The velocity argument holds water, IMHO. If you assume a prop shaft angle of 12 degrees relative to the velocity, that gives an in-plane velocity component of 21% of the free stream (cosine of 12 degrees), a big delta. The down-swinging blade sees +21% and the up-swinging blade sees -21% of the free stream. If one assumes the prop tip speed is 400 knots, and the airplane is flying at 65knots, this makes the down blade see 413 knots and the up blade see 386 knots. The difference in dynamic pressure is 14%, so is the difference in lift.
For those who don't yet see the picture, imagine the prop at an angle of attack of 90 degrees. Then one blade sees all the forward speed and the other subtracts it.
Interesting!
Last edited by NickLappos; 16th June 2007 at 01:41.