Prop Charts For Model Airplane Engines

Prop Chart For Two – Stroke Engines

Alternate Propellors	Starting Prop	Engine Size
5.25×4, 5.5×4, 6×3.5, 6×4, 7×3	6×3	.049
7×3,7×4.5,7×5	7×4	.09
8×5,8×6,9×4	8×4	.15
8×5,8×6,9×5	9×4	.19 – .25
9×7,9.5×6,10×5	9×6	.20 – .30
9×7,10×5,11×4	10×6	.35 – .36
9×8, 11×5	10×6	.40
10×6,11×5,11×6,12×4	10×7	.45
10×8,11×7,12×4,12×5	11×6	.50
11×7.5, 11×7.75, 11×8,12×6	11×7	.60 – .61
11×8,12×8,13×6,14×4	12×6	.70
12×8,14×4,14×5	13×6	.78 – .80
13×8,15×6,16×5	14×6	.90 – .91
15×8,18×5	16×6	1.08
16×10,18×5,18×6	16×8	1.20
18×8,20×6	18×6	1.50
18×10,20×6,20×8,22×6	18×8	1.80
18×10,20×6,20×10,22×6	20×8	2.00

Prop Chart For Four – Stroke Engines

Alternate Propellers	Starting Prop	Engine Size
9×5,10×5	9×6	.20 – .21
10×6,10×7,11×4,11×5.11×7,11×7.5,12×4,12×5	11×6	.40
10×6,10×7,10×8,11×7,11×7.5,12×4,12×5,12×6	11×6	.45 – .48
11×7.5,11×7.75,11×8,12×8,13×5,13×6,14×5,14×6	12×6	.60 – .65
12×8,13×8,14×4,14×6	13×6	.80
13×6,14×8,15×6,16×6	14×6	.90
14×8,15×6,15×8,16×8,17×6,18×5,18×6	16×6	1.20
15×6,15×8,16×8,18×6,18×8,20×6	18×6	1.60
18×12,20×8,20×10	18×10	2.40
18×10,18×12,20×10	20×8	2.70
18×12,20×10	20×10	3.00

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Starting Propellor sizes are mid range pitch props that should fly just about any plane designed for that size engine. Use these first as in most cases they will be close to being the correct size. Then use trial and error to try and fine tune the maximum performance from your ship by trying the alternate props. If none work better stick with the recommended starting prop.

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Below are some safety items that although seem elementary still need to be repeated regarding propellers and their use.

• Install the prop with the curved side of the blade facing forward and tighten the prop nut or bolt with the proper size wrench.
• Recheck the tightness of the nut or bolt often, especially on wood props which tend to compress and loosen more often.
• When starting the engine, keep spectators at least 20 feet clear of the model and out of the path of the propeller.
• Keep hands away from the prop as much as possible. Use a chicken stick or and electric starter.
• Keep face and body out of prop arc as engine is started and run.
• Make all adjustments from behind the prop except on pusher prop installations.
• Never throw anything into the prop to stop the engine. Use a kill switch or pinch off the engine’s fuel supply.
• Discard any prop with nicks, scratches, splits, cracks or any other sign of damage. Never attempt to repair, alter or bend a prop.
• Don’t run an engine in areas of loose gravel or sand for the prop can throw such material into your face and eyes. It’s not a bad idea to wear eye protection.
• Keep loose clothing, shirt sleeves, and other such items away from the prop and avoid carrying objects that can fall into the prop such as pens, screwdrivers, etc.
• Be sure to keep the glow driver wire out of the prop path.
• If a spinner is used, be certain that it’s edges are not in contact with the propeller blades.