Hey Jim,

Pulling tight corners is something that is a lot easier with a Contra Drive. In fact, there are two tight corners in the current masters pattern where I am finding the Contra to be very helpful. There is the half triangle with four point roll, and the 45 degree upline with 2 of 4 followed by a 180 degree loop and a 45 degree downline with a half roll. In both maneuvers the Contra tracks through the corners like it's on rails, and it doesn't matter if you push or pull with the last maneuver. It tracks exactly trhe same.

In my view, one of the things that happens with single prop setups is that the trim becomes "speed sensitive", which makes sense if you think about what's happening. This is because when the plane is flying fast, air is accelerated less at it goes through the prop disk than when the plane is travelling slowly. The biggest effects are when you accelerate during takeoff and climb out because you are flying with maximum power and slow speed. These effects are also very noticeable at the end of long vertical climbs because you are also flying slowly, and with maximum power.

The smallest effects are when you are flying without throttle, like on a downline, because you are flying with zero power, or even negative power if you are using ESC braking. In between these two extremes you get a whole range of effects that change as the airspeed and power of the plane change. What the Contra does is make the trim of the plane the same under all these different conditions, even braking.

Obviously, this makes it a lot easier to dial the trim of a plane in, and it also eliminates all the tradeoffs associated with using large diameter props. This means that with a Contra we can successfully run a pair of 22 inch diameter props, and take advantage of the tractor like vertical thrust and huge braking power that you get with large props. I did some calculations, and I figure that a pair of 22 inch props is about equivalent to a 30 in diameter single prop setup, but no one in their right mind would consider using a 30 inch diameter prop because all of the torque and slipstream effects would probably make the plane unflyable.

An additional benefit of running with a pair of 22 inch diameter props is that larger diameter props are inherently more efficient due to the reduced power loading per square inch of prop disk area. I am calculating that a pair of 22 inch props are from 15% to 20% more efficient than a 21 inch single prop setup.

However, none of this means that you still don't have to "fly the plane". You still have to put the plane where it needs to be, and you still need to correct for wind, so none of the aforementioned is a substitute for pilot skill. What the Contra Drive does do however, is make pattern much more enjoyable to fly. I liken it to racing with Toyota Prius, and then switching to a Ferrari. The Ferrari is much more pleasurable because it is better suited to the task.

I know that in my case I would find it very difficult to switch back to a single prop setup. First off, the change itself would be a shock because now I am aclimated to flying with a Contra. Then I would notice that my vertical performance sucks because the plane keeps slowing down on vertical climbs, and then zooming on vertical downlines. It would also seem to squirt all over the sky at the top of humpty bumps, or any large maneuver where the plane slows down a lot. It would also be very frustrating when I tried to do stall turns, because the wings would keep twisting out of the plane of rotation. Also, snaps would be an endless source of frustration because the plane would never snap the same when snapping in opposite directions.