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CRUNCHING NUMBERS: Brewer Comfort Ratio

Most racing sailors aren’t very concerned about this. Indeed, if you read some accounts of modern long-distance races and record attempts, it seems they pride themselves on sailing aboard the most uncomfortable boats imaginable. The motion aboard some extreme sailboats can be so violent that crew members must wear helmets while sleeping in case their heads are smashed against bulkheads or ceilings while they lie in their berths.

Smart cruisers, on the other hand, are very interested in a boat’s motion and how it affects comfort aboard. Cruisers, like all sailors, are happy when sailing fast. But they are happiest when they are physically comfortable. Even short of getting seasick, this is the one factor that normally has the biggest influence on a cruiser’s sense of psychological well-being.

It isn’t really possible to quantify all aspects of a boat’s motion in a single numerical parameter. But there is a relatively simple so-called “comfort ratio,” developed by designer Ted Brewer , that does provide a reasonable indication of what a boat’s motion will be like in certain conditions. Though originally developed by Brewer somewhat in jest, it is now accepted by many as the best way to evaluate motion comfort using commonly published boat specifications. Unfortunately, the comfort ratio is rarely mentioned in magazine boat tests and is never published by boatbuilders. It’s easy, however, to figure it out on your own, and I urge you to use it when analyzing cruising boats, particularly bluewater cruising boats. It provides a much needed third dimension to complement the simplistic two-dimensional picture painted by the D/L and SA/D ratios.

To calculate Brewer’s comfort ratio, you need to run the following formula: Comfort ratio = D ÷ (.65 x (.7 LWL + .3 LOA) x Beam↑1.33), where displacement is expressed in pounds, and length is expressed in feet.

As an example, let’s again consider a hypothetical 12,000-pound boat with a load waterline length of 28 feet. Let’s assume it also has a length overall of 35 feet, and a beam of 11 feet. Therefore, to find its comfort factor, we first need to multiply its LWL by .7 (.7 x 28 = 19.6) and its LOA by .3 (.3 x 35 = 10.5) and should then add these two results together, which gives us 30.1 (19.6 + 10.5 = 30.1). Next take the boat’s beam to the 1.33 power, which gives us 24.27 (11↑1.33 = 24.27), and multiply this result and the previous result by .65, which gives us 474.84 (.65 x 30.1 x 24.27 = 474.84). Finally, divide this result into the boat’s displacement, which yields a comfort ratio of 25.27 (12,000 ÷ 474.84 = 25.27).

What the formula purports to assess is how quickly and abruptly a boat’s hull reacts to waves in a significant seaway, these being the elements of a boat’s motion most likely to cause seasickness. The formula favors heavier boats over lighter boats, as more weight always helps to dampen a boat’s motion, and also favors boats with smaller waterplanes. This refers to the horizontal plane on a boat’s waterline and is generally a function of length and beam. Boats that weigh less and have more waterplane tend to have a quicker motion, because more waterplane means there’s more area for waves to push up against and less weight means there’s less resistance to the pushing.

Longer boats obviously have larger waterplanes than shorter boats, but the exponential increase in their displacement always negates this. As a result, the comfort-ratio formula also favors length, though it penalizes beam. Generally, it favors heavy boats with overhangs and narrow beam, but longer boats may have considerably lower D/L ratios than shorter ones and still fare much better by comparison.

You can use the following guidelines to interpret comfort ratio results: numbers below 20 indicate a lightweight racing boat; 20 to 30 indicates a coastal cruiser; 30 to 40 indicates a moderate bluewater cruising boat; 50 to 60 indicates a heavy bluewater boat; and over 60 indicates an extremely heavy bluewater boat. If evaluating a larger boat, say 45 feet or longer, expect your results to be skewed a bit higher on this scale; if the boat is quite small, say 25 feet or less, they will be skewed slightly downwards.

Once again, increasing displacement to account for loads carried seriously affects results. Our hypothetical 12,000-pound boat, with its comfort ratio of 25.27, becomes decidedly more comfortable as we load it to cruise. Add on another 2,500 pounds for light coastal cruising, and the ratio rises to 30.5; make that an extra 3,750 pounds for bluewater cruising, and it becomes 33.16.

Limitations/Multihulls

What the comfort ratio does not assess is how comfortable a boat seems in relatively flat water. In these conditions it is normally a boat’s heeling that makes folks feel uncomfortable. The best way to make a boat stiffer and decrease heeling is to increase its beam, which, ironically, is one the things that will make it less comfortable in a strong seaway. Conversely, a narrow boat that heels easily may seem more comfortable in a seaway, but less comfortable, compared to a beamier boat, when sailing well in flat water.

Another factor the comfort ratio does not account for is ballast location. This is not often remarked upon, but I’ve found the closer you are to a boat’s ballast the more comfortable you tend to be. Presumably this is because ballast normally represents the greatest concentration of weight on a boat, so has a dampening effect on motion. Also, the heaviest part of the boat tends to be the fulcrum around which it revolves in rough conditions. The less distance there is between you and the fulcrum, the less motion you will experience.

On most modern boats with ballast keels this effect won’t really come into play. It will be noticeable, however, on some older wooden boats that carry some ballast in their bilges; even more so on certain modern centerboard boats that have no keels at all and carry all their ballast in their bilges. Boats like this, in my experience, are much more comfortable than their comfort ratios suggest.

The comfort ratio also does not pertain to multihulls. Because these boats carry no ballast at all and rely entirely on beam for their stability, their motion is entirely different from monohulls. Many cruisers are attracted to catamarans for precisely this reason. Because cruising catamarans normally do not heel, they are perceived by many as being more comfortable than monohulls.

This is true as far as it goes, but don’t assume that a catamaran’s motion in large seas is ever negligible. A monohull may experience more total motion in a strong seaway than a catamaran, primarily because it rolls more from side to side. Like the cat it will also be heaving up and down. But the motion of the monohull will usually have a distinct rhythm to it. If the seas are not absolutely confused and have some pattern to them, that pattern will be reflected in the motion of the boat. Those onboard can learn the pattern and anticipate it. The motion, because it is not random, is easier to adapt to.

This is not the case with catamarans. Catamarans not only have two hulls in the water, each reacting to separate sets of waves, they also have a bridgedeck connecting the hulls, which is struck by the irregular waves that heap up between the hulls at irregular intervals. A catamaran thus receives input from three different sets of waves. Its aggregate motion, as a result, often has no rhythm to it.

Because it has no ballast and is light for its size, a cat’s motion is also fast and abrupt. The total effect in a seaway is quick, quirky, random, and harder to anticipate and adapt to. Some sailors aren’t bothered by this and are happy to live with it in exchange for not heeling. Others, however, prefer to deal with the slower, more predictable, albeit somewhat more exaggerated motion of a monohull, and will take their heeling as they find it.

HANSTAIGER X1: The Trimaran To End All Trimarans

JAMES WHARRAM: His New Autobiography

Hi Charlie,

You may want to put in a link to US Sailing’s “Motion Comfort Calculator”

http://www.sailingusa.info/motion_comfort.htm

It make running the numbers a little easier.

Response to Ken below: Thanks! What a cool resource. I see they have calculators for the various other formulae I’ve discussed in these Crunching Numbers posts. I’ll have to add several links! charlie

I little late to when you posted but even more important now with lots of fat bottom boats being pushed. I laugh at the boats being advertised ocean boats. Can you speak to the reverse now ( negative bouyancy rate on dropping bow), wide sterns pushing down the bows on any heal angle encouraging slipping and plowing. I’d love to see a comparison of rocking motion, acceleration of boats about their rotation point. Rotation point being center of bouyancy and CG. Rocking motion then plotting angle vs volume. Add in wave shape and that wide stern prevents the bow from rising in a gradual motion. And small volume bows have very little restoring volume until the boat is immersed half way to the mast…..

Response to Ken below: Thanks!

You’re welcome. And thank you for the interesting and informative articles. And yes, I have your book… I bought it last year while we were trying to make up our minds about what boat we were going to purchase. It helped the process.

Hi, For people living on the SI-side of the universe, formula can be used with SI units too, just replace the 0.65 by 4.697 … enter length and beam in m, displacement in kg. best rgds, vic

Great post, I am copying it, placing in my research.

On factor overlooked is the effect of heavy displacement, particularly in the ends of the vessel, when encountering waves from ahead of the beam. A light boat will more quickly and abruptly react to the waves, and will ride over them and this is thought to be a less comfortable motion than that of a heavier boat. On the other hand, and not acknowledged by this formula, is what happens to that heavier yacht which does NOT ride over the waves but plows directly into them. Given a bigger wave the heavier yacht, (with weight in the ends it is worse) plunges deep into the wave, throwing tons of water to each side, and it’s forward progress is dramatically slowed. Next buoyancy comes into play and this boat, with it’s bow deep into the wave face, and nearly stopped, begins to rise, quickly. As the crest passes under the hull the bow will arch skyward, then plunge dramatically into the next wave. Two waves in a row like the and the boat can be totally stopped.

I’ve sailed on both types of boats and without a doubt, I prefer the jarring, jerky ride of a boat going over the waves, (BUT GOING), over the hobby horsing heavyweight which plunges deeply into each wave and cannot maintain headway in a seaway.

Ted Brewer’s comfort index is great for the armchair sailor but does not hold up when you got to sea and you encounter big waves coming from the direction you want to go.

Thank you for breaking this down in a way that even a beginning cruiser-to-be can understand, yet retaining the level of sophistication necessary to explain some important maritime concepts.

Clear and well written. I can see the variables of the comment above. A heavier boat digging in creating a stop and go motion compared to a boat that has a lower comfort ratio floating like a cork over the waves continuing forward … this is another scenario which is impacted by how big and closely spaced the waves are…it’s not as clear as the armchair formula that gives a general rating for a particular model boat. The formula makes sense and I can see how it compares to my previous boats. What brought me to this article is comparing numbers on 3 sailboats and this comfort ratio makes sense to me.

Bethwaite’s books explain it perfectly. A deep keel boat’s motion in a seaway is more solidly hooked in underwater while a multihull, is skittering over the waves in general.

I’ve been on both in a seaway and it’s a tossup, lots of water on deck and a labored movement with a deep keeled monohull, vs. flying over the water on a multihull at speed ’till you hit the wrong wave set & risk capsizing the boat. Modern fin keeled monohulls are stiff & uncomfortable but always keep the mast pointing upward. The same cannot be said about performance multihulls where an “oops we’re capsizing” event is always possible.

The 40-50 range is missing. “…numbers below 20 indicate a lightweight racing boat; 20 to 30 indicates a coastal cruiser; 30 to 40 indicates a moderate bluewater cruising boat; 50 to 60 indicates a heavy bluewater boat; and over 60 indicates an extremely heavy bluewater boat.”

Thank you for this informative article! I wonder how this concept plays into the concept of heaving to in rough seas, as explained really well by Lin and Larry Pardis in their book, “The Capable Cruiser”. In this regard, they strongly endorse more heavier displaced boats with heavy full keel hulls to heave to in heavy weather, thereby creating a slick behind the boat that breaks the waves in advance of reaching the hull.

They maintain that as opposed to running before a storm, you should heave to and let it pass over while safe behind your slick, losing about 1.5-2 knots as the storm rolls over. Those who try to outrun a storm often elongate their being in the mess, versus those who ride it out. Of course, being highly skilled at it is essential, as failing to properly hove to leaves one vulnerable to building and sometimes very dangerous sea conditions.

They suggest that being able to hove to in bad weather is necessary in elongated lee shores, so I’m curious if this comfort ratio is pertinent if a sailor knows these tactics, and/or if the ratio is descriptive of the vessel’s capability in this regard. I’d enjoy hearing your thoughts on it. Certain keels cannot heave to very well and cats certainly are unable to create a slick without ample displacement.

In general, modern monohulls with fin keels and spade rudders have significant yawing moments around those keels and don’t heave-to particularly well. Theoretically they should either lie to a sea anchor, or run +/- a drouge.

Hi! As an engineer of automobiles, I kind of thinking on the comfort ratio and heeling as effect of mass inertia. For example if you put a lot of loads at front/rear you will get a considerably high Iy mass inertia (Iz is about the same as Iy). For heeling it about Ix which can be affected by make the boat wider or with a person on side.

The 30 most “comfortable” sailboats

The Comfort Ratio is as a measure of motion comfort. Ted Brewer dreamed up the comfort ratio tongue-in-cheek, but it has been widely accepted and, indeed, does provide a reasonable comparison between yachts of similar type.

From tedbrewer.com :

It is based on the fact that the faster the motion the more upsetting it is to the average person. Given a wave of X height, the speed of the upward motion depends on the displacement of the yacht and the amount of waterline area that is acted upon. Greater displacement, or lesser WL area, gives a slower motion and more comfort for any given sea state. Beam does enter into it as as wider beam increases stability, increases WL area, and generates a faster reaction. The formula takes into account the displacement, the WL area, and adds a beam factor. The intention is to provide a means to compare the motion comfort of vessels of similar type and size, not to compare that of a Lightning class sloop with that of a husky 50 foot ketch. The CR is : Displacement in pounds/ (.65 x (.7 LWL + .3 LOA) x B1.333). Ratios will vary from 5.0 for a light daysailer to the high 60s for a super heavy vessel, such as a Colin Archer ketch. Moderate and successful ocean cruisers, such as the Valiant 40 and Whitby 42, will fall into the low-middle 30s range. Do consider, though, that a sailing yacht heeled by a good breeze will have a much steadier motion than one bobbing up and down in light airs on left over swells from yesterday’s blow; also that the typical summertime coastal cruiser will rarely encounter the wind and seas that an ocean going yacht will meet. Nor will one human stomach keep down what another stomach will handle with relish, or with mustard and pickles for that matter! It is all relative.

These 30 sailboats have the highest Comfort Ratio of all known sailboats.

Eastwind 44

Mayflower 1620.

Belfast Lough One-Design (Class I)

Seawanhaka schooner.

