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Catamaran Hull Design

  • Post author By Rick
  • Post date June 29, 2010
  • 2 Comments on Catamaran Hull Design

efficient catamaran hull design

Part 1: Notes from Richard Woods

Since the America’s Cup experimented with going multihull, there’s been a lot of interest in catamaran performance and the catamaran hull designs that define performance. Many guys are investigating whether to buy a catamaran or design and build their dream boat. Let it be said here that building a large catamaran is not for the faint of heart. People begin building 100s of boats a year, yet few are ever completed, as life always seems to have a way of interfering with a good boat build. 

Never the less, since the rest of this website is about selecting and buying a boat , it only seems fair to have at least one webpage that covers catamaran design. This page contains notes on boat hull design goals and an accompanying page from Terho Halme has mathematical formulas used in actual catamaran hull design. It has become a popular research stop and an important reference to the catamaran design community.

The content of this page was reproduced from the maestro of Catamaran designs, renown British naval architect, Richard Woods, who not only designs catamarans, he sails them across oceans…. repeatedly. He has a lot to say on the subject of catamaran hull design.

“…When it’ all said and done, the performance of a sailing catamaran is dependent on three primary specs: length, sail area and weight. If the boat is longer it generally means it’ a faster boat. If she has more sail area, it means she’ a faster boat and if she’ light it means she’ a faster boat.  Of course, there are limits: Too much sail area capsizes the boat in brisk winds. If the boat is designed too light, she will not take any kind of punishment. Too slim a hull design and the boat becomes a large Hobie Cat capable of only carrying your lunch. Of course, too long and large and you’d have to be Bill Gates to afford one. Then there are lot of additional and very important factors like underwater hull shape, aspect ratios of boards and sails, wet deck clearance, rotating or fixed rigging and so on….” Richard Woods

All Catamarans are not equal, but all sailboats have two things in common: They travel on water and they’re wind powered, so the Catamaran design equations in the 2nd part should apply to every catamaran from a heavy cruising Cat to a true ocean racer.

Richard Wood’s comments on catamaran design:

We all know that multihulls can be made faster by making them longer or lighter or by adding more sail. Those factors are the most important and why they are used as the basis of most rating rules. However using just those figures is a bit like determining a cars performance just by its hp and curbside weight. It would also imply that a Tornado would sail as fast forwards as backwards (OK, I know I just wrote that a Catalac went faster backwards than forwards)

So what next?? Weight and length can be combined into the Slenderness Ratio (SLR). But since most multihulls have similar Depth/WL beam ratios you can pretty much say the SLR equates to the LWL/BWL ratio. Typically this will be 8-10:1 for a slow cruising catamaran (or the main hull of most trimarans), 12-14:1 for a performance cruiser and 20:1 for an extreme racer.

So by and large faster boats have finer hulls. But the wetted surface area (WSA) increases proportionately as fineness increases (for a given displacement the half orange shape gives the least WSA) so fine hulls tend to be slower in low wind speeds.

The most important catamaran design hull shape factor, is the Prismatic Coefficient (Cp). This is a measure of the fullness of the ends of the hull. Instinctively you might think that fine ends would be faster as they would “cut through the water better”. But in fact you want a high Cp for high speeds. However everything is interrelated. If you have fine hulls you can use a lower Cp. Most monohulls have a Cp of 0.55- 0.57. And that is about right for displacement speeds.

However the key to Catamaran design is you need a higher Cp if you want to sail fast. So a multihull should be at least 0.61 and a heavy displacement multihull a bit higher still. It is difficult to get much over 0.67 without a very distorted hull shape or one with excessive WSA. So all multihulls should have a Cp between 0.61 and 0.65. None of this is very special or new. It has been well known by naval architects for at least 50 years.

There are various ways of achieving a high Cp. You could fit bulb bows (as Lock Crowther did). Note this bow is a bit different from those seen on ships (which work at very specific hull speeds – which are very low for their LOA). But one problem with them is that these tend to slam in a seaway. 

Another way is to have a very wide planing aft section. But that can increase WSA and leads to other problems I’ll mention in a minute. Finally you can flatten out the hull rocker (the keel shape seen from the side) and add a bustle aft. That is the approach I use, in part because that adds displacement aft, just where it is most needed.

I agree that a high Cp increases drag at low speeds. But at speeds over hull speed drag decreases dramatically on a high Cp boat relative to one with a low Cp. With the correct Cp drag can be reduced by over 10%. In other words you will go 10% faster (and that is a lot!) in the same wind and with the same sails as a boat with a unfavorable Cp. In light winds it is easy to overcome the extra drag because you have lots of stability and so can fly extra light weather sails.

The time you really need a high Cp boat is when beating to windward in a big sea. Then you don’t have the stability and really want to get to your destination fast. At least I do, I don’t mind slowly drifting along in a calm. But I hate “windward bashing”

But when you sail to windward the boat pitches. The sea isn’t like a test tank or a computer program. And here I agree with Evan. Immersed transoms will slow you down (that is why I use a narrower transom than most designers).

I also agree with Evan (and why not, he knows more about Volvo 60 design than nearly anyone else on the planet) in that I don’t think you should compare a catamaran hull to a monohull, even a racing one. Why chose a Volvo 60/Vendee boat with an immersed transom? Why not chose a 60ft Americas Cup boat with a narrow out of the water transom?? 

To be honest I haven’t use Michelet so cannot really comment. But I have tested model catamarans in a big test tank and I know how inaccurate tank test results can be. I cannot believe that a computer program will be better.

It would be easy to prove one way or the other though. 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.

One of the key findings I discovered with my tank test work was just how great the drag was due to wave interference between the hulls. Even a catamaran with a modern wide hull spacing had a drag increase of up to 20 % when compared to hulls at infinite spacing. One reason why just flying a hull is fast (the Cp increases when you do as well, which also helps). So you cannot just double the drag of a single hull and expect to get accurate results. And any speed prediction formula must include a windage factor if it is to give meaningful results.About 25 years ago we sailed two identical 24ft Striders next to each other. They were the same speed. Then we moved the crew of one boat to the bow. That boat IMMEDIATELY went ½ knot faster. That is why I now arrange the deck layout of my racing boats so that the crew can stay in front of the mast at all times, even when tacking or using the spinnaker.

I once raced against a bridge deck cabin catamaran whose skipper kept the 5 crew on the forward netting beam the whole race. He won.

Richard Woods of Woods Designs www.sailingcatamarans.com

  • Tags Buying Advice , Catamaran Designers

Rick

Owner of a Catalac 8M and Catamaransite webmaster.

2 replies on “Catamaran Hull Design”

I totally agree with what you say. But Uli only talk sailing catamarans.

If only solar power. You need the very best. As limited watts. Hp.

The closer to 1-20 the better.

Closing the hulls to fit in cheaper marina berth. ?

You say not too close. But is that for sailing only.

Any comment is greatly appreciated

Kind regards Jeppe

Superb article

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Catamaran hull design plans

Power catamaran hull design - displacement catamaran.

  • Mechanical engineering

Catamaran hull design

Welcome to our comprehensive guide on catamaran hull design! Whether you're a seasoned sailor or a novice enthusiast, understanding the intricacies of catamaran hull designs is essential for optimizing your boating experience. 

Advantages of Catamaran Hull Design: Catamarans have gained immense popularity due to their unique attributes. The asymmetrical catamaran hull design offers enhanced stability, greater maneuverability, and increased speed on the water. Unlike traditional displacement hulls, which tend to plow through the water, catamarans slice through waves with minimal resistance, providing a smooth and efficient ride.

Displacement Catamaran Hull Design: Displacement catamaran hull designs combine the benefits of displacement hulls with the efficiency of catamarans. These designs excel at maintaining stability, even in rough waters. They offer spacious interiors, making them ideal for long journeys, liveaboards, or recreational outings.

Power Catamaran Hull Design: Power catamaran hull designs are tailored for speed and performance. They integrate sleek contours and streamlined shapes to minimize drag, allowing power catamarans to achieve remarkable speeds while consuming less fuel. These designs are favored by those who seek exhilarating water adventures.

Types of Boat Hull Designs: Boat hull designs encompass a wide range, from displacement hulls to planing hulls, each tailored to specific purposes. Whether you're looking for the most efficient, stable, or innovative hull design, our expert team can help you explore a variety of options to suit your needs.

Efficient Displacement Hull Design: Efficient displacement hull designs prioritize fuel efficiency and smooth navigation. By cutting through the water rather than riding on its surface, these designs conserve energy and offer a serene on-water experience. Our hull design agency specializes in creating displacement hulls that balance performance with economy.

Hull Design Plans and Drafts: Our hull design co offers meticulously crafted catamaran hull design plans. From the initial hull design drawing to the final hull design draft, our team of skilled engineers ensures precision and attention to detail at every step. We're dedicated to bringing your ideal hull design concept to life.

Hull Form Design and Optimization: Hull form design and optimization are critical aspects of creating a successful catamaran hull. Our experienced hull design engineers employ cutting-edge techniques to ensure the ideal combination of stability, efficiency, and aesthetics in your boat's hull.

Stability and Safety: One of the key considerations in hull design for boats is stability. Our experts meticulously craft hull designs for stability, ensuring that your catamaran provides a secure and comfortable platform for your waterborne adventures.

Innovative Hull Designs: Looking for something fresh and innovative? Our design engineer hull team specializes in creating new hull design boats that push the boundaries of traditional design concepts. We merge artistry with functionality to offer you an exceptional catamaran hull like no other.

Whether you're intrigued by the advantages of an asymmetrical catamaran hull design, fascinated by efficient displacement hulls, or in pursuit of the most stable boat hull design, our hull design agency is committed to delivering top-tier designs tailored to your preferences. Contact us to embark on a journey of unparalleled boating excellence.

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Power Catamarans: A Complete Guide

Dec 06, 2023

less than a min

Power Catamarans: A Complete Guide

Power Catamarans, often termed as the epitome of modern maritime engineering, are gaining popularity for all the right reasons. Their distinct design, enhanced stability, and cruising efficiency set them apart from traditional monohull boats and even their sail-driven counterparts. This guide dives into the world of Power Catamarans, shedding light on their advantages and how they compare to other vessels like monohulls and trimarans.

Historical Prelude:

The concept of catamarans traces its roots back to ancient maritime cultures. However, the power catamaran is a relatively modern innovation that marries the traditional twin-hull design with powerful engines, offering a unique blend of speed, stability, and space.

Distinguishing Design:

Power Catamarans are characterized by their twin hulls, which significantly reduce the drag, thus enhancing speed and fuel efficiency. Unlike monohulls, they have a broader beam, which contributes to increased stability and more living space. The absence of a ballast for stability further lightens the vessel, contributing to its speed and fuel economy

Speed and Handling:

One of the significant advantages of power catamarans is their speed and handling. The twin hulls allow for a smoother glide over the water, making them particularly favorable for watersports enthusiasts. Their handling in rough waters is superior to monohulls, thanks to the inherent stability provided by the dual-hull design.

The stability of power catamarans is unparalleled, especially when compared to monohulls. The wide beam and twin hulls provide a stable platform, reducing the rocking and rolling common in monohulls. This stability is not only comforting in rough seas but also crucial when docking or anchoring.

Comfort and Space:

The spacious design of power catamarans offers homelike livability, with ample room for cabins, lounges, and even onboard amenities like grills and bars. The wide beam also allows for large deck spaces, ideal for sunbathing or enjoying the scenic ocean vistas.

Economy and Redundancy:

Power catamarans are economical, with fuel efficiency being one of their selling points. The redundancy built into their design, with separate engines for each hull, provides an added layer of safety, ensuring that the vessel can return to shore even if one engine fails.

Regular Upkeep and Care:

Power catamarans, given their unique design and structure, come with their own set of maintenance requirements. Like all boats, routine checks and upkeep are essential to ensure smooth sailing. The twin hull design means double the underwater gear – from propellers to rudders, which necessitates regular inspections for any signs of wear, tear, or fouling.

Antifouling:

Given that power catamarans have a larger surface area underwater due to their twin hulls, they may be more susceptible to marine growth. Regular antifouling treatments can help in keeping the hulls clean, ensuring optimal performance and fuel efficiency.

Engine Maintenance:

One distinct advantage of power catamarans is their dual-engine setup, but this also means double the engine maintenance. Regular oil changes, cooling system checks, and filter replacements are crucial. It's beneficial to synchronize maintenance schedules for both engines to ensure consistent performance.

The lifespan of a power catamaran largely depends on its build quality, materials used, and how well it's maintained. With proper care, a power catamaran can last for several decades. The engine's maintenance significantly impacts the catamaran's lifespan, with gasoline engines requiring maintenance at 1,200 to 1,800 hours and diesel engines at around 5,000 hours​​. The construction materials play a crucial role; for instance, fiberglass catamarans, when well-maintained, can last for many decades, while aluminum cats might change ownership after 10-15 years but can last a lifetime with proper care​.

World-Renowned Builders:

The power catamaran sector boasts several reputable manufacturers such as Lagoon, Leopard Catamarans, Fountaine Pajot, and other notable names like Seawind Catamarans​.

Lagoon, a revered name under the Beneteau Group umbrella, has carved its niche in crafting luxurious, spacious catamarans. A prime example is the Lagoon 630 Motor Yacht, embodying opulence with its nearly 250 sq. ft. aft deck and 900 sq. ft. interior, comfortably housing up to 12 guests. Known for its superyacht styling, it boasts superior fuel efficiency and a commendable average velocity-made-good of 9 knots.

Leopard Catamarans:

Emerging from the reputable Robertson and Caine shipyard in South Africa, Leopard Catamarans is synonymous with innovation and efficiency. The Leopard 53 Powercat is a testament to this legacy, showcasing excellent seakeeping abilities, offering 3 or 4 cabin configurations, and achieving a top speed of 25 knots.

Fountaine Pajot:

A trailblazer since 1976, Fountaine Pajot constantly redefines catamaran design. The Fountaine Pajot MY6 is a shining example, encapsulating the brand's visionary ethos. Stretching 15 meters, the MY6, equipped with dual engines of up to 2 x 353 Kw and 2 x 480 hp, promises dynamic sailing. Crafted meticulously by Pier Angelo Andreani, the interior mirrors a 20-meter monohull's spaciousness, reflecting modern aesthetics and comfort that stand as a benchmark in the Motor Yacht world.

