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Discussion Starter #1
Just want to start a theoretical thread on how to go about building a 24-30 ft Trimaran, possibly by using a mono hull used boat (brand specific to recommendations ie 28 ft hunter) and attaching two separate hulls/pontoons or to simply design one from scratch. Wanna make it sea worthy and able to cruise anywhere from 7 to 15 knots.

I would love to know if there are resources, books, individuals on here and videos also to start this.

I do realize this will be long and tedious but so is life. So let me have it!


Brandon
 

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Farr 11.6 (Farr 38)
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It would take forever to build a 24-30 trimarran from a comventional monohull that would be seaworthy and able to cruise anywhere from 7 to 15 knots since those goals are mutally exclusive. Trimarrans get their speed from being very light in weight with hulls that are very narrow compared to their length.

Trimarrans and cats take a longer time to build than monohulls since workmanship has to be very good, and careful to keep weight down, and you have three hulls to build.

Back in the 1970's I designed a 23'6" trimarran for a friend of mine that was designed so he could build it in his apartment diagonally across the living room and dining room, storing the completed parts in a hallway near the kitchen.

If I remember correctly he lofted the hulls, completed the cross beams and two outer hulls, and had the main hull framed and ready to plank including all bulkheads and fixed interior elements, in a little less than a year. Then he fell in love and his girlfriend wanted to move in if he was willing to change the livingroom/dining room furniture so he gave everything away.

The fellow was reasonably dilligent, typically working a couple evenings and roughly one weekend day a week. This was a very simple boat with a forward cabin with a single berth and an aft caccoon like cabin with another single berth. The berths were canvas laced to holes in the frame and poles that passed through the holes. There was to be a boom tent with cooking under the tent in the cockpit from a single burner stove that stored under the cockpit sole. There was also a storage for a Kohler cooler, an anchor and line, and bucket and chuck it head.

The boat had a rotating centerboard that was lowered through a long centerboard trunk that was opened at the top and which allowed the board to be trimmed fore and aft for balance. The centerboard slot served as the cockpit drain. The centerboard could be lowered to a near vertical daggerboard position during which time there was a canvas spray cover that would need to be rigged. I think that the rig was salvaged from a 24 foot sailboard which I think was a Raven class that had rotted out. I never saw the donor, simply measuring the parts that we had.

Jeff
 

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what Jeff did not said is to use the monohull as a base for trimaran is not very reasonable (unless you have to get "that" hull sailing regardless). Even if the removing of the keel/attaching side floats looks like shortcut, what you would get will not sail as a tri-.
The underbody of a fast tri is different, thats what makes it faster.
Once you reach the point where you need a rig, more options are available.
 

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buy an old beater and fix her up
...or purchase or scavenge:
An old Venture 21 hull, a Hobie 18,
and old Cal 25 mast.
5 gallons of West epoxy, and some carbon or S glass.
Ditch the V21 keel, build a strong centerboard.
Cut the C25 rig in half,to use as beams(akas),
with the Hobie hulls as amas.
Rig with the Hobie rig.
After two weekends and an 18 pack of beer,
you could be cruising at 8-10 knots,
in sheltered water.*

*15 knots will be terminal velocity for this craft.
*This craft will not be ocean capable.
 

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I have a friend who built a trimaran using the constant camber system from the designer Jim Brown.
It took a few years and a whole lot of money and is only about 22'. My friend is a professional builder and cabinet maker.


This is another story about building a huge tri. Really fun read.
http://www.mayaparadise.com/stories/that/that1.htm
 

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Wouldn't it be more fun to go sailing, than to be a builder? Just asking,... from experience. 1 1/2 years of 7 days a week 12 to 14 hours a day, no holidays, and regardless of what you repair or replace, no increase of value (to any buyer or insurance company). Find yourself a good boat to sail, and leave the rebuilding to those of us who have gone before, and didn't take the advice of the people before us. As much fun as fixing, and rebuilding is, I only dream of sailing, not the fun of re-doing someone elses screw ups. Just as a guess, building a tri the size you wish for, and to do what you want, you are probably looking at $150000, and 3000 - 4500 hours of your labour FOR FREE! But maybe your spouse / friends / family will help. Also don't forget a place to build your project, and all the little tiny details, like all the tools and welders and machining. Aw hell, Just Do It!! I DID! (kinda, I am refitting a 42 Tayana) :D
 
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