Max Hull Speed
First of all, we need to know the maximum hull speed for a displacement hull, and from that number, we will be able to calculate how much faster the semi-planing (or semi-displacement) hull will be. This is the formula for Maximum Hull Speed on a displacement boat:
Now we need to add the increased efficiency (loss of drag) of a semi-displacement hull, usually, this is somewhere between a 10-30% increase.
Note: “1.3” is the increase in efficiency, if you believe you are on the lower end of the scale this would be 1.2 or 1.1.
This calculator offers a theoretical perspective, but many other factors such as sail plan, weight, and sailor skill, of course, have a profound impact on speed. As we have seen, a semi-displacement hull can exceed maximum hull speed, but we can also see that it isn’t by much. The next step is to reduce drag even further by utilizing a planning hull.
If you want more info, calculate other lengths, or see the speeds in Km/h or Mph then I suggest you check out this free spreadsheet.
Catamaran Freedom Hull Speed Calculator
Note: If you want your own copy just click, File->make a copy.
Below I will answer some of the questions I receive concerning catamaran hull design. The list will be updated as relevant questions come in.
As we have discussed above, a catamaran can definitely have a semi-planing hull, but can it be designed in a fully planing configuration as well?
Catamarans can be configured as planing hulls, although most sailing catamarans are set up as either semi-planing or hydrofoil. Due to the high speeds needed to get a boat to planing speed, this is only possible on racing sailboats or motor-powered catamarans such as high-speed ferries.
Owner of CatamaranFreedom.com. A minimalist that has lived in a caravan in Sweden, 35ft Monohull in the Bahamas, and right now in his self-built Van. He just started the next adventure, to circumnavigate the world on a Catamaran!
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While Part 1 showcased design comments from Richard Woods , this second webpage on catamaran design is from a paper on “How to dimension a sailing catamaran”, written by the Finnish boat designer, Terho Halme. I found his paper easy to follow and all the Catamaran hull design equations were in one place. Terho was kind enough to grant permission to reproduce his work here.
Below are basic equations and parameters of catamaran design, courtesy of Terho Halme. There are also a few references from ISO boat standards. The first step of catamaran design is to decide the length of the boat and her purpose. Then we’ll try to optimize other dimensions, to give her decent performance. All dimensions on this page are metric, linear dimensions are in meters (m), areas are in square meters (m2), displacement volumes in cubic meters (m3), masses (displacement, weight) are in kilograms (kg), forces in Newton’s (N), powers in kilowatts (kW) and speeds in knots.
Please see our catamarans for sale by owner page if you are looking for great deals on affordable catamarans sold directly by their owners.
There are two major dimensions of a boat hull: The length of the hull L H and length of waterline L WL . The following consist of arbitrary values to illustrate a calculated example.
L H = 12.20 L WL = 12.00
After deciding how big a boat we want we next enter the length/beam ratio of each hull, L BR . Heavy boats have low value and light racers high value. L BR below “8” leads to increased wave making and this should be avoided. Lower values increase loading capacity. Normal L BR for a cruiser is somewhere between 9 and 12. L BR has a definitive effect on boat displacement estimate.
B L / L | In this example L = 11.0 and beam waterline B will be: |
Figure 2 | |
B = 1.09 | A narrow beam, of under 1 meter, will be impractical in designing accommodations in a hull. |
B = B / T | A value near 2 minimizes friction resistance and slightly lower values minimize wave making. Reasonable values are from 1.5 to 2.8. Higher values increase load capacity. The deep-V bottomed boats have typically B between 1.1 and 1.4. B has also effect on boat displacement estimation. |
T = B / B T = 0.57 | Here we put B = 1.9 to minimize boat resistance (for her size) and get the draft calculation for a canoe body T (Figure 1). |
Midship coefficient – C | |
C = A / T (x) B | We need to estimate a few coefficients of the canoe body. where A is the maximum cross section area of the hull (Figure 3). C depends on the shape of the midship section: a deep-V-section has C = 0.5 while an ellipse section has C = 0.785. Midship coefficient has a linear relation to displacement. In this example we use ellipse hull shape to minimize wetted surface, so C = 0.785 |
Figure 3 |
C =D / A × L | where D is the displacement volume (m ) of the boat. Prismatic coefficient has an influence on boat resistance. C is typically between 0.55 and 0.64. Lower values (< 0.57) are optimized to displacement speeds, and higher values (>0.60) to speeds over the hull speed (hull speed ). In this example we are seeking for an all round performance cat and set C := 0.59 |
C = A / B × L | where A is water plane (horizontal) area. Typical value for water plane coefficient is C = 0.69 – 0.72. In our example C = 0.71 |
m = 2 × B x L × T × C × C × 1025 m = 7136 | At last we can do our displacement estimation. In the next formula, 2 is for two hulls and 1025 is the density of sea water (kg/m3). Loaded displacement mass in kg’s |
L = 6.3 | L near five, the catamaran is a heavy one and made from solid laminate. Near six, the catamaran has a modern sandwich construction. In a performance cruiser L is usually between 6.0 and 7.0. Higher values than seven are reserved for big racers and super high tech beasts. Use 6.0 to 6.5 as a target for L in a glass-sandwich built cruising catamaran. To adjust L and fully loaded displacement m , change the length/beam ratio of hull, L . |
m = 0.7 × m m = 4995 | We can now estimate our empty boat displacement (kg): This value must be checked after weight calculation or prototype building of the boat. |
m = 0.8 × m m = 5709 | The light loaded displacement mass (kg); this is the mass we will use in stability and performance prediction: |
The beam of a sailing catamaran is a fundamental thing. Make it too narrow, and she can’t carry sails enough to be a decent sailboat. Make it too wide and you end up pitch-poling with too much sails on. The commonly accepted way is to design longitudinal and transversal metacenter heights equal. Here we use the height from buoyancy to metacenter (commonly named B ). The beam between hull centers is named B (Figure 4) and remember that the overall length of the hull is L . | |
Figure 4 |
Length/beam ratio of the catamaran – L | |
L = L / B | If we set L = 2.2 , the longitudinal and transversal stability will come very near to the same value. You can design a sailing catamaran wider or narrower, if you like. Wider construction makes her heavier, narrower means that she carries less sail. |
B = L / L B = 5.55 | Beam between hull centers (m) – B |
BM = 2[(B × L x C / 12) +( L × B × C x (0.5B ) )] × (1025 / m ) BM = 20.7 | Transversal height from the center of buoyancy to metacenter, BM can be estimated |
BM = (2 × 0.92 x L × B x C ) / 12 x (1025 / m ) BM = 20.9 | Longitudinal height from the center of buoyancy to metacenter, BM can be estimated. Too low value of BM (well under 10) will make her sensitive to hobby-horsing |
B = 1.4 × B | We still need to determine the beam of one hull B (Figure 4). If the hulls are asymmetric above waterline this is a sum of outer hull halves. B must be bigger than B of the hull. We’ll put here in our example: |
B = B B B = 7.07 | Now we can calculate the beam of our catamaran B (Figure 4): |
Z = 0.06 × L Z = 0.72 | Minimum wet deck clearance at fully loaded condition is defined here to be 6 % of L : |
EU Size factor | |
SF=1.75 x m SF = 82 x 10 | While the length/beam ratio of catamaran, L is between 2.2 and 3.2, a catamaran can be certified to A category if SF > 40 000 and to B category if SF > 15 000. |
Engine Power Requirements | |
P = 4 x (m /1025)P = 28 | The engine power needed for the catamaran is typically 4 kW/tonne and the motoring speed is near the hull speed. Installed power total in Kw |
V = 2.44 V = 8.5 | Motoring speed (knots) |
Vol = 1.2(R / V )(con x P ) Vol = 356 | motoring range in nautical miles R = 600, A diesel engine consume on half throttle approximately: con := 0.15 kg/kWh. The fuel tank of diesel with 20% of reserve is then |
Owner of a Catalac 8M and Catamaransite webmaster.
