Outrigger construction

[Rumars]

Dejay, while in principle I agree with your post you must remember that size and location are still determining factors.
The OP has Thailand as location and a trimaran in mind and that can open up avenues. If hireing 6 people for a week to laminate, sand and polish is feasable, intelligent infusion is a moot point.
Material prices are also location dependent.

 

[Dejay]

Good point. It might also be cheaper to import structural PVC foam from China. Or plywood for that matter.
I'd be curious if there is any country where boatbuilding would be cheapest, either materials or labor or both. I figure materials would be cheapest in China since almost everything is made there.

 

[Qmaran]

Thanks everyone for replying. Some useful suggestions in there. I completely get it that you are all well meaning trying to save me a lot of trouble. I went through the same thing when I got into speaker building. Building real high end HiFi speakers is also not easy. Everybody told me to build from plans and my first few attempts at some small speakers disappointed me. Even though many people who heard them were blown away and asked me to build them a pair. After a year of tinkering, getting a calibrated measuring setup and importing hard to get crossover parts and drivers I built a pair of speakers that are completely self designed and give me a lot of joy and pride. I believe I can do the same with a boat. It doesn't need to win races or win beauty contests. It should sail adequately and be safe to cross oceans.

OK, back to the outriggers. They are combined about 4m3 in volume. So air or light foam doesn't really make that much difference and i want foam for buoyancy anyway. A light foam is about 30kg/m3 so 120kg extra for the two hulls. My newest idea is to use foam planking with polyurethane glue and fiberglass cloth. So light foam plug --> PU glue+fiberglass --> foam core strips --> Vinyl/fiberglass.

I need to test how much puncture resistance the PU glue + glass cloth adds and if the soft foam doesn't deform under vacuum. I think it will be OK with the PU glue, glass and PVC core around it though. It may be a while before I have materials for testing but if I do I will report back my findings.

 

[MassimilianoPorta]

There is a part two with the actual infusion and demolding. Perforated core is used. Most things done in a mold are done this way.

Thanks a lot!

 

[Rumars]

Your newest idea is crap and shows you don't understand the basics of cored construction.
I'll try one last time. If you can't say by just looking at the lines how the boat will perform in various conditions and be at least 80-90% right you have no business designing one.
This is no speaker cabinet sitting on the floor and you don't get multiple atempts to doing it right. You build the thing and go sailing. The happy case is it breaks apart first launching in sight of land and rescuers. The bad and more likely case is it breaks apart in a storm way out there.

Just for kicks please explain why do you want foam filled amas? A properly designed foam cored multihull will float above the surface even if completly filled with water and having all stores on board.

Look, if your goal is to learn boat design then be my guest. 2.5 years is barely enough time to go trough a proper full time formal education in the field. If your goal is to build a 40ft trimaran then 2.5 years is tight for the lone amateur working full time but doable with (hired) helping hands. So decide what your goal is, if you want both you need more time.

 

[Dejay]

Here is an article I just stumbled across about the build method for the farrier trimarans. Maybe that help you decide on a good build method:
a.b.b. - amateur boat building - vertical foam strip planking http://amateurboatbuilding.com/articles/howto/strip-plank/vertical_strip.html

BTW Richard Woods also has a design with female half-hull molds to for building foam sandwich with vacuum bagging or I guess also vacuum infusion.

I also was curious about using polyurethane as a matrix and read something about using it for wind turbine blades but there is probably zero advantage for this compared to epoxy. You need to consider things like elasticity of matrix and fiber. You might also need special seizing. And costs? PU paint is quite expensive so I assume as a material PU will be more expensive than epoxy.

 

[Zilver]

Having helped building a farrier trimaran I can say that the vertical strip building method is easy and quick. You build the first half, laminate the inside, attach the bulkheads and put that first half aside. Then you reverse the frames and build the second half, lower the first half onto that. Then you can fair the foam outside, glass it,and fair/paint again.
The foam for the core (divinycell h80 or equivalent) is relatively expensive.
Hans