semi displacement power catamaran

• Featured Cats:
• Woodbridge 50′ Charter Cat
• Bloomfield 86′ MotorSailer Cat
• Shuttleworth 52 AeroRig

A Case for Displacement Power Catamarans

Article by Malcolm Tennant as published in Multihulls Magazine

In our Premier Issue, Malcolm Tennant, one of today’s foremost power catamaran designers, discusses the principles of planing vs. displacement catamarans. In this article he makes clear his choice of the displacement cat.

For some fifteen years now our office has been designing powerboats that combine something of the old and something of the very new. To make a leap forward in comfort and economy we looked back to the close of the 19th Century and the early years of the 20th. We have taken the powerboat wisdom of that time and used it in the designing of very modern power catamarans that can have much more living space than their monohull cousins, and that easily surpass them in comfort and economy. Current thinking has it that to go fast in smaller craft it is necessary to plane. This is because the usual monohull displacement craft are restricted to a speed of approximately 1.34 times the square root of their waterline length (Froudes Law).

To drive a normal displacement vessel faster than this requires an inordinate amount of horsepower and may even lead to foundering in their own bow and stern waves, or by rolling the gunwales under from the enormous torque produced. Planing is a way to circumventing Froudes Law by getting the vessel to plane on top of the water where the wave making drag is no longer a restriction on their performance. However, planing craft do need to be relatively light, i.e.: have good power-to-weight ratios, and planing surface-area-to-weight ratios; are very inefficient when they are not planing, and are not as economical to run at some speeds as the displacement craft.

So we seem to have two distinct type of boats: a. One that is fast, but uneconomical at slower speeds and can have a bone-jarring ride in a seaway; b. The other, that is economical and comfortable in a seaway, but is slow. Is it then even possible to get a craft that combines the best features of both these types? A boat that has reasonable, ­ even good ­ performance with excellent accommodations and is still economical to build and run and has good seakeeping capabilities: ­ or is this just one of those designers’ pipe dreams?

One quite successful attempt to achieve this dream was made by Tom Fexas with his Midnight Lace series of monohull designs, in which he used long, light, semi-displacement hulls to improve economy without compromising performance too much. These boats were, in fact, a compromise (aren’t all boats?) and, to me, only partially successful by reason of his definition of a slim hull which was, of course, forced on him by the need for stability, accommodation and sea keeping. To Tom Fexas a slim hull was one that had a length-to-beam ratio of four (the waterline length was four times the waterline beam). This was certainly narrow by contemporary planing boat standards, but was unexceptional when compared with earlier boats, or with types of hulls that I am proposing should be used.

Before the improvement of the power-to-weight ratio of the internal combustion engine, and the development of the hard-chine, low-deadrise hull that allowed boats to plane, there was only one way to go fast: building long-and-slim, and in the first decade of the 20th Century we find boats such as Slim Jim, that were achieving speeds of 15 knots from a 15 HP engine driving just such long hulls in 1905. Typical of the early boats was Defender: 16.2m (53′) long, having a maximum hull beam of 2.28m (7’6″). Headroom under the flush deck was only 1.45m (4’9″) and she slept six in berths only 500 mm (18″) wide. In anything of a seaway it would have been incredibly wet and uncomfortable.

The boat had a great deal of grace and elegance to her lines, but her rolling at sea, and lack of accommodations, would be totally unacceptable today except for one small detail: a 48 HP motor propelled this 16.2m boat at 16.5 knots! Is it possible, then, to reconcile these old, easily driven, but incredibly uncomfortable hull forms with the current, ever increasing demands for more interior space and more home comforts that can be the downfall of many a well-designed planing craft? I believe the answer is: catamarans! By joining two of these long, slim hulls together and surmounting them with an extensive superstructure, we are able to provide even more than the currently desirable amount of accommodation and at the same time stabilize the hulls so that rolling is no longer a problem.

So it would seem that all we have to do is to make power catamarans with long, slim hulls, and then we will have speed, economy and accommodation. The potential is there, but is it really that simple? The answer, of course, is “no” ­ not quite!

Even a very cursory look at sailing catamarans will show that they are not restricted by Froudes Law. Their very fine hulls place them on a very different part of Froudes’ wave making continuum, and results in their having a very much higher hull speed than he ever envisioned from his observations ­ in the order of 30+ knots is not unusual for these boats. Certainly the boats with this sort of performance are very lightly loaded racing craft, but even the more heavily laden cruising boats do not have much trouble breaking the 1.34 barrier. If these sorts of speeds can be achieved under sail, than it should be much easier under power.

Towing tank tests of long, slim hulls with high prismatic coefficients (fine hulls with a fairly even spread of displacement from bow to stern), such as our displacement powerboats exhibit, have shown no catastrophic increase in wave drag at speed/length ratios above approximately 1.4 ­ such as occurs with “normal” displacement hulls. These high prismatic hulls have a higher displacement hull speed than is “normal.” This test data is further supported by the precisely measured performance tests of such boats as the Zenith-47 Antaeus, the Awesome 2000, the Mako-61, the Jaybee and the Icarus 46 in the full-sized ocean test tank. All these boats have prismatic coefficients greater than 0.66 and all easily exceed their theoretical hull speeds, while returning exceptional fuel economy.

So it would seem that all we have to do is to make power catamarans with long, slim hulls, and then we will have speed, economy and accommodation. The potential is there, but is it really that simple? The answer, of course, is “no” ­ not quite! If we compare a sailing catamaran with a keelboat, we will see that the catamaran has one immediately obvious advantage. It is lighter because it is able to eliminate the lead keel upon which the keelboat depends on for its stability. In the case of the powerboat, there is no such advantage. The catamaran may, in fact, be heavier than the monohull because of its increased area. All is not lost, however, because while the skin area is increasing by the square, the interior volume is increasing by the cube! This possible increase in weight may be a problem with planing catamarans because of their limited planing surface, but it does not mean that our dream is impossible.

