To fit an electric trim to the rudder and elevator, how do you a) determine the size of the actual trim tab to be effective and b) determine the size of the servo motor?

Pierre Swanepoel

Very good question.

You have to make some assumptions based on the dynamic pressure on the tab to calculate the torque about the tab hinge.

Get yourselves a copy of Von Doenoff "Theory of Wing Sections" and look on page 215 and up.

You probably cannot make the hinge and tab too strong :)
If it fails you die.

Paul Lamar