For you guys who want to max out the use of the torque you paid for AND keep the control surface arm long, there is a tool which makes all the calculations easy. You input the parameters:
Max control surface deflection in degrees.
Max servo arm deflection in degrees.
Control surface arm length.
Control surface arm distance fore/aft from hinge centerline
Servo distance from hinge centerline fore/aft and up/down
It will calculate the sero arm length required to achieve the desired surface deflection with the specified servo arm deflection.
I agree that the longer servo arm is good up to a point so you can get the torque and resolution you paid for. But if it's too long you lose torque out on the surface as well as resolution. This tool tells you the exact length you need to meet your criteria. If your control surface clevis isn't centered over the hinge centerline, it will also tell you the ideal servo arm angle to achieve balanced throws AND display the linearity of the throws.
It also performs a number of other really cool calculations, like the torque required of your servo based on control surface geometry, linkage geometry, and airspeed.
Go to this thread post 10 to download from RCU.
http://www.rcuniverse.com/showthread...88&forumid=230
This thread has some other links relative to this work in post 7.
http://www.rcuniverse.com/showthread...67#post1225441
A couple improvements which would be nice would be some way to add a counterbalance to the equation and adjust for altitude and humidity changes. I suppose for a counterbalance, you could do a manual adjustment by removing the counterbalance area and an equivalent portion of the main surface from the inputs..