The displacement catamaran is not as susceptible to overloading as is the planing craft. The hull speed of the displacement boat is largely dependent on the L:B ratio of the hulls and this does not change very much with modest overloading. This does, however, bring up one of the limitations of the displacement boat. To work successfully, the L:B ratio of the hulls should be in excess of 10, and preferably higher. Consequently, if high displacements and length restrictions force short, fat hulls on the designer, then the displacement approach will not be successful. In this situation the only recourse is to lengthen the hull until the requisite L:B ratio is obtained, or to use a planing hull form.

It will be apparent from this, that the displacement concept would seem to have little place in boats shorter than 10m (32′), unless they can be built light ­ or a very modest performance is required. I have designed smaller displacement boats that achieve quite credible 15-knot cruising speeds from very small horsepower (43 HP per side) engines. But if performance on par with planing vessels is required, then the displacement boat must be able to have long, slim hulls, preferably without the planing boats’ low deadrise, submerged chine sections, as this increases the drag substantially, and even more if the chines break the surface. This, then, is the approach we have taken with a lot of our power catamaran designs: long, slim, easily driven round-bilge, minimum wetted surface hulls that give performance on a par with planing craft, but with considerably better sea-keeping capability and better fuel economy.

It is, of course, possible to question whether these boats really are displacement craft. Current theory says that for vessels of this length, to go this fast, they must be planing. In fact, if we accept the usual definition of planing vessel, namely: that it has a speed/length ratio of more than 2, then these boats are clearly planing. However, a boat is said to be planing when most of its mass is supported dynamically by the downward directed thrust of the water. A vessel that is planing will typically have a bow out trim and will have bodily risen out of the water. The waters are muddied a little by the fact that there is no sudden jump from displacement to planing. It is a continuum and somewhere in the speed/length ratio range from 1.5 to 2 the craft would be considered to be in a “semi-displacement” mode. We have now designed a large number of displacement power cats exemplifying the “long and slim” approach of powerboat design.

The Zenith-47 displaces 13 tons fully loaded, and motors at 20 knots maximum ­ much more economically at 16 knots ­ with only two 122 kw (160 HP) pushing hulls with a 24.5 knot hull speed. A monohulled displacement boat of this length would have a hull speed of about 8.5 knots. The smaller Nomad and Cortez powerboats also have a similar hull speed but are optimized more for economy with slower speeds with small engines. The Icarus-46 has a top speed of 25 knots from two 150 kw (200 HP) turbo-charged diesels. At the upper end of the scale is the Mako-61, an 18.6m (61′) game fishing boat with a hull speed of 37.5 knots which would yield an easy 30 knots with around 500 HP per side. In the interest of economy, this boat is intended to cruise at 16 knots ­ with a maximum of 20 knots ­ using twin 150 kw

These performances are very much faster than those of the traditional displacement boats of comparable size and are on a par with that of a planing boat of similar displacement, but with lesser power requirement and subsequently greater economy. I believe the performance of these designs demonstrates the potential of the displacement power catamaran to be that very elusive and ephemeral animal; the best of all possible worlds: combining excellent accommodation, comfort, and economical performance with good old-fashioned seaworthiness. It seems to me that there is no reason why this old “long and slim” principle should not be applied to lightweight boats with less superstructure and even finer hulls, to produce 30 or even perhaps 40 knots of fuss-free performance from quite modest horsepower.

In fact, this belief has been partially tested with two offshore designs: the 17.5m (57′) Red Diamond II, designed for a Japanese client, capable of a top speed of 33 knots (cruising at 24) from twin 320 kw (430 HP) Yanmar diesels; and the 20m (65′) Awesome 2000, which has a top speed of 28 knots, and an open ocean cruising range of 3,000 miles at 15-knot speed. This craft has made the trip from Long Beach, California to Hawaii using only her internal tanks. Although these displacement cats may not be the fastest things around in flat water, they have demonstrated an ability to maintain much higher average speeds than most other craft regardless of sea conditions. In situations where the high-speed planing monohull is forced to drastically reduce its speed, the displacement catamaran is able to continue on with very little reduction in performance.

This ability is displayed day in and day out by the rapidly expanding commercial catamaran ferry fleets whose operators recognized the economic advantages of this concept early on. It has often been pointed out that many people with displacement boats try to push them too fast and, consequently, would be better off with a planing boat. For these people there is now another alternative: displacement boats with the performance of planing craft and the frugal thirst and smooth comfort of the traditional displacement boat.

• Boat Reviews
• Retro Boats
• Digital Edition
• Competitions

BOAT REVIEW L980 semi-displacement powercat Emocean

• Good separation of spaces
• Secure handling and a dry, smooth ride
• Feels like a bigger boat
• Efficient, foil-assisted hulls provide economy and speed with modest power
• Designed to be trailerable

Boat designer Dan Leech has made a name for himself designing small semi-displacement powercats. The L980 Emocean is his latest.

Sometimes with boats, you don’t know how good they are until you give someone else the helm, hop off and take a look for yourself. Watching your boat go by is the best way to get an honest appraisal. At least that is what crossed my mind as we bobbed around in a RIB with owner Randall Diggs, while the designer of the new L980 Emocean , Dan Leech, did whistling flybys for the camera.

When good design and innovative technology meet meticulous boat building and finish, you always going to have something special. The meticulous bit belongs firmly to owner and self-taught boatbuilder, Randall Diggs, who has just launched Emocean . The good design bit comes from Dan Leech, who has established himself as a leading name in the growing market of small semi-displacement power cats in New Zealand. Combined with the use of semi-foiling technology, the result is exceptional economy, an unbeatable ride, and comfortable cruising. In short, it is impressive.

Construction Having been converted to the power cat idea with his previous boat, a Leech L875, Randall Diggs set about commissioning a bigger model. Only a metre longer but an exponentially bigger boat all around, the bare hull of Emocean was built at Davie Norris Boat Builders in Christchurch and finished off by Randall over an 18-month period, most of it during the covid pandemic.

Layout Semi-displacement power cats work well when the hulls are narrow and the bridge decks high. Dan Leech has incorporated some eye-pleasing lines into this basic concept that give Emocean handsome looks. She has a reverse sheer in the forward sections, accented by a spray chine that runs the length of each hull and terminates at the plumb bows with a step, thus achieving a good interior room with a dry ride. The reverse sheer gunwale allows full-standing headroom throughout the interior and allows the pilothouse to integrate nicely with the steep sides of the hull.