Im working though these formuals to help in the conversion of a cat from diesel to electric. Range, Speed, effect of extra weight on the boat….. Im having a bit of trouble with the B_TR. First off what is it? You don’t call it out as to what it is anywhere that i could find. Second its listed as B TR = B WL / T c but then directly after that you have T c = B WL / B TR. these two equasion are circular….
Yes, I noted the same thing. I guess that TR means resistance.
I am new here and very intetested to continue the discussion! I believe that TR had to be looked at as in Btr (small letter = underscore). B = beam, t= draft and r (I believe) = ratio! As in Lbr, here it is Btr = Beam to draft ratio! This goes along with the further elaboration on the subject! Let me know if I am wrong! Regards PETER
I posted the author’s contact info. You have to contact him as he’s not going to answer here. – Rick
Thank you these formulas as I am planning a catamaran hull/ house boat. The planned length will be about thirty six ft. In length. This will help me in this new venture.
You have to ask the author. His link was above. https://www.facebook.com/terho.halme
I understood everything, accept nothing makes sense from Cm=Am/Tc*Bwl. Almost all equations from here on after is basically the answer to the dividend being divided into itself, which gives a constant answer of “1”. What am I missing? I contacted the original author on Facebook, but due to Facebook regulations, he’s bound never to receive it.
Hi Brian, B WL is the maximum hull breadth at the waterline and Tc is the maximum draft.
The equation B TW = B WL/Tc can be rearranged by multiplying both sides of the equation by Tc:
B TW * Tc = Tc * B WL / Tc
On the right hand side the Tc on the top is divided by the Tc on the bottom so the equal 1 and can both be crossed out.
Then divide both sides by B TW:
Cross out that B TW when it is on the top and the bottom and you get the new equation:
Tc = B WL/ B TW
Thank you all for this very useful article
Parfait j aimerais participer à une formation en ligne (perfect I would like to participate in an online training)
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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.
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:
All three of these hull types come with their own unique advantages and disadvantages:
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.
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.
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 .
Semi-displacement hulls:
To learn more about displacement hulls , I recommend reading my full guide on it. It explains the pros and cons of displacement hulls .
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!
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.
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.
I wouldn’t describe my father as a hardcore boat guy. He owned a cabin cruiser and a few sailboats during my childhood, but he spent much more time on the golf course.
That’s why it came as a big surprise, in the mid-1960s, when Dad—ever the gadget enthusiast—built himself a boat: a catamaran, in fact.
Now, I don’t recall spending much time aboard his homemade multihull, but I do recall sailing with him aboard the Hobie Cat he bought shortly thereafter. Cat boats evoke fond memories for me, however I’ve been a monohull powerboat owner ever since.
In the offshore-fishing world, I represent one side of the historic divide between V-hull owners and cat-boat enthusiasts. Make no mistake: V-hulls still dominate, but more American boat buyers have started gravitating to cats during the past decade.
New Designs “I’ve been impressed to see how [the two groups] have stayed segregated, if you will,” explains Bill Cordes, director of sales for Invincible Boats, which has introduced 40- and 37-foot catamaran offshore-fishing boats over the past two years, and yet remains successful with its popular stepped-V-hull vessels. “The guy coming in who’s already on a V-bottom boat is coming in for another V. But we’re getting new looks from guys who are cat guys, who are looking for a bigger alternative.”
Invincible and companies such as Freeman, Seahunter, Insetta and Calcutta are driving a resurgence in multihull-boat building, particularly in the offshore-fishing world. At press time, Calcutta was poised to splash its new 480, an express boat that will be available in inboard and outboard versions; Invincible is expected to add a 35-footer to its multihull stable; and TAG Boats, a new South Carolina company, should introduce its 36-footer. In the next six months, Barker Boatworks plans to debut a new 40-foot cat, and HHH BoatWorks will launch a 35-footer.
Depending on how they’re built, cat designs can offer some general advantages over V-hulls, including a better ride in rough head seas, a broader, more stable platform with little roll at rest, shallower draft, better fuel efficiency and greater deck space.
“On my first World Cat sea trial, I remember getting ready to stabilize myself as I saw that first big wave approaching,” recalls Capt. Shane Jarvis, of Sport Fish Panama Island Lodge ( fishpanamatoday.com ), which operates two World Cat 33TEs. “But the boat never jumped. It just cut through the wave like butter and didn’t buck like I was accustomed to.”
In Panama, captains do a lot of run-and-gun-style fishing and trolling, but they also drift live baits and jig. Offshore runs can total 20 to 50 miles. “The wide 10-foot-6-inch beam of our cats allows plenty of room to move around, and for multiple anglers to cast and fish with minimal to no roll when drifting,” he says.
In fact, outside the United States, catamarans have been popular for a long time.
“Certain parts of the world embraced cats a long time ago—places like South Africa, Australia and New Zealand, where the distances are great and the seas can be pretty rough,” says yacht designer Michael Peters, well-known in the fishing world for creating everything from large inboard sport-fishing vessels to stepped-hull center-consoles. Peters is also currently designing Barker’s new catamaran.
“Yet, the American market never did [embrace cats]. It seems that nobody really got the attention until Freeman. Why that was, I couldn’t completely explain, but suddenly there was a boat that seemed to get good balance and aesthetics, and the fishing world took notice.”
Billy Freeman started Freeman Boatworks in 2006, after years of working in boatyards and welding shops, and cutting up old hulls to rebuild them in his off time. “I bought an old cat, and wanted something bigger and better,” Freeman says. “I called up [naval design engineer] Jesse Rhodes, who was an unknown back then, and I said I wanted to design a cat. I said, ‘If it doesn’t work, it’s on me.’”
Quite simply: It worked.
Freeman says he started calling fishing guides in Venice, Louisiana, who make their living running well offshore into sometimes gnarly seas. “I didn’t have to talk them into a cat,” he says.
