RobRiley, "its just a flow modification that increases lift until stall, but they are devices that hugely increase drag in that process."
No it doesn't increase the drag hugely. Just look at the NACA Charts
While this shape isn't particularly good at generating lift, it has the interesting property of generating very little lift (none) for +/- 2˚ directly into the wind which makes it a very good choice for a wing that will spend most of its life just being a wind vane. And if you look at its drag coefficients they are very good too something like .013.
I would be willing to bet that a single multi stranded wire stay on a normal sailboat has more drag.
RobRiley - "So the broader question becomes, what is the quantity of that drag force in high winds and the resultant weight of the spar to carry it. Now parallel that weight/lift equation with that of an advanced but ordinary sail. Im still uncertain about which wins."
The symmetrical wing is the huge winner, it isn't even close. Especially as the camber (thickness) increases the wing gets proportionately stronger stiffer and lighter (up to the limits of the Epoxy and Carbon fiber), the bearings get more expensive though.
Look at a competition sailplane where 30 meter wingspans are common. They are probably designed for twice the Reynolds number so doubling the thickness of the wing as a sail looks like it would work.
Talador
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Posted by: taladorwood@yahoo.com.au
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