Chris brought in one of the partially completed frames a while back, the main feature of which is a backbone made of sailboat mast material, a high quality aluminum extrusion in a ovalish shape with 70 to 80 thousandths thick walls and a sail clip groove that works nicely as a place to tuck cables out of the way.

Most of the frame is built of Alumax, a new alloy that is quite hard compared to typical 6061 alloy, machines well, and welds great according to Chris.

Note the trick little cable pulley and mount.