Daniel, what Pointus is talking about is an effect induced by the propeller. Since because the propeller is also a "wing" when you nose up, the the angle of attacks change between (or among) the blades. so the down going blade and the up going blade produce a net force that make a yaw - Asymmetric propeller effect
Heavy 4 engined turbo props have their vertical stabilizer offset the butt line of the fuselage to compensate this, and not sure about the Cub but small single engined piston props have their engine little angled against the butt line. I have also heard (not seen yet!) there are small props with wash-in in one wing and wash-out in the other.
the maximum effect of these forces induce at the cruising speed, so they design the plane to be stable for the cruise.
stand to be corrected!
Last edited by code0; 8th November 2012 at 15:16.