Small trimarans under 20'

thank you! just turn the computer off and build something already or at least go play with the model until its solid and stable! THEN get a video guy (any kid with a camera basically).

moving on now and back on topic....

 

20' and under

Gee, 2F2, I started this topic and the topic is tri's 20' and under-boats I have designed and built for over 40 years. It is a wide open topic even today with nice daysailing tris and high performance tri's covered by the topic. The reason I started the topic was to try to discuss small trimaran design both new ideas and variations on same old same old. There's room for the traditional approach and for radical new approaches. It's an unfortunate accident of history that most people assume that a beach cat is always faster than a beach trimaran.
The trimaran has the potential to be faster, more comfortable and easier to handle.
It would be nice to see some high performance beach trimaran ideas along with the other ideas.

Here's the first 20' tri I designed and built in 1971-it featured a planing main hull. I also designed and built an 80 lb 14 footer in 72-also with a planing main hull and extremely small ama's:

 

How well did/do they perform against say a Hobie 16? What would you change next time around? Foil assist? Center hull foiling with amas not?

 

20' and under

This is what I am doing now: http://www.boatdesign.net/forums/mu...f-righting-trimaran-test-model-36058-124.html
The concept is applicable to 12'LOA tri's and above.
My 20 footer was designed with a planing main hull which back then was unheard of-at least by me. In winds over 10 it was faster than a Hobie 16. The 14 was faster than a US1(mono-same hull as a Windmill with same SA as the 14 tri-80 sq.ft.) and faster upwind than a Hobie 14 but the Hobie was faster (but not by much) downwind.
My new boat also has a planing main hull with the addition of a very small planing ama and foils as well.
Planing hulls can work real well on small tri's-like the Weta, for instance, and a side benefit is more room in the cockpit. The smaller the tri the less chance there is to effectively use a skinny main hull.
On a boat like the Weta where the main hull stays seahugging(though planing) the boat is extremely wet in a good breeze-like firehose wet. You can get out of it a little by sitting outboard to weather. This is another good reason to use lifting foils on the main hull: it is much dryer.
There is tremendous opportunity in designing and building tri's under 20' and the smallest don't have to be slow.
Small tri's can allow a designer/builder to use their imagination to create a nice daysailer or a blast out high performance boat or anything in between.
There is tremendous room for development!

Pictures: a concept model of a 12 footer(almost 14' with the gantry extended). It would be single handed, beach sailable with retractable foils and a planing main hull and planing amas and 17' wide with 170 sq.ft. of sail :

 

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You should post some sketches/pictures of your boat and the mods you want to make. Look around very carefully for carbon tubes for crossarms and mast.
There's a big composites factory out that way called Rock West Composites. Some times they sell seconds. And just keep your eye open for good deals and be patient. Work carefully on the design-that will pay off when you start to make the mods.

Rock West is in Utah! http://www.rockwestcomposites.com/?...F-eYpWJn07M7Dx5G8RC2OelaMHHAlh2e9waAsEC8P8HAQ

 

Possible build method

When I was doing the foils for the Test Model I lucked in to finding an Architectural foam Company with an owner(Sharon) that was interested in doing new stuff. I talked to her about my Crossbow fl monohull and about an idea for a 15.5' tri main hull. The key to the main hull design was that she could cut it out-mostly flat surfaces. It would be cut out of two big chunks of the foam. She would have cut it out of EPS for between $300 and $400 dollars leaving carbonating and installing reinforced areas and the main foil trunk, mast step etc. I even considered laying up 5.7oz carbon on a glass table then bonding the sheets to the styro(EPS).
It seems that this is an excellent way to quickly build a hull if the design restrictions-no compound curves- were ok. I talked to Hugh Welbourn about a 27' DSS model of a 100 footer that was done with shaped EPS-and still races today after more than 5 years. He said it was a great solution but he had it done on some sort of computerized muliaxis shaper. The system that Sharon has is a computer controlled hot wire.
She takes a drawing of the various parts and the machine cuts it out.
It's quick, inexpensive but you have to make sure that the foam that's left in the boat doesn't raise the weight too much.
Something to consider if you have one of these Architectural Foam places nearby-with an obliging owner. She could produce the parts pretty quickly so
if the boat was worth producing for homebuilders it could be done.

Here are some pictures of a model I built in pretty much same way she would cut the parts:
UPDATE-1/9/15-Just found the pictures of the hull cut in the same pieces Sharon would supply-it's the model before it was glued together-last two pictures below-
click-

 

FYI,

I checked, my H14 all aluminum mast is around 30 lbs or 13.6 kg.

