Post your design ideas

Here is my design brief:

Low tech trimaran, inspired by Sardine Run, L7, Seaclipper 24 and IDEC II.

Needed features: Fold able or slideable amas,
VERY inexpensive to build >5000 US
Performance on par with L7.. I want to give an F25c a run for it's money.

Hulls:
6mm Ply, ringframes every 24'' Much like sardine run, except the center hull will have some more flare
I beams for akas like the L7
High volume amas like L7 and sardine run.

33' mast made of aluminum tube like buc 24. Maybe shape foam and thin ply to make a wingmast.

center hull will have the displacement of a 22' boat but it will be stretched to 26' like IDEC II.

Working out the details in freeship. I will post soon.

 

Rapscallion, Looking forward to that pictures.

 

Iteration 1. I'm going to make the floats a bit bigger and change their shape a bit. Still have to add the centerboard. But this is the general idea.

 

Here is a front view. The center hull isn't as big as it appears in the perspective view. The boat has to be built light and cheap, but sturdy. Pine plywood will be used. Marine ply is too heavy, and expensive. The wood can be made rot resistant with a mixture of borax and antifreeze, and a thin coat of epoxy if desired.

 

Here is the pic

 

amas retracted for trailoring

 

I'd agree that it's expensive, but I think okoume ply will be lighter than pine. Have you looked into the high-quality underlayment products like Ultraply XL? I used a product like this in my little beach cruiser, and three years later it's holding up with no problems. A 1/4" sheet of the Ultraply XL is about 20 bucks. It's 5 ply, uses marine glues, and will take much less effort to finish smoothly than pine ply.

 

Great suggestion! I'll look into the ultraply this weekend!

 

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Raps, any numbers for your tri? Good Luck and have fun!

 

Why do you want the deck so wide? And why have that low angeled sides? The beam at WL is thin, but with the waves the boat creat when in motion will make the waves go up on the hull sides and therefor make the water think that that aka is alot wider than it is. And if you are willing to use 5 panels for the hull (6 panels including the deck) then why not put the added panels down in the water to get a smoother hull? I added yellow lines to your drawing to try to illustrate what i mean.
Another thing, i read some years ago a theory to have the amas angeled outward instead of inward. The lee ama is in the water, so it will go rather smooth anyway, and the helm ama will slice the waves instead of slaming them (and it will throw the water outwards instead of into the cockpit)

http://tinypic.com/view.php?pic=b6zeab&s=7 (if the picture doesnt work embeded)
I must add that i have never sailed a multihull, and have little practical experience with boatdesign.

/Brorsan

 

Maybe you have a point. The deck is about 6' wide. I wanted some volume below, but the amas don't have the volume I was hoping they would have, so I will have to remove a bit of volume from the center hull and put it in the amas. I want a budget racer, for distance races. So I figured I would need some carrying capacity. I want to race in the LMSS solo challenge in this boat, and maybe the solo chi-mac. I have been talking about doing this for years, and I'm finally getting around to putting a design together...

I like your center hull idea, and your ama shape comments. Your comments fall in line Dick Newick's new moon ama shapes. I think he gave up on that approach, but I'm committed to a simple build. I want to make the most out of the least... so I want to get the most out of each chine. I'll flip the amas around, and if I don't like it I can always flip them back

There is also some interesting discussions about dory hulls having some advantages over semi circular hulls at higher speeds.. The real question is what is the best all around shape, that one can achieve with a minimum of materials and effort.

 

I want the weight of the boat to be no more than 1500 lbs. Considering the L7 is less than 1400 lbs I think it's achievable. I was hoping for 200% buoyancy in the floats, but I have to reduce the volume in the mail hull first and put it in the floats. NO SEASTAYS!! width will be 8'6" when "folded" and about 18' when fully retracted. I won't know exact displacements until I decide on materials for scantlings.


The rig will most likely be a copy of the aluminum tube used in the buc 24. I was hoping to find some used melges 24 sails for the main, jib and spinnaker. At least those are the target sail areas for the boat.

 

Ray, how come you use traditionaly bows for your cat? How is the building going?

Rapscallion, Is that races serios races, or more of a get together? I for sure think it is possible to design and build a boat that will do well for crusing, because then you dont notice 5% difference in speed that you maybe would have got if the boat was designed by a naval architect. But for racing seriosly, i dont think a first time built 5 panel ply multi will be competeble.

/Brorsan

 

Brorsan

Good points! I would like to race! but for me, racing is kind of like league bowling. I would like to attempt to emulate what was accomplished by the L7 design. The prototype, armed with a beach cat rig, was faster than most corsairs. Only some of the F31's could beat it... That is all I'm looking for....

BTW, Thanks for the compliment! only 5% better if designed by an NA?

 

5% was just a guess, have no clue how much it could be (and of course it depends)

The L7 got round fiberglass below waterline on both aka anda amas which make the water "think" that this boat is made of reinforced glassfibre instead of ply. BUT I think it could be possible to build a fast, all ply boat.

Keep it up! Look at pictures and drawings of boats you like, and try to take the best of them that will suit your need. (the sardine run looks like a nice boat and similar building method as yours, why not try to use the section of it on your boat? I could not stand to not have a cockpit in the boat, else it looks like a nice concept)

/Brorsan