prop shaft spinning when sailing

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chrisD

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I have recently purchased a Westerly with a Volvo 2030 engine and the prop spins quite noisily when sailing, even fairly slowly. The manual is emphatic that it must not be left in gear. I have a recollection that a simple fix is to put a mole wrench around the prop shaft, which would be quite easy in this boat. Is this just an old wives tale, or does it really work?
 
check the manuel ( The manual is emphatic that it must not be left in gear ) this is wrong by volvo should be put in reverse gear i do with mine and all solved with that noise and hope the gearbox holds longer
 
I had the same with the 2030 and a two blade fixed prop, although it'd start rotating at 5kn.

I fitted a Kiwi. (An expensive fix mind) but you get less drag when sailing and more thrust when on engine.
 
Prop turning

The whole time your prop is turning your gear box is wearing, only slightly but it is still wearing.
It is normal practise to engage reverse gear when not running the engine, remember to engage neutral before restarting the engine.
Never heard of Volvo instruction not to engage gear.
 
There are many tales and opinions about this. I heard it said that the principle of not putting the drive in gear to stop the prop goes back to the days when hydraulic drives were more common and so the box kept driving pressure up when loaded. On a previous boat with a fixed two-blade prop we always droppped the lever into reverse when sailing or went mad with the noise, but it should be said that we sometimes had difficulty getting back into neutral ready to start the engine again. It helped to slip into neutral in the midst of going about so there's little load on the drive.

Now, I don't worry as the prop folds as soon as the shaft stops rotating, so there's little or no load on the drive and she goes back into neutral really easily. I guess it's the same with a feathering prop.

Rob.
 
If you lock a fixed prop you will lose half a knot of sailing speed. Never mind all the arguments about helicopters falling that will no doubt follow, it has been measured scientifically and was reported in the mags last year.

Even my Autoprop rotates with the gearbox in neutral, although presumably the drag is very small. I lock my shaft by putting the gearbox in reverse.
 
The Volvo Penta MD2030 manual clearly says:

"If the boat has a fixed propeller the control lever must be in the neutral position when sailing. If the boat has a folding propeller the control lever must be in the astern position".

I leave it in the neutral position with my 2-bladed fixed propeller. And yes, the noise is very annoying. By replacing next year the 2-blader with a 3-blader I expect to be much less noise.
 
cmedsailor said:
The Volvo Penta MD2030 manual clearly says:

"If the boat has a fixed propeller the control lever must be in the neutral position when sailing. If the boat has a folding propeller the control lever must be in the astern position".

I leave it in the neutral position with my 2-bladed fixed propeller. And yes, the noise is very annoying. By replacing next year the 2-blader with a 3-blader I expect to be much less noise.
Click to expand...

replace it with a feathering (kiwi prop?) and it will stop turning all togther and give you less drag...
 
mattnj said:
replace it with a feathering (kiwi prop?) and it will stop turning all togther and give you less drag...
Click to expand...

Well, yes any feathering or folding will give me less drag and less noise but besides the cost I prefer the simplicity of the fixed propeller. But anyway I am planning to replace it with a Campel Sailer propeller that claims to have the same drag as a 2-wide blader fixed propeller.
 
I thought that mechanical boxes were lubricated by splash. So in the locked position the splash doesn't happen but the fixed prop still applies a bit of force onto the gears, hence you get accelerated wear at the contact points. If left to rotate sufficient lube is thrown around to prevent this. In the folded prop case you keep the box locked to allow the prop to fold. The folded props provides no torque to the box so the local wear does not happen.

Just an opinion based on some distant memory which could be wrong. I expect that modern mechanical gearboxes have oil pumps as well.
 
Volvo are correct or they were with mine.
We had just changed to the spare fixed prop and sailed off with it in reverse, as I had done on many yachts in the past to stop the prop turning.

After a brisk three hour sail, when we came to start the engine it was locked solid in reverse, at first I thought it was the gearlever/throttle mechanism as these often wear in the sliding junctions that operate throttle and gear change. Not wanting to arrive in a strange harbour in reverse or with a dodgy gear change I dismantled it to find out it was fine! started the engine in reverse and it did free up but it was quite an effort to get it out of reverse. Then I read the manual and it said don't sail with it in gear!
 
