JT - I've read a book describing wing tip "sails" or "feathers", much like the outboard primary feathers on an eagle's wings. Is this your Scissorhands device?
I imagine such devices would be easier to rotate to the optimal angle of attack than a winglet, although the reference does not provide quantitative data on their efficiency. FYI it's a book by RH Barnard & DR Philpott.
One wonders what airliners in fifty years will have attached to recover energy from the airflow.
O8
PS - Perhaps this might help clear up some disagreement?
If thrust is defined as a force acting forwards, and if one agrees that there is a small forwards component to a winglet's net aerodynamic force, then there is a thrust force present. Much disagreement here is due to a different definition of thrust I think.
Last edited by Oktas8; 13th July 2004 at 10:16.