Electric free flight propeller

Using the right propeller for electric free flight

By James Packwood

I am working on a Guillow’s project converting a Nakajima Rufe from a rubber motor free flight into an electric free flight using a free flight timer to control the motor run time and realized the importance of having the proper propeller when I mounted the wrong prop onto my E-flight Park 180. It was obvious on my bench test that I was using the wrong prop. The startup was rough, it had a heavy vibration and I could only get a 45 second run time off of a Lipo 2s 7.v 120 mAh battery (Not Good). The motor specs required a GWS 5x3 prop, I had mounted a 5.1x4.5E prop. After I mounted the proper propeller the difference was like night and day. Now the startup was smooth, no excessive vibration and I could now get 5 to 7 30 second flights out of my battery. You should always make sure that your propellers are properly balanced prior to installing them on your motor. I don’t think I have ever purchased one that did not need adjusting. Here are some tips.

Where to find the motor specs to get the right propeller.
• Look for the spec sheet that comes with your motor. It should tell you the best prop   will be for your motor.
• If you purchased your motor from a local hobby store, then they should be able to     get you the correct prop.
• You can always check the manufactures website. The will always have the proper     specs. (especially if the local hobby shop made a mistake or were not very helpful).
• Push comes to shove just google the make and model number of your motor. Look    for websites that also sell the motor that you have. 99.9% of the time they will            always have the specs.

Hazards of running the wrong prop.
• Excessive strain and vibration which will reduce the life of your motor.
• High motor temp.
• Motor will most like not produce the full RPM
• Reduced battery life caused by the motor straining to run a prop that may be too        heavy.

Happy Building 

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