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How To Build A Catamaran? (A Step-By-Step Guide)

Are you excited about the prospect of building your own catamaran? With a little research, planning, and the right tools, you can turn your vision into reality in no time.

In this step-by-step guide, well show you how to make the most of this incredible boatbuilding project.

From selecting the materials and planning the design to constructing the hulls and deck and outfitting the boat, well walk you through everything you need to know to build a catamaran of your own.

So, grab your tools and lets get started!

Table of Contents

Short Answer

Building a catamaran requires careful planning and a lot of patience.

The first step is to decide on the design and the materials you will use.

You will need plans for the project, along with lumber and other materials such as fiberglass and epoxy.

The next step is to build the catamaran frame, which involves cutting and fitting the wood pieces together to form the hulls and decks.

Finally, you will need to attach the decking, add the rig and sails, and finish the project with paint and varnish.

Benefits of Building a Catamaran

Building a catamaran can be a very rewarding experience.

Not only will you have the satisfaction of creating something with your own hands, but you will also have a boat that is uniquely yours.

Catamarans offer many benefits over traditional monohull boats, making them an ideal choice for those looking for a reliable and efficient ride.

These benefits include greater stability, more space, improved fuel efficiency, and greater speed.

Stability is one of the biggest advantages of catamarans.

The two hulls provide a wider base that helps to keep the boat from rocking and rolling in rough waters.

This makes for a much smoother and safer ride, even in choppy waters.

Additionally, the two hulls create an open area between them that is perfect for storing equipment, making it ideal for longer trips.

Catamarans are also more fuel efficient than monohulls.

This is because the two hulls provide lift, allowing the boat to glide through the water more easily.

This means you won’t need to use as much fuel to power your boat, allowing you to save money in the long run.

Finally, catamarans are faster than monohulls.

This is due to the increased surface area of the two hulls, which allows the boat to move more easily through the water.

This makes them ideal for those who want to travel quickly and efficiently.

Overall, building a catamaran can be a fun and rewarding experience.

With the right materials and tools, you can create a boat that is unique to you and offers many benefits over traditional monohull boats.

With the right planning and construction process, you can create a catamaran that will be the envy of your peers.

Selecting the Materials

Selecting the right materials is a crucial step in building a catamaran.

The type of material you choose will depend on the size and type of catamaran you are building, as well as your budget and experience.

Catamarans are typically constructed from wood, aluminum, or fiberglass.

Each of these materials has unique advantages, so it is important to research the pros and cons of each before making a decision.

Wood is the traditional material used to build catamarans and is often the most cost-effective option.

Wooden catamarans are strong and stable, and they can be custom-built to any size or shape.

However, wood requires a lot of maintenance and can be susceptible to rot and water damage.

Aluminum is a great option for larger catamarans, as it is lightweight and resistant to corrosion.

It is also relatively easy to work with and can be welded together to create a strong and durable structure.

However, aluminum is a more expensive material and is not as flexible as wood or fiberglass.

Fiberglass is the most popular material for building catamarans, as it is lightweight, strong, and resistant to corrosion.

Fiberglass is also relatively easy to work with and can be shaped to create unique designs.

However, fiberglass is also the most expensive option and can be difficult to repair if damaged.

Once you have selected the material, it is important to purchase the right amount for the project.

Make sure to measure the catamaran carefully and purchase enough material to account for any mistakes or waste.

It is also important to purchase high-quality materials that will last for years.

With the right materials, you can build an amazing catamaran that you will enjoy for years to come.

Planning the Design

When planning the design of your catamaran, youll need to consider a variety of factors, including the size, shape, and type of material youll be using.

Consider the size and weight of the catamaran and the type of water it will be used in.

Youll also need to think about how the catamaran will be used, such as for recreational or commercial purposes.

When it comes to the shape of the catamaran, the most common design is the two-hulled V-shape.

This shape is ideal as it offers stability and is easy to maneuver.

However, depending on the type of use, other shapes, such as the three-hulled catamaran, may be better suited.

The material you choose for your catamaran will also play a role in the design process.

Common materials used to build catamarans are wood, fiberglass, aluminum, and composites.

Each material has its own advantages and disadvantages, so its important to research and select the best material for your project.

Finally, when planning the design, youll need to consider the outfitting of the boat.

This includes items such as decking, seating, and a helm station.

Make sure to think about the type of equipment youll need for your catamaran, and consider how it will be installed.

By taking the time to plan the design of your catamaran, you can ensure that you get the best possible outcome.

Doing your research, selecting the right materials, and choosing the right outfitting will all help you create an amazing catamaran that will last for years to come.

Constructing the Hulls and Deck

Constructing the hulls and deck of a catamaran is perhaps the most important and time-consuming step in building a catamaran.

You will need to plan the design of the hulls and deck carefully to ensure that your catamaran is strong, stable, and seaworthy.

When constructing the hulls, you will need to use strong and light materials that are suitable for marine environments.

Fiberglass is a good choice for this, as it is strong and lightweight.

You will need to cut and shape the fiberglass to fit the shape of the hulls, and you will need to use a strong adhesive to bond the pieces together.

The deck of the catamaran will need to be strong and stable enough to support the weight of the passengers and cargo.

You will need to construct the deck out of marine-grade plywood, and you will need to use a strong adhesive to bond the pieces together.

You may also need to add extra support beams to the deck for added strength.

Once the hulls and deck have been constructed, you will need to sand and finish them to ensure a smooth and watertight surface.

