Problem: as left/right flaperon is applied, path length of the cable changes dramatically, because the top of the elevator control horn is located about 12” off the axis of rotation of the flaperon torque tube.
With cable tension set to 20lbs at neutral stick, I was seeing 10-15lbs at full left (very slack) and >35lbs at full right stick. This was tight enough to cause the elevator horn to bend!
Solution: I have added a pulley right behind the lower access hatch, on the bottom of the fuselage. It's pivoted so it can swing left and right, and about 3” right of center (because the horn is on the right of the torque tube). I have also lengthened the cable slightly by adding a linkage.
The change in path length is greatly reduced. The ideal location for the pulley would be lower still, but that’s not possible because of the upward slope of the tail-cone.
This results in almost no change in cable tension with full right or full left flaperon. I have tension set at 20lbs with stick neutral, and I am seeing less than +/- 3lbs through full left-right-up-down stick.
Elevator now does not feel stiff with full right flaperon applied, as it used to.
If anyone wants pictures, please contact me at email@example.com