On Sat, 22 Nov 2003 09:01:09 -0000, "karel adams"
wrote:

:dear all,
:
:what is the blue foam around which composite parts are built?
:is it polyurethane? what brand names does it carry in europe?

It is absolutely NOT polyurethane. Polyurethane will release cyanide
gas if you try to hot wire it. DON'T.

It is Polystyrene foam, trade name Styrofoam by Dow chemical. The
form usually used in homebuilding is PI (Pipe Insulation) Billets, or
FB (Fabrication Billet) or BB (Bouyancy Billets), made by Dow. The BB
is a little ligher and weaker than the PI or FB, which are the same
thing. The PI's come in 8x16x104 inch blocks, or, lately, 10x20x104.

Don't use white EPB (Expanded Polystyrene Bead) board, often sold for
insulation, or used to make molded foam things like cheap ice chests.
You can recognise it because if you break it, it looks like it's made
from thousands of tiny round beads fused together. That's exactly
what it is. It's chemically the same, and you can hot wire it, but
it's not nearly as strong in flex or tension.

Here are a couple of halfway decent primmers on hotwiring
http://www.info-central.org/construction_hotwire.shtml
http://www.spacemodeling.org/new/how_to/Foam_Cutter.htm

Note - you don't have to use nichrome wire. I've used .020 stainless
safety wire, and titanium MIG wire with good results.