronze stock rudder is chronically leaky, disassemble the stuffing box and check for excessive wear. The same is true for stainless and aluminum stocks: chronic leakage is often an indication of corrosion at the packing. Finally, because of their galvanic incompatibility, neither bronze nor copper alloys should be used aboard aluminum vessels for rudderstocks or any other rudder or stuffing box components.

Mild-steel webbing welded to a stainless-steel rudderstock is a recipe for eventual corrosion and failure.

The webbing, or internal metallic support system, in most composite rudders must be strong enough to carry the loads of service and be made of the appropriate material. At one time, many rudders were built using stainless-steel stocks and ordinary, rust-prone mild or carbon-steel webbing. Inadvisably, some still are. The union between a stainless stock and FRP rudder blade is tenuous at best (the two materials expand and contract at different rates) and stainless steel’s slippery surface makes adhesion to the laminate resin a short-lived affair. Once water enters the gap between these two materials, it will reach the webbing and associated welds. Thus, all the materials within this structure must be as corrosion- and water-resistant as possible, and the core material must be closed-cell—often foam—and nonhygroscopic.

This destroyed foam-core and stainless-steel rudder reveals the conventional construction of such appendages.

Additionally, where possible, the stock should consist of a single section of solid or tubular material; i.e., it should not be sleeved, reduced, or otherwise modified or welded unless done so in an exceptionally robust manner. The webbing must be welded to the stock, but the structure of the stock should not rely on a weld that would experience cyclical, torsional loading.

The webbing in the form of a plate or grid should be welded to the stock with ample horizontal gussets (small wedges welded where the stock and webbing interface), which will reinforce welds 90° to the primary web attachment.

Whether the rudder is spade (supported only at the top) or skeg hung (supported at the top and the bottom), the stock must pass through and be supported by the hull. This is usually accomplished by a component known as a rudder log, or port. In its simplest form it’s a tube or pipe through which the stock passes. Nearly all logs incorporate two other components—a bearing and a stuffing box. The bearing may be as simple as a bronze or nonmetallic bushing or tube inside of which the stock turns; or it may be as complex as a self-aligning roller-bearing carrier that absorbs rudder deflection and prevents binding.

This rudder log is leaking, corroded, and poorly supported, with washers compressing into the backing plate and gelcoat cracking off.

The log transfers tremendous loads and must be exceptionally strong and well bonded to the hull. Fiberglass vessels should rely on a well-tabbed-in purpose-made tube (its filaments are wound and crisscrossed and thus quite strong) that is supported with a series of vertical gussets that distribute the load to the hull’s surrounding structure. On some spade rudder installations, particularly where the log is not, or could not, be long enough, an additional bearing is used at the top of the stock, above the quadrant, where it is supported by the vessel’s deck.

On metal boats the design is similar but with a metal tube welded in place, supported by substantial gussets. For vessels with skeg-hung rudders, the strength of the rudder log is still important. However, because the loads are not imparted by a cantilevered structure, logs used in these applications may be less substantially supported.

Stuffing Box

Unless the rudder log’s upper terminus is well above the waterline or on the weather deck, it is typically equipped with a stuffing box similar to those used for propeller shafts. But unlike a shaft stuffing box, the rudder’s stuffing box shouldn’t leak much, if any, seawater. Because the rudder turns slowly, friction and heat are not a problem. Packing (i.e., waxed-flax packing like that in traditional stuffing boxes) can typically be tight enough to stem all leakage, and lubricating it with heavy water-resistant grease will reduce friction and leakage.

Stuffing boxes that are above the waterline while the vessel is at rest, such as those on many sailboats, are often the most chronically leaky, because the packing tends to dry out and contract. To avoid this, liberally apply grease to the packing material itself; this requires partial disassembly of the stuffing box. Alternatively, a galvanically compatible (316 stainless or Monel for bronze stuffing boxes) grease fitting may be installed and periodically pumped with grease to keep the packing lubricated.

Rudder Bearings

Well-engineered rudder bearings support and lubricate the rudderstock.

Rudder bearings range from the basic rudderstock turning inside a bronze log, to the sophisticated aluminum, stainless, or nonmetallic roller bearings installed in a self-aligning carrier. For most cruising vessels, the choice of bearing is not as important as knowing which type of bearing is in use and its strengths, weaknesses, and maintenance needs. The simple shaft that turns inside a bronze log is durable and reliable but more friction-prone than roller bearings. If lubrication access or a grease fitting is available, it should be pumped with grease periodically, although most rudders rely solely on seawater for lubrication, which is perfectly acceptable.

This synthetic upper bearing worked fine in cool temperatures, but when it heated up in the sun, the material expanded and caused binding in system.

Nonmetallic sleeve and roller bearings, often made of ultra high molecular weight polyethylene (UHMWPE), require no maintenance, are extremely slippery, and will not absorb water, an essential attribute for nonmetallic bearings. Delrin and nylon, for instance, will absorb water, expand, and lead to rudder binding. On several high-performance sailing vessels, I’ve had to replace nylon or similar bearings with UHMWPE to restore the steering to its proper specification and effort level.

Propeller Removal

Shaft removal should be possible with the rudder in place. This conventional skeg-hung rudder has a hole to facilitate shaft removal when the rudder is swung hard to port or starboard.

Whether a rudder is a spade or skeg-hung design, it’s important to determine how it will affect the removal of the propeller or the propeller shaft. Is there enough clearance between the shaft’s trailing end and the leading edge of the rudder to allow the propeller to be removed or to use a propeller removal tool? Can the shaft be slid out without removing the rudder? Some rudders are equipped with shaft-removal holes, while others are installed slightly offset from the centerline; or the rudder’s leading edge has an indentation to allow the shaft to be removed. The propeller should be removable without having to unship the rudder. The dimensional rule of thumb calls for clearance of at least the prop’s hub length between the aft end of the shaft and the leading edge of the rudder.

Rudder Stops

The rudder’s movement should be unimpeded as it swings approximately 35° in either direction, making no contact with hull or propeller. Just as important as the rudder travel is how its movement is checked. Other than for the smallest runabouts with jacketed cables, all inboard rudders should rely on hydraulic cylinders to check rudder travel (provided they are designed to do so, and most are) or be equipped with robust stops. Stops must be integral to the hull, supported by substantial tabbing or a welded and through-bolted structure for fiberglass vessels, or by welded angle and shelves for metallic hulls.

About the Author: For many years a full-service yard manager, Steve now works with boatbuilders and owners and others in the industry as Steve D’Antonio Marine Consulting. He is an ABYC-certified Master Technician, and sits on that organization’s Hull and Piping Project Technical Committee. He’s also the technical editor of Professional BoatBuilder .

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Rudder Types for Sailboats

A rudder is a one-of-a-kind technological achievement for sailboats. There are a handful of rudder types for sailboats to allow sailors to steer.

March 16, 2023

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Today’s sailboats use various rudders that serve unique purposes in steering or performance. You are probably wondering which rudder type you have on your boat and which one is best.

There are four types of rudders, which are skeg, spade, outboard, and full. Depending on the size of the boat and the hull will determine which rudder it will need. In addition, each rudder type will have a slight variation that will meet certain expectations of performance on the boat.

Sailors need to rely on a rudder in order to steer their boat efficiently. Each boat will not have the same rudder, as different styles of sailing require different rudders.

According to experienced sailors, each rudder has its pros and cons. However, the best rudder needs to match your expectations in sailing.

Table of Contents

‍ Rudder Types

With the four rudder types mentioned, each one will have its pros and cons. As you begin your travels on bluewater or are interested in learning more, then it would not hurt to check out what each rudder is designed to do.

Full Keel Rudder

If you were to picture a sailboat with a rudder, it would likely be a full keel rudder. The most common rudder type is the full since a lot of sailboats use a full keel.

The reason a full keel is the most common keel on a sailboat is that it is the best one to provide stability. In that case, you need a rudder that can accommodate that type of boat.

On a full keel sailboat , the rudder looks like it is part of the keel itself. It is actually attached on a hinge, giving it the appearance that it is fully connected to the keel.

Advantages of a Full Keel Rudder

A full keel rudder is quite strong and actually helps tremendously with the protection of the boat. During a strong storm or harsh waves, it can be easier to navigate with this type of rudder. In addition, debris is significantly less likely to snag on anything like other rudders.

Disadvantages of a Full Keel Rudder

While a full keel rudder might be the best one to handle in strong storms, it is still the most difficult rudder to handle. Since the flow of the water is providing pressure on the full keel, it makes it harder to move the rudder. You would need to put a lot of effort into steering, especially in harsher conditions.

Skeg Rudders

Skeg rudders might give a full keel rudder a run for its money due to its durability. These are often referred to as skeg mounted rudders.

These are similar to full keel rudders, but can also be used on fin keel boats . This alone gives it a slight edge over full keel rudders, but each boat design will differ.

Advantages of a Skeg Rudder

With similarities to a full keel rudder, you are going to have the stability as well in a skeg rudder. The added bonus is that it works in either a full keel boat and a fin keel.

Disadvantages of a Skeg Rudder

Just like a full keel rudder, all of the pressure of the water hits on one side or the other. This means it will be hard to turn in rough conditions.

Spade Rudders

These rudder types are best fit for a fin keel boat rather than a full keel or to the types of boats. It enters straight down into the water and can rotate left or right using a post that extends within the hull.

Advantages of a Spade Rudder

The best advantage of a spade rudder is that it can be part of the fin keel. You can turn this rudder much easier than a full keel rudder or skeg rudder. The water is not forced one side or the other, allowing a better flow and easier turn.