These manufacturers continue to innovate, offering a blend of luxury, performance, and efficiency in their power catamaran models, making them a popular choice among maritime enthusiasts.

Comparing with Monohulls and Trimarans:

While monohulls are traditional and often cheaper, they lack the stability and space offered by power catamarans. On the other hand, trimarans, with three hulls, provide even more stability but at the cost of additional drag and less interior space.

TheBoatDB - Your Gateway to Maritime Exploration:

If you’re looking to delve deeper into the world of power catamarans and other vessels, TheBoatDB offers a comprehensive boat database. Explore various catamaran models, compare them with monohulls, trimarans, and other types of boats, and make an informed decision on your next maritime adventure.

In summary, power catamarans encapsulate a modern engineering marvel in the maritime domain. Their blend of speed, stability, comfort, and economy makes them an attractive option for a broad spectrum of boaters. Whether you are a long-distance cruiser, a water sport enthusiast, or someone who cherishes the tranquility of the sea, a power catamaran could be the vessel that transforms your maritime adventures into unforgettable experiences.

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PROA HULL DESIGN

The advantages of proa hull design.

Setting out with the goal of building the most efficient boats we could, our founder Larry Graf and his designers sought to create earth-friendly cruisers that would inspire a new generation of boaters. And because Larry and his team played a hands-on role in developing some of the world’s best catamarans, they had an idea of what a boat could be in terms of comfort, stability, and fuel economy.

When one looks at catamarans vs. monohulls, the starting point is clear. The many advantages catamarans exhibit when compared with monohulls are an excellent starting point. Catamarans offer a stable ride with predictable hull movement. The seakeeping is excellent, even in rough conditions. Another advantage the design provides: incredible onboard space. The space of a catamaran is often comparable to that of a monohull that is 25 percent longer. Catamarans also have been proven to provide efficient operation.

aspen catamaran hull

A Different Kind of Catamaran

The concept was formed, and extensive testing was done to both prove and refine the design until the hull form we have today was established and then patented.

The first boats were single-engine diesels, with all propulsion confined to the larger starboard hull. This hull has the appendages including a keel, prop, and rudder. The hull forms are hydrodynamically designed so that power on one side creates straight tracking when the rudder is centered. If it were not for this, and rudder was needed to make the boat track straight, the constant rudder movement would create additional drag. The proa hull form works efficiently with both inboard and outboard power. Performance and stability remain unmatched whether powered by a single diesel or two gas outboards.

The shape of the tunnels from fore to aft is also precisely crafted. The forward section is designed to cut through wave tops, when in extreme conditions, creating a slight amount of lift as the vessel enters the wave with no slapping. The water funnels back into the tunnel flowing evenly and exiting at the stern. This tunnel design keeps water flowing and reduces wave impact much better than the tunnels of other catamarans.

The wider starboard hull provides more space for the accommodations, and also makes it easier to access and manage the engine and machinery. The proa hull on the portside is 35 percent narrower, but its actual drag is reduced by approximately 50 percent due to fluid dynamics. A hull that is a little thinner maintains the buoyancy required to keep the boat running true but requires a lot less energy to move through the water. This makes a big difference in efficiency.

Our patented proa design for inboards uses just one engine, one shaft, one prop, one rudder, and one keel—half the typical engine appendage drag of a twin-engine design. The hulls are shaped to compensate for the engine torque. Since both fluid-dynamic and engine-torque forces are proportional to speed, the boat runs straight at every speed. Even better, the single-engine design saves dramatically on machinery weight, which in turn, saves on the required structural-component sizes and fuel needs, and their corresponding weight. This reduces the boat’s weight by around 44 percent. Less weight also equals much less drag. Thanks to solid engineering principles and innovation, our boats strike the perfect balance for the environment: comfortable and efficient.

proa hull design

A second round of innovation was conducted on the outboard-powered boats. Originally the second engine was to allow for a trolling motor, but testing and further refinement led to the two-engine configuration. By thinking even further outside the box, we created an asymmetrical installation that has not been seen previously: one 200-horsepower Yamaha on the larger hull, matched to a 70-horsepower outboard on the smaller hull. With the option to run on both engines or on the single larger outboard, or even just on the smaller outboard, we are able to see the advantages in efficiency.

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efficient catamaran hull design

Parts of Catamaran: A Comprehensive Guide to Understanding the Components

by Emma Sullivan | Aug 2, 2023 | Sailboat Racing

efficient catamaran hull design

Short answer: The key parts of a catamaran include the hulls, bridgedeck, mast(s), rigging, sails, rudders, and daggerboards. These components work together to provide stability, propulsion, and control for this type of multi-hulled watercraft.

Exploring the Essential Parts of a Catamaran: A Comprehensive Guide

From cruising the open seas to enjoying lazy afternoons by the shore, catamarans have become a popular choice for water enthusiasts. With their unique design and exceptional stability, these vessels offer an unmatched sailing experience . But have you ever wondered what makes up a catamaran and how each part contributes to its overall functionality? In this comprehensive guide, we will take you through the essential parts of a catamaran, uncovering their purpose and shedding light on why they are instrumental in making these boats such fantastic options for adventure seekers.

1. Hulls: The hulls are the twin structures that form the main body of a catamaran. These structures play a pivotal role in providing stability and buoyancy while at sea. Catamarans boast wider hulls compared to traditional monohull sailboats, resulting in increased surface area and enhanced stability. The design allows for smoother sailing even in rough waters, as each hull slices through waves independently.

2. Keels: Unlike monohull sailboats that rely solely on a single keel positioned beneath the waterline for both lift and resistance against sideways drift (known as leeway), catamarans often feature two separate skegs or keels attached to each hull. These auxiliary structures enhance directional control and offer excellent stability while reducing drag.

3. Deck: The deck is where all the action takes place! It serves as the primary horizontal surface on which passengers can relax, sunbathe or engage in various activities while aboard the vessel. Catamaran decks usually come with ample space due to their wider design compared to monohull sailboats .

4. Trampoline: One of the standout features of a catamaran is its trampoline – a mesh-like netting stretched between the two hulls just above sea level. While it may seem like an unconventional addition, trampolines provide multiple benefits including giving passengers an exhilarating sensation as they sit or lay above the water. This ample recreational area additionally offers an unobstructed view of the sea, making it an ideal spot for stargazing or simply enjoying the soothing sound of the waves.

5. Cockpit: The catamaran’s cockpit is strategically positioned closer to the waterline, ensuring a thrilling and immersive sailing experience. It acts as the primary control center where the helm is located, allowing sailors to expertly navigate their vessel through various seascapes. Additionally, some catamarans offer spacious cockpits that provide sufficient seating capacity for socializing with fellow passengers or hosting intimate gatherings while at anchor.

6. Rigging: The rigging refers to all lines, cables, and hardware necessary for controlling and adjusting the sails . Catamarans typically employ a simple yet effective rigging system that ensures easy maneuverability and efficient sailing performance. By skillfully managing these components, sailors can harness wind power optimally and maintain smooth cruising speeds in any weather conditions.

7. Sails: Sails are central to a catamaran’s propulsion system, enabling it to move gracefully across bodies of water without relying on fuel-based engines alone. Modern catamarans often embrace a sail plan consisting of multiple sails designed to maximize efficiency and adapt seamlessly to varying wind strengths and directions. With innovative designs such as fully battened mainsails and lightweight genoas, these boats have become incredibly agile even when faced with challenging wind patterns.

8. Engines: While a catamaran’s sails provide a significant portion of its power source, auxiliary engines are still crucial for many aspects of sailing life – be it docking in tight spaces or maneuvering during low-wind situations. These engines are usually mounted within each hull beneath deck level as part of an integrated propulsion system comprising shafts, propellers, and operational controls.

9. Navigation Instruments: In today’s era of advanced technological aids, catamarans make use of a range of navigation instruments to enhance safety and efficiency. From GPS systems providing precise positional information to depth sounders measuring water depth, these sophisticated tools are essential for ensuring smooth journeys and avoiding potential hazards.

So there you have it – a detailed glimpse into the essential parts of a catamaran. Wherever your sailing adventures take you, now you can fully appreciate how each component contributes to the incredible performance and unrivaled experience offered by these magnificent vessels. So hop aboard a catamaran and embark on your next nautical journey with confidence!

How to Identify and Understand the Various Components of a Catamaran

Catamarans are fascinating vessels known for their unique design and exceptional performance on the water. Whether you are a seasoned sailor or just interested in learning more about these incredible boats, understanding their various components is essential . In this blog post, we will take a detailed, professional, witty, and clever dive into the world of catamarans and shed light on how to identify and understand their different parts .

1. Hulls: At the core of any catamaran are its hulls – the main supportive structures that keep the boat afloat. Unlike traditional single-hulled vessels, catamarans have two parallel hulls connected by a deck. These hulls play a vital role in providing stability and minimizing drag while sailing. Think of them as the sturdy legs that help the catamaran gracefully glide through the water .

2. Deck: The deck serves both as a platform for enjoying your time onboard and as an important structural element that connects various parts of the catamaran. It consists of multiple areas such as the helm station (where you control the boat), seating areas, dining spaces, trampoline nets for lounging, and storage compartments. Sunbathing or hosting friends for a sunset gathering? The deck has got you covered!

3. Rigging: If you’ve ever looked up at a sailboat’s mast with admiration, then you’ll love discovering how rigging contributes to a catamaran’s overall performance and elegance. The rigging includes all the supporting wires and ropes that hold up the mast(s) on your catamaran and control its position relative to wind direction (known as “trimming”). Understanding how to properly trim your sails can greatly enhance your sailing experience – from capturing optimal wind power to achieving picture-worthy maneuvers.

4. Sails: What could be more mesmerizing than watching billowing sails against an azure sky? Catamarans utilize various types of sails based on their purpose – mainsails, jibs, genoas, spinnakers – each designed to maximize performance under specific wind conditions. Learning about the different sails and their characteristics will help you navigate efficiently and make the most of your sailing adventures. Plus, understanding the art of sail trim is sure to impress your fellow sailors!

5. Rudders: Just as a captain relies on his or her compass for navigation, catamarans depend on rudders to steer through the water with precision. Mounted at the stern (rear) of each hull, these ingenious components allow you to control your course by diverting the flow of water passing beneath them. Rudders are essential for maintaining stability and maneuverability when tacking, jibing, or navigating challenging waters.

6. Engines: Catamarans aren’t solely reliant on wind power; they often incorporate engines as auxiliary means of propulsion. These mechanical marvels provide added security and flexibility during low-wind situations or when maneuvering in confined spaces like marinas or crowded anchorages. Understanding how to handle your catamaran’s engines confidently will ensure smooth sailing even when Mother Nature plays hard-to-get.

By expanding your knowledge about these various catamaran components – hulls, deck, rigging, sails, rudders, and engines – you’ll unlock a whole new level of appreciation for these magnificent vessels and gain confidence in navigating them.

Lastly, remember that wit and cleverness go hand-in-hand with professionalism when exploring any topic. So have fun while unraveling the mysteries of catamaran anatomy! Perhaps envision yourself as an expert sailor who can distinguish port from starboard blindfolded or sharpen your comedic skills by jokingly referring to hulls as “feline foundation” (though cats might not appreciate sharing their name with boats!).

Happy sailing!

Step-by-Step Breakdown: Unraveling the Mysteries behind Catamaran Anatomy

Catamarans have become increasingly popular in recent years, mainly due to their unmatched stability and impressive speed capabilities. But have you ever wondered what lies beneath the sleek exterior of these remarkable vessels? In this blog post, we will delve into the intricate details of catamaran anatomy, providing you with a comprehensive understanding of how these boats are constructed and why they excel on the water.

1. The Hulls: The Foundation of Stability At the core of every catamaran lies its hulls – two parallel structures that run alongside each other. Unlike traditional monohull boats that feature a single hull, catamarans distribute their buoyancy across two hulls, offering superior stability even in rough waters. These hulls are typically made from fiberglass or aluminum and are designed to cut through waves effortlessly, minimizing resistance and maximizing speed.

2. Bridging the Gap: The Trampoline One striking feature present in many catamarans is the trampoline located between the two hulls. This sturdy mesh-like material serves various purposes. Firstly, it provides an additional platform for sunbathing or relaxing while underway. Secondly, it acts as a safety net by preventing crew members or passengers from falling into the ocean should any unexpected jolts occur during navigation .

3. Connecting Hulls: The Crossbeams In order to maintain structural integrity and connect both hulls securely, catamarans utilize crossbeams that stretch between them. These crossbeams play a vital role in sharing weight distribution evenly across both sides, ensuring stability and balance at all times.

4. Above Deck: Central Cockpit and Living Space Moving upwards onto the deck area, you’ll discover a central cockpit where most controls and steering mechanisms are located. This strategic placement allows for optimum visibility and easy maneuverability while sailing. Additionally, catamarans often feature large living spaces, including saloons and cabins that provide ample room for socializing, dining, and sleeping. Their spaciousness is a significant factor contributing to their growing popularity among cruising enthusiasts.

5. The Power of Sails: Rigging and Sail Plan Catamarans rely on sails for propulsion, utilizing a complex system of rigging to hoist and control them effectively. A unique feature of catamarans is the absence of a single mast; instead, they employ multiple masts strategically positioned between the hulls. This configuration optimizes sail area while reducing heeling (when a boat tips sideways due to windy conditions), resulting in smoother sailing experiences even during stronger winds.

6. Additional Features: Daggerboards or Foils To enhance performance further, some catamarans are equipped with daggerboards or foils – retractable appendages located beneath each hull. These boards reduce lateral slippage by providing lift, improving upwind capability and enhancing overall speed. As technology advances, advanced hydrofoil systems have also been introduced in certain catamaran models, allowing these boats to glide above the water ‘s surface entirely.

