Very fair question. And the answer is that any number of good builders will produce the same model that flies virtually identical every time when building from the same kit. I have seen the pitch couple mentioned numerous places related to a number of different kits and/or plans of the Cap. And the root cause of a pitch towards the belly on KE flight is that the stab is too high relative to the fuse and/or thrust line (I'm not sure which, exactly, and they are intertwined somewhat) and needs to be lowered. On many pattern planes, adjustable wings and stabs mean that you can trim the plane with different incidence settings to make the tail fly higher or lower in level flight, essentially moving the stab up or down relative to thrust and achieve the neutral KE performance I want. Go through a trim chart to set up a good aerobatic design and you will find that they are very sensitive to changes and a different stab location will make a very noticeable difference in KE pitch coupling. Moving the CofG 1/2" makes a detectable difference in pitch coupling and inverted behavior as well. So if Eric says it improved his models, I don't doubt that it did.

The differences between airframes you ask about are real, since no one can exactly duplicate another airframe, but those differences are small between good builders. If you had Eric build one and Dick Hanson build another, one might need 4% mix to trim out a couple and the other 6%. But it won't be 2% and 20%, which is what we are talking about by relocating the stab.


Mark