Extreme Speed Prop Planes Discuss the need for speed with fast prop planes (Screamin Demon, Diamond Dust, Shrikes or any REAL sound breakin'''' plane)

Prop question?

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Old 09-20-2004, 10:00 PM
  #1  
Zeroman
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Default Prop question?

Can a prop fly faster than its calulated speed?
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Old 09-21-2004, 04:21 AM
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der_steuermann
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Default RE: Prop question?



No, even if considering an ideal environment (no draggy airframe/engine, no air resistance) the theoretically calculated speed would be the best possible one.

From experience a very good speed setup reaches about 90% of the theoretical prop speed at given rpm (rpms of an unloaded engine during a powerdive derived from Doppler effect measurements).

Boundary conditions are:

- low drag airframe supporting the engine/prop combo to unload with ease after the first dive
- low drag speed prop designed for a certain rpm and target speed
- an engine swinging the prop within its highest efficiency
- preferably subsonic prop tip speeds
- speed measurements in both directions, headwind and downwind

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Old 09-21-2004, 09:25 AM
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Default RE: Prop question?

Thanks for the info der-steurmann, there has been quite a discussion about this.Some club members say they fly faster than the calculated speed all the time.Chris.
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Old 09-21-2004, 10:19 AM
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daven
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Default RE: Prop question?

I'm not convinced that a prop CAN'T fly faster than its calculated speed.

I think its possible, but it may be due to incorrrect pitched props.

I've seen APC 10x7 props go faster than what they should be capable of going.
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Old 09-21-2004, 11:59 AM
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Mike Connor
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Default RE: Prop question?

Since a typical prop starts developing forward thrust at a negative 3* pitch I would have to say yes. The calculated forward speed of a 0* pitch prop would be 0 but under the right circumstances it may even get a plane off the ground. This advantage is usually lost to drag as speed increases.
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