One off composite construction

I was wondering if anyone has built a composite boat without a mold. I was thinking of making a very light framework for the foam core for the deck and hull. the foam on the framework would create the shape. The foam would be covered with fiber glass or carbon fiber.

Would this work?

 

It's quite common for "one off"s.
http://www.javelins.org/Technical/buildyourown/malestringermould.PDF

 

It's done this way all the time. ..

Another approach that might save some fairing time is to buid a female form from CDX frames and Fiberboard (pegboard material), ...fill the seems and hard chine edges with Bondo, sand to shape, resin and wax the female mold. From this mold you can lay up the gelcoat, laminates, and core. It's a bit more involved up front, but produces a fairer hull than just laying foam on a frame. The amount of time you spend up front will be a good investment in your finished hull.

 

Is a 1 off worth messing with a vacuum? I'm looking at an 8M trimaran. I was thinking of laying the epoxy, then going to vacuum; instead of messing with infusion.

 

Sure! It depends on your desire to have the most state of the art build... or not. If you just lay-up the laminates by hand, weight the core down with sand pails or whatever you have thats heavy, then lay your last laminates...all by hand your boat will be slightly heavier than if you had vacuum bagged. If you are very careful not to allow the laminate to develop any voids, you will have a solid boat.
For an 8m boat, vacuum bagging is well worth it...not necessary, but worth it. Vacuum bagging is not as difficult as it sounds and once you get going, you'll find it to be a great tool.
Infusion is a bit more involved and your mold needs to be up to the task. Infusion requires a proper mold, not just a cheap built form. So in that sense it may not be worth the trouble...

 

Thanks everyone for the info!

 

vaccum bag foam with a couple layers of glass or kevlar each side with epoxy. used to do this for hydroplanes and it was stronger than plywood and light as a feather.

 

drill small pinholes in the foam, then lay a layer of nylon(peel ply) over the final lay up, then cotton wadding on top of that(soak excess resin), bag it over night. Insane strength

 

what kind of foam did you use? was it expensive?

 

it was a marine pvc core foam. Not too sure on the cost as i did not handle that aspect at the time but i know it comes in 4x8 sheets and stacks of like 10 to a box. We would shape and bevel the edges so everything was uniform.

http://www.boatdesign.net/articles/foam-core/

this will explain the benefits and concepts. Whn vaccum bagged this stuff with glass or kevlar will blow your mind at how light it is and how GD strong it really is. I am thinking about making a really small and light PWC powered by a small outboard.

 

My bad, it wasnt pvc, it was this stuff


http://www.noahsmarine.com/Canada/Core_Materials-Can/ATC_Chemicals-can/atc_chemicals-can.html

 

I have done 21 foam One offs mostly out of Airex and Core cell the quickest system is the Core cell "Bead and cove" system it eliminates a lot of work in the set-up .

 

You can also just buy perferated foam, with the holes already drilled.