Originally Posted by
thailazer
After putting more time on the Cub, have found that the elevator control is the one to make the bird expose its twisted nasty nature. This Cub can fly knife edge and I can slip it all the way to landing. So it can fly in an uncoordinated fashion no problem as long as the angle-of-attack on the wing is low. But..... Just pull back on elevator stick during a slip at altitude and it is snap roll time. My other models are more forgiving, but this J3 has taught me a new criteria for checking out a model's stability.
Update: Have reduced the elevator throw to half of what it was and the plane is a much more predictable now. Using only 1/4 inch up and 1/2 inch down (for inverted snap rolls), 40% exponential, and it now only snaps when I want it to. I also got rid of the long balsa push rod on the elevator as there was too much play at the control surface and put a servo right at the tail with a 4 inch rod for connection. The improvement in speed control during approaches has been dramatic.
A Cub has large control surfaces at the tail and not much movement is needed for large pitch and yaw changes. I think I had it set up with too much control throw initially and that accentuated problems with the twist in the fuselage.