On the Water The first impression of L980 is of elegant space. It is hard to believe you are on a 9.8-metre boat when the feeling is more like a 12-metre boat. The space has been arrived at largely by extending the efficient layout of the smaller Leech models. With storage to soak up the clutter and a clean-flowing deck layout, the vessel always looks like it is ready for a photoshoot for a glossy boating magazine. A closer look at the boat reveals some clever detailing created by Randell over the solid bones of the base design. Walking through the boat every corner angle and detail has been thought through making it feel seamless. This functionality is achieved by keeping the berths and toilet facilities on a lower level, while the helm, galley, and socialising areas are up high in the saloon. The separation of space works well offering a private retreat that is essential to good morale aboard while cruising. Opening up the aft end of the saloon to the deck creates a spacious feeling to the living area. Most launches of this length are only sophisticated day boats, but you get the feeling that Emocean could provide very comfortable cruising for over long periods.

Seawind 1370

Solar panels on the vast roof help keep the batteries charged.

Sessa Yacht Line C47

Sessa vessels have a CE CLASS B rating – certified offshore to 200 miles, for winds up to force 8, and waves up to up to four metres high. Very capable, therefore.

Legacy Marine L45

The L45 is intended to fulfil the role of a luxury motoryacht capable of operating in typical New Zealand coastal conditions.

Lazercat 950

The helm station is well-equipped and simple to operate, thanks to the simplified switching that’s been implemented.

LEECH 1025 SEMI DISPLACEMENT POWER CAT

The new Leech 1025 Semi Displacement Power Catamaran incorporates the latest thinking from designer Dan Leech.

According to Leech, it is the culmination of ten years of design development and refinement of his semi-displacement power catamaran. Being built in Nelson for an Auckland client, the new design will offer an incredibly soft riding, fuel-efficient boat with excellent sea keeping.

Built from full composites from a very high-quality construction using e glass/epoxy laminates on either side of a foam core, it is a solid but lightweight structure, which enhances the boat’s performance. Using the foam core also makes for a very quiet boat.

Features include full standing headroom throughout, a queen-size berth forward, head and shower forward, quarter berths in the port and starboard hulls, a large galley in the saloon, and a large U-shaped settee with a table that can form a double berth.

The cockpit has a side door for easy access from the marina berth, a considerable aft boarding platform, fishing rod locker, huge under-floor storage and built-in seating. The aft cabin bulkhead has a large window that opens and a sliding door, so the saloon opens right up to the cockpit to give great indoor/outdoor flow. The hardtop roof extends aft over the cockpit for sun and rain protection.

Powered by twin Mercury 115hp 4 stroke outboards, an optional foil will be available for added performance. The lightweight structure, efficient hull design, and foil allow small engines to be used and low fuel consumption. The 10.25m power cat carries a beam of 3.80m.

Dan Leech Naval Architecture |  [email protected]

L&B TO DISTRIBUTE VERATRON

Fountaine pajot launch first my4.s, related articles, australia’s own electric motor yacht, alexander marine introduces the d50 coupe, lowrance introduces new eagle fishfinder, the surtees/yamaha grand prize boat, sirocco marine, auckland boat show wrap up, ultimare ears’ epicboom, scibs launches new look vip experience, rayglass boats launches the all-new legend, iliad 53s on display at mandurah open day....

D&B Publishing is proud to have delivered the Pacific regions best power boat read for over 25 years. Our PowerBoat team brings you the news, views and reviews from around the world. A team second to none when it comes to power boating.

• Boat Reviews
• Boat Safety
• Destinations
• Buyer Guide
• General Interest
• Company Profile
• [email protected]
• +64 9 428 2328

• 0 No item in your cart
• SUBSCRIPTION
• Classified Ads
• Technical Specifications
• Destinations
• Address book

• All the magazines

2023 Power Buyer’s Guide - 30 to 40 feet

Article published on 28/10/2022

By Emmanuel van Deth

published in n°SP19 dec. / jan.

This category of ‘multipowers’ incorporates a wide variety of models - from the Open designed for shoal draft waters to the comfortable Cruiser that can accommodate you for weeks on board, or even the catamaran designed just for big game fishing. The common theme: all these models easy to handle thanks to their dual engines and their still modest size.

Create a notification for "Buyer's guide"

We will keep you posted on new articles on this subject.

Dismantlable and transportable

A dismantlable powercat can be transported on a simple flatbed trailer... as long as it is of reasonable length and light in weight. Naval architect Richard Woods was able to test the validity of the concept with his own Skoota 28: the Aegean 30 is a development of the Skoota 28, still for building in plywood/epoxy and dismantlable. The objective was to increase the beam - now close to that of a sailing catamaran - and the headroom while offering two additional berths in the hulls. The outboard motors make beaching easier and safer - no rudders and engine legs. Two 40 to 60 HP engines guarantee a cruising speed of 10-12 knots (16-20 knots top speed).

Architect: Richard Woods Design  Material: Epoxy plywood Overall length: 30’2” (9.20m) Waterline length: 289’ (8.85 m) Beam: 16’5” (5.00 m) Draft: 14” (0.36 m) Headroom in nacelle: 6’3” (1.90 m) Light displacement: 5,500 lbs (2.5 t) Laden displacement: 7,000 lbs (3.2 t) Engines: 2 x 40 to 60 HP outboards  Cruising speed: 10/12 knots Max speed: 16/20 knots

L925 SEMI DISPLACEMENT POWER CAT

Amateur or professional construction in plywood/epoxy.

New Zealand-based naval architecture firm Dan Leech is offering a number of power multihulls from 25 to 60 feet (7.5 to 18 m) for amateur or professional construction. Among them, the L925 is the perfect choice for relaxed cruising for a couple. This model is built in ½” (12 mm) plywood - the panels can be digitally cut - with glass/epoxy reinforcements. Its limited beam will allow you access to a marina slip without any noticeable extra cost. On the other hand, the gain in habitability and stability is considerable compared to a single-hulled motorboat. This kind of construction is very accessible to an enlightened amateur (4,000 hours of work were counted for the first model) all the more so as having outboard motors for propulsion considerably simplifies the technical aspects. Despite its semi-displacement hulls, the L925 is capable of making more than 20 knots with two 90 hp engines.