Belfast Lough One-Design (Class II)

Clyde 20-Ton One-Design

Jongert 20s.

Nicholson 70

Controversy 30, little harbor 62.

Bar Harbor 31

Concorde 151

Jongert 21s.

Solent One-Design

Viking 30 (Buchanan)

West solent one-design, new york yacht club 50.

Hinckley Sou'wester 59

Little harbor 54.

Dolphin 47 (Alden)

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How a Sail Works: Basic Aerodynamics

The more you learn about how a sail works, the more you start to really appreciate the fundamental structure and design used for all sailboats.

It can be truly fascinating that many years ago, adventurers sailed the oceans and seas with what we consider now to be basic aerodynamic and hydrodynamic theory.

When I first heard the words “aerodynamic and hydrodynamic theory” when being introduced to how a sail works in its most fundamental form, I was a bit intimidated.

“Do I need to take a physics 101 course?” However, it turns out it can be explained in very intuitive ways that anyone with a touch of curiosity can learn.

Wherever possible, I’ll include not only intuitive descriptions of the basic aerodynamics of how a sail works, but I’ll also include images to illustrate these points.

There are a lot of fascinating facts to learn, so let’s get to it!

Basic Aerodynamic Theory and Sailing

Combining the world of aerodynamics and sailing is a natural move thanks to the combination of wind and sail.

We all know that sailboats get their forward motion from wind energy, so it’s no wonder a little bit of understanding of aerodynamics is in order. Aerodynamics is a field of study focused on the motion of air when it interacts with a solid object.

The most common image that comes to mind is wind on an airplane or a car in a wind tunnel. As a matter of fact, the sail on a sailboat acts a bit like a wing under specific points of sail as does the keel underneath a sailboat.

People have been using the fundamentals of aerodynamics to sail around the globe for thousands of years.

The ancient Greeks are known to have had at least an intuitive understanding of it an extremely long time ago. However, it wasn’t truly laid out as science until Sir Isaac Newton came along in 1726 with his theory of air resistance.

Fundamental Forces

One of the most important facets to understand when learning about how a sail works under the magnifying glass of aerodynamics is understanding the forces at play.

There are four fundamental forces involved in the combination of aerodynamics and a sailboat and those include the lift, drag, thrust, and weight.

From the image above, you can see these forces at play on an airfoil, which is just like a wing on an airplane or similar to the many types of sails on a sailboat. They all have an important role to play in how a sail works when out on the water with a bit of wind about, but the two main aerodynamic forces are lift and drag.

Before we jump into how lift and drag work, let’s take a quick look at thrust and weight since understanding these will give us a better view of the aerodynamics of a sailboat.

As you can imagine, weight is a pretty straight forward force since it’s simply how heavy an object is.

The weight of a sailboat makes a huge difference in how it’s able to accelerate when a more powerful wind kicks in as well as when changing directions while tacking or jibing.

It’s also the opposing force to lift, which is where the keel comes in mighty handy. More on that later.

The thrust force is a reactionary force as it’s the main result of the combination of all the other forces. This is the force that helps propel a sailboat forward while in the water, which is essentially the acceleration of a sailboat cutting through the water.

Combine this forward acceleration with the weight of sailboat and you get Newton’s famous second law of motion F=ma.

Drag and Lift

Now for the more interesting aerodynamic forces at play when looking at how a sail works. As I mentioned before, lift and drag are the two main aerodynamic forces involved in this scientific dance between wind and sail.

Just like the image shows, they are perpendicular forces that play crucial roles in getting a sailboat moving along.

If you were to combine the lift and drag force together, you would end up with a force that’s directly trying to tip your sailboat.

What the sail is essentially doing is breaking up the force of the wind into two components that serve different purposes. This decomposition of forces is what makes a sailboat a sailboat.

The drag force is the force parallel to the sail, which is essentially the force that’s altering the direction of the wind and pushing the sailboat sideways.

The reason drag is occurring in the first place is based on the positioning of the sail to the wind. Since we want our sail to catch the wind, it’s only natural this force will be produced.

The lift force is the force perpendicular to the sail and provides the energy that’s pointed fore the sailboat. Since the lift force is pointing forward, we want to ensure our sailboat is able to use as much of that force to produce forward propulsion.

This is exactly the energy our sailboat needs to get moving, so figuring out how to eliminate any other force that impedes it is essential.

Combining the lift and drag forces produces a very strong force that’s exactly perpendicular to the hull of a sailboat.

As you might have already experienced while out on a sailing adventure, the sailboat heels (tips) when the wind starts moving, which is exactly this strong perpendicular force produced by the lift and drag.

Now, you may be wondering “Why doesn’t the sailboat get pushed in this new direction due to this new force?” Well, if we only had the hull and sail to work with while out on the water, we’d definitely be out of luck.

There’s no question we’d just be pushed to the side and never move forward. However, sailboats have a special trick up their sleeves that help transform that energy to a force pointing forward.

Hydrodynamics: The Role of the Keel

An essential part of any monohull sailboat is a keel, which is the long, heavy object that protrudes from the hull and down to the seabed. Keels can come in many types , but they all serve the same purpose regardless of their shape and size.

Hydrodynamics, or fluid dynamics, is similar to aerodynamics in the sense that it describes the flow of fluids and is often used as a way to model how liquids in motion interact with solid objects.

As a matter of fact, one of the most famous math problems that have yet to be solved is exactly addressing this interaction, which is called the Navier-Stokes equations. If you can solve this math problem, the Clay Mathematics Institute will award you with $1 million!

There are a couple of reasons why a sailboat has a keel . A keel converts sideways force on the sailboat by the wind into forward motion and it provides ballast (i.e., keeps the sailboat from tipping).

By canceling out the perpendicular force on the sailboat originally caused by the wind hitting the sail, the only significant leftover force produces forward motion.

We talked about how the sideways force makes the sailboat tip to the side. Well, the keep is made out to be a wing-like object that can not only effectively cut through the water below, but also provide enough surface area to resist being moved.

For example, if you stick your hand in water and keep it stiff while moving it back and forth in the direction of your palm, your hand is producing a lot of resistance to the water.

This resisting force by the keel contributes to eliminating that perpendicular force that’s trying to tip the sailboat as hard as it can.

The wind hitting the sail and thus producing that sideways force is being pushed back by this big, heavy object in the water. Since that big, heavy object isn’t easy to push around, a lot of that energy gets canceled out.

When the energy perpendicular to the sailboat is effectively canceled out, the only remaining force is the remnants of the lift force. And since the lift force was pointing parallel to the sailboat as well as the hull, there’s only one way to go: forward!

Once the forward motion starts to occur, the keel starts to act like a wing and helps to stabilize the sailboat as the speed increases.

This is when the keel is able to resist the perpendicular force even more, resulting in the sailboat evening out.

This is exactly why once you pick up a bit of speed after experiencing a gust, your sailboat will tend to flatten instead of stay tipped over so heavily.

Heeling Over

When you’re on a sailboat and you experience the feeling of the sailboat tipping to either the port or starboard side, that’s called heeling .

As your sailboat catches the wind in its sail and works with the keel to produce forward motion, that heeling over will be reduced due to the wing-like nature of the keel.

The combination of the perpendicular force of the wind on the sail and the opposing force by the keel results in these forces canceling out.

However, the keel isn’t able to overpower the force by the wind absolutely which results in the sailboat traveling forward with a little tilt, or heel, to it.

Ideally, you want your sailboat to heel as little as possible because this allows your sailboat to cut through the water easier and to transfer more energy forward.

This is why you see sailboat racing crews leaning on the side of their sailboat that’s heeled over the most. They’re trying to help the keel by adding even more force against the perpendicular wind force.

By leveling out the sailboat, you’ll be able to move through the water far more efficiently. This means that any work in correcting the heeling of your sailboat beyond the work of the keel needs to be done by you and your crew.

Apart from the racing crews that lean intensely on one side of the sailboat, there are other ways to do this as well.

One way to prevent your sailboat from heeling over is to simply move your crew from one side of the sailboat to the other. Just like racing sailors, you’re helping out the keel resist the perpendicular force without having to do any intense harness gymnastics.

A great way to properly keep your sailboat from heeling over is to adjust the sails on your sailboat. Sure, it’s fun to sail around with a little heel because it adds a bit of action to the day, but if you need to contain that action a bit all you need to do is ease out the sails.

By easing out the sails, you’re reducing the surface area of the sail acting on the wind and thus reducing the perpendicular wind force. Be sure to ease it out carefully though so as to avoid luffing.

Another great way to reduce heeling on your sailboat is to reef your sails. By reefing your sails, you’re again reducing the surface area of the sails acting on the wind.

However, in this case the reduction of surface area doesn’t require altering your current point of sail and instead simply remove surface area altogether.

When the winds are high and mighty, and they don’t appear to be letting up, reefing your sails is always a smart move.

How an Airplane Wing Works

We talked a lot about how a sail is a wing-like object, but I always find it important to be able to understand one concept in a number of different ways.

Probably the most common example’s of how aerodynamics works is with wings on an airplane. If you can understand how a sail works as well as a wing on an airplane, you’ll be in a small minority of people who truly understand the basic aerodynamic theory.

As I mentioned before, sails on a sailboat are similar to wings on an airplane. When wind streams across a wing, some air travels above the wing and some below.

The air that travels above the wing travels a longer distance, which means it has to travel at a higher velocity than the air below resulting in a lower pressure environment.

On the other hand, the air that passes below the wing doesn’t have to travel as far as the air on top of the wing, so the air can travel at a lower velocity than the air above resulting in a higher pressure environment.

Now, it’s a fact that high-pressure systems always move toward low-pressure systems since this is a transfer of energy from a higher potential to a lower potential.

Think of what happens when you open the bathroom door after taking a hot shower. All that hot air escapes into a cooler environment as fast as possible.

Due to the shape of a wing on an airplane, a pressure differential is created and results in the high pressure wanting to move to the lower pressure.

This resulting pressure dynamic forces the wing to move upward causing whatever else is attached to it to rise up as well. This is how airplanes are able to produce lift and raise themselves off the ground.

Now if you look at this in the eyes of a sailboat, the sail is acting in a similar way. Wind is streaming across the sail head on resulting in some air going on the port side and the starboard side of the sail.

Whichever side of the sail is puffed out will require the air to travel a bit farther than the interior part of the sail.

This is actually where there’s a slight difference between a wing and a sail since both sides of the sail are equal in length.

However, all of the air on the interior doesn’t have to travel the same distance as all of the air on the exterior, which results in the pressure differential we see with wings.

Final Thoughts

We got pretty technical here today, but I hope it was helpful in deepening your understanding of how a sail works as well as how a keel works when it comes to basic aerodynamic and hydrodynamic theory.

Having this knowledge is helpful when adjusting your sails and being conscious of the power of the wind on your sailboat.

With a better fundamental background in how a sailboat operates and how their interconnected parts work together in terms of basic aerodynamics and hydrodynamics, you’re definitely better fit for cruising out on the water.

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An Introduction to the Physics of Sailing English

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This lesson is CPALMS Vetted and Approved

Instructors.

Emma Ferris Masters of Mechanical Engineering at MIT Officer, The United States Navy

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Introduction.

The goal of this lesson is to explain how sailboats work by exploring basic physics principles. At the end of this lesson, students will be able to identify the forces acting on a sailboat and explain how the combination of these forces results in the forward motion of a sailboat. Students should be familiar with vectors and be able to use them to represent forces and moments, and also should be familiar with using free body diagrams to represent forces and moments. A basic understanding of fluid flow and/or resistance might be helpful, but not necessary. This lesson and the follow-on assessment will each take about one hour to complete. Students only need pen/pencil and paper to complete the activities in the lesson, although an optional activity where students make their own sailboats would require additional materials. The classroom activity challenges are centered around small-group discussions based on the questions posed before each break. Free body diagrams, or another conceptual representation of his or her answer, should support each student’s solution to the questions posed in the video. Instructions for the option of having students design their own sailboats as part of this lesson can be found here: https://tryengineering.org/teacher/sail-away/

Attention : It has been pointed out to us that certain experts disagree with the explanation for the generation of lift presented in this video lesson. For this reason, we would like to refer teachers to the following articles which present an alternative explanation:

http://www.gentrysailing.com/pdf-theory/How-a-Sail-Gives-Lift.pdf

https://www.northsails.com/sailing/en/art-science-sails/gentry

Instructor Biography

Emma started sailing at a young age and eventually taught sailing and sailed competitively in college at the United States Naval Academy.. Her passion for sailing and the ocean led her to study Naval Architecture (ship design) as an undergraduate, and she went on to pursue a Masters in Mechanical Engineering at MIT, with a focus on Ocean Engineering. She currently serves as an officer in the United States Navy.

For Teachers

Teacher Guide (PDF)
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Additional Online Resources

The Physics Classroom: Drawing Free-Body Diagrams This site, sponsored by the Physics Classroom, provides instructions on drawing free body diagrams, as well as practice situations for applying those instructions.

The Physics Classroom: Vectors and Direction Also sponsored by the Physics Classroom, this site provides an introduction to the fundamentals of vectors and directions.

The Physics Classroom: Relative Velocity and Riverboat Problems Again from the Physics Classroom, this is a discussion of vectors and relative velocity.

The Physics Classroom: Addition of Forces Again from the same hosting site, here you will find an introduction to forces and vectors in two dimensions and the addition of those forces.

University of Cambridge: How wings really work Developed by the University of Cambridge in England, this short video demonstrates how lift is created by air flowing over a wing.

Live Science: What Is Fluid Dynamics? This article by Live Science is an introduction to Fluid Dynamics.

Real World Physics Problems: The Physics of Sailing Sponsored by Real World Physics Problems, this site provides a comprehensive overview of the physics of sailing.

YouTube: The Physics of Sailing This is an excellent video on sailing produced by KQED in San Francisco.

National Sailing Hall of Fame: Introducing STEM Sailing Best Practices This site, sponsored by the National Sailing Hall of Fame, introduces two hands-on activities students can do to study the science of sailing.