By unraveling the mysteries behind catamaran anatomy step-by-step, it becomes evident why these vessels are highly sought after by both leisure sailors and competitive racers alike. From their stable hull design to innovative features such as trampolines and foils – every element plays its part in creating an exceptional sailing experience that combines comfort, speed, and versatility. Perhaps now you can fully appreciate these engineering marvels whenever you set sight on one gliding gracefully through the waves!

Frequently Asked Questions about the Different Parts of a Catamaran Answered

Have you ever looked at a catamaran and wondered what all those different parts are called? Or maybe you’re thinking about buying or renting a catamaran and want to be familiar with its components . Well, look no further! We’ve compiled a list of frequently asked questions about the different parts of a catamaran and will provide detailed, professional, witty, and clever explanations just for you.

1. What is a Catamaran? A catamaran is a type of boat that consists of two parallel hulls connected by a deck. It offers increased stability compared to traditional monohull boats due to the wider beam. This unique design allows for smoother sailing experiences and more spacious interiors.

2. Hulls – What Are They? The hulls are the main structure of a catamaran, providing buoyancy and supporting the entire vessel. Typically made from fiberglass or aluminum, they have curved shapes that help reduce resistance in the water while providing stability. Think of them as the legs of the feline-inspired boat!

3. Trampoline – Isn’t That for Jumping? While it may sound similar to the equipment used for bouncing around at your local playground, in the world of catamarans, trampoline refers to an open area between the hulls where passengers can relax or even stretch their sea legs! Made from durable materials like nylon mesh or PVC canvas, trampolines provide excellent circulation and an unobstructed view below deck.

4. Rigging – Is it Related to Sailing Techniques? Indeed! Rigging refers to all the elements involved in controlling sails on a catamaran . This includes mast(s), boom(s), standing rigging (shrouds & stays), running rigging (halyards & sheets), winches, cleats – basically everything needed to manipulate wind power efficiently and safely navigate through various conditions.

5. The Mast – How Tall Should It Be? The mast, often made of aluminum or carbon fiber composite, is the tall vertical pole that holds up the sails. Its height depends on several factors, such as boat size, intended use, and the desired sail area. Think of it as the catamaran’s lighthouse – guiding you along your aquatic adventures with grace.

6. Boom – Not Just a Sound Effect! Nope, not just an imitation of an explosion! The boom is a horizontal spar attached to the bottom of the mast, helping support and control the lower edge (foot) of the mainsail. It swings back and forth with changes in wind direction – think of it as a catamaran’s wagging tail!

7. Daggerboards – Are They Catamaran Ninja Weapons? While they may sound dangerous and ninja-worthy, daggerboards are actually retractable foils that extend from each hull into the water. Their purpose? Providing lateral resistance against sideways motion caused by wind force while improving upwind performance by reducing leeway – no martial arts skills required!

8. Rudders – Steering Like a Pro Like most boats, catamarans have rudders for steering purposes. These underwater blades at the stern help control direction by redirecting water flow around them when turned. Whether you’re tacking or gybing through waves or researching rudder-related puns like this one—we’ve got you covered.

So there you have it – frequently asked questions about the different parts of a catamaran answered in detail! Now you can impress your fellow sailors with your newfound knowledge or confidently embark on your next seafaring adventure aboard one of these sleek double-hulled vessels ! Remember to keep exploring and enjoy every nautical mile!

The Key Elements That Make up a Catamaran: Everything You Need to Know

Title: The Key Elements That Make up a Catamaran: Everything You Need to Know

Introduction: Catamarans have long fascinated sailing enthusiasts with their unique design, efficient performance, and spacious interiors. Whether you are a seasoned sailor or a curious novice, understanding the key elements that make up a catamaran is essential. In this enlightening article, we will delve into the intricate details of these remarkable vessels, uncovering the secrets behind their success on the open seas .

1. Hull Design: Stability Meets Speed At the heart of every catamaran lies its dual-hull structure. Unlike traditional monohulls, catamarans feature two separate hulls connected by a spacious deck. This design offers enhanced stability and reduced heeling, making them less prone to capsizing compared to their single-hulled counterparts. The inherent buoyancy allows for faster speeds and smoother sailing experiences—enabling both exhilarating adventures and relaxed cruising.

2. Beam: Embracing Extra Space One of the most significant advantages of a catamaran is its beam—the width between its two hulls—which can be quite impressive. The ample beam creates an exceptionally generous living area that sets catamarans apart from other sailboats . More space means greater comfort for passengers and crew alike; accommodating larger groups, luxurious amenities, and even personalized additions such as Jacuzzis or sunbathing decks.

3. Stability & Balance: A Steady Journey In addition to their unique structural design, catamarans offer exceptional stability through weight distribution and physics principles. With twin hulls spread apart at a considerable distance, it becomes significantly easier to maintain balance during sailing motions—a significant advantage for those susceptible to seasickness or seeking effortless navigation under challenging conditions.

4. Sailor-Friendly Handling: Ease-of-Use at Sea Catamarans excel in terms of maneuverability due to several factors working harmoniously together. Their shallow drafts allow for exploration in shallower waters, and docking becomes a breeze with the ability to navigate narrower marinas. Furthermore, their twin engines operate independently, offering excellent control even in tight spots or challenging wind conditions—a maneuverability dream for sailors of all skill levels.

5. Sailing Performance: Effortless Speed When it comes to performance on the water, catamarans stand tall once again. The efficiency gained from their two hulls reduces drag and enables quicker acceleration, resulting in higher average speeds than traditional monohulls. Even when faced with light winds, their ample deck space allows for customized rigging options—such as efficient sails or high-tech foiling capabilities—that can unlock extraordinary speed potential.

6. Comfortable Living Spaces: An Unprecedented Haven Catamarans redefine on-board living by providing both ample space and superior comfort. The expansive interior saloon offers panoramic views of the surroundings while being versatile enough to cater to various activities—from hosting lively social gatherings to peacefully reading a book by the window. Additionally, private cabins are often located in each hull, creating secluded sanctuaries for relaxation and tranquility amidst enchanting seascapes.

Conclusion: As we conclude our exploration into the key elements that make up a catamaran, it becomes evident why these vessels have become revered in the sailing world . The revolutionary dual-hull design ensures stability and faster speeds while offering unparalleled comfort and spaciousness aboard. Whether you seek adventure or serenity on the seas, understanding these elements will help you appreciate catamarans’ remarkable qualities truly—an embodiment of innovation and maritime excellence brought together harmoniously by human ingenuity.

Mastering the Parts of a Catamaran: A Beginner’s Guide for Sailing Enthusiasts

Are you a sailing enthusiast who is fascinated by the sleek and efficient design of catamarans? If so, then you’ve come to the right place! In this comprehensive beginner’s guide, we will delve into the key components of a catamaran and unlock the secrets to mastering its various parts. So grab your sailor’s hat and get ready to embark on an exciting journey through the intricate world of catamaran sailing!

The first component that sets a catamaran apart from other sailboats is its dual-hulled structure. Unlike traditional monohull sailboats, which have only one hull, catamarans feature two parallel hulls connected by a deck or bridge. This unique design grants them exceptional stability, speed, and even more interior space for amenities such as cabins and lounging areas.

Now let’s move onto a crucial part of any sailboat – the rigging . The rigging system on a catamaran consists of numerous elements that work harmoniously to control and manipulate the sails . Firstly, there are the masts: tall vertical structures that support the sails. Catamarans typically have two masts placed towards each end of the boat , allowing for efficient distribution of power.

Attached to these masts are various types of sails, including mainsails, jibs or genoas (fore-sails), and spinnakers (used for downwind sailing). The main sail is the largest sail on a catamaran and is hoisted up the mast using halyards – ropes specifically designed for this purpose. Jibs or genoas assist in maneuverability by generating additional power when sailing upwind.

For those seeking exhilarating downwind adventures, spinnakers add an extra element of thrill to your journey! These expansive triangular or bulbous-shaped sails catch wind from behind and propel your catamaran with remarkable swiftness. Learning how to handle these different types of sails will be crucial to seamlessly controlling the boat and maximizing performance on the water.

Next in line are the helm and steering system, responsible for guiding your catamaran ‘s path as it gracefully glides through the waves. The helm, often referred to as the steering wheel , is used to control the rudders located at each hull’s stern. One unique characteristic of catamarans is their tilting tendency caused by wind pressure acting upon the exposed surface area of their broad decks. Therefore, mastering steering techniques, including adjusting sail configurations and keel positions, will help you navigate with finesse and maintain balance.

One particularly innovative feature found in some catamarans is a daggerboard or a centerboard system. Located between the two hulls beneath the waterline, these retractable fins can be individually raised or lowered to vary their depth while sailing. By adjusting these boards according to wind conditions and point of sail , you can minimize resistance, optimize speed, and even prevent lateral drift.

We cannot overlook catamarans’ anchoring systems when discussing their components . Anchors are vital for keeping your vessel secure when moored or stopping for a leisurely swim in crystal-clear waters. Most modern catamarans employ bow rollers integrated at the front end that facilitate effortless anchor deployment and retrieval. With an array of anchor types available — from plows to flukes — it’s essential to understand each one’s characteristics in various seabed environments.

Lastly, let’s not forget about safety equipment onboard! While mastering catamaran parts allows for glorious adventures on calm seas, unforeseen challenges may arise during your sailing odysseys. It’s important always to have safety essentials like life jackets, fire extinguishers, first-aid kits, emergency flares, and navigational tools like GPS systems.

So there you have it – a comprehensive overview of key components necessary for mastering the art of sailing a catamaran! Understanding how each piece of the puzzle fits together and harmonizes uniquely will set you on a path to becoming a skilled catamaran sailor . Whether you’re gliding across tranquil bays or tackling exhilarating rough seas, this guide will equip you with the knowledge and confidence to embark on unforgettable nautical journeys!

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Catamaran hulls- everything you need to know.

  • Post Written By: Boater Jer
  • Published: July 17, 2022
  • Updated: July 19, 2022

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Catamaran hulls are not like normal boats but provide increased stability. Let’s take a look at these incredible boats and how their hulls create one of the most versatile watercraft available today.

The Tamil Cholas used catamarans to ferry their troops to invade Malaysia, Indonesia, and Burma. The early paravars or fishing communities in the southern part of Tamil Nadu used two-hulled boats to fish. Polynesian seafarers were also early users of the catamaran, utilizing the watercraft to get to hard-to-reach islands. ( source )

Although the catamaran hull concept is a relatively new introduction to modern boat design , the boat has been in use since the 5th century. It was used for fishing, traveling, and transporting people and supplies. 

Parts Of A Catamaran

Here are the basic parts of the modern sailing catamaran:

  • Hulls are what sets this boat apart from the rest. The catamaran has two hulls, while the monohull, as the name suggests, has only one hull. Most of the advantages of this boat are hinged on these two hulls. 
  • The bridge deck connects the two catamaran hulls. 
  • On top of the catamaran hulls and the bridge deck is the deck . It is where owners attach most of the equipment in a boat. 
  • You can locate the berth, the galley, and other living amenities in the cabin . 
  • The cockpit is where you find the navigation equipment of the boat . It is where you control the catamaran’s rudder, sails, and engine. 

Types Of Catamaran

Types of catamarans are explained on Boating.guide

The modern catamaran is far more different than its crude ancestor. Instead of tree cutouts, catamarans are now carbon fiber or fiberglass. Here are the different types of catamarans: 

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Based On function

Pontoons are usually present on rivers and lakes and sometimes even on oceans, but they only travel near the shore.

In a catamaran pontoon-type boat, the pontoons serve as storage areas, where you will find the onboard motors. They are useful for water leisure activities such as short water trips, tubing, wakeboarding, and water skiing. 

Some pontoons may also serve as houseboats. They provide a broader, more stable platform ideal for a floating house. Plus, the space is bigger, and most of it is above water. It offers a better viewing option than a monohull. ( Source )

Small Waterplane Area Twin Hull is a catamaran-type boat that the United States Navy initially used for military purposes. They provide the water stability that is necessary when transporting heavy military equipment. 

One example of a military SWATH catamaran is the Spearhead class EPF. It is as long as a World War II escort destroyer, yet it is twice as fast at 43 knots. It can reach that speed because of its two separate hulls.

Because of their innate speed, SWATH catamarans can become patrol boats in lakes and rivers. They can easily outrun and outmaneuver standard watercraft.  

Nowadays, there are SWATH cruise ships and other non-military variations. ( Source )

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Based On Design

  • Sailing Catamaran

The smaller sailing catamarans do not have auxiliary engines, so the owner can propel the boat by harnessing the wind using the sails. It’s a popular choice for people with very little or no sailing experience because they are light and easy to use. 

The larger sailing catamarans are for group charters and long-distance cruising. They have become so popular lately that they now outnumber monohulls in tropical locations all over the world. They have a last, a headsail, and a mainsail. And the twin hulls have one engine each. 

  • Power Catamaran

Unlike their sailing cousins, the powered catamarans do not have sails. They have massive engines which provide high speed. Their twin hulls are stronger and can carry and protect the large motors. 

The smaller “powercats” are used mainly for fishing. The bigger ones are rented out for charters and cruises. 

Catamaran Hulls Performance 

Thanks to the catamaran hulls, the boat offers many advantages over other boat types. 

  • Because its dual-hull design provides a broader base, it offers more water stability than monohull boats. It makes the cat (catamaran) a popular choice for fishing expeditions and cruises.
  • Riding a catamaran is ideal for people who feel seasick whenever they ride boats. The twin hulls prevent the boat from moving from side to side. The hulls allow the boat to travel smoothly, even on moderately choppy waters.
  • The catamaran is the best choice when storing provisions and other household items with less heeling and bobbing. 
  • The twin hulls’ stability is ideal for many activities such as cooking and partying. 
  • Cats offer more moving space because of their broader base, thanks to dual hulls.
  • With a catamaran, you have two great options on where to hang out. You can do it on the spacious deck or below the galley. 
  • Compared to a monohull of the same size, the catamaran can accommodate more equipment and people.
  • The living area in a catamaran is above the water line. This feature provides more natural light, a greater view of the outside, and better air circulation. 
  • Since catamarans do not have keels, they can anchor on shallow waters, something that most monohulls will not be able to do. This ability of catamaran boats is impressive, especially if you are going around areas with many reefs and small islands.
  • Catamaran hulls allow the boat to cut through the waves easier and faster. It means they require less engine power than their monohull counterparts.
  • Because it has two engines and two rudders, the catamaran can easily maneuver in very tight spaces. 
  • Because they do not carry heavy keels, catamarans can sail faster than monohulls. 
  • The catamaran’s stability, speed, and weight make it a safer option than the monohull. It can sail in shallow waters, make a 360 degrees maneuver effortlessly, and carry more provisions. 