Construction: Amateur or professional Architect: Dan Leech Naval Architect Length: 30’4” (9.25 m) Waterline length: 24’9” (7.55 m) Beam: 11’ (3.35 m) Draft: 19” (0.48 m) - engines up Recommended engines: 2 x 90 HP outboards Cruising speed: 17 knots Max speed: 22 knots Fuel: 79 US gal (300 l)

ARROWCAT 320

Compact but luxurious.

The ArrowCat 320 is a successful model - now in its third generation. The smallest of the Arrowcat range, it features a luxurious finish - rare in compact powercats - such as a wooden steering wheel, or modern, full instrumentation on a carbon-look dashboard. Inside, the manufacturer has paid particular attention to the owner’s cabin. The 320 is powered by two outboard motors. The limited beam of 10 feet (3.05 m) allows the boat to be transported by road in certain countries such as the United ...

Subscribe to Multihulls World and get exclusive benefits.

Tags : 

• 2023 power buyer's guide

Did you like this article ?

Share this article

Most-read articles in the same category.

2024 Multihull of the Year Election - You’ll soon be able to vote for your favorite multihulls!

Who's Who - Mike Horn: “I fell in love with multihulls”

Catamaranscup - 34 charter catamarans setting out from Athens!

Miami & Florida - The American boating spirit

2023 Sail Buyer's Guide - Multihulls from 30 to 40 feet

2023 Power Buyer’s Guide - 60 to 70 feet

What readers think.

Post a comment

No comments to show.

Follow us on

Vous avez ajouté " " à vos favoris., vous avez supprimé " " de vos favoris., in order to add this article to your favorites, please sign in..

"Voyager" Power Catamarans represent the latest developments in G.R.P. High performance offshore cruisers and sports cats.

PHONE: 0417 780 600

EMAIL:   [email protected] FACEBOOK

• Voyager Range
• V625 Series

V1040 Explorer

• V1100 Discovery
• Specifications

The ‘V1040 Explorer’ is a semi-displacement Sedan Cruiser suited to those in lower access areas, or who prefer an economical single level Cruiser with essential shallow draft and protected props for their explorations. It’s versatile open layout is perfect for family or fishing, and with twin Diesel shaft drives from 100hp to 200hp, this vessel can cruise at 13-18 knots, reaching up to 23knots at top speed

• Fisherman & BoatOwner Magazine
• Multihull World – by Barry Tyler
• Boatsales – Series 2 review
• Bow to Stern – Prior Series 1 review – by Barry Tyler
• Fisherman & Boat Owner – by Weter Webster
• Multihull Powercats – by John M. Sullivan
• Voyager V1040 Hybrid
• Virtual Tour
• Boating New Zealand – by John Eichelsheim
• Multihull PowerCats – Barry Taylor
• Professional Skipper

© 2024 Voyager Power Catamarans Design by Dynamic Productions • MADE ON THE GOLD COAST

Construction plans only

The plans can be purchased separately and the materials can be sourced by the client at their own pace. A  list of the required and recommended materials is provided.

Cad-drawn colour construction plans are supplied in an A3 sized booklet of high detail specifically suited to amateur building.

Study Plans

Study Plans are available for this design, please send a request via our  Contact  page.

How to Order your Spirited 400?

Purchase Order Please complete the online contact form.  Online Form

Order Confirmation On receipt of your order form we will provide you with an order confirmation with the costs and deposit requirements. 

Payment Generally a deposit is made at order and a final payment is made prior to dispatch. Payment for the larger design range is generally made via direct deposit and these bank details are provided on your order confirmation. Payments are made in Australian dollars.

Delivery Estimated delivery times is provided on the Order confirmation. We will contact you with a delivery date and delivery options once the kit has been ordered.

Contruction Plans Printed to order with customised cover sheets and any other design requirements to meets the clients requests.

Kits Pre-cut to order as standard or to meet any specific customised requirements.

Components Built to order as standard or to meet any specific customised requirements.

• Testimonials

P: (+61) 02 4981 8288  

Disclaimer  Copyright © 2013 Spirited Designs. All Rights Reserved.

Semi-Displacement Hulls Explained (Illustrated Guide)

If you want to know exactly what a semi-displacement hull is, this article is right for you. Here, I explain simply what it is, how it works, and why it's different from other hulls.

What is a semi-displacement hull? A semi-displacement hull is a hull design that combines features of the displacement and planing hull. It displaces water at low speeds but is able to generate lift at cruising speed. It is more stable than planing hulls, and faster than displacement hulls. It planes at lower speeds than regular planing hulls.

Generally, you'll find this type of hull on motor cruisers, trawlers, and the likes. Sailboats don't really come in this flavor, and I'll explain why below.

On this page:

Semi-displacement hulls explained, maximum hull speed, semi-displacement hull advantages, semi-displacement hull disadvantages, differences between the hull types, who might like this type of hull, sailboats with semi-displacement hulls, examples of boats with semi-displacement hulls.

A semi-displacement hull is a perfect hybrid between displacement hulls and planing hulls. It's the perfect medium speed range hull design. It is also called the semi-planing hull. To summarize briefly:

• A displacement hull lies inside the water, and displaces it as it moves. It holds up the boat using buoyancy.
• A planing hull lies on top of the water as it moves and holds up the boat using lift. This is called planing .
• A semi-displacement hull displaces water at low speeds, but is able to semi-plane at cruising speeds.

All three of these hull types come with their own unique advantages and disadvantages:

• The displacement hull is efficient and very dependable in rough waters.
• The planing hull is extremely fast and agile.

The semi-displacement hull is a bit of both. It's seaworthy and can be relied upon in rough waters, but at the same time, it's a lot faster than displacement hulls. Semi-displacement hulls are perfect for boats that need to be steady and seaworthy but fast at the same time.

Design Features

The most important thing to understand is that generally, planing hulls are fine and flat aft (in the back), and displacement hulls are bulky and round. The semi-displacement hull combines these two design features. It is flat aft but gets bulkier towards the front. The bow (the front), has more of a wedge shape to it, like a Deep-V. The bow has to be able to displace water and lift at the same time. That's why the quality of the design is really important with these boats.

