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Old 16-08-2017, 19:01   #61
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Re: Utilizing free wheeling prop spin

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Originally Posted by Adelie View Post
Because airplane props are generally adjustable pitch and can be fully feathered.

For fixed pitch props, air & water, free spinning is lower drag than stopped.

For adjustable pitch props feathered & stopped is lower drag than freewheeling unfeathered.
That is not correct. A stopped fixed pitch aircraft propeller produces much less drag than a free wheeling prop. I've done the tests.

I used to fly a powered hang glider that was equipped with a centrifical clutch and a prop brake. I would fly to altitude and turn off the engine. At this point the prop was disconnected from the engine by the clutch and free to spin. i would establish my speed for minimum. When I engaged the prop lock the aircraft would accelerate dramatically. When I re-established minimum sink, it was about 200 feet per minute less. This is a fixed pitch prop, it could not be feathered.

Here is a video that proves the opposite is true for a three bladed boat prop.
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Old 16-08-2017, 19:15   #62
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Re: Utilizing free wheeling prop spin

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Because airplane props are generally adjustable pitch and can be fully feathered. For fixed pitch props, air & water, free spinning is lower drag than

Well friend, you are not a pilot. So if you offer opinions to this dear forum, please add some sort of little face at the end to show you are just kidding.
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Old 16-08-2017, 19:34   #63
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Re: Utilizing free wheeling prop spin

Oh goody, two things I love here:

The old free-wheeling vs fixed prop drag debate. Always a treat.

AND an idea to put ANOTHER point of failure in the drive train.

What's not to love hey?
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Old 16-08-2017, 20:43   #64
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Re: Utilizing free wheeling prop spin

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Originally Posted by GILow View Post
Oh goody, two things I love here:

The old free-wheeling vs fixed prop drag debate. Always a treat.

AND an idea to put ANOTHER point of failure in the drive train.

What's not to love hey?
And lets add the old aeroplane pro into the mix - some concepts just keep on giving
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Old 16-08-2017, 20:57   #65
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Re: Utilizing free wheeling prop spin

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And lets add the old aeroplane pro into the mix - some concepts just keep on giving
Perfect score!
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Old 17-08-2017, 00:09   #66
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Re: Utilizing free wheeling prop spin

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Perfect score!
Bonus points for free energy, too!

Jim
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Old 18-08-2017, 12:51   #67
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Re: Utilizing free wheeling prop spin

10/12 years ago you could have your engine replaced by large bank of batteries fed from a generator driven by the prop. I think it was a Californian company.Don't know if it still exists.
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Old 18-08-2017, 13:03   #68
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Re: Utilizing free wheeling prop spin

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I would bet the two different possible answers are available from two different manufacturers of engines and transmissions.

The appropriate mode depends on the specific combination of engine and transmission (gearbox and bearing lubrication and clutch type being important factors)
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Old 18-08-2017, 13:18   #69
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Re: Utilizing free wheeling prop spin

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That is not correct. A stopped fixed pitch aircraft propeller produces much less drag than a free wheeling prop. I've done the tests.

I used to fly a powered hang glider that was equipped with a centrifical clutch and a prop brake. I would fly to altitude and turn off the engine. At this point the prop was disconnected from the engine by the clutch and free to spin. i would establish my speed for minimum. When I engaged the prop lock the aircraft would accelerate dramatically. When I re-established minimum sink, it was about 200 feet per minute less. This is a fixed pitch prop, it could not be feathered.

Here is a video that proves the opposite is true for a three bladed boat prop.
I for one can not find a parallel between a boat props and aircraft props. The viscosity of the medium is two different animals. Turning one prop at a few thousand RPM and one at a maybe a few hundred?
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Old 18-08-2017, 13:22   #70
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Re: Utilizing free wheeling prop spin

Buy a feathering or folding prop to save drag, then install a few solar panels.
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Old 18-08-2017, 13:25   #71
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Re: Utilizing free wheeling prop spin

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The viscosity of the medium is two different animals.
Absolutely, a big +1 on that!

Cup your hand and spin in a circle then jump in the water, cup your hand the same and feel the difference. Some would say "The arm, the arm is fighting more water!" Well, it was also fighting the air. Unless your body somehow dramatically changed between the two mediums.
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Old 18-08-2017, 20:10   #72
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Re: Utilizing free wheeling prop spin

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Well friend, you are not a pilot. So if you offer opinions to this dear forum, please add some sort of little face at the end to show you are just kidding.
My posts are my opinions just as your posts are your opinions, except I am generally not nearly as rude to others when I offer them.

Regards.
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Old 18-08-2017, 22:33   #73
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Re: Utilizing free wheeling prop spin

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Pete7, Do you sail at night? How are those solar panels working for you from sunset to sun rise? Isn't the point of having a sailboat going green? If your prop free spins why not utilize that potential power? Why add a clutch? Stop the wear to the transmission. The engine and transmission are taken out of the equation. Why would you even consider changing out your engine for a hybrid one?
Ah, the old solar panels don't work at night story. Of course they don't work at night which is why one installs a complete solar system, panels which through the day feed an appropriately sized bank of batteries which enable the operation of required electrical devices until such time as the sun returns, simple really.
The utilisation of a free spinning prop to produce power merely increases the drag which effectively slows the boat, sometimes noticeably and the claim that one should not allow the transmission to spin whilst sailing may be true for some transmissions but is not universally true, many gearbox manufacturers advise to let the prop spin and not to lock the transmission.
Perhaps your concept is in your opinion a good one however I believe it has had it's day and the combination of wind and solar coupled to an appropriate battery bank is a far more practical arrangement.
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Old 18-08-2017, 22:49   #74
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Re: Utilizing free wheeling prop spin

I can very well understand the need to work on your boat systems and invent new technology to be used. Specially so if one has a background in engineering. However, as people who have read previous threads on the same topic will know, that's not an easy task. Doable for sure. So, invent on.

I'm personally a great fan of hydrogenerator. I have a transom mounted DuoGen and use that whenever we sail for longer distances in cloudy weather. The main thing that made me to put an idea of prop shaft generator away is that I don't like the noise of rotating prop shaft. DuoGen is much quieter but there still is some vibration involved.

But, and that's a big but, those both are much more quiet then your average boat engine or a gen set.
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Old 19-08-2017, 07:05   #75
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Re: Utilizing free wheeling prop spin

[QUOTE=Make_My_Day;2457011]I am very interested in this conversation.

We have a Ford Lehman diesel with Velvet drive transmission that I am told from the previous owner is supposed to remain in neutral when sailing. This is a free wheeling prop and shaft that is going to turn anyway.

Can it not be connected with a pulley on the shaft and a timing belt to pulley attached via a clutch to a generator? Would this be harmful in anyway to the transmission?

I am always looking for additional alternative ways to add to the charging system to help keep the batteries topped up. When sailing at night, this seems like a good way to use energy that would otherwise be wasted.

Am I missing something? Thank you some one actually see's the value
The purpose of adding a clutch was to remove the transmission from the equation. Stop excessive wear and tear on the seals and bearings.
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