Resistive forces

Predicting speed, the physics of sailing.

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Bryon D. Anderson; The physics of sailing. Physics Today 1 February 2008; 61 (2): 38–43. https://doi.org/10.1063/1.2883908

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In addition to the recreational pleasure sailing affords, it involves some interesting physics. Sailing starts with the force of the wind on the sails. Analyzing that interaction yields some results not commonly known to non-sailors. It turns out, for example, that downwind is not the fastest direction for sailing. And there are aerodynamic issues. Sails and keels work by providing “lift” from the fluid passing around them. So optimizing keel and wing shapes involves wing theory.

The resistance experienced by a moving sailboat includes the effects of waves, eddies, and turbulence in the water, and of the vortices produced in air by the sails. To reduce resistance effectively by optimizing hulls, keels, and sails, one has to understand its various components.

Moving air has kinetic energy that can, through its interaction with the sails, be used to propel a sailboat. Like airplane wings, sails exploit Bernoulli’s principle. An airplane wing is designed to cause the air moving over its top to move faster than the air moving along its undersurface. That results in lower pressure above the wing than below it. The pressure difference generates the lift provided by the wing.

There is much discussion of whether the pressure difference arises entirely from the Bernoulli effect or partly from the wing’s impact and redirection of the air. Classic wing theory attributes all the lift to the Bernoulli effect and ascribes the difference in wind speeds above and below the wing to the wing’s asymmetric cross-sectional shape, which caused the path on top to be longer. But it’s well known that an up–down symmetrical wing can provide lift simply by moving through the air with an upward tilt, called the angle of attack. Then, despite the wing’s symmetry, the wind still experiences a longer path and thus greater speed over the top of the wing than under its bottom. A NASA website has an excellent discussion of the various contributions to lift by an airplane wing. 1 It disputes the conventional simple version of wing theory and emphasizes that lift is produced by the turning of the fluid flow.

The case is similar for sailboats. A sail is almost always curved and presented to the wind at an angle of attack. The situation is shown schematically in figure 1(a) . The wind moving around the “upper,” or downwind, side of the sail is forced to take the longer path. So the presence of the surrounding moving air makes it move faster than the air passing along the “lower,” or upwind, side of the sail. Measurements confirm that relative to the air pressure far from the sail, the pressure is higher on the upwind side and lower on the downwind side.

Figure 1. Forces on a moving sailboat. (a) Sail and keel produce horizontal “lift” forces due to pressure differences from different wind and water speeds, respectively, on opposite surfaces. (b) The vector sum of lift forces from sail and keel forces determines the boat’s direction of motion (assuming there’s no rudder). When boat speed and course are constant, the net lift force is precisely balanced by the velocity-dependent drag force on the boat as it plows through water and air.

For downwind sailing, with the sail oriented perpendicular to the wind direction, the pressure increase on the upwind side is greater than the pressure decrease on the downwind side. As one turns the boat more and more into the direction from which the wind is coming, those differences reverse, so that with the wind perpendicular to the motion of the boat, the pressure decrease on the downwind side is greater than the pressure increase on the upwind side. For a boat sailing almost directly into the wind, the pressure decrease on the downwind side is much greater than the increase on the upwind side.

Experimenting with what can be done, a beginner finds some surprising results. Sailors know well that the fastest point of sail (the boat’s direction of motion with respect to the wind direction) is not directly downwind. Sailboats move fastest when the boat is moving with the wind coming “abeam” (from the side). That’s easily understood: When a sailboat is moving directly downwind, it can never move faster than the wind because, at the wind speed, the sails would feel no wind. In fact, a boat going downwind can never attain the wind speed because there’s always some resistance to its motion through the water.

But when the boat is moving perpendicular to the wind, the boat’s speed doesn’t decrease the force of the wind on the sails. One sets the sails at about 45° to the direction of motion—and to the wind. The boat’s equilibrium speed is determined by the roughly constant force of the wind in the sails and the resistance against the boat’s motion through the water. If the resistance can be made small, the velocity can be large. That’s seen most dramatically for sail iceboats, which skate on the ice with very little resistance. They can glide along at speeds in excess of 150 km/h with the wind abeam at speeds of only 50 km/h! Of course sailboats plowing through the water experience much more resistance. Nonetheless, some specially constructed sailboats have attained speeds of more than twice the wind speed.

It was recognized centuries ago that a sailboat needs something to help it move in the direction in which it’s pointed rather than just drifting downwind. The answer was the keel. Until the development of modern wing theory, it was thought that one needed a long, deep keel to prevent side-slipping. But now it’s understood that a keel, like a sail, works by providing sideways lift as the water flows around it, as shown in figure 1(a) . A keel must be symmetrical for the sailboat to move to either side of the wind.

A keel works only if the motion of the boat is not exactly in the direction in which it’s pointed. The boat must be moving somewhat sideways. In that “crabbing” motion, the keel moves through the water with an angle of attack. Just as for the sails in the wind, that causes the water on the “high” (more downstream) side of the keel to move faster and create a lower pressure. Again, the net lift force on the keel is due to the combination of that decreased pressure on the high side and increased pressure on the other (low) side.

In figure 1(b) , the keel lift thus generated points almost in the opposite direction from the lift provided by the sails. The two vectors can be resolved into components along and perpendicular to the boat’s direction of motion. For a sailboat moving in equilibrium—that is, at constant speed in a fixed direction—the transverse lift components from sail and keel cancel each other. The component of the driving force from the sails in the direction of motion is the force that is actually moving the boat forward. For equilibrium motion, that force is balanced by the opposing component of the keel lift plus the total resistive force.

Wing theory, developed over the past 100 years for flight, indicates that the most efficient wing is long and narrow. Vortices produced at the wing tip cost energy. A long, narrow wing maximizes the ratio of lift to vortex dissipation, thus providing the best performance for a given wing surface area. That also applies to sailboat sails and keels.

It is now recognized that the most efficient keels are narrow from front to back and deep. Such a keel can have much less surface area than the old long keels. Less area means less resistance. Most modern racing sailboats, such as those used in the America’s Cup races, have deep, narrow keels that are very efficient at providing the lift necessary to prevent side-slipping. Of course, such keels are a problem for recreational sailors in shallow waters.

A sailboat experiences several kinds of resistance. The first is simply the resistance of the hull moving through water. As the boat moves, it shears the water. Water molecules adhere to the hull’s surface. So there must be a shear—that is, a velocity gradient—between the adhering molecular layer at rest with respect to the hull and the bulk of water farther away. The shear means that van der Waals couplings between water molecules are being broken. That costs energy and creates the resistive force, which becomes stronger as the boat’s speed increases. The energy dissipation also increases with the total area of wetted surface.

Although the effect is called frictional resistance, it’s important to realize that the resistive force in water is basically different from the frictional force between solid surfaces rubbed together. To reduce ordinary friction, one can polish or lubricate the sliding surfaces. That makes surface bumps smaller, and it substitutes the shearing of fluid lubricant molecules for shearing of the more tightly bound molecules on the solid surfaces.

For a boat moving through water, however, polishing the hull doesn’t eliminate the shearing of the molecules of water, which is already a fluid. The resistive force cannot be reduced significantly except by reducing the wetted surface. It does help to have a smooth surface, but that’s primarily to reduce turbulence.

The generation of turbulence is a general phenomenon in the flow of fluids. At sufficiently low speeds, fluid flow is laminar. At higher speeds, turbulence begins. Its onset has to do with the shearing of the molecules in the fluid. When the shearing reaches a critical rate, the fluid can no longer respond with a continuous dynamic equilibrium in the flow, and the result is turbulence. Its onset is quantified in terms of the Reynolds number

where ν is the velocity of the flowing fluid, μ is its viscosity, ρ is its density, and L is the relevant length scale of the system. Rearranging factors in equation (1) , one can think of R as the ratio of inertial forces ( ρν ) to viscous forces ( μ /L). In the late 19th century, English engineer Osborne Reynolds found that, with surprising universality, turbulence begins when that dimensionless parameter exceeds about a million.

For a boat of length L moving through water at velocity ν to see when turbulence begins in the flow along the hull, R is about 10 6 Lν (in SI units). A typical speed for a sailboat is 5 knots (2.4 m/s). At that speed, then, one should expect turbulence for any boat longer than half a meter. (Used worldwide as a measure of boat speed, a knot is one nautical mile per hour. A nautical mile is one arcminute of latitude, or 1.85 km.)

Because turbulence dissipates energy, it increases the resistance to motion through the water. With turbulence, a sailboat’s resistance is typically four or five times greater than it is when the flow along the hull is laminar. A rough surface will cause turbulence to be greater and begin sooner. That’s the main reason to have a smooth hull surface.

Turbulence also occurs in the air flowing along the surface of the sail. Water is a thousand times denser than air and 50 times more viscous. So for the air–sail system one gets

For a typical wind speed of 5 m/s, then, one gets turbulence if the sail is wider than about 3 meters. When turbulence forms in the air flow along the sail, the desired pressure difference between the two sides of the sail—its lift—is diminished.

Another important resistive force comes from vortex generation at the bottom of the keel and at the top of the sails. When the air or water moves around the longer-path side of the sail or keel, its speed increases and therefore its pressure falls. As the air or water moves along the sail or keel, it will respond to the resulting pressure difference by trying to migrate from the high-pressure side to the low-pressure side. Figure 2 sketches that effect for a keel. What actually happens, as shown in the figure’s side view, is that the flow angles a bit up on one side and down on the other. When those flows meet at the back of the sail or keel, the difference in their arrival angles has a twisting effect on the fluid flow that can cause a vortex to come off the top of the sail or the bottom of the keel.

Figure 2. Vortex formation by the keel. Unless the boat is sailing straight ahead, there’s a pressure difference between the two sides of the keel. As a result, the water flow angles down on the high-pressure (lower water-speed) side and up on the low-pressure side, creating a twist in the flow that generates vortices behind the bottom rear of the keel.

The effect is well known for airplane wings. Called induced drag, vortex formation costs energy. Figure 3 shows vortices generated at the tops of sails by racing sailboats moving through a fog. A long keel will generate very large vortices. By making the keel short and deep, one can increase the ratio of lift to energy dissipated by vortices. The same is accomplished—especially for sailboats racing upwind—by having tall, narrow sails. It’s also why gliders have long, narrow wings.

Figure 3. Sailtops form vortices visible in fog. The boats were participating in the 2001–02 Volvo Ocean Race off Cape Town, South Africa.

Because it’s often impractical to have a short, deep keel or a narrow, long wing, one can install a vane at the tip to reduce the flow from the high-pressure to the low-pressure side. On planes they’re called winglets, and on keels they’re simply called wings. A modern recreational or cruising sailboat will have a keel that’s a compromise between the old-fashioned long keels and the modern deep, narrow keels—with a wing at the bottom rear end to reduce induced drag. Such keel wings were first used by the victorious sailboat Australia II in the 1983 America’s Cup race. Modern wing theory also suggests that to minimize induced drag, keels and sails should have elliptic or tapered trailing edges. 2 Such shaped edges are now common.

A sailboat also has a resistance component due simply to its deflection of water sideways as it advances. That’s called form resistance, and it obviously depends on hull geometry. It’s easy to see that narrow hulls provide less resistance than do wider hulls. Any boat will always be a compromise between providing low form resistance and providing passenger and cargo space. Seeking to minimize form resistance for a given hull volume, shipbuilders have tried many basic hull shapes over the centuries. Even Isaac Newton weighed in on the question. He concluded that the best hull shape is an ellipsoid of revolution with a truncated cone at the bow.

Extensive computer modeling and tank testing have resulted in a modern hull design that widens slowly back from the bow and then remains fairly wide near the stern. Even with a wide stern, designers try to provide enough taper toward the back to allow smooth flow there. That taper is often accomplished by having the stern rise smoothly from the water rather than by narrowing the beam. If the flow from the stern is not smooth, large eddies will form and contribute to resistance.

As a boat moves through water, it creates a bow wave that moves with the speed of the boat. Water waves are dispersive; long waves propagate faster than short ones. Therefore the length of the full wave generated by the bow is determined by the boat’s speed. As a boat starts to move slowly through the water, one sees at first a number of wave crests and troughs moving down the side of the hull. As the boat speeds up, the wavelength gets longer and one sees fewer waves down the side. Eventually at some speed, the wave will be long enough so that there’s just one wave down the side of the boat, with its crest at the bow, a trough in the middle, and another crest at the stern (see figure 4 ). That’s called the hull speed.

Figure 4. Moving at hull speed, a sailboat generates a bow wave whose wavelength just equals the length of the boat’s water line. The wave crests at bow and stern, with a single well-formed trough in between.

If the boat speed increases further, the wavelength increases so that the second crest moves back behind the boat and the stern begins to descend into the trough. At that point, the boat is literally sailing uphill and the resistance increases dramatically. That’s called wave resistance. Of course, if one has a powerboat with a large engine and a flat-bottomed hull, one can “gun” the engine and cause the boat to jump up on the bow wave and start to plane on the water’s surface. Most sailboats don’t have either the power or the hull geometry to plane. So they’re ultimately limited by wave resistance.

The wave-resistance limit also applies to all other so-called displacement boats: freighters, tankers, tugs, and most naval vessels bigger than PT boats—that is, any boat that can’t rise to plane on the surface. The functional dependence of water-wave speed ν on wavelength λ is well known. From the limiting case for deep-water waves for the solution of the two-dimensional Laplace wave equation, 3 or from a simple derivation due originally to Lord Rayleigh, 4 one gets ν = g λ / 2 π ⁠ , where g is the acceleration of gravity. In the form commonly used by sailors in the US,

where the λ is in feet and ν is in knots.

If one equates the wavelength to the waterline length of a boat, equation (3) gives the boat’s hull speed. For a sailboat with a waterline length of 20 feet (6 m), the hull speed is 6 knots. For a large cruising sailboat with a waterline of 40 feet (12 m), it’s about 8 knots. And for a 300-foot-long naval vessel, it’s 23 knots. In practice, it’s very difficult to make a displacement boat go faster than about 1.5 times its hull speed.