From the front, it looks like a sailboat, from the back, it looks like a powerboat.

The hull shape allows it to semi-plane. Planing simply means it's riding its own bow wave, lifting it out of the water. Planing is a great way to add speed, but it decreases stability.

The semi-displacement hull is heavier than a planing hull but lighter than a displacement hull. Because of its weight, it can't generate enough lift to fully plane. But because of its weight, it's also a lot more stable in rough waters.

How Does a Semi-Displacement Hull Work?

So now we understand the different features of this hull type, let's see how it comes together. At low speeds , the hull acts as a displacement hull, cutting through the water instead of riding on top of it. This makes it stable and reliable in waves. Its weight and keel make sure it handles well in choppy waves and rough weather, which is why it is a great design for coastal cruisers and trawlers and the likes.

At high speeds , the hull acts as a planing hull, riding on top of the water. This makes it a lot faster. Its flat back allows it to plane, as this will lift the front out of the water (but only partially). At the same time, the design of the bow helps it to climb out of the water. Between 12 - 16 knots (cruising speed), the semi-displacement hull will start climbing its own wave, generating lift. This reduces drag (water resistance). This adds a lot to its top speed. Roughly anywhere between 5 - 10 knots. That's a lot.

The semi planes at lower speeds than planing hulls though. This is great because most semis aren't that fast. The reason? The center of gravity is farther forward than planing boats 1 .

The reason the semi-displacement hull is so much faster is that it's able to climb its own bow wave. Regular displacement hulls can't do this. This means they have an upper-speed limit, called the maximum hull speed. The maximum hull speed is a direct correlation between the length of the boat's waterline and the maximum speed.

To learn more about calculating maximum hull speed, and to view examples of different boat lengths and their upper limit , please check out my previous article here .

• faster at cruising speed
• can outrun storms thanks to speed
• larger range
• excellent rough-water boats
• are able to cross oceans
• shallower draft
• less efficient at low speeds than a displacement hull
• uses a lot of fuel at lower speeds
• a bit less comfortable than a displacement hull
• less storage due to flat aft and fine bow
• not as fast as planing hulls

Difference between semi-displacement hulls and displacement hulls

Semi-displacement hulls:

• have finer bow entry
• are flatter aft
• can generate lift, making it faster
• can outrun storms because of their speeds
• have less storage due to flat aft and fine bow

To learn more about displacement hulls , I recommend reading my full guide on it. It explains the pros and cons of displacement hulls .

Difference between semi-displacement hulls and planing hulls

• are narrower than planing hulls
• have a deeper and narrower hull forward, more like a deep V
• are not as fast as planing hulls
• are a lot steadier than planing hulls
• vessels weight is still supported by buoyancy

Yes, that's right. You can cross oceans with a semi-displacement hull. With a planing hull, that's not recommended. However, for those types of journeys, I'd still pick a full displacement hull over a semi every day of the week.

For examples of the most common hull types , please read my Illustrated Guide to Boat Hull Types here .

If you want to have a comfortable ride, even in moderate to heavy chop, and want to have a reliable boat that also has some speed up its sleeve, this is a great hull design for you. With pretty decent speeds, often anywhere up to 20 - 30 knots, this hull can has plenty of thrill to it, while at the same time being comfortable and reliable. It's perhaps one of the most versatile hull designs out there. In my opinion, it offers the perfect fast-paced family cruiser for people who live near the coast and want to take her out for a bluewater spin.

I haven't heard of any sailboats - monohulls - that have semi-displacement hulls. (If you have, please let me know in the comments below.) I think the reason is simply that sailboats can't deliver the power necessary to generate any meaningful lift. Cruising speed for most semi-displacement boats is roughly 15 - 20 knots - that's when lift is generated and it starts to semi-plane. Monohulls can't get up to that speed.

Catamarans can. There are cats out there with wide and flat aft hull sections, enabling them to get into a semi-plane. This is one of the reasons why cats are so much faster than monohulls.

The most famous semi-displacement boat type is the Maine Lobster boat. Other boats that use semi-displacement are trawlers and motor cruisers.

https://www.soundingsonline.com/boats/how-different-hull-types-react-in-rough-water   ↩

Thank you for a well formed explanation—assuming you’re correct. My wife and I are looking at boating as a retirement plan. She asked what the difference is between hull types. I can send her your link.

Stay safe and healthy!

Thank You for an excellent education, I learned much from your article. Is there a chance ou may provide your comments/comparison of the Majesty 140 and theh Benetti Diamond 145? I would so much appreciate your commentary. Most Appreciated !

MacGregor 26M is a semi displacement sail boat :-)

The MacGregor 26X sailboat is also a semi-displacement hull. Factory specs suggest 24 knot top speed under sail or with a 40 hp outboard motor. I have not reached those speeds under sail … more like 14 to 16 knots.

Thank you so much I understand the different types of hulls so much better!

robert salverda

Hi Shawn, I once owned a Lancer 39.5 foot sailboat. It had two Perkins 4-254 85 h.p engines in it. At full throttle it could actually plane, defying all the rules of a displacement hull, so I am assuming it must have had a semi-displacement hull.

Leave a comment

You may also like, the illustrated guide to boat hull types (11 examples).

I didn't understand anything about boat hull types. So I've researched what hulls I need for different conditions. Here's a complete list of the most common hulls.

A Complete Guide to Displacement Hulls (Illustrated)

Own your first boat within a year on any budget.

A sailboat doesn't have to be expensive if you know what you're doing. If you want to learn how to make your sailing dream reality within a year, leave your email and I'll send you free updates . I don't like spam - I will only send helpful content.

Ready to Own Your First Boat?

Just tell us the best email address to send your tips to:

[email protected]

Tag: prowler power catamaran design by sdi

Growler 710 vt.

The Growler 710 VT has been designed specifically for those interested in a fast, practical run-a-bout for fishing, over-nighting or sports, with three different versions available.

Contact us for more info, current build - malta.

