PROP FOR SCALE
For years, I have been catching a lot of guff over my propeller selections. As I said before, creating the illusion of scale flight speeds can be a lot of work, so I want the plane to do as much as possible. As in other forms of RC competition, such as aerobatics or pylon racing, prop selection is very important if you want your beauty to act correctly. The list of recommended props from the engine manufacturers will provide good performance under most conditions, but I have found them to be a tad small for scale performance. I always try new things, but after a bunch of flying, I usually end up using a prop that’s one or two steps larger (in pitch, diameter, or both) than what was recommended. I normally over-prop so that I can get the airplane to react in ways that can’t be easily controlled with the sticks. In other words, bigger props tend to mellow out the reaction time of the throttle and the control-surface sensitivity. The big props also hold rpm down to about 5,300 to 6,000, which is plenty for providing the needed performance and does a good job of controlling sound levels. There’s nothing worse than a propeller that should be turning 3,000rpm turning 9,000rpm—and that’s at 100% power. If you’ve watched full-scale aircraft fly, you’ve probably noticed that nothing happens very quickly. Whether they’re in the air or on the ground, airplanes never make sharp jerky movements and there is a certain delay time. By using props that are too big, the model seems to acquire this delay time. I’ve never had a problem with the actual transition of throttle, but it slows down the transition time. This is very handy at takeoff, causing the model to require less rudder to compensate for P-factor and providing longer, slower takeoff runs that look more scale.
The same holds true for approach speeds and landing, where the big prop creates more drag at lower power settings to make speed control easier when it is most important. Don’t be afraid of lost performance with a big prop; of course, there will be a decrease in rpm, but the larger props create more thrust. It just takes longer for the plane to get up on step. Instead of rocketing off the runway in 10 feet, it will take a full lap to reach cruising speed. Be sure to check out my list of displacement and recommended prop sizes. It might be a little mind-blowing but at least give them a try. Keep in mind that, at first, your plane will probably feel sluggish, but I think you’ll like the difference when you get used to flying without the sharp edges. Your flight scores will show the positive effects as well.