THIS next bit has nothing to do with answering SaCCaL72's original question

Now, where I started to muddy the waters is when I went off on my own personal crusade against the slipstream spiral theory that has been a SIGNIFICANT part of aviation, both full scale and model since the publication of the book Stick and Rudder

The author of this book first penned the theory that the wind off the propeller is spiraling around the fuselage, striking the vertical fin from the left side, causing a higher angle of attack on the right side, which results in a yaw to the left. In full-scale flight a pilot is required to demonstrate slow flight and a power on stall. In both cases the airplane is at a very high (relative to normal flight) angle of attack and at a very high power setting. Just before the airplane stalls, you have the right rudder peddle stomped as far down as it will go with all the force your leg can put behind it, deflecting full right rudder to overcome the strength of this supposed spiraling air around the fuselage.

Here is where my own crusade against this theory kicks in. This spiral is always illustrated in a side view of the fuselage and the vertical fin. No one ever stops to think of what it is doing to the rest of the plane. If it is taking all my right foot force to hold a heading with the rudder due to a higher angle of attack on the fin. Why am I NOT holding a bunch of aileron to counter the now differential angle of attack over the wings and horizontal stabilizers? Because if the spiral is creating all this force on the fin and rudder should it not also be creating that much more force on both sides of the stab and wing? Which should be a very strong roll to the RIGHT, not left, as the airplane always wants to go.

I came to the conclusion that spiraling slipstream is a myth because it is the only aircraft stability function that is not quantified. Designing the aerodynamics of an airplane is a cookbook plug and crank set of mathematical operations. Take a set of interactive equations. Plug in a bunch of numbers, and it cranks out the answers of area and angle of attack for all of the flight controls. The one thing missing in all those equations is the mathematical definition of the slipstream and how much the fin should be offset to fix it.

And as shown in the photo in post #20 above, when you can see these spirals off the prop, they are going the wrong way to support the myth.

So what’s the answer? My personal theory, and I haven’t fully cooked it up yet, is that the airflow doesn’t spiral around the fuselage. But rather at high angles of attack and high power settings, due to the differential thrust called P factor, it is simply moving faster down the right side of the fuselage. This too creates a higher AOA on the fin and rudder and causes left yaw. But it also causes locally higher lift on the right wing and horizontal stab, which causes left roll, what the airplane actually does.

Again I most humbly apologize if I have offended any of you. Offending any of you was never my intent. I simply get a little too carried away in my outlook on aeronautical definitions.

By the way 2slow2matter, when I teach folks to fly RC it is the KISS principle. I only teach the mechanical aspects of how to do what with the controls to get the airplane to do what you want it to do. Never, ever, do I get into a discussion of aerodynamics or why, to avoid getting into this kind round-and-round discussions.

Thank you all for a chance to share.

SaCCal72, did you get an answer?

T