These cats have found huge favour locally and worldwide with special interest from France and New Caledonia. It is refreshing to see some people appreciating the ‘true’ multihull values of a proper A hard-top cover provides much needed shade when out on the water, as well as plenty of space to work while remaining extremely stable in even the largest swells. She has excellent load carrying capabilities, and can be loaded with equipment and passengers more so than other boats of similar size or perhaps just to bring home all the fish! The reduced size bimini reduces interference with rods and casting. Depending on your needs, a small 12v fridge could easily be fitted. This is a new take on the ‘bowrider’ style, with good looks, extraordinary speed and fantastic fuel economy.

For more information please download our study plans on this design using the link below., growler 710 vt study plans, growler 710 vt fishing.

The Growler 710 VT Fishing has been designed specifically for those interested in a fast, practical run-a-bout for fishing. A hard-top cover provides much needed shade when out on the water, as well as plenty of space to work while remaining extremely stable in even the largest swells. She has excellent load carrying capabilities, and can be loaded with equipment and passengers more so than other boats of similar size. Or perhaps just to bring home all the fish! The reduced size bi-mini reduces interference with rods and casting. A small fridge can be installed, and theres plenty of rooms for eskies. Floor space is kept flat with one step forward to maximise the room when fighting a big catch. The Growler 710 VT Fishing is the ultimate fishing machine!

Growler 710 vt sports.

The Growler 710 VT Sports is the ultimate run-about for waterskiing, wakeboarding, or simply taking out friends and family for a day on the water. With plenty of seating for 6 passengers, or more should you require – you won’t have to leave anyone at home. Perfect for loading the camping gear and taking off up rivers, creeks and inland waterways, as well as extremely seaworthy for those adventures that take you out into the ocean swells. Easily beached, just raise the outboards or anchor and swim from the transom. Depending on your needs, a small 12v fridge (and port-a-potty) could easily be fitted to keep the beer cold while lazing on the beach. This is a new take on the ‘bowrider’ style, with good looks, extraordinary speed and fantastic fuel economy.

Growler 710 vt cuddy cabin.

The Growler 710 VT Cuddy is our third option for the ultra-efficient registered VT (Vapour Trail) hull shape used on the 6.5m platform. She boasts a surprisingly roomy cabin, with a double berth from which a table extends to create a dinette if required. A small fridge, small gas cook-top and port-a-potty can also be installed if desired. This little weekender is perfect for inland lakes or skipping out to the islands at a top speed or 45 knots (depending on engine choice). Exceptional ocean going ability is a key feature. The Cuddy can also be trailered and stored in the driveway during the week. Built from balsa-core Duflex panels, this tough little cat is perfect for those weekend trips with friends and family or a romantic retreat with a partner.

Prowler 1500.

The Prowler 1500 is a semi-displacement power catamaran design, following a more traditional style in comparison to some of the more modern power designs such as the growler series.

Prowler 1500 Study Plans - PDF Coming Soon

The bows have been kept quite square and sharp, and the cabin features large wrap around windows and angular styling. the foredeck runs forward to the front of the bridgedeck providing a wide spacious area for sunbathing, enjoying a glass of champagne or giving storage space for dinghy or other cruising toys., the layout is open plan and offers a surprising amount of interior space and accommodation due to the prowler’s wide hulls—significantly wider than that of her alaskan sisters. this extra width does allow a little more freedom when configuring the layout and combats the ‘stuffy' enclosed feeling that being down in the hull can bring., the prowler 1500 is a large displacement hulled cruiser that will sleep 4-86 family or friends comfortably. she has a very large light ‘n airy galley and saloon allowing full-size appliances. the cockpit is also designed for entertaining, cooking, toys, and fishing. the flybridge is generously laid out which could also covert into a premium berth. the upper deck also has wide possibilities for storage or entertaining., the prowler 1500 is a large displacement hulled cruiser that will sleep 4-6 family or friends comfortably..

Exterior CAD Renders

Interior CAD Renders

Prowler 40 Open Cruiser

Prowler 40 Open/Cruiser

Sdi prowler 40 open/cruiser is a commercial power catamaran, available at a very competitive price for a motor-away vessel, the open layout is ideal for dive-boats, day-boats, snorkelling tours and almost any other on-water charter..

No matter where you need to go, or who you're taking, the Prowler Open 40 can get you there quickly and in comfort. The Cruiser version has accommodation and relaxing living areas for the whole family.

This pictured version is an open plan bridgedeck, featuring ample seating for the 32 passengers that she can safely and comfortably carry, along with an additional 3 crew members. the hulls have 1.85 metres of headroom and provide toilet amenities, crew bunks and a galley for food preparation., if you're looking for a fast good-looking commercial vessel that will perform well above expectations and is more affordable than you think - look no further, for more information please contact us regarding study plans., prowler 40 open/cruiser​.

Prowler 33 Cruiser

The Prowler 33 Cruiser is a commercial or pleasure power catamaran offered by Multihulls PCM, located in Slovenia.

Available at a very competitive price for a motor-away vessel and in a number of alternate configurations. pcm 330 has semi-displacement hulls that makes her very efficient at most speeds. it means small engines and economical fuel consumption.

This production vessel als has 2 Double Cabins forward + 1 Cabin in the starboard aft + 1 big Bathroom (2.5m long) with 2 separate washbasins with hot/cold pressure water and shower in the port aft. Inside this bathroom there is a door that brings you to a separate Head with its own washbasin with hot/cold pressure water.

Galley is up on the bridge deck together with the spacious saloon. there is a wooden table and bench seating for 6 people which is convertible to a double bed as well in the saloon. panoramic view through non-opening windows all around is one of her features. the generous cockpit allows boarding through doors on either side and has seating for 8 people together with two handcrafted wooden cockpit tables., if you're looking for a fast good-looking pleasure or dive vessel that will perform well above expectations and is more affordable than you think - look no further, see the full prowler 33 page on the multihulls pcm website here., prowler 33 cruiser​.

Prowler 1360

The Prowler 1360 is a semi-displacement power catamaran design, following a more traditional style in comparison to some of the more modern power designs such as the Growler Series.

The Prowler 1360 is a large displacement hulled cruiser that will sleep 4-6 family or friends comfortably.

Prowler 1360 study plans - pdf.