You may need to use a sealer or primer to protect the wood and fiberglass from the elements.

Finally, you will need to attach the hulls and deck together.

This can be done with bolts, screws, or other fasteners.

You may also need to use a water-resistant sealant to ensure a watertight connection between the hulls and deck.

Outfitting the Boat

Outfitting a catamaran is an essential part of the build process.

Once the hulls and deck are constructed, you’ll need to ensure that all the necessary components are in place for a successful voyage.

This includes items such as masts, sails, rudders, and outriggers.

It is critical to ensure that the boat is outfitted with the right components for its size and purpose.

For example, if you are building a small catamaran for speed and agility, you’ll need to outfit it with a light and responsive mast and sail.

If you are building a larger craft for comfort and luxury, you’ll need to outfit it with a heavier and more resistant mast and sail.

Additionally, you’ll need to select the right outriggers and rudders for the catamaran’s size and purpose.

Outfitting a catamaran can be a complex process, and it is important to do the research and plan ahead.

Taking the time to select the right materials and components will ensure that your boat is outfitted for success.

Additionally, it is important to use quality materials and components to ensure a safe and successful voyage.

With careful planning and quality components, you can outfit your catamaran for a successful journey.

Acquiring the Right Tools

When it comes to building a catamaran, having the right tools can make all the difference.

To get started, you’ll need a variety of hand tools, including saws, drills, sanders, and screwdrivers.

You’ll also need power tools like routers, biscuit joiners, and angle grinders.

It’s also important to have safety equipment like safety glasses, ear protection, and respirators.

You’ll also need a variety of measuring tools, such as rulers, calipers, and tape measures.

Finally, you’ll need a selection of glues, adhesives, epoxies, and sealants.

With the right tools, you’ll be able to complete your catamaran project safely and efficiently.

Researching and Planning Your Build

Researching and planning your build are essential steps in the process of building a catamaran.

The first step is to become familiar with the design and construction of catamarans.

Start by researching different types of catamarans, from the small and lightweight recreational boats to the larger and more luxurious cruising vessels.

Learn about the advantages and disadvantages of the different types of catamarans and determine which type is best suited to your needs.

Once you have a good understanding of the different types of catamarans, you can begin researching the materials and tools you will need for your project.

You will need to choose the type of wood you will use for the boats hulls and deck, as well as the type of fiberglass and resin you will use for the hulls and deck.

You will also need to choose the type of engine you will use and the type of rigging and sail you will use.

Once you have selected the materials and tools you will need for your project, you will need to create a plan for the construction of your catamaran.

You will need to determine the size and shape of your boat, the types of joints you will use to construct the hulls and deck, and the type of engine and rigging you will need.

You should also plan out the sequence of construction steps, so that you can build the catamaran in the most efficient way.

Finally, you will need to research the best ways to protect your catamaran from the elements.

You will need to determine what type of paint or varnish to use on the hulls and deck, and you will need to research the most effective ways to protect your boat from the sun, wind, and water.

By taking the time to research and plan your build, you will be able to create a catamaran that is well-built, efficient, and beautiful.

With the right research and planning, you can create an amazing catamaran that will be the envy of your friends.

Final Thoughts

Building a catamaran is a rewarding experience that can be achieved with the right approach and materials.

With a clear plan, the right tools, and a good understanding of woodworking and fiberglass techniques, you can build an amazing catamaran to share with your family and friends.

So what are you waiting for? Get started on your own catamaran build today and all the rewards that come with it!

James Frami

At the age of 15, he and four other friends from his neighborhood constructed their first boat. He has been sailing for almost 30 years and has a wealth of knowledge that he wants to share with others.

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How To Create the Perfect Cruising Catamaran Layout

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More than ever before, sailing fans are gaining an interest in catamaran layouts and designs that define performance. Many others are also looking into either buying a cruising catamaran or designing and building one. While building a catamaran is no piece of cake, this article shows you how to create the perfect cruising catamaran layout. 

To create the perfect catamaran layout, carefully consider factors like a good hull design, optimal helm station placement, boat stability, and adequate load-carrying capacity. Excellent galley positioning, ease of handling, and spacious living and sleeping quarters are also crucial. 

The modern cruising catamaran is a far cry from the simple Polynesian double canoe of old. That’s because structural innovations and new composite materials have resulted in multihulls with impressive cruising abilities. Keep reading to learn more about exceptional catamaran layouts.  

The Changing Trends in Catamaran Designs

The early cruising catamaran designs resulted in boats that could sail much faster than traditional sailing boats. In addition, they could glide with ease in shallow waters and required less wind and crew. Unfortunately, these cruising cats were heavy, had small, cramped interiors, and boasted somewhat challenging handling abilities. 

Today’s cruising catamarans are different. They boast the utmost comfort, high speeds, and the safety of a well-designed cruising yacht. They are also more exciting, visually appealing, deliver the smoothest of rides, and sport more spacious interiors. 