Disadvantages Of A Catamaran

Like any other boat type, the catamaran also has drawbacks and limitations. Here are some of them:

  • The catamaran hulls prevent the boat from sailing as fast as the monohull upwind. The two hulls cause drag, and this slows the boat considerably. 
  • Because of its bigger size, looking for a docking site can be more difficult and costlier than a monohull. 
  • For hardcore sailing fans, the experience of sailing with a catamaran will never be able to match that of sailing with a monohull. To them, the challenge of true sailing is just not there with a catamaran.

What Are The Hulls Of The Catamaran Called?

According to the Online Etymology Dictionary, the Tamil word கட்டுமரம், which is pronounced as kattumaran, is where the word catamaran takes its name. The word means “pieces of logs tied together”. Through the years, the term has evolved into what is now a catamaran in English. 

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What Are The Characteristics Of A Catamaran Hull?

  • Both hulls of a catamaran complement each other to achieve very minimum water resistance. 
  • Because of this, it takes less energy to propel a catamaran, whether via an engine or sails. 
  • The catamaran hulls provide stability to the boat. The twin-hull significantly reduces bobbing. 
  • The catamaran’s ability to keep steady on the water makes it an ideal vessel for cooking, dining, and storing provisions. 

Are Catamarans Good In Rough Water?

Catamarans are amazingly stable in rough water. The catamaran’s design and build, which provides stability, are factors why it is one of the best boats to use when the waters are choppy. 

Yes, catamarans are relatively more expensive than monohulls. Nevertheless, since single-hull boats are less expensive, their resale value is also cheap. 

If you add all the advantages that a catamaran offers – safety, comfort, and speed- it does not come out expensive. 

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A Guide to Catamarans: Exploring the Beauty of Twin-Hull Vessels

efficient catamaran hull design

Catamarans are a fascinating class of vessels that have captured the imagination of sailors and water enthusiasts worldwide. With their distinctive twin-hull design and numerous advantages, catamarans have become increasingly popular in recent years. Whether you’re a seasoned sailor or a novice to the world of boating, this guide will introduce you to the allure of catamarans and help you navigate your way through these remarkable vessels.

Understanding Catamarans: The Basics

1. Twin-Hull Design: At the heart of every catamaran is its twin-hull design. Two parallel hulls provide stability and buoyancy. This design offers several advantages, including reduced rolling motion, increased deck space, and shallower draft, making them suitable for various water environments.

2. Stability: Catamarans are renowned for their exceptional stability. The wide-set hulls offer a solid platform, reducing the tendency to heel (tilt) in strong winds or rough seas. This stability is a key reason catamarans are favored by those who are prone to seasickness.

3. Speed and Fuel Efficiency: The dual-hull design creates less drag, allowing catamarans to achieve impressive speeds and superior fuel economy. The reduced water displacement means they can be faster and more fuel efficient than monohull vessels of the same size. This speed and fuel efficiency makes catamarans ideal for both leisure cruising and competitive racing.

4. Deck Space: Catamarans provide ample deck space, which is perfect for fishing, sunbathing, or just relaxing. The absence of a central keel and a tapered bow enables you to make the most of the deck space, often with a seamless connection between indoor and outdoor areas.

Types of Catamarans

Catamarans come in various shapes and sizes, each designed for specific purposes. Here are some common types:

1. Sailing Catamarans: These are designed primarily for sailing, offering the joy of wind-powered navigation. Sailing catamarans often have spacious living areas and are great for extended cruising.

2. Power Catamarans: Power catamarans are equipped with engines for those who prefer motor-driven propulsion. They are known for their efficiency, stability, and relatively shallow draft, making them suitable for a variety of applications, from fishing to luxury charters.

3. Cruising Catamarans: These are designed for long journeys, often with comfortable living quarters, kitchens, and spacious cabins. Cruising catamarans are popular for people looking to explore coastal and offshore destinations.

4. Racing Catamarans: These are built for speed and competitive racing. They have sleek designs, lightweight construction, and advanced rigging systems, making them the choice for adrenaline enthusiasts.

Advantages of Catamarans

1. Stability: Catamarans offer excellent stability both at anchor and underway. This stability is a key reason families and novice sailors often opt for catamarans.

2. Spacious Interiors: Catamarans provide ample living space, with multiple cabins, saloons, and kitchens. The wide beam allows for a comfortable and roomy interior.

3. Reduced Draft: Catamarans have a shallow draft, allowing them to access shallower waters, hidden coves, and secluded anchorages that might be off-limits to deeper-draft monohull boats.

4. Maneuverability: Catamarans can execute tight turns with precision, making them easier to dock and navigate in marinas.

5. Safety: Thanks to their buoyancy and stability, catamarans are less prone to capsizing, making them a safer choice, especially for families.

Challenges of Catamarans

1. Maintenance: Catamarans often have more complex systems due to their twin engines and two hulls, which can result in increased maintenance requirements.

2. Cost: Catamarans are generally more expensive than monohull boats of similar size and age.

3. Docking Space: The wider beam of catamarans can require wider slips in marinas, which may limit docking options in some locations.

Sailing the Seas in Style

Catamarans offer a unique and exciting way to explore the world’s oceans, rivers, and lakes. Their stability, speed, and spaciousness make them an excellent choice for a wide range of water-based activities, from leisurely cruising to competitive racing. Whether you’re looking for a family-friendly vessel, a luxurious yacht, or a thrilling racing machine, catamarans have something to offer every sailor and water enthusiast. So, if you’re ready to set sail in style and comfort, consider exploring the world of catamarans and discovering the beauty of twin-hull vessels.

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Hull Resistance and Hull Shape Comparisons

Introduction

As I've said elsewhere, I only like to design boats that are fun to sail. I also know from personal experience just how much effort is involved in building even the smallest boat. I've found that it is the psychological effort that's particularly hard, especially if you are a home builder building alone in your spare time. I also know that there are other people, like myself, who's keeness to build is not matched by manual dexterity.

So I try to design boats that are straightforward to build. In simple terms, if I can build it then anyone can! To do this I try to keep to simple shapes and use flat panels where ever possible. Flat decks in particular have many advantages. For a start they are easier to walk on, while coming alongside and boarding from a marina pontoon or dinghy is a lot safer. Flat panel hulls may not offer ultimate speed, but to be honest, few cruising sailors need the fastest boat while I've found that most people don't have either the skill or daring to sail a racing boat to its full potential.

You have to remember that a cruising boat, especially, isn't just for sailing. It has to be a practical floating cottage as well. And the design of that often over rules otherwise desirable sailing features. And also remember that boats have to be usable in harbours and marinas. It's not like the "good old days" when Slocum and even the Pardey's first went to sea - with no engines and few marinas or even cruisers. So all cruising boats MUST maneuver reliably under power and be easy to board from both the dock and from a dinghy.

That is one reason why I don't now like canoe sterns. They make boarding so much harder than a boat with transom steps (the acid test I always use - "could my mother get on board?"). Safe maneuvering in a small harbour is another reason I like small boats. I also find a trimaran much harder to handle than a catamaran when coming alongside, as it is so difficult to reach the outrigger bows to fend off, especially when compared to the big wide decks of a catamaran. Successful designs are ones that work in every situation, not just those that sail or motor fast in a straight line.

I always try to visulise what a particular design would be like when sailing to windward at 2am in the rain. Or when reefing. Or of course when drifting downwind on a very hot humid day.

I tend to own a fleet of multihulls. Sometimes I just go for a day sail, sometimes I race for the weekend, and most years I spend a long time living on board (I spent every Christmas living on board a boat from 2001 - 2009). All this experience means that I have personally faced nearly every situation you can meet when sailing and I use that experience in my designs.

Hull Shapes and Performance

In this article I will talk solely about hull shapes in relation to performance. Comfort, seakindliness and load carrying are also major factors affecting hull shapes and will be discussed in more detail in future articles.

People try to simplify hull design and performance predictions, formulae like the Bruce Number and KSP spring to mind. These coefficients rely only on basic sail area, displacement and length dimensions yet purport to give an accurate indicator of performance. It's easy to show that these formulae cannot be relied on if you consider that a Tornado would have the same rating whether it was sailing forwards or backwards! I suspect the latter is slower! Its probably as accurate as predicting car speed from the kerbside weight and engine horsepower. In fact hull design is a hugely complex subject while different sailing conditions require different solutions. For example, inshore boats can have a flatter rocker while offshore cruisers should be more veed forward to prevent pounding when sailing to windward in waves.

Some factors affecting yacht design are based on scientific principles and are unalterable, so always apply, whatever ones basic design philosophy and regardless of cross section shape (ie whether one uses a Deep V or round bilge hull for example). Everything else is just styling or dressing up the same proven concepts in a slightly different way. As with all moving objects, speed is the result of the combination of resistance to movement (drag) and available power. In sailing boats the power is related to the sail area while in simple terms drag comes in two forms - friction drag and wave making drag.

Frictional drag is primarily dependent on the Wetted Surface Area (WSA). Less is always better than more and WSA is the biggest factor affecting lightwind speed. The minimum WSA for a given displacement (or boat weight) is the hemisphere (eg half an orange). A longer, thinner hull has proportionately more WSA and so in light winds suffers from more drag and thus is slower but conversely is significantly faster as the wind gets up. In fact this is one reason why monohulls - which are much more orange like, do well in light winds. Spray also adds to wetted surface, one reason why powerboats have spray rails. Lots of spray makes a boat look as though it is sailing fast, but it is actually very inefficient. As an example, because of their heel and deeply immersed lee outrigger, trimarans make a lot more spray than catamarans. But we usually find that they are actually slower, particularly reaching, than an upright, low spray producing catamaran. Round bilge hulls have the lowest WSA and deep V hulls the most.

Many people think that, because multihulls have relatively thin hulls, wave making drag is non-existent, but in fact, nothing could be further from the truth. The size of waves that a hull makes depends on several factors. The Slenderness Ratio (SLR) or Displacement Length Ratio (DLR) is a measure of the fineness of a hull and is the technically correct coefficient that naval architects use. However, it is easier to visualise the hull waterline length/hull WL Beam ratio (LWL/BWL), so that is more commonly used. That's acceptable, as for a given cross-section shape, the SLR is directly related to LWL/BWL. Higher ratios result in smaller waves. Typically the LWL/BWL ratio will vary from 10:1 for a good cruising boat to 16:1 for a racing boat. (Team Philips has a LWL/BWL ratio of 35:1!) Finer hulls are more efficient at high speeds, but as we've just seen suffer from more WSA and so for normal cruising catamarans in average conditions a ratio of 11:1 - 13:1 seems optimum.

The Prismatic Coefficient (Cp) is a measure of the fullness of the ends of a boat, the higher the number the fatter the ends and - surprisingly - the more efficient at high speeds. Intuitively you'd think that a diamond shape would cut through the water best, but that's not actually the case. A high Cp also has the advantage of reducing pitching. But to complicate matters, the lower the SLR the lower the Cp can be. Typically a monohull has a figure around .56, while a properly designed multihull will be about .63. Although such a shape is slower than a lower Cp in light winds that is not a problem as one then has the sail carrying power to add extra sail to compensate. It is when sailing fast in strong winds that you need an efficient hull because you then don't have the stability to carry more sail. As an example a 30' boat with a Cp of .63 will be 1/2 knot faster than one with a Cp of .55 when sailing in 25 knot winds for EXACTLY the same sail area (and crew effort etc). Boats with a low Cp try to race faster by keeping too much sail up and it was these types that often used to capsize 25 years ago. Add in the fact that the high Cp boat won't pitch as much and its clear which is going to be the better boat.

In simple terms the Half Angle of Entry is the angle that the waterlines make to the hull CL at the bow. If it is too low then the boat is wet to sail, and, in extremis, if it is hollow there is a pressure build up further aft which slows the boat. If too fat it is also wet to sail as the bow wave goes vertically up the sides of the boat. All sailors, no matter how skillful, sail slower if they can't see where they are going because they are being blinded by spray! In both cases the correct Cp has to be maintained. So a 10 degree angle seems a good compromise. Vertical bows look fast but its actually very difficult to draw a vertical bow on a hull with both the correct Cp and one that has good reserve buoyancy. Read my articles about the Cape to Rio race to discover what I learnt first hand about the perils of vertical bows!

When I was a design student I took the opportunity to do some tank testing on catamaran models and I investigated the drag from the wave interference between the hulls. I found that this interference caused significant drag at certain speeds - in fact up to 20% when compared to hulls at an infinite spacing. So it's vital to reduce this interference as much as possible. The simplest way is to have a hull spacing wide enough so that the bow waves meet at the stern rather than under the boat. This has the added bonus that there is significantly less bridge deck slamming. In the past designers said that the optimum L/B ratio was 2:1. (In fact they were talking about overall length and beam when obviously it is waterline length and beam that are the crucial measurements.) The reasons given for this ratio were the theories that wider boats would break up and be hard to tack. In practice I've heard that limiting beam had more to do with the width of the boatyard doors! Our Strider Turbo has a LWL of 6.6m and a hull centreline spacing of 4.2m yet I've always thought it was a better sailing boat than the standard Strider. So the general trend is to go as wide as one can. But structural strength is still a problem, even with modern techniques and materials. Wide boats are heavier than narrow ones and that ultimately limits the LWL/BWL ratio to about 2:1 on cruising boats with full bridgedeck cabins.

