I'm building a foam core solid wing
for an iceboat/land yacht.

I'm curious...aside from the discussion of "luff tension" et al, what's the
benefit of a solid sail?

My dad built an iceboat and I have vivid early-childhood memories of skimming
along, face inches from the ice of the lake, going at what seemed a terrific
rate of speed. Aside from the usual risk of getting clobbered by the boom when
it comes around, managing the sail didn't seem to be a problem for him, and I'd
think it would give you more versatility, not to mention being easy to wrap up
and tote.