Combining all the components of resistance for a sailboat moving at close to its hull speed, one finds that the frictional resistance contributes about a third of the total, and the wave resistance another third. Form resistance accounts for about 10%, as does the induced drag from vortex generation at the bottom of the keel. The assorted remaining contributions, including eddy formation behind the boat and aerial vortex generation by the sails, provide the remaining 10 to 15%. Of course the fractional contributions vary with boat speed, wave conditions, and the direction of motion relative to the wind.

One can exploit the physics of sailing to calculate boat speeds for a given sailboat for different wind speeds and points of sail. Such calculations are usually performed iteratively by computer programs that start from two basic vector equations to be solved simultaneously:

Here F drive is the total driving force in the direction of motion provided by the wind in the sails, and F resistance is the sum of all the resistive forces. The torques M heel and M righting are the heeling and righting moments caused by the wind in the sails and the weight of the hull and keel.

The force of the wind on the sail is calculated as a lifting force perpendicular to the apparent wind direction and a drag force in the direction of the apparent wind. (The apparent wind is the wind as perceived by an observer aboard the moving vessel.) These lift and drag forces are then resolved into components along and perpendicular to the direction of motion. The net force in the direction of motion is then F drive ⁠ , and the net force perpendicular to the boat’s motion is what produces the heeling moment. The two equations in ( (4) ) must be solved simultaneously because the angle of heel affects the total driving force.

Following Bernoulli’s principle, one takes the force of the wind in the sails to be proportional to the total sail area times the square of the apparent wind speed. The actual forces are then obtained with empirical lift and drag coefficients, given as functions of sail geometry and angle of attack. Frictional resistance is proportional to the hull’s wetted surface area and increases as the square of the boat’s speed. All the various contributions to total resistance involve empirical coefficients. Wave and form resistance are expressed as functions of the hull’s “prismatic coefficient,” which is an inverse measure of the tapered slimness of its ends.

There are simple and complex speed-prediction computer programs. Some that have been refined over decades for racing applications are kept private and closely guarded. Figure 5 shows the results of calculations I performed for a 30-foot (10-m) cruising sailboat using a publicly available program. 5 The figure shows the calculated boat speed as a function of wind speed and point of sail. The predicted boat speeds are greatest when one is sailing about 90° away from the wind direction. Sailors call that beam reaching. It yields a boat speed of about half the wind speed.

Figure 5. Speeds predicted by a computer model 5 for a 10-meter-long cruising sailboat, plotted for three different wind speeds from 6 to 20 knots as a function of the angle of the boat’s motion relative to the wind direction. (10 knots = 18.5 km/h.) An angle of 180° means the boat is “running” with the wind directly at its back. The fastest speeds are predicted when the boat is “beam reaching,” that is, moving at about 90° to the wind. The boat even makes some progress when it’s “close hauling” almost directly into the wind.

Such calculations are confirmed experimentally, with a degree of accuracy that depends on the sophistication of the model and on how much the program has been tuned for a specific kind of sailboat. Broadly speaking, a sailboat is faster if it is longer and narrower, with bigger sails and a smaller wetted surface. Such general rules can, of course, yield a boat that’s longer than one wants, or tips over too easily, or has too little room inside.

So every design feature is a compromise between competing needs. For sailing downwind, one wants fairly square sails, which are best at catching the wind. But for sailing upwind, taller, narrower sails are best, because they maximize the ratio of lift to energy lost by generating vortices. The most efficient keel is deep and narrow, to maximize lift with minimal surface area. But a deep keel is problematic in shallow waters. Shorter keels with wings or bulbs at the bottom usually represent the best compromise for overall sailing.

What’s the highest speed a sailboat can reach? The trick is to reduce resistance. An iceboat can outrun the wind because it has so little resistance. For a sailboat, the resistance comes primarily from having to plow through the water. The best way to reduce that resistance is to move less and less of the boat through the water. One answer is hydrofoils. They are vanes placed below the hull that raise it out of the water as the boat speeds up.

Sailboats with hydrofoils have reached speeds of more than 40 knots when the wind speed was barely half that. One such craft is shown in figure 6 . These vessels are not usually practical for cruising and other normal recreational activities. They’re sometimes dismissed as low-flying aircraft. A more practical alternative is the catamaran—a double-hulled sailboat. Catamarans are being developed to provide relatively stable, fast sailing. Although they are more expensive than traditional single-hull sailboats for a given amount of living space, catamarans are becoming increasingly popular.

Figure 6. A hydrofoil sailboat with solid, winglike sails, moving at about twice the wind speed with the wind abeam—that is, blowing from the side.

Bryon Anderson is an experimental nuclear physicist and chairman of the physics department at Kent State University in Kent, Ohio. He is also an avocational sailor who lectures and writes about the intersection between physics and sailing.

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How Do Sails Actually Work: Full Beginners Guide

The sails are your boat's primary driving force. Your boat is designed to sail , and with good wind it will be faster and more comfortable than using the engine. Engines on sailboats are called "auxiliary" for a reason, almost every sailor hates to use them once they get the hang of sailing. But it won't happen if you don't learn to trim the sails, and to trim them you have to understand them.

But how does a bunch of cloth - your sails - get so much motive power and force? How do sails actually work?

The short answer is that upwind sails generate lift which acts against forces on the keel in the water to pull the boat forward, and downwind sails capture as much wind force as they can to push the boat downwind.

But the detailed answer for sailing upwind is more complex, so come join us for a deep dive into the reason sailboats work and can sail up, down, and across the wind. It's going to get a little into math and a little physics, but we'll keep it on a practical level where you can get the concepts with little hard stuff. And downwind sails are much easier to explain.

To understand sails and sailing, understand the forces which apply to a boat and how they combine to make forward motion. To represent forces, motion, and velocity, we need to use vectors .

We'll do our best to keep this simple, and you will not need a calculator. The important takeaway is how we add forces together to figure a net force or motion .

What is a Vector?

A vector is a number with both a magnitude (a number or size) and a direction. Traveling at 60 miles per hour down the highway is a speed—the car's speed is 60 mph no matter where it’s headed. It has no direction component. But traveling west at 60 mph is a velocity , which is a speed and a direction (west).

You represent the speed easily with a number: "60." But how do you show its velocity headed west? Just as easily, with a vector.

Draw a six-inch line running east/west, then put an arrow on the west end. If we set our scale to one inch = 10mph, then we have our scalar measurement (6") and our orientation - west, or 270°. This arrow is the velocity vector of a car moving at 60mph headed west.

You can represent anything with an orientation and a scalar measurement this way. Whether it's the force and direction a pool cue applies to a ball, the force a hammerhead puts on a nail or the speed and direction of the wind, you can show it with vectors.

Calculating the sailing vector (with pictures)

So what is the point of drawing arrows to describe things? If we can describe forces with vectors, then we can add and subtract the vectors to see how the forces add and subtract, too.

Adding vectors is simple. To add two vectors, put the arrow end of the first vector at the beginning of the second vector. Then, with a straight edge, draw a line from the start of the first vector to the end of the second and put an arrow on the end where it meets the second vector. That new line you just drew is the sum of the vectors.

That's all there is to it. But what does it mean? Let's do a couple of thought exercises to show how it works.

Picture a bicyclist riding north along a road at 20 mph with no wind. The bicyclist feels a 20 mph north wind in her face, right? You can draw that as a line 20 units long pointing directly at the rider's face. The exact units on paper don't matter. That they're consistent is all that counts, so "one square of graph paper = one unit" and "one unit equals one mph" is just fine.

Now picture a 10 mph north wind from straight in front of the rider. What does it feel like to the rider?

That 10 mph wind is added to the 20 mph wind, and it feels like the rider is moving into a 30mph wind. You don't need vectors to see this, it's simple math, and you know how this feels. Just like you know a 10 mph south wind from straight behind the rider will make the total wind feel like just 10 mph.

But what about if there's a 10 mph wind from the east - 90 degrees from the rider's right? What does the wind force feel like in her face now?

Draw your 20-unit north wind line in the rider's face.
From the end of the first line, draw a 10-unit east wind.
With a straightedge, draw a line from the beginning of the north wind vector to the arrow on the east wind vector.
That line is what the rider feels in her face from the combined wind of her motion on the bike and the 10 mph east wind.
You can measure the exact angle of the new vector with a protractor or compass and measure the length in units to get the wind strength. You'd get a wind that felt like 22.4 mph from 26.6° to the rider’s right.

Vector A, the north wind (0°) 20 mph long, and B is the east wind (90°) at 10 mph

The line is drawn to add them together.

The new vector for the wind force.

To explore this further, check out the tool used to make these graphics , where you can create your own vectors and add them together. Just remember it's made by mathematicians, not sailors, so North (0°) is to the right instead of up!

Applying vectors when sailing

You don't need to understand how to measure vectors or even do the math to get all the numbers. All you need to understand is how to add the forces together with the arrows.

Lay them head-to-tail and draw the new line. And that's enough for you to see how the combined forces will look without using a calculator.

Vectors are an important part of understanding sailing. When you learn to navigate, you'll use vectors to calculate the current set and drift or the course to a waypoint (though they won't call it that!). From our examples, you see how they apply to understand apparent wind. You don't need to draw lines on paper all the time, but understanding how forces, currents, and wind affect each other will make you a better sailor.

Now that we know how to measure and add forces, we can talk about the forces on a boat that create upwind motion. There are a few basic physics principles that describe and explain these forces and how they apply to a sailboat. If you never took physics back in the day (or you remember as well as most of us do years later...) don't sweat. We'll keep it relatable.

What is the Bernoulli Effect?

Standing near a chimney, you can feel flue drafts that suck the heat right out of the room if you leave it open, or see them suck smoke up the chimney. And if you've ever flown, did you ever look out the window at what the wing was doing during the flight? Ever wonder how the wings get that big jet plane off the ground?

The answer lies in the work of Daniel Bernoulli, an 18th-century Swiss mathematician. Bernoulli's Principle states that a moving fluid is associated with a decrease in static pressure. The faster the flow, the lower the pressure near it.

At lower speeds, the air is effectively fluid, and the same rules apply. So wind moving over a chimney opening creates a low-pressure spot at the top of the chimney, which draws air up the chimney even when there is no fire. On a windy day, this force is powerful enough to rattle the flue cover when it's closed.

How the sail generates lift

How does this get a plane in the air? And by extension, how does it get power to a sail? Because the same principle applies and upwind sails are very similar to airplane wings.

An airplane wing is a curved surface. As air flows over a curved surface, the air on the outside of the curve has a longer path to travel than air on the inside before it meets again at the back of the wing. Both sides of the wing are moving through the air at the same speed, so the air over the top of the curve must move faster than the air on the bottom.

The faster a fluid moves, the lower the pressure. So the faster air on top of the wing has lower pressure than the bottom, which leads to a lifting force from the higher pressure under the wing. The curve of a wing causes the lifting force towards the top of the wing. The same thing applies to upwind sails - the curve in the sail generates "lift" towards the outside of the sail.

If you want to feel this yourself, the next time you're a passenger in a car, roll down the window and put your hand. Flatten your hand with your palm down parallel to the ground. Then, slowly curve your hand and feel the lifting force!

How the sailor controls lift

If you've watched the wing while a plane takes off or lands, you've seen the pilot adjusting the flaps and the overall shape of the wing. A modern plane wing changes shape from a low-flat profile to a shorter, thicker shape. This different shape changes the amount of lift the wing gives, and the thicker shape has more lift, which helps at takeoff and landing.

The pilot is trimming the wing like a sailor trims a sail.

In a curved surface like an airplane wing (or sail), the chord is the curve's height. The fuller the curve, the longer the chord. And the faster the wind has to travel over the outside to meet the inside wind, which leads to more lift. But it also creates more drag, so once a plane is off the ground and getting closer to cruising speed, the pilot flattens out the wing to reduce drag for higher speed.

For airplanes, this makes taking off and landing easier since the plane can get off the ground and land at lower speeds. For sails, it gives more power for acceleration from low speed or through waves and chop.

What is Newton's Third Law of Motion?

"For every action, there's an equal and opposite reaction."

If you push against a wall, the wall pushes back with the same force. If it didn't, the wall would fall over. A rocket blasts hot gasses from burning fuel out of the bottom, and the rocket moves forward from the reaction force. A car's tires push against the road, the road pushes back, and the car moves forward.

When wind hits a boat's sails, it will either flop over and capsize or skitter sideways through the water unless it has a keel or other appendage under the water . A mono-hulled boat without a keel, centerboard, daggerboard, or other underwater stabilizers can not sail upwind.

So the keel acts as a counterpoise to the forces on the sails to keep the boat upright, but it also pushes against the water. This pushing against the water and the sails is an action, and there's an equal and opposite reaction. This force works against the sail lift to move the boat.

Sailing upwind, you've got a combination of lifting force from the sails, reactive force from the keel against the water, and other forces, like friction and drag from the water. These forces have their own vector arrows.

For simplicity, we will ignore friction and drag, since they're the only forces pushing against the boat in one direction as it moves through the water. While they increase with speed, we can assume the other forces are large enough to overcome them. And you don't want to make me explain adding four or five vectors together at once...

Friction and drag are very important to boat performance. We've simplified them out of the equation to make the force diagrams clearer. Faster boats have less drag from hull form and smooth bottoms, but all the drag and friction vectors point straight back against the boat's forward motion so they only slow the boat down, not change its direction.

In the diagram below, you can see vectors for the lifting force from the sails and the side force of the keep pushing against the water.

Now, add them.

You don't have to do it on paper, as long as you can see that those vectors, when added together, result in a vector that nets a forward motion of the hull through the water. There's your answer.

Any yacht designer will tell you there's much more to getting the correct forward vector. And this is true. The shape of the hull, the smoothness of the bottom, and a few other factors will affect the final forward forces on the boat.

But at its core, the lift vector from the sails added to the keel vector ends up in the boat being pulled forward.

