Engineering Specs

The Constraints

Constraints: 2 minute mission plus 20 W-hr energy maximum equals 600 watts and 40.5 amps continuous propulsive system minimum

If using a 4S LiPo with a nominal voltage of 14.8 V,

Current equals power divided by voltage: 1000 divided by 14.8 equals 67.5 amps

Power and current minimum requirements influence every design choice in the propulsion system.

Propeller: 6×7 folding propeller

To minimize drag in the glide portion of the mission, a folding propeller is utilized. Whenever the motor is turned on, the rotational motion keeps it extended and producing thrust, but once the motor stops, the propeller stops rotating and folds back.

After analysis, the range of optimal pitch over diameter (PoD) ratios for the specified motor is from 0.875 to 1.25.

Pitch versus total score chart for the BadAss 2320-1630 motor

Optimizing the propeller to get just over two minutes of full-throttle endurance involved in-flight testing, starting with an 8×7 (PoD = 0.875) and then trimming it down until we get the full endurance. A 6×7 (PoD = 1.17) propeller can achieve full endurance while still maintaining high speeds.

Motor — BA2320-1630 Kv

Monarch was optimized and designed to operate with five BadAss motors, with each one being capable of producing optimal performance.

BA2310-2350
BA2315-1800
BA2315-2300
BA2320-1310
BA2320-1630

The BA2320-1630 was selected after flight testing.

Battery — 4S 1300 mAh

To maximize the energy capacity in the battery, a few different combinations can be utilized.

4S 1350 mAh (19.98 W-hr)
3S 1800 mAh (20 W-hr)
2S 2600 mAh (19.24 W-hr)

Upon initial analysis, a 4S battery gives the highest theoretical score output.

Chart comparing battery cell configurations versus score

ESC — 65 amp

To achieve servo torque required for tight and controlled turns, the BEC needs to output 8.4 volts.

This limits the options for suitable ESCs, as many do not have this option. The BA renegade 65 amp was ultimately chosen for its seamless integration with the BA motor, as well as its heat dissipation ability and BEC output voltage of 8.4 volts.

Troubleshooting

When something inevitably malfunctions, reference the wiring diagram below to better understand what could be causing the issue.

Internal propulsion component layout in the fuselage

Electric propulsion cutaway view of the aircraft nose

Part	Name	Link
ESC	BadAss Renegade V2 65A	BadAss Renegade V2 Series Brushless ESC, 65A
Motor	BadAss 2320-1630 Kv	BadAss 2320-1630 Kv Brushless Motor
Battery	Tattu 1300 mAh 4S LiPo	Tattu R-Line Version 5.0 1300 mAh 4S 14.8 V 150C LiPo Battery — XT60
Propeller	Aeronaut CAM 8×7 folding propeller trimmed to a 6×7	Aeronaut CAM folding propellers
Spinner	BB Turbo Spinner 36×4×8	BB aluminum spinners turbo for folding propellers
Voltage and current sensor	Jeti 50A MUI EX	Jeti telemetry sensor — current, voltage, capacity MUI EX
Speed sensor	Jeti MSpeed EX	Jeti telemetry sensor — airspeed MSpeed EX
Receiver	Jeti Duplex EX R7 REX Assist	Jeti Duplex EX R7 REX Assist 2.4 GHz receiver

	MathCad	CFD
SM_p	22%	19%
C_nβ	0.074	0.076
C_m,α=0	−2°	−3°

Wing Span: 39 in.

Wing Area: 180 sq. in.

Taper: 0.85

Sweep: −0.55 degrees