Cobra C4120/18 Motor Propeller Data
Motor Wind Motor Kv No-Load Current Motor Resistance I Max P Max (6S)
18-Turn Delta 540 RPM/Volt Io = 1.50 Amps @ 20v Rm = 0.030 Ohms 54 Amps 1200 W 
 
Outside Diameter Body Length Total Shaft Length Shaft Diameter Motor Weight
49.8 mm,  1.96 in. 51.8 mm,  2.04 in. 74.5 mm,  2.93 in. 6.00 mm,  0.236 in. 290 gm,   10.23 oz
 
Prop Prop Input Motor Watts Prop Pitch Thrust  Thrust Thrust Eff.
Manf. Size Voltage Amps Input RPM Speed Grams Ounces Grams/W
APC 12x10-E 14.8 24.76 366.4 6,959 65.9 1647 58.10 4.49
APC 12x12-E 14.8 29.55 437.4 6,776 77.0 1501 52.95 3.43
APC 13x8-E 14.8 24.25 358.9 6,881 52.1 2012 70.97 5.61
APC 13x10-E 14.8 33.82 500.5 6,620 62.7 1937 68.32 3.87
APC 14x7-E 14.8 28.64 423.9 6,817 45.2 2437 85.96 5.75
APC 14x8.5-E 14.8 30.79 455.6 6,737 54.2 2530 89.24 5.55
APC 14x10-E 14.8 30.36 449.4 6,753 63.9 2457 86.67 5.47
APC 14x12-E 14.8 44.88 664.3 6,227 70.8 2082 73.44 3.13
APC 15x6-E 14.8 30.36 449.3 6,758 38.4 2761 97.39 6.14
APC 15x8-E 14.8 32.27 477.6 6,680 50.6 2746 96.86 5.75
APC 15x10-E 14.8 44.74 662.2 6,228 59.0 2958 104.34 4.47
APC 16x8-E 14.8 47.86 708.3 6,141 46.5 3477 122.65 4.91
APC 16x10-E 14.8 52.27 773.5 5,971 56.5 3498 123.39 4.52
APC 17x8-E 14.8 51.73 765.6 5,959 45.1 3781 133.37 4.94
APC 18x8-E 14.8 52.23 773.0 5,869 44.5 4142 146.10 5.36
MAS 12x8x3 14.8 26.34 389.8 6,904 52.3 2192 77.32 5.62
MAS 13x8x3 14.8 29.16 431.6 6,793 51.5 2408 84.94 5.58
MAS 14x7x3 14.8 34.22 506.5 6,615 43.8 2851 100.57 5.63
MAS 14x9x3 14.8 40.78 603.5 6,371 54.3 3160 111.46 5.24
MAS 15x7x3 14.8 42.22 624.8 6,316 41.9 3352 118.24 5.36
MAS 16x8x3 14.8 48.07 711.5 6,093 46.2 3740 131.92 5.26
MAS 16x10x3 14.8 59.28 877.3 5,653 53.5 4080 143.92 4.65
 
Prop Prop Input Motor Watts Prop Pitch Thrust  Thrust Thrust Eff.
Manf. Size Voltage Amps Input RPM Speed Grams Ounces Grams/W
APC 11x8.5-E 18.5 26.06 482.0 8,768 70.6 1967 69.38 4.08
APC 11x10-E 18.5 30.76 569.0 8,574 81.2 1818 64.13 3.20
APC 12x8-E 18.5 30.92 572.0 8,564 64.9 2184 77.04 3.82
APC 12x10-E 18.5 37.64 696.4 8,295 78.6 2360 83.25 3.39
APC 12x12-E 18.5 41.78 772.9 8,129 92.4 2184 77.04 2.83
APC 13x6.5-E 18.5 34.61 640.4 8,418 51.8 2984 105.26 4.66
APC 13x8-E 18.5 37.61 695.7 8,306 62.9 2943 103.81 4.23
APC 13x10-E 18.5 50.23 929.3 7,797 73.8 2730 96.30 2.94
APC 14x7-E 18.5 43.62 807.0 8,061 53.4 3497 123.35 4.33
APC 14x8.5-E 18.5 44.81 829.0 8,012 64.5 3593 126.74 4.33
APC 14x10-E 18.5 44.84 829.5 8,011 75.9 3473 122.51 4.19
APC 14x12-E 18.5 64.32 1189.9 7,220 82.0 2833 99.93 2.38
APC 15x4-E 18.5 34.39 636.2 8,426 31.9 3534 124.66 5.55
APC 15x6-E 18.5 45.33 838.6 7,992 45.4 4004 141.24 4.77
APC 15x8-E 18.5 47.19 873.0 7,924 60.0 3923 138.38 4.49
MAS 11x8x3 18.5 25.80 477.2 8,779 66.5 2267 79.97 4.75
MAS 12x6x3 18.5 26.43 488.9 8,753 49.7 2502 88.25 5.12
MAS 12x8x3 18.5 37.46 693.1 8,305 62.9 3162 111.54 4.56
MAS 13x8x3 18.5 41.33 764.6 8,157 61.8 3497 123.35 4.57
MAS 14x7x3 18.5 48.12 890.3 7,877 52.2 4064 143.35 4.56
MAS 14x9x3 18.5 56.75 1049.9 7,530 64.2 4414 155.70 4.20
MAS 15x7x3 18.5 58.72 1086.3 7,433 49.3 4693 165.54 4.32
 
