colmo-RCU

Hi all, Im making new foam wings for my 4 m discus, as the original built-up balsa ones were destroyed. The thing is Ive never used foam and I don`t know if I should use spars under the balsa sheeting. Also, how do I support de 10 mm rod that joins them inside the foam?? Im sure if I use nothing, the foam will just crush and the rod will go loose inside. Maybe some ply ribs??

Thanks

rgunder

Hi colmo-RCU!

Balsa skins over foam cores without spars works only for small models. I highly recommend that you incorporate a strong spar (probably carbon fiber) into your foam core prior to skinning the wing. As for the 10mm rod, I would recommend a minimum of a plywood root rib and secondary rib located about 10% to 15% of the half-span from the root. Each of these ribs should be bonded to the core before skinning the wing, and the rod should fit snugly into the ribs.

Best of luck on your build!