First, lift, by definition, is opposite to weight. Weight is down so lift is always upwards. I realize the layman’s definition of lift is the force produced by a wing and its direction is out from the wing. This is incorrect by the scientific definitions and it results in confusion as to how drag is produced by lift.

If you put your hand out of a car window when you are driving and deflect leading edge upward, you feel a force pushing your hand backwards and upward. The exact upward component of the force is lift and the backward component is the drag due to the lift. If you tilt your hand at a greater angle, you get more lift, but more drag is also produced.

When the ailerons are deflected, both wing panels are producing a force. The panel with the down aileron is producing more force than the side with the up aileron so you get a roll. The components of the force from the side with the down aileron are also greater than the components on the panel with the up aileron. This means the drag on the down aileron is greater than the drag on the up aileron. The result is a yaw toward the down aileron which is opposite to the direction you want the plane to go, hence the requirement for a small amount of rudder correction at the roll in to a bank.

From this it is easy to see that long wings produce more adverse yaw than short wings, scale Cubs, for example. Large, cut-in or barn door ailerons out at the tip produce more adverse yaw than do strip ailerons. A high-speed plane will need less aileron deflection to produce a certain roll rate than a slow speed one so the high speed one will produce less adverse yaw.