Hmm. On the one hand, you're doubling the mass of the "sail", on the other you are eliminating the mass of any spars or tether lines (not to mention any reels,

Hmm. On the one hand, you're doubling the mass of the "sail", on the other you are eliminating the mass of any spars or tether lines (not to mention any reels, pulleys and the like). I'm curious as to how well a bubble like this can withstand being pushed on from just one side.