Florida's "Sunshine Coast"
is small boat heaven!
What's On This
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).
4. Building our first "real" trimaran:
the tandem rig
(includes construction photos).
5. Building the first lightweight, single-seater
trimaran, "No Commotion"
6. Building Laura's 65-lb "ultralight" trimaran
- see 50 construction photos!
7. The Amazing "Planing Amas"- see
8. No Commotion Gets A Slick
New "Sliding Aka" System!
8.1 - Details of No
Commotion's New Sliding Aka"
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
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.)
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.
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.
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.
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?
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!