Idea for foam/glass construction

[Ward]

I've been thinking about this for the last couple of days, but I don't have any experience building a boat completely from glass. I'm also into R/C airplanes, and there has been a recent explosion of people building dirt cheap R/C planes from foam. Many of them use BlueCor, which is a readily available and cheap insulation material for houses. It is most commonly found in 5MM thickness. You guys have probably seen it before, its blue, and is laminated on either side with thin plastic, which gives it much more strength than normal 5MM thick foam.

Anyways, I was wondering if it could be of any use building a boat. One idea I had was to make a very light frame for the hull, then plank it completely in bluecor, then cover with glass. Im 99% sure this would work, but whether or not it would offer any advantage im unsure of. The other idea I had was to make a female mold out of it and lay glass in it. Since its laminated with plastic, it should be possible to release. One problem I can think of right away however is that when you bend this stuff alot, the inside surface likes to wrinkle, which wouldn't be very good for a mold. I may get around to trying to make a small test mold for a catamaran hull, like maybe 5' long. If it turns out that it works good, then hey, i'll have a nice outrigger for something later on

[tspeer]

Foam core composite sandwich construction is widely used today for boats. Here's a comparison of alternative ways to do it: http://www.f-boat.com/pages/construction/methods.html

[tgundberg]

I believe the BlueCor is mainly used for insulation purposes and may not be ideal for marine sandwich construction. Plus, it's extruded (or expanded?) polystyrene, so you can't use polyester or vinyl ester resins.....otherwise your core will disintegrate!!

[Ward]

Wow, I didnt know that. Too bad though, because the stuff is pretty cheap, and it does work very well for R/C airplanes. Check this site out, theres pictures of what people have built, as well as information on how its done. There are even people building larger planes from thick blocks of polystyrene, and they're using CNC hot wire foam cutting machines that they have built at home.

EDIT: forgot the link

http://www.foamfly.com/

[tspeer]

For the reasons stated above, styrene foams are not used a lot for structural purposes in boat building. Urethane, polyvinyl, and SAN foams are commonly used, each with its own pro's and con's.
But don't hot-wire them. Urethane foams especially give off toxic gasses when you do. Instead, you can shape them by sanding using an aluminum extrusion or wooden batten with sandpaper glued to it.

Not to mention the problem of interlaminer sheer. These foams
don't have the density or the ability to resit sheer loading or localized impacts!