Experimenter is a magazine created by EAA for people who build airplanes. We will report on amateur-built aircraft as well as ultralights and other light aircraft.
Issue link: http://experimenter.epubxp.com/i/101874
wisdom applies…generally. Larger-diameter props are heavier; not just because of the diameter, but also because strength and rigidity are more difficult to achieve, thus the longer the prop. Longer props are more expensive and more subject to damage from ground strikes, and they limit rpm (and sometimes horsepower available). Aircraft speed and mission also play significant roles in propeller diameter choice. For example, pick two aircraft with the same engine, say, a Piper Super Cub and an RV-6, each running a Lycoming 180. The Super Cub prop may be as long as 82 inches for short takeoff and landing flights and slow speed capability, while the RV-6 will turn a 72-inch-diameter prop to achieve high cruise and top speeds. shapes. Plus, if you have a prop strike with a wood prop it basically acts as a "fuse" and turns to splinters, minimizing internal engine damage. The main downsides to a wood propeller are more frequent maintenance (frequent bolt torque checks) and often lower performance than a metal or composite prop. (To maintain the rigidity necessary, a wood prop usually needs a heftier chord than would be optimum.) Of course, the lower the airspeed, the less the performance difference is. "Pitch" refers to the distance the propeller would travel in a single revolution. (The term "airscrew" was often used in the early days of flight.) An airplane's propeller, in real life, has various pitches along its length, from hub to tip; "pitch" is an effective value only, and its measurement differs even among manufacturers and sometimes among their various products. Still, any published pitch number can be useful when you're staying in a given manufacturer's product line. Prop Materials There's a third really important factor: the material of which the prop is constructed. Wood, the choice for decades, has a lot of advantages: It is light, relatively durable, resistant to fatigue, inexpensive, and available in endless A loose metal prop will destroy itself and damage the hub Even a tough all-composite prop will be ruined when it hits something solid. When a prop is even slightly loose, it can "burn" as it rubs against the hub causing the prop to become less efcient. Photography courtesy Sensenich Propeller and by Tim Kern EAA Experimenter 37