Propeller Installation & Safety Measures
It’s easy to overlook safety concerns when we’re eager to install new props and take to the air. Most of these are good common sense routines, but there’s no harm in repeating them.

ALWAYS install the propeller with the curved side facing forward
ALWAYS use the correct sized wrench to tighten the bolts or nuts
ALWAYS recheck the bolt or nut’s tightness, especially with wooden props
ALWAYS test the new props AT LEAST 20ft. away from onlookers
ALWAYS keep hands well clear of spinning props
ALWAYS keep faced & body clear of the prop’s arc after starting the engine/motor
ALWAYS make fine adjustments from behind the prop (except pusher props)
ALWAYS keep loose clothing well clear from spinning propellers
NEVER throw something into the path of spinning props to kill the engine
ALWAYS discard damaged props. NEVER attempt to repair
ALWAYS test new props well away from loose gravel and sand
ALWAYS keep the glow driver wire away from the prop’s path
Accidents happen all the time, yet RC mishaps are avoidable with a little foresight. Try not to let excitement and enthusiasm make you impatient or rush you along.

PROPELLER  2-STROKE ENGINES
Engine Size Starting Prop Alternate Propellers
.049 6-3 5.25-4, 5.5-4, 6-3, 6-4, 7-3
.09 7-4 7-3, 7-4, 7-5
.15 8-4 8-5, 8-6, 9-4
.19 – .25 9-4 8-5, 8-6, 9-5
.29 – .30 9-6 9-7, 9.5-6, 10-5
.35 – .36 10-6 9-7, 10-5, 11-4
.40 10-6 9-8, 11-5
.45 10-7 10-6, 11-5, 11-6, 12-4
.50 11-6 10-8, 11-7, 12-4, 12-5
.60 – .61 11-7 11-7.5, 11-7.75, 11-8, 12-6
.70 12-6 11-8, 12-8, 13-6, 14-4
.78 – .80 13-6 12-8, 14-4, 14-5
.90 – .91 14-6 13-8, 15-6, 16-5
1.08 16-6 15-8, 18-5
1.2 16-8 16-10, 18-5, 18-6
1.5 18-6 18-8, 20-6
1.8 18-8 18-10, 20-6, 20-8, 22-6
2.0 20-8 18-10, 20-6, 20-10, 22-6

PROPELLER FOR 4-STROKE ENGINES
Engine Size Starting Prop Alternate Propellers
.20 – .21 9-6 9-5, 10-5
.40 11-6 10-6, 10-7, 11-4, 11-5, 11-7, 11-7.5, 12-4, 12-5
.45 – .48 11-6 10-6, 10-7, 10-8, 11-7, 11-7.5, 12-4, 12-5, 12-6
.60 – .65 12-6 11-7.5, 11-7.75, 11-8, 12-8, 13-5, 13-6, 14-5, 14-6
.80 13-6 12-8, 13-8, 14-4, 14-6
.90 14-6 13-6, 14-8, 15-6, 16-6
1.20 16-6 14-8, 15-6, 15-8, 16-8
1.60 18-6 15-6, 15-8, 16-8, 18-6
2.40 18-10 18-12, 20-8, 20-10
2.70 20-8 18-10, 18-12, 20-10
3.00 20-10 18-12, 22-8

OVER-propping on an IC plane is not a serious concern and does one of two things:

• Fly but underperform
• Stall before takeoff

OVER-propping an EP aircraft is a different matter. The problem here is that the motor is forced to work harder than the makers designed it to. The EP motor won’t stall like the IC engine either. It just keeps trying until it eventually overheats or catches fire. That’s the problem. UNDER-propping EP motors is less of an issue. All that happens in this case is that the craft underperforms.