Have a look at the below video showcasing the top ten cruising catamarans:

Features To Look Out for in Catamaran Design Layouts

Cruising catamaran designers understand what most sailors look for in a cruising vessel. They, therefore, design cruising multihulls that address these pertinent issues and more. Some of the features you might want to consider having in your dream boat include the following:

• Responsive performance. Outstanding performance allows for pleasurable cruising and ensures your safety since you have more options during difficult weather.
• Excellent load-carrying ability . This allows you to have an extended cruising vacation or ocean crossing.
• Boat stability . Go for lightweight, robust construction, which results in a lot of buoyancy.
• A low center of gravity for smooth rides and enhanced performance. Centering weight around a low center of gravity improves the overall sailing quality, reduces pitching movement and reduces the risk of capsizing .
• Adequate bridgedeck clearance to reduce slamming and provide better performance in rough conditions. A high bridgedeck also means less noise and slapping action from the waves hitting the boat bottom, thus ensuring a quieter, smoother ride.
• Comfortable sailing. To enjoy a quality life on board, you need comfort while at sea. Thus, elements like gentle movement, no creaks or groans, no bridgedeck slamming, and minimal pitching are essential for quality, peaceful and restful sleep.  

Now that you know what a cutting-edge catamaran features, let’s look at how to create the perfect cruising catamaran layout.  

Build a Larger-Sized Catamaran

The early catamarans ranged between 36-42 feet (10.9-12.8m). At the time, this appeared to be a good size in terms of safety and ease of handling. However, the boats were heavy, and the additional drag and displacement adversely affected their performance and windward ability. 

It’s now possible to make the new generation catamarans lighter, larger, and more spacious with excellent power-to-weight features. The current trend is larger-sized catamarans in the 45-50 feet (13.7- 15.2) range. Composite engineering and technologically advanced equipment such as furling systems, electric winches, and autopilot make it easier for a smaller crew to sail larger boats with confidence. And to do so without compromising safety or stability. 

Get the Best Catamaran Hull Design

A cruising catamaran’s performance depends on three main aspects; its length, the sail area, and the boat’s weight. Long boats are generally fast. A light boat with more sail area is also faster than a heavier boat with less sail area. In other words, you can make a multihull faster by making it longer, lighter, or adding more sail.

However, there are exceptions to this rule; a boat with too much sail area is more likely to capsize if there are brisk winds. Also, if the boat’s design makes it too light, it’ll be unable to handle much punishment, while a hull design that’s too slim would make the vessel incapable of carrying any significant loads. But that’s not all; if the boat is too long or too large, it’ll become grossly exorbitant. Narrow hull shape might also mean smaller cabins.

Nonetheless, these three factors alone are not enough to determine a cruising catamaran’s performance. While faster boats boast finer hulls, the wetted surface area tends to increase as fineness increases; thus, fine hulls end up becoming less fast in low wind speeds. Also, very wide hulls mean a reduction in actual performance.

The Prismatic Coefficient (Cp), a measure of how full the ends of the hull get, is the most essential design hull shape factor for any catamaran. A high Cp equals high speeds, although you can still use a lower Cp if you have fine hulls. Nevertheless, the key to a good Catamaran design is a higher Cp for fast sailing. 

To achieve a high Cp, there are several things you can do: 

• Fit bulb bows . Unfortunately, the bulb bows tend to slam in a seaway when you do this.
• Have an extensive planning aft section . However, this can increase the wetted surface area, WSA and lead to additional challenges. 
• Flatten out the hull rocker and add a bustle aft. This helps to add displacement aft. 

Build Convertible Main Living Spaces

The open cockpit is now a thing of the past. Instead, pioneering designers for catamaran manufacturers like Nautitech, Gunboat, and Catana now replace traditional-style salons, cockpits, and cabins with spacious indoor and outdoor living spaces. The concept involves merging separate saloon and cockpit areas with duplicate lounge spaces and the use of hard-wearing composite materials. 

You can also design the cabin to suit your preferences. You may decide to add a cabin or remove one, add a bathroom, have the forward berth in the hull or on the wing deck.

• The design enhancements boost usable space while opening up the living areas.
• It reduces time and costs for interior maintenance and cleaning. 
• Large windows bring in more light, increasing visibility. 
• Luxurious, spacious, and airy owners’ cabins provide more comfortable living space. 

Bulkhead Helm Stations vs. Twin Stern Steering

Many catamaran owners have traditionally preferred bulkhead steering. This helm position remains popular, but twin stern steering positions come with more advantages since they provide greater sails visibility. The twin stern positions are also best suited for racing or day sailing since they often lack adequate protection for extended cruising. 

Exposed helms are not ideal for a long ocean passage. Go for a safe, secure, and well-protected helm station that provides good visibility and comfortable space for long watches. Again, it’s best to have all control lines at the helm to establish a static control station. Also, have all push-button-controlled winches, instruments, windlass, and autopilot prominently located inside the cockpit. 

• Twin stern steering positions give you a better view of the sails
• You get a better feel for overall sailing conditions.
• Twin stern steering positions lack the necessary protection for extended cruising. 

Go for the Flybridge Design

The flybridge design is appealing because it offers excellent visibility, more comfort, and additional entertainment and lounging space for everyone on board. Unfortunately for smaller boats – those below 50 feet (15.24m), there is minimal protection from the elements. As such, you might want to consider adding enclosures to offer protection. The flybridge, thus the helm, remains cut off from the vessel, which makes communicating with the crew a challenge. 

• It provides great visibility.
• It offers comfortable spacing. 
• It might be unsafe to move from the cockpit to the flybridge in bad weather.
• It isn’t easy to communicate with the crew.

Daggerboards vs. Fixed Keels

Average cruising catamarans typically utilize fixed keels while high-performance cats have daggerboards . Fixed keels allow you to beach your catamaran easily, and your hull remains intact if a collision occurs. While you lose some angle when sailing upwind, you gain more interior space in the hulls that you can put to good use.