Freeman looked to resolve what are considered classic catamaran performance and handling issues, including bow steering and pulling and jerking in certain sea conditions. Traditional cats rode very well into head seas, and remained more stable at rest because of their wide beam. But in a following sea, “they could be a complete handful,” says Peters, who also spent 25 years building offshore racing catamarans. “In high-speed turns, they do what we call a ‘destroyer turn,’ as in a Navy vessel. They bank outboard.”
Cordes says Invincible sought the same handling innovations from its designers Morrelli & Melvin, a California firm. In fact, the Invincible boats bank inboard like traditional V-hulls.
Peters says the resurgence of the planing catamaran, and its subsequent redesign, has resulted from a perfect merge of technology and timing. “Part of it is the new, large outboards that put these boats in the 60-plus mph range,” Peters says.
Curb Appeal Freeman’s boats also looked better than traditional boxy cat boats, which feature near-vertical sides. Longtime multihull specialist World Cat—which evolved out of the original handful of Carolina cat builders from the 1980s—saw the new design trend and created its X series, beginning with the 280CC-X in 2017.
However, World Cat’s customers want greater amenities and comforts than do 100 percent hardcore fishermen. “This buyer [of the 280CC‑X] is 80 percent fish, 20 percent cruise,” says Wyatt Lane, World Cat’s national distribution manager. “Our design process started with a sales scope.” Criteria for that include the various attributes the boat needs for salability such as its speed, comfort factors and price point.
“With the 28, one of these requirements was aesthetically we had to work on changing the traditional cat look and raising that bar,” he says. “The deck cap and hullsides are a challenge. You can’t have a lot of flare because of how skinny the hull is. So you’ve got to be creative.”
The cats of the ’80s came from a similar surge of creativity, but they fell short for a variety of reasons. “Early designs were flawed. They were somebody’s backyard dream,” says Steve Ellis, who founded Calcutta Boats in 1996. “They didn’t have enough reserve buoyancy, and they all bow-steered really badly and sneezed really badly.” (Sneezing occurs when spray shoots out the front of the tunnel and blows back toward the helm.)
Those boats featured knife-edge entry angles, which could easily bury the bow into oncoming waves. “Very few of the cats were really designed” by naval architects, Ellis continues. Calcuttas and many of today’s modern cat builds come from the desks of designers such as Jim Ryan, of Locus International, who drew up the Calcutta 480.
Invincible’s Cordes says the evolving industry piqued his company’s interest. “I think the overall versatility of the boat has got the attention of a lot of folks,” he says. “The sheer volume of storage, and then you get into the fishing platform that it is. It really is something new and exciting.”
Venice, Louisiana, captain John Cole, with Southern Catch Outfitters, has run Invincible’s 40 Cat for the past two fishing seasons. “Invincible did a lot of homework and spent some money,” Cole says. “There are two aspects I like best: how it runs and the internal layout.”
He says it took a little time to learn how best to trim out the boat and engines, but he says he now has high confidence and that the handling is very predictable.
The layout is a mix between hardcore fishing boat and family boat, which serves all of his clients. “The 12-foot beam carries all the way to the bow. There’s so much deck space and square footage,” he says. “I can have a customer fighting a fish next to the console, and I can walk around him if I need to get ahead of him. Plus, the in‑deck storage on the cat boats is just ridiculous.”
Hull Variations The majority of today’s catamarans feature planing hulls—designed to rise up on top of the water—rather than displacement hulls, which plow through the water. They can have asymmetrical or symmetrical sponsons. The former focuses more on forcing air down through the tunnel to create lift, says Rob Coffey, director of sales and marketing for Insetta Boatworks, which builds a 45-foot semicustom asymmetrical cat.
Looking at the bow of a boat with asymmetrical sponsons, what you’d see would look like a V-hull split down the middle: The inside sponson edges would be straight from hull bottom to the water, and the outside edges would angle. The symmetrical hull would look like two small V-hulls side by side.
Coffey says the asymmetrical sponsons float higher and help the boat turn with less outboard force.
Insettas also feature steps, as do Invincibles and several others. Steps do for cats what they do for V’s: They break the surface tension, and create better speed and efficiency.
With asymmetrical sponsons, “you’ve helped correct the turning, but you’ve not made the head sea ride quite as good,” Peters says. “We’re really at the beginning of the curve in perfecting the designs.”
To help the new Barker boat perform better in a head sea, Peters says he made the bow fuller, not as sharp and pointed. A too-sharp angle of entry means the bow can act like a rudder. “What we opted for was saying, if you put this much horsepower in the boat to go 60-plus mph, we want a boat that can absorb all that horsepower and not become difficult to drive,” he says. “We opted for a boat that we feel will bank more appropriately in a turn.”
Creature Comforts Center-console catamaran builders also face a challenge when creating interior space. A boat that features two hulls with a tunnel between means no step-down beneath the console. To compensate, the builder can increase the interior-console height, but “how do you do that and not have a telephone booth in front of you?” World Cat’s Lane asks.
Cole says the V-hulls he owned prior to his Invincible cat always featured a spacious cabin with a V-berth. However, he says, that just became a black hole for storage anyway.
Companies such as Insetta, Calcutta and World Cat, whose customers often want overnighting capability, have come up with creative solutions. Insetta’s 45, for instance, features an interior-console full-size berth, a plumbed head, and a kitchenette with a microwave, freshwater sink and shower wand. At the bow, Insetta designed twin single V-berths.
Cat builders have also addressed the problem of bow sneezing. For instance, World Cat formed what it calls a Vector Pod in the tunnel near the bow. It helps break up incoming water, creating aeration and reducing friction. As air and water pass through the narrowing tunnel aft, the mixture increases in velocity with a subsequent decrease in forward pressure.
Read Next: Boat Review: Invincible 40 Catamaran
In the next decade, designs will continue to evolve, Peters says. Fishing-boat cat hulls are now at a point in their evolution that deep-V hulls experienced in the 1960s and ’70s. “We’ve got a perfect confluence of things happening. Development happens when things overlap at the same time,” he says.
Billy Freeman says that 35 years ago when the Carolina cats emerged, some builders predicted that monohulls would become obsolete. They didn’t. “I think they didn’t because [the early cat builders] screwed it up. They built on a budget. They had to cheap it out to get to the same price as a monohull.”
Clearly today’s crop of resurgent cat builders has planned a better outcome.
Crazy Cat Traits Out of necessity, catamarans employ a number of design characteristics most anglers would not expect. For instance:
1. Most cats feature a higher deck level than V-hulls, and in fact, the whole boat is generally taller, Calcutta Boats founder Steve Ellis says. That can result in higher gunwale heights and freeboard, making it tougher for anglers to reach the water to release a fish aft—without the assist of a side dive door or an aft tuna door.
2. An offshore cat boat’s height and its tunnel also necessitate at least twin outboards or quads—one or two per side—though Calcutta and Insetta have designed vessels for inboard power.
