ORIGINAL: Rodney
D.J.E., I'm sorry to say you are wrong in your comments in your post above. If you refer to my post above (post #43) you will see pictures of the pulleys I use at the servo end and also the way the cables are attached at the surfaces. When you use a pulley at the servo end, you will always pay out as much line at you retract. What determines whether or not you get slack is the way the cables are attached at the surfaces. If the attachment is aft of the hinge point on the moveable surface you will get a slackening on the line not being pulled as you move away from neutral; if the attachment point is forward of the hinge point, the lines will tighten (a very bad thing) as the surface is displaced from neutral. If the attachment is directly over the hinge point, no change in tension will occur. You can change the amount of deflection by moving the attach point of the horns at the surface being deflected in and out within reason.
Yup.
You've obviously carefully setup some pull pull systems.
The pulley neatly assures that the point the cable is let out is colinear with the point cable is taken in (as well as the pivot center). A decent servo arm attached to a well centered servo achieves the same geometrical symmetry.
At the control surface, the same applies... the attachment at either arm or horn must be colinear with the hinge line.
Also, at the control surface, the spread of the attachement points must be equidistant from the hinge line. (Each of the attach points CAN be 3" from the hinge line, and the spread at the servo can be 20" or 1/2"... Just so long ast the attach points are equidistant from the hinge/pivot line).
The big clue that a pull-pull system is out of geometrical symmetry is that the cable tension is tight.
A well rigged pull-pull system will require just minimal tension.