A composite propeller is made of plastics and other materials such as carbon fiber and fiberglass. As it is typically lighter than aluminum and steel, a composite propeller uses less power to spin than other types of propellers. In aircraft, a composite propeller usually creates less noise than other types of propellers. This is dependent on type, size and manufacturer. In marine applications, a composite propeller will often withstand strikes with rocks much better than stainless steel or aluminum propellers.
The performance potential of a composite propeller lies in its reduction in rotating mass. The lighter a propeller is, the more performance potential it possesses. By weighing less, the engine is able to spin the propeller faster and at an increased rate of speed. This results in quicker takeoffs and a higher rate of climb once airborne. The lighter composite propeller also requires less horsepower to turn, resulting in better fuel economy. Another benefit of using a composite propeller on an airplane lies in the ability to occasionally carry a heavier payload.
In a marine application, the composite propeller is many times more durable than a stainless steel propeller; the blades of the composite version can withstand the occasional strike of the waterway bottom without resulting in damage to the propeller. The composite blades are also often thinner than an aluminum type of propeller. The thin blades give the composite unit the performance traits of a stainless steel unit with the lower cost of an aluminum unit. The soft aluminum is not as forgiving when striking an object, and it typically results in a broken propeller blade.
The composite blades will flex when contacting a hard object. This flex often saves the propeller by preventing a chipped or broken propeller blade. Even a large nick can often result in uncontrollable vibration that can damage the engine's bearings. The downside of running a composite propeller lies in the inability to repair a damaged unit. Aluminum and stainless steel propellers usually can be straightened and sharpened when damaged, but a composite unit usually can not be fixed.
For enthusiasts wishing to gain some of the performance of a stainless steel propeller with the cost of an aluminum unit, the composite units are a good choice. In waters where there is no danger of striking rocks and submerged logs, the composite-type propeller can give many years of trouble-free use. In waters that are strewn with underwater hazards, a composite type propeller may be a less costly expense when compared to damaging more expensive units.