Disadvantages of a Spade Rudder

If you sail upon a lot of debris in the water, you are likely going to damage the rudder. These are more delicate than skeg or full keel rudders, as they are more exposed.

Debris can get caught in between and potentially wrapped within the space rudder. In addition, rough water can be a nightmare. Tough conditions can cause enough pressure to bend or potentially break the rudder.

Outboard Rudder

Outboard rudders are not attached to the boat’s hull and are mounted outside at the back . Typically, these are not connected to a steering wheel and are connected by a tiller.

A tiller is a steering lever that can take some getting used to if you have solely used steering wheels. On smaller boats, sailors actually like a tiller over a wheel.

Advantages of an Outboard Rudder

If an outboard rudder becomes damaged, it will not typically affect the rest of the boat. This is because there is not a rudder post through the hull.

In the event that you damage it while at sea, you have the opportunity to fix it. Since it is on hinges and not attached to the hull, it might be able to be fixed. This also means the rudder might be stronger than other rudder types.

Disadvantages of an Outboard Rudder

Since the outboard rudder is at the back of the boat, it is vulnerable in some situations. If floating debris or something like a rope is in the water, it can tangle up in the rudder or damage it.

The location of the rudder also makes it harder to turn than a spade rudder. In tough conditions, this might be difficult to turn.

Purpose of a Rudder

A rudder is one of many important components of a boat to operate as efficiently as possible. Some boats are built for speed and others for comfort, so a rudder also has to fit that category.

Water pressure will dictate how the rudder moves in the water. Whichever direction you turn the rudder, then water pressure will push against it and allow you to turn.

While a sailboat is turning, it is pivoting around a middle point of the boat. The stern and bow move at the same time, while the middle point of the boat remains in place. Knowing how to properly operate a rudder to steer can make a huge difference in avoiding a crash.

Variations of Rudders

While some rudders are fairly cut and dry for their intended use, other rudders have slight variations to the design. This allows a little bit of flexibility on some boats, which is great because not all boats are designed the same.

Balanced Rudder

A balanced rudder is a form of a spade rudder with a slight difference in free space at the top. The leading edge allows rotation from one side of the boat while the trailing edge goes opposite.

The post is also a few inches back from the front of the rudder, which is slightly different from a regular spade rudder. Even though the turning action is roughly the same in comparison to a spade rudder, the force on the helm has more balance and makes it easier to steer.

You will usually see this type of rudder in performance boats or yachts. Furthermore, they are always paired with a fin keel to provide the best performance overall.

The only drawbacks to a balanced rudder is that it is susceptible to debris if you were to run anything over in the water. You have to rely on the structural integrity and hope that it is strong enough to take a blow. If it were to fail, it does not revert back to the center and might make it difficult to navigate the boat.

Unbalanced Rudders

Unbalanced rudders have the support from a full length skeg and are attached to the furthermost point of their span. It is unbalanced because the entire rudder is aft of its axis or the centerline where the rudder stock is located.

When you begin turning this rudder type, you get all of the force on one side. Whoever is steering the boat will notice this feeling compared to other rudder types, especially when using a tiller.

As you can gather, these rudder types are not commonly used today. You might find one used in history books or replicas of older boats.

If this were commonly in use today and were to fail at sea, the rudder remains in place and not go back to the centerline. This caused serious issues in the past and arguably why it is not very popular anymore.

Semi-balanced Rudders

If you can picture what a balanced and unbalanced rudder would look like, then a semi-balanced rudder is something in between. The name suggests that it is partially balanced and unbalanced at times.

The top part of the rudder is unbalanced, while the lower part is balanced. With the top part being this way, it helps by providing structural support to the rudder by aiding in vertical displacement.

During this process, the balanced section will endure less torque pressure during swings. It will then return back to the centerline if the steering equipment fails, which is a critical aspect that balanced and unbalanced rudders did not originally have.

Semi-balanced rudders are also different from other types since they vary in size and shape. You will often hear sailors talk about the depth of the horn, which is the connection between the rudder and the boat.

A shallow horn rudder has a horn that extends less than half of the chord length from its top. In a deep horn rudder, the horn extends more than 50 percent of its chord length from the top.

Semi-balanced rudders have had some unique innovations over the years. They appear to be the best of both worlds between balanced and unbalanced.

Twin Rudders

Twin rudders have been used since 1980 among racing boats. Over the last decade or so, they have increased in popularity among cruising sailboats.

Twin rudders have a history of being difficult to operate in tight spaces if you do not have experience with them. This is true, especially since it navigates a little differently than one rudder.

When using a boat that has a twin rudder, the prop wash moves by both rudders and you cannot have the same maneuverability as with one rudder. One tactic you could do is to increase your boat speed to increase water flowing between the rudders. In doing so, it could cause some concern in tight spaces if you are unable to land exactly where you want.

One positive to twin rudders is that it performs well in reverse. You do not have as much prop walk as other boats and can handle better in lower speeds due to increased blade length on both rudders.

Another benefit is that it responds better to the wind. In single rudder boats, the wind can push the bow in one direction while the stern goes opposite. For twin rudders, the wind does not have as much of an impact in that regard.

Can Rudders Fail While in Use?

Just like anything in life that you use, it has a lifespan on it. For a rudder, some can fail while you are using them at sea.

Rudders failing at sea is actually a common hazard, so knowing what to do in that situation is very important. Sometimes cheaper boats, like a fiberglass boat, will experience a rudder failure likely before a more expensive boat.

The material of the rudder pole has to be a good blend of flexibility and strength. If it is too weak, it will break. If it is too strong, it might damage the hull since it cannot flex properly.

The framework inside the rudder should be a heavy-duty metal, because if it breaks, then it will be unusable. This is likely the case in cheaper boats, where costs have been cut in certain areas. Depending on the boat brand, you might see welding jobs that are not executed properly for rudders.

In addition, the type of rudder you use at sea can make a big difference. Full keel rudders might be the best option since it is protected from debris and offers the best stability. Depending on your sailing goals, the right rudder type will be different for everyone.

What are Rudders and Stocks Made out of?

Rudders have historically been crafted out of heavy duty stainless steel or aluminum. You want something that is non-corrosive and can withstand some beating.

If you were to look at high performance yachts, these typically have alloy since it is lighter but also strong. Stainless steel can handle swelling and debris, but crevice corrosion could be an issue.

Composite is another material that is used in mass production yachts or high performance boats. Some material is arguably better than others, but there is really not a perfect option out there. A proper inspection is needed before doing any long term use at sea.

Why a Tiller Could be Better than a Wheel for Rudders

If you have sailed a boat with a steering wheel and have never used a tiller, you could be missing out. Regardless if you are new to sailing or a seasoned pro, a tiller is very easy to use.

Tillers provide instant feedback when turning a boat, whereas steering wheels take a minute to get results. For newer sailors, a wheel could prove to be frustrating in rough conditions.

Depending on the size of your boat, a wheel might be the better option. In larger boats, a tiller does not perform the same.

Even though a tiller is harder to turn, it still offers an immediate reaction. This is why you will oftentimes see tillers on racing boats because they provide instant feedback.

What Happens if Your Rudder Fails?

While safety is a priority in everything you do while sailing, there are some situations you cannot avoid. No matter how much preventative maintenance you do, your rudder might still become damaged or unable to use.

If bearings have seized, the rudder can become difficult to move at first but will eventually lock up. Your steering capability will eventually be impossible and quite difficult to stop the boat from rounding into the wind.

If it were to fall off completely, then you will have quite a difficult time tracking the boat. The rotation of the boat might even be abrupt or rapid.

It is important to stay calm during a situation like this and to check on the crew. Drop your sails and attempt to gain some control.

You could even try pointing the bow into the wind and dropping anchor to reduce motion. Once the boat is under control, check for damage and call for assistance.

If you cannot phone for assistance, the best thing you can do is to create a makeshift rudder or potentially purchase one before a situation like this happens. For example, brands like Seabrake and Delta Drogue are quality rudders you could use in a pinch to safely make it back to shore.

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What’s the best rudder design and why are Sirius Yachts so easy to manoeuvre?

If you’ve seen the videos of our deck saloon sailboats manoeuvring effortlessly in the tight space of a marina, you may wonder how we can make it look so easy. The simple answer is that it looks easy because it is easy. Years of practice are absolutely not required as we prove on every test sail; after 10 minutes of simple instruction anyone on board who is more than eight years old can manoeuvre a Sirius with the same confidence. Part of the reason our yachts are so easy to manoeuvre is rudder design, combined with the position of the propeller.

A rudder needs to work well for both sailing and motoring, but many believe a rudder can only be good for sailing or motoring, not both. Most boatbuilders nowadays just focus on producing a rudder that’s efficient for sailing, but it doesn’t have to be one or the other. You can indeed have both. We even have a solution for hard-to-manoeuvre twin-rudder yachts, which have no prop wash to steer with.

The three rudder options we offer

We offer three rudder options. The first is a single, partially balanced spade rudder with a skeg for added protection. This is the standard setup on all our fin-keel yachts and also on the twin-keel versions.

On all our lifting keel yachts we use twin rudders because when the yacht is dried out, the height from the hull to the sea bed won’t allow enough span (rudder height) to give good control under sail. Instead of one deep rudder, we use two shorter rudders, angled outwards at the bottom so that at any heel angle one rudder is always fully immersed and close to vertical for optimum performance. Twin rudders also give the security of a wider support base when the boat is dried out.

