# How to design a catamaran

Catamaran Hull Design

Below are basic equations and parameters of catamaran design, courtesy of Terho Halme. There are also a few references from ISO boat standards. The first step of catamaran design is to decide the length of the boat and her purpose. Then we’ll try to optimize other dimensions, to give her decent performance. Garett’s #1 axiom of catamaran boat building: Axiom #1: The hours to build a catamaran is in almost in direct proportion to its weight. Which brings us to Axiom #2: Axiom #2: It takes about 1 hour to create 1 pound of finished boat. In our case we spent 3, hours (click here for full details on the construction hours) to build a 4, lb. boat.

I found his paper easy to follow and all the Desibn hull design equations were in one place. Terho was kind enough to grant permission to reproduce his how to setup up a network here. Below are basic equations and parameters of catamaran design, courtesy of Terho Halme. There are also a few references from ISO boat standards. The first step catamarsn catamaran design is to decide the length of catamarxn boat and her purpose.

Please see our catamarans for sale by owner page if you are looking for great deals on affordable catamarans sold dexign by their owners. The following consist of arbitrary values to illustrate a calculated example.

Heavy boats have low value and light racers high value. Lower yo increase loading capacity. Normal L BR for a cruiser is somewhere between 9 and dezign L BR has a definitive effect on boat viking how to train your dragon estimate. Im working though these formuals to help in the conversion of a cat from diesel to electric.

Range, Speed, effect of extra weight on the boat…. First off what is it? The planned length will be about thirty six ft. In length. This will help me in this new venture. You ddesign to ask t author.

His link was above. What am I missing? On the right hand side the Tc on the top is divided by the Tc on the bottom so the equal 1 and can both be crossed out. Your email address will not be published. Save my name, email, and website in this browser for the next time I comment.

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Catamaran Selling Advice. Catamaran Sales Forms. Catamaran Importation. List Your Catamaran For Sale on catamaransite. Reasonable values are from 1. Higher values increase load capacity.

The deep-V bottomed boats have typically B TR between 1. B TR has also effect on boat displacement estimation. Bow coefficient has a linear relation to displacement. Prismatic coefficient has an influence on boat resistance.

C p is typically between 0. Near six, the catamaran has a modern sandwich construction. In a performance cruiser L DR is usually between 6. Higher values than seven are reserved for big racers and super high tech beasts. Use 6. Make it too wide and you end up pitch-poling with too much sails on. The commonly accepted way is to design longitudinal and transversal metacenter heights equal. Here we use the height from buoyancy to metacenter commonly named B M.

You can design a sailing catamaran q or narrower, if you like. Wider construction makes her heavier, narrower means that she carries less sail. If the hulls are asymmetric above waterline this is a sum of outer hull halves. B H1 must be bigger than B WL of the hull. Tags Buying AdviceDesigners. Owner of a Catalac 8M how to design a catamaran Catamaransite webmaster.

Yes, I noted the same thing. I guess that TR means resistance. Thank you all for this very useful article. Leave catmaran Reply Cancel reply Your how to design a catamaran address will not be published. A narrow beam, of under 1 meter, will be impractical in designing accommodations in a hull. A value near 2 minimizes friction resistance and slightly lower values minimize wave making. We need to estimate a few coefficients of the jow body.

At last we can do our displacement estimation. L DR near five, the catamaran is a heavy one and made from solid laminate. We can now estimate catamsran empty boat displacement kg : This value must be checked after weight calculation or prototype building of the boat. The light loaded displacement mass kg ; this is the mass we will use in stability and performance dessign.

The beam of a sailing catamaran is a fundamental thing. Transversal height from the center of buoyancy to metacenter, BM T can be estimated. Longitudinal height from the center of buoyancy to metacenter, BM L can be estimated. Too low value of BM L well under 10 will make her sensitive to hobby-horsing. We still need what is an historical novel determine the beam of one hull B H1 Figure 4.

Installed power total in Kw.

Step 1. Kit Design

The most important thing for the catamaran is to carry the sails in the design conditions. The righting moment of catamaran (Nm) caused by the boat size is: RM D 10 ?mLDC BCB 2:= ? RM D 10 3 = ? Heeling moment Sail dimensions P k:= P?LWL P = Mainsail luff (m) E k:= E?LWL E = Mainsail base (m). 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 and a heavy displacement multihull a bit higher still. It is difficult to get much over without a very distorted hull shape or one with excessive WSA. So all multihulls should have a Cp between and Jan 26,  · A catamaran is a design for a boat that utilizes two hulls. Due to the flat, platform-like-potential for the deck of the boat, the catamaran is often purposed with transporting materials, vehicles, and .

Building your own catamaran is another option to getting into your own boat. In this page we will go over the advantages, considerations, and a detailed history and journal of our boat-building adventure with Light Wave. We hope this will give you a clear picture of what lies ahead if you go this route, including:.

It has been said that building a large boat is the closest a man can come to giving birth to a baby. There are several big pluses to building your own boat. You will intimately know every part of your boat. You will know where every wire, hose, bolt, bulkhead, rib, and support is because you installed them! We have often thought what it would be like to just buy a boat from a manufacturer, and know that while owners who have spent a lot of cash or future life to pay off the lien their often possessive and competing-with-the Joneses could not begin to compare to our quiet glow of happiness and akinship we feel with Light Wave.

Our boat is like part of the family. So much time was spent on her that we have a major emotional investment. Many of the production boats that are out there are designs of many years ago because the manufactures have to recoup their capital investment on the mold and production setup.