Daggerboards are essential in a performance cruising catamaran since they guarantee that the boat delivers good upwind sailing, including during difficult situations. During long passages, they allow you to point better upwind though the drawback is that they consume much interior space within the cruising catamaran’s hulls.

Since flying on foils ( hydrofoils ) isn’t that practical on cruising catamarans, designers of larger-sized boats have also come up with modified daggerboards. These daggerboards produce lift and prevent leeway, too, thereby improving performance significantly, as seen with the Catana 59’s curved daggerboards. These foil-like daggerboards lift the boat ever so slightly upon reaching higher speeds, making it feel less heavy and much faster. 

At the end of the day, calculating the performance of a boat sailing in a wide range of varying seas and winds might not be easy – despite a daggerboard or fixed keel configuration. This is because upwind speed depends not only on the sails’ quality but also windage and the height of the bridgedeck beyond the water.

• The design innovations -curved daggerboards and hydrofoils- improve catamaran performance significantly.
• Daggerboards enable you to access otherwise inaccessible anchorages.
• Daggerboards take up hull space in the hulls of your vessel.

Galley Up vs. Galley Down

Galley layout are becoming more and more important as more people, including families, start sailing regularly. While at sea, your galley needs to be a safe place, well-ventilated, and functional. Everything should be well-thought-out for the sailor’s comfort, including handholds to make it safer to move around the boat. 

While the galley location can either be up the bridgedeck or down in the hull, galley up appears to be the most popular trend. This makes the galley the focal point of both the living space and entertainment areas.

If you have a family, this placement is ideal since you make your meals from the galley and get to spend most of your time here. Many cruising families and couples prefer this arrangement and find separating the galley down the hull unappealing. Besides, carrying hot food up and down the staircase is unsafe.

Still, galley down is ideal for charter boats since it offers a private cooking area and uses up hull space efficiently.  

• Having the galley on the bridgedeck is ideal for families and cruising couples.
• Placing the galley on a similar level with the serving area and cockpit is safer and less tiring.
• There’s better ventilation on the bridgedeck, making for comfortable cooking. 
• There’s less kitchen privacy galley up.
• On smaller catamarans, this layout can impact the size of the saloon seating area significantly.

Production Catamaran vs. Custom

The choice of either a production catamaran or a custom design might seem pretty straightforward. Production catamarans from major brands come backed by proven designs, dependable construction, solid warranties, and many years of experience. The catamarans are easy to service, source for parts, and most – particularly the owner’s versions – hold on to their value, making them much easier to resell. 

On their part, custom boats are fantastic in that you can tailor them to your exact needs. However, they might be more challenging to maintain or service. That’s because of parts unavailability and lack of construction knowledge.

Choose Quality Construction Materials

The best quality materials to use on your catamaran are both light and robust. While carbon fiber is great, plywood, plywood/epoxy, and strip-cedar are excellent materials too. What’s more, they are also affordable, so you don’t have to get too hung up on cutting-edge building materials. What matters is build quality; thus, a well-built plywood catamaran boat can last as long as a boat made from more high-tech materials. 

Combining various materials also helps combat some of the issues that plague plywood boats in terms of resale value. At times, the design tends to make the boats appear pretty dated.  

• Plywood and strip-cedar materials are affordable and provide excellent build quality. 
• Plywood boats may have a lower resale value than those built with modern materials.

Consider Ease of Handling

An important factor in handling a cruising catamaran is deck layout. Most cruising catamarans sailed short-handed , so if your boat has one helm, all lines should run back here to allow for a static control station for the entire boat. 

The other essential element is visibility from the helm. The 360 degrees of visibility while maneuvering, docking, or underway is crucial to your boat’s safety, as well as life and property. As such, you should be able to view both bows, or at least the pulpits and sterns, while standing at the helm. If not, you may have challenges handling the boat due to blind spots.

Consider the Load Carrying Capacity

A well-designed catamaran is enjoyable to sail in all weather conditions. It’s also much easier to handle than a monohull because of its widely spaced twin engines. But when you immerse extra hull depth, the vessel gets sluggish and moves slower, maneuvering in tight spots or when docking becomes more challenging. Furthermore, the hull submersion reduces bridge deck clearance, leading to hull slamming. 

To allow for adequate load carrying capacity, you need a design that provides a generous displacement. This helps to ensure that you maintain reasonable bridge deck clearance even when fully loaded. It also allows you to avoid digging big holes in the water as you drag your transoms. 

Displacement refers to the amount of buoyancy designed into the hulls, which essentially means that your boat will cruise better if its weight is less than your designed displacement.

Note that an overloaded catamaran not only loses out on performance but eventually, on safety too. To counter this, choose a lightweight catamaran with hulls bearing cored construction and interiors made of lightweight materials.  

Remember, when you go cruising, you will need to carry fuel, extra water, supplies, equipment, and amenities, translating into thousands of extra pounds. Therefore, try and avoid the following design errors to ensure that your catamaran has an adequate load-carrying capacity:

• Avoid putting in place too much accommodation space.
• Avoid building a heavy boat ‐ use low-tech construction materials.
• Avoid installing inboards in a small boat.
• Lightly constructed catamarans perform faster and carry more weight.
• Cored construction makes for a strong and stiff catamaran, thus enabling good performance.