Prowler 1040 GTR

The Prowler 1040 GTR looks quite like the Growler VTR, both sharing the new ‘Schionning’ sleek, stealth styling above water but the underwater shape is quite different. The Prowler GTR has a standard semi-displacement hull shape.

This is a very efficient hull that travels through the water so doesn’t plane or achieve the very high speeds of the Growler but she is however more economical for longer distance travel and she’ll cruise comfortably and efficiently from 0-22kts.

The hull is rounded so construction uses strip planking for the hull bottoms but the rest of the boat is supplied in a flat panel pre-cut kit for easy building by anyone., prowler 1040 gtr study plans - pdf, flybridge model.

Sedan Model

Growler 950 VT

The ‘Growler 950 VT’ Power Cat offers unparalleled living space. Open living areas and a sense of light flow through the interior design of this boat. The secret behind this is her unusual underwater hull shape. We have managed to achieve a blend of characteristics that has not, until now, been possible to achieve in a power cat.

This amazing boat has the ability to plane. The new underwater shape as well as opening the space in the hulls allows the boat to have enough surface area to propel her onto the plane, offering high speeds and great fuel efficiency.

She is available in a fully pre-cut duflex kit or built to any stage by one of our associated professional boat builders., the growler 950 vt is a mid-sized planing hulled cruiser that will sleep 4-8 family or friends comfortably., growler 950 vt study plans - pdf.

Growler 650 VT

The growler 650 vt has been designed specifically for those interested in a fast, practical run-a-bout for fishing, over-nighting or sports, with three different versions available., these cats have found huge favour locally and worldwide with special interest from france and new caledonia. it is refreshing to see some people appreciating the ‘true’ multihull values of a proper a hard-top cover provides much needed shade when out on the water, as well as plenty of space to work while remaining extremely stable in even the largest swells. she has excellent load carrying capabilities, and can be loaded with equipment and passengers more so than other boats of similar size. or perhaps just to bring home all the fish the reduced size bimini reduces interference with rods and casting. a small fridge can be installed, and theres plenty of rooms for eskies. between speed and luxury., growler 650 vt study plans - pdf, growler 650 vt fishing, the growler 650 vt fishing has been designed specifically for those interested in a fast, practical run-a-bout for fishing. a hard-top cover provides much needed shade when out on the water, as well as plenty of space to work while remaining extremely stable in even the largest swells. she has excellent load carrying capabilities, and can be loaded with equipment and passengers more so than other boats of similar size. or perhaps just to bring home all the fish the reduced size bi-mini reduces interference with rods and casting. a small fridge can be installed, and theres plenty of rooms for eskies. floor space is kept flat with one step forward to maximise the room when fighting a big catch. the growler 650 vt fishing is the ultimate fishing machine, growler 650 vt sports.

The Growler 650 VT Sports is the ultimate run-about for waterskiing, wakeboarding, or simply taking out friends and family for a day on the water. With plenty of seating for 6 passengers, or more should you require – you won’t have to leave anyone at home. Perfect for loading the camping gear and taking off up rivers, creeks and inland waterways, as well as extremely seaworthy for those adventures that take you out into the ocean swells. Easily beached, just raise the outboards or anchor and swim from the transom. Depending on your needs, a small 12v fridge (and port-a-potty) could easily be fitted to keep the beer cold while lazing on the beach. This is a new take on the ‘bowrider’ style, with good looks, extraordinary speed and fantastic fuel economy.

Growler 650 vt cuddy cabin, the growler 650 vt cuddy is our third option for the ultra-efficient registered vt (vapour trail) hull shape used on the 6.5m platform. she boasts a surprisingly roomy cabin, with a double berth from which a table extends to create a dinette if required. a small fridge, small gas cook-top and port-a-potty can also be installed if desired. this little weekender is perfect for inland lakes or skipping out to the islands at a top speed or 45 knots (depending on engine choice). exceptional ocean going ability is a key feature. the cuddy can also be trailered and stored in the driveway during the week. built from balsa-core duflex panels, this tough little cat is perfect for those weekend trips with friends and family or a romantic retreat with a partner..

SENSORI POWER CATS

We've updated our Sensori power cat range with newly developed low drag semi displacement hulls, fresh styling and a new range of layout options. Spec's, layouts and more details coming thru November 2023.

Sensori is our range of power catamarans designed for long range, long term cruising with efficient hull forms and a range of powering options

Powering options include Inboard diesels with shaft or sail drive, outboard diesel engines, and diesel electric systems.

There are two styles of accommodation layout for cruising. In the larger size range (58'/17.6m +) you have the option of the master suite layout. All of the designs offer the possibility of two, three or four cabins in the hulls with additional guest accommodation in the saloon.

Any of the designs on these pages can be converted to day charter or passenger transfer vessels.

Enquire with us for pricing estimates or to have a detailed specification an quotation prepared by one of our builders.  [email protected]

Join the Newsletter

• Scroll to top

• Frank Magazine
• Denison History
• Virtual Tours
• Alaskan Yachts
• Azimut Yachts
• Back Cove Yachts
• Beneteau Yachts
• Benetti Superyachts
• Bertram Yachts
• Boston Whaler
• Broward Yachts
• Buddy Davis Sportfish
• Burger Yachts
• Cabo Yachts
• Carver Motoryachts
• Center Console
• Chris-Craft Yachts
• Cruisers Yachts
• DeFever Trawlers
• Dufour Sailboats
• Fairline Yachts
• Feadship Yachts
• Ferretti Yachts
• Formula Yachts
• Fountaine Pajot Cats
• Grady-White
• Grand Banks Trawlers
• Hargrave Yachts
• Hatteras Yachts
• Hinckley Picnic Boats
• Horizon Yachts
• Hydra-Sports
• Intrepid Boats
• Jarrett Bay Sportfish
• Jeanneau Yachts
• Kadey-Krogen Trawlers
• Lazzara Yachts
• Luhrs Sportfish
• Marlow Yachts
• Maritimo Yachts
• Marquis Yachts
• McKinna Motoryachts
• Meridian Yachts
• Midnight Express
• Mochi Craft
• Neptunus Motoryachts
• Nordhavn Trawlers
• Nordic Tugs
• Ocean Alexander Yachts
• Offshore Yachts
• Oyster Sailing Yachts
• Pacific Mariner Yachts
• Palmer Johnson Yachts
• Pershing Yachts
• Prestige Yachts
• Princess Yachts
• Pursuit Yachts
• Riva Yachts
• Riviera Yachts
• Sabre Downeast
• San Lorenzo Yachts
• Sea Ray Boats
• SeaVee Central Consoles
• Selene Trawlers
• Scout Yachts
• Sunseeker Yachts
• Tiara Yachts
• Trinity Superyachts
• Viking Yachts
• Westport Yachts

5 Power Catamarans For Serious Boaters [New + Used]

Power catamarans for sale with denison yachting..

