Forces and Propeller Thrust

Owned by Henry Zhou
2021-06-06
1 min read

Forces acting on an airplane at cruising speed.

Excuse my extremly shitty sketch

Derivation of the cruising drag given a fixed wing area:

  • D is drag

  • CD is drag coefficient

  • CL is takeoff coefficient

All units in metric.

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/