PVC (Herex, Divinycell, Corecell, etc) foam, 80 kgs per cu metre unless it is a very big boat. It must be perforated (1mm holes at 50mm centres) which you can do yourself by stacking and drilling, or you can pay for. Make sure you blow or vacuum the sheets to remove any lumps from the hole making. You can buy it with tracks (2mm x 2mm is standard, once you are confident, try 1mm x 1mm) to disperse the resin, or use commercial disperser or hardware stuff (fly screen, shade cloth, etc).
Start small (and ideally on a sheet of glass), then build up to full size. Prep is everything.
rob
Hi,
If planning to use sections formed on an infusion table for my 60/40 proa, which kind of foam sheet shall I buy? I don't really want to waste the section I make now - it would be kinda nice to point to some ugly first effort featured in my boat later :)