3. Trim tabs can create problems as well, competing with the outboards for space along the width of the sponson. However, yacht designer Michael Peters says interceptors—blades that drop down vertically—prove less problematic to mount.
4. The wake behind a cat is generally smaller than that created by a deep-V. That’s due to the weight of the boat over two hulls. The narrower hulls push less water out of the way, Peters says.
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The advantages of a world cat catamaran. a smoother ride is only the beginning.
Take a sea trial on a World Cat catamaran and you’ll understand just how smooth, just how exhilarating, and just how much fun boating can be. But, a smoother ride is only one of the many advantages a power catamaran offers over a monohull. In fact, a World Cat offers you…
Chances are, you own – or owned – a monohull boat. And that means you’ve endured pounding, slamming, and slapping. Monohull manufacturers employ deep V designs to try to lessen the abuse, but the result is often just more rocking and rolling whenever you stop or troll your boat. But a World Cat power catamaran offers you a better boating experience without all the exhausting physical abuse.
Smoothness. stability. speed. world cat hulls are designed to deliver all of them..
When it comes to choosing the ideal boat, World Cat gives you more and better choices. It all begins with the two key hull designs that we offer. While each design shares the same major advantages of a power catamaran – a smoother ride, better stability, and shallower draft – our different hull choices can help you “fine tune” a better boating experience.
(used in all World Cat boats) – if you’re looking for speed, you’ll find it with this design. By employing a flatter V-bottom surface, you get on plane quicker for maximum speed. This design delivers racecar like performance. And, while traditional monohull boats slam you hard when coming down, this action is greatly reduced in a World Cat power catamaran. Which means less abuse and more control for you.
(used in our Glacier Bay Edition boats) – this design offers a softer ride, and has unique handling characteristics, which its thousands of satisfied owners swear by. Its unique design provides outstanding seakeeping and a soft ride by keeping larger sections of the hull in the water for maximum stability while underway. Its balance of hull buoyancy and dynamic lift reduces drag and increases efficiency.
World Cat boats deliver a smoother, softer, faster and drier catamaran ride in even the roughest, toughest conditions. The secret – and science – behind this better boating experience is intelligent engineering – which incorporates our VectorFlo® hull design.
This unique hull innovation combines air and water at the scoop-shaped bow and channels the mixture into the tunnel between the twin hulls. As part of the design, a Vector Pod, forward in the hull, helps to break up incoming water, creating aeration and reducing friction. As the mixture passes through the narrowing tunnel channel, it increases velocity, while decreasing forward pressure and drawing the aerated water and spray aft through the tunnel.
The result?
So, you get a better boating experience in all kinds of seas. But, don’t take our word for it, take a sea trial and experience the VectorFlo® advantage yourself.
The process of designing a catamaran hull is equal parts physics, experience and technology, and as it is a significant investment in time and resources, it needs to be done extremely well. Here we describe what goes into World Cat’s ‘secret ingredient’ – the hull:
Catamarans generally have significantly greater planing characteristics than comparably sized monohulls.
The defining aspect of a World Cat catamaran and the key to its advantages is the tunnel – as a unique situation where air is available underneath the boat , the resulting aerated water ‘cushion’ softens the ride.
At WorldCat, we work to create the perfect balance between function and style:
At World Cat, we believe we have the industry’s best-performing hulls. But as we design new hulls, we continue to strive to seek out new shapes and materials to further improve the catamaran experience.
Experience the thrill of the open water with unparalleled comfort and tailored craftsmanship. Whether you are cruising the coastlines or anchored in serene bays, your ArrowCat power catamaran is your gateway to a life of adventure and tranquility.
We intentionally designed this model to be simple and plain – simple to take the boat out, simple to use and to maintain, plain by allowing you the flexibility to customize it according to your preferences.
This 20-foot center console is built with strength and purpose, designed for ease and simplicity. Effortlessly take it out on the water, and enjoy straightforward maintenance and operation. Its clean, adaptable design allows for extensive customization, whether on your own or through a dealer.
Fully Planing Hull Design LOA: 19′ 4″ / 5.89 meters Beam: 8′ 4″ / 2.54 meters Draft: 10″ / 0.254 meters
Perfect for inshore and offshore cruising, long distance and overnight trips, cold off seasons and hot boating seasons, and much more. The ArrowCat 32-foot and 42-foot models provide an exciting and versatile experience on the water. Explore to see which one could best suit your boating lifestyle.
Merging express cruiser elegance with catamaran stability, the ArrowCat 320 Coupe features a planing hull design for smooth, swift rides. Powered by twin outboard motors, it promises dynamic performance and exhilarating adventures on every voyage.
Standard Layout: 2 Cabins/ 1 Wet Head Optional Tower Option LOA: 31′ 2″ / 9.5 meters Beam: 10’ / 3.05 meters Draft: 20″ / 0.508 meters
The ArrowCat 420 Coupe combines the luxury of an express cruiser yacht with the stability of a catamaran hull. Designed with a planing hull for agile, efficient navigation and powered by twin outboard motors, it delivers unmatched performance for your ocean adventures.
Standard Layout: 2 Cabins/ 1 Full Head LOA: 41′ 9″ / 12.73 meters Beam: 14′ 9″ / 4.50 meters Draft: 18″ / 0.46 meters
This luxury express cruiser yacht boasts a catamaran hull for superior stability and a planing hull design that ensures efficient, agile handling. Powered by twin outboard motors, it offers robust performance. The addition of a flybridge enhances your view and enjoyment, making every journey unforgettable.
Standard Layout: 2 Cabins/ 1 Full Head LOA: 41′ 9″ / 12.73 meters Beam: 14′ 9″ / 4.50 meters Draft: 20″ / 0.51 meters
Enjoy your boat year-round and stay warm and dry during cooler weather or overnight trips, while also having a comfortable and private space to retreat for whenever you need a break. Here are a few reasons why an ArrowCat power cat is an excellent boat to consider.
Catamarans have two hulls, which provide more stability in the water. They are less likely to roll or pitch, which means they offer a more comfortable ride, especially in rough conditions and for people who are prone to seasickness.
Power catamarans are typically more fuel-efficient than monohull boats of the same size. It requires less energy and yields more performance per HP. The two hulls create little to no drag or resistance to get on plane, resulting in greater fuel economy. Allowing for longer journeys with fewer refueling stops.
Power catamarans have a shallow draft which means they can navigate diverse cruising grounds – beaches, islands, rivers, channels, and coastal areas with limited water depth.
Cabin boats are designed with comfortable sleeping quarters and living spaces. They feature a sleeping space with a bed, a galley with a stove, sink, and refrigerator, and a head with a shower and toilet.
Cabin boats provide protection from the elements, such as wind, sun, and rain. This allows for comfortable cruising in a variety of weather conditions, as well as providing a haven during storms
Express cruisers are designed for efficient and fast navigation, offering higher speeds compared to traditional cruising boats. They usually have powerful engines that enable them to cover long distances quickly, making them ideal for day trips or weekend getaways.
