Dave,

Measure the length of the control surface - perpendicular to the hingeline (front to back), multiply this by the sin of the angle and that will give you the deflection in inches at the control surface edge. For tapered control surfaces this will vary as you move inboard to outboard....

sin 10 = .1736
sin 12 = .2079

For a 1 inch length at 10 deg, the deflection will be .1736" or about 11/64"

Hope this helps.

Steve