BlowingOldBoots said:
I thought that mechanical boxes were lubricated by splash. So in the locked position the splash doesn't happen but the fixed prop still applies a bit of force onto the gears, hence you get accelerated wear at the contact points. If left to rotate sufficient lube is thrown around to prevent this. In the folded prop case you keep the box locked to allow the prop to fold. The folded props provides no torque to the box so the local wear does not happen.

Just an opinion based on some distant memory which could be wrong. I expect that modern mechanical gearboxes have oil pumps as well.
Click to expand...

I really can't see that a pretty much stationary force applied between teeth could accelerate wear, even on older style through-hardened gears. Modern case hardened ones (which I would assume would be used in most purpose-built marine gearboxes) show virtually no wear after years of use. I used to monitor gear teeth on 2 MW water injection pumpsets and remember the original grinding marks clearly visible after five years of constant use.
 
vyv_cox said:
If you lock a fixed prop you will lose half a knot of sailing speed. Never mind all the arguments about helicopters falling that will no doubt follow, it has been measured scientifically and was reported in the mags last year.

Even my Autoprop rotates with the gearbox in neutral, although presumably the drag is very small. I lock my shaft by putting the gearbox in reverse.
Click to expand...

Backing up what vyv_cox says, I posted the following on the WOA web forum Jan 2009:-

"Scientific investigation.

http://strathprints.strath.ac.uk/5670/1/strathprints005670.pdf

Read the pdf report, and the conclusion on page 24.
"The experimental results confirm that a locked propeller produces
greater drag than does a freewheeling screw (up to 100% more drag was
observed, this being at higher speeds). Furthermore, for the
freewheeling case, the magnitude of the hydrodynamic resistance is
significantly affected by the amount of frictional torque on the shaft,
low torque being accompanied by log drag."

The Volvo 2000 series with MS2 gearbox Owners Manual states -
"When under sail, the control lever should be in the neutral position if
the propeller is a fixed propeller. If the propeller is a folding
propeller, the control lever should be in the reverse position. Start
the engine and run it for five minutes every ten hours when on
long-distance cruises."

Nanni state -
"to put the engine into reverse when sailing and also if anchored in a
strong tidal flow."

Further information/results on fixed or rotating prop drag -
http://www.flexofold.com/Test_Results.php - about halfway down."


So basically, it is up to you, with reference to your gearbox recommendation.
 
philip_stevens said:
Backing up what vyv_cox says, I posted the following on the WOA web forum Jan 2009:-

"Scientific investigation.

http://strathprints.strath.ac.uk/5670/1/strathprints005670.pdf

Furthermore, for the
freewheeling case, the magnitude of the hydrodynamic resistance is
significantly affected by the amount of frictional torque on the shaft,
low torque being accompanied by low drag."
Click to expand...


Well, who'd a thunk it? It's almost as if turning a propeller produces thrust ...

Seriously folks, this reflects the thing almost always missing from these discussions: the drag you'll get from a spinning prop is critically dependent on the torque resistance to the shaft turning. Low torque means low drag.
 
chrisD said:
I have recently purchased a Westerly with a Volvo 2030 engine and the prop spins quite noisily when sailing, even fairly slowly. The manual is emphatic that it must not be left in gear. I have a recollection that a simple fix is to put a mole wrench around the prop shaft, which would be quite easy in this boat. Is this just an old wives tale, or does it really work?
Click to expand...
I have told this story many times, Lynn from VP spoke to me a couple of years ago when I had a a VP2030 with an MS2 box, he said that VP used to advise putting in reverse BUT it would jam in reverse, they advised to give the starter a flick to loosen it and then carry on from there. However customer feedback was that they didnt like that so then their advise was to leave in neutral!
Stu
 
We have to leave ours in gear or the prop (Bruton Autoprop) won't feather. The manual says just shut down the engine in gear and leave it like that.

But there is still some torque on the shaft with the prop feathered, and it jams in gear. The first time this happened it really freaked me out. I was down in the engine space with a wrench trying to free up the gearshift.

Then I just started cranking the engine in gear. Doesn't seem to mind a bit; cranks right up happily that way. And with torque on the driveshaft in the cranking direction of the engine, I start to understand why not.
 
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