Outboard motors can provide excellent performance and speed. They can often reach higher speeds than inboard motors of the same horsepower.
Outboard motors have a simple and standard design and are relatively easy to install, they do not require additional components such as a transmission, propeller shaft, couplings, and struts, that inboard engines do. They are easily assessable and cost less to maintain than inboard motors because they are mounted outside at the rear of the boat.
Outboard motors are often designed with features that make them easy to maneuver. For example, they can be tilted or rotated to provide precise control and handling in tight spaces and shallower waters.
Crafting Versatility and Adventure on the Water Since 2008
At ArrowCat, we believe in creating boats that are ready for anything. Our American-owned company builds versatile, multi-functional catamarans designed not just for a specific activity, but for a lifestyle that demands freedom and reliability. Whether you’re cruising, fishing, or exploring, our boats deliver superior performance in all conditions.
Trusted by seasoned mariners across coastal and saltwater environments, ArrowCat power catamarans embody the spirit of adventure and the promise of quality.
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Discover the unparalleled stability and speed of an ArrowCat power catamaran. Connect with our experts to schedule your sea trial today and experience the thrill firsthand.
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Discussion in ' Powerboats ' started by johnnythefish , Feb 23, 2024 .
For a given boat length - let us say 26 foot - and all else the same in terms of the boats payload, will a planning cat be more or less fuel efficient than an “average” planing mono hull at non-planning speed? Let us say 8kts. In the same vein how much more efficient is a displacement or semi-displacement catamaran (basically a catamaran not designed for very high speeds) compared to its planning catamaran counterpart at these speeds (8kts). I know that it is very hard to compare apple with apples here but I want to understand whether “the equivalent” planning catamaran is better than a mono hull in terms of fuel efficiency at these speeds; or if real efficiency gains at these speeds only happen with a displacement cat hull.
johnnythefish said: ↑ For a given boat length - let us say 26 foot - and all else the same in terms of the boats payload, will a planning cat be more or less fuel efficient than an “average” planing mono hull at non-planning speed? Let us say 8kts. Click to expand...
What load? You need to be very specific. The relative performance is very sensitive to weight. Catamarans always have a lot more wetted surface area, which is bad 100 percent of the time. But they make less waves at some speeds, and can be tuned to have small wave losses at a narrow band of speeds. So they can be better at least some of the time for some displacements. Note that cats have a considerably lower payload percentage. If you are trying to build a boat around a specific load, the monohull is at a significant advantage because the craft will be lighter overall. But 8 knots is a really awkward speed for any 26'er with any weight to her.
I started a reply and lost it. The problem with the question is the premise is false. All else cannot be equal. The planing cat, offers more stability with wider beam, for a theoretical similar displacement and waterplane. The problem for you is you have left too much detail out of the query. If you want a high speed trolling platform; running at 6-8 kts is not efficient in many monohulls. The flipside is the monohulls allow for lotsa passengers and lotsa gear, but they are going to be doing poorly at that speed. The best way to fight this issue is a cat that is bigger than 26'. Of course, this is a classic OPM by me. @DogCavalry would tell you to build a 26' Seasled, but he still can't get into 15' of beam. DM me please as I have some private issues to mention. Let the group know a bit more about the plan and remember, in boats, ceteris parabis is mythical.
@johnnythefish , I'm going to echo the other fellows. Not enough information here to answer your question. The biggest thing missing is how much weight you want to carry. Then what sort of conditions you'd like to be safe in. @fallguy has obliquely hinted that I might like sea sleds. This is my 26' sea sled named Serenity. To save fuel I typically cruise at 5 knots, which requires 12 hp. But that's with 800# of people and beer and snax on board. I've done 15 knots with 3500# of cargo aboard, at 150hp. Or 32 knots with #700 at 250hp. I expect to seriously improve that last number, now that I have the prop @baeckmo recommended. As far as lumpy water goes, I've been out drinking a coffee from a regular cup, and been interrupted by a phone call from a watcher on shore to let me know that if I sank they'd have to watch, because their boat couldn't leave the dock under those conditions. I'm not sure where @fallguy got 15' beam from. I stopped at 10' but she's already stable enough. @Ad Hoc was kind enough to run the hydrostatics for me. Posted on my thread back in 21/08/07. More stable than a flat bottom barge. This is almost certainly TMI, but the question was raised. And it's an opportunity to praise the fine gentlemen who generously help folks on here who are willing to be helped.
Firstly - thank you for all the responses. @DogCavalry nice looking sled - where can I find more info on this concept. How does the sled do at 8kts? Let me try and define my parameters more specifically and let’s do aside with the comparison between a mono hull and a catamaran altogether and ask this instead…. At 8 Kts, how much more efficient will a “displacement” catamaran of 26 foot in length be than a planing catamaran if the beam are the same (can be more than trailerable width and no limit on how wide). The boat must carry 6 adult men, fishing tackle and enough food, fuel and water for an overnight; accommodation can be sparse and minimalistic; basically boat does not need the kitchen sink. More space obviously is preferable but not paramount. Weather conditions are warm and balmy. No chance of rain. Sleeping accommodation can be a mattress on deck that rolls up. Shade is important. The vessel will need to cover 80 miles as fast as possible given it’s design limitations. Faster is better but not to the detriment of the overall fuel economy so long as a minimum speed between of 16 mph can be maintained. The vessel must then travel 160 miles at 8kts. Sea conditions can range from flat calm to large swell and/ and or wind driven chop. Water is tropical.
Your issue with any boat, is most planing boats at 26' are not "out of the hole" at 6-8 kts. What you are really asking is what designs are more efficient at speeds of 6-8 kts. There are semi-displacement monohulls and cats. The cat can offer a more stable fishing platform, but make no mistake, building a cat is more difficult. Two hulls, beams and a bdeck, engines on each. It all depends on how much wirk you are in for for a more stable platform. A 30' cat can probably get into 15' beam which would be an advantage over the Sea Sled. Maybe 13.5 for a 26'er. But everything gets spendy, too. More cables, two start batteries, long cables to the helm. So, I recommend you find some semi-displacement monohulls that will do well at 7 kts (not in a hole), and wide enough for a nice fishing platform. The reason for semi-planing vs displacement is the speed desired and ability to take a 6 pak a farther distance than displacement.
I noticed you had the same type of thread going awhile back. I picked a boat for you. The Bluejacket 28. But make the cabin smaller and the cockpit bigger. This will shift lcg for'd some, so you'll need to accomodate the change somehow. Bluejacket 28 – Bluejacket Boats https://bluejacketboats.com/bluejacket-28/ The Bluejacket 27 is a better design for fishing; not sure if it has a head onboard. On further, probably not big enough in available displacement for a 6 pack, but close. Gonna be hard to find a 26' cat to accomodate a 6 pack as well...
johnnythefish said: ↑ Firstly - thank you for all the responses. @DogCavalry nice looking sled - where can I find more info on this concept. How does the sled do at 8kt? Click to expand...