When you build your own you have much newer designs to draw from. Where do we start? So here is my version of it:. We had sailed our first boat Wave Dancer for five years and had many adventures on the British Columbia coast. This is the book that got me going Carllie was not yet convinced. I must have read it a half dozen times over the next 6 months, each time becoming more convinced that this was the way to go for our next boat. It was really still pre-internet web site days so I wrote to all the designers that were listed in the back of the book.

I would pour over these preliminary printed pages with pictures and accommodation layouts. Next, I put a few dollars down to buy the information packages and study plans from the top prospects.

I should digress to explain that we had never sailed a cruising catamaran. Our only experience with multihulls consisted of some summer sailing on a foot AquaCat beach cat, definitely first generation. It went about 6 knots and that was it. My only other experience was when I was in my early teens back in Montreal: my father had bought this little bathtub-like trimaran about 10 feet long. The most fun we had with it was trying to get the bows to plow under while sailing so the cockpit would fill with water I must see if I can get a picture of it out of the family archives…..

I waited patiently for the study plans. It was like the night before Christmas when I was kid. Oooh the wait! Finally they came, and again I carefully scrutinized the next level of detail. Things were getting a little more serious. The top contenders were:.

Click here to read my comments and reviews on their catamaran designs as well as those of Jeff Schionning. I remember initially drooling over the Atlantic 42 by Chris White, still one of my favorite designs. The most important piece of advice that came out of the material was from Richard Woods:.

What does that mean? Each page in these plan books covers one design. Though there are differences in the accommodation plans, they are all scaled to fit a single page. Axiom 1: The hours to build a catamaran is in almost in direct proportion to its weight. Axiom 2: It takes about 1 hour to create 1 pound of finished boat. In our case we spent 3, hours click here for full details on the construction hours to build a 4, lb. When you think about it, you can only mix and handle so much material per hour.

More boat weight, more material, more hours. Sure there are some economies of scale on a bigger boat, but usually the systems become more complex and these take longer to install. Anyway, back to the decision process: Richard Woods out of England included a video in his design package.

I guess this is what sold Carllie and I on his designs. In the end the fact that Gypsy could be built in components swayed us to pick that one. Many of the initial parts and components could be built in a garage. It was now January of Little did we know it would be 26 months and 3, hours between the two of us until we launched on June 5, We ordered the full plans and we were off and running.

We were ready to build, but where would we start the process? First of all, we live in a tiny sq. I had some wood delivered and lots of epoxy and on Sunday, February 23, , the day before my 40th birthday, I cut and glued the first pieces of wood which would eventually make up the mast beam. Most of the stuff at the beginning were small things.

It was like I was building a model. After about 4 months in the garage, I had made all the small parts and it was time to build the hulls. This meant that we had to go larger facilities. This is the biggest boat yard in the Vancouver area with dozens of commercial and private projects, big and small, under way. I went out and bought one of these big hoop greenhouse buildings.

I took a week off work to erect our shed. I had a couple friends help me for a day and then we covered it with some heavy plastic. We are going to build a boat that is going to fill this? We were out of money by then, so we sold our first boat so we could buy resin and fiberglass. It was a traumatic time as we said goodbye to our beloved Wave Dancer. We were now committed. It was time to build the hulls. Up to that time I had done most of the work in the garage on my own.

It was at this time, July , that Carllie and I really started to work as a team as we learned to laminate the hull sides on our big flat mold. We worked every night after work and every weekend. Over the next 6 weeks we made all the hull panels and bonded them all together over the bulkheads.

We had friends come out to help turn the hulls. By the end of August, we had two open hulls sitting in our boat shed. Over the next several months we proceed to join the hulls with the beams I had built in the garage, and then to install the cuddy cabin, cockpit, and decks. By the spring of , it was staring to look like a catamaran.

Through the spring and summer of , we continued with the major structural components: mini-keels, hatches, stairs, and interior. Then we went on to the very laborious work of fairing the boat before painting.

All through our boat building, Carllie kept reminding me nagging? With that motivation, I kept fairing and sanding and fairing and sanding….. By October we were ready to prime the boat and start painting.

I really thought this would go quickly. I forgot that I would have to do two more complete sandings to sand off and finish the two layers of primer application.

In addition we had to fill countless pinholes — a laborious process somewhat like hiking up a mountain — each time you get to what you think is the top, you see another summit! The boat seemed to get bigger and bigger. Believe me, there is a lot of surface area on a catamaran.

I clearly remember that last sanding: I had reached the end of my physical and mental endurance — I was exhausted. I was ready to move on to the next phase — any phase but more sanding! We now started spray-painting the hulls bright yellow. It was around this time we decided on our boat name of Light Wave. The painting took over a month: the hulls being the easy part, it was the topsides, the nonskid, and all the masking and prep that seemed to take forever.

Happily, the worst of the dust was gone. By March we were in the home stretch. The center bridge deck cabin was completed so we took a week off from our paid jobs and lived on the boat in the shed so we could work all day and not waste time commuting. March, April and May were frantic months as we finished all the final touches: engine installation, rudders, windows, deck fittings, electrical, plumbing, mast, and rigging.

See our outfitting page for more details on what we picked and why, and things we would do differently now. Initially, our electronic systems were relatively basic but included GPS and autopilot see the following link for all our electronic outfitting choices and reasoning for more details. On the Friday night before Launch Day, we still had a number of final things to do, many of them outside.

Unfortunately it was pouring rain. We were tired and very wet but the boat had to go into the water next day so we persevered on till everything was ready.

Launch Day finally arrived!

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