The third option is three rudders: the standard twin rudders as above plus a small, central third rudder whose sole purpose is to improve manoeuvrability under power, especially from a standstill and at low speed.

Siriuus Yachts - Our twin-rudder boats have the option of a third rudder

The best rudder design for motoring

Let’s first look at how our rudders are optimised for use under power. If we were making a motorboat, the rudder would have little or no area forward of the rudder stock. It would only need to be the height of the propeller, and the distance between rudder and propeller would just be a quarter to half of the propeller’s diameter. Most motorboats are steered entirely by prop wash (the flow of water from the propeller passing over the rudder). As mentioned above, our twin-rudder boats also have the option of a smaller, central third rudder. Like a powerboat rudder, it steers the boat by efficiently deflecting prop wash and also directing a laminar current onto the two rudders.

Life isn’t so simple for our single rudder designs; they have to be equally efficient under sail and power. To get maximum manoeuvring efficiency from prop wash we locate the propeller at an optimum distance from the rudder, so that the cone-shaped, moving mass of water is the same height as the rudder when it hits it. The positioning has to be precise. The rudder blade needs a large surface area for efficient performance under sail, and if it’s too close to the propeller there will be a lot of pressure on the rudder, making it heavy on the helm with lots of vibration under power. If it’s too far away from the propeller, the energy of the prop wash dissipates into the surrounding water before it hits the rudder. One reason we prefer saildrives, rather than shaft drives, is that they allow us to fit the engine in what would typically be an aft cabin (this is one reason why the aft cabin of the Sirius 40 DS is transverse), which puts the propeller in an optimal position and gives the owner an excellent mid-cabin plus a workshop. We do also fit shaft drives to some of our yachts, but they generate more noise and vibration and this moves the engine a bit further forward. You can have whichever drive you prefer.

Sirius Yachts - The rudder blade needs a large surface area for efficient performance under sail

When a yacht is motoring, the area of rudder blade forward of the post (or stock) is doing the most work. It’s under the highest pressure from prop wash and helps to deflect more water over the high-pressure side of the rudder. The area forward of the stock also helps to balance the helm. Without it, the rudder would require more effort to turn. But if there is too much surface area forward of the stock, the rudder will become unbalanced and twitchy under sail – the helm will require constant attention, which is clearly a bad thing on a cruising yacht. It’s all about striking the right balance (if you’ll excuse the pun) between a rudder that provides a good steering response and one that is not hard work to turn at high speed.

The water pressure is highest at the point where the prop wash hits the hull, and because our propeller is closer to the rudder than on most other boats, a lot of pressure is exerted on the top (or root) of the rudder. One way to avoid it experiencing too much pressure is to remove the area forward of the stock where the pressure is highest. We do this with the addition of a skeg. Under power, the skeg absorbs the water pressure and directs the flow of water over the rudder. It acts like the wing of an aircraft and the rudder is the control surface on its trailing edge – if the whole wing of an aircraft were to move in flight it would be very unstable, it’s the same principle. The skeg stabilises the flow of water, so by the time the water hits the rudder there is minimal turbulence. This translates into less movement and vibration of the rudder under power. Adding a skeg is an expensive complication in the production process, that’s why it is rarely seen in production yachts. Twin-rudder yachts don’t suffer the same way because the turbulent water from the propeller passes cleanly between the rudders, and in our triple-rudder design the third rudder is small enough and designed not to be affected.

The best rudder design for sailing

Our yachts are not just designed for party tricks in marinas, they are also designed to sail well. So any rudder design we use has to work at least as well, if not better, for sailing as it does for motoring. To achieve this the rudder blade must be deep, so when the yacht heels there is still enough of the rudder in the water to maintain control. Under sail, it’s the trailing edge of the rudder that is doing the work and is under the most pressure.

Sirius Yachts - The rudder blade must be deep to maintain control when the yacht heels

Why twin rudders have become popular

There is a trend for yachts to carry their maximum beam a long way aft to enlarge the aft cabins. Sirius yachts don’t need the aft cabins to be the master cabins because the accommodation is on two levels, and we prefer to keep our cockpits low down for greater comfort in rough seas. For single-rudder boats, the problem with a broad, overly buoyant stern (apart from excessive heeling and being vulnerable when docking) is that as the boat heels, the root (top) of the rudder is lifted out of the water. If the top 30cm (1ft) of a 1.3m (4ft 3in) rudder blade comes out of the water, more than a quarter of the blade’s effectiveness is lost. The top quarter of the blade becomes useless and the rest of the blade is operating in less dense water. The angle the blade is working at also makes it less effective and when under pressure it will ventilate: a vortex of air swirls down one side of the rudder, which loses its grip in the water, causing a sudden loss of control as the boat rounds up into the wind. To stop that happening, the crew needs to play the mainsheet constantly in gusty winds, which is exhausting if you’re sailing long distances, and the yacht will need to be reefed (and unreefed) more often.

Sirius Yachts - Many yachts have twin rudders that are angled outboard on each side of the stern

To avoid this effect, many yachts have twin rudders that are angled outboard on each side of the stern. As the yacht heels, the leeward rudder is pushed into deeper, denser water and becomes vertical, making it more efficient. Twin rudders tend to be narrow-chord with a short span (short and skinny) and they must be set well apart to make them efficient while sailing. The problem is that there’s no prop wash over the rudders when manoeuvring in harbour, so unless the yacht is moving relatively fast through the water you have no steerage. When the yacht is stationary, she cannot be turned by applying helm and giving the engine a burst of power. Only when there is water passing over the blades at a speed faster than is prudent in confines of a marina will the yacht start to turn. One way to overcome this trait is to fit a retractable stern thruster in addition to the bow thruster, but they come at extra expense and need to be operated simultaneously with the rudder and engine and bow thruster, as well as using more power. Also, they take up space inside the hull and they’re something else for debris to catch in.

Sirius yachts don’t have fat aft quarters, they have a more balanced hull form for better all-round performance and comfort and safety at sea, so we don’t need twin rudders or stern thrusters – a single rudder works well. When a Sirius heels, the rudder blade is deep under water and remains fully immersed.

The reason we use twin rudders on some of our yachts

We do, however, use twin rudders for a different reason on our lifting-keel and twin-keel yachts, which are designed to dry out. With a draught up to 75cm (2ft 5in), a single rudder wouldn’t have a long enough span to work properly. Where we fit twin rudders, they have a relatively long chord (wide blade) and because our hulls are only moderately wide at the stern, the rudders are quite close together. A burst of power from the engine can be diverted by the rudders, creating a turning effect – not as much as with a single-rudder boat, but more than most twin-rudder yachts.

Sirius Yachts - We use twin rudders on our lifting-keel and twin-keel yachts

We can fit twin rudders on any of our yachts. We offer the option of twin electric drives (for propulsion and power regeneration) and we recommend twin rudders, one behind each drive, to give the very best manoeuvring ability. Not only is the thrust directed over both rudders, the two drives can be powered individually so with one drive in forward and the other in reverse she will pivot on the spot.

Sirius Yachts - A well-designed, strong rudder design doesn’t need a skeg for support

Construction of the rudder and skeg

As mentioned above, our single rudders have a half skeg that serves many purposes. As well as absorbing the energy of turbulent prop wash at the top of the rudder it also helps direct the water passing onto the rudder blade while sailing. It boosts the efficiency of the rudder and also protects it from hitting submerged objects. Inside the skeg is a stainless-steel structure that is through-bolted and bonded to the hull. We don’t hang the rudder off the skeg, though; three bearings would create a rudder that is harder to turn when heeling and wear out the bearings faster. Instead, we use two self-aligning bearings. A well-designed, strong rudder design doesn’t need a skeg for support, only for protection.

The wide foil at the tip of the rudder spreads the load and prevents the rudder blade from sinking in

A rudder to dry out on

We use an alloy stock in our rudder blades that is optimised for seawater and strength. The blade is built in two parts, laminated onto the stock on the inside, and filled with closed-cell foam then laminated along the leading edge. On our yachts that are designed to dry out, the rudder has a wide foil on the tip to give a larger surface area for the rudder to rest on. When our twin-keel yachts dry out on concrete or any other hard surface, the rudder will be about 80mm (3in) off the ground and she will sit happily on her keels – we wanted to see how stable, so we had 12 guys jumping up and down on the stern and they were unable to get her to move.

Sirius Yachts - The rudder is designed to provide a stable tripod stand for the hull

On softer surfaces, like sand and gravel, the keels sink in by about 2-5cm (1-2in). Our boats’ longitudinal centre of gravity is slightly aft of amidships, so the stern tends to sink in a bit further. The wide foil, or foot, at the tip of the rudder spreads the load and prevents the rudder blade from sinking in. The rudder has a Delrin sheave to transfer the weight onto the hull and it is designed to provide a stable tripod stand for the hull. The rudder is deliberately a little shorter than the keels for added safety – when you run aground while feeling your way into your perfect spot to dry out, the keels will touch the bottom before the rudder does. On our lifting keel models, the twin rudders support the stern of the boat so she will dry out upright.

General Manager – Torsten Schmidt SIRIUS-WERFT GmbH Ascheberger Straße 68 24306 Plön/Holstein

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Practical Boat Owner
Digital edition

How to build a rudder for your boat

August 30, 2023

Hitting a submerged object destroyed Mike Gudmunsen’s rudder...so he set about making a new one

The rudder horn on Mike Gudmunsen's yacht had parted company from the palm, leaving the two sides of the palm still bolted to the hull. Credit: Mike Gudmunsen Credit: Mike Gudmunsen

How to build a rudder

The Blackwater estuary above Osea island dries at low water, writes Mike Gudmunsen .