The one issue with the Sea Sled, is a massive fishing cockpit might mean lcg is too far forward. I'll let John remark more.
Like yours? My LCG is too far forward because I built the bow super massive to carry an actual ton of material in the forward cockpit, or to push a ten ton barge with the bow. Both of those things are job related, so I'm fine with them. With the throttle at 15%, the bow pops up, and she's planing at about 3° with respect to the twin keels, or 6° with respect to the apex of the tunnel. So that's fine. Her drag is too high from huge wetted surface, if I was always running light. It's not the most efficient form. But I carry heavy stuff, and for that I think it's as good as there is.
DogCavalry said: ↑ Like yours? My LCG is too far forward because I built the bow super massive to carry an actual ton of material in the forward cockpit, or to push a ten ton barge with the bow. Both of those things are job related, so I'm fine with them. With the throttle at 15%, the bow pops up, and she's planing at about 3° with respect to the twin keels, or 6° with respect to the apex of the tunnel. So that's fine. Her drag is too high from huge wetted surface, if I was always running light. It's not the most efficient form. But I carry heavy stuff, and for that I think it's as good as there is. Click to expand...
I built the sides of the forward cockpit much too high for convenient fishing. I honestly never thought of it. I was thinking of keeping kids inside and water out, but folks regularly ask me about fishing, so I thinking I pooched that one. I just prioritized wrong.
If you’re into offshore fishing or water sports, the Power Catamaran or “multi-hull powerboat” offers you a great option for your first vessel. These powerboats provide you an excellent combination of performance, stability, and maneuverability.
These boats have a catamaran design, relying on two hulls to float the vessel instead of the typical deep-V hull found on other powerboat models. The multi-hull powerboat is ideal for cruising, and you can set it up for fishing or watersports as well.
With the multi-hull powerboat, you get options for multiple fishing stations over each hull without disrupting the boat’s balance on the water. They are ideal for use in lakes and estuaries, and they excel on the open ocean.
These boats come in lengths ranging from 16 to 30-feet, with plenty of customizable options and accessories. Typically, you get a stern-drive or outboard motor configuration, with center consoles for the driver and loads of storage space onboard.
These boats can carry from six to eight passengers easily, and most models will fit on trailers. This post gives you all the information you need on selecting the right multi-hull powerboat to suit your aquatic needs.
The multi-hull powerboat features a catamaran design, with two hulls running down the boat’s length, featuring a gap between the two. This configuration makes the boat exceptionally stable at higher speeds, allowing fast movement through choppy water inshore or offshore.
The catamaran might seem like a niche boat design. However, it offers you several advantages on the water, such as a smooth ride, stability, and economy. These boats come in a wide range of designs and lengths, with the smallest versions measuring around 12-feet, and the largest extending up to 70-feet or longer.
The longer vessels come with liveaboard facilities and all the amenities you need to spend days out on the water. We like to think of the multi-hull powerboat as the catamaran design of the cabin cruiser or cuddy cabin boat. You get all the same advantages as these models but with an added performance on the water.
You get plenty of options for live wells, rod holders, gear storage, and integrated coolers for drinks and fish. Whether you’re planning a weekend trip or just going out for the day, the multi-hull powerboat is a great choice for your ocean-going excursion.
While the catamaran model is the most popular choice in this category, there are models featuring a tri-hull design. Typically, these vessels cater more towards fishing than performance or watersports, offering slightly less steering maneuverability than the dual hull setup. However, the addition of the third hull brings superior stability to the boat, making them ideal for fishing in choppy water or cruising from island to island on rougher seas.
The ripple hull models typically feature more liveaboard space, with some models having multiple separate living areas beneath the deck.
The Multi-hull powerboat offers you plenty of advantages for fishing, cruising, and watersports. Here are our top reasons for adding this boat to your shortlist of considerations.
The multi-hull boat relies on two separate hulls contacting the water. As a result, there is less drag from the hull when cutting through the water. You get faster speeds than you do with a mono-hull design and excellent handling with tight turning circles. These boats do well on open water, allowing for superior stability in rough waters when fishing offshore.
The multi-hull powerboat features dynamic cruising capability. These boats are most popular with recreational users that want to cruise down the coastline on the weekend or take a few days out on the water for a fishing trip. The built-in accommodations in many designs make it suitable for staying out on the water overnight.
Multi-hull powerboats can come with several engine configurations. The motors on these boats offer excellent performance, propelling the watercraft up to speeds of 50 to 80-mph, depending on the model. They also make suitable watersports boats, allowing for skiing and wakeboarding.
The multi-hull boat offers you more storage capability than mono-hull models. You get loads of storage room above and below deck for your dive gear or fishing equipment. There is under-seat storage, and the v-berths in the bow of these models can include plenty of amenities.
The center console driver configuration is common with the multi-hull performance boat. This driver position gives you more control over the vessel when turning. Some consoles may position closer to the bow or aft of the boat, depending on the length and design features of the boat.
Most multi-hull powerboats come equipped for long ocean-going trips. As a result, they may have a covered driver cockpit leading to below deck accommodations or storage facilities. Some models have wraparound cockpits with doors sealing the cabin, allowing for air conditioning inside the boat on hot days. Other models come with an open plan design and a hard roof.
Most models of multi-hull power bats range from 16 to 24-feet, but there are plenty of longer models. The shorter lengths are easy to trailer, allowing for easy removal for the water and transportation. However, some models may be wider than 10-feet, requiring a special license to operate the loaded trailer. Check with your local authorities for trailer regulations and laws.
These boats are excellent fishing vessels, offering you plenty of stability for casting on any side of the boat. The center console design means you have walkways on either side of the console, allowing the angler to chase the fish around the boat if it decides to drag the line. Most models also feature setups for watersports like wakeboarding, with T-tower bars or Bimini tops for higher tow points.
The multi-hull powerboat comes with a design for performance out on the water. As a result, these boats usually feature outboard motors with capacities ranging from 150-HP to 450-HP. Some models may use dual-motor setups or stern-mounted motors that hide out of sight.
As mentioned, the multi-hull boat comes in a variety of lengths to suit your requirements. Whether you need a large boat for spending days out on the water or a simple day fishing vessel, there’s a multi-hull design to suit your requirements.
While the multi-hull powerboat is a flexible design suited for cruising, fishing, or water sports, it does come with a few drawbacks.
These boats feature design and construction for speed, with large outboard motors. As a result, they are somewhat heavy on fuel, especially with a large-capacity dual-motor setup.
You have plenty of choices when selecting your multi-hull powerboat. Here are some of our top picks for the best models available.
This multi-hull powerboat has a 51-foot length, and it’s ideal for offshore use, providing exceptional stability thanks to the size and the 17-foot beam. It’s one of the largest models available, featuring world-class multi-hull design.
You get a spacious deck with a center console configuration and enough room to walk down either side of the boat when fishing. The dual hull provides exceptional stability combined with the long length, and you get options for diesel-powered or gasoline engines in outboard or in-stern setup to suit your requirements.