Turning now to the hull above the waterline, vertical topsides reduce space inside dramatically and in addition are not good news when sailing offshore. As a boat moves in waves so it heaves up and down, causing discomfort and slowing the boat. Flared topsides help counteract this heaving because as the boat sinks the buoyancy picks up more quickly than with vertical topsides. The result is a smoother ride and as a bonus, better load carrying ability for, by the same token, the hull sinks slower so there is less increase in WSA and wavemaking as the boat is loaded. Clearly, freeboard adds to windage and slows the boat. Traditionally yachts had low freeboard because they were large (J Class etc) so people could fit in the accommodation easily regardless of freeboard and it's easy to make a low freeboard yacht look elegant. More importantly, it was hard to make a conventionally caulked and planked boat strong and watertight if it had too many planks (ie too much freeboard). As boats got smaller and as grp took over freeboards had to, and could, increase. Adding a few centimetres (inches) of freeboard adds enormously to interior space and at the same time results in a boat that is drier and more comfortable to sail. Fortunately, in practice I have never found that high freeboard slows the boat down appreciably and certainly not by enough to worry any except the most ardent racer.

Load carrying considerations are an important factor for cruising boats. In general it's natural for people to add weight aft because it is easier to load stores near the companionway than forward. Engines and their associated tanks, generators, a/c units etc are also always aft. So I always try to add extra buoyancy near the stern. That means that when empty the boat will probably float stern up. Too many poorly designed multihulls float stern down and drag their transoms.

Pros and Cons of popular hull shapes

The deep V is a simple to build hull shape that matches the human body as it is narrow low down and wider high up so it is a good choice if the accommodation is only in the hulls. It can make to windward without keels or boards - just - but it's more maneuverable and makes less leeway with them fitted. Deep V hulls pitch more than any other hull shape, particularly if they have canoe sterns. Hull asymmetry is needed to reduce pitching, a canoe stern is obviously as pointed as the bow so it's bound to pitch more. They have more WSA than any other hull shape so are slow in light winds.

The flat bottom hull is also easy to build and has the added advantage that it is self supporting during building and transport. It needs Veeing forward for offshore sailing or it will pound. Then it becomes a hard chine/single chine hull. Carefully drawn such a shape is a close approximation to a round bilge hull, but without any complicated building.

The round bilge hull is the only hull shape that can be varied over it's length so one get exactly the shape one wants. It has minimum WSA, and so is also the optimum hull shape but it is the slowest to build. A topsides knuckle helps deflect spray, adds interior volume and makes it easy to join flat topsides to the curved bottom. It also makes a nice styling line.

From the start of my design career I have always tried to design balanced, undistorted hulls that sail easily on all points but are not too extreme. However, I have made a few changes to my hull shapes over the years. First I have increased freeboard (in common with most designers, monohull and multihull). I have also increased the centreline spacing and where appropriate, drawn a bigger knuckle. I haven't designed any deep V boats for a long time because of the pitching and light wind speed problems. I have found the flat bottomed or single chine hulls are as simple to build and are more efficient hull shapes.

Finally, I am one of the few designers who use all feasible hull shapes and so can choose the most appropriate one for the intended use. I'm not committed by dogma to any one hull design. The performance differences between different hulls are easy to see, however I have not noticed any practical difference in seaworthiness between them.

The following sketches are typical hull cross sections. Please note, these are not to scale and are not real boats, instead they are just examples of the different hullshapes we use in our designs. (For those not familiar with lines plans: Only half sections are shown. The forward half of the boat is shown to the right, the aft half is to the left of the vertical centreline.)

efficient catamaran hull design

This is the "Dory" hull used on the Janus and Gypsy as well as the Strike trimaran mainhulls. Note that the Janus does not have a V'eed area forward (as shown) as the bottom is narrow enough to prevent slamming on such a small boat.

This chined hull is used on Flica, Mirage and Romany and is a close approximation to a round bilge hull, but built in flat panels

This is a deep V hull used on Surfsong, Windsong and Mira (deep V version)

This is the chined V hull used on Meander, Rhea and Ondina. If these larger boats had a conventional V hull then either the gunwale or keel panel would have to be very wide so that the hull had the correct displacement. By adding a soft chine the lower hull section can be well flared, while the topsides remain nearer vertical. This hull shape has the added advantage that the hull panel is stiffer and, as each section is smaller, it can be easier to make.

This continuously curving hull shape is used on Wizard, Sango and Wizzer. It has a similar below-waterline shape to a Strider hull (for example) but the bulge in the topsides allows a vertical bow to be drawn while keeping a good flare forward to prevent nosediving. It also adds to the interior room, especially at shoulder level. These hulls can be built in strip planking or foam sandwich but it is harder to build than the small knuckle hull shape.

This "Small Knuckle" round bilge hull is used on Strider, Shadow, Merlin, Gwahir, Skua, Gypsy (round bilge version), Mira (round bilge version), Scylla, Nimbus, Rhea (round bilge version) and Cirrus. This shape is easier to make than the one below. The knuckle is small and is usually made from solid timber (eg 2" x 1"). Even so it has proven effective at reducing spray and slamming. The hull bottom can be double diagonal plywood or strip plank. The topsides of both this hull shape and the one below can be strip plank or sheet plywood. Alternatively both knuckle designs can be built in foam sandwich with a flat panel topside panel.

This is the "Large Knuckle" hull used on the Scorpio, Javelin, Sagitta, Eclipse and Transit. It is the most sophisticated shape I draw, and takes the longest to build. The large flare increases space inside and cuts down on spray. The angle of the hull at the WL is actually higher than on other hull shapes. That means that it sinks relatively slowly as you add weight. A big advantage for cruisers. But it also means the boat doesn't pitch and heave so much, ie vertical movements are reduced. That is because it is (slightly) harder to make the boat sink as it goes through waves. All minor differences but they add up if you are looking for the best all round shape.

Having said that, if you are planning on using LAR keels rather than daggerboards then you will probably be better off with a flat panel hull. There is no point in taking just one part of the overall design to the limit, you have to balance the trade off for the whole boat. So don't fit daggerboards and cheap sails! Makes no sense to me.

Catamaran Design Guide

Spectacular sunsets in the Pacific turn the horizon into a brilliant spectrum of gold and orange colors.

Copyright © 2006, 2008 by Gregor Tarjan. Click here for terms of use.

performance, yet desire high daily averages and passage times, which should be as short as possible. When choosing a large multihull, sailors look, above all else, for safety and comfort, long before the consideration for flat-out speed comes into the discussion. Nevertheless, performance is a highly important design consideration. No catamaran sailor wants to sail slower than a same length ballasted keelboat. Below are some EVALUATION & COEFFICIENTS useful coefficients, which will help compare monohulls and multihulls objectively.

Bruce Number (BN)

below "Indigo," a magnificent Wormwood 70, sailing in sparkling Caribbean waters.

Wormwood Catamaran

Various multihull characteristics and design features can be expressed in mathematical formulas. Their results are crucial and will give prospective owners a basis of comparison between different types of catamarans. These numbers are important, as they eliminate ambiguity and clearly display various advantages or concessions of a design, which would be hard to quantify any other way. Mathematical coefficients not only will provide insight into a boat's performance in varying conditions, they also reflect concerns about loads to be carried safely, speed and stability.

We have already mentioned the Displacement/Length and Sail Area/ Displacement ratio in our chapter on Multihull Advantages, illustrating the point of a multihull's efficiency. Let's look at some other coefficients that give us an indication of a boat's performance.

What is performance and how do we really measure it? Most people who buy a cruising catamaran are not really interested in racing

The Bruce Number is very similar to the Sail Area to Displacement ratio although the formula is slightly different. It is the square root of the sail area in feet, divided by the cube root of the boat's displacement in pounds:

SA = upwind sail area (mainsail and 100% jib)

Displ = weight of the boat in pounds

Similar to the Sail Area to Displacement ratio, the higher the coefficient the faster the boat and better is its performance in light air. Typically a BN of 1.1 will be the threshold between fast and more sluggish multihulls. A heavy displacement monohull might have a BN of .7, whereas a modern cruising catamaran shows a BN of 1.3. Offshore multihull racers can have BNs of 2.0 and higher. The BN will also tell us about a catamaran's ability to withstand stronger winds before reefing. A boat with a higher BN is usually overcanvassed in strong conditions and will have to be reefed earlier than one with a lower coefficient.

On the other hand, they will be able to produce more "power" than their counterparts in lighter winds and perform better.

Sail Area to Wetted Surface (SAWS)

SA/WS = Sail Area Wetted Surface Coefficient

SA = upwind sail area

WS = total underwater surface area (hull and appendages)

This formula simply divides the upwind sail area of the boat (mainsail and 100% jib) by the wetted surface. This coefficient will give us a statistical indication of the multihull's lightair performance since in low wind conditions skin friction becomes an important factor. Monohulls can have coefficients of at least 7% more than multihulls.

Hull Fineness Ratio (HFR)

The Hull Fineness Ratio, known as the hull's beam-to-length ratio, is an interesting number. It is derived by simply dividing the waterline length of the hull by the waterline beam of the hull.

Max. WL/Max. Beam WL = Hull Fineness Ratio Max. WL = length of the hull at waterline in ft. Max. Beam WL = beam of the hull at the waterline in feet.

Monohulls, when compared to multihulls, have low hull/fineness ratios. In Part 1 of this

Catamaran Proportions

book, discussing "Efficiency," we saw that ballasted keelboats are limited to Archimedes' principle of hull speed (1.34 x VWL). Multihulls do not have these theoretical barriers, because their hulls are narrower.

The thinner the hull the faster it will be able to travel through the water. But, attention! It will also carry less unless you are on a mega cat. Typically, a 40' cruising catamaran's HFR will range from 8:1 to 10:1. Dennis Conner's above While sailing under spinnaker and experiencing virtually no roll at all, guests will always find a comfortable spot to relax on the foredeck, an impossibility on a monohull.

There are various methods of calculating the transverse stability of a catamaran. One of the simplest and most utilized techniques is establishing a relationship between the height of the Center of Effort (CE), displacement, beam and sail area. Multihull designer, James Wharram added safety factors of 20% to compensate for gusts and the dynamic environment of the ocean. Another method is described in the text below.

Multihull Stability & Capsizing Moment d - Displacement (kg) x half beam (m) max ~ Sail Area (sq m) x Height of Center of Effort (m)

P max = maximum pressure exerted onto sails

Multihull Stability & Capsizing Moment

Trimaran Center Effort

height of sailplan CE

half overall beam (half hull beam)

racing cat "Stars and Stripes" had a 16:1 HFR. Of course, the larger the boat, the narrower the hulls will become in comparison to its length. For example, the HFR of a 100' luxury catamaran may be 12:1, providing it with a high speed potential. However, monohulls can show HFRs of 3:1, though the comparison is complicated as their angle of heel affects the measurement.

One has to be very careful when analyzing the Hull Fineness Ratio of a cruising catamaran, because other factors such as the actual shape of the hull cross sections (Prismatic Coefficient, PC) can throw the analysis off balance. Go-fast sailors like to think that fine hulls are always fast. That is not necessarily true because a slim hull could have a large underwater volume, thus slowing it down. Consequently, a wide waterline-beam hull could have less drag than a narrower one. It could have a shallow underbody (low PC), which would be beneficial to load carrying (Pounds Per Inch Immersion Number, PPI) and early surfing characteristics at speed.

Stability Coefficient (SC)

This mathematical formula has been devised by the distinguished catamaran designer and sailor James Wharram and his team. This coefficient analyzes a multihull's ability (in a static environment) to resist capsizing due to wind.

( 0.682 VW x (.5 Boa) ) x .555 = CW .00178 x SA x h

W = Wind speed, apparent, in mph CW = Critical Wind Speed to capsize in mph SA = upwind sail area in sq ft. h = height of Center of Effort (CE) of total sail area

Boa = Beam overall

This formula will tell us how much wind it will take to overturn our multihull. By instinct we will know that a catamaran with a wide stance and a conservative sail plan will be very stable offshore. The SC formula will inevitably illustrate that a wider beamed catamaran with a tall sail plan will be as resistant to wind induced capsize as a short-rigged, narrower boat. This is not so if one considers the chaotic environment of waves and the real world of heavy weather sailing. It is interesting to note that a wide beamed boat (regardless of the SC) is more resistant to capsize in seas due to the effects of a higher moment of inertia. In an open-ocean environment, which is everything but static, the SC formula has little meaning. Nevertheless, it serves as a good basis to evaluate stability as a factor of wind force.

below When the wind suddenly comes up, all that is needed is a couple of turns on the jib furler to quickly reduce the headsail size. The catamaran will hardly sail any slower, but feel more comfortable.

Ship Hull Fineness

Wide hulls and a large overall beam will increase the overall righting moment of a catamaran. A word of caution: Excessive beam will reduce the fore and aft stability. Designers strive to compromise hull fineness ratios, place heavy weights towards the CG (Center of Gravity), and engineer hull and overall beam to achieve a seaworthy balance, which is safe, yet provides ample liveaboard accommodations.

Catamaran Stability Considerations

Seaworthy Catamaran

Diagonal Stability & Beam-to-Length Ratio (BLR)

Stability of a multihull, or the resistance to capsize, should be seen as three components. Athwartship Stability is one well-publicized type and the one often talked about. The other much more important types are Fore and Aft and Diagonal Stability. Fore and aft stability is established by the relationship between the boat's waterline length and the distance between the hull centerlines. It will reflect the catamaran's resistance to tripping. This relationship should be in the vicinity of 39% to 42%. For a seaworthy cruising multihull it is important maintain the proper ratio between length and beam, which, in turn, balances equal amounts of athwartship with diagonal stability. The goal should be to prevent the possibility of a sudden discrepancy of powers between fore and aft and sideways resistance. Most of today's multihulls keep these two component forces in equilibrium, making them extremely seakindly and safe.

Some early design multihulls were very narrow, partly due to the material limitations of that time. But things have changed. Contemporary composite construction allows designers to build wider boats without compromising stiffness. Production catamarans of today have a wide stance and have the benefit of greater safety margins in gusty wind conditions than their older cousins. Multihulls are sophisticated structures and true modern miracles. They provide a more comfortable ride and more interior room. Thanks to modern materials they weigh less and perform better than catamarans built only 10 years ago.

