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Old 09-01-2008, 20:17   #1
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Props - Feathering or Folding?

Hi all,
This is our first experience with saildrives on our 37'cat. We've been mono-hullers for 30 years, and we finally got smart.
We are considering changing our props to either feathering or folding.
We would DEARLY appreciate any input into the pros or cons of either.
If anyone has any brand recommendations, we'd love them too.
We have twin 18 hp Yanmars with Yanmar saildrives.
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Old 09-01-2008, 22:48   #2
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The general consensus seems to be that
i) Folding props have the least drag when sailing but also the least thrust when motoring
ii) Feathering props have slightly more drag when sailing, but a fair bit more thrust when motoring
iii) Feathering propos are usually slightly more complicated than folding props, which makes them more expensive.
iv) Folding propos may exhibit more difficulty in tight manouvering than feathering, particularly in reverse.

I currently have a 2-blade feathering prop. I do a mixture of low-key racing and cruising. When I can get the cash together I intend to change to a 3-blade feathering prop... I think the improved motoring performance will outweigh the minor decrease in sail performance.
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Old 10-01-2008, 00:04   #3
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"We've been mono-hullers for 30 years, and we finally got smart."

Welcome to enlightened sailing!

The Kiwi prop may not be the best for your app I just like the graph on their website:

http://www.kiwiprops.co.nz/images/drag.gif

The 3 blade max prop has just about a flat drag line through 8 kts. I think you would have a hard time telling the difference between it and a folding prop under sail, and the manuverability in reverse will make a believer out of you.

Kiwi props might have an advantage when the prop shaft is at an angle so it probably has no advantage for you.

The max-prop is a real beauty.

I fully agree with weyalan
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Old 10-01-2008, 10:37   #4
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Hi Exhale, and wecome to the fold.

Weyalan covered the major points.

I have Volvo folders that were already on my boat when I acquired it. Prior to this, always planning to have either feathering or folders on whatever cat I ended up with, I had a bias to feathering props. Reverse thrust that would tend to make the prop fold in upon itself seemed to be a huge performance contradiction to me. But the first time I backed down my (future) boat on the sea trial I became a believer in folders - at least Volvo folders. Very impressive reverse performance. Somehow, they work very well.

Some claim that folders in forward are better than feathering in forward, because they more closely mimic fixed prop geometry (in forward). Maybe, maybe not. Feathering props in reverse are claimed by some to be better even than fixed props in reverse because their geometry in reverse better mimics fixed props in forward. (Fixed props are typically designed to be better in forward for obvious reasons.) In other words, forward & reverse geometry of featherers can be identical - neither being optimum.

Just consider this a data point that claims that folders do not (cannot) perform in reverse may be exaggerations. As Weyalan noted, featherers should be better in reverse - and should even be better in reverse than fixed props. If I ever need to replace my props I'd consider all comers as you apparently are. Good luck.

Dave
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Old 10-01-2008, 13:25   #5
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We had a folding prop on our 120S saildrive and were not impressed with the forward performance - 3.5 kts @ 10hp

We changed to a feathering MaxProp Duo and it is like night and day. We get 5.5+ kts in forward and the reversing performance is astounding. We didn't have the comparison to realize that reverse performance was weak.

It was the singular best improvement we made on the boat.
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Old 11-01-2008, 06:35   #6
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Hmmmm...
OK, so it "seems" that there is more favoring towards feathering. I suspected that there wouldn't be THAT muich of a difference between them, once a change from fixed had been done, but I had heard that one might expect the occasional "issue" with regards to the prop working properly when first shifting INto reverse.
Any "brand" recommendations (for feathering) offering signifcant cost savings without sacrificing performance????
John
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Old 11-01-2008, 07:23   #7
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We've had both, feathering (Max Prop) and folding (Martec) and I have driven a lot of boats that have other props. I think the setup is the key, any drive combination from a good prop maker should work.

Our boats with folder have always had very good reverse and could haul the boat down from speed in a hurry, same as the feathering props.

Other boats I've driven with identical setups to our boats couldn't get out of their own way. This would indicate you can have a bad setup with a good prop, maybe over/under ptiched, maybe the wrong gear ratio, maybe too small/big a prop....

Anyway, make sure you install the right prop (pitch, diameter) for your set up, folder or feathering should not matter.
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Old 11-01-2008, 08:50   #8
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We've had Flex-o-Folds for six years. Performance is great - very good in reverse. No problems whatsoever. Agree with Joli; proper pitch is really important - worth doing a LOT of research before you buy.

Tom
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