Foam option(s) for prototype hulls?

Per some excellent suggestions from a recent post, I'd like to use rigid shapeable foam "blocks" to create some prototype/mockup hull shapes for real-world testing. I'd like to be able to strap/glue the blocks onto an existing hull to test performance. Need 36" x 36" x 48" raw size, and will cut/sand to desired shape.
Any suggestions for where I can procure the raw material?
Thanks!
--Jason

 

What kind of use? XPS stryene foam (different from EPS aka styrofoam) can handle moderate loads and is quite cheap and relatively easy to shape.

 

I think this is the guy with the pontoon boat with the cutaway tubes aft, he wants to create a cylinder, rather than one with a slice taken off it, for testing. Polystyrene seems the obvious choice.

 

There used to be a place in Anaheim where I bought dock foam billets to hot wire model airplane wings. I'll try to find them. Meanwhile, contact Martyn Cowley at AeroVironment, Inc.'s Simi Valley plant, and ask him or anyone else there who would know of good sourcing. They use a ton of foam.

 

EPS blocks at least 8'X4'X2' size are readily available and hotwire pretty well. Check insulation suppliers - proper trade wholesalers. Some will even hotwire the stuff for you.

 

I get my EPS from an Architectural Foam place-might be one near you. A few years ago about 8 I think, Hugh Welbourn, inventor of DSS built a 27' experimental test boat out of 1.5lb(I think) EPS and it is still racing.