Gentlemen:

I need some advice setting up the pull-pull system for my 1/4 scale WH extra. I am using a Hitec HS-7955TG rudder servo. The geometry is square - control horn pivot points exactly on the hinge line at the rudder, and the pivot points are even with the axle of the servo at the fore end. Arm length (not that it matters) is 2 1/4", and matches for the servo arm and the control horns.

The problem is that the servo sings quite a bit when energized at neutral rudder. I have loosened the tension on port and starboard cables to the point that they have perceptible sag (perhaps 1/4-3/16") back through the fuse. The servo does not sing if the H9 arm and cables are not connected, so the servo itself seems OK.

What actually is the proper tension for pull-pull cables? Any suggestions for eliminating the singing? Obvioulsy, the servo is drawing higher current while singing, so I'll have a negative impact on battery life if I cannot solve the problem.

Any ideas?

Thanks in advance.