DSK wrote:

Nav wrote:


... Second they are not symmetrical in section. The winglet with the
negative angle of attack generates less negative lift in the vortex
than that with the postive angle. The net effect is postive lift and
again vortex energy robbing.

OK?


Dude, check your geometry. Each winglet may not be symmetrical, but they
are paired. The overall design *is* symmetrical. Any beneficial effect
they have on keel efficieny is in the area of reduced drag and increased
lift on the main keel section.

Yes, I said the lift was coupling energy back into the keel. Why do you
have to say the same thing and yet not agree?

Now please try to think about it a bit more. Look at the vortex down
it's axis and imagine an (e.g.) Clarke y type section across the vortex.
Does it produce more lift on one side than the other? The key is that
the vortex gives one side of the wing a negative angle of attack and the
other an equally postitive angle of attack. Now couple that to an
assymetric type section (e.g. Clarke Y) and what have you got? Do you
get it now?


Cheers