Over the years, wooden jetties, fish traps and even barges have been left to decay at the margins, presenting hazards for the unwary – along with more recent man-made obstacles such as the causeways to Osea and Northey islands.

The spring tides were pretty big and the river had swelled, covering the surrounding salt mashes. Northey island had all but disappeared, apart from the hillock upon which the farm building sits.

I’d enjoyed a good sail around Osea island in my Pegasus and had time for a brew in Goldhanger Creek, but on leaving I became disorientated due to the unusually large expanse of water.

I strayed into an unfamiliar inlet and this was my undoing, as no sooner was I in than I was aground.

Frantic engine manoeuvres and rocking the boat on its keels released the boat, then as I proceeded back towards the main channel there was a resounding crash, the boat stopped dead and the tiller was wrenched from my grasp – I’d hit a submerged object and, whatever it was, it was pretty hard.

A damaged yacht rudder hanging from the hull of a boat

Although Mike had previously reinforced the hull around the rudder connection, the grounding still did damage. Credit: Mike Gudmunsen

From the tiller angle and the visible damage to the transom top in way of the upper rudder bearing, something was very wrong.

With minimal steerage, we limped back to our mooring further upriver to contemplate what to do next.

When we hauled the yacht out and inspected the damage, we found the rudder horn had parted company from the palm, leaving the two sides of the palm still bolted to the boat hull .

I’d reinforced the hull around this connection back in 2009 as I was concerned about the potential effects following an impact on the rudder – fortuitously, as it turned out.

Without this additional reinforcement, I suspect the bolts would have been pulled through the GRP and I could have been looking at a total loss.

The remains of the palm. Credit: Mike Gudmunsen

Pegasus yachts have a rather unusual rudder arrangement.

A cast aluminium rudder horn, which forms the leading edge of the rudder for about half its depth, is bolted via a palm to the hull.

At its lower end, a pintle bearing supports the rudder and takes most of the lateral rudder force.

A hollow stainless steel shaft passes through the pintle bearing and terminates above the transom at the tiller head.

Having removed the rudder and unbolted the remaining bits of the palm, I toured various boatyards and marinas hoping to get the rudder repaired.

The builders of Pegasus yachts went out of business many years ago, and it was evident that a replacement cast rudder horn was as rare as hen’s teeth.

So, the only option was to design and fit a spade rudder and move away from the original ‘mariner’-style rudder arrangement.

Designing a new rudder

The helm has always been light and responsive, so I was anxious to maintain those qualities in the new rudder.

I kept the original rudder dimensions and aspect ratio and also the rudder stock position relative to the leading edge.

The original rudder had a chord of 410mm and a maximum thickness of 63mm.

A NACA 0015 aerofoil is very close to these requirements, and I was able to get the section offsets from a site on the internet.

There are important differences between the original ‘mariner’ rudder and the proposed spade rudder .

A rudder horn which is needed when fitting a rudder

A cast aluminium rudder horn, which forms the leading edge of the rudder for about half its depth, is bolted via a palm to the hull. Credit: Mike Gudmunsen

The original carried the rudder lateral force via the pintle bearing and into the rudder horn which resists bending at the bolted connection to the hull.

With this arrangement, the rudder stock essentially only carries the rudder torque and, as a consequence, the shaft can be hollow and of modest diameter.

Mine was 38mm diameter with a 3mm wall thickness.

For a spade rudder, the stock itself has to resist bending, shear and torsion, and would clearly need to be a lot thicker and possibly solid.

Calculating the loads on the rudder

A quick trawl on the internet will give numerous references to methods to calculate the forces on a rudder.

They basically all use the blade area (Ar) and the boat speed (V) in knots, together with a few other parameters such as lift coefficient, blade aspect ratio and so on.

For my chosen aerofoil section, I took the design lateral force (Dlf) on the rudder blade, measured in Newtons, to be:

Dlf =100A(V+3)2

The eagle-eyed will notice that lift coefficient and aspect ratio don’t figure in this equation as my 3-knot augmentation of the speed may be considered to compensate for these effects.

The original rudder was 980mm high with a chord of 410mm, giving an area of 0.4018m2.

I took the design speed of my 26ft yacht to be 5 knots. Hence, the lateral force came out to be 2,572N (262kg).

This force acts at the vertical centre of the blade area and, for the NACA section I had selected, at 1⁄3 of the chord from the leading edge.

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Having decided on the location of the upper and lower bearings, a simple moment calculation about the top bearing gave the reaction force at the lower bearing (3,983N): likewise, taking moments about the lower bearing gave the reaction force at the upper bearing (1,411N).

By multiplying the lateral rudder force by the distance from the blade centre of area to the lower bearing, the bending moment was determined:

Mb = 0.483m x 2,572 N = 1,242Nm

The torque on the rudder (Mt) was calculated by multiplying the lateral force by the separation between the shaft axis and the centre of pressure.

For my rudder it worked out to be 2,572 x (0.41 x 0.33-0.10) = 91Nm; roughly 10kg.

Interestingly, classification societies set a minimum separation value of 0.12 x chord, which results in a larger torque of 127Nm.

Will the shaft be thick enough?

The rudder shaft would be of 316-grade stainless steel.

Although stainless does not exhibit a yield point, a value of stress for a defined percentage of plastic strain is generally used to represent the nominal yield.

Data from the internet gave a UTS (ultimate tensile strength) of 485N/mm2 and a nominal yield value of 210N/mm2.

The shaft diameter would be limited by the diameter of the existing rudder trunk and also the thickness of the rudder blade.

The rudder trunk had an internal diameter of 50mm.

The rudder blade thickness of 63mm, less two layers of 9mm ply, permits a maximum shaft diameter of 45mm, so it was clear that 45mm would be the largest diameter that could be accommodated in association with these physical limits.

In order to confirm the structural adequacy of the shaft, a few basic calculations needed to be undertaken.

A 45mm-diameter shaft has the following attributes:

The shear area A = π r2 = 1,591mm2 s

Section modulus Z = Ππ d3/32 = 8,946mm3

The torsional constant J = Ππ d4/32 = 402,578mm4

The bending stress in the shaft Mb/Z = 1,242 x 1,000/8,946 = 139N/mm2

The average shear stress F/As = 3,983/1,591 = 2.5 N/mm2.

The torsional stress Mtr/J = 91 x 1,000 x 22.5/402,578 = 5.0 N/mm2

From the results, the dominant stress is the bending stress, and this provides a factor of safety on the nominal yield of 1.5.

The shear and torsional stresses are so small I basically ignored them.

Now I had the shaft diameter, the bearing dimensions could be calculated.

A Delrin spacer ring for a rudder on a boat

A Delrin spacer ring had to be arranged below the rudder carrier ring in order to take up the clearance. Credit: Mike Gudmunsen

Delrin has a good track record for rudder bearings – it’s easy to machine and has a very low moisture absorption characteristic, particularly when compared with nylon.

Published data on bearing pressures for synthetic bearing material suggests that the design pressures should not exceed 5.5N/mm2.

Based upon the bearing forces of 3,983N and 1,411N, I needed bearing areas of 724mm2 and 256mm2 respectively.

From a purely practical point of view, the bearing depths finally selected were 16mm at the upper bearing and 45mm at the lower bearing, both of which resulted in more than double the minimum areas needed.

The rudder build

The rudder shaft would be subject to some significant machining, and tangs would need to be welded to it in order to transmit the rudder torque to the shaft.

A local marina workshop did the job.

The rudder blade would be laminated from 9mm marine-grade plywood which, after shaping and fairing, was skinned with GRP and finally epoxied.

The bolting location of the original palm provided a convenient location for the new lower bearing.

A bearing plate bolted into place on a yacht

The bearing plate bolted in place. Credit: Mike Gudmunsen

Using a suitable mandrel as a dummy shaft, I fashioned a cardboard template for the lower bearing plate.

To be honest, I probably made three or four templates before I was satisfied that it was as dimensionally accurate as could possibly be.

A stainless steel tube carrying the lower bearing would need to be welded to this lower bearing plate at precisely the correct angle.

A local engineering shop produced the upper and lower bearing plates, the bearing tube, the Delrin bearings and the rudder carrier ring for me.

The final welding of the bearing tube to the lower bearing plate was carried out by a fellow club member using TIG welding. Credit: Mike Gudmunsen

A steel bush was used as a dummy bearing so the bearing tube could be tack-welded to the lower bearing plate while the rudder shaft was in situ.

Delrin apparently melts at around 160°, so it’s best kept away from the welding process.

Once removed, the final welding of the bearing tube to the lower bearing plate was carried out by a fellow club member using TIG welding.

Even though we left the dummy bearing in place, heat from the welding did cause the bearing tube to warp slightly, so the Delrin bearing had to be adjusted to fit.

The final fitting

The new spade rudder was considerably heavier than the old one and took two of us to offer it up through the rudder trunk, while another assembled the upper bearing components and carrier ring.

Once in place, the lower bearing plate was through-bolted to the hull.

When measuring the shaft length I’d added a 10mm margin to the overall length just in case things didn’t fit as planned.

The final rudder assembly. Credit: Mike Gudmunsen

In the end it proved 8mm over length, so a Delrin spacer ring had to be arranged below the rudder carrier ring in order to take up the clearance.

A club member donated the Delrin and carried out the machining for me.

Completion of the rudder replacement – including producing drawings for the marina and machine shops and calling upon a number of helpful club members to carry out machining and welding – took just over three months.

