Originally Posted by erozion
Which is better 3mm or 5mm EPP foam?
I would say use 5mm EPP if you are going to try and make one of these out of EPP. Most people used bluecore which is more rigid so if you go with EPP you may end up with a floppier wing or else you'll need to use more carbon fibre (or whatever material you choose) to brace the wing and stop it bending under load. I suspect 3mm EPP would be far too floppy and weak to make a good wing.
I used 5mm EPP and reduced dimensions slightly to produce a smaller wing with good results. I ran a length of 4mm diameter carbon fibre tubing up each of the bits of foam used to shape the airfoil and another peice to run between them creating an A shaped frame of carbon fibre. This resulted in a wing both stiff and strong and weighing just under 9 oz all up (although only 24" wingspan).
Just bear in mind that whilst you will likely end up with a bouncier more resillient aircraft using EPP than bluecore you'll have to go to more effort to reinforce it to keep it stiff and be very careful not to build it too heavy as a result.