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  #21  
Old 09-14-2012
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Re: Propeller Drag - Challenging my intuition

Here is the link to a thread with the official statement from Yanmar about leaving the engine in neutral:

SailboatOwners.com - A Definitive Answer (YANMAR Gear Position)
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Old 09-14-2012
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Re: Propeller Drag - Challenging my intuition

Jordan, locking the prop in the appature between the keel and the rudder will be less drag than letting it spin providing we're talking about a 2 blade prop. The keel has already "opened the slot in the water to move thru. How do you know when the prop is in the slot? On a boat I used to race on we had a three blade folding prop where we lined up one blade vertical. All it took was a sharpie mark on the shaft lined up with a sharpie mark on the drip seal. Of course to do this you either have to dive and place the prop vertical and then mark or wait to pull the boat for the winter. Of course getting in to see the shaft can be a challange for a contortionist sometimes.
It is a well established conclusion that allowing a non folding prop to spin is less drag than locking it.

John
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  #23  
Old 09-14-2012
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Re: Propeller Drag - Challenging my intuition

And here is a thread with a LOT more information on fixed vs. free spinning..

Fixed vs. Freewheeling (LINK)
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  #24  
Old 09-14-2012
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spinning prop on Volvo penta

I have recently read in the volva penta manual that with a reversing transmission the propeller should not be left to spin without the engine running. The transmission is similar to a car auto trans and has a oil cooler that operates the same as the engine heat exchanger. With engine not running no cooling and transmission overheats and damage occurs. Now to find a shaft brake.
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Old 09-14-2012
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Re: Propeller Drag - Challenging my intuition

Oh hey! Lookie here, Maine Sail is on the forum. Hi.

I linked to your article, including video in my very first post so watching the video again doesn'tt help any more than it did the first time - it worked once and that was enough. ;-) As I said from the outset, your article is what made me second guess my gut-feeling. For what it's worth there are people that are stubborn and refuse to change their minds once set (check the Politics forum here for many examples.) I'm not one of them and I change my mind when a better explanation comes along - thanks for doing that today.

jray, yes, I am aware of Yanmar's advisory, mentioned it and it is linked in Maine Sail's article as well. We seem to be repeating the same links and content that we started with... I feel like we're just spinning our wheels (and props) in this discussion. It's beginning to be a drag. (ok ok, I'm done with the horrible puns.)

John (jfdubu)... yes, I had thought about marking the shaft, but that is very impractical on my boat since it lies under my cockpit floor with 12 bolts holding on the compartment. Not something I'll pull off on a regular basis. Do they make non-skid plexiglass? ;-)
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Old 09-14-2012
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Re: Propeller Drag - Challenging my intuition

Quote:
Originally Posted by JordanH View Post
John (jfdubu)... yes, I had thought about marking the shaft, but that is very impractical on my boat since it lies under my cockpit floor with 12 bolts holding on the compartment. Not something I'll pull off on a regular basis. Do they make non-skid plexiglass? ;-)
I was thinking it would actually work well on my Contessa because I have an inspection hole right there. You don't? (and it's way more than 12 bolts for the actual compartment...) It wouldn't be worth it for short sails but if I were going a distance it might.
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Old 09-14-2012
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Re: Propeller Drag - Challenging my intuition

Hmmm... Do you have a JJ Taylor or Jeremy Rogers Contessa? Mine is JJ Taylor #312 (1983). It has the cockpit divided into 2 sections, aft of the cockpit drains is solid/fixed. Forward of the cockpit drains is a single compartment cover with 12 bolts holding it down. (2x end, 4x sides). Definitely no inspection hatch on mine.

Well, I will mark it this winter when I pull the boat out just in case I ever want to try to lock it in place.

Now, I have a Farymann k34 with a Hurth transmission. Any chance you have the same? What do you think of the above point about cooling/oil circulation of the transmission?
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Old 09-14-2012
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Re: Propeller Drag - Challenging my intuition

Quote:
Originally Posted by JordanH View Post
Hmmm... Do you have a JJ Taylor or Jeremy Rogers Contessa? Mine is JJ Taylor #312 (1983). It has the cockpit divided into 2 sections, aft of the cockpit drains is solid/fixed. Forward of the cockpit drains is a single compartment cover with 12 bolts holding it down. (2x end, 4x sides). Definitely no inspection hatch on mine.

Well, I will mark it this winter when I pull the boat out just in case I ever want to try to lock it in place.

Now, I have a Farymann k34 with a Hurth transmission. Any chance you have the same? What do you think of the above point about cooling/oil circulation of the transmission?
I've got a 79' JJ Taylor. I have an inspection hole in both the removable engine cover and the solid part behind the drains. They're old so they're either a factory option or a long ago addition. Probably 8-10" in diameter. They are pretty nice to have especially when bolting down the cover (how the heck to you reach the underside of the bolts that are furthest aft?). I definitely have more like 20-24 bolts...they probably reduced them from complaints. I'm getting faster, and just replaced the bolts this year with shorter ones but it still takes a good 30 min for on or off. Longer for on because they need to be sealed. I use butyl tape as of this year.

No I have a 97' yanmar 1GM10 so I have no opinions on the matter other than the Yanmar advisory seen here. I'll say that I tend to doubt it makes much difference either way but given that different manufacturers seem to be about 50/50 and we all basically agree on the drag issue I would let it spin unless you can find specific information otherwise.

EDIT: On second thought if the holes were an addition it was probably during the re-power. Anyway they are nice to have, you could consider adding them.

Last edited by asdf38; 09-14-2012 at 05:51 PM.
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Old 09-14-2012
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Re: Propeller Drag - Challenging my intuition

Jordan, thanks for starting this thread, I obviously hadn't got around to it yet.
And thanks to Maine Sail for putting in the time for this research.
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Old 09-14-2012
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Re: Propeller Drag - Challenging my intuition

Have you ever done a test your self? It is real easy, you sail with it in gear, then out of gear, look at the GPS speed. It's not to hard.
Brad
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