SELECTING A PROPELLER

 

The charts below are intended to give the beginner a starting point for best performance.  Modelers who have some experience develop a feel for the best size propeller for different model/engine combinations.

 

In general, engines want to operate at a particular RPM where they can reach max power.  Using too large a diameter and/or too high a pitch may cause the engine to not rev up to the best power band.  With too small a diameter and/or pitch, the engine will over-rev and not deliver the best thrust.  Often, heavy and slow airplanes use a large diameter and moderate pitch, while a fast plane will have a smaller diameter and a higher pitch.  Hovering and lifting applications use an over-sized, low-pitch propeller.

 

Use the charts below to select a propeller.  Check the RPM with a tachometer – RPM will increase from 1500 to 3000 in flight, depending on the weight and speed of the plane.   BE SURE TO FOLLOW ALL SAFETY AND WARNING INSTRUCTIONS. . . GOOD FLYIING!

One of the differences between wood and glass-filled nylon propellers is that glass-filled nylon props have suggested RPM limits for mechanical considerations.  This will vary according to diameter.  For Master Airscrew props, we suggest the following formula:

 

RPM Operating Limit = 165,000 divided by Diameter in Inches.  For example, a 10” diameter prop has an operating limit of 16,500 RPM, well above the requirement of a .40 engine.