Hi Adam,

I've been meaning to continue your discussion but have been super busy. A long time ago someone asserted that stab incidence was not critical and I had a big problem with that. It was pointed out that all the stab did was set the wing at the proper angle of attack. It kind of made sense. I countered with the fact you would get trim drag if the elevators didn't trim to exact neutral and was told it is insignificant.
Now some recent experience. My Impact required uptrim to fly level and went to the canopy on vertical lines. I started adding positive incidence to the wing which required less uptrim in the elevator. It had the effect of adding downthrust and it made the tail fly higher. After a number of cut and tries the plane goes straight up and down and is flying with a tiny bit of downtrim. A purist would adjust the stab slightly but the downtrim is almost imperceptable so I won't mess with it.

I am now thinking of going back and working on my Composite-Arf Extra which never did good vertical lines. On it, I will adjust the thrust line as it is difficult to change the wing incidence.

Jim O