RobR, "Benefits
* an optimum of performance on a reduced size plan
* self trimming
* ability to point higher"
Add to that, * less drag, which I think is almost as important as self trimming.
RobR, "* complicated arrangements to induce twist
It is true that wind direction will vary with height too which my only solution is to reduce height with lower performing lower aspect ratio wings and symmetric sections more tolerant of AoA issues. "
I have been working on this issue. . . First of all the situation is the worst where the wind speed differences are the greatest, like a low draggy hull with a large sail area, where the wind will be very slow, and nice clean fast wind at the top of the sail where the sail area is small. It is the difference in wind velocity that is the problem, the Reynolds numbers even change. . .
Then there is the problem that higher velocity lowers the pressure. What that means is that the wind at the top of the sail (or wing) will suck up the air from below. Add that to the vortices loss at the tip and we have a problem. . .
An airplane doesn't have that problem (as much) because the highest air velocities (lowest pressure) are at the fuselage so the flow is more balanced.
At sea however, 2 meters above the top of the waves, the wind gradient is very slight. If we start the wing at that point and have a very clean hull (both from the direction of the apparent wind and the opposite side, the trailing edge is the most important) we should get an even flow around the wing. That comes with lots of benefits, more lift, less drag, lowered center of effort, etc.
Of course we still have the vortices at the top of the wing. . . I am kind of partial to a spitfire wingtip, but the numbers indicate that just making the wing longer do the same thing. The vortices is a function of lift, necessary.
Talador
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Posted by: taladorwood@yahoo.com.au
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