A DIY Homebuilt 16 Foot Trimaran Design

Small Trimaran enthusiast Jim Gallant let me know about a new small trimaran that he designed (and is currently building). This isn’t the kind of thing anyone who doesn’t have a lot of sailing experience or building skills should undertake. But Jim is a true “do-it-yourselfer” sailor who possesses the background to undertake such a project.

And we get to benefit … thanks to his willingness to share it with us :-)

Jim responded to a few questions that I sent him. And he is allowing me to post a few pics from the blog he has set up that will record his building process. Now, here is Jim …
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Building a 17-Foot Trimaran
by Jim Gallant

For a context of my building this original 16-foot trimaran, see the last tri I built, the canoe conversion here. This boat was really successful in terms of performance, ease of transport and economy of building.

The canoe trimaran had problems in winds over 20 knots though. Being so low to the water, it took on water from swells, which meant frequent bailing. I didn’t see an easy solution for that. Then, a steel tube that held the mast up collapsed under heavy load. Still, I liked this boat so much that I decided to build a new center hull rather than fix the steel tube and continue using the canoe.

My goals were to eliminate the wet ride and make it easier to assemble. The canoe tri had a somewhat elaborate system of steel pins that connected the ladder to the canoe and the amas to the ladder. They were fussy to operate and prone to corrosion since they weren’t stainless. No tools were needed to assemble the boat though. This new boat should be easier to assemble as it’ll use 1″ diameter aluminum tubes to pin the ladder to bulkheads and to the amas.

The new boat will actually be over 16 feet in length, and be built of plywood coated in epoxy and glass. For details on design and construction progress to date, see my blog at http://trimaranjim.blogspot.com/.

Gallant 16 Trimaran Rendering

One unique feature for this boat is obviously using the ladder as an aka. My sons are 15 and 12 now, but in the past when I’ve built things like this, I had them in mind. The canoe tri was like a moving jungle gym for them. Climbing out on the ladder to the lawn chairs was a little dicey, but a whole lot of fun. Then once out on the lawn chair it was a really interesting and comfortable place to be. I’m not a big fan of trampolines between vakas and amas. They’re wet and not very comfortable. Lawn chairs, however, are great!

The seating will be unique too. Think of a bench seat for three people designed like a sling back folding wood/canvas beach chair. I considered building seating with plywood, but then realized that fabric seats would be lighter, less labor to construct, and collapsible so the vaka will be easier to transport.

My canoe tri used a single ladder section to connect the vaka to the amas. The amas could change pitch independent of the vaka due to the ladder twisting. I actually think this made for a smooth ride as the amas would ride over swells (up and down) easily.

A Strongback to Build the Trimaran

My new design will still have the forward ladder, but also a rear aka made from a ladder section where the rungs will be cut out. The 2 siderails from the ladder section are then spliced back together with plate aluminum and pop rivets, forming a box beam that’s approximately 2″ x 3″ in width/height. By allowing a small gap between the two siderails, I end up with a slotted track that’ll be used for a traveler for the main sheet. Again, see my blog for details.

I have a Hobie 18 sitting on a trailer in my driveway now. I don’t want to use it because I don’t like capsizing catamarans in cold Northwest waters, especially if I have my kids with me. My 14 foot beam on a 16 foot trimaran should make for nice, flat sailing with little chance of capsizing. Something will break before it capsizes with this width.

Bulkheads For This 16 Foot Trimaran

One interesting note, I used to sail my canoe tri into marinas and go up and down the lanes of boats. It’s pretty narrow in there, but the canoe tri could tack on a dime despite its 14 foot width. It was really fun to sail in tight places. Hopefully this new one will be the same way.

It’ll have plenty of floatation volume for four people. I designed the seating area width for 3 people to sit bench style comfortably, and one person could be out on the ladder. Obviously, with 1 or 2 people it’ll perform better.

I plan on using this sailboat mainly for daysailing. I’ll have to see how much cargo capacity it has after installing hatches in the deck forward of the mast. I found an interesting cheapo boat project where a guy used plastic bucket lids as deck hatches, and with the right adhesive they were waterproof. I may do that too rather than building hatches from scratch or paying for off the shelf hatches. Here’s a link to his plastic bucket hatch page.

It’ll use the same Hobie 16 main and jib that my canoe tri used, along with the slotted mast made from windsurfer masts. Good pictures of this rig are here.

I’ve thought about using a standard Hobie 16 mast, but the windsurfer masts are much lighter, yet are strong enough even in high winds. Plus, the top section bends under very high winds, which may spill some air. Hi performance windsurf sails are designed to do this so they can be used in greater ranges of wind.

Updated Rendering For the 16 Foot Trimaran

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Thanks again for sharing Jim! Be sure to check in with Jim’s tri building blog. He’s added just about ready to install the plywood skin now. — Small Tri Guy

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4 Responses to “A DIY Homebuilt 16 Foot Trimaran Design”

  1. terry burton Says:

    I have built a couple of trimarans in the past. 16 ft x 2 ft hull and outriggers and another
    16 ft x 18″ hull and outriggers.They sailed well but were awful at going about. They both
    had leeboards.
    I am thinking of building a 12 ft x1 ft hull plus very fine outriggers and a dagger board
    with a 6 ft overall beam with seats [ planks ] either side set on the beams.

    does this sound to you a reasonable configuration.

    best wishes
    terry

  2. Small Tri Guy Says:

    Hi Terry,

    I could offer an opinion here, but it would be unqualified (from a proper designer’s perspective). Designing a boat properly takes years of experience, which is probably why you’re small tris didn’t “go about” well in the past. I strongly urge you to check out a few of the smaller model designs you’ll find either here at SmallTrimarans.com or via the links you’ll find here. For example, you may wish to check out some of the smaller models designed by any of the following:

    Richard Woods — http://smalltrimarans.com/blog/?p=3123 or Chris Ostlind — http://smalltrimarans.com/blog/?p=1983 or Kellan Hatch — http://smalltrimarans.com/blog/?p=1921 or one of the other designers of small craft that can be found at Duckworks — http://www.duckworksbbs.com/plans.htm

    Their plans for smaller boats are rather inexpensive and you’ll be able to begin your project being confident that your vaka and ama lengths and beam width are in good proportion.

  3. Jim Gallant Says:

    My original canoe trimaran turned on a dime. You could easily sail up into marina alleys and come about and sail back out. Lots o’ fun.

  4. Jack Spoering Says:

    I think I have just found my boat, Jim. When will plans be available

    Aloha – Jack

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