As a bit of a follow on from my last question on saildrives:-

When sailing, do you all allow prop (fixed 3-blade) to free-wheel, or as I do leave in gear and suffer a little drag ??
I am conscious of not wearing our my absolutely dripless shaft seal.

save up for a folding ...............you will love it !

Sadly S & S, that won't fit. Keel-hung rudder. Next boat maybe.

feathering ? also better than folding in reverse ....may fit ....more $ though

If you freewheel a propellor, be it 2 or 3 blade, it will act like a governor and you will hear it when sailing going whirr, whirr, whirr...whirr....whirr whirr....whirr, whirr, whirr, when the boat speeds up and slows down in the swell etc. So the faster the boat wants to go the more resistance the spinning prop and shaft will try to prevent speed.

Also letting it freewheel will cause unwanted wear to the P or A bracket bearing, the stern bearing, the stern seal and the thrust bearing in the gearbox and probably other gearbox internals.

Most yachts have a gearbox with a cone or plate clutch and in most cases stopping the prop shaft freewheeling when sailing with the engine stopped just requires engaging the clutch in reverse to stop it.

If you engage it in forward, the boat speed may override the clutch and wear it out.

If the gearbox is hydraulic drive it may be a whole different circumstance and you need to refer to the manufacturer manual and you may need to fit a shaft brake.

In any case a fixed blade propellor that is locked in place gives a fixed amount of drag for the speeds a yacht usually does.

If your yacht is primarily a cruising yacht, fixed blade props locked when sailing tend to be trouble free with less maintenance issues.

There will be other opinions but that is mine. Cheers.

I let mine free wheel, less drag and I need all the help I can get. Cutlas bearing and stern gland, not much to wear there and the ZF rep confirmed the hydrolic transmission would come to no harm. If I had a 2 blade prop I would lock it up in line with the keel though

There are a number of examples of testing done with actual props on actual boats using rigs to measure the difference in drag between fixed and freewheeling. Those that I have seen have all demonstrated that in the water a fixed prop has far more drag than a freewheeling one.
One test was by, if memory serves me correctly, Practical Sailor magazine in the UK and another by Compass Marine in the US.

My Volvo Penta manuals says to allow the prop to freewheel. I've also read those tests that show significantly less drag from a free spinning prop.

Cheers

Bristol

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Bristolfashion said..
My Volvo Penta manuals says to allow the prop to freewheel. I've also read those tests that show significantly less drag from a free spinning prop.

Cheers

Bristol

Exactly Volvo Manuel says free spin for fixed and reverse for folding.

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Bristolfashion said..
My Volvo Penta manuals says to allow the prop to freewheel. I've also read those tests that show significantly less drag from a free spinning prop.

Cheers

Bristol

Exactly Volvo Manuel says free spin for fixed and reverse for folding.

If you have a cone-clutch gearbox (like my Yanmar 2GM) and a right-hand prop, then when you lock it in reverse the torque on the prop will act via the shaft helix to drive the cones harder together. However if you lock it in forward, the prop torque will tend to do the opposite and try to pull the cones apart. This reduced cone friction can allow slipping which could glaze the cones. You will then be up for removal, disassembly and deglazing of the gearbox.

Cheers, Graeme

^^^ Thanks for that. It clarifies the point I was making.

Hi All

With my two blade prop on a shaft if i am cruising it let it spin as per the Yanmar instructions but when we are racing I lock it vertically behind the skeg with the lever in reverse

Regards Don

Hi Don, how do you know when prop is vertical ?
My guess id you marked the shaft so you can check?

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Craig66 said..
Hi Don, how do you know when prop is vertical ?
My guess id you marked the shaft so you can check?

Hi Craig

Your guess is right

Before a race i crawl up the 1/4 berth with a torch and turn the shaft to the correct position and yell out to my mate in the cockpit to put the lever in reverse to lock the shaft in position

I don't know how much difference it makes in boat speed but i figure any bit helps

Regards Don

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Donk107 said..
Hi All

With my two blade prop on a shaft if i am cruising it let it spin as per the Yanmar instructions but when we are racing I lock it vertically behind the skeg with the lever in reverse

Regards Don

I have a two blade prop as well & do the same - the sound of the prop spinning annoys me. I have a hydraulic box so I have made a simple prop lock.
A simple texta mark tells me when it's vertical.

I let my 3 blade fixed prop spin on the saildrive. Local Volvo mechanic didn't think that it would cause any appreciable wear and I see at least half a knot speed gain when it's spinning freely. Noise is the downside though, and it was feeling a bit out of balance lately and vibrating... I wonder why?

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2bish said..
I let my 3 blade fixed prop spin on the saildrive. Local Volvo mechanic didn't think that it would cause any appreciable wear and I see at least half a knot speed gain when it's spinning freely. Noise is the downside though, and it was feeling a bit out of balance lately and vibrating... I wonder why?

Wow 2bish, those are genuine stalagmites.

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saintpeter said..
When sailing, do you all allow prop (fixed 3-blade) to free-wheel, or as I do leave in gear and suffer a little drag ??
I am conscious of not wearing our my absolutely dripless shaft seal.

