ORIGINAL: gaRCfield
I borrowed an incidence meter and found that my rear stabilize has between 1.5 and 2 degrees of 'up' built into it; the wings are close to 0, and the engine is about 1.5 degrees down (supposed to be 2 degrees).
What should I change? The plane likes to fly UP, and uses lots of down trim to fly straight. I know I can add a washer under the top of the engine mount to add more down thrust, but not sure (haven't thought too hard about yet) how this would affect everything else. Obviously I can't change the incidence of the elevator as it's epoxied in place. The tail was able to be repaired with minimal amounts of CA and epoxy, so it's not going to be removed.
Thanks.
What you're talking about, incidences, are values that are absolutely not important by themselves. They are important, but in relationship to other things. And you've not mentioned any of those important other things.
For example, the incidence of a cambered wing will quite naturally be different than a symmetrical wing. And a highwing airplane's stabilizer will usually have a different incidence than a low wing airplane's stabilizer. And the airfoil of the wing would have an affect on the stabilizer as well.
Also, what do you mean by the tail having "up built into it"? Do you mean it is angled down in front or angled up in front?
What the plane does should be good enough to work with. If you feel that it climbs when you wish it to fly level and that trimming the elevator with down trim gets it to fly the way you wish, work with that. Since you're not planning to change the stab's incidence, the change the wing's incidence. Raise the wing's TE some and test fly the airplane. Expect the elevator trim to be incorrect.
BTW, if you know that the engine is supposed to have more downthrust, then set it to whatever you know it should be and test fly. You'll learn right away if that engine thrust line mattered. And all it took was slapping some washers in place.
What is the airplane?