The Calcutta brand custom-builds boats for its clients. You get options for fully enclosed bow areas and fishing-style cabins with a roomy helm deck and a sleeping berth included in the bow. You also have an enclosed head for ablutions, but there is no option for a shower.
This model comes with an enclosed cockpit and air conditioning to keep you cool when cruising. The motors on this boat are monsters, featuring a twin setup of 550-HP Cummins diesel inboards available on the sports version for superior power and speed on the water while maintaining the boat’s maneuverability.
There’s a 600-gallon fuel capacity for the thirsty engines, allowing you to spend days out on the water without running out of fuel.
The Insetta 35 IFC hydrofoil offers you the smooth-sailing benefit of hydrofoils, with premium multi-hull designs. The hydrofoil system generates the lift under the hull, allowing for superior, stable sailing in rough water conditions.
The hydrofoil reduces friction and dragging on the hulls, reducing your fuel consumption by as much as 40% compared to other models with a similar dual hull design. The foil fits between the sponsons, featuring design and construction with stainless steel.
Another interesting design feature with this model is the way the inboard motors have positioning towards each other. This configuration allows for maximum thrust for the propellors on the asymmetrical multi-hull.
The foil and motor setup design also allow for much tighter turns than you get with other multi-hull models, giving you similar performance to what you expect in a mono-hull design.
The boat comes with a large coffin box with 156-gallons of space available and an insulated finish. You get eight rod-holders positioned in the bow and aft of the boat. You also get dual 30-gallon transom live wells and an option for a third below the mezzanine seat.
The Insetta 35 IFC hydrofoil comes with a three-pump sea chest, a folding bait station, and plenty of tackle storage. The boat gets its power and performance from dual Mercury 400 Verados, with the vessel topping out at speeds of 58-mph on open, calm waters.
This model is the largest in the Invincible range, and it’s a great choice for offshore fishing. This flagship model comes with a 42-foot length and a center console design for easy driver operation. This multi-hull powerboat relies on a hybrid semi-asymmetrical multi-hull giving it great turning capability and maneuverability out on the open water.
The Invincible 46 Cat features a stepped hull with fast acceleration and plenty of lift. You get a quad engine setup with Mercury 450 Racing outboard motors, and the craft can reach a top-end speed of 78-mph. Other notable features of this boat include a vacuum-infused hull and grid-stringer system for an “invincible” boat that’s virtually unsinkable.
If you’re looking for a luxury powercat model, the Bali Catspace Motoryacht is a fantastic – but expensive choice. This model features a design from legendary boat maker Olivier Poncin. This model is a natural cruiser and ideal for the longest ocean-going trips.
The dual hull and high ride height from the water provide exceptional stability for the boat, even in the roughest offshore and coastal waters. The boat comes with a lounge on the deck, and there’s plenty of room around the center console cabin to walk the length of the boat on either side of the vessel. The top level of the boat features the captain’s station and wheelhouse, with luxury living quarters underneath.
You get a huge lounge and a v-berth with sleeping quarters for spending the night out on the water. The cockpit presents the captain with a 360-degree view of the water, and the high riding position gives you a view of the ocean that extends for miles.
The boat comes with all the amenities you need, including tables, a full kitchenette, and luxury sleeping accommodations. There are plenty of entertainment options for TVs and stereo systems down below, with an optional hardtop Bimini.
The Bali Catspace Motoryacht receives its power from a single or dual engine setup featuring 150-HP or 250-HP Yamaha motors.
With so much variety available in multi-hull powerboats, you have options for any activity out on the water. These boats are more common in coastal waters, and they make excellent fishing vessels.
Decide on the model that suits your activity, as most have a purpose-built design for fishing, watersports, or cruising. There are plenty of customization options, so make sure you keep a budget in mind as the additions can cost more than 20% of the boat’s initial sticker price, increasing your costs.
John is an experienced journalist and veteran boater. He heads up the content team at BoatingBeast and aims to share his many years experience of the marine world with our readers.
A complete guide to narrow boats: all you need to know, a guide to aluminum fishing boats.
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Before going into the advantages of catamarans, I’d just like to define the term. Catamarans are a class of boat that has two hulls, generally equal in size. The hulls are connected by a structure of some sort. Catamaran hull speeds are very high, making them a good choice for recreational uses. Catamaran sailboats are common, but catamaran ferry designs are quickly growing in popularity due to their unique advantages.
The catamaran is a ship design with an interesting history. The twin-hull design was first observed by Europeans in India in the late 17th century, but it was actually invented by South Pacific islanders. The capabilities of catamarans were more or less ignored in the West until 1877, when an American named Nathanael Herreshoff began developing and racing catamarans. His designs were so much faster than traditional monohull designs that sailing authorities banned them from competition for nearly a century. Today, catamarans are a popular design for recreational and racing sailboats, and are being used in efficient, low-wake ferries .
Image: Flickr , Catamaran in Cozumel.
Catamarans are, in general, faster than single hull boats. This is due to several factors, the most important of which is the hull shape. Displacement hulls are the most common shapes for single hull craft. A displacement hull is supported on the water entirely by buoyancy effects. This creates a hydrodynamic drag barrier, which slows the craft. Catamaran hulls can be designed as planing or displacement hulls, but they are not slowed nearly as much by the drag barrier. Catamarans reduce drag by making use of a very thin and pointed hull design.
Catamarans are also very light, which further reduces drag and displacement. Catamarans save on weight because the multihull design eliminates the need for a keel counterweight, as the same purpose (righting the ship) is served by the hull spacing. This can make them difficult to turn, however.
Catamarans are also more stable than monohull ships, enabling designers to use more sail per foot of the boat. Stability comes from the wide beam legth; beam length is the distance from one side of the boat to the other. This wide beam and stability also allows catamarans to gain more power from heavy gusts, because they do not tend to heel over like monohulls do.
More efficient single hull boats are designed to travel with a low Froude number, which reduces but does not eliminate the drag barrier. This drag limits hull speed based on a relation involving length at waterline, given by the formula V=(gL/(2pi))1/2, where g is the gravitational constant and L is the waterline length. This is the theoretical limit for single hull displacement craft. Note that ships can sometimes exceed this theoretical limit, but to do so requires a very large power source.
The calculations for a catamaran are more complicated. The formula for catamaran hull speed is 1.34*(wetted length)1/2; however, this drag formula is generally not the limiting factor for catamaran hull speed. This is because boats with waterline length to beam ratios greater than 8:1 are not limited by hydrodynamic drag factors, whereas smaller boats need to plane to do so (planing requires enormous amounts of power for displacement hulls). A more important factor to consider is the prismatic coefficient, Cp. Cp = V/(LBP*Am), where V is the volume of water displaced by the hull, LBP is the length between perpendiculars, and Am is the area at midship.
