Since doing some work on the first boat pictured in post #1, I have discovered more of the boat's structure. It is entirely filled with foam, so I assume it was a foam mould that was covered with wood, then fibre glassed. I have cleaned out some of the foam in the cabin area to make room for new servos and sail servo arm. Then I lined the remaining exposed foam with balsa to tidy up the interior. I had thought of restoring this boat with a Bermuda rig, but first, I will try it with the single sail shown and see how it sails. Since a cat rig has its mast way forward compared to this boat, I'm wondering if I'm going to have too much weather helm. Anyway, we'll see when the ice melts in the spring and I will report back.