otrcman

It's never going to be as easy as a nosewheel, but maybe a better understanding of the physics of a ground loop will help you overcome the problem.

First, the fact that the airplane goes left at low speed is no coincidence. What you are seeing is not really so much motor torque as it is gyroscopic precession. Precession sounds like a mouthful, but what it really means is that the spinning prop is a giant gyroscope. When the tail comes up, the prop feels like something is pushing forward at the top of the disc. But precession means that the gyroscope reacts as if it were being acted upon 90 degrees later in the rotation path. In other words, you push at the top of the disc, but the disc reacts as if you had pushed on the right side of the disc (right as seen from the pilot's seat). So the rapid rise of the tail becomes a strong push on the right side of the prop disc, making the airplane go strongly to the left. Since the model is very slow when the tail comes up, the rudder effectiveness isn't as strong as the gyroscope.

The thing to take away from this gyro business is the understanding that you need a major quick rudder input while the tail is coming up. If you wait to correct when you see the nose heading left, the harm has already been done. Learn to poke in a healthy dose of right rudder at the moment that the tail begins to rise. When I say, "poke", what this means is that you don't simply put in some right rudder and hold it. You need to put in far more rudder that you might think, and then get right back off it even before you see the plane respond. Just one big, quick poke, let go, and see how it's going. If the plane is still swinging to the left, poke the right rudder again. But don't push and hold the rudder. You will get out of phase with the action and wind up looping to the right. Notice what Charlie P. said about the P-40: "Pumping to full deflection repeatedly as necessary."

Another thing that will work in your favor is to change from a plastic propellor to a wooden. Remember, the prop is a spinning gyroscope. If you make the gyroscope lighter (wood prop instead of plastic), the precession torque will be reduced. This is very apparent on full scale airplanes if you fly the same airplane with a wood prop and then a metal prop. The wood prop airplane will seem like a ***** cat after flying the metal prop version.

Another trick is to slow down the rate at which the tail rises. If you apply and hold just a tiny bit of up-elevator before advancing the throttle, the tail will come up a little later and won't come up as quickly. The slower tail rise will reduce precession torque. I usually sort of lock my thumb on the elevator stick with 5% to 10% up elevator and hold it there until I break ground. Unless your model is overly sensitive to elevator, there won't be any danger of stalling with that small elevator input.

You mentioned using a heading hold gyro as a last resort. That's not a bad idea, although it's not necessary to use heading hold mode. I've experimented with a gyro in simple rate mode and found that it tames the model significantly. Better yet, get one of the 3-axis gyros such as the Eagle A3. Having rate damping on the elevator as well as rudder slows down the rate at which the tail comes up. Remember precession ? Slowing down the rate of rise of the tail reduces precession and makes it that much easier for the yaw channel of the gyro to control the left pull. Putting a gyro on yaw or pitch alone will make your job easier. Putting a gyro on both axes makes takeoffs duck soup.

Dick