Final Thoughts

A well-designed cruising catamaran is a joy to behold. Today’s modern technological advancements mean that you can buy or build a light but strong cruising catamaran. And as you can see from this article, there are many excellent cruising catamaran layouts that you can choose from. 

However, whichever layout you decide on needs to fit your sailing needs and purposes to ensure you remain comfortable and safe while at sea. Above all, ensure that you go for a vessel that you can handle with ease in all weather conditions.

Owner of CatamaranFreedom.com. A minimalist that has lived in a caravan in Sweden, 35ft Monohull in the Bahamas, and right now in his self-built Van. He just started the next adventure, to circumnavigate the world on a Catamaran!

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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.

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

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

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.

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

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'.

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.

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.

"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

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.

Continue reading here: Hull

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Related Posts

• Design Dynamics - Catamarans Guide
• Hull Construction - Ship Design
• Geometry - Ship Design
• Heavy Weather Tactics - Catamarans Guide
• Configuration Types - Catamarans Guide

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.

Catamaran Plans: Design, Build and Sail your own Multi-Hull Boat

Table of Contents

Why Build a Catamaran: The Benefits of Multi-Hull Boats

Building a catamaran offers many benefits over traditional monohull boats. One of the main advantages of catamarans is their stability. With two hulls instead of one, catamarans have a lower center of gravity, which makes them less likely to tip over in rough waters. This makes them ideal for families with children, or for anyone who wants to feel more secure while on the water.

Another benefit of catamarans is their increased speed and efficiency. The two hulls of a catamaran can displace more water than a single hull, which means they can move through the water faster and with less resistance. This makes them ideal for racing or for anyone who wants to cover more ground in less time. Additionally, Catamarans are also known for their space, as the twin-hull design provides more room for living and storage than a monohull.

Catamarans also offer more flexibility in terms of design. The two hulls of a catamaran can be configured in many different ways, which allows for a wide range of customization options. For example, one hull can be used for sleeping quarters, while the other can be used for storage or as a cockpit. This makes catamarans ideal for long-term cruising or for anyone who wants to create a unique and personalized boat.

Finally, catamarans are also more environmentally friendly than monohulls. Because they are more efficient, they can move through the water with less fuel consumption, which reduces their carbon footprint. Additionally, many catamaran designs incorporate solar panels and other renewable energy sources, which makes them ideal for anyone who wants to minimize their environmental impact while enjoying the water.

Designing Your Own Catamaran: Tips and Tricks

Designing your own catamaran can be a challenging but rewarding experience. Before you begin, it’s important to consider your needs and goals for the boat. Are you planning to use it for racing, cruising, or a combination of both? How many people will be on board? What kind of conditions will you be sailing in? Answering these questions will help you to determine the size, shape, and features of your catamaran.

One important tip when designing your catamaran is to keep it simple. While it can be tempting to add a lot of bells and whistles, the more complex your design, the more difficult and expensive it will be to build and maintain. Instead, focus on creating a functional and efficient boat that meets your needs.

Another tip is to take into account the materials you will be using. Different materials have different properties and costs, so it’s important to choose the right ones for your design. For example, wood is a traditional and affordable material, but it requires more maintenance than fiberglass. On the other hand, composites materials are more expensive but offer great weight to strength ratio.

Finally, it’s important to consult with experts and professionals during the design process. There are many resources available, such as online forums, books, and classes, that can help you to learn more about catamaran design and construction. Additionally, you should consider consulting with naval architects, boat builders, and other experts who can offer guidance and feedback on your design. They can help you to refine your ideas and ensure that your boat is safe and seaworthy.

Materials and Tools Needed for Building a Catamaran

Building a catamaran requires a variety of materials and tools. The materials you will need will depend on the design of your catamaran and the type of construction you choose. Common materials used in catamaran construction include wood, fiberglass, composites, aluminum, and PVC. Each material has its own unique properties and benefits, so it’s important to choose the right one for your project.

When it comes to tools, you will need a basic set of hand and power tools to complete your catamaran project. These include saws, drills, sanders, and other tools that are commonly used in woodworking or metalworking. Additionally, you will need specialized tools such as a router, a band saw, and a vacuum bagging system if you are building with composites materials.

In addition to the above tools, you will also need safety gear, such as goggles, respirators, and ear protection. Building a catamaran can be a challenging and time-consuming process, so it’s important to take the necessary precautions to protect yourself and others. Additionally, it’s important to have a well-ventilated workspace, as some of the materials and chemicals used in catamaran construction can be harmful if inhaled.

Common Mistakes to Avoid When Building a Catamaran

Building a catamaran can be a complex and challenging process, and it’s easy to make mistakes if you’re not careful. Here are some common mistakes to avoid when building a catamaran:

One of the most common mistakes is not properly planning and designing your catamaran. This can lead to problems later on in the construction process, such as not having enough room for your intended use or not being able to fit certain components. It is important to take the time to carefully plan and design your catamaran, taking into account your needs, goals and the materials you will be using.

Another common mistake is not properly preparing your materials. This can include not properly storing or protecting the materials from the elements, or not properly cutting or shaping the materials before assembly. Proper preparation of materials is essential to ensure that your catamaran is strong and durable.

A third mistake is not using the right tools or not using them properly. This can lead to problems such as not being able to cut or shape the materials correctly, or not being able to assemble the boat properly. It’s important to research and invest in the right tools for the job, and to learn how to use them properly before starting the construction process.

