Forces and Propeller Thrust

Forces acting on an airplane at cruising speed.

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Derivation of the cruising drag given a fixed wing area:

• D is drag

• C_D is drag coefficient

• C_L is takeoff coefficient

All units in metric.

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The force generated by the propeller must be at least 8.27 N. Probably more, from the drag of the fuselage and so such. Using this data of a 15x4E propeller it is found that:

• 8000-9000 rpm for cruising speed of 10m/s=22mph

• 350W output at cruising, 411 W at takeoff

  • 25A cruising with 14.4V battery.

This is a useful tool for motor curves: http://www.drivecalc.de/

Prop performance data: https://www.apcprop.com/technical-information/performance-data/