I have a couple of good weeks into my version of the Ultralight. It is enough different from Mike's design I think I need some sort of a qualifier.
At this moment the inside skins are on the sides as well as the pan. I wanted the inside to be painted (except for the cabinet work), so I have primed, textured and painted two coats of oil enamel on the inside panels.
I'll bolt the sides to the pan in the next couple of days. No screws, bolts! The stringers/ribs/joists will fasten with a hidden nut system.
Yes, it frameless. It is all wood and there is no steel in the "frame" since there isn't one.
I'll add reinforcing to the axle mounts and there will be gussets on the tongue, but it will stay light and simple.
Other than the sides, which are made of 1/2" Obeche plywood, all the other plywood is 1/8 Meranti.
More pictures soon.
dave