672 kg/m³ PVC foam?

I'm ordering some materials for a medium sized multihull build, but marine grade stuff is very hard to find here. I'm importing some rolls of fiberglass, and a pallet of p80 foam, however I estimate I'd still be short about 10 sqm. Not enough to foot the cost for an additional pallet of foam, but I recently found a local hardware store with 4x8 PVC foam sheets used for construction and I weighed a 1 sq ft sample (0.5 inches thick) at 1.75 pounds. That extrapolates to about 672 kg/m³. My current displacement puts my draft at about 1.5 ft, so i have extra weight to play with before reaching my 2 ft target. Has anyone here tried using this type of foam?

It seems to be closed cell, and is quite sturdy stuff unless I pierce it with something sharp. I can't bend, break, or compress the 0.5 x 10 x 14.5 ft sample. The surface is very smooth however, so I assume I'd need to sand off the coating.

Materials on order:


What the foam looks like:


Is it sensible to assume that due to the high density even at a somewhat lower assumed quality this foam core could be used for bulkheads etc? Maybe also for the lowest parts of the hull and mini keels? What tests should I be doing to the sample?

 

need datasheet

 

Unfortunately I have no idea how to get that. I asked the owner of the shop and he said he isn't sure either. If I had the datasheet then I'd just go do some more research on it. But in this case I'm trying to figure out if anyone here is familiar with these products or know what tests I could do to figure out if I can use it safely. My only other option would be marine ply, which is really hard to source here, very expensive, and gives me worries about eventual rot.

 

Do you have any reason to suppose that resin will bond to the skin of the foam,or that crush resistance of the foam beneath the skin is adequate?The impermeable skin might also make it difficult to avoid having air pockets trapped in the laminate.As fallguy says,a datasheet would be very useful,but in the meantime a laminating test piece might be a step forward and then you can compare with a similar sized sample of the P80 foam,if that has the qualities you seek.Until proven suitable I would suggest limiting the use of the material to easily cleaned and non-structural furniture or confining the use of the boat to water that is shallow enough to walk ashore.

 

What you're saying makes sense. I plan to test the adherence of the lamination and compare once I get the p80 foam. The inside of the foam seems a lot coarser than the skin (seems to be about 0.3mm? thick), so that's why I think I'd likely use a sander to remove the outer layer before trying to stick anything to it.

I'm just not sure what other tests to do? Maybe check how much weight I can put on a square inch before it collapses?

 

Surely your supplier knows who he buys it from? Just follow the supply chain back to the manufacturer and a data sheet. Resin compatability, peel and crush comparisons to your P80 would be worthwhile on a small sample.