Baron:

I should have responded to you also. You have a valid point, but I always try to have enough sub fin or low rudder area that the effect of the toroid flow is minimized. And full scale designers often do it too. Look at the rudder of a Cap - the ugly shape is just for that reason.

And many GA planes (full scale) have the leading edge of the vertical fin offset to the left, again for the same reason.

But when I'm scratching a design I automatically center all empennage areas as much as I can, and I usually forget the spiral flow of the slip stream when I talk about thrust lines.

So thanks for pulling me up short, I needed it.

Randall:

No professional association since I got out of the USAF. Since then I've been building, flying, crashing, and hopefully, learning. Both books and practical, models and full scale.

Bill.