Converting Glow to Brushless Electric Power

This brief video explains how to size a brushless electric power system for your model aircraft. While focused on glow size aircraft, the rules apply well to larger and smaller craft. For quick reference, remember the Four Ps:

- 100 to 150 watts/lbs for sport flying
- 200 watts/lbs for 3D
- Power = V*I (volts * current in amps)

- Nominally, lipo batteries are ~4volts per cell
- Keep all cells above 3.75 volts for long pack life
- Voltage * kV = motor no load RPM
- Brushless motors are most efficient at 80% of no load RPM.
- Quick estimate for size: mah = (max current / 15) * 1000
- Common packs: 3S 2100mah, 4S 3300 mah

Pitch Speed:
- At 10,500 RPM Pitch Speed (mph) = Pitch (inches) * 10
- (80% no load RPM / 10,500) * 10 * Pitch ~ Pitch Speed (mph)
- 50 mph and under are slow fliers
- 60 to 80 mph typical for sport fliers

- Diameter / Pitch < 1.5 can stall at low speeds – D/P > 1.5 more thrust at take off, less torque roll
- D/P = 2.0 or higher for 3D

- Confirm static current draw with a power meter
- Consider a seperate BEC or receiver battery over 500 watts
- Consider arming switch for systems over 500 watts
- Never reach through prop circle to arm or disarm battery

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