Foam as main building material ?

[andrea]

Hi there everybody, hope my english is not too bad.
I am new to this great comunity and kind of excited.
I am planning to build my own little boat, probably about 20 feet power boat.
I am considering different materials and foam could be a potential partner.

I was wondering if a boat hull entirely built out of a block of foam could be strong enough or if there is any system to work around that way. :?:

I hope in your competence since i do not have any on this material.

Thanks a lot.

Andrea
atagli@libero.it

[Stranger]

Why would you want a solid foam 20' boat anyway? That's much more foam than you need for flotation, making it very heavy. You still need skins for impact resistance and strength. You still need internal structure for engine/transom motor support.

"Foam" is commonly used to mill a plug with via CNC, but this doesn't make sense for a one-off unless you happen to have use of the equipment for free.

I have seen a site where foam was carved to provide the plug for a fairly simple hull form. I'm not sure how exact the result was.

Why not go with the traditional one-off bulkhead form covered upside down with a foam core and then with fiberglass?

[andrea]

Thanks for replying my message Stranger,
as i was saying i don't have big experience in fiberglass and foam therefore i may definetely say something inapropriate, that's also way i am confident in this newsgroup to get some information.

It will be much faster for me to build a boat out of foam and maybe also cheaper since i have a 5 axix cnc router available at my shop that we don't usually use for foam.

I don't anything about foam strenght and how to protect it, it's only an idea and maybe wrong. HELP!!!

Thanks a lot
Andrea

[lprimina]

If it is a dense foam it will work as long as you use fiberglass on the outer and inner part of the structure and as said above you still will need internal structure..
The first all foam boat I know about personally was done in 1983. she is still floating.
BUT SHE is encapsulated in fiberglass and has internal structure for the important things like engine.. Oh the boat is 56 foot long..

[andrea]

Thanks Iprimina,
do you think a couple of fiberglas coats will be enough as exterior protection?
I was thinking to build also the floor out from the same block of foam that it could maybe work as structure itself, and use some wood or metal for the engine fondation.

Every hint is very welcome.

Thanks everybody
Andrea

[andrea]

How dense the foam should Be ?
Ciao

[turnershells]

Check out what the homebuilt aircraft people do with foam in their planes. There are even some excellent videotapes (North American format) from Aircraft Spruce detailing foam sandwich core construction.

As was said, always covered with some sort of composite material, including e-glass, kevlar, and carbon fiber. Usually they lay down a surface of thickened epoxy to fill the surface, and then resin and cloth are applied.

In my own boats, it's enough to fill the surface of the foam, apply dry kevlar, and then vacuum bag to the surface of the mould. But then, my cores are only 1/8" thick and it's only 1.8oz. kevlar on each side. But it does a very nice job. Also works well over a gelcoated surface.

If you've got a mill, go for it! I wish I had that sort of machine....


Regards,

Matt Turner
Turner Racing Shells Ltd.

[gonzo]

Before asking about construction techniques and scantlings, you need to specify a design and intended use. Surfboards take a lot of abuse and are very light. Swim platforms and floating docks are made of foam blocks with a plywood deck. It is possible to build something out of foam that floats and has propulsion.

[lprimina]

I will look for the web page for the density needed. others here probably know off the top of their heads

[gonzo]

Iprimina: boats with foam core and fiberglass or other types of skins have been around for a long time. However, there is no way to decide on a type or density of foam without the rest of the data.

[lprimina]

yes you are right, What I was trying to find was a page that shows the density for certain applications. You are correct you need to know what, how, when and sometimes who..

[andrea]

Well, i am not sure about the layout but i would like a power boat 250 hp i/o or shaft, probably 14° hull angle at the mid section, classic looking boat with a modern core, something like that, nice design, you know a little fancy a little sporty.

I would love to see other people experience with foam, so please if you find the web address you were looking for please post it.

Thanks everybody for your great help, i know i have a lot to learn but you guys are helping a lot.

Thanks
Andrea

[kboat]

If You Are Thinking Of Foam For Your Primary Building Material, Then You Must Do Your Homework Prior To Starting. 300 Ft. Light Destroyer Are Currently Being Build In Sweden And Norway Of Foam.the Thickness Is 9 Inches. Start With The Diab Webpage In Europe For Initial Help. Good Luck In Your Boat Building. Also, Remember Most Of The High Quality Yachts Both Sail And Power Are Being Built With Foam Variations. Good Luck. :) :)