On the topic of Prop Balancing, here is an inexpensive way to get a smoother running engine. It was submitted by Ben Favrholdt, N66MX, of Porterville, California. Note that he is talking about his wood propeller.

• Cut a piece of aluminum, making a disk about 3 inches wide and 6 inches long. Glue a suction cup on one side of the disk. You can use one from Aircraft Spruce, P/N 13-00088 at $2.95. See photo below.
• Next, attach a spring steel reed at the top end of the disk. A coping saw blade will probably work okay. Attach an adjustable weight on the reed.
• Mount the assembly by suction to the face of one of the instruments on the panel.
• In flight, you will see a deflection of the reed due to normal vibration. By experimenting with different RPM's and weight positions on the reed, you should be able to find a combination where there will be harmonic resonance, where the reed will deflect to a much greater extent. Note these settings.
• Now paint the outer two or three inches of one blade of the propeller. Obviously, if the deflections are now greater than before, you painted the heavier side of the prop. Now work on the other blade until you get minimum deflection.
• It seems simple, but it works. I used a spray can to paint, and doesn't take much paint since there is a long arm and requires little weight to have an effect.
• I don't know if this will work on a metal prop because of the larger mass.

18 November, 2002