My wife Laura's 16' trimaran with 84 sq.

ft. sail on a homemade unstayed mast.

 

Welcome to...

"DIY-Tris.com"

 

A Web Site For Do-It-Yourself 

Small, Homemade Trimarans

 

Presented by "Dr. Frank" Smoot, and

dedicated to DIY boatbuilders everywhere!

 

My 16' trimaran No Commotion with its

optional 124 sq. ft. rig from a Laser II.

 

 

Florida's "Sunshine Coast"

is small boat heaven!

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What's On This Site:

1. Why I have come to believe that small trimarans are the only way to go. [click here]

 

2. A Brief History of the 15 or so homemade boats and rigs I have build over the past two years [click here]

 

3. Our first "trimarans"- made from kayaks (includes construction photos). click here

 

4. Building our first "real" trimaran: the tandem rig (includes construction photos).  click here

 

5. Building the first lightweight, single-seater trimaran, "No Commotion" click here

 

6. Building Laura's 65-lb "ultralight" trimaran - see 50 construction photos! click here

 

7. The Amazing "Planing Amas"- see 40 photos! click here

 

8. No Commotion Gets A Slick New "Sliding Aka" System! click here

 

8.1 - Details of No Commotion's New Sliding Aka" System

My original idea was to have pivoting akas, like those in Jim Brown's Seaclipper 20. But the more I thought about it, the more cumbersome and impractical it seemed on a boat that was going to have to be de-trailered and rigged from scratch every time it went out. Too many compromises, weak spots, and too much weight. Great idea for Jim's 20 footer, but not so much for my lightweight 16 footer.

 So I shifted my thinking to the sliding-aka approach. Needless to say, there are a lot more ways to do this poorly than to do it well. I really wanted to get it right on the first try, so I spent countless hours in my "mental CAD" program trying every variation I could think of, and lots more hours at the drawing board (And yes, I really do draw all my ideas out -- on graph paper. I'm simply too design-program-illiterate to use even the simplest boatbuilder software.)

 Anyway, I finally settled on this design, which uses 2 1/2" dia. .085 seamless aluminum tubing. Pricey stuff, plus I then paid to get it galvanized. But I really love this tri of mine (it's name is "No Commotion"), so I figured it was a good investment. Of all my hull designs, this is the quickest, quietest, smoothest, and driest.

The aka tubes each slide in a pair of 2 1/2" stainless steel U-bolts (5/16" dia.) I put a bit of clear plastic tubing at the top of the U-bolt arch, to stop rattling and scraping, and I also put a small plate of plastic (made from cheap cutting boards) under the tubes, for the same reason. Then I treated the galvanized tubes with silicone, and they really do slide in and out pretty easily.

I added a small stop bolt to keep them from extending too far. The U-bolts themselves are through-bolted into a 2 x 8, which is in turn bolted to the sheer clamp of the hull via pieces of aluminim angle. I use a drop-in bolt that fits into a hole in the 2 x 8 to hold the tubes in place once they're extended, and a small plastic shim to eliminate any possible play or rattling.

As I'm sure you can see, the port ama is a bit forward of the starboard one -- about 3". But that makes not the slightest difference in performance. The biggest challenge with something like this is the alignment on everything -- which is super-critical. You have virtually no margin for error if the amas are going to be able to slide in and out freely without binding anywhere. But when you get it set up right, this system is a dream to use. It dramatically reduces both assembly time and effort on the beach, and has cut a good 5 minutes off the process.

The real surprise for me was how much "stiffer" the boat is now. I had originally been using 12' long 2" dia. tubes with 1/8" walls as akas, bolted directly to the sheer. Now, with the combination of (a) the larger 2 1/2" dia. tubing, (b) the 2 x 8 crossbeam (which extends out the support quite a bit farther), and (c) the new "planing" amas, the boat just doesn't heel, so the wind power gets translated directly into forward motion -- lots of it. And hey, isn't that what trimarans are all about?

Bottom line: It's not the easiest thing to engineer or build, but it's a huge improvement in both strength and functionality, and (IMHO) it just plain looks cool!

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