The whole project proved to be very rewarding and is well within the skills of most practical boat owners.

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Building a Faster Rudder

Boost performance with a bit of fairing and better balanced helm..

We’re cruisers not racers. We like sailing efficiently, but we’re more concerned with safety and good handling than squeezing out the last fraction of a knot. Heck, we’ve got a dinghy on davits, placemats under our dishes, and a print library on the shelf. So why worry about perfection below the waterline?

The reason is handling. A boat with poorly trimmed sails and a crudely finished rudder will miss tacks and roll like a drunkard downwind when the waves are up. On the other hand, a rudder that is properly tuned will agilely swing the boat through tacks even in rough weather, and provide secure steering that helps prevents broaching when things get rolly. The difference in maximum available turning force between a smooth, properly fitted rudder and the same rudder with a rough finish and poor fit can be as much as 50% in some circumstances, and those are circumstances when you need it the most. It’s not about speed, it’s about control.

It Must Be Smooth

Smooth is fast. That’s obvious. But it makes an even bigger difference with steering. Like sails, only half of rudder force comes from water deflected by the front side of the blade. The rest results from water being pulled around the backside as attached flow. How well that flow stays attached is related to the shape of the blade, which we can’t easily change, and to the surface finish of the blade, which we can.

Remember the school experiment, where you place a spoon in a stream of water and watched how the water would cling to the backside of the spoon? Now, try the experiment again as a grown-up, but with a different set of materials.

Try this with a piece of wood that is smooth and one that is very rough; the water will cling to the smooth surface at a greater angle than the rough surface. Try piece of smooth fiberglass or gelcoat; the water will cling even better because the surface is smoother. Try a silicone rubber spatula from the kitchen. Strangely, even though the surface is quite smooth, the water doesn’t cling well at all. We’ll come back to that.

Investigators have explored this in a practical way, dragging rudders through the water in long test tanks (US Navy) and behind powerboats.

If we are trying to climb to windward, it’s nice to get as much lift out of the rudder as practical, before drag becomes too great or before it begins to stall with normal steering adjustments. If the boat has an efficient keel and the leeway angle is only a few degrees, the rudder can beneficially operate at a 4-6 degree angle. The total angle of attack for the rudder will be less than 10 degrees, drag will be low, and pointing will benefit from the added lift. If the boat is a higher leeway design—shoal draft keels and cruising catamarans come to mind—then the rudder angle must stay relatively low to avoid the total angle (leeway + rudder angle) of the rudder from exceeding 10 degrees. That said, boats with truly inefficient keels but large rudders (catamarans have two—they both count if it is not a hull-flying design) can sometimes benefit from total angles slightly greater than 10 degrees—they need lift anywhere they can get it.

How can you monitor the rudder angle? If the boat is tiller steered, the tiller will be about 0.6 inches off center for every degree or rudder angle, for every 3 feet of tiller length. In other words, the 36-inch tiller should not be more than about 2 inches off the center line. If the boat is wheel steered, next time the boat is out of the water, measure the rudder angle with the wheel hard over. Count the number of turns of the wheel it takes to move the rudder from centered to rudder hard over, and measure the wheel diameter. Mark the top of the rim of the wheel when the boat is traveling straight, preferably coasting without current and no sails or engine to create leeway.

The rim of the wheel will move (diameter x 3.146 x number of turns)/(degrees rudder angle at hard over) for each degree of rudder angle. Keep this in the range of 2-6 degrees when hard on the wind, as appropriate to your boat. It will typically be on the order of 4-10 inches at the steering wheel rim. A ring of tape at 6 degrees can help.

How do we minimize rudder angle while maintaining a straight course? Trimming the jib in little tighter or letting the mainsheet or traveler out a little will reduce pressure on the rudder and reduce the angle. Some boats actually sail to weather faster and higher, and with better rudder angles, by lowering the traveler a few inches below the center line.

On the other hand, tightening the mainsheet and bringing the traveler up, even slightly above the center line on some boats, will increase the pressure and lift.

Much depends on the course, the sails set, the rig, the position of the keel, the wind, and the sea state. Ultimately, some combination of small adjustments should bring the rudder angle into the appropriate range. Too much rudder angle and you are just fighting yourself.

Turn this rudder just 10 degrees and the end plate is lost, reducing the amount of lift generated.

This rudder might as well be transom hung, the way that the end cap just disappears.

Stern-hung rudders, and spade rudders with large gaps between the hull and the top of the rudder will lose their lift at the “tip” of the blade near the surface.

Surface roughness affects the lift from the rudder in two ways. A rougher surface has slightly lower lift through the entire range of angles, the result of a turbulent boundary layer instead of smooth flow over the entire surface. More dramatically, rougher blades stall at lower angles and stall more completely. The difference between a faired rudder with a polished finish and a rudder carrying a 10-year accumulation of rolled-on antifouling paint can be as much is 35 percent (see “Rudder Savvy to Boost Boat Performance,” above).

What can we do? If your rudder is a lift up type, don’t use bottom paint. Fair the blade within an inch of its life and lay on a gloss topside paint as smoothly as possible, sanding between coats. If you use a brush, stroke the brush parallel to the waterline, not along the length of the blade.

Which is faster, a gloss finish or one that has been dulled with 1000 grit sandpaper? Opinions go both ways, and we believe it may depend on the exact nature of the paint, which leads to the question, “Should we wax the blade?” The answer is a resounding, no.

Wax is a hydrophobic (readily beads water), like the silicone rubber spatula you tested, and as a result, water doesn’t always cling as well. Thus, whether the paint should be deglossed or not depends on the chemistry of the paint, but in all cases the final sanding should be 1000 grit or finer.

If the rudder stays in the water, antifouling paint is required. Sand the prior coat perfectly smooth. There should be no evidence of chips, runners, or any irregularity at all. Using a mohair roller, lay the paint on thin, and apply multiple coats to withstand the scrubbing you will give your rudder from time to time.

Even if you use soft paint on the rest of the boat, consider hard paint for the rudder. Sure, it will build up and you will have to sand it off periodically, but the rudder is small and no part of your boat is more critical to good handling. Take the time to maintain it as a perfect airfoil.

Close the Gap

Ever notice the little winglets on the tips of certain airplanes? As we know, those are intended to reduce losses off the tip of the wing. The alternatives are slightly longer wings or slightly lower efficiency. At the fuselage end of the wing, of course, there is no such loss because the fuselage serves as an end plate. The same is true with your rudder.

There’s not much you can do about losses from the tip; making the rudder longer will increase the chance of grounding and increase stress on the rudder, rudder shaft, and bearings. Designers have experimented with winglets, but they the catch weeds and the up-and-down motion of the transom makes them inefficient. However, we can improve the end plate effect of the hull by minimizing the gap between the hull and the rudder.

In principle it should be a close fit, but in practice the gap is most often wide enough to catch a rope. Just how much efficiency is lost by gap of a few inches? The answer is quite a lot. A gap of just an inch can reduce lift by as much as 10-20 percent, depending on the size and shape of the rudder and the speed. A gap of 1-2 mm is quite efficient, but normal flexing of the rudder shaft may lead to rubbing.

If the gap is tight, the slightest bend from impact with a submerged log can cause jamming and loss of steering, though in my experience once the impact is sufficient to bend the shaft, a small difference in clearance is unlikely to make much difference; the shaft will bend until the rudder strikes the hull. Just how tight is practical depends on the type of construction, fitting accuracy, and how conservative the designer was in their engineering.

Carbon shafts, tubular shafts, and rudders with skegs flex less, while solid shafts generally flex more, all things being equal. Normally a clearance of about 1/4-inch per foot of rudder cord is practical, and performance-oriented boats often aim for much less. If you can reach your fingers through, that’s way too much. Hopefully the hull is relatively flat above the rudder so that the gap does not increase too much with rudder angle.

Practical Sailor’s technical editor Drew Frye is the author of the books Keeping a Cruising Book for Peanuts and Rigging Modern Anchors. He blogs at his website, sail delmarva.blogspot.com .

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Welcome to Jefa Rudder

We have rudder and bearings for your boat.

Who is Jefa Rudder?

Beginning in 1980, Jefa Rudder has supplied Rudder Bearings to over 40,000 boats. Jefa was founded by Jan Faurschou. Today Jefa Rudder is steered with the second generation at its helm, by Jan’s daughter Louise.

Did you know

Quality roller bearings.

All Jefa rudder bearings are produces with precision machined rollers and close tolerances to provide smooth operation under load. The close tolerance allows Jefa to eliminate the roller cage needed with sloppy bearings and keep the design simple for long term reliability.

Retrofit Bearings

Jefa Rudder produces replacement rudder balls for all old JP3 and Seaway (Bavaria, Elan, Salona, etc..) rudder bearing.

Jefa Rudder produces replacements for old Harken rudder bearings which is precisely match the original outer dimensions

Standard & self-aligning bearings

Jefa produces self-aligning bearings for rudder stocks engineered to flex. Self-aligning bearings also eliminate the need for precise alignment during installation. Standard or Non Self-aligning bearings are available at a lower cost and normally have a smaller outside diameter.

How a cargo ship took down Baltimore’s Key Bridge

Part of the Francis Scott Key Bridge ended up on the Dali container vessel after collapsing.

To bridge experts, the collapse of Baltimore’s Francis Scott Key Bridge after being hit by a heavy cargo ship was as unsurprising as it was devastating.

