Question, I built my plane and the incidences were checked out and were not off, however flight required some up trim, so the elevator is not centred with the stab.
This is so at both nose and tail heavy setting on the plane.

Does this imply that an incidence could be out somehow and if it was corrected the elevator could be set so that it would be centered with the stab ?

Thanks,

L

I take it that the amount of up-trim is not excessive - like it is no more than about 1/8"?

If so, about the only thing that I would check, and I would think twice before adjusting, is that the CG is in the right "place". Sounds as though it might toward the forward end of the recommended range.

If you need more up-trim than that, then I would certainly be wanting to check the CG, and perhaps remove just a bit of the weight out of the front.

Here's the NSRCA trim chart. Gives a lot of trim information that may help.
http://www.nsrca.org/trimA.htm

Well, elevator trim and decalage are two ways of doing the same thing. If you want level flight with your elevator trimmed level with your stab, you can do that by (a) moving your cg back or (b) changing the decalage between wing & stab. Changing the decalage can be accomplished by lowering the TE of the wing, or lowering the LE of the stab. If neither of these is easily accomplished, then moving CG would be the way to go. Another point in favor of the CG solution is that elevator trim & decalage change will give varying effect with varying speed, whereas CG change will be more speed neutral. Consider also that as the tank empties, if the tank is not on CG, your CG will move back as fuel is drawn from the tank.

It is not unheard of for kit & plan CG recommendations to be off--sometimes a little, sometimes a lot. Most kitters like to err on the safe side and recommend a nose-heavy CG setting, expecting the modeler to make adjustments to suit their flying style.

Also follow the trim guide listed above by Mike and flight check for correct engine down thrust.

Alan