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Old 26-08-2016, 23:58   #76
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Re: Free prop or locked prop?

If you had a prop like these SS-UNITED-STATES COM on your 'plane and you locked the prop I think gravity would take charge a lot sooner rather than later.....and there would not be a lot of difference if it could free wheel.

Can we reach a consensus here that air and water are fundamentally different?

To take an example..... I have an Aqua4Aerogen.... wind or water. 2 bladed 'water' fan is maybe 5 inch diameter.... produces 5 amps at 5 knots. The 'Air' fan is six bladed maybe 15 inch diam .. needs about 20 knots to give 5 amps. Guess the water is thicker or something.... just a guess.
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Old 27-08-2016, 00:13   #77
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Re: Free prop or locked prop?

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Originally Posted by El Pinguino View Post
If you had a prop like these SS-UNITED-STATES COM on your 'plane and you locked the prop I think gravity would take charge a lot sooner rather than later.....and there would not be a lot of difference if it could free wheel.

Can we reach a consensus here that air and water are fundamentally different?

To take an example..... I have an Aqua4Aerogen.... wind or water. 2 bladed 'water' fan is maybe 5 inch diameter.... produces 5 amps at 5 knots. The 'Air' fan is six bladed maybe 15 inch diam .. needs about 20 knots to give 5 amps. Guess the water is thicker or something.... just a guess.
With a prop like that, gravity would take charge before you got anywhere.

Good guess, it works !
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Old 27-08-2016, 02:34   #78
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Re: Free prop or locked prop?

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Originally Posted by Djarraluda View Post
With a prop like that, gravity would take charge before you got anywhere.

Good guess, it works !
Oh dear oh dear oh dear .... ok .. lets imagine a prop like that made of rice paper.....

and then imagine trying to propel you boat with this Large Sopwith Camel Airplane Propeller | Wood Propeller | Gifts


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Old 27-08-2016, 08:05   #79
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Free prop or locked prop?

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Originally Posted by HopCar View Post
Malbert you're wrong. I have flown a powered glider that when you shut off the engine, the prop shaft was disconnected from the engine. The prop did not turn the engine. It was free to spin in ball bearings. It produced tremendous drag until I stopped it with a brake.

I stand corrected. I wonder if that's true for all planes.

But regardless- i am fully convinced by mainesail that freewheeling is faster than fixed for sailboats. Luckily i have a flexofold 😀 so it's moot


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Old 27-08-2016, 12:30   #80
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Re: Free prop or locked prop?

Most small piston planes cannot disengage the prop from the engine crankshaft. A powered glider can because that reduces drag when gliding. Stoping the airplane prop altogether presents the least drag.
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