What makes a boat sail downwind is much simpler than the mashup of force vectors we had to work through for upwind sailing. It's quite simple really - the sails fill with wind and pull on the boat to push/drag it downwind.

When you're not going against the wind, the physics is a lot simpler.

Not that you can't look more closely at the forces involved to maximize your speeds and find the best way to sail downwind. But we're not asking how to trim for speed, we're asking how the boat moves. And heading downwind, your full sails catch as much wind as possible to put as much propulsive force onto the hull as possible.

If you've gotten this far, you may wonder "now what?" The next step is to apply that knowledge to sail your boat. Now that you know you can change sail shapes for speed and power and why that works, check out our complete guide to trimming sails so you can trim better and sail faster.

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Beyond the Wow: The Six Types of Ship Motion

Beyond the Wow is a series of education videos for students to learn about the STEM principles behind our deep-sea discoveries. Exploratory missions of the 68-meter (223-foot) E/V Nautilus rely heavily on the knowledge and expertise of our bridge crew and navigators. But to do so, it is important to understand the mechanics of the ocean and how they influence the way in which a ship moves.

At first glance, the ocean may appear flat, but it is anything but. A closer view offers a better look at the wind, currents, and wave action that influence how a ship moves in six degrees of motion: heave, sway, surge, roll, pitch, and yaw. These environmental conditions create a dynamic and ever-changing plan that Nautilus moves across — not just forward and reverse, but up and down, side to side, and even heaving into the air. Regardless, all six happen in combination, and understanding how helps scientists, engineers, and bridge operators make informed decisions about how and where to operate the ship, when it is safe to operate the ROVs, and how to calibrate our technology systems.

Here is a quick look at the six planes of ship motion:

Pitch describes the up and down motion of a vessel. This is characterized by the rising and falling of the bow and stern in much the same way as a teeter-totter moves up and down.
Roll is how we describe the tilting motion of the ship from side to side. Wind and waves push against the ship and cause it to rock back and forth.
Yaw spins the ship on an invisible middle line similar to swiveling on a chair. This can be caused by waves moving in perpendicular to the motion of the ship and can change its heading, or direction.
Heave defines the up and down motion of a ship as large swells heave Nautilus vertically on the crests and troughs of waves.
Sway this sliding motion occurs when the hull of a ship is pushed by the wind or current.
Surge occurs when Nautilus is being followed by larger swells, which can push the vessel forward and impact the front to back motion of the ship.

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Modern Hull forms and Motion Comfort

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To kick off this series of discussion topics, I am posting the following article: Modern Hull Forms and Motion Comfort By Jeff Halpern (This is a comparatively long discussion) Over the past 10 -15 years hull forms have changed dramatically. In the case of the IMS (IRC) typeform that is influencing many of the new breed coastal and offshore cruisers, the longitudinal center of buoyancy has moved aftward. Cross sectional shapes have changed from the semi-circular, or hard-chined MORC inspired hull shapes, or IOR three-part cross sections to vee'd sections forward that merge further aft into elliptical shaped cross sections with softer bilges than had been popular. Keels have gone from the IOR era delta to shorter chord length keels with large bulbs. Entries have become much finer and plumb or nearly plumb bows have become increasingly popular. These changes from came rather quickly, resulting in a question about the relative merits and liabilities of these design features. To begin with it may be helpful to look at a bit of history and more specifically, the source of this rapid change. Many of these same features were Although plumb bows, soft bilges, and centers of buoyancy located proportionately far aft in the boat have been with us nearly from the beginning of yacht design history (for example, look at a set of line drawings for the yacht America or a Friendship sloop, ignoring their trailboards and bowsprit made necessary to support their 19th century sail plans) and were the norm for cruising yachts and working water craft in the early 20th century, finer entries, soft chines, and plumb bows began to show up again in large numbers in the late 1980's and early 1990's. The primary impetus for this current trend was the result of research leading up to boats designed around IMS rule. Unlike earlier measurement rules which measured boats at a limited number of identifiable measurement points, and whose formulas were widely known and so could be 'beaten', the IMS was a velocity prediction program derived formula that measured the boat and created in effect a prediction of performance based on its actual shape. The formula that produced the rating was kept secret so that designers were unable to push specific parameters to beat the rule. Unlike earlier rules where a slower boat with a big rating advantage could win, in the early days of the IMS, there was no advantage to designing a slow boat because you could not cheat the rule. Long overhangs offered no advantage under the IMS in terms of un-rated speed. In fact, the IMS rule precisely understood the extent to which a short waterline was a liability since much of the prediction formula testing had used contemporary short waterline hull forms. Which is not to say that individual designers did not seek ways to produce faster boats than the rule could predict. One reality of racing is that a faster boat generally has a strategic advantage out on the racecourse over a slower boat in its class because the faster boat can sail a little further and therefore take strategic advantage of being sailing on the fastest portion of the course (i.e. more wind or more favorable current). Longer waterlines, for a given boat length, results in less induced drag and higher speeds through the water. But the strategic advantage of that extra speed is only small part of why plumb bows became popular. In looking at other un-rated advantages, designers began to look at motion as an area that no rating rule had previously considered. Studies in the wake of the Fastnet Disaster had lead designers to understand that IOR era race boats (and to a lesser extent earlier CCA era boats) had serious motion issues that were beating their crews to death in any kind of rough going. But beyond the comfort issues of this motion, designers also came to understand that large ranges of motion and rapid changes in motion direction had a real negative impact on the air flow over the sail and water flow over the keel. As sails and keels became more efficient but easier to stall, this issue of motion control offered real opportunities for improved performance for the sails and keel; performance that would be un-rated at that. Designers and research scientists quickly identified three forms of motion that could easily be addressed through the careful weight distribution and hull modeling, namely: rolling, pitching and wave collision. It was always understood that the rate of motion could be slowed by adding inertia. In the case of angular motion, roll and pitch, inertia is actually a moment meaning that the weight is multiplied by the length of the lever arm (squared or cubed depending on the type of calculation) from the axis of rotation. The further from the instantaneous axis (I use the term 'instantaneous' because the roll and pitch axis changes as the shape of the hull in the water changes with movement), or the larger the weights involved, the greater inertia that the vessel will have. With greater inertia comes a slower acceleration of the motion. But like everything else in yacht design, high moments of inertia come with a price. A greater moment of inertia also stores more kinetic energy. So while a vessel with a high moment of inertia has a tendency to change direction more slowly, it also has a tendency to move through a larger range of motion. From a performance design standpoint, (or from the standpoint of crew comfort for that matter) this larger range of motion is also undesirable. To some extent, the source of the inertia is important as well. For example, we can compare two otherwise exactly identical boats, each with equal roll moments of inertia, but one has a heavy mast but less ballast by the same amount added to the rig while the other has a lighter mast and heavier ballast. The high vertical center of gravity of the mast would tend to cause the first boat to roll further than the second boat for an equal roll loading, because the weight in the mast would be on the motion side of the roll axis while the weight in the keel would be on the opposing side of the roll axis. Speed of motion and range of motion can be offset by what designers call dampening. Dampening is the ability to absorb and resist undesirable motion. Dampening is creating a resistance against motion that reduces the amount of kinetic energy that can be stored by reducing the amount of motion in any one direction. From either a performance standpoint, or motion comfort standpoint, dampening ideally needs to reduce the rate of change as well. To do so, dampening needs to be progressive, rather than sudden. If dampening occurs too suddenly too effective the boat will jerk as forces attempt to produce motion and the boat fetches up against the entity providing the resistance. (Pounding is a good example of that) In concept, controlled progressive dampening is exactly how shock absorbers are supposed to work on an automobile. With regards to individual types of motion, designers of IMS type boats began to address roll motion in a number of ways. First of all, the typical IMS typeform reduced form stability from the excessively high levels popularized in IOR boats, 'Open Class' boats and to a lesser extent in MORC derived designs. But beyond reducing the initial stability of the IMS designs, they also focused on a progressive increase in form stability. In other words, as a boat healed, it would initially increase form stability progressively rather than all at once as had been the case with the harder chined light weight boats of earlier generations. Early IMS type form boats don't heel until they suddenly fetch up on chine and stop heeling all at once. Instead they slowly and progressively generate form stability over a moderately wide angle. As a result of the reduced form stability, when IMS type form encounter a wave there is less roll forces exerted on the hull and similarly, because the form stability comes on progressively over a wider angle, these roll forces do not exert as sudden a loading on the boat. These reduced roll loadings are further reduced by careful dampening. In the case of IMS type forms, their tall rigs and deep keels provide high dampening lever arms and as a result, despite their smaller sail and keel areas, proportionately large roll resistance moments of inertia. Which brings us to fine bows, plumb stems and the afterward re-location of the center of buoyancy popularized by the IMS typeform. If you have ever beat or motored to windward in a short chop, try to remember the motion that you felt as the boat encountered each wave. Initially, there was a moment as the boat collided with the wave that to one degree or another you could feel your body thrown forward as the boat de-accelerated. And while you were feeling that force, you could feel the bow being be jerked upward, the whole boat rotating about the pitch axis of rotation. Then you could feel the boat heave (moving vertically) as the wave passed under the center of buoyancy. There is a brief moment during which the boat seems to hang in the air, before the bow begins to rotate downward. And lastly, you felt the bow jerk to a halt or even upward as it hits the back of the wave below. In that description, are three of the six forms of motion; heave, negative surge, and pitch. Heave is heavily dependent on the size of the waves relative to the length of the waterline of the boat. There is little that can be done about heave once the wave spacing approaches the length of the boat. A lighter boat will rise and fall with the wave with very little lag time, essentially moving vertically at the speed and height of the wave. A heavier boat will also rise and fall with the wave with a slight delay between the time that the wave hits the boat and the time that the boat starts to rise. This delay can actually cause a heavier boat to move through a larger range of motion (its momentum carrying it higher out of the wave crest and deeper into the trough). This increased range of travel may also result in less harsh changes in vertical direction at the top and bottom, but not always. Depending on the size, frequency, and configuration of the wave, and the delay in movement of the heavier boat means that it is coming down farther back in the wave, falling further before being fully supported by the wave again. That increased distance means a greater speed and momentum at that point in the cycle and so the heavier boat may actually have a greater de-acceleration when it bottoms out. What can be designed around is the amount of impact force imparted into the hull by the collision with each wave, and the amount of change in speed with which the boat pitches. To begin with, visualize two boats with equal displacement, equal longitudinal centers of gravity, the same deck shape when viewed from above and in profile, same depth of canoe body, same mid-ship cross section, and the same reserve buoyancy (meaning volume of the hull above the waterline forward of the center of buoyancy), but one has a plumb stem and the other has four feet of overhang at the bow. In this example, by its very nature, the boat with the overhang will be more blunt, less knife like, than its plumb stemmed sister. Instead of cleanly slicing through the wave, the boat with the overhang, actually collides with the wave with a greater impact force, and that impact force, both slows the boat down, and also is wearing on the crew. Because both boats have equal reserve buoyancy, the deck will stay equally dry, but because the waves act more suddenly upward on the blunter ends of the boat with the longer overhangs, there is more concentrated rotational force imparted and applied more rapidly (i.e. more of a collision than a gradual application of force) into the forward end of the boat with the longer overhangs. All other factors being equal, greater concentrated force applied further outboard forward means a greater rotation angle; more rapid application of force means a more rapid change in direction. Greater rotation angle and greater speed of motion means a larger flow interruption over the sails and foils and less comfort for the crew. On the boat with the modern hull form, as the bow moves upward, the fuller stern sections build reserve quicker than the overhanging sterns of more older hull forms and that earlier progressive building of buoyancy serves to further dampen the speed and amount of rotation. At this point the boat with the longer ends is moving upward at a greater speed and will have greater kinetic energy causing it to rise higher than the shorter overhang boat. Because it has farther to fall, and the acceleration of gravity is a constant, it will hit the water later on the wave, and with a greater impact force. Another factor that further improves the motion of the IMS type form is that the center of buoyancy is located further aft. If you visualize two boats having their bows lifted an equal distance by a wave, but one boat rotates about a point that is further forward than the other boat's axis of rotation, the angle of rotation on the boat with the longer distance to the axis of rotation will rotate through a smaller angle than the boat with the axis of rotation located further forward. And since the boat with the center of buoyancy located further aft ends up with not only small rotation angle, but with a shorter distance from the axis of rotation to the cockpit, there is less vertical distance experienced by the crew in the cockpit.

Jeff, I thank you very much for your very valuable explanantion and input on this subject. I appreciate it very much. I have problems explaining things this well and without drawing, is almost impossible for me. I believe that this thread, being so informative, should be kept, together with other stuff that has value, in a dedicated section on the board. Maybe Cam or CD can create a place for valuable tech information, in a way we cann all read, but not reply to, or reply subject to verification, to prevent degeneration.

Giulietta, That is a very good suggestion. While I don't necessarily agree with all of Jeff's conclusions and assertions, I believe they are well explained and very helpful -- deserving of ready access by those who are interested in this topic. Which brings up another suggestion that I have been meaning to make: Could the moderators create a new forum subject heading for discussion of "SailBoat Design and Construction"? Generally folks seem to post these topics either under "Buying a Boat" or "General Discussion", but these discussions deserve a category of their own. Buying a Boat is probably the best fit right now, but getting into technical discussions like this one is not really the same as trying to help someone, whether neophyte or old salt, find "the right boat". I'm aware that there are other forums on the Internet that specialize in boat design, but Sailnet seems to have quite a few members with a lot of expertise and experience in this subject (Jeff H, Giulietta, Robert Gainer, Grampus (?), just to name a few). Not everyone is interested in this topic, but for those of us who are it would be nice to keep some of these discussions "in-house" here at Sailnet under their own dedicated topic heading.

Good article. I always thought that calculation of motion comfort derived from just a few numbers can not give a realistic number - Site like http://www.image-ination.com/sailcalc.html just use Ted Brewer's formula and lot of contributing factors are ignored. A small boat with higher motion comfort may be in some conditions very wet and miserable while a larger boat with lower rating may still be dry and easy in the cockpit (not in the V berth in front cabin).