 

If you want a 30' aluminum mast you could get an old Tornado.
But it is about 60# with the diamond stays and fittings.
There is a guy here with at least 2 full masts but they are bare (and used). I don't know what he would ask, but probably the only way to ship them economically is to drive a car down with a roof rack and make up some front and rear bumper supports.

Practically speaking the Hobie 14 mast is relatively lite.

Please stop talking about electrical conduit. Its a waste of your time and hopeless optimism

Here is a fairly general discussion about making wooden masts - not solid round tree trunk types. http://idniyra.org/old/articles/carbon_wood.htm

Another article on wing masts. http://www.woodenboat.com/rotating-wing-masts—part-ii

A third article. This one is specific to a wooden wing mast for a small trimaran.
http://smalltrimarans.com/blog/?p=6282

A fourth article about the W17 trimaran. The designer offers a wooden wing mast design for those who have completed the hull for this boat. Not sure you could buy the design separately but it has been a few years since the design has been sold so it might be possible. You might have to look thru the complete website to find the reference. http://www.smalltridesign.com/W17/w17-plans-2.html

 

That is very light. Should be light enough by many standards. Next step is a Star mast.

 

Yeah, it seems like it shouldn't be a problem having 30 lbs of a mast. I can step it by myself, and because it cants, i can pull it all over wherever I want, so weight shouldn't be an issue.

I'm working on some computer designs, it looks like both my Autodesk Inventor and Solidworks programs have expired, so I'll have to figure something else out to do it in.

 

I did some computer work in sketchup, since inventor and solidworks are both expired. Here is a render.

Mast: 22' from Hobie 14.
Mast rake: 5 degrees.
Max mast cant: 10 degrees.
Ama displacement fully submerged:about 400 lbs. Barely out of the water at rest.
Beam: 16'
Ama LOA: 16'
Vaka LOA: 15'11"

What do you all think? I don't really like the beam design, they kinda stick down about 4 inches into the float, so I suspect there may be trouble with it when the amas submarine, like a lot of drag from it. The mast also looks too short.

 

beams bad. mast way too short for beam of platform.

 

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For a first shot it's excellent! I'm impressed. Are you hoping to fly the main hull?
Do you intend the crew to move from ama to ama or to sit on either side of the cockpit-or in the center? You might consider a rudder T-foil in a cassette(so it will retract vertically).
Here are the Hobie 14 Turbo specs for sail area. Are you planning to use the original Hobie 14 rig w/o the jib? Depending on how you're planning on building the boat more SA than the 14 main + jib might be possible. Be sure to get help with the structural engineering if you can. Good Luck....
PS- the ama foils look approximately in the right place-the daggerboard should probably go behind the mast. Depending on the SA you decide on I'm not at all convinced you need such a long ama, especially since you have a foil there for vertical lift. Take a look a Gary Baigents tri designs in the "Alternative.........." thread.


Upwind sailarea 143 ft²
Mainsail area 113 ft²
Jib area 30 ft²

 

Yes I thought the beams didn't look that good. I'll try designing some new ones copying the beams on maxi trimarans, and see how that looks. I'm thinking i'll reduce the beam to 14 feet.

Yes, I want to fly the main hull, which is why the amas are so large.

The crew(me, 150 lbs) can move from ama to ama if they want or sit in with feet in the cockpit. In light air, i'll probably sit on the leeward side toward the ama.

The T foil is an interesting idea, I'll have to remember that and see if I can make a good one.

As for the rig, I'm going to pack as much sail as I can effectively on that mast, so yes, maybe a 110 genoa and the full main. I would love to have an A class mast, but there is no way on earth I am spending that kind of money. Not worth the $4000+ USD.

The daggerboard was behind the mast, but I am putting the new mast step on the crossbar, which is behind the old mast step.

I've seen pictures of Gary Baigents tri, the broomstick, and the amas are about the size of the old ones I have. I have concluded they are way too small for anything other than perfectly flat water. They submerge when I try to step onto them off the dock. I suspect they displace around 120 lbs of water. I will try shortening the amas to about 14 feet or so, and see how that looks.

 

Gary's tri is not "Broomstick"-that is Doug Halsey's full flying foiler design. See the "Alternative...to the Buc 24" thread for Sid, Flash Harry and others.
I thought the beams were ok-it all depends on how they're built. Dr. Sam used
"D" section beams on his 18' long by 22' wide Osprey(below).