RE: Lightning Build
On to the fin. The fin is built up with 3/16" balsa ribs, 3/16" x 3/8" balsa spars, and sheeted with 1/16" balsa. I reduced the sheeting from 3/32" balsa that I used on the prototype to save some weight. The fin came out plenty strong, but the thinner sheeting is going to make finishing a bit tougher. I think if I was going to do it again, I would go back to a minimum of 3/32" sheeting for built up structures.
The ribs are cut with alignment tabs, making construction similar to building a wing.
I use zip lock bags filled with shot as weight to hold down the sheeting.