Sounds good. I am not sure about the heavier boat rising further due to momentum and thus falling further. Since it requires a greater mass of water to support it, it will sit lower in the wave if it is supported on less than its waterline length. Consequently it is moving through less distance, and possibly over a greater time if its speed is less. My physics is rusty but I would think that the force exerted is that required to lift the mass by however much the centre of buoyancy rises, and that distance being less, the velocity and thus momentum are less. Hence the observation that heavy boats rise and fall less. As to pitching through cutting through waves, given your assumptions of equal buoyancy forward it follows that the boat with an overhang must have a blunter bow or at least fuller sections forward to match volumes. However in practice it may not. With wide quarters a modern boat may rise less at the bow to the waves because of the dampening provided by the stern, but as the wave reachs the stern it will rise more and the bow go lower. It seems to me that in a following sea the stern will rise more and hence the bow go down more. With overhangs much of the pitch will arise initially from the shorter waterline giving a greater angle of pitch, with reduced dampening until the overhangs immerse. Hence the hobbyhorsing. Just thoughts as I find it of interest although I claim no expertise.

Why do so few cruising sailboats have plumb bows today? Plumb stems make for a longer waterline, they "cut" through chop rather than collide with each wave, and they provide more room below. If my little C30 had a plumb bow it would be an entirely different boat. She does not like the chop...

Very nice writeup Jeff.

Sailhog, plumb bows are difficult to get right for the cruising boat, in part because they "work" or don't work in a tighter band then swept bows. This means if you overload or badly trim up a boat with plumb bows, it is going to be an uncomfortable and possibly dangerous ride. At issues is usually downwind performance. Plumb bows tend to dig in and pig-root around int he wave, meaning that the helm has to perform exagerated and frantic corrections...that sometimes don't work and the wave runs away with the bows and the boat broaches. even when it is not broaching, it makes for an uncomfortable "swirly" ride with an extra twist to the boat motion as the bows bite and get scewed sideways for a little bit of every wave. There are good solutions to this available...but they are not bog standard for production boats that are basically floating caravans. My favourite simple solution is to sweep the below-water-line hull upwards to the plumb bows so that the bow is sharp, and vertical...but not very deep. The boat can thus carve into and through waves when going up wind, and sit back a little and get its nose out of the waves entirely when going downwind. No more biting in and pig-rooting around....But it takes a lot more engineering and design know-how and it all goes for nothing on the day that some new owner decides to mount 120kg of 'something" shiny and nifty in the bows. Sasha

Sasha_V said: Sailhog, plumb bows are difficult to get right for the cruising boat, in part because they "work" or don't work in a tighter band then swept bows. This means if you overload or badly trim up a boat with plumb bows, it is going to be an uncomfortable and possibly dangerous ride. At issue is usually downwind performance. Plumb bows tend to dig in and pig-root around in the wave, meaning that the helm has to perform exagerated and frantic corrections...that sometimes don't work and the wave runs away with the bows and the boat broaches. even when it is not broaching, it makes for an uncomfortable "swirly" ride with an extra twist to the boat motion as the bows bite and get scewed sideways for a little bit of every wave. There are good solutions to this available...but they are not bog standard for production boats that are basically floating caravans. My favourite simple solution is to sweep the below-water-line hull upwards to the plumb bows so that the bow is sharp, and vertical...but not very deep. The boat can thus carve into and through waves when going up wind, and sit back a little and get its nose out of the waves entirely when going downwind. No more biting in and pig-rooting around....But it takes a lot more engineering and design know-how and it all goes for nothing on the day that some new owner decides to mount 120kg of 'something" shiny and nifty in the bows. Sasha Click to expand...

Sasha, So downwind the bow needs to act like a sled to keep it from pig-rooting... I can get my mind around that. My C30 is mighty noisy below when sailing through chop, and I've always attributed it to the wide beam and the shape of the hull below the waterline toward the bow. Noticed your avatar has a plumb bow. Thanks, Captain...

Not buying it. It all sounds good til you consider looking at it from another angle. The boat with overhangs has a progressive, building dampening effect from reserve buoyancy. So, as it hits a wave, the force isn't all at once, but as the bow digs deeper into the wave, more of the reserve is tapped, thus dampening the impact gradually. The plumb bow has less impact with a wave, but also lacks buoyancy, so it will tend to plow. The broader overhanging bow looks like the clear loser in the drag comparison, but plowing drains speed too. As the wave moves back along the hull, the bow will pitch up as the center of buoyancy is encountered, but a boat with overhangs will, while lifting the bow, also utilize the damping effects of an overhanging stern. In other words, the stern will settle or squat some as the lever arm moves back. So, as a consequence, as the hull lifts at the bow, it settles at the stern, smoothly with progressive resistance. This also limits the height the bow rises as the wave moves back. While the angle of motion is a given amount, the total deviation from center is divided between the bow and the stern. A plumb bow and stern, cannot do this nearly as well. As the lever arm moves back on a plumb bow, the wider (and typically flatter) higher buoyancy stern exerts all it's resistance at once. Ever leveraged something that was loose on one end (the bow) and rigid on the other (the plumb stern)? Since the stern is so much more buoyant from the outset, it doesn't settle into the water as the lever arm moves back. As a result, the stern acts like a hinge point on the water. As the wave moves back, the exerted leverage of the wave on the higher buoyancy stern, forces the bow to lift higher as a result, then fall further as the wave moves past the center of buoyancy. More of the angle of pitch is at the bow, with little at the stern. The sharp, low resistance plumb bow then slices deeper into the next wave perhaps submarining as the non-compliant stern rides over the wave and leverages the bow down hard. Having insufficient buoyancy to counter the stern, it plows even more. This begs the question. Since the wave moving past the hull is essentially a constant, why would you eliminate or reduce reserve buoyancy in the bow and have an excess in the stern? Great for racing. The fine, plumb bow slices cleanly through the water, and the high buoyancy stern keeps the boat up on the bow wave. I can see where Jeff's champion would be better for max speed in reasonably calm conditions, but toss and tumble? Forget it. I'll stick with some overhangs. Having been on one of these plumb bow/stern jobs recently in some gusty/slightly beyond choppy conditions, and feeling like I was going to be slingshot from the cockpit due to the pitching motion, I can say she was fast (all sorts of zippy in the initial calm, but not fast enough (to outrun the weather when things got more interesting....and it really wasn't that bad weather-wise), and not comfortable at all, because at the trough of each wave it was BANG, BANG, BANG, and it got a little damp too. Thoroughbreds are beautiful and fast, but I'll stick with my Quarter Horse any day.

I am not sure that the idea of a fixed hinge at the stern is accurate. I would think that the fulcrum would be further forward, at the centre of the horizontal plane. As the bow comes up this would be opposed by the greater stern plane giving a smaller downward movement. While this depends on moments and the distance from the centre of buoyancy effects the angular movement, it seems quite possible that the rise of the bow is limited by the plumb stern.

Jeff, I just read your very detailed post on the impact of the morc rules on performance cruising boat design. I'm in the market for a performance/cruiser and I've been looking at 3 of the boats that you referred to: Santana 30/30 S2 9.1 Kirby 30 Prior to reading your post I was unaware of the morc influence on these boat designs but I had by coincidence identified these 3 as candidates. My mission is to sail the carib for several months or longer. I will make 3-5 day crossings and then layup until i want to change scenery and the weather cooperates. I expect to single hand much of the time. In your post you referred to the Santana and the S2 as examples of late generation designs and the Kirby 30 as a middle generation boat. I would appreciate it if you would elaborate on that and describe the differences between the middle and late generations. Also, for my mission would you think any one of these boats would have any particular advantage? Or would you recommend something different altogether? Thanks in advance, Tom

I am inclined to agree with alot of this article by Jeff from a technical side as his explanations are detailed and demonstrate a firm knowledge of physics and boat design history but IMHO I am unsure of his conclusions in support of blunt bows, massive sail plans and aft buoyancy etc.. ... whether or not the new Open-class or other fat and plumb stemmed type boats are more comfortable for their crews still is the question only individual sailing conditions can answer...as it seems that the new boat are obviously faster and so their crews may experience more short term discomfort but may be sipping gin in the port tavern having arrived quickly while the guys in the old IOR boat are still "comfortably numb in a different fashion 50 miles offshore. Seems it will remain a "different horses for different courses" argument....but it is also lamentable that so few sailnetters have ever chimed in more on this older but quite relevant thread and it's subject matter... ...Morgan in Sw Florida

Step back a bit and read all the references to racing criteria and is should be clear that boats designed to win races are not optomised or even conceived with cruising in mind. Second hand race boats have been used for cruising for a long time but the article makes it clear the compromises trying to win within design formulas seriously compromises the boat as a cruiser. While I appreciate the value of technology evolved by yacht racing, the mistakes made in the name of a better rating formula are an unfortunate legacy for owners wishing to cruise. Yachts like Freedoms were designed for practical use and racing aspects were largely ignored. I have trouble believing any yacht made to a racing formula is the best boat possible.

"To some extent, the source of the inertia is important as well. For example, we can compare two otherwise exactly identical boats, each with equal roll moments of inertia, but one has a heavy mast but less ballast by the same amount added to the rig while the other has a lighter mast and heavier ballast. The high vertical center of gravity of the mast would tend to cause the first boat to roll further than the second boat for an equal roll loading, because the weight in the mast would be on the motion side of the roll axis while the weight in the keel would be on the opposing side of the roll axis." Well, yeah, but why would anyone take a heavier rig and subtract the additional weight of said rig from their ballast? They wouldn't. You said it yourself, all else being equal. Removing ballast makes what you say true, but, again, why do that when it flies in the face of good sense. We aren't talking about dinghys on the pond here. So, as determined by the Fastnet committee, a heavier rig allows for greater resistance to capsize thanks to the very inertia you mention. A heavier hull also contributes to this, as does the lowest possible center of gravity, which comes back to the question of why would anyone remove valuable ballast because of a heavier rig? The Fastnet crews didn't abandon ship for motion comfort issues (fore and aft), they were rolling severely, some being rolled 360 degrees, with many having difficulty righting after capsize. While stability offers comfort, it wasn't a study on motion comfort, it was about stability and capsize. As usual, Jeff, you just have to throw a jab at the CCA. It has been noted that most of the boats that got into serious trouble in the Fastnet race would not have met the minimum size limit of the CCA Bermuda race.... because size matters. It should also be noted that among the smaller boats, those built before 1975 survived with few problems, while many of the (then) new boats suffered badly. Something had changed and later statistical data confirmed that. "Boats everywhere were becoming lighter, beamier, and less stable." Now, no doubt all this led to designers re-thinking things, but a plumb bow and fat behind cannot act in place of weight and the inertia that comes with it.

Nice job Seabreeze...your articulate gust of air you just gave us (which I mostly agree with) has offically rekindled this thread ....at least for the moment...

Jeff_H said: Unlike earlier rules where a slower boat with a big rating advantage could win, in the early days of the IMS, there was no advantage to designing a slow boat because you could not cheat the rule. Click to expand...

Jeff_H said: Which brings us to fine bows, plumb stems and the afterward re-location of the center of buoyancy popularized by the IMS typeform. If you have ever beat or motored to windward in a short chop, try to remember the motion that you felt as the boat encountered each wave. Initially, there was a moment as the boat collided with the wave that to one degree or another you could feel your body thrown forward as the boat de-accelerated. And while you were feeling that force, you could feel the bow being be jerked upward, the whole boat rotating about the pitch axis of rotation. Then you could feel the boat heave (moving vertically) as the wave passed under the center of buoyancy. There is a brief moment during which the boat seems to hang in the air, before the bow begins to rotate downward. And lastly, you felt the bow jerk to a halt or even upward as it hits the back of the wave below. What can be designed around is the amount of impact force imparted into the hull by the collision with each wave, and the amount of change in speed with which the boat pitches. To begin with, visualize two boats with equal displacement, equal longitudinal centers of gravity, the same deck shape when viewed from above and in profile, same depth of canoe body, same mid-ship cross section, and the same reserve buoyancy (meaning volume of the hull above the waterline forward of the center of buoyancy), but one has a plumb stem and the other has four feet of overhang at the bow. In this example, by its very nature, the boat with the overhang will be more blunt, less knife like, than its plumb stemmed sister. Instead of cleanly slicing through the wave, the boat with the overhang, actually collides with the wave with a greater impact force, and that impact force, both slows the boat down, and also is wearing on the crew. Because both boats have equal reserve buoyancy, the deck will stay equally dry, but because the waves act more suddenly upward on the blunter ends of the boat with the longer overhangs, there is more concentrated rotational force imparted and applied more rapidly (i.e. more of a collision than a gradual application of force) into the forward end of the boat with the longer overhangs. All other factors being equal, greater concentrated force applied further outboard forward means a greater rotation angle; more rapid application of force means a more rapid change in direction. Greater rotation angle and greater speed of motion means a larger flow interruption over the sails and foils and less comfort for the crew. On the boat with the modern hull form, as the bow moves upward, the fuller stern sections build reserve quicker than the overhanging sterns of more older hull forms and that earlier progressive building of buoyancy serves to further dampen the speed and amount of rotation. At this point the boat with the longer ends is moving upward at a greater speed and will have greater kinetic energy causing it to rise higher than the shorter overhang boat. Because it has farther to fall, and the acceleration of gravity is a constant, it will hit the water later on the wave, and with a greater impact force. Another factor that further improves the motion of the IMS type form is that the center of buoyancy is located further aft. If you visualize two boats having their bows lifted an equal distance by a wave, but one boat rotates about a point that is further forward than the other boat's axis of rotation, the angle of rotation on the boat with the longer distance to the axis of rotation will rotate through a smaller angle than the boat with the axis of rotation located further forward. And since the boat with the center of buoyancy located further aft ends up with not only small rotation angle, but with a shorter distance from the axis of rotation to the cockpit, there is less vertical distance experienced by the crew in the cockpit. Click to expand...

