I have 2 models, same plane from the same manufacturer.

only major difference is powerplants......but same diameter prop and pitch

in a knife edge, both models do a nice knife edge flying from right to left...however one flies well from left to right, and the other tucks towards the belly.

not sure what difference I'm dealing with........

both are balanced with Great Planes balancer, at same point

measures with incidence meter, nothing I can pin down, but thats not the first time I could not find a difference with the meter that effected the flight charactoristics of a model....

I'm open for thoughts and suggestions

thanks

Are your pushrods flexing? Rudders with pushrods will always knifedge better on the side they pull, not so well on the side they push.

Is your fin/rudder square & straight on the offending model?

two great points to consider

the offending model has carbon fibre pushrods, and was built tighter than the better flying model, and the rods are supported in both planes....

the better flying model has about 200 flights on it and the new one about 25

the rudder seems to be centered, I haven't put a straight edge on it recently, but would suspect that a carefuel second check is in order and check the centerv line reference to the offset in the motor as well..

this will be done tonight

thanks

bob

See if the elevator halves are exactly alligned. Sometimes the"top" elevator is blanked in K E, so the plane will pitch differently depending on which side it's flying.

could be a balance issue with the airplane, left to right, front to back. It ould also be the wing alignment, engine thrust angles. The list goes on and on..

I would be tempted to simply increase the rudder area - this always helps my knife-edge - and make sure that the rudder throw is 45 degrees, or more, each way - and put as much rudder area as possible in the propwash by using a subrudder and subfin. I find that servos frequently have slightly unequal travel; left versus right, and have to correct by offsetting the servo output arm a few degrees.

I recently increased the rudder area of my old faithful fully aerobatic original design bipe by 50. Knife-edge improved considerably, to the point where it will now glide with its nose level in knife-edge, power off, but it has very wide chord, airfoiled "cheater" interplane struts covered with clear Monokote, which help a lot, and they also improve overall handling close to stall by boosting yaw resistance. Now does much sharper knife-edge square loops.