Power catamarans are an unusual and rare species. Without a mast, these boats look and act more like multihull trawlers. Power catamarans have different benefits from sailing catamarans and monohulls. For one, they have low clearance, so they’re great if your cruising plans involve bridges. Second, they have superior speed and range. And, of course, a multihull provides a comfortable ride and elimination of rolling at anchor.

These fast but smooth-riding boats are perfect for those looking to take a long journey or island-hop with ease. We found 5 power catamarans for serious boaters, currently for sale with Denison Yachting.

1. 80′ Sunreef Power 2021

You’re not going to find a more serious-looking boat than the 80 Sunreef Power 2021 , which made her international debut at the 2019 Cannes Yachting Festival. This power cat offers excellent value considering size, quality, range, and accommodations with her 40-foot beam. You can customize this new 80 Sunreef (hull #8) according to your preferred layout, interior decor, and exterior colors.

This yacht is made for long cruises in ultimate comfort — taking luxury and seaworthiness to a new dimension. With a bold, contemporary hull styling, the 80 Sunreef Power incorporates classic stainless steel portlights, teak sole decks, and subtle ambiance lighting. The 80 Sunreef Power’s immense flybridge is big enough to house a spa pool, a wet bar, and generous seating all around.

Contact Denison yacht broker Alex Clarke to inquire about this power catamaran.

2. 52′ Horizon 2015

GYPSY SOUL is ready to whisk you to your next adventure thanks to twin Cummins QSB6.7- 550 horsepower. The PC52 is a highly refined and technologically advanced cruising yacht, and it shows throughout the boat. Her stand out features include air conditioning on the flybridge, yacht controller, new exterior cushions, and new Garmin electronics. The semi-displacement symmetric hulls are incredibly efficient and ensure a soft, smooth ride and excellent sea keeping. A 3 cabin, 2 head layout makes this boat perfect for a small family.

Contact Denison yacht broker Brian Ragsdale to inquire about this power catamaran.

3. 44′ Endeavour Catamaran 2007

This 44 Endeavour power catamaran is turn-key and ready to cruise you to the Bahamas. (And in cool comfort thanks to air conditioning throughout the boat, including the helm.) She’s a stable boat with an 18.5-foot beam and plenty of space onboard. She comes with custom features, including a 3000 W inverter with 4 solar panels and brand new AGM 4DL house batteries. Just throw your gear on board and cruise out; we’ll catch up later.

Contact Denison yacht broker Charlie King to inquire about this power catamaran.

4. 40′ Sunreef 2022

This futuristic 40 Sunreef Power is a multihull luxury speedster built to order. Sunreef currently has two makes of this model — an open boat with outdoor seating or an enclosed cabin with overnight accommodations. In both models, the two lateral aft folding platforms improve an already spacious cockpit.

This yacht is not only an eye-catcher but also great for entertaining guests. It features tons of seating areas and large sun pads. As a new construction power catamaran, Denison yacht broker Tony Smith can guide you in customizing your Sunreef 40 Power with a design that fits your needs.

Contact Denison yacht broker Tony Smith to inquire about this power catamaran.

5. 34′ PDQ 2002

The PDQ 34 MV Passagemaker is a rare find on the west coast. She’s a very spacious and comfortable power catamaran that boasts more living space and stability than your average single-hulled trawler. WESTEND EXPRESS is perfect for a liveaboard, the Great Loop, or long weekends thanks to 2 staterooms with queen size beds.

The captain can enjoy full engine controls at both the cabin and flybridge helms with upgraded Raymarine electronics, autopilot, AIS receiver, generator, AC/heat, and radar. She is quite literally a passagemaker and will reliably take you on your next expedition.

Contact Denison yacht broker Kurt Jerman to inquire about this power catamaran.

Consider one of these new or used power catamarans for sale, perfect for serious boaters looking for a reliable and stable yacht. These boats allow you to go farther and faster in a comfortable setting. Contact a Denison yacht broker to find your next power cat.

Speak With A Power Catamaran Specialist:

Latest news.

NEWS | March 21, 2024

Extra yachts makes north american debut at the 2024 palm beach boat show.

EXTRA Yachts Makes North American Debut at the 2024 Palm Beach Boat Show EXTRA Yachts will be making its North American debut with Denison with its X99 Fast yacht, MINI K2. Denison Yachting is pleased to announce that its partner EXTRA Yachts will be making its North American debut with Denison at the

NEWS | March 20, 2024

The italian art of shipbuilding.

The Italian Art of Shipbuilding The Denison sales team tours 15 shipyards in Italy. This article was written by Sarah Nadler. The birthplace of all things beautiful, Italy has long been known worldwide as one of the superpowers of building boats. With a long history

How to Qualify a Yacht Broker

How to Qualify a Yacht Broker A good broker can be hard to find when looking to buy or sell your boat. Denison yacht brokers weigh in on what makes a broker a good one. Brokers come in all shapes and sizes. Some yacht brokers have

we are a yacht design practice producing thoughtfully crafted power and sail designs for clients seeking style, efficiency and performance

My studio is based in Auckland, New Zealand. I believe that the yachts I design should be beautiful, functional, and meet the owner's brief.

Our office motto > A successful project is a happy client.

To achieve this I work meticulously, considering projects from every angle, right through to the smallest detail. I strongly believe that good relationships are the key to successful projects, and our office prides itself on building a strong sense of trust and understanding with our clients and suppliers.

What's the point if the whole exercise is not a pleasant experience for all involved?

+64 9 537 2644 contact us online

Design Studio

20 Tanglewood Place Howick Auckland New Zealand