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Old 05-28-2014, 09:18 PM
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OhD
 
Join Date: Oct 2002
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Originally Posted by speedracerntrixie
Joe, if it were me I would set the motor to zero and adjust the CG until the up trim is gone then start trimming all over. For the past few years I have been setting up my aerobatic models this way and usually am pretty darned close from the bench. I will also adjust engine thrust to correct up lines only and never to correct horizontal flight issues.
I agree you need to get it flying with no trim in horizontal flight. I had been chasing the same problem on my Axiome + and found it was a cg problem. I found a program on the Internet that would let me calculate the MAC of a four panel wing. The Axiome + can be approximated with four panels and the results showed the cg had to be much further back than where I had it. What was really interesting was the fact that the mean aerodynamic chord was not an actual chord on the wing but was shorter than the actual chord at the specified distance from the centerline. You could also calculate the neutral point of the plane which takes into account the horizontal stab but you need to know if the horizontal stab is efficient on your model. I never found a way to determine this, but I'm sure someone knows.

Jim O