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Electric Stunt => Gettin all AMP'ed up! => Topic started by: Dennis Toth on July 05, 2010, 09:49:28 AM
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Guys,
One question that's always seems to come up in stunt discussions is how stiff a prop needs to be. In ECL we tend to use APC -E props, in the wet world they use carbon fiber props. Our APC-E's are very thin and pretty light but they do flex a bit more then wood or carbon props. So how much performance are we giving up due to the flexing?
Best, DennisT
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Hi Dennis,
The short and woefully incomplete answer is ... some.
Not only that, but flapping, flopping and wobbling props make noise.
your mileage may vary!
Dean P.
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An interesting question. Has anybody done any work on this? In particular, how much the stiffness is increased by the centrifugal force of rotation (for an extreme case of this, see helicopter rotors).
E-props are thinner and lighter by virtue on not having the in-plane accelerations that IC props must deal with, and the thin blades certainly seem to be efficient. Can't be getting too much shaking and wobbling, but the theorists among us may point to where the ideal might be. Anyone listening to PW's plane go around can verify how quiet it is.
Our e-props are getting big enough that we might need root hinges soon (joke).
John W
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Did anyone put an APC Prop on the scale? Or anyone did a weight comparison between props?
My Gator prop are 29gr for a 2 Blade at 14in diameter.
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Is there any advantage from the electric props other that weight. Are the electric props designed to work better in the RPM and torque ranges that are found in electric motors. Don't know if I stated it right.
Andy
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Keeping in mind that with lighter weight comes lighter rotational mass, the only other real advantage I have seen is that they are thinner, and seem to be much more efficient than a "standard" prop..
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Andrew any prop puts two loads on the motor. A mechanical load that comes from the weight of the prop witch is more like a baseball player trying to swing a bat versus two and a aerodynamic load just like a wing on a plane. They both take power from the motor. So an efficient prop is light yet aerodynamic. Stiffness comes in place too because you do not want it to flatter. I guess the challenge is how thin can we go and maintain integrity.
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Heavy prop is problem especially because of precession. Precession limits flying properties of the stunter and precession is difficult to trim out, so lighter is better.
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Andrew any prop puts two loads on the motor. A mechanical load that comes from the weight of the prop witch is more like a baseball player trying to swing a bat versus two and a aerodynamic load just like a wing on a plane. They both take power from the motor.
Not the former.