Very fast boats actually require a high prismatic coefficient, which in turn requires a less-narrow boat. However, narrower hulls can get away with a lower prismatic coefficient. The ideal range of Cp for a catamaran is between 0.61 and 0.65. There are a few ways of increasing the prismatic coefficients: sailors can use bulb bows, a wide planing aft segment, or a flat hull rocker in conjunction with a bustle aft. Though high prismatic coefficients increase drag at low speed, at high speeds they can reduce drag by as much as ten percent.
As explained here , catamarans can be used to create low-wake ferries. Because of their wide bows and low weights, catamarans can be made to travel quickly with minimal wake. Catamaran ferries are also more fuel-efficient, because of the previously-mentioned factors.
Image Credit: Wikimedia Commons , Catamaran Ferry
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A catamaran hull is much like a frigate hull (similar SLR, L/B ratios and Froude numbers) and there is plenty of data available for those. There is also a lot of data for the round bilge narrow non planing motorboats popular in the 1930'-50's which again are similar to a single multihull hull.
Mike Myers, vice president of product development for World Cat explains: "Catamaran hulls experience little to no drag or resistance to get on plane, resulting in greater fuel economy. They have a steady rise in speed and fuel burn with little to no spikes in fuel consumption."Planing powercats have a unique trait — which many cat lovers ...
Instead, catamaran planing pads act like a lifting strake, which allows planing at lower speeds. The key to a great planing surface is the perfect balance of size, proportions, distribution, and how far forward on the hull it extends from the transom. Tunnel Considerations
Planing boats are designed to rise up and glide on the water when enough power is applied. Whether you're in the market to buy a planing boat or you want to ...
The planing hull catamarans that have been designed, built and sailed have usually had stepped hull shapes based on the floats of water planes. I guess Yves Parliers boat is the most famous of these. They claim it worked very well under the right conditions until it crashed and burned. Gareth. grob,May 22, 2006.
A discussion about catamaran hull shapes and how they relate to performance and sea keeping with specific reference to the 33' catamaran Mad Max. ... possibly promoting some planing effect. If we had a more even rocker line we would slightly reduce the wetted area, but we would increase the pitching and the water would exit the hull aft at a ...
Figure 2.4 - Typical Planing hull - a) Side view b) Mid-ship station c) Top View. ... An existing hull shape of a sailing catamaran currently being produced in South Africa could be used, or a standard hull shape of suitable characteristics could be used. In either case, a representative hull shape would need to be found in order to determine ...
This will be your calculated maximum hull speed for a semi-displacement catamaran. The Formula. First of all, we need to know the maximum hull speed for a displacement hull, and from that number, we will be able to calculate how much faster the semi-planing (or semi-displacement) hull will be. This is the formula for Maximum Hull Speed on a ...
Catamaran Hull. The catamaran is similar to the pontoon hull (read on to learn more on that one), but it is a displacement multihull instead of a planing one. So it has two hulls, that lie inside the water and displace it. Like the pontoon, you will have to try really hard to capsize this design (and it won't work). Examples: well, catamaran ...
A 1:4 scale model of planing catamaran hull has been built and the geometry of the planing catamaran in this study is shown in Fig. 1.And the main parameters of this catamaran are presented in Table 1.The hull is divided into two demi-hulls arranged aside by a tunnel, so this kind of planing catamaran is also named tunneled planing hull (Roshan et al., 2020).
T c = 0.57. Here we put B TR = 1.9 to minimize boat resistance (for her size) and get the draft calculation for a canoe body T c (Figure 1). Midship coefficient - C m. C m = A m / T c (x) B WL. We need to estimate a few coefficients of the canoe body. where A m is the maximum cross section area of the hull (Figure 3).
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. ... Catamarans can. There are cats out there with wide and flat aft hull sections ...
Boats moving at high speeds operate in the planing mode when the hydrodynamic lift on their hulls overcomes the hydrostatic lift. To improve lateral stability of such boats and to increase available deck space, twin-hull arrangements are often implemented (Fig. 1).The hydrodynamic interaction between hulls operating in a proximity to each other can be significant and needs to be accounted for ...
The majority of today's catamarans feature planing hulls—designed to rise up on top of the water—rather than displacement hulls, which plow through the water. They can have asymmetrical or symmetrical sponsons. The former focuses more on forcing air down through the tunnel to create lift, says Rob Coffey, director of sales and marketing ...
Catamarans generally have significantly greater planing characteristics than comparably sized monohulls. Factors in design: Distribution of deadrise (angle at which hull departs from centerline on hull): shifts from 35° in bow to 12° amidships, with the planing surface at transom. Shape of chines (deflects water in front; lifting surface aft).
There are automatic generation codes for the stepped planing hulls or catamarans and this is an area where emerging knowledge from computer science can be employed (see Section 10.1.2). Table 3 . Different methods developed for parametric generation of semi-planing and planing hulls (This table is originally presented in Khan et al. (2017) ).
Planing Catamaran The planing cat's ride is still rough compared to dis-placement cats, but better than on a planing single hull boat. The top speed of these craft again are only dependant on the amount of power applied. Oddly, power needed, and efficiency are not much better than single hull planing craft, at planing speeds. Below
ArrowCat 320. Merging express cruiser elegance with catamaran stability, the ArrowCat 320 Coupe features a planing hull design for smooth, swift rides. Powered by twin outboard motors, it promises dynamic performance and exhilarating adventures on every voyage. Standard Layout: 2 Cabins/ 1 Wet Head. Optional Tower Option. LOA: 31′ 2″ / 9.5 ...
A short, fat hull (like a Formula board which is 3' wide and about 7' long) is very inefficient at low speeds but if you can summon the power to drive it fast enough to reach its planing threshold, it abruptly starts to plane at lower speeds and more efficiently than the long skinny hull. The jump from "displacement" to planing speeds and vice ...
At 8 Kts, how much more efficient will a "displacement" catamaran of 26 foot in length be than a planing catamaran if the beam are the same (can be more than trailerable width and no limit on how wide). The boat must carry 6 adult men, fishing tackle and enough food, fuel and water for an overnight; accommodation can be sparse and ...
In catamaran planing, we found that the hull resistance decreased by 7.8% at the 30° deadrise angle compared to the most significant resistance at other angles. Geometric scheme of the deadrise ...
The multi-hull powerboat features a catamaran design, with two hulls running down the boat's length, featuring a gap between the two. ... Whether you're planning a weekend trip or just going out for the day, the multi-hull powerboat is a great choice for your ocean-going excursion. While the catamaran model is the most popular choice in ...
Catamaran hulls can be designed as planing or displacement hulls, but they are not slowed nearly as much by the drag barrier. Catamarans reduce drag by making use of a very thin and pointed hull design. Catamarans are also very light, which further reduces drag and displacement. Catamarans save on weight because the multihull design eliminates ...
The red twin-hull catamaran in the images and video above is Safehaven's new T-2000 Voyager, a 20-m (66-ft), long-range, high-performance, semi-wave piercing explorer boat capable of speeds over ...