load on flight controls and servo selection
 

with the new 3D style of flying, we can see plenty small planes fit with hi torque-speed servos. Those servos literally double the price of the plane.
I agree that on flight controls like the rudder there is a high force aplied during 3D figures, but I believe that in a lot of cases the servos are "oversized".

Modelers with low budget could be intersted in some reliable rules to select proper servos.....

load on flight controls and servo selection
 

I posted a general equation for servo torque requirements near the bottom of this thread http://www.rcuniverse.com/showthread...246&forumid=35 which I believe is reasonably accurate. The meat of the msg is the equation in boldface , but it would be beneficial to read the rest of it to see how the equation was arrived at, i.e. don't accept formulas blindly..

load on flight controls and servo selection
 

Two things to consider when selecting servos for 3D flying.

First; the more extreme flying will introduce higher hinge moments on the control surfaces.

Second; The linkage is usually installed to increase the maximum throw which gives the servo less mechanical advantage. You normally have the control rod on the outer servo hole and the inner control horn hole. Therefore the hinge moment torque is increased when it gets to the servo.

Tom