BTT-Jon:

You are perfectly correct on the circular flow of the slip stream. And that's why it is not uncommon on a single engine prop plane to find the leading edge of the vertical fin offset to the left.

This effect also is greatest immediately after take-off, while on the ground plain old "Ground Effect" neutralizes it somewhat, and during acceleration with the tail still low p-factor is of much greater effect.

In the air, as the plane approaches pitch speed, the effect diminishes, Also, with a longer tail moment arm there is less effect from the spiral flow, as it tends to straighten in proportion to the distance from the propellor.

But torque is always with us, so long as you are feeding power to the propellor.

The note on p-factor above is a copy of one post in a series I did on basic design considerations, someday I'll go back and finish it. The series starts with the third post here:

http://www.rcuniverse.com/forum/Wher...1063414/tm.htm

I invite yoour reading the series, and yoour comments.

Bill.