If you can buy a small piece you could do some experiments. Glass it both sides and see how strong the sandwich is. I would think it would work just like the high density foam they use on surftechs. May be a little heavy.
If you read some of the stuff on cork rails, I seem to remember that cork absorbs a lot of resin, pretty deep, so may not be what you’re looking for or you may need to work around that…
I don’t think I would use cork in a sandwich construction because it has zero stiffness. It’s a totally floppy material. If you notice it’s always paired with balsa for doing rails- the balsa for stiffness, the cork just to build up thickness (and they look good together and sand easily). So unless you stringer the board up a lot I think you’ll end up with a floppy board that’s easy to snap. In large sheets it’s not necessarily cheap either.
It also has almost no burst or shear strength. Balsa & high density sheet foam add a lot of strength so you can use less glass cloth…I think with cork, you’d end up using more than normal.
Now, if you could glue together enough wine bottle corks (with foaming pu glue) to make a blank…that could be interesting. Start drinkin’!
use the cork as a sandwich material to separate your two laminate layers, top and bottom, over an EPS core and you’d have a very flexible board! Might be good for surf! Prolly suck for windsurfing.
It would not provide a board with much pop though as the cork would deform under pressure. It’d be heavy due to resin suck.
If you wanna make a board like this, can’t help but think that you’d be better off with some model aircraft garde bendy-plywood, or some hardwood veneers (0.6mm…though these are full of their own pitfalls and headaches).
Other use, that would be great, would be deck pads. Mmmmm…squishy…that’s about all I’d use cork for.
I’ve been thinking about building a sailboard for some months.
I finally get the EPS foam.
It’s impossible for me to get PVC or balsa sheets for the sandwich core, which is quite necessary fo sailboard stiffness.
You might try www.lonestar-models.com They sell balsa in bulk for a reasonable price and will ship to europe for a reasonable price too. I think the cork is unsuitable as a sandwish material as it has all the wrong properties. Good for impact protection with a really flexible resin, but that’s bout it. It bends nicely though.
“PUfoam/fibreglass/polyester lam resin/3mm cork sheet” test has been done and FAILED at first stage.
Resin was completeley set after 24h, fibreglass was perfectly glassed to the PU foam, but when I untied the tape that was compressing the whole pack, the 3mm cork sheet simply slipped away from the fibregalss. Cork was sticky and olily.
It seems there’s some incompatibility between cork and poly resin. Cork was completely wet on resin, but the resin simply didn’t set on/in it.
I’ll post pics next week.
Now I’m running the “1lb EPS/fibreglass/epoxy resin/3mm cork sheet”. First bottom stage has been done with SUCCESS.
good idea cork is cheap and easy to fin in spain. Othewise you can use modelims balsa (is what I use in my compsands) it can cost ambout 40€ for a 6’5" board or ask at PLASTICELL in Barcelona if they can deliver you some PVC foam.
If you had asked two month ago I was surfing galicia and could bring it to you.
I’ve been busy this week and also very excited about the results of the tests.
As I said before, I started the test for a “PU foam/glass with poly resin/3mm cork sandwich core/glass with poly resin/poly resin hotcoat” combo, but something failed when glassing the inner glass+cork to the PU foam core.
I thought it was a matter of some incompatibility between cork and poly resin, since the completely resin saturated coork sheet simply peeled away from the fibreglass.
Then I started a new combo using “#1EPS foam/glass with epoxy resin/3mm cork sandwich core/glass with epoxy resin/poly resin hotcoat”, but I decided to give another try to the poly/cork combitation.
So finally, this is the result for the hybrid combo “#1EPS foam/glass with epoxy resin/3mm cork sandwich core/glass with poly resin/poly resin hotcoat”.
Cork+outer glass saturated with poly resin work great, so I guess the first combo failure was a humid PU foam issue or so, I don’t really know.
