> can be used as the middle sandwich layer with carbon fiber. I've learned a lot about FRP construction and I've never heard of cork used as a core matarial. A

> can be used as the middle sandwich layer with carbon fiber. I've learned a lot about FRP construction and I've never heard of cork used as a core matarial. Are you sure you're not thinking of Balsa? Balsa is a hardwood despite being so light, so it has capillaries in it. The wood is cut into blocks and then the end-grain is pressed into the wetted-out FRP mat. The resin in the mat is drawn into the balsa through capillary action forming a very secure bond. Manufactured foam core material doesn't have capillaries and therefore has trouble forming a bond with the resin. If you're using foam instead of balsa core, the manufacturer will specify a bonding agent that you need to use between the mat and the core. If cork were to be used as a core, I'd think it'd have the same problem bonding with the resin as foam has, and you'd have to use a special bonding agent formulated for the cork. EDIT: Heh, after posting I decided to google around for cork FRP core. It turns out there is a company selling a core material manufactured from cork: http://www.mcmc-uk.com/products-corecork.html http://www.mcmc-uk.com/products-corecork.html; most of the users of it I can find are surfboard builders though. Here's a not-very-long thread about it on boatdesign.net: http://www.boatdesign.net/forums/materials/corecork-material-32251.html http://www.boatdesign.net/forums/materials/corecork-material...