Flyer 101. Your entire reasoning dismissing p-factor is based on a faulty premise:
That a prop mounted in line with and aft of the wing, will encounter the air at the same angle as a prop conventionally mounted on the forward fuselage ahead of the wing, given the same conditions of pitch attitude, climb angle and prop shaft axis mounting angle.
That, as I said, is a badly flawed premise and completely negates the conclusions you've drawn. Here's why:
On a conventional airplane, if we assume that the disturbance of airflow ahead of the physical airplane is negligible *, the angle at which the prop encounters the airflow is going to be quite simply the attitude angle - the climb angle +/- the angle of the prop shaft to the longitudinal axis on the airplane. We're speaking of the angle of the airflow relative to the spin axis of the propeller, not the effective angle of attack of the prop blades, just the angle the air flows thru the prop disc.
The same is *not* true of an airplane with the prop mounted in line with and behind the wing, as in the photo you linked. On such a plane the prop is *not* encountering undisturbed, or minimally disturbed airflow. It is right in the air flowing off the training edge of the wing. And whatever your favorite explanation for how a wing generates lift, what is *not* in question is that the wing deflects air downward. So, if the axis of the prop is aligned with the chord of the wing, it will encounter descending air when the wing is generating lift. If it is aligned with the longitudinal axis of the aircraft, the air flowing thru it will be descending to an even greater degree. It appears from the picture (and common sense would seem to suggest) that the latter is the case rather then the former. In any case, the airflow thru the prop will be descending, relative to the rotational axis of the prop. Which is the opposite of the angle of airflow thru a conventionally mounted prop. Which according to the theory of P-factor, would predict that for a prop turning clockwise when viewed from behind, the p-factor would produce a *right* turning tendancy. Which is exactly what you report. QED.
There is one comment of yours which warrants a specific response:
Originally Posted by
flyer101flyer
PS near the end of section 8.5.2 of the same source, we read that the yaw effect of P-factor is SMALL compared to the yaw effect from the spiralling slipstream striking the vertical fin:
*8**Yaw-Wise Torque Budget
Yes. We read that. The thing is, it is a completely unsupported assertion. The author just claims that it is true, without offering a shred of empirical evidence, anecdotal evidence, theoretical reasoning, or any suggestion of how he has concluded that is true, just that he states that it is true, and he expects it to be accepted as true because he states it is. Now it may be that he has what he believes are compelling reasons for stating that, but if he doesn't say what those reasons are, his claim has exactly zero value. He could have claimed with equal validity that left turning force was caused by gyroscopic precession or aliens.
* Objects moving through a fluid affect the fluid farther ahead of the object that many realize. Watch a video of an airfoil in a wind tunnel with smoke streams. When the airfoil is generating lift, the smoke streams are deflected upward well ahead of the airfoil. And yes, fluid is correct. At 172 speeds the air is a fluid, for all practical purposes. Many people visualize air as compressing as it flows around and airfoil. At those airspeeds (it's actually related to mach number, which isn't exactly airspeed, but we're drifting way off topic) it doesn't compress or squeeze or change density any significant amount, so it's acting as a fluid.