Prop Prop Input Motor Watts Prop Pitch Thrust  Thrust Thrust Eff.
Manf. Size Voltage Amps Input RPM Speed Grams Ounces Grams/W
APC 10x7-E 22.2 22.51 499.7 10,612 70.3 1923 67.83 3.85
APC 10x10-E 22.2 34.86 773.8 10,209 96.7 1849 65.22 2.39
APC 11x5.5-E 22.2 25.58 567.8 10,619 55.3 2565 90.48 4.52
APC 11x7-E 22.2 30.62 679.7 10,385 68.8 2740 96.65 4.03
APC 11x8-E 22.2 34.03 755.4 10,241 77.6 2571 90.69 3.40
APC 11x8.5-E 22.2 35.77 794.2 10,021 80.7 2591 91.39 3.26
APC 11x10-E 22.2 42.38 940.7 9,895 93.7 2440 86.07 2.59
APC 12x6-E 22.2 33.91 752.8 10,109 57.4 3223 113.69 4.28
APC 12x8-E 22.2 42.37 940.7 9,897 75.0 2944 103.85 3.13
APC 12x10-E 22.2 52.72 1170.3 9,491 89.9 3047 107.48 2.60
APC 12x12-E 22.2 55.74 1237.5 9,345 106.2 2877 101.48 2.32
APC 13x4-E 22.2 27.74 615.9 10,370 39.3 3156 111.32 5.12
APC 13x6.5-E 22.2 49.08 1089.5 9,617 59.2 3929 138.59 3.61
APC 13x8-E 22.2 53.08 1178.5 9,486 71.9 3917 138.17 3.32
APC 15x4-E 22.2 47.00 1043.3 9,542 36.1 4737 167.09 4.54
MAS 10x7x3 22.2 25.64 569.1 10,617 70.4 2457 86.67 4.32
MAS 11x7x3 22.2 31.32 695.4 10,358 68.7 2960 104.41 4.26
MAS 11x8x3 22.2 34.58 767.6 10,230 77.5 3034 107.02 3.95
MAS 12x6x3 22.2 35.68 792.0 10,177 57.8 3436 121.20 4.34
MAS 12x8x3 22.2 49.95 1108.8 9,594 72.7 4264 150.41 3.85
MAS 13x8x3 22.2 54.90 1218.7 9,374 71.0 4638 163.60 3.81
 
Prop Prop Input Motor Watts Prop Pitch Thrust  Thrust Thrust Eff.
Manf. Size Voltage Amps Input RPM Speed Grams Ounces Grams/W
APC 9x7.5-E 29.6 39.65 1173.6 13,563 96.3 2457 86.67 2.09
APC 9x9-E 29.6 41.53 1229.2 13,302 113.4 2452 86.49 1.99
APC 10x5-E 29.6 30.30 896.9 14,023 66.4 2845 100.35 3.17
APC 10x6-E 29.6 33.47 990.7 13,871 78.8 2935 103.53 2.96
APC 10x7-E 29.6 39.92 1181.7 13,557 89.9 3159 111.43 2.67
APC 11x5.5-E 29.6 45.97 1360.7 13,300 69.3 4078 143.85 3.00
APC 11x7-E 29.6 54.81 1622.4 12,886 85.4 4168 147.02 2.57
APC 13x4-E 29.6 51.53 1525.3 13,029 49.4 5324 187.80 3.49
MAS 9x7x3 29.6 31.01 917.8 13,991 92.7 3118 109.98 3.40
MAS 10x5x3 29.6 27.95 827.4 14,141 67.0 3200 112.88 3.87
MAS 10x7x3 29.6 41.29 1222.3 13,489 89.4 4043 142.61 3.31
MAS 11x7x3 29.6 48.70 1441.6 12,962 85.9 4670 164.73 3.24
MAS 11x8x3 29.6 56.28 1665.8 12,820 97.1 4716 166.35 2.83
Propeller Chart Color Code Explanation
   The prop is to small to get good performance from the motor. (Less than 50% power)
   The prop is sized right to get good power from the motor. (50 to 80% power)
   The prop can be used, but full throttle should be kept to short bursts. (80 to 100% power)
   The prop is too big for the motor and should not be used. (Over 100% power)
PLEASE NOTE: 
The data contained in this prop chart is based on actual measurements taken in a controlled test 
environment.  The test voltages used are based on a properly sized Li-Po battery for the current
draw of the motor being tested.  If you are using a larger than normal capacity battery, or a very
high C-Rated battery, your actual voltages will be higher than those shown in this chart, and this
will result in higer current draw for each prop used.  You should always test your power system
with a watt meter whenever a prop is used to ensure that you are not exceeding the recommended
rating of the motor being used.  The prop recommendations in this chart are based on the motor
receiving adequate cooling throughout its operation.  If your motor is being used inside a cowl, you
must provide adequate cooling to the motor and make sure that the motor is not getting too hot
during operation.