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Old 17-06-2016, 08:11   #1
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Do you lock your prop or let it spin?

Hi there,

I am wondering what people do when sailing with a fixed prop?



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Old 17-06-2016, 08:16   #2
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Re: Do you lock your prop or let it spin?

I have a 2006 393 and at low speeds I let it spin in neutral to keep the speed up. But when speed gets over 7 knots I lock(reverse gear) it up to stop vibration and wear


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Old 17-06-2016, 08:23   #3
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Re: Do you lock your prop or let it spin?

I all depends on your boat transmission makers recommendation.

Here is what the Volvo PentaSD 130s (Saildrive) recommendation are.

Gear when sailing
When sailing, set the control lever to reverse if a folding propeller is fitted.
If a fixed propeller is fitted the control lever should be set in neutral or reverse. When using a fixed propeller and sailing with the control lever set to reverse the speed is slowed down though less noise is being made.
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Old 17-06-2016, 08:24   #4
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Re: Do you lock your prop or let it spin?

Check the documentation that the original manufacturer supplied and go by that. There have been many long discussions on this subject but I would go with what the manufacturer says to do. For my year boat and trans, the builder says put in reverse while sailing.
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Old 17-06-2016, 11:45   #5
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Re: Do you lock your prop or let it spin?

Yanmar/Kanzaki says neutral.

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Old 17-06-2016, 11:58   #6
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Re: Do you lock your prop or let it spin?

I always locked mine in gear. Volvo, perkins, hurth, yanmar. But most were Maxprops. The locking gets the prop to feather.
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Old 17-06-2016, 13:49   #7
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Re: Do you lock your prop or let it spin?

There have been prior threads on this subject.


I am of the lock it whilst sailing school by putting the gear shift in reverse because I don't like it making an annoying noise and I read many years ago that it caused less drag that way. Don't know whether that's true or not but I am in the habit now.


I believe it is probably far less likely to pick up trailing or floating lines if it's not spinning.
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Old 17-06-2016, 14:01   #8
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Re: Do you lock your prop or let it spin?

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Originally Posted by RaymondR View Post
There have been prior threads on this subject.


I am of the lock it whilst sailing school by putting the gear shift in reverse because I don't like it making an annoying noise and I read many years ago that it caused less drag that way. Don't know whether that's true or not but I am in the habit now.


I believe it is probably far less likely to pick up trailing or floating lines if it's not spinning.
A propellor that is free to rotate will have the least resistance. However, if it keeps the noise and vibration down then there is no reason why you shouldn't lock the prop if the slower speed through the water is acceptable.

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Old 17-06-2016, 14:02   #9
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Re: Do you lock your prop or let it spin?

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Originally Posted by AFKASAP View Post
Hi there,

I am wondering what people do when sailing with a fixed prop?



Beneteau Oceanis 40 - 2008
Mallorca
I would follow the recommendations of the engine manufacturer for your specific engine.

Here is a Google custom search of CF on search terms " lock prop"

https://cse.google.com/cse?cx=011403...rop&gsc.page=1
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Old 17-06-2016, 14:04   #10
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Re: Do you lock your prop or let it spin?

According to MIT, there is less drag with a spinning propellor.

The transmission type is really the key if you are want to avoid damaging it. Check with manufacturer and then make your decision.

Yanmar/Kanzaki says let it spin. Something about damaging the cone clutch. The noise drives me crazy so I put the transmission in reverse to stop the prop on my Yanmar 3GM30f. So far no problems.
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Old 17-06-2016, 14:04   #11
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Re: Do you lock your prop or let it spin?

I lock ours. Not only the transmission issue but also the noise.

Next step, a feathering prop ...

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Old 17-06-2016, 23:39   #12
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Re: Do you lock your prop or let it spin?

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Originally Posted by Pete7 View Post
A propellor that is free to rotate will have the least resistance. However, if it keeps the noise and vibration down then there is no reason why you shouldn't lock the prop if the slower speed through the water is acceptable.

Pete
I could have gone either way until I considered the physics.

From a work done viewpoint:

The case with locked prop is that the drag produces torque but no work since the prop is not turning - potential energy only.

The case with the unlocked prop is that as the prop is rotating work is being ie torque x turns = work.

BUT:

non rotating = high form drag, lower friction drag.

rotating = lower form drag, higher friction drag (rapid fluid flow over blades as they slice through the water) (Incident fluid flow vector change)

Someone is just going to have to do a "Mythbusters" on this, set up a test jig, carry out the trial and publish the results here for us to argue about.

I still tend towards the lock prop = lowest drag because of the work done implications but am quiet ready to change my inclination on the presentation of contrary facts.

In technology empiricism rules mate.
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Old 18-06-2016, 00:17   #13
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Re: Do you lock your prop or let it spin?

Just upgrade to a feathering prop and lock it in gear, it's the best solution, no torque, no gearbox wear-out, no spinning, no noise, highest speed under sail, best maneuverability, same (or better) speed under power in forward
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Old 18-06-2016, 00:25   #14
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Re: Do you lock your prop or let it spin?

Quote:
Originally Posted by RaymondR View Post
I could have gone either way until I considered the physics.

From a work done viewpoint:

The case with locked prop is that the drag produces torque but no work since the prop is not turning - potential energy only.

The case with the unlocked prop is that as the prop is rotating work is being ie torque x turns = work.

BUT:

non rotating = high form drag, lower friction drag.

rotating = lower form drag, higher friction drag (rapid fluid flow over blades as they slice through the water) (Incident fluid flow vector change)

Someone is just going to have to do a "Mythbusters" on this, set up a test jig, carry out the trial and publish the results here for us to argue about.

I still tend towards the lock prop = lowest drag because of the work done implications but am quiet ready to change my inclination on the presentation of contrary facts.

In technology empiricism rules mate.
Maine Sail did do a Myth Busters type test. He used a scale to measure drag and convincingly proved that a free spinning propeller produces less drag in water.

I have done experiments that proved exactly the opposite with an aircraft propeller. A locked aircraft propeller produces less drag. My tests were done in an ultralight airplane with an airspeed indicator and a sensitive variometer.

I don't know why it is different in air than in water. I think it might have to do with the cord (width) of the propeller blades.
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Old 18-06-2016, 01:27   #15
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Re: Do you lock your prop or let it spin?

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Originally Posted by EWOL Props View Post
Just upgrade to a feathering prop and lock it in gear, it's the best solution, no torque, no gearbox wear-out, no spinning, no noise, highest speed under sail, best maneuverability, same (or better) speed under power in forward
Know anyone who sells them?

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