When a vessel as heavy as the Singapore-flagged Dali strikes with such force one of the span’s supercolumns, or piers, the result is the type of catastrophic chain reaction that took place early Tuesday.

“If the pier was destroyed like it was, the bridge has to collapse,” said Dan Frangopol, a bridge engineering and risk professor at Lehigh University and president of the International Association for Bridge Maintenance and Safety.

“If the column is destroyed, basically the structure will fall down,” he said. “It’s not possible to redistribute the loads. It was not designed for these things.”

Maryland officials did not immediately answer questions about what protective devices may have been place in the water near the bridge and whether they were sufficient for any strike of such an important span.

Ian Firth, a British structural engineer and bridge designer, reviewed video footage and said there appeared to be at least two protective objects in the water next to the Key Bridge. The objects, known as “dolphins,” are supposed to protect maritime structures from being hit by vessels. But Dali, the container ship that struck the bridge, appeared to have come in “at an angle,” Firth said, which means the devices were unable to prevent the ship from striking the bridge.

Firth said in a telephone interview he was not surprised at how quickly the bridge came down. He noted the support structure that was struck, which would have been made of reinforced concrete, was one of two main supports responsible for doing “all the work” to hold up the bridge.

He said the ship appeared to have strayed to one side before striking the bridge, which appeared to have a lightweight support structure.

If the Dali had been traveling straight on instead of at an angle, Firth said, it probably would have hit the protective objects. And if there had been three or four vessel-protection objects around the bridge, the outcome might have been different, Firth said, adding that he expects lessons will be learned from Tuesday’s tragedy.

Firth noted that the bridge was erected, in 1977, at a time when ships were not as big as they are now and the flow of traffic was not as busy. These days, structures are designed with better protective measures in place, he said, though he noted that even a brand-new bridge would have “come down in the same way” if it were hit by such a large vessel traveling at speed.

Firth called the incident tragic and “very rare indeed.” He said the large container ship would not have had to be traveling very fast to have had such an impact, one that the bridge was simply not engineered to withstand.

In video imagery, the ship can be seen losing electrical power, then briefly regaining it before going completely dark. The ship then veers to the right, directly toward the bridge’s structural support.

The rudder may have gotten stuck in a position that caused the ship to turn, said a senior retired maritime official, who spoke on background while waiting for more details on the incident. It’s also possible that an incoming tide could have been a factor, he said.

“Obviously, they could not control the ship. They could not stop the ship,” he said.

Ships coming in and out of Baltimore Harbor must be guided by a state-licensed pilot who is familiar with the shipping channel and navigational hazards.

Why the Baltimore bridge stood little chance against a fully loaded cargo ship

As questions surround the collapse of a Baltimore bridge after a containership crashed into it Tuesday, engineering experts say that while bridges have some built-in defenses against collisions, this one was most likely too extreme to withstand.

“Bridges are and should be designed to withstand ship impacts. That’s typical of the design process,” said Sanjay R. Arwade, a professor of civil engineering at the University of Massachusetts Amherst.

“But for all structures and all engineered systems, there is a possibility that an event will occur that is beyond what the structure was designed for. And this may be one of those situations,” he added.

The Francis Scott Key Bridge, a roughly 1.5-mile-long steel arch truss bridge, collapsed into the Patapsco River early Tuesday after a containership struck it. Several vehicles crashed into the water, and one of the country’s busiest ports shut down.

Follow live updates on the Baltimore bridge collapse

An unknown number of workers with Brawner Builders Inc. were repairing concrete ducts when the ship, called the Dali, hit a support pillar. Six employees are presumed dead .

Key Bridge was ‘fairly unprotected'

Arwade said design codes for modern bridges stipulate "what sort of loads it has to be able to resist.”

“Whenever a design code is written, decisions have to be made about what the most extreme conditions are,” he said.

Maryland Gov. Wes Moore said the bridge was "fully up to code."

But the Key Bridge was built in 1977, and bridge design and technology have improved since then.

"Since the 1970s, we have a lot of advancements," Sameh Badie, a professor of engineering at George Washington University, told NBC Washington. But he said, "I saw today a couple of videos before the collapse, and it seems to me, structurally wise, it was very safe."

Roberto Leon, a structural engineer at Virginia Tech, said that while engineers try to account for “extreme events” during the design and construction process, “when this bridge was built, there were no ships of this size.”

“This type of load was not really considered,” he said. “So the bridge was, I would say, fairly unprotected.”

Retrofitting older bridges could cost millions

Officials have not specified what type of protective infrastructure, if any, the Key Bridge had.

Leon said that on a newer bridge, large concrete structures called dolphins are often used to protect the base. Dolphins can form a kind of frame and are designed to take the impact of a vessel and “slow the ship down and redirect it away from the bridge,” he said.

“In some cases, they’re called sacrificial elements, because they might be damaged beyond repair if an event of this type occurs, but of course, they save the bridge,” he added.

John Pistorino, a structural engineer in Florida, said dolphins are in use to protect the Sunshine Skyway Bridge in Tampa, Florida, which was reopened in 1987 , seven years after it was hit by a freighter. Thirty-five people died after the bridge collapsed into Tampa Bay.

Pistorino, who was involved in the construction of the rebuilt Sunshine Skyway Bridge, described dolphins as walls or guardrails.

“They can be concrete or steel … and they go all the way down to the bottom of the river,” he said. “They’re supposed to protect the abutments.”

Jacksonville, Florida, Mayor Donna Deegan cited the dolphin infrastructure that's in place to protect the Dames Point Bridge — the only bridge in the city that cargo ships sail under — in a statement Tuesday. She noted that the bridge is also equipped with specialty sensors that provide real-time information about the distance between the water surface and the bottom of the bridge structure over the main channel.

Older and more vulnerable bridges can be retrofitted to add defensive infrastructure like dolphins, Leon said, but building them can cost hundreds of millions of dollars.

“I’m hoping that because of the infrastructure bill that passed, we are going to be able to do projects like this,” he said, referring to the $555 billion infrastructure bill that President Joe Biden signed in 2021. “Putting those into the budget and justifying them is very difficult when you have all kinds of other bridges that are in really sad shape. So it’s just a question of prioritization.”

However, Kevin Heaslip, director of the Center for Transportation Research and a professor of civil and environmental engineering at the University of Tennessee, Knoxville, said the cost of designing bridges to withstand fully loaded cargo ships like the Dali would “be so high that we wouldn’t be able to have any bridges.”

Image: Baltimore's Francis Scott Key Bridge Collapses After Being Struck By Cargo Ship

Government oversight of bridges could increase

Transportation Secretary Pete Buttigieg said he has been monitoring the situation in Baltimore. A team of investigators from the National Transportation Safety Board has been sent to the crash site.

Leon said he hopes what happened in Baltimore will cause port operations to change “quite a bit.” Pistorino said the event may lead legislators to take a closer look at vulnerable bridges in the country and the types of maritime traffic in ports.

“Just like the building collapse in South Florida created a lot of legislation that required a more intimate type of building scrutiny, I think that will happen on the bridges,” he said.

Minyvonne Burke is a senior breaking news reporter for NBC News.

Baltimore bridge collapse wasn't first major accident for giant container ship Dali

Propulsion failed on the cargo ship that struck the Francis Key Bridge in Baltimore early Tuesday as it was leaving port, causing it to collapse into the frigid Patapsco River. Its crew warned Maryland officials of a possible collision because they had lost control.

“The vessel notified MD Department of Transportation (MDOT) that they had lost control of the vessel” and a collision with the bridge “was possible,” according to an unclassified Department of Homeland Security report. “The vessel struck the bridge causing a complete collapse.”

An official speaking on condition of anonymity confirmed to USA TODAY that the DHS’ Cybersecurity and Infrastructure Security Agency is working with federal, state, and local officials “to understand the potential impacts of this morning’s collapse of the Francis Scott Key Bridge.”

Clay Diamond, executive director, American Pilots’ Association, told USA TODAY power issues are not unusual on cargo ships, which are so large they cannot easily course correct.

“It’s likely that virtually every pilot in the country has experienced a power loss of some kind (but) it generally is momentary,” Diamond said. “This was a complete blackout of all the power on the ship, so that’s unusual. Of course this happened at the worst possible location.”

The ship in Tuesday's crash, Dali, was involved in at least one prior accident when it collided with a shipping pier in Belgium.

That 2016 incident occurred as the Dali was leaving port in Antwerp and struck a loading pier made of stone, causing damage to the ship’s stern, according to VesselFinder.com, a site that tracks ships across the world. An investigation determined a mistake made by the ship’s master and pilot was to blame.

No one was injured in that crash, although the ship required repair and a full inspection before being returned to service. The pier – or berth – was also seriously damaged and had to be closed.

VesselFinder reports that the Dali was chartered by Maersk, the same company chartering it during the Baltimore harbor incident.

The 9-year-old container ship had passed previous inspections during its time at sea, but during one such inspection in June at the Port of San Antonio in Chile, officials discovered a deficiency with its "propulsion and auxiliary machinery (gauges, thermometers, etc)," according to the Tokyo MOU, an intergovernmental maritime authority in the Asia-Pacific region.

The report provided no other information about the deficiency except to note that it was not serious enough to remove the ship from service.

Follow here for live updates: Baltimore's Key Bridge collapses after ship strike; construction crew missing: Live Updates

Why did Dali crash into the Baltimore bridge?

Officials said Tuesday they’re investigating the collision, including whether systems on board lost electricity early Tuesday morning, which could be related to mechanical failure, according to a U.S. official who was not authorized to speak publicly.