The amount of drag depends on the pitch of the prop. We've been through this discussion before.

Low pitched props will create more drag when freewheeling, while high pitched props will create less drag when freewheeling. Most boat propellers are considered "High pitch" -- so freewheeling them means less drag.

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2bish said..
I let my 3 blade fixed prop spin on the saildrive. Local Volvo mechanic didn't think that it would cause any appreciable wear and I see at least half a knot speed gain when it's spinning freely. Noise is the downside though, and it was feeling a bit out of balance lately and vibrating... I wonder why?




Hi 2bish

H\A couple of questions if you don't mind me asking

How long since you slipped her and was the saildrive leg antifouled at the time

Regards Don

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nebbian said..

saintpeter said..
When sailing, do you all allow prop (fixed 3-blade) to free-wheel, or as I do leave in gear and suffer a little drag ??
I am conscious of not wearing our my absolutely dripless shaft seal.

The amount of drag depends on the pitch of the prop. We've been through this discussion before.

Low pitched props will create more drag when freewheeling, while high pitched props will create less drag when freewheeling. Most boat propellers are considered "High pitch" -- so freewheeling them means less drag.

Well yes the pitch will have a bearing on the amount of drag, but surely even the lowest pitched prop must have less drag being able to free wheel ?

Do you want to go fast, or is rotational wear more important?

Fixed prop - Let it spin. You will go faster, but have rotational wear (really?) Just me, but I'll take a bit of extra speed over some rotational bearing seal wear without load any day.

Folding prop: Fixed. Always. Lock it in forward or reverse, does not matter. You want it to fold. If it free spins, blades fold out creating drag, which is counter productive to why you spent the big bucks on the folding prop in the first place.

Simples!!

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saintpeter said..
As a bit of a follow on from my last question on saildrives:-

When sailing, do you all allow prop (fixed 3-blade) to free-wheel, or as I do leave in gear and suffer a little drag ??
I am conscious of not wearing our my absolutely dripless shaft seal.

with 3 blade fixed prop you should have the clutch in neutral. Having it in gear (either forward or reverse) and not running the engine will burn your clutch out due to drag on the props. Read your engine manual, it should be somewhere in there too

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Poodle said..
Folding prop: Fixed. Always. Lock it in forward or reverse, does not matter. You want it to fold. If it free spins, blades fold out creating drag, which is counter productive to why you spent the big bucks on the folding prop in the first place.

Simples!!

This is what I thought. Why are there so many people around who say a folding prop must be locked in reverse? We use forwards with no dramas. And the lever is more out of the way there.

Our Yanmar says to fold the prop using reverse, then put in neutral.

www.endeavourowners.com/dscsn/info/bulletins/YMTQTB11-017.pdf

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FreeRadical said..
Our Yanmar says to fold the prop using reverse, then put in neutral.

www.endeavourowners.com/dscsn/info/bulletins/YMTQTB11-017.pdf

yep once is folded it can stay in neutral . most of the time it will fold even if its already in neutral

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Seebreasy73 said..

saintpeter said..
As a bit of a follow on from my last question on saildrives:-

When sailing, do you all allow prop (fixed 3-blade) to free-wheel, or as I do leave in gear and suffer a little drag ??
I am conscious of not wearing our my absolutely dripless shaft seal.

with 3 blade fixed prop you should have the clutch in neutral. Having it in gear (either forward or reverse) and not running the engine will burn your clutch out due to drag on the props. Read your engine manual, it should be somewhere in there too

When my fixed blade prop is in gear (I use reverse for tidy cockpit) the shaft does not turn at all -so no wear on anything.
I guess my original question is about wear on the shaft seal during many hours/days/weeks of sailing when the prop is not in use.

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saintpeter said..

Seebreasy73 said..

saintpeter said..
As a bit of a follow on from my last question on saildrives:-

When sailing, do you all allow prop (fixed 3-blade) to free-wheel, or as I do leave in gear and suffer a little drag ??
I am conscious of not wearing our my absolutely dripless shaft seal.

with 3 blade fixed prop you should have the clutch in neutral. Having it in gear (either forward or reverse) and not running the engine will burn your clutch out due to drag on the props. Read your engine manual, it should be somewhere in there too

When my fixed blade prop is in gear (I use reverse for tidy cockpit) the shaft does not turn at all -so no wear on anything.
I guess my original question is about wear on the shaft seal during many hours/days/weeks of sailing when the prop is not in use.

It is not wear by turning but wear on the clutch by force. Would be very rare if there was enough power to turn over the engine/shaft, especially considering the gearbox reduction ratio as well. Also, likeliness to develop resonance created by the passing water on the propeller when the blades are fixed in ope position. And that, actually can cause seal damage over time. You will have wear either way, but shaft seals should last many years if lubricated adequately...

So while we are here, does anyone have an opinion on the feathering kiwi prop ? I'm excessively horse powered and propellerd like a tug, which is good for steaming into a swell or dragging a grounded vessel off. But in reverse she's flat out hauling the anchor chain tight and must be causing ridiculous amount of drag under sail ( even with it free wheeling )