Building a beach trimaran....calling all engineers.... :: Catamaran Sailboats at TheBeachcats.com

some excellent info in this thread

Now that Bush, Henrik, Dave and I have our boats sailing, mods made and dialed in, and others like Munt have are enjoying their Multi-23's, I though it would benefit all of us to start a discussion about our experiences and observations about different build characteristics and behaviors of baots in the 20-24' range. So if you either own or have built a small tri, please chime in and share your boat's specs, characteristics, observations and experiences. This could provide further improvements to all of our boats and or lead to better builds in the future.

Here are our final specs:

L: 23'
W: 16'
Sailing weight w/ engine, safety gear, sails, but no crew: 1,100
Amas: extended N 6.0 hulls to 23'
Mast: 31' carbon mast, from 1995 Nacra 6.0 experiment
Mainsail: 230' sq/ top of technora flex, by Slip Elliot, on elongated sail slugs in mast track
Jib: 100' furling, also technora flex
Downwind reacher: 295' furling maxi-reacher of code 0 material
Spin: off of Nacra 6.0, wrong shape for this boat, reacher works better
Foils: Rudder: Inter20 dagger in lifting cassette on main hull; Dagger: Carbon Hobie Tiger dagger, reinforced, vertically hung
Furlers: all continuous line Facnor FX 900 for jib, screecher and maxi-reacher, supplied by Mike Leneman
Waterstays: wire with turnbuckles, continuous tensioned attachment through hull
Lifting foils: none

Observations and lessons learned:

•Plenty of bouyancy in extended 6.0 hulls, have never even come close to pitchpoling downwind, in fact they ride up nicely with weight in back
•Would lifting foils in amas help perfromance? Perhaps when hardpressed, but the added weight, cost, complexity, weed gathering, and drag when going slower ruled them out for us. Plus, the weight of a 3rd person to operate them more than cancels out their benefit.
•We can do 12-13 knots upwind, pointing as high and sailing faster than tricked out F-31's in 15-20 knots of breeze
•Top speed so far is only 17.5, but our glory seems to be higher consistent speeds over time than boats with a faster top speed
•There is a distinct turbo mode at 12-15 knots of breeze where the boat goes from being decently fast to accelerating like a rocket
•It appears the higher the wind above that only increases her performance.
•Below 5 knots she is a dog, and tri and monos we hose in 15 knots pass us like we're parked
•We have a light air screecher on the way, but have not experimented with it yet, hopefully this will help light air performance
•Body weight placement forward increases boat speed by at least half a knot in light air
•Seems we reef between 15-20, although we have probably held sail to 20-25 knots aith no adverse effects
•Boat seems to run best with main hull mostly out but not all the way out.
•I think one of our strengths is the main hull has less rocker than some boats, so we maintain a long waterline in most conditions.
•Roller furling headsails a necessity on such a narrow bow, real happy with facnor 900 fx's, including bearing headstay load with jib
•Should have built the transom a little taller, moter boat wakesor stopping in a seaway can slop in, but we do have venturi drains in the back
•Mast compression even on a boat this size is significant, make yoru underpinnings and mast base sturdier than you might think (had to beef up ours)
•Having a cassette rudder sure helps shed weeds/grass when racing
•Lifting rudder and dagger part way when jibing downwind seems to help some
•Plenty of steerage and area with an inter20 dagger as your rudder for this size boat, and on main hull.
•Running traveler and mainsheet down the boom to both sides/nets works very well and is so much more convenient than dragging it back accross every tack
•Marelon winches are not sufficient for the loads on a boat this size, even though the published loads were with limits;, we had to upgrade to smallest lewmar aluminum
•Addition of furling maxi-reacher increased speed but bent mast excessively (holy crap moments) with halyard at 3' above hounds. Decided to RF mast with uni carbon instead of add running backstays, and it has worked so far.
•Inner and outer diamonds were the right choice to strengthen our carbon 6.0 mast for this higher righting moment
•Long sail slugs with a little McLube work like a greased pig on the track, can drop main to deck doing downwind in 10 knots in less than 10 seconds
•Love our Honda 2hp aircooled longshaft engine. Light, dependable, and only sips fuel. Can do 5.5-6 knots without adverse current/wind
•Overall we are pretty dang happy with our boat and her performance
Questions:

•Do you find lifting foils to be helpful in a boat this size, if yours has them?
•Have you found that more than 2 people significantly slows you down for racing?
•How do you pitch compared to larger F-31's and such, and does your ama shape dampen pitching?
•What do you like best about your boat?
•Any huge changes you would make if you had the cash and energy to do it over?http://forums.sailinganarchy.com/index.php?showtopic=125891

Building a beach trimaran....calling all engineers....

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