Originally Posted by ThermalBuster
Mark, Could you please explain why the rudder is so much more effecient at canceling adverse yaw than aileron differential. I have heard this before but I'm not able to reconcile that conclusion.
Aileron differential uses drag to create a yaw moment, while the rudder uses lift. By definition, a drag force sucks energy from the glider, while a lift force does not.
The lift force on the rudder does have some associated profile and induced drag. But for a given yaw moment, this additional drag on a typical rudder is much smaller than what's required on the upward-deflected aileron. Increasing the aspect ratio of the vertical tail makes it even better in this regard.