Accidents at sea, known as marine casualties, are not uncommon, the source told USA TODAY. However, “allisions,” in which a moving object strikes a stationary one with catastrophic results, are far less common. The investigation of the power loss aboard the Dali, a Singapore-flagged vessel, will be a high priority.

In a video posted to social media, lights on the Dali shut off, then turned back on, then shut off again before the ship struck a support pier on the bridge.

Numerous cargo and cruise ships have lost power over the years.

The International Convention for the Safety of Life at Sea requires all international vessels to have two independent sources of electricity, both of which should be able to maintain the ship's seaworthiness on their own, according to a safety study about power failures on ships , citing the International Convention for the Safety of Life at Sea.

The Dali's emergency generator was likely responsible for the lights coming back on after the initial blackout, Diamond said.

“There was still some steerage left when they initially lost power,” he said. “We’ve been told the ship never recovered propulsion. The emergency generator is a diesel itself – so if you light off the generator, that’s also going to put off a puff of exhaust.”

Under maritime law, all foreign flagged vessels must be piloted into state ports by a state licensed pilot so the Dali's pilot is licensed by Association of Maryland Pilots .

Diamond described the incident based on information from the Maryland agency that licensed the pilot aboard the ship. His organization represents that group and all other state piloting agencies in the US.

“The pilot was directing navigation of the ship as it happened,” he said. “He asked the captain to get the engines back online. They weren’t able to do that, so the pilot took all the action he could. He tried to steer, to keep the ship in the channel. He also dropped the ship’s anchor to slow the ship and guide the direction.

“Neither one was enough. The ship never did regain its engine power.”

How big is the Dali ship?

The Dali is a 984-foot container vessel built in 2015 by Hyundai Heavy Industries in South Korea. With a cruising speed of about 22 knots – roughly 25 mph. It has traveled the world carrying goods from port to port.

The ship, constructed of high-strength steel, has one engine and one propeller, according to MarineTraffic.com.

The Dali arrived in Baltimore on Sunday from the Port of Norfolk in Virginia. Before that, it had been in New York and came through the Panama Canal.

It remains at the scene of the collapse as authorities investigate.

Who owns and operates the Dali?

It is owned by the Singapore-based Grace Ocean Pte Ltd but managed by Synergy Marine Group, also based in Singapore. It was carrying Maersk customers’ cargo, according to a statement from the shipping company.

“We are deeply concerned by this incident and are closely monitoring the situation,” Maersk said in the statement.

Synergy, which describes itself as a leading ship manager with more than 600 vessels under its guidance, issued a statement on its website acknowledging the incident and reporting no injuries among its crew and no pollution in the water. There were two pilots on board and 22 crew members in all, according to Synergy, all of them from India.

USA TODAY reached out to Synergy on Tuesday, but the company did not immediately return a call seeking comment.

Contributing: Josh Susong

What we know about the condition of Baltimore's Key Bridge before its collapse

B altimore's Francis Scott Key Bridge collapsed early Tuesday morning after one of its columns was hit by a large container ship. Video of the bridge shows it buckle and crash into the river below after the Dali, a massive 948-foot cargo ship, strikes it, sending vehicles and people into the river below. Six people were missing, and after a daylong search and rescue effort, the U.S. Coast Guard said Tuesday evening it was shifting to a recovery mission.

Here's what we know about the condition of the bridge and how this sort of collapse could happen.

During its latest federal inspection, the Key Bridge scored a six out of nine, which is considered "fair," a condition it had been labeled since 2008, CBS Baltimore reported .

The bridge passed inspection in May 2022, but there was concern with one of its columns. The reinforced concrete column was downgraded from a health index, or condition rating, of 77.8 to 65.9. It is not known whether the column of concern was the same one that was struck on Tuesday morning.

Ben Schafer, professor of civil and systems engineering at Johns Hopkins University, told CBS News that most bridges in the U.S. fall in this "fair" range, which is "not what we would want or suspect" as a society. But, he said, the massive ship — not the condition of the Key Bridge — is likely to blame for its collapse.

"Like others, I've watched the video a bunch of times and have gone frame by frame and worked up a few different hypothesis in my mind, but I see little evidence for anything other than: the boat strike took a bridge with two supports and took away one of them and then it fell in the water," Schafer told CBS News. "I mean, doesn't seem to be super more complicated than that."

Transportation Secretary Pete Buttigieg expressed a similar view at a briefing Tuesday afternoon. "This is a unique circumstance. I do not know of a bridge that has been constructed to withstand a direct impact from a vessel of this size. Anytime anything happens to any bridge, we as a country take that and learn from it," Buttigieg said.

Many bridges, whether a suspension bridge or an arched bridge, require two supports under the portion of bridge that goes over water, Schafer said. "This is the minimum number to cross over," he said.

"The container ship was as wide as it was as tall," Schafer said, adding that it was of similar scale to the bridge. "So the mass that's associated with that container ship creates an amount of energy that a small concrete pier isn't going to sustain. That's an accident that we can't allow to happen and expect the bridges to stay up."

Schafer said in the late 1800s, the Quebec Bridge, which had a similar design to Baltimore's Key Bridge, collapsed, which taught engineers many lessons about truss bridges. But by the 1970s when the Key Bridge was built, the design used was modern and sufficient.

Schafer said there is a lesson to be learned here, but it's likely not that changes to a bridge's design would help prevent an accident like this. He said the way shipping traffic is managed, or the size of container ships — which have likely increased since the 1970s when the bride was built — should be considered when trying to understand the risk of these types of accidents.

Robert Sumwalt, former chairman of the National Transportation Safety Board, told CBS News that the video of the accident holds some clues about what could have happened. The lights of the ship flashes off and on, which would indicated an electrical power failure, he said. Authorities confirmed the ship did lose power before the crash.

Black smoke is also seen coming out of the ship, which Sumwalt said likely means "ship's crew is trying to increase the RPMs across the propeller to increase the steering capability of it."

All of the crew members on the Dali were accounted for and there were no reports of any injuries among the crew. Sumwalt also said the ship's audio recording device likely captured conversations happening on the ship as well as other data like the angle of the rudder. "There will be a lot of information to help piece this back together," he said.

The four-lane Key Bridge is 1.6 miles long and was used by some 31,000 people a day, according CBS News Baltimore. Sumwalt said only two other tunnels cross the Patapsco River, so without the bridge, access will be limited.

A construction crew was filling potholes on the bridge at the time of the accident. Two workers were rescued from the water but six remained unaccounted for Tuesday night, officials said.

New details on Baltimore Key Bridge collapse, rescue efforts and more

The Dali was just starting a 27-day voyage.

The ship had spent two days in Baltimore’s port before setting off.

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The side of a large ship, painted blue, with the words “Dali” and “Singapore,” sitting at a port.

By Claire Moses and Jenny Gross

Published March 26, 2024 Updated March 27, 2024, 9:07 a.m. ET

The Dali was less than 30 minutes into its planned 27-day journey when the ship ran into the Francis Scott Key Bridge on Tuesday.

The ship, which was sailing under the Singaporean flag, was on its way to Sri Lanka and was supposed to arrive there on April 22, according to VesselFinder, a ship tracking website.

The Dali, which is nearly 1,000 feet long, left the Baltimore port around 1 a.m. Eastern on Tuesday. The ship had two pilots onboard, according to a statement by its owners, Grace Ocean Investment. There were 22 crew members on board, the Maritime & Port Authority of Singapore said in a statement. There were no reports of any injuries, Grace Ocean said.

Before heading off on its voyage, the Dali had returned to the United States from Panama on March 19, harboring in New York. It then arrived on Saturday in Baltimore, where it spent two days in the port.

Maersk, the shipping giant, said in a statement on Tuesday that it had chartered the vessel, which was carrying Maersk cargo. No Maersk crew and personnel were onboard, the statement said, adding that the company was monitoring the investigations being carried out by the authorities and by Synergy Group, the company that was operating the vessel.

“We are horrified by what has happened in Baltimore, and our thoughts are with all of those affected,” the Maersk statement said.

The Dali was built in 2015 by the South Korea-based Hyundai Heavy Industries. The following year, the ship was involved in a minor incident when it hit a stone wall at the port of Antwerp . The Dali sustained damage at the time, but no one was injured.

Claire Moses is a reporter for the Express desk in London. More about Claire Moses

Jenny Gross is a reporter for The Times in London covering breaking news and other topics. More about Jenny Gross

Pilot on board the Dali tried to slow ship before it struck Key Bridge

The specially trained pilot ordered the rudder turned hard to the left and an anchor drop to steady the ship and slow it down, an industry official said.

When a massive ship lost power on its way out of the Port of Baltimore and headed toward a major bridge, the pilot ordered its rudder turned hard to the left and its left anchor dropped in an effort to slow the vessel and stop it swinging to the right, according to the head of a national association for ship pilots.

The 985-foot container ship, known as the Dali, left Baltimore about 12:30 a.m. Tuesday, bound for Sri Lanka. Clay Diamond, the executive director of the American Pilots’ Association, said the ship experienced a “full blackout” around 1:20 a.m., meaning it lost both engine power and electrical power to the ship’s control and communications systems.

Baltimore bridge collapse

The ship was traveling at 8 knots, a normal speed for the area that Diamond described as “ahead slow.” The ship never regained engine power, but Diamond said a diesel backup generator did kick in, restoring the electrical systems — the possible source of a puff of black smoke visible in video of the collision circulating on social media.