I'm no expert either in terms of technical or actual water time in a wide spectrum of conditions but it seems more than reasonable that there is no perfect hull shape when it comes to sailboats...only a multitude of various kinds of sailors and types of sailing requirements tasks, etc. and expected performance parameters...the new boats we are seeing for offshore/nearshore racing and cruising seem to spring from the drawing boards of designers who are paying close attention to speed...pure and simple...along with a similar focus on spacious "Scan-design" interiors which often produce what only what might be termed 'initial comfort". We won't see the likes of the CCA and IOR boats again in production and those boats IMHO are better all-around sea boats in all conditions...they had IMHO ... in their more traditonal designs ....more solid built-in safety factors for the average Joe or newbie sailor who is in Long island sound with his family on a given weekend in November experiencing the "learning curve"...so to speak. On the other hand... Many of us would enjoy surfing at 8 knots in one of the newer offshore designs...in good conditions...but that doesn't ease my trepidation of what happens to "crew lucidity" in these types of boats when speed is no longer of any help in dealing with a raging sea. So I guess I'm skeptical whether the speed of these boats offsets their shortcomings...but I will gladly concede that speed is a huge factor...and it's bonuses vs.older, slower and more sea-kindly boats cannot be quickly dismissed....and I tend to think in the big picture they are probably at least as safe as the older seakindlier CCA IOR boats overall...

souljour2000 said: On the other hand... Many of us would enjoy surfing at 8 knots in one of the newer offshore designs...in good conditions...but that doesn't ease my trepidation of what happens to "crew lucidity" in these types of boats when speed is no longer of any help in dealing with a raging sea. So I guess I'm skeptical whether the speed of these boats offsets their shortcomings...but I will gladly concede that speed is a huge factor... Click to expand...

You might have some interest in reading my two articles in GOB. The first is out now and it's on the CCA and how it shaped the boats we know from that era. The second article is on the IOR and it will not be out for at least another month. Sometimes I think I hear here the "old is good and new is bad" theory expressed. I think there are good and bad boats from every era and any extreme approach to a measurement rule, and the CCA had its own rule beating freaks, can produce boats that have idiosyncratic handling characteristics. The light boat vs heavy boat argument goes back father than I do and I'm 65. There is still no definitive objective answer ubnles you want to quantify exactly what you mean by "performance" and that can be a challenge. But it is hard to deny that most modern designs are far more efficient sailing boats compared to the boats of the 60's. Objectively speaking. I think a lot of it depends upon just how you choose to sail. The "ideal" cruiser for one sailor may not be the "ideal" cruiser for another but that does not make each sailor's preference a "bad" boat.

I will be looking for those articles Bob...and I am sure there are more than a few IOR boats that are "freaks" though I cant name any off the top of my head I think we all know 'em when we see one. The CCA boats...well... not so many in that category I would think...but they were slow but steady "wins the race" kind of boats it seems to me. The CCA boats still on the market need alot of work these days to bring 'em back to coastal/near shore passage work if they havent been babied...bulkheads need re-tabbed if not replaced..etc...same could be said for the IOR boats though...and the CCA boats seldom need decks/hulls recored or keel bolt replaced...so I lean toward CCA boats for the sailor who aint got deep pockets like myself...would love a newer ericsson 29 from late seventies in good shape cheap but one like that hasnt dropped from the sky yet for under 10 grand and thats still above my budget ceiling....so many projects to do on the Columbia 29...

souljour2000 said: The CCA boats still on the market need alot of work these days to bring 'em back to coastal/near shore passage work if they havent been babied...bulkheads need re-tabbed if not replaced..etc...same could be said for the IOR boats though...and the CCA boats seldom need decks/hulls recored or keel bolt replaced Click to expand...

Yeah i did my homework a bit to make sure I didnt end up with a boat that needed the keel bolts re-done....that sounds like a nightmare that thankfully alot of the early and mid-sixties Columbias/Pearsons/Seafarers were not fraught with...my '66 Col29 MK II had bricks of lead lowered into and braced into the molded forefoot type full keel form. She has other issues for sure but rotting keel bolts is one I knew I could not afford due to the need for some yard work/heavy equipment renta/etc.

2000: You seem to think that IOR boats frequently need their keel bolts tightened or replaced. Why would you think that? That has not been my experience. I think you might be generalizing based on a couple of boatyard stories you may have heard. The IOR produced some great boats and many of them have made fine family offfshore cruising boats. Some of them were built as throw aways and they are best thrown away. But you need to take far more into account if you are accurately to compare CCA and IOR boats. If the CCA era had the technology that was available during the IOR days you probably would have seen throw away CCA boats.

Hope I wasn't the thread-killer here..but I did try to re-suscitate it too I guess...Anyways...I think this is one of the best threads I have seen on this forum...the brief that Jeff laid out a while back in the thread was well..not so brief..but it was well-explained and a good platform for the thread...hope we can keep it going...I like this topic...jeff as I said made alot of good points and laid out the landscape..it just seems that there is alot of mumbo-jumbo that is so very relative...the only hard data seemed to be the tank-testing where certain newer wide-beam boats did better with successive wave action in terms of resisting complete knockdown...that could be but do we all really want to go to sea in boats that pound and have a lead bullet hanging precariously 8 feet below a rather flat hull...this might be fine for offshore racing with $$$ and testosterone in the balance...and a crew on land giving regular satellite weather updates and support...

SoulJour; With all due respect, at least in part, this is a good example of something which I had just been talking about in the full-keel vs fin keel thread. I apologize for the cut and paste comment. In my mind the problem with discussing this in the abstract, versus analyzing this in the specific, is that for the most part, the majority of fin keel boat which have been built have been aimed at the racing, coastal cruising and value oriented communities. These boats have purposely developed for their use which is clearly different than that of boats intended for dedicated offshore passage-making and cruising. By the same token, a much larger percentage of full keel boats built in recent years were designed with the intent of offshore use. It is easy to say that a purpose built, offshore cruiser- no matter what its keel type, should have a more comfortable motion, more carrying capacity, and a more seaworthy hull form no matter what its size or displacement than would be expected on a dedicated race boat, racer cruiser, coastal cruiser, or even a boat designed to make occasional offshore passages. Where these debates go off the rails is that comparasons are often made between purpose built offshore cruisers versus purpose built race boats, racer-cruisers, value oriented family cruisers and coastal cruisers and so on, when each may be well suited and optimized for their secific intended use and so do not represent a fair example for comparason on the issue being debated. I think that your comment about lead bullet hanging precariosuly 8 feet below the rather flat hull falls in that category. I think that the current trend in race boats and coastal cruisers has moved in a direction which is far less suited to offshore use than I personally would consider ideal. At the time when I wrote the original post of this thread, performance hull forms were more moderate and moved away from high form stability, flat bottomed model to which you refer. At this point the pendulum has swung wildly in the other direction, and so if one were talking about the current trend in racers, and coastal cruisers you would be very right about their ill-suited nature to distance offshore cruising, as was the case with many of the racer, and coastal cruiser type forms from earlier eras mentioned above.

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20 Best Sailing Movies of all Time

Last Updated by

Daniel Wade

June 15, 2022

If you have been looking forward to curling up on the couch, grabbing a bowl of popcorn, and watching some captivating movies, this can be a good time. A good sailing movie can be perfect given that you'll hear a few lines that you're already familiar with when on the dock or setting sail.

This can be a perfect time to binge-watch some of the best sailing movies.

So in no particular order, we'll highlight 20 of the best sailing movies of all time. From the brutal and dramatic tales of man vs. sea to inspirational explorations and expeditions, we've covered it all. Keep reading and you'll be inspired while waiting to get off dry land when it's safe to do so.

Table of contents

All is Lost (2013)

For lone sailors, All is Lost is probably the best movie to give you a glimpse of what might go wrong for you if you decide to sail the big blue ocean alone. With a near-mute performance as an old man who loves sailing alone, Robert Redford puts in an almost quasi-silent performance by portraying the ordeal of what a lone sailor can undergo when the sea turns on you.

Directed by JC Chandor, there's only one person on the screen throughout the film. He's all alone in the vast sea with his damaged boat. He has to become tough, resourceful, and calm even when things turn against him. Single-character movies are a rarity even today but this is a great survival film that perfectly depicts what could happen even to the hardest lone sailors out there.

Master and Commander: The Far Side of the World (2003)

Directed by the talented Peter Weir, this critically-acclaimed movie was nominated for 10 Oscars and won for best cinematography and sound editing. Depicting the return of the high-seas adventure, this movie is skillfully and meticulously adapted from the historical novel by Patrick O'Brian set during the Napoleonic Wars and starring Russell Crowe.

Crowe plays an arrogant captain who pushes his ship crew to the limits while trying to capture a French warship. This movie offers action-packed battle scenes that will keep you on the edge of your seat. This movie gives you an insight of what sailors undergo in their struggles to make it through the high-seas alive.

Captain Ron (1992)

With little sailing experience but with an inherited yacht moored on an offshore island Martin Short hires charismatic Captain Ron to take them back to Florida. The voyage isn't as easy as they expected as they have to face pirates, breakdowns, and other obstacles. They all get more than what they bargained for.

Portrayed by Kurt Russell, Captain Ron depicts the misadventures of a nominal sailing character that is hired by an upper-middle-class father to guide a yacht through the Caribbean. From the marine accidents, pirates, guerilla carnivals to malfunctioning equipment, and Russell's croaked absurdities, this movie is just full of double humor and worthy performance.

Wind (1992)

As one of the biggest races in competitive sailing, America's Cup is often associated with rich people competing in weird-looking boats. But this movie changes this as it takes viewers through the eyes of tanned and rugged Will Parker as played by Matthew Modine. He's hired by a self-made millionaire (Cliff Robertson) to lead his crew in the competition.

Together with his girlfriend Kate who is an equally skilled sailor, Parker intends to win America's Cup but Kate is thrown off the crew leaving Parker angry. When the crew loses America's Cup to the Australians, Parker decides to form his own syndicate to win back the cup.

White Squall (1996)

This movie follows a young man's adventure movie that follows a group of high school students who boards the brigantine ship called Albatross for their senior year at sea. They sail to the tip of South America and back. They get to accept responsibility, learn how to be sailors, and grow up.

The skipper of the ship, Christopher Sheldon together with the 13 teenage boys set sail for an eight-month voyage. The boys soon discover Sheldon's psyche gradations, rattling tension, and freak storms that sink the ship. As a sailor, you'll be disturbed by the fact that four students and two crew members drown, leaving skipper Sheldon facing a fierce tribunal, tortured conscience, and grieving parents and students.

Mutiny on the Bounty (1962)

As one of the greatest epic movies of the 1960s, English Captain Bligh is on a sea voyage to transport breadfruit from England to Jamaica. He is so abusive that he gets on the nerves of his crew members, especially 1st Lieutenant, Fletcher Christian.

Tension eases when they reach Jamaica and the crew indulges in the island's lifestyle but the captain claps some members of his crew in irons as they try to desert. Further abuses lead Fletcher to inspire a mutiny against the Captain. Fletcher and his men set the Captain and his loyal members afloat in a rowboat. This movie offers a realistic depiction of a larger-than-life character that most sailors are known for.

Dead Calm (1989)

Starring Billy Zane, Nicole Kidman, Sam Neil, and a gorgeous 60 ft. ketch, Dead Calm revolves around a mass-murderer who kidnaps and seduces a young beautiful woman after leaving a husband to die on a vessel whose crew he has just murdered.

This movie was filmed in the Whitsundays Islands of Australia, which is one of the best sailing destinations in the world. Bringing forth an epic combination of deadly sailing conditions , complete isolation from the rest of the world, and a skillful villain aboard the vessel, this movie is thrilling and will leave you looking behind your back whenever you're out there on the sea.

The Life Aquatic with Steve Zissou (2004)

This adventure-comedy follows the high journeys of Steve Zissou, a character adaptation of French oceanographer Jacques-Yves Cousteau. It follows his ocean expedition when tracking the ‘jaguar shark' that apparently ate his partner, Esteban.

Esteban had been working with Zissou on a documentary about mysterious circumstances by a shark. This is a sharp film with lots of fun and adventure on the sea.

Kon-Tiki (2012)

Legendary Norwegian explorer and ethnographer Thor Heyerdahl believes that the South Sea Islands were originally colonized by South Americans. Thor, who fears water and doesn't know how to swim, partakes on a voyage in 1947 to prove his belief. Together with five crew members, set sail from Peru on a balsa-wood ancient raft.

Even though their only modern equipment is a radio, they have to navigate through the ocean while relying on stars and ocean currents and they achieve the impossible after exhausting three months at the sea. This is a very spirited adventure that depicts what's possible when we believe in our dreams.

Maidentrip (2013)

A 14-year-old sailor by the name Laura Dekker sets sail on a two-year voyage in pursuit of her dream to become the world's youngest sailor. Laura sets out from Holland and sails throughout the world. Apart from the occasional foul language that Laura uses now and then on the documentary, this is an excellent film that shows what one can achieve when he/she lives her dream and works hard towards achieving it.

The documentary, however, doesn't suggest that Laura is alarmingly young to sail across the unforgiving Atlantic and Pacific Oceans. Instead, she's depicted as an independent outsider who is looking for paradise in a never-ending sea.

Adrift (2018)

In most cases, sailors seem to never anticipate that they may sail directly into a catastrophic hurricane and this is exactly what Richard Sharp and Tami Oldham do when they sail directly in one of the worst hurricanes ever recorded in history.

Tami awakes in the aftermath of the hurricane to find their boat in ruins and Richard is badly injured. And because they do not have any hope that they would ever get help or get rescued, Tami is left with two options: sit there and perish or find strength and determination to save herself as well as the only man she's ever loved.

Turning Tide (En Solitaire) (2013)

In this daring tale, this movie portrays how a fearless sailor known as Yann Kermadec finds a lot of obstacles in his biggest race as a two-hander named Turning Tide falls flat. In a nail-biting tension, the story begins when Kermadec replaces the main skipper in the Vendee Globe on short notice.