Another common mistake is not properly securing and aligning the components during assembly. This can lead to problems such as leaks, or the boat being unstable on the water. It’s important to take your time and to work carefully to ensure that everything is properly aligned and secured.

Finally, not following safety guidelines is a mistake that should be avoided. This can include not wearing protective gear, not having proper ventilation, or not taking the necessary precautions to protect yourself and others. Building a catamaran can be a challenging process, but it’s important to prioritize safety to prevent accidents or injuries.

After completing the construction of your catamaran, there are several important steps to take before launching it. These include finishing the exterior and interior of the boat, and performing necessary safety checks.

Finishing and Launching Your Catamaran

Finishing the exterior of your catamaran involves tasks such as painting, varnishing, or applying gel coat. This step is important to protect the boat from the elements and give it a professional look. It’s important to use the right type of paint or finish for the materials you used in the construction, and to follow the manufacturer’s instructions.

Similarly, finishing the interior of your catamaran involves tasks such as installing cabinetry, flooring, and other finishing touches. This step is important to make the boat more comfortable and functional. You can add amenities such as a kitchen, a bathroom, and a sleeping area.

After the finishing is done, it’s important to perform safety checks on your catamaran before launching. This includes checking the boat’s systems such as electrical, plumbing, and navigation. You should also check that all the safety equipment is in place and working properly. This includes life jackets, flares, and fire extinguishers.

Once all the necessary steps are completed, you will be ready to launch your catamaran. Launching a catamaran is a complex process that requires coordination between the boat owner, the marina, and other professionals. The boat should be launched in a protected area with calm waters, and with the help of a crane or a trailer. It’s important to have a plan in place for launching and to be aware of the local laws and regulations.

Finally, after the catamaran is launched, it’s important to test the boat and make any necessary adjustments before taking it out on the water. This includes testing the systems, checking for leaks and making sure that the boat is stable on the water. After this, you can finally enjoy your new catamaran!

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Go on adventures and live the life of your dreams. Spend your weekends coastal trekking and camping, or live aboard and spend your days sailing around the world. Become a member of the global family of Wharram builders and sailors. Wharram catamarans have been built and are sailing in all the World's oceans and can be found in far away ports and anchorages.

The quality of the Wharram self-build catamarans is reflected in their popularity, excellence of craftmanship and sound sailing qualities. More than 50 years on - with over 10,000 sets of plans sold and thousands turned into proud vessels - Wharram 'Cats' can be seen in harbours across the world, maintaining the highest reputation for surviving wind and wave.

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James Wharram: Lifetime Achievement Award

A special award was presented to James Wharram for a 'Lifetime Achievement' as Pioneer catamaran builder - sailor and multihull designer.

About James Wharram

In the mid 50's, based on his research into ancient Polynesian boat design, James Wharram built the first off-shore Catamaran in Britain and sailed it out into the Atlantic. While the world's yachting community still did not accept such a design as a worthy sea-going vessel, James was landing his 23'6" 'Double Canoe' called TANGAROA in Trinidad in the West Indies.

There he built a second 40' Polynesian style Catamaran, RONGO, and in 1959 sailed it up to New York and back to the UK accompanied by two German women - being the first to sail a catamaran West-to-East across the North Atlantic. These amazing Trans-Atlantic crossings and the follow up book ' Two Girls, Two Catamarans ' have etched the name 'James Wharram' into the annals of yachting history.

Since then, James Wharram has been designing, building and sailing offshore catamarans longer than any other multihull designer. James was a 'hands-on' designer having, over his lifetime, built personally many of the prototype designs. These prototypes were built in the open, in barns, workshops and all the range of building sites available to self-builders, in a variety of climate types from northern European to the Tropics. James was often referred to as a 'Living Legend' or as written in 'Yachting Monthly' in January 2006: "James Wharram is considered by many to be the father of modern multihull cruising."

James’ last achievement was his autobiography published in 2020 as ' People of the Sea ', which he wrote in conjunction with his design/life partner Hanneke Boon. James died in December 2021 at the age of 93. The design business is carried on by his co-designer Hanneke Boon .

Hui Wharram Cornwall Gathering 2024

We are having another Annual Hui! This Hui will mark 70 years since James designed his first Catamaran 'Tangaroa' and we are excited that we will be mooring at Devoran Quay just a 5 minute walk from the Wharram Headquarters based in Cornwall. It would be lovely to celebrate his achievement with all of you.

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Pacific Islander History Month

This month of May in America is 'Pacific Islander History Month' and we at James Wharram Designs would like to join in and celebrate alongside them! As you may know, double canoes/catamarans are of ancient Polynesian origin. The modern day catamaran is a direct descendent of these original ocean-going vessels.

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James Wharram's Last Ride

On 23 July, a motley fleet of self-built catamarans gathered off Cornwall to give James and Ruth Wharram their final escort. It was a fitting farewell to a legend. The ashes of James and Ruth Wharram were consigned to the sea to be carried by the ebb current out to the open ocean.

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James' Eulogy

Hi everyone. I'm Matt. And apart from being truly honoured to be here to help send James on his way to his next adventure, I am here above all as a representative, really, for the many many people worldwide who's lives have been changed, for the better, as a result of James' life work.

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A Living Legend Lives No More

We are very sad to announce that on the 14th December James Wharram left this earthly world, joining Ruth, Jutta and his many close friends that departed before him. At 93 years old his spirit has set out on the voyage to sail the oceans of heaven.

