Firtst, lets decide what we are actually discussing --- it started as a general query about thrust angles. That requires a generalized, but technically correct "quickie" answer, specific to model airplanes. 2Slow, Khodges & JohnW took a bite at that, but included some dubious concepts -- lets fix that before proceeding to the more esoteric aspects of the general question.

2) We can address the specific forces driving an uncommanded left turn (P-factor, torque, etc) -- but we need bounding conditions.

a. During take-off roll up to rotation

b. Climb-out & normal flight regimes

3) We can discuss/argue the validity of the spiral slipstream theory

I suggest that MajorTomski leads the discussion (that way the rest of us can keep our powder dry 'till we see the whites of his eyes).

This should be very instructive to the newbs, as well as to the rest of us.

Anyone agree?

OK, so much for that -- who dissagrees?