Some catamarans, especially production boats, which are very popular in the charter fleets, are growing wider by the year. The businesses who rent these beamy monsters adore them. Lots of room plus open decks are ideal for clients and the bigger (wider) the boat, the more paying guests can share the fees. But there certainly is a limit as to how wide is too wide. Extreme beam can be dangerous. It can lead to instability fore and aft and to excessive bridgedeck slamming, as the relative distance from the bridge deck to the water will decrease with an increase in width. A vessel with excessive beam might seem stable athwartships, but it will compromise overall stability.

We know that multihulls can, in extreme cases of seamanship error in wild storms, be thrown over from any side - front, back and beam-on. The best examples of this phenomenon are racing multihulls, especially Formula 1 trimarans, which have fine hulls for speed and huge sailplans to provide driving power. They are initially extremely stable athwartships (High Beam-to-Length Ratio), but have a tendency to become unstable fore and aft. They will surf down waves and reach a point where the power of the sails, and speed, will exceed the ability to keep the bows out of the water and the boat will pitchpole. This is the reason why catamaran designers usually draw their multihulls with a Beam-to-Length relationship of between 50% and 55%. The longer the vessel the lower that percentage becomes.

I am currently involved in the "Gemini" project, which presents an example. It very well might become the world's largest sailing catamaran. She will have an overall length of 145 feet, yet her beam will "only" be 54.4'.

Stable Catamaran Dingy

Please, don't worry. "Gemini" will not be tender and tip over in the slightest breeze. On the contrary, this monster will be one of the most stable craft afloat, although the beam-to-length relationship is only 37%. The relatively low beam-to-length ratio also involves the fact that the boat would be too heavy and building costs would be prohibitive if she were to have a standard 52% BL relationship. Most importantly, could you imagine turning a 75-foot-wide boat?

above Asymmetric spinnakers on furlers are great inventions. They add instant sail area, yet can be doused in a matter of seconds when the wind picks up strength.

Catamaran Underwing

above Although this Edel 35 was a good-looking and popular catamaran, it suffered from excessive bridgedeck pounding, which was caused by only several inches of clearance between the saloon's underwing and the sea.

Obviously there is a sweet spot in the beam vs. stability question. Designing too beamy a boat will also necessitate more freeboard to preserve bridgedeck clearance which, in turn, will increase windage and complicate maneuvering. Unless sophisticated aramid construction methods are utilized, more beam will also add more weight and stress to the structure. Adding more mass will, to a certain point, help make the boat more stable, but where do we stop? Is it better to add weight or width to make a boat stiffer? Of course, both characteristics are interrelated as a beamier boat normally is also heavier. Just adding weight to a catamaran simply to make her more stable will not pay off. Consequently, making a boat too wide might increase living space yet it will also burden the structure, require a beefier manufacture, and yield an even heavier boat. Needless to say, a boat which is too wide will also create practical restrictions such as maneuvering, the ability to haul the vessel and much higher building costs.

Beam has a great effect on bridgedeck clearance, which is one of the most vital characteristics of a good cruising catamaran. As standard practice, the well-known rule of 1" of bridgedeck clearance for each foot of beam was a safe way to prevent excessive wave slap. The wider the beam the more the relationship changes and the necessary height of 1" per foot of beam needs to be increased to 1.3" or more. In the extreme case of overly square boats, that number will have to be closer to 1.8" per foot of beam. This will have a negative effect on any seaworthy multihull that has a bridgedeck saloon. The wide beam will necessitate a high cabin sole to remain a safe distance from the waterline. In order to provide standing headroom, the coachroof might be higher than practical, which could result in a boxy, high-windage multihull. Not only will this be unattractive, but also raise the Center of Gravity (CG) which really should be kept as low as possible.

More overall beam on the other hand (given that there is still sufficient bridgedeck height) has a less known benefit, as it reduces the possibility of hull-wave interference, which is particularly important for fast designs. The wave interaction between the hulls can lead to additional resistance, and especially in an agitated sea state, the formation of wave crests can pound the bridge deck. Most early narrow-beamed catamarans suffered from this phenomenon,

Ultimately, a boat's design has a major influence on its ability to stand against the forces of nature, and to keep occupants safe. Manufacturing excessively wide catamarans is like trying to market monohulls with super deep-draft keels. Both are totally impractical. We designers have to make sensible compromises and learn from past experiences of what has worked at sea by balancing the benefits of a wide boat with its disadvantages.

below This narrow-hulled Outremer 64 Light has completed her third circumnavigation with the same owners. Note the smooth underwing clearance, lacking any protrusions or steps.

Outremer Standard

"A great cape, for us, can't be expressed in latitude and longitude alone. A great cape has a soul, with very soft, very violent shadows and colors. A soul as smooth as a child's, and as hard as a criminal's. And that is why we go!"

~ Bernard Moitessier

Catamaran Underwing

Dinghies, windsurfers and every imaginable type of water toy can be stored conveniently on large catamarans and easily launched from the wide transom steps for shore-side pleasures. Note the twin life rafts located in special compartments on the massive aft crossbeam.

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Readers' Questions

What length should a stub keel be to waterline length on a catamaran?
There is no set rule for the length of a stub keel on a catamaran in relation to its waterline length. The length of the stub keel will depend on various factors, such as the size and design of the catamaran, intended use, and specific requirements of the boat builder. Generally, the stub keel on a catamaran is designed to provide stability and improve sailing performance, so it is important to consult with a naval architect or boat designer to determine the appropriate length for a specific catamaran.
What is a 16 passenger catarmarn like?
A 16-passenger catamaran is a type of boat or vessel specifically designed to carry 16 people comfortably. Catamarans are multihull boats with two parallel hulls, which are connected by a deck or a structure. They offer stability, speed, and efficiency in the water. A 16-passenger catamaran can vary in size and design, but generally, it will have enough seating or lounge areas for all passengers. It may have indoor cabins with beds or seating areas, as well as outdoor spaces for relaxation or socializing. These boats often come equipped with amenities such as bathrooms, kitchens or galleys for meals, and sometimes even entertainment systems. The catamaran's size can influence its specific features. Some catamarans are designed for day trips or shorter excursions, while others are built for longer journeys or overnight accommodations. Additionally, they can be used for various purposes, such as whale watching, diving trips, ferry services, or private charters. Overall, a 16-passenger catamaran provides a comfortable and stable platform for small groups or gatherings, allowing passengers to enjoy the beauty of the water while ensuring safety and comfort.
Is the catamaran hull floor always on the waterline?
No, the hull floor of a catamaran is not always on the waterline. The design of a catamaran allows for the hulls to be elevated above the waterline, reducing drag and increasing speed. The position of the hulls in relation to the waterline can vary depending on factors such as the weight distribution, load, and sailing conditions.
How close to a catamarans design reefing points should you go?
You should always be careful when approaching reefing points on a catamaran and stay as far away as possible. Generally, you should aim to stay at least 10 meters away.
What keel to length ratio for catamarans?
The keel-to-length ratio for catamarans typically ranges from 0.1 to 0.25.
Is 70% length to beam ok for a catAMARAN?
Yes, it is generally accepted that a catamaran should have a length to beam ratio of between approximately 6:1 and 8:1. Therefore, a 70% length to beam ratio would be within an acceptable range.
What is the waterline length to baem ratio of a typical cruising catamarans?
This ratio will vary depending on the type and size of the catamaran. Generally, the ratio should be between 1:1.5 and 1:2.5, with 1:2 being the most common.

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What's the best shape for a fast & efficient catamaran hull?...

Discussion in ' Boat Design ' started by Seagem , Jan 21, 2009 .

Seagem

Seagem Junior Member

Doing research on fast & efficient hull shapes for a 25' cruising catamaran capable of 22/25 knots cruise and 30 knots top speed, while still providing reasonable performance at lower speeds, I found the following: 1) Efficient planning shape, foil assisted:Corsair 22 Foiler The boat does 50 mph top with twin 90hp motors and cruises happily at 30 mph with better than 3 miles/gallon fuel consumption. Its asymmetrical hull design allows it to bank in turns, unlike most other catamarans.. Description: http://floridasportfishing.com/magazine/product-reviews/boats-reviews/corsair-foiler-2200.html Potential drawbacks: not efficient at displacement speeds 2) Efficient displacement hull: Prowler 9 meter Description: http://www.schionningmarine.com.au/www/page.cfm?pageID=195 Twin 50hp outboards will cruise this catamaran at 17 knots using 1 liter/mile or 3.8 miles /gallon with top speed of 21 knots, thanks to a fineness ratio of 15 to 1... Drawback: Top speed cannot exceed 23 knots, as this is a displacement hull... 3) Not so efficient semi-displacement hull: VT650/950 The larger version of this design with the unusual asymmetric chines, the VT950 cruises at 17 knots, using 2.2 liters/mile (1.7 mile/gallon) and tops out at 26 knots with twin 140hp outboards. Many advantages: sharp entry at slow or high speeds, load carrying ability aft where the weight is usually concentrated, easy access to hulls from bridgedeck and clever location of the outboard engines, which have a clear water flow while keeping the stern platforms free. This also moves the engine weight and prop further forward, reducing potential aeration in rough seas. Description: http://www.schionningdesigns.com.au/login/pages/images/StudyPlanProwler950VT.pdf One major drawback: the hull shape has too much wetted area which affects its efficiency. I suggested tapering the "V" section to nothing about one third before reaching the stern, but Schionning says it increases the drag... 4) Efficient semi-displacement hull: Chilkat 30 This boat cruises at 30 knots with 3 miles/gallon fuel efficiency and tops out at42 knots with twin 225hp outboards. However, it still cruises at 25 knots and tops out a 43 mph with twin 150's... Description: http://www.blackfeatherboats.com/power_catamaran_boat.cfm Drawback: the bridge deck may be too low and pound in a seaway... There is also the Sea Knife hull design which may be suitable, but will require some expensive R&D to make work satisfactorily: http://www.yachtforums.com/forums/technical-discussion/2701-trimarans-bladerunner-4.html Any suggestions of hulls that might fit the bill would be welcome...  

sabahcat

sabahcat Senior Member

Are you still trying to get queen sized beds, dinettes, shower toilet and a few hundred litres of water onto these hulls? Does it still need to be a trailerable width? If not, option 1 although I would suggest a boat with foils may not have got the hull shapes right to start with. If you want the beds etc then option 2, but like was said in your other thread, it will be high sided due to bridgedeck clearance. Thems the rules.  
Good question.... sabahcat said: ↑ Are you still trying to get queen sized beds, dinettes, shower toilet and a few hundred litres of water onto these hulls? Does it still need to be a trailerable width? If not, option 1 although I would suggest a boat with foils may not have got the hull shapes right to start with. If you want the beds etc then option 2, but like was said in your other thread, it will be high sided due to bridgedeck clearance. Thems the rules. Click to expand...

[​IMG]

mark775 Guest

There is a Chilkat thing here and the owner loves it but the outboards are ripping the the back of the boat off... Most in this neck of the woods have given up on little cats that plane, by the way because of the hobby-horsing and general thrashing.  

terhohalme

terhohalme BEng Boat Technology

http://glacierbaycats.com/show  

robherc

robherc Designer/Hobbyist

Hmmm... I know you don't like the speed limit of a displacement hull, but it's going to be by FAR your most efficient through-the-water (at least under varied speeds). If I were to build a boat for myself, with the same qualifications you listed, I'd be tempted to go with fine, mostly-displacement hulls (if not fully displacement), but I'd still foil-assist it. With the foil-assist, you can dramatically reduce the displacement of the hull, and thus the wetted surface, w/o having to plane, so that seems like the way to go for me...but I still prefer to sail also, so the efficiency thing is pretty paramount to me, while I'd be quite happy with 25knots...and 0litres/nautical mi.  
Seagem said: ↑ The hulls are a cleverer design than appears at first sight: notice the main chine coming down the bow and turning down below the slightly convex bottom to prevent the lifting water flow under the hull from escaping sideways. Also the other chine just above the waterline that has a rubbing strake: the fineness ration is a narrow 18 to 1... Click to expand...

eponodyne

eponodyne Senior Member

I'd go with option 2. 20 knots is really hauling bass, let's not forget that 20 knots hour after hour adds up to 550 statute miles in a day. How far do you really need to go, and how fast do you really need to get there? Who are you really trying to impress?  
mark775 said: ↑ There is a Chilkat thing here and the owner loves it but the outboards are ripping the the back of the boat off... Most in this neck of the woods have given up on little cats that plane, by the way because of the hobby-horsing and general thrashing. Click to expand...
Seagem said: ↑ As mentioned earlier, the boat is 25' plus the swim platform, which will give a total of close to 27' and it may be necessary to still go longer to help carry the fairly substantial tankage necessary... Click to expand...

Alik

Alik Senior Member

From our experience, hull shape is secondary issue (unless it is too bad or not match the desired speed). Weight - this is key point of fuel efficiency. Make Your boat light to be fuel efficient. For planning cat, a lot of weight savings can be obtained by light bottom. Say, using AirexR63 and Kevlar/E-glass composite on bottom will give 1200 kg of hull structure for 10m cat, while for normal WR/CSM the weight is 1900 kg.  
Seagem said: ↑ A foil addition remains an option and it has been done successfully on a 46' displacement cat built by Alwoplast as a retrofit: speed increased by an amazing 35%... The fastest I was ever able to sail my Antigua 37 catamaran under spinnaker alone on an Atlantic crossing to the Caribbean was 15 knots: above that, the bows started to bury and waves would reach the foot of the mast by the time I took down the spi. Click to expand...
The Chilkat is by Black Feather Boats. It was an option pic posted above.  
50' Wave piercer by Gold Coast yachts on St Croix... Please, click on the link below to enlarge the photo and see the lay-out... 50' Wave piercer by Gold Coast yachts on St Croix... Owners comments: Mosler claims his boat burns 3 gph at 10 knots for 3.33 nmpg and 11.1 gph at 20 knots for 1.80 nmpg. His top speed is over 26kts with a 24kt cruise with the d3's Volvo 190hp at just over 14 gph. The length to beam of each of my hulls is about 16:1, and the bridge deck is about 3ft over the surface at the rear, sloping up towards the bow, so it can quarter some very high seas at full cruise without slapping, though the wind will blow a lot of spray on the upper aft deck at high speeds. Warren Mosler said: I took 13 people to St. Thomas from St. Croix yesterday quartering 8 ft seas at about 20 kts. picked 4 in St Thomas, had lunch in St. John, back in St. Croix less then 2 hours later. All sat comfortably on the upper aft 'sundeck' above the aft berths (and no one got sea sick). http://pmyeditors.blogspot.com/2008/01/is-it-finally-happening-are-power.html  
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And your point? 25feet has grown to 50feet? Similar concept Sheer Khan http://www.charterworld.com/index.html?sub=yacht-charter&charter=luxury-catamaran-sher-khan-715 http://www.incat.com.au/  

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DutchCat: The 15p-per-mile-marvel motor catamaran

  • Electric boats

This electric or hybrid-engined motorcat takes fuel-efficiency cruising to a new level

Evolution rather than revolution is the name of the established boatbuilder’s game. The finish and layout of current models might be a quantum leap ahead of where they were a decade ago, but conceptually little has changed. Even new ideas such as Azimut’s Magellano range with its ‘dual-mode’ hull capable of running comfortably at displacement and semi-displacement speeds, offer only tiny gains in fuel efficiency. But with ever more emphasis on environmental concerns, pressure for change is growing in a motor boat world where 1mpg for a 40ft planing boat is the norm. Enter Jan van Eck, the man behind the DutchCat. Rather than wait for the mainstream builders to rip up the rule book, he has simply started without one and created what he believes to be the true future of motorboating.

