On the other hand, plastic props are more durable than a wood prop. If you are going to bump the ground or nose over a lot, like when you are first learning to land your R/C trainer, you may want to use a synthetic prop to save money. Once you can land without clipping the prop, you can switch to wood.

SAFETY FIRST! When people hurt themselves with a model airplane, it almost always involves the propeller. Props are dangerous and you must be constantly on guard to avoid accidents. A spinning prop is like a buzz saw - it can and will cut right through fingers, arms, legs, etc.

One last thought on safety and propeller selection. A wood prop will usually break if it hits your hand while a plastic prop will not. A plastic prop will usually cut much deeper, causing more serious damage to you than a wood prop. This safety aspect of wood propellers should not be overlooked.

Each of the three propellers shown above is designated as a 10-6, but they are from different manufacturers and are made of different materials. The top propeller is wood, the middle prop is non-reinforced polyester, and the bottom one is glass-filled nylon. When choosing a wood prop, look for grain lines that are straight and run from tip to tip. Avoid wood props with curved grain that runs off the leading or trailing edge.

PROPELLER PREPARATION: Propellers usually need some amount of preparation before bolting them in place. Often times the center hole will have to be enlarged to fit the engine's crankshaft. Always use a special-purpose "prop reamer" or a drill press to enlarge the hole. Be careful to make the enlarged hole straight and perpendicular to the prop hub.

All propellers should be carefully hand balanced using a commercially-available prop balancer. An unbalanced prop causes excessive vibration which can lead to structural failure and radio problems. Lightly sand the front side of the heavy blade until the prop balances. Avoid sanding the tips or changing the shape of the propeller.

The sharp edges of injection molded synthetic props can be sanded lightly to remove any molding flash.

Don't sand any more than necessary and rebalance the prop when finished.

Always check your prop carefully after each flight to be certain it hasn't been broken, cracked, or nicked. Even a small nick in the leading edge can cause the blade to separate on the next run, so discard all propellers with any kind of flaw.

TO MAKE PROPS LAST LONGER: You will break fewer propellers if you do one simple thing. Always bolt the prop on the engine so that when the piston first comes up against compression (in the normal direction of running) the prop is horizontal! In a power off landing, the prop will windmill to that position and be much less likely to come in contact with the ground.

This propeller is being balanced using an inexpensive, hand-held balancer (shown below). It is a good idea to check the balance on all propellers because even new props fresh from the factory can be out of balance.

This is the correct propeller position when the piston first comes up on compression. Notice the "chicken stick" being used for starting.

HAND-HELD PROPELLER BALANCER