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People Of The Sea - Compact Edition

The new second edition of the autobiography of James Wharram and Hanneke Boon is now available! This more compact edition at the lower cost of £16 contains all the text and illustrations of the special first edition. An easier size to fit the bookshelf on your boat. A must for all Wharram enthusiasts and other sailors.

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CUSTOM POWER CATAMARAN Yacht Layout & GA Plans

36m  /  118'1 | custom | 2000 / 2011.

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Plans de multicoques pour constructeur amateur

Jérôme Delaunay Architecte Naval - Nautline bureau d'étude en architecture naval : je conçois et dessine des plans de bateaux et voiliers sur mesure, en contreplaqué époxy et autres matériaux. Plans de voiliers pour la construction armateur et la construction professionnelle. Plans de multicoques, plans de catamarans, praos et trimarans. Étude de carène en CFD, bassin de carène numérique, optimisation de la motorisation . Je propose des calculs de structures, calculs de quilles, calculs de mâts et gréements. Calculs des échantillonnages en composites. Plans numériques DXF pour découpe numérique CNC.

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Open Source 13-15m Catamaran Plans

Discussion in ' Projects & Proposals ' started by archie1492 , Jan 3, 2018 .

archie1492 Junior Member

Dear all, I want to create a detailed building information model for a 13 - 15 meter catamaran that is capable of being CNC cut and assembled. I need some help finding plans I can use as a basis of design. Specifically, I need the hull profile information. Section cuts through the hull will give me the ideal contours for a boat of this size. Can someone help? After weeks of searching, I still cannot find these online. For now, this is merely an exercise in my 3d modeling capability. I'd like to share my drawing work with the forum if I can get some assistance to start off. There are future possibilities I am also considering. I'm an experienced Architect & construction designer with a strong background in computer aided design. Once I've modeled the boat in 3d, I would like to flatten the various parts and create plans for the individual boat parts to be CNC cut. I would like to build a small scale model first (1:2o or perhaps 1:10) with the ultimate goal of building the boat full scale.  

TANSL Senior Member

This is a very simple catamaran which, if you are interested, I can give you a lot of information. It is not a spectacular boat but it can help you in your first steps with boats. LOA = 16 m, Lbp = 14.6 m  

Thanks I really appreciate it. The hull lines for the motor cat you've provided are not quite what i'm looking for. I'm specifically looking for the hull lines for a 14m catamaran sail boat. I guess there is some standard for these contours especially the area below the waterline. Check the attached document as well if anyone is interested in this.  

Attached Files:

catdimension.pdf

I'm sorry, you never specified that it was a sailing catamaran. I thought that to carry out your purposes, " For now, this is merely an exercise in my 3d modeling capability ", any model was valid. Apparently, you have different purposes than, in addition to, to practice with 3D models. The better you clarify what you are really looking for, the better someone can help you.  

Hi all, Here's an example of what kind of information I need to get started. Optimising Hull Lines for Performance https://www.graingerdesigns.net/the-lab/optimising-hull-lines-for-performance/ The boat shown here is a 8.5m cat sailboat. I'm looking for something a bit larger in the 14m range. Also, the images only show one of the hull profiles. I'd like profile lines for the entire boat. I will post some other images I've found online showing profile lines for smaller boats. I still cannot find any 14m hull lines. Can anyone help?  

grainger_1488019480.jpg

Grainger_1488019410.jpg, grainger_1488019333.jpg, grainger_1488019265.jpg, grainger_1488019219.jpg.

Here are some other hull lines I've found online. Hope this is useful to anyone else looking for this information. Thanks!  

Evergreen Lines small.jpg

Hull-lines.jpg, shark-20.jpg.

You could take any of those boats and scaleb the lines to get the desired length. Since it is only a 3D modeling exercise, you do not have to worry about anything else. You could even make a mix of 2 or 3 of those models to get the one you are looking for.  

Thanks Tansl, I'd like to make the boat drawings accurate for the 14m size. Perhaps one day I will develop this into something worth building full scale. The more accurate I can draw the boat, the more I will learn about the boat design.  

Maybe it does not look like it but I would like to help you. If you do not find what you want on the Internet I could draw a lines plan, strictly following your instructions, which would help you to make the 3D model. Or, if you find something similar on the internet I can adapt it to your needs and fill in the information that you indicate you need for your work. I insist that starting from the shapes of a 10 m boat you can get the shapes of a boat of 14 m, with total accuracy.  

Dolfiman Senior Member

archie1492 said: ↑ I'd like to make the boat drawings accurate for the 14m size. Perhaps one day I will develop this into something worth building full scale. The more accurate I can draw the boat, the more I will learn about the boat design. Click to expand...

Cata 14m with Gene-Hull UE Catamaran 2.3_2018 01 15.ods

Gene-Hull Catamaran 2.3 User Guide_2018 01 16.pdf

Hull for cata 14m with Gene-Hull UE Catamaran 2.3_2018 01 16.pdf

Dolfiman, thanks so much! This is exactly what I was looking for. It's very interesting and probably a bit over my head at this point. I think this should work for modeling the basic hull shape. For the bridge deck and all of the stuff above the hull I can model this with a bit more creativity. Although, I'd like to learn more about understanding the center of gravity for the boat and the proper location of the mast. Are there any rules of thumb about this? Thanks again!  

archie1492 said: ↑ I think this should work for modeling the basic hull shape. Click to expand...