After some smooth sailing, things go eerily wrong for the sailor as his ship is damaged and he's forced to anchor off the Canary Islands to repair it. When he gets back on his journey, he soon discovers that a Mauritanian teenage boy has sneaked inside the boat and he has no option but to sail with him at least until they cross the Atlantic Ocean.

The Old Man and the Sea (1958)

An old Cuban angler known as Spencer Tracy is so unlucky that he hasn't caught any fish in 84 days. And despite the commitment of a young boy to bring him food, the angler fears that he's forever lucky but catches a small fish on his 85th day, so he decides to keep fishing.

When one of his many fishing lines hooks a large marlin, he decides not to go back to the shore until he reels it in. For almost two days and nights, he has no choice but to sit there and do everything he can to redeem himself from what seems like a perpetual failure.

Morning Light (2008)

By entering the TRANSPAC, which is one of the world's best open-ocean competitions, 15 young men and women prepare for a sailing adventure of their lives. With world-class teachers, these sailors begin intense training in Hawaii but only reach a climax in an elimination process that comes in the form of who-stays-and-who-goes process.

This documentary follows these sailors for six months as they embark on a 2,300-mile sailing ordeal, which starts in Los Angeles and ends in Honolulu.

The Perfect Storm (2000)

Created by Wolfgang Petersen, The Perfect Storm is a blockbuster that's big on visuals and depicts an action-packed escapade on the water as Captain Billy Tyne and his crew set on a fishing expedition aboard a ship known as Andrea Gail.

They're soon caught up in a catastrophic destructive storm when they decide to risk the storm and have to deal with a very powerful hurricane. At the height of their fishing expedition, their ice machine breaks down and the only way to ensure that their catch doesn't go stale is by hurrying back to the shore to sell their catch. This is exactly why they decide to risk their lives and it doesn't turn out as they expected.

Captain Phillips (2013)

When Captain Richard Phillips takes command of an unarmed container ship known as MV Maersk Alabama from the port of Salalah in Oman, they anticipate that they'll be attacked by Somali Pirates on their way to Mombasa, Kenya.

They attack the ship and Captain Phillips has to use his wits and diplomacy to negotiate with the pirates and save his crew.

Maiden (2018)

As the saying goes; what a man can do a woman can do even better. This is exactly what's depicted by this sailing movie that follows the life of Tracy Edwards as she leads the first all-female crew when competing in the Whitbread Round the World Race.

Covering 33,000 miles and lasting for nine months, this is a truly grueling race that depicts the corrosive sexism that still exists in the sailing world as well as the ocean terrors that sailors have to deal with during voyages or competitions.

Chasing Bubbles (2016)

This is a captivating documentary that follows the journey of Alex Rust who is a free spirit who gives the normal life to sail around the world. Alex is brought up as a farm boy but becomes a stock trader in Indiana. At the age of 25, he decides to abandon his life in Chicago, buys a modest sailboat known as Bubbles and embarks on a very unique free-spirited voyage. It takes him three years to sail around the world and to quench his insatiable curiosity while meeting great people and fulfilling his lifelong dream of becoming a free soul.

This is a breathtaking travelogue that depicts the sailing life of a truly absorbing character.

180° South (2010)

Directed by Chris Malloy, this is a sailing documentary that covers the journey of Jeff Johnson as he travels from Ventura, California to Patagonia in Chile. He does this to retrace the same trip covered by Yvon Chouinard and Doug Tompkins in 1968.

While the two initial explorers made the journey on the land, Johnson travels by sea using a small boat.

Deep Water (2006)

This movie follows the true-life story of Donald Crowhurst, an inexperienced British sailor who enters the Golden Globe, which is the first nonstop boat race in the world. Donald puts up his home as collateral to gain financial backing to compete in the race but soon finds himself on the wrong end of things as he enters the race under-prepared.

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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Starlink for yachts: true remote connection for your boat

November 17, 2022

Phil Johnson looks at Starlink for cruising sailors and asks if internet everywhere and remote switching is set to revolutionise the boating world

Imagine you’re peacefully anchored in a tight cove on the lee of some remote uninhabited island with zero mobile phone reception. But you unexpectedly need to speak with family or a colleague about something important – so you chat by FaceTime. Then you spend the evening streaming a film on Netflix. You don’t even stop to check your connection.

This scenario is getting closer to reality for some cruisers with the release of Starlink RV and Maritime versions. Starlink promises truly unlimited broadband satellite internet service without breaking the bank – but is it really the perfect solution on board?

Starlink is the first in a new generation of low-earth orbiting satellite communications services that promise to deliver low-latency, broadband internet everywhere. Developed by Elon Musk’s SpaceX, Starlink has launched over 2,500 satellites to date – spread out in a diagonal web flying across our horizon. To connect with the network, users purchase a satellite dish (the so called ‘Dishy McFlatface’) and wifi router, assisted by an app downloaded on their phone.

In other words, just plug in the satellite dish and “Boom! you’ve got lightning fast internet everywhere you want to sail!” Or at least that’s the sales pitch that my wife and co-skipper, Roxy, gave me after ordering a Starlink RV unit to install on our 1986 Cheoy Lee Pedrick 47, Sonder, which we’ve called home for nearly four years while living and working remotely.

Taking delivery of Starlink.

Around two months ago a large cardboard box from Starlink arrived. With excitement, we tore into it and put Dishy with its heavy four-legged stand straight on top of the deck, connecting the 75ft cable to the router – which also serves as the power supply – and opened the app to configure. The whole process took all of five minutes and soon the dish’s motor stirred to life, tilting the antennae from one side of the horizon to the other.

From our relatively remote anchorage on the Dalmatian coast of Croatia, we were instantly getting download speeds of over 100 Mbps – far exceeding that of the local LTE cellular network. Impressed by our experience, I asked some other sailors using Starlink RV to see if they too had positive results.

Lain and Brioni Cameron are currently cruising the Caribbean aboard their Leopard 47 catamaran Indioko while documenting their adventures on the YouTube channel RedSeas . Since installing Starlink, the bandwidth and reliability is so good they’ve started a video conferencing collaboration with other YouTubers, something that “simply couldn’t have been done under 4G solutions,” notes Lain.

Like us, they previously used a combination of range boosters, wifi reachers, and cell phone hotspots to manage their digital life, but still found themselves occasionally going to shore “in search of a cafe with reasonable wifi connection.” Since testing Starlink successfully at anchor between St Martin and Grenada, that’s a habit they’ve been able to break.

But it’s not just the Mediterranean and Caribbean. Dave and Amy Freeman video conference with kids in schools from the rugged coastline anchorages of Newfoundland and Nova Scotia, in part using Starlink. They run the non-profit Wilderness Classroom, teaching the natural world while sailing aboard their 35ft steel gaff-rigged cutter Iron Bark. Before Starlink, they say: “We found some locations had a signal that was too weak for us to video conference with schools.” Now they’ve used Starlink reliably all around Newfoundland and Southern Labrador.

The first installation using the stand

The fine print

This might all sound brilliant, but what’s the cost and fine print? Starlink RV is a non-geofenced version of the original Starlink. This means you can use it anywhere within the continent it is shipped, and use it outside the country of initial use for up to 60 days at a time. If you’re using Starlink past the 60-day time limit you’ll need to change the country associated with the account.

However, while Starlink RV includes ‘mobility’ (ie the ability to use the dish in locations other than the address it’s registered to) it does not support ‘in-motion use’ from, say, a moving vehicle or yacht. The terms make it clear that such use will void your warranty. The support page says: “While our teams are actively working to make it possible to use Starlink on moving vehicles (eg automobiles, RV or campervans, boats), Starlink is not yet configured to be safely used in this way.”

Furthermore, there are still dead zones around the world where Starlink either doesn’t yet have licensing approval or the location is too distant from supporting ground stations for the satellites to relay your connection. For the moment, this includes the open ocean, although I’ve heard anecdotally of RV users getting service on passages such as in the middle of the Mediterranean and across the Bay of Biscay. You can check the coverage maps for both RV and Maritime users at starlink.com/map, which also shows the dates for planned expansion roll-out.

There are some other considerations to make. Dishy is not a passive antennae like on an Iridium sat phone, it’s a power hungry phased-array antennae. I measured 40-50Wh in initial testing. And while it’s relatively weatherproof, the system is cumbersome to set up on deck unless you mount Dishy out of the way of rigging. As the crew of Indioko commented: “We see Starlink as a work and entertainment system rather than a replacement for safety systems like Iridium.”

The Freemans also keep their Dishy stowed below decks while under way.

Starlink has released a Maritime version geared towards commercial use. The upgrade comes with two professionally installed dishes, and promises soon-to-be-global coverage using satellite cross-link technology to expand range further into the oceans. This package, though, comes at a significant price hike: $10,000 of hardware and $5,000 per month of service. This version is suitable for superyachts, cruise ships, and tankers. By comparison, Starlink RV has one-time hardware costs of $599 and unlimited data at $135 per month.

For most cruising sailors needing reliable internet in remote anchorages around Europe and North America, the RV service will cover their needs. In two months of using our new Starlink, we’ve been up and down the coasts of Croatia and across the Adriatic to Italy without service ever dropping. The network speeds have been equal or faster than the mobile service offered in these places. For us, as remote workers that need consistent and fast internet everyday to run our e-commerce business, Starlink has been nothing short of a game changer for our cruising plans.

NASA has expressed concern that Starlink satellites could cause a “significant increase in the frequency of conjunction events and possible impacts to NASA’s missions”

Truly remote

Since we moved aboard in 2018, ‘getting connected’ has been a constant effort. Island hopping between different Caribbean countries required maintaining half a dozen local SIM cards, each with different confusing data plans. When we sailed the remote Hebrides I’d be steering into lochs nervously looking at both our navigation chart and our cellular signal levels. The stress of not having a reliable go-anywhere alternative adds a cautionary asterisk when advising others about a ‘workaboard’ life.

That outlook is thankfully starting to change. “Feeling more freedom to anchor where we want rather than feeling the need to be next to a cell tower when we are working,” is how the Freemans put it. Farther-flung cruising destinations like the Pacific or high latitudes, where traditional workaboards couldn’t dream of sailing, are potentially in reach once Starlink builds out its satellite network. I write this article anchored in the remote Kornati islands of Croatia – a place devoid of cell reception that two months ago, before Starlink, we couldn’t have stayed in for any length of time.

Starlink hacks

It’s still early days for this technology so sailors have been getting creative to adapt the RV version of Starlink, which was designed for campervans and similar, to use on yachts. There are several Facebook groups where users share ‘hacks’ for Starlink (all of which are strictly at owners’ risk and not condoned in any way).

A popular, though warranty-voiding, solution is to disable the actuating motor by drilling into the back of the unit. This keeps the antenna stationary and pointing straight up, reducing power consumption while making it easier to mount. In some cases, this also seems to reduce intermittent dropouts in the signal.

Dave and Amy Freeman are live-linking with schools from remote areas of Newfoundland

Dropouts can also occur from blockages in the horizon, as the crew of Iron Bark experienced when anchored near very steep cliffs. We found our Starlink fits perfectly into a fishing rod holder mounted on the stainless steel arch above our bimini top. Its position allows an open view of the horizon that’s clear of all rigging and other electronics. Iain and Brioni of Indioko plan to fabricate two-mounting positions using a 3D printer, one for either hull of their catamaran. This way they can place Dishy on the “preferred side of the boat for clear views of the sky”.

Another much-talked-about hack is modifying the power supply to run on DC power from the house batteries rather than AC power from an inverter. This modification requires cannibalising the router to build your own power over ethernet (POE) board (beyond the technical grasp of me!), but has reportedly further reduced Dishy’s power consumption for some users.

Race for the skies

There are further options just over the horizon that should offer more ‘plug & play’ solutions. OneWeb is promising to compete with Starlink, with a service due to start in 2023. Amazon has pledged to build its own low-earth orbit network, while established satcom companies Iridium and ViaSat are also upgrading their networks.

Things are changing fast with this burgeoning industry. In just the span of a few years, we’ve gone from hoisting a cellphone up the mast in a dry bag for reception to not even thinking about how we might get online when sailing for a remote anchorage.

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Rep. Marjorie Taylor Greene moves to oust Speaker Johnson

(Gray News) - Rep. Marjorie Taylor Greene, a Republican from Georgia, has filed a motion to oust Speaker Mike Johnson.

The move comes amid some Republican dissatisfaction with a budget bill that passed Friday.

The House approved a $1.2 trillion package of spending bills on Friday just a few hours before funding for some key federal agencies is set to expire, the Associated Press reported.

Johnson, R-La., has served as House speaker for five months, taking over for former speaker Kevin McCarthy, who himself was ousted by his own party.

Greene filed the motion but would need recognition on the House floor for it to take effect. But Johnson waived off the move.

The House is scheduled to leave town for a two-week spring recess at the end of Friday’s session, and it’s doubtful any vote on removing Johnson would be imminent.

Greene called the funding bill a win for Democrats that does not secure the border and increases access to abortion.

“No Republican in the House of Representatives in good conscience can vote for this bill. It is a complete departure of all of our principles, especially if you call yourself pro-life,” Greene said. “It is the will of our voters and it is the will of Republicans across the country that this bill should not be brought to the floor that this bill will, will absolutely destroy our majority and we’ll tell every single one of our voters that this majority is a failure.”

The night before Friday’s voting, Rep. Matt Gaetz, R - Fla., warned against trying to oust Johnson, saying that Republican lawmakers fed up with the process would cross the aisle and vote for the Democratic leader, Rep. Hakeem Jeffries of New York, the Associated Press reported.

“If we vacated this speaker, we’d end up with a Democrat,” Gaetz predicted late Thursday. “When I vacated the last one, I made a promise to the country that we would not end up with a Democrat speaker. ... I couldn’t make that promise again today.”

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COMMENTS

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