DutchCat main deck

His vision starts with the hull shape. It was seeing catamaran sailing dinghies consistently outperform monohulled ones that convinced Jan twin hulls were more easily driven. Of course, motorcats are nothing new but most existing powercats are far wider than monohulls of a similar length, making them unwieldy for inland use. The Fountaine-Pajot 44, for example, has a beam of 6.6m, compared with the monohulled Azimut Magellano 43 at 4.4m. The 41ft DutchCat comes in at 4.9m, far closer to monohull territory and crucially granting it access to the French canal system, where locks are typically just 5.2m wide.

One boat, two versions

Designed by Vripack and RCD Category B-rated, there are two versions of the DutchCat hull. The ‘Comfort’ version has a round bilge form and long shallow keels, similar to a sailing yacht, and is designed to run at lower speedswith smaller engines. The ‘Sport’ hull is a more traditional powerboat form with sprayrails and tunnelled props for higher speeds, toppingout at 22 knots with bigger motors. Crucial though hull design is, it’s only one part of DutchCat’s energy efficiency equation. Similar blue-sky thinking has been brought to bear on pushing that ultra efficient hull shape through the water. Perhaps the most radical power source is an all-electric setup that uses twin Kräutler 48V 10kW (14hp) or 15kW (21hp) motors connected to conventional shaftdrives for a maximum speed of 8.5 knots and a cruising gait of 4 to 6 knots. Gel traction 48kWh batteries are standard, with Lithium ones an option. DutchCat claims about seven hours of cruising at 5 knots and about ten hours to recharge from a 16A supply. Pure diesel is an alternative. Comfort-spec boats rely on a pair of Yanmar 3YM30 3-cylinder 29hp engines to yield about 11 knots flat out and cruise at 8 knots. Opting for the Sport hull configuration allows twin Yanmar 4BY3 150hp engines to boost maximum velocity toward 22 knots.

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DutchCat engine

Out on the water

We had the chance to try the diesel hybrid setup with twin 29hp Yanmars. Two hulls mean two bow thrusters – a pair of 55Kgf Vetus units combine with wide-spaced shafts to make wriggling out of Amsterdam Marina and on to the IJ fairly painless. Despite being the first boat from this new company, it feels well engineered with commendably low noise levels at 2,500rpm which equates to a 7-knot cruise. But to really drop the decibels, switching to all-electric is the way to go. The electric motors use the same engine controls as the diesels, so it’s just a case of switching off the Yanmars, engaging the electric motors and then throttling back up. Under electric power there are two obvious differences. Performance is muted – 5 to 6 knots is as much as you’ll get if you want meaningful range. But so is noise. The closest comparison would be sailing, with the gentle gurgle of water around the hulls the only sound. This speed is more than adequate for inland waterways and should allow for 5.5 hours of cruising from the 38kW battery pack.

Continues below…

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So how does that efficiency translate to cost? Like any boat, travelling at displacement speeds is the key to the biggest savings – DutchCat hasn’t rewritten the laws of physics. Nonetheless, with the smaller diesel engines, the boat is burning under a gallon an hour at 7 knots, which is less than half that of the slightly longer but narrower hybrid-hulled Magellano 43 (albeit without its 22-knot top end). With marine diesel currently hovering at around £1/litre that’s about £4/hour. At 5 knots under electric power, it’s using roughly 5.5kWh. With 1kWh of mains electric costing 13.5p, that’s about 75p/hour or a miserly 15p per mile!

So is this the future? Well, it’s certainly one of the most credible attempts to create something truly new and efficient that we’ve seen for some time, and it’s telling that it comes from a brand new start-up with zero boatbuilding history.

Hugo’s take

Combining the efficiency of a catamaran hull with the low-running costs of a diesel-electric hybrid makes perfect sense, particularly for inland cruising. I reckon DutchCat are on to something.

At a glance…

Build: GRP RCD: B for 12 people LOA: 41ft 2in (12.55m) Beam: 16ft 1in (4.90m) Draught: 2ft 9in (0.85m) Displacement 12 tonnes Price: from €467,533 ex VAT Contact: DutchCat   

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Capilano Maritime Design Ltd.

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High-Efficiency Catamaran Design

The contributor.

The National Research Council Canada (NRC) as represented by its Industrial Research Assistance Program (IRAP) funded the research in 2020 and 2021.

The objective of the research project was to develop an adaptable catamaran ship design valid within a certain design space given by the main dimensions (length, draught, beam, displacement, number of passengers and operational range).  The aim is to be able to design variants efficiently, quickly and with high accuracy and thereby limit the technical risk for both the client and Capilano Maritime Design Ltd.

The design platform is intended for various applications such as commuter passenger ferry, harbour cruise, offshore supply, research vessel etc.

The catamaran designs in the range of the following main dimensions were explored:

efficient catamaran hull design

The initial focus was on small passenger vessels with lengths ranging from approximately 20 to 40 metres.   Specific areas of interest were catamarans with low l/b ratio, low Froude number (low speed to length ratio) and/or high displacement to length ratio.

The main technical risks identified are: resistance, wave making, propulsion and weight.

In order to evaluate a large number of hull form variations a CFD set-up was validated using published hull forms and model tests results of the catamaran Delft 372 as well as a comparison was made to empirical formulas for resistance calculation of catamarans.

The CFD calculation results, empirical formulas and the published model test results for the Delft 372 agreed well for both resistance, dynamic trim and sinkage, as shown in below figure.

efficient catamaran hull design

This validated set-up was subsequently applied using different hull shapes to determine their hydrodynamic performance.

The hull forms that were part of the design study had a considerable higher displacement than the validation case (Delft 372), in the order of 60%, and therefore also distinctively different hull characteristics. Thanks to the extensive CFD studies we determined the limitations and accuracy of these empirical formulas at or beyond their application range.

In parallel, a structural layout based on DNV-GL’s rules for high speed and light craft (HSLC) rules was prepared and utilized for a FEA analysis to investigate vulnerable spots, accurately determine design margins and optimize material allocation hence minimizing structural weight.

During the course of the research project several design tools were developed that enable CMDL to develop catamaran concept designs in a shorter time frame while increasing the level of detail and confidence, thus reducing the technical risks and consequently reducing design margins earlier.

  • Remmlinger, “The resistance of the Delft 372 Hull”, 2014
  • Van’t Veer R. “Experimental results of motions and structural loads on the 372 catamaran model in head and oblique waves.” TU Delft Report, N.1130, 1998
  • Van’t Veer R. “Experimental results of motions, hydrodynamic coefficients and wave loads on the 372 catamaran model” TUDelft, 1998
  • Broglia R, Zaghi S. “Calm water tests for the DELF 372, Catamaran model at several hull separations”, INSEAN, Report, 2010
  • Broglia, B. Bouscasse, B. Jacob, A. Olivieri, S. Zaghi and F. Stern, “Calm Water and Seakeeping Investigation for a Fast Catamaran” 11th International Conference on Fast Sea Transportation, FAST 2011, Honolulu, Hawaii, USA, September 2011
  • DNVGL-RU-High Speed and Light Crafts- Part 3
  • DNVGL-CG-0127- Finite Element Analysis
  • Liang Yun, Alan Bliault, Huan Zong Rong, “High Speed Catamarans and Multihulls”, Book
  • Liao PK, Quemener Y, Syu YC, Chen KC, & Lee YJ, Validation of Practical Approaches for the Strength Evaluation of High-speed Catamaran under Beam and Quartering Seas, The 31st Asian-Pacific Technical Exchange and Advisory Meeting on Marine Structure, 2017

Category: Analysis & Consulting

Client: National Research Council of Canada

Services Provided: CFD, FEA, Development of Tools for Structural Design, Weight Estimation and Wake Wash

Date Completed: 2021

Location: North Vancouver, BC

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Six Amazing Boat Hull Designs

  • By Dean Travis Clarke
  • Updated: October 25, 2016

Six Amazing Hull Designs

The American boating consumer bears a remarkable psychological profile when it comes to wants and needs.

A cursory glance at the lines of most boats proves that profiles haven’t changed dramatically over the past 60 or so years. Certainly, construction methods such as resin infusion and injection molding have altered business as usual, and ingredients have also changed to include all manner of space-age composites, epoxies, paints, computer mapping for engines that produces vastly greater horsepower from smaller blocks, and so on. Even propulsion has changed with the advent of pod drives and big outboards. But here’s the weird part: Any time a designer or builder introduces a model that looks significantly different, whether it is Euro-styled or functionally clunky, it fails. It doesn’t matter how well the boat performs, the typical boater rejects it because it doesn’t look like what he knows. We, as an enthusiast niche involving boats, are horribly set in our aesthetic ways.

Look at how well multihulls handle heavy seas. When it comes to seakeeping ability, efficiency and performance, the catamaran has a lot going for it, as anyone who happened to catch some of the most recent America’s Cup racing can attest. And yet, to date, production multihulls have enjoyed only moderate acceptance by boaters.

Here are six of the latest hull-design innovations and technologies being used elsewhere in the maritime world that we will likely never accept for our recreational boats — even though they all work well.

Six Amazing Hull Designs

Wave-Piercing Hulls Most accounts cite wave-piercing technology as coming on the scene around the start of the 20th century. However, it has been employed as far back as the times of the Phoenicians and ancient Romans. The design concept consists of a bow with little buoyancy, a hull that slopes inward from the waterline and, ergo, a large reduction in wave-making resistance. While it works well in heavy seas, the drawbacks include reduced interior volume forward and a very wet ride because the waves come up and over the bow as a matter of course. Wave piercers fell out of favor for a period of time due to these same drawbacks but have recently enjoyed a resurgence of popularity because of their dramatic fuel-efficiency gains.

Six Amazing Hull Designs

Stepped Hulls OK, this hull form has achieved a certain level of acceptance in our recreational boats, mostly in performance boats or offshore center consoles. But why isn’t it more popular? The stepped bottom has been around as a V-bottom refinement since at least 1912. Steps are grooves in the hull stretching outward from the keel to the chines. Most hulls sport one or two steps per side. And a vessel should really be capable of cruising in excess of about 30 knots for a stepped hull to be worthwhile. Steps work by allowing air to be “injected” against the running surface, breaking contact between part of the hull and the water, which in effect turns the running surface into numerous short, wide planes, rather than one long, narrow one.

How much the hull surface contacts the water directly determines the amount of drag a hull suffers. Steps (also called vents) decrease the amount of hull contacting the water (called the wetted surface), thereby decreasing drag, increasing speed for the same horsepower, and increasing fuel efficiency. It all sounds good. But steps also come with potential drawbacks. Though modern deep-V designs have enough deadrise to counteract the problem in most cases, stepped hulls have been known to suffer from transom slide in sharp turns at speed. They also require attention to loading and trim because the steps need the proper angle of attack to function correctly; they don’t offer an advantage in flat, calm water; and they require a special trailer.

Most owners of stepped-hull vessels are experienced and want to travel at high speeds in moderate to heavy seas, and/or achieve good economy and range. Yet to date, performance and center console builders aside, only Regal Boats, with its FasTrac hulls, and Formula have committed to using steps in production cruisers and sport boats.

Six Amazing Hull Designs

Asymmetrical Twin Hulls This unique design concept comes from the drawing board of Larry Graf, the pioneer who put power catamarans on the map here in the U.S. when he founded Glacier Bay Boats in 1987. His new company, Aspen Powerboats, employs a cat design where one hull is narrower (35 percent) than the other. His patent calls it a Power Proa, and it relies on a single engine in only the wider of the two hulls. The hull shapes, alignment and placement compensate for the offset propulsion thrust, allowing the vessel to run straight and true. With only one set of running gear in the water, inherent appendage drag is reduced by 20 percent. Combined with the efficiency of the hull designs, overall fuel efficiency of the Aspen rises to an impressive 70 percent over monohulls of comparable size. Aspen won an award for the best 30- to 39-foot catamaran in the world in 2014.

Six Amazing Hull Designs

SWATH A quick glance might lead you to believe that a SWATH (small waterplane area twin hull) vessel is a catamaran. And it is but only to the extent that it has two hulls in the water with a bridge across the top. But that’s where the hulls’ similarities end.

Consider a submarine. Once under the surface, it runs stable, with no roll or pitching from wave action. All that wave energy remains on the sea surface. That basically explains how a SWATH design functions.

If you’ve ever dived under a wave at the beach to avoid being smacked by it, you know that the water beneath the wave is calmer. SWATH minimizes a vessel’s volume where the water meets the air (which is where all the wave energy is at its peak). The bulk of the vessel’s displacement and buoyancy runs beneath the waves, affording amazing stability, even in big seas and at high speeds. Please think of high speeds as a relative term here, as this is not a planing hull. What SWATH does provide, however, are a wide, stable deck and unsurpassed ride quality, especially in rough seas.

