FenceMAgnet wrote: I believe you are not entirely correct. By using a short servo arm and a long rudder horn you increase the torque available to deflect the rudder. The price you pay for this is reduced travel. Crash90 is correct.

In order to obtain the best possible resolution the servo should be operated with as much throw as possible. If the available angular deflection of the servo is larger than the desired angular deflection of the rudder one should shorten the servo arm (or even better, lengthen the rudder horn) rather than reducing the servo throw.

Whether or not "slop" is increased depend on what kind of slop you are talking about. In order to reduce effects of "slop" in the servo gear train one should aim at using the maximum servo throw. If necessary the rudder horn could be lengthened or the servo arm shortened. In order to minimize the effects of slop in links etcetera, all arms should be as long as possible.

My method to determine what arm lengths is:
a) Determine the desired angular deflection of the rudder, say +-45 deg..
b) Determine the maximum angular deflection of the servo, say +-60 deg
c) The ratio between (b) and (a), 60/45 = 1.33 is the necessary ratio between the lengths of rudder horn and servo arm.
d) Select the longest possible servo arm, say 2".
e) Calculate the required length of the rudder horn by multiplying servo arm length with the ratio in (c), e.g., 2"*1.33=2.67".

/Red B.