<font size="2">Loop trim:

Straight and level, medium power.
Pull up and do three reasonable tight loops in succession. Do not add any corrections.
If the plane tracks well but drops a wing then it is heavy on that side and you need to add a balance weight to the other wing tip.
If the plane tries to corkscrew ie each loop is progressively further left (or right) than the other one then you have a aileron that is not in alignment to the wing. If the plane tracks left then the leading edge of the left aileron is either high or low in relation to the trailing edge of the wing and is causing the plane to skew to that side. You need to correct the aileron alignment. </font>


I got this from another post a while back, and kept it for myself.