Drawbacks to SWATH designs include the fact that each hull must be custom designed. Draft runs deeper than standard hulls (especially planing hulls). The underwater “torpedoes” providing buoyancy must run parallel to the water’s surface, which requires a fairly complex trim-control system. And the underside of the deck must be far enough above the sea surface to avoid waves slamming up into it. Finally, SWATH vessels cost more to design and build than conventional hulls.

Six Amazing Hull Designs

Hydrofoils Once the strict province of commercial ferries and a few high-speed military vessels, the most recent America’s Cup has spurred hydrofoil acceptance to new heights. Will it catch on with powerboats?

The hydrofoil design acts exactly like an airplane wing, providing more lift than the drag coefficient the vessel produces, thereby lifting the entire hull out of the water. Only the hydrofoils remain in the water, unaffected by surface wave action. In fact, hydrofoils cut inherent resistance to zero while the hull is out of the water. In the case of power-driven boats, you still suffer drag from the propulsion system (prop, shaft or the like).

The most significant disadvantage to this system on recreational boats is definitely the deployment of the foils. Unless you want the added draft of these struts sticking down below your hull all the time, you must be able to extend and withdraw them — a complex engineering feat. There is at least one recreational powerboat employing hydrofoils: Twin Vee builds a catamaran with foils that don’t actually lift the hulls completely out of the water. It does improve fuel economy and ride stability nonetheless. Still, boats ride more smoothly in a sea and go much faster with hydrofoils. With the dramatic acceptance of this technology in sailing, is it only a matter of time before recreational powerboats incorporate foils into their designs?

Six Amazing Hull Designs

Ulstein X-Bow The Norwegian Ulstein Group has been designing offshore vessels since 1917. Presently, it has the notoriety of creating the most advanced bow design in history. The Ulstein X-Bow looks like it might be upside down, but it’s proven itself in more than 100 offshore support vessels to date. The X-Bow allows higher speeds and smoother rides in even the worst seas. Gone are the slamming and vibration that occur when the bow of a ship drops off a wave. It functions better on all points of sea, and its lower hydrodynamic drag substantially decreases fuel consumption. The X-Bow has proven so successful that Ulstein is in the process of creating an X-Stern design now.

You won’t ever see this on small recreational boats, but you can nod knowingly when someone points one out on a mega-yacht in the near future.

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Rossinavi Sea Cat 40 solar panels

Rossinavi launches first 43m hybrid-electric catamaran Seawolf X

Related articles.

Rossinavi has launched its "most innovative project" to date, a 42.8-metre hybrid-electric catamaran named Seawolf X . Construction was first revealed to have begun at the Monaco Yacht Show 2022, with the concept itself unveiled during Miami Design Week in 2021.

Exterior design is by Fulvio De Simoni Yacht Design , marking the first project presented by the pair since the 49.1-metre Aurora in 2017. It also marks the first multihull project for the shipyard.

A key characteristic of the model is her three "performance scenarios". On one-day trips, Seawolf X can cruise in full-electric mode for 100 per cent of the time; on multi-day trips, she can cruise for 90 per cent; and on transatlantic trips, she can still cruise in electric mode for 80 per cent of the time. When the catamaran is moored, a "hibernation mode" activates for reduced consumption – with the energy generated able to be given back to the quay or to a private property. She can recharge at the shore in five hours and supplies enough energy to charge up an entire villa.

Rossinavi has also developed an onboard artificial intelligence system, called Rossinavi AI, to analyse the operation of the vessel, predict the needs of guests and communicate with the crew on "lower-impact behaviours" and "conscious cruising". The AI can also monitor the battery pack to keep it in a range of 20 to 80 per cent.

Her exterior is low-profiled and reminiscent of a sports car, with Fulvio De Simoni Yacht Design seeking "to liberate their minds from preconceptions" around catamaran design. The team also integrated solar panels into Seawolf X and addressed hull efficiency by developing "lightweight solutions", including an anchor installation that meets weight standards while enhancing aesthetics.

New York-based design firm Meyer Davis have created an interior that "complements the cutting-edge yacht to bring relaxed luxury and sustainable design to its forefront," the shipyard said. The decor takes inspiration from nature, in particular the sun, the sea and sand.

Leisure highlights include a convivial cockpit centred around a pool, an expansive sundeck with sunbathing and living spaces, and a bow area that features a hidden pool and convertible home theatre. Accommodation is for up to 10 guests in four cabins located in the hulls.

"After years of study and construction, it is now a source of satisfaction and pride for us to witness the launch of project Sea Cat, now Seawolf X , the first hybrid-electric multihull vessel," said Federico Rossi, COO of Rossinavi. "This yacht showcases remarkable technological innovations in both power management and propulsion technologies, marking the beginning of a new chapter in next-generation vessels."

Seawolf X also carries the BlUE label, the shipyard' "sustainable" design philosophy established in 2022. Inspired by phytoplankton, the BlUE fleet absorbs sunlight during the day and utilises photovoltaic technology to convert it into energy. This energy is stored in advanced batteries and released at night, creating a bioluminescent effect "akin to glowing plankton".

The catamaran sits below the 500GT threshold with a beam of 13.8 metres and a maximum draught of two metres.

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  • 2 Get around

Mytishchi is a mid-sized industrial city in North Moscow Oblast , which borders Moscow to the southwest. It is perhaps Moscow Oblast 's principal industrial center, particularly for machinery and armaments.

Get in [ edit ]

A convenient elektrichka route (in fact, the first elektrichka route in Russia) runs frequently all day between Mytishchi and Moscow's Yaroslavsky Train Station. Rapid trains (Sputniks) bound to Pushkino and Bolshevo also stop here.

You can also get here pretty easily by taking the Kaluzhsko-Rizhskaya metro line to the end at Medvedkovo and there catch a bus or marshrutka to the Mytishchi center from the metro station.

Do [ edit ]

There is one of the biggest ice Arenas in Region (appr. 8 500 visitors) for ice hockey.

At summer: several pay beaches at Pirogovo water reservoir. Malibu pay resort (yachts, cafes etc)

Sleep [ edit ]

Go next [ edit ].

  • Pushkino is just a little farther along the rail and elektrichka lines running from Moscow through Mytishchi.

efficient catamaran hull design

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efficient catamaran hull design

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  1. Catamaran efficient hull design

    efficient catamaran hull design

  2. Catamaran hull design ~ Making of wooden boat

    efficient catamaran hull design

  3. Optimising Hull Lines for Performance

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  5. Check out our catamaran boat designs for the E-Cat, an economical

    efficient catamaran hull design

  6. CATAMARAN DESIGN: How Hull Volume & Bow Shape Affect Performance & Safety

    efficient catamaran hull design

VIDEO

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  4. Hammer Cat 35' Hull #2 Virtual Tour and Drone footage

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  6. Supercat 22 Catamaran @ Verde Passage Philippines

COMMENTS

  1. Catamaran Hull Design

    If you have fine hulls you can use a lower Cp. Most monohulls have a Cp of 0.55- 0.57. And that is about right for displacement speeds. However the key to Catamaran design is you need a higher Cp if you want to sail fast. So a multihull should be at least 0.61 and a heavy displacement multihull a bit higher still.

  2. Unlocking Catamaran Hull Design: Efficiency, Stability & Innovation

    The asymmetrical catamaran hull design offers enhanced stability, greater maneuverability, and increased speed on the water. Unlike traditional displacement hulls, which tend to plow through the water, catamarans slice through waves with minimal resistance, providing a smooth and efficient ride. ... Efficient Displacement Hull Design: Efficient ...

  3. Optimising Hull Lines for Performance

    A third number that we can plug in as a constant if we want to is the prismatic coefficient which describes bow much volume there is end the ends relative to the cross section shape in the middle of the boat, but in sailing boats this is of less importance compared to other factors. The hull lines for Design 256, 8.5m Cat.

  4. Power Catamarans: A Complete Guide

    However, the power catamaran is a relatively modern innovation that marries the traditional twin-hull design with powerful engines, offering a unique blend of speed, stability, and space. Distinguishing Design: Power Catamarans are characterized by their twin hulls, which significantly reduce the drag, thus enhancing speed and fuel efficiency.

  5. PDF Hull Shapes & Performance (Power)

    Schionning Designs use three hull types for our range of power catamarans, each with different design and performance characteristics. The hull shapes are: Prowler Semi-displacement. Prowler VT (Vapour Trail) Growler Whisper. The semi-displacement hull is a slim hull shape with a canoe-end underwater aft, meaning this hull simply slides through ...

  6. PDF Optimization of the Propulsive Efficiency of a Fast Catamaran

    To enable high speeds for any type of vessel (and even more of catamarans) operating around and beyond a Froude number of 0.50, it is essential to conduct a hydrodynamic optimization of the ship's hull form and its propulsive devices for the least power and of the overall design for the least structural and lightship weight.

  7. The Patented Power Proa Hull Design

    Catamarans offer a stable ride with predictable hull movement. The seakeeping is excellent, even in rough conditions. Another advantage the design provides: incredible onboard space. The space of a catamaran is often comparable to that of a monohull that is 25 percent longer. Catamarans also have been proven to provide efficient operation.

  8. Parts of Catamaran: A Comprehensive Guide to Understanding the

    1. Hull Design: Stability Meets Speed At the heart of every catamaran lies its dual-hull structure. Unlike traditional monohulls, catamarans feature two separate hulls connected by a spacious deck. This design offers enhanced stability and reduced heeling, making them less prone to capsizing compared to their single-hulled counterparts.

  9. Catamaran Hulls- Everything You Need To Know

    Although the catamaran hull concept is a relatively new introduction to modern boat design, the boat has been in use since the 5th century. It was used for fishing, traveling, and transporting people and supplies. ... Efficiency. Catamaran hulls allow the boat to cut through the waves easier and faster. It means they require less engine power ...

  10. A Guide to Catamarans: Exploring the Beauty of Twin-Hull Vessels

    3. Speed and Fuel Efficiency: The dual-hull design creates less drag, allowing catamarans to achieve impressive speeds and superior fuel economy. The reduced water displacement means they can be faster and more fuel efficient than monohull vessels of the same size.

  11. Sailing Catamarans

    Strike 15 trimaran at speed. 28ft Skoota in British Columbia. 10ft 2 sheet ply Duo dinghy. 24ft Strider sailing fast. 36ft Mirage open deck catamaran. Hull Resistance and Hull Shape Comparisons. Introduction. As I've said elsewhere, I only like to design boats that are fun to sail.

  12. PDF DISPLACEMENT POWER CATAMARANS

    The mainstream design office catamarans that I see look that way because those gold plate offices are most ... planing speed, they are more efficient than single hull boats, but much less efficient than displacement cata-marans. They will require some 1500 hp to do 30 knots, depending on weight. PLANING SINGLE HULL

  13. Catamaran Design Guide

    Catamarans are multihull boats with two parallel hulls, which are connected by a deck or a structure. They offer stability, speed, and efficiency in the water. A 16-passenger catamaran can vary in size and design, but generally, it will have enough seating or lounge areas for all passengers.

  14. What's the best shape for a fast & efficient catamaran hull?

    Doing research on fast & efficient hull shapes for a 25' cruising catamaran capable of 22/25 knots cruise and 30 knots top speed, while still providing reasonable performance at lower speeds, I found the following: 1) Efficient planning shape, foil assisted:Corsair 22 Foiler. The boat does 50 mph top with twin 90hp motors and cruises happily at ...

  15. DutchCat: The 15p-per-mile-marvel motor catamaran

    Crucial though hull design is, it's only one part of DutchCat's energy efficiency equation. Similar blue-sky thinking has been brought to bear on pushing that ultra efficient hull shape through the water. ... Combining the efficiency of a catamaran hull with the low-running costs of a diesel-electric hybrid makes perfect sense, particularly ...

  16. High-Efficiency Catamaran Design

    High-Efficiency Catamaran Design; High-Efficiency Catamaran Design. The Contributor. The National Research Council Canada (NRC) as represented by its Industrial Research Assistance Program (IRAP) funded the research in 2020 and 2021. ... The hull forms that were part of the design study had a considerable higher displacement than the validation ...

  17. Six Amazing Boat Hull Designs

    With only one set of running gear in the water, inherent appendage drag is reduced by 20 percent. Combined with the efficiency of the hull designs, overall fuel efficiency of the Aspen rises to an impressive 70 percent over monohulls of comparable size. Aspen won an award for the best 30- to 39-foot catamaran in the world in 2014.

  18. Boat Hull Shapes: What Hull Shape is Best?

    Catamarans As one of the oldest hull shapes (imagine two logs tied together), catamarans occupy a small niche in America and larger niches in some other areas of the world. Using two hulls bridged by a deck, the catamaran design provides additional beam, increased stability and, at the same time, increased speed (the slim twin hulls have little ...

  19. Rossinavi launches first 43m hybrid-electric catamaran Seawolf X

    A key characteristic of the model is her three "performance scenarios". On one-day trips, Seawolf X can cruise in full-electric mode for 100 per cent of the time; on multi-day trips, she can cruise for 90 per cent; and on transatlantic trips, she can still cruise in electric mode for 80 per cent of the time. When the catamaran is moored, a "hibernation mode" activates for reduced consumption ...

  20. Mytishchi

    Rapid trains (Sputniks) bound to Pushkino and Bolshevo also stop here. You can also get here pretty easily by taking the Kaluzhsko-Rizhskaya metro line to the end at Medvedkovo and there catch a bus or marshrutka to the Mytishchi center from the metro station. 55.91449 37.76223.

  21. Mytishchi Map

    Mytishchi is a mid-sized industrial city in North Moscow Oblast, which borders Moscow to the southwest. It is perhaps Moscow Oblast's principal industrial center, particularly for machinery and armaments. Map. Directions.

  22. Crocus Expo International Exhibition Centre

    Crocus Expo International Exhibition Centre, 16 Mezhdunarodnaya Ulitsa, Moscow Oblast 143401, Russia

  23. Design-Build Contractors & Firms in Mytishchi

    Search 827 Mytishchi design-build contractors & firms to find the best design-build contractor for your project. See the top reviewed local design-build contractors in Mytishchi, Moscow Oblast, Russia on Houzz.