Cata 14m V2 with Gene-Hull UE Catamaran 2.3_2018 01 15.ods

In complement to illustrate this first approach, my good friend Alain did some 3D views here attached of the hull V2 version with Multisurf (using fit for purpose ouput data in section 5. of the above file). To inspire you , some other examples of cata, more sport/day sailer oriented than the Saona 47 : - R/P 45 (Reichel-Pugh) : multihull http://reichel-pugh.com/tag/multihull/ - Dazcat 1295 : in this video, from 1:45 the launch, you can see the hulls from various angles https://www.youtube.com/watch?v=0BZF4Udda5E - SIG 45 (VPLP design) : from 1:20 you can see the winward hull fully lifted ​  

dean 1962 New Member

archie1492 said: ↑ Dear all, I want to create a detailed building information model for a 13 - 15 meter catamaran that is capable of being CNC cut and assembled. I need some help finding plans I can use as a basis of design. Specifically, I need the hull profile information. Section cuts through the hull will give me the ideal contours for a boat of this size. Can someone help? After weeks of searching, I still cannot find these online. For now, this is merely an exercise in my 3d modeling capability. I'd like to share my drawing work with the forum if I can get some assistance to start off. There are future possibilities I am also considering. I'm an experienced Architect & construction designer with a strong background in computer aided design. Once I've modeled the boat in 3d, I would like to flatten the various parts and create plans for the individual boat parts to be CNC cut. I would like to build a small scale model first (1:2o or perhaps 1:10) with the ultimate goal of building the boat full scale. Click to expand...

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Archie, I have been looking to do the same thing. Where are you at on the project? Very interested in hearing all about it. Thanks.  

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EcoCat 42, un catamaran de croisière à fabriquer soi-même pour rester écoresponsable

Concevoir et surtout construire un catamaran vraiment écoresponsable. Voilà l'objectif que propose de réaliser l'architecte Alexandre Fortabat avec l'EcoCat 42, un catamaran qui ne devrait que très peu marquer par son empreinte écologique.

Alexandre Fortabat est architecte naval. Ses différents chantiers lui ont donné envie de "construire propre". Pas seulement proposer du Green Wahsing, mais bien d'avancer une solution de construction la plus écoresponsable possible. Il propose donc l'EcoCat, un catamaran de 42 pieds (12,80 m) dont toutes les phases de vie du produit sont réfléchies dans ce sens. Depuis la construction, l'utilisation jusqu'à la déconstruction.

Une construction par panneau

Construire un moule puis venir infuser des pièces dedans, demande beaucoup de matériaux non recyclables : le moule, mais aussi les bâches en plastique utilisées pour l'infusion sont autant de produits que l'on jette ensuite. Alexandre Fortabat propose un catamaran avec des formes développables, construit à partir de panneaux plats. Ainsi ce bateau pourra être proposé en contreplaqué ou bien avec des panneaux en sandwich réalisés sur des marbres. Ainsi le marbre tout comme le silicone qui renferme le sandwich sont réutilisables.

Ce sandwich est composé d'une âme en balsa (matériaux recyclables) et de peaux en fibre de lin avec de la résine époxy biosourcée. La construction est alors la plus propre possible. Seul défaut de ce principe : la perte suite aux découpes des différentes pièces dans les panneaux. Bien qu'elle soit minimisée par des logiciels de placement.

L'architecte pense aussi à la fourniture des matériaux puisque l'ensemble des composants comme le contreplaqué ou même la découpe numérique peuvent se sourcer à proximité du chantier, limitant l'impact sur le transport .

Une construction amateur

Pour diminuer les couts, l'EcoCat sera proposé à différents stades de finition. Depuis la fourniture des plans et des fichiers de découpe numérique, jusqu'à la livraison de la plateforme assemblée à finir. La volonté de l'architecte est de proposer un catamaran de 42 pieds à moins de 500 000 €. Il estime d'ailleurs le prix d'un bateau réalisé par un amateur entre 300 et 350 000 € prêt à partir en grande croisière. Pour cette construction, le temps de travail uniquement pour la plateforme est estimé à environ 3500 h pour un amateur éclairé.

Tout le bateau a été conçu pour cette construction en kit avec des assemblages prévus en découpe numériques sur les différentes pièces et des liaisons, non pas avec des joints congés, mais avec des reprises de strat en fibre de lin .

Dessiné pour la grande croisière

Ce catamaran de 42 pieds qui ne pèsera que 10 t chargé au maximum est destiné à une famille voulant partir en grand voyage. C'est un véritable Open avec une nacelle ouverte, juste fermée par des panneaux souples amovibles. De chaque côté, plus bas de quelques marches, se trouvent deux espaces de vie, cuisine à bâbord et table à cartes à tribord. Sous ces planchers sont installées les zones techniques. Avec un plan prévu dès l'origine pour une motorisation électrique Oceanvolt (à partir de 2 x 10 kW), le parc batterie se retrouve bien centré pour la répartition des masses. À l'avant et à l'arrière de chaque coque s'installent des cabines doubles et des cabinets de toilette.

Plusieurs prospects ont déjà montré leur intérêt pour ce type de bateau et l'on espère bientôt voir démarrer des constructions. Alexandre Fortabat ayant déjà imaginé une gamme de 3 modèles sur le même concept : 27, 35 et le 42 pieds présenté ici.

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Construire soi-même son catamaran : pourquoi pas vous ?

Article publié le 15/10/2014

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