Unable to slow the ship, Diamond said the pilot, who had more than a decade of experience, radioed an emergency message to have the Francis Scott Key Bridge closed. That mayday call has been credited with saving lives.

The huge vessel soon struck one of the bridge’s supports, causing it to crumple and crash down into the Patapsco River. Two members of a work crew on the bridge were rescued, but another six are presumed dead, the Coast Guard said. The collision led to the closure of the Baltimore port and leaves officials facing a massive cleanup and rebuilding job.

The 22 crew members on board the Dali all survived .

Who are the people presumed dead in the Baltimore bridge collapse?

Diamond said he had been in constant communication with the Association of Maryland Pilots on Tuesday and that the pilot on board had given a statement to investigators from the Coast Guard and the National Transportation Safety Board, which is leading the investigation into what went wrong. A second pilot aboard the Dali was an apprentice who had started his training last month, Diamond said.

Diamond said it is unusual for a ship to experience a total loss of power. “It’s not unheard of for a pilot to experience an engine casualty, it’s not that common to have a full blackout like this,” he said. “This is a complicated piece of equipment so it could be any number of causes.”

Foreign-flagged ships are required to have pilots aboard to guide them in and out of U.S. ports. Pilots have detailed knowledge of local shipping channels and complete an apprenticeship before becoming fully qualified. Diamond said they don’t take direct command of the vessel, but work with its crew to get it safely out to sea.

An earlier version of this article incorrectly identified the body of water into which the Key Bridge collapsed. It was the Patapsco River, not the Chesapeake Bay.

Baltimore’s Francis Scott Key Bridge collapsed after being hit by a cargo ship , sending at least eight people from a construction crew into the water. Two people were rescued and the remaining six are presumed dead, officials said. Follow live updates and see photos from the scene .

How it happened: The container ship lost power moments before colliding with the bridge, Maryland Gov. Wes Moore (D) said. Video shows the bridge collapse in under 40 seconds. Read everything we know about the bridge collapse .

Victims: All six missing victims are presumed dead, the U.S. Coast Guard said, and the agency has ended rescue efforts. The entire crew aboard the 985-foot container ship Dali survived . First responders shut down most traffic on the four-lane bridge after the crew issued an urgent “mayday.” It saved lives, Moore said.

Economic impact: The collapse of the bridge, which severed ocean links to the Port of Baltimore, adds a fresh headache to already struggling global supply chains . See how the collapse will disrupt the supply of cars, coal and tofu .

History: The Key Bridge was built in the 1970s and spans the Patapsco River. Here’s a list of other major bridge collapses in U.S. history , including Florida’s Sunshine Skyway Bridge

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4 Rudder Types for Sailboats
It is harder to move a full rudder than to move other types of rudders. Water flowing by the boat puts a great deal of pressure on a full keel rudder and makes the rudder hard to move. It takes a lot of force to push the rudder against the water moving past the boat. Spade rudders. Spade rudders are for fin keel boats rather than full keel boats.
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Components and mechanics of boat rudders. A typical boat rudder consists of several key components: Rudder blade: The rudder blade is the flat, vertical surface responsible for redirecting the water flow. It is the most critical part of the rudder and comes in various shapes and sizes. Rudder stock: The rudder stock is a sturdy vertical shaft ...
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A Becker Rudder is a type of spade rudder that has a moving flap at the trailing edge. The flap moves together with the main blade depending on the given rudder command. Due to the versatility of its flap, Becker Rudder can reach more than 65° without worrying about stalling or rudder drag. This results in a smaller turning circle and cost ...
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Types of Rudders For Ships. To broadly categorize conventional rudders, there are two types of ship rudders: 1. Spade or Balanced Rudder. A spade rudder is basically a rudder plate that is fixed to the rudder stock only at the top of the rudder. In other words, the rudder stock (or the axis of the rudder) doesn't run down along the span of ...
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The type of rudder is often related to the boat's type of keel. Rudder on Full-Keel Sailboat . As shown in this photo, the rudder of a full-keel boat is usually hinged to the aft edge of the keel, making a continuous surface. The engine's propeller is usually positioned in an aperture between the keel and rudder.
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The skeg rudder is similar to a spade keel and is fast. The skeg rudder's fore edge is protected by a "faux keel" that extends from aft of the hull. Hylas yachts are known for their skeg rudders. Outboard Rudder. Outboard rudders are used on smaller boats. They are attached to the transom of the boat, hanging off the stern.
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Keel-mounted rudders are attached to the boat's keel, which is the central structural element that runs along the bottom of the hull. Spade rudders are free-standing rudders that are not attached to any part of the boat and are commonly used in racing sailboats. The type of rudder used depends on the boat's size, design, and intended use ...
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The type of rudder and fitted to a yacht is often directly related to the type of keel which was covered in part 3 of this guide, and the type of steering is usually dictated by the size and position of the cockpit and space directly beneath or aft of it. As always, due to the huge variety of yachting pursuits, different rudder types work for ...
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2. Skeg- Mounted Rudder Skeg-hung or mounted rudders are supported in part by the ship's skeg, which is a vertical extension of the hull. The rudder is given more stability by this design, which makes underwater obstructions less likely to hurt it. Sailing yachts and some motorboats frequently employ skeg-hung rudders. 3. Balanced Rudder
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There are several types of rudders used on boats and ships, each with its advantages and disadvantages: 1-Balanced Rudder. A balanced rudder is a type of rudder used on boats and ships that are designed to reduce the force required to turn the rudder and improve steering efficiency.. A balanced rudder has a smaller surface area, which reduces the amount of water resistance and drag created by ...
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By far the most popular type are the spade rudders that are mounted on either stainless steel or aluminum (sometimes even aramid) stern-tube rudder stocks. In case of a failure emergency tillers can be quickly fitted to the top of the stocks. ... Drill holes in the stock for attaching to the rudder and boat. Attach the rudder stock: Use epoxy ...
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A skeg rudder is more modern in performance and safety. It is the most popular and common type of rudder on production boats these days. The rudder is fast and looks like a spade keel. Except, the skeg rudder has a fake keel which extends from the hulls aft and protects the fore edge. Most Hylas yachts have skeg rudders. Outboard
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The 20-knot semi-displacement lobster yacht's rudder I measured yielded an even 2.0 aspect ratio, which is considered respectable for this application. More identifiable rudder components include the stock; web or ... depending upon type, of many rudder designs. Because this component provides the primary connection between the rudder's ...
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Balanced rudders or spade rudder A rudder has 20-40% of the area forward of the stock, similarly there is no torque on the rudder stock at certain angles, this type of rudder is called balanced rudder. The axis of the rudder is placed near to the center of gravity, so torque required to move the rudder will be very less.
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Part of the reason our yachts are so easy to manoeuvre is rudder design, combined with the position of the propeller. A rudder needs to work well for both sailing and motoring, but many believe a rudder can only be good for sailing or motoring, not both. Most boatbuilders nowadays just focus on producing a rudder that's efficient for sailing ...
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Mb = 0.483m x 2,572 N = 1,242Nm. The torque on the rudder (Mt) was calculated by multiplying the lateral force by the separation between the shaft axis and the centre of pressure. For my rudder it worked out to be 2,572 x (0.41 x 0.33-0.10) = 91Nm; roughly 10kg.
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The difference between a faired rudder with a polished finish and a rudder carrying a 10-year accumulation of rolled-on antifouling paint can be as much is 35 percent (see "Rudder Savvy to Boost Boat Performance," above). What can we do? If your rudder is a lift up type, don't use bottom paint.
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How a cargo ship took down Baltimore's Key Bridge
The rudder may have gotten stuck in a position that caused the ship to turn, said a senior retired maritime official, who spoke on background while waiting for more details on the incident.
Why Baltimore's Key Bridge couldn't withstand a cargo ship crash
The Francis Scott Key Bridge, a roughly 1.5-mile-long steel arch truss bridge, collapsed into the Patapsco River early Tuesday after a containership struck it. Several vehicles crashed into the ...
Dali ship that caused Baltimore bridge collapse was in prior accident
The ship in Tuesday's crash, Dali, was involved in at least one prior accident when it collided with a shipping pier in Belgium. That 2016 incident occurred as the Dali was leaving port in Antwerp ...
What we know about the condition of Baltimore's Key Bridge before ...
Sumwalt also said the ship's audio recording device likely captured conversations happening on the ship as well as other data like the angle of the rudder. "There will be a lot of information to ...
Dali Ship That Hit Key Bridge Was Destined for Sri Lanka
March 26, 2024 Updated 1:50 p.m. ET. The Dali was less than 30 minutes into its planned 27-day journey when the ship ran into the Francis Scott Key Bridge on Tuesday. The ship, which was sailing ...
Ship's pilot tried to avoid Baltimore Key Bridge before crash, collapse
The specially trained pilot ordered rudder turned hard to the left and an anchor drop to steady the ship and slow it down, an industry official said. By Ian Duncan March 26, 2024 at 8:49 p.m. EDT

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The Types of Sailboat Rudders

Full Keel Rudder

Rudder on Full-Keel Sailboat

Advantages of Full Keel Rudder

Disadvantage of Full Keel Rudder

Spade Rudder

Advantages of Spade Rudder

Disadvantage of Spade Rudder

Balanced Spade Rudder

Skeg-Mounted Rudder

Outboard Rudder

Advantages of Outboard Rudder

Disadvantages of Outboard Rudder

Four Types of Rudders On Sailboats

Full Rudder

Spade Rudder

Skeg Rudder

Outboard Rudder

Choosing a Blue Water Yacht – Rudder Type

Steering Systems

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