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Old 06-07-2006, 08:41   #16
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My understanding is that as long as the engine's transmission has it's independent oil reservoir, freewheeling the prop under sail is OK. My Yanmar manuals actually address this, and recommend it. The prop performance charts I've seen (MIT study) concerning the drag of a freewheeling, 2 bladed prop under sail, show that it's a non issue.

The only time I would imagine that a 3 bladed prop would be considered is if you own a motorsailor,in which case it's a good choice, as the drag under sail is prohibitive.

As for the folding props... they'd be great when there's the possiblity of snagging a crab trap, or if your drive train prohibits freewheeling. If you are able to freewheel, in my opinion there's not much of a cost / benefit ratio.

Rick in Florida
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Old 06-07-2006, 10:36   #17
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We carry 2 3 blade fixed props on our Voyage 380. A recent Yanmar tech release for the sd20 recommended neutral when sailing as in reverse casues excess wear on the plates.

That said we have sailed in neutral and have jumped up 1/2 to 3/4 of knot on average.

The voyage base in the BVI's has switched all of their boats to the 2 blade fixed and report good motoring and sailing. We will be changing to the 2 blade as well.

The cost of the props and the additonal speed vs a fixed seems to be high. If I were a racer, it would make sense. But even traveling in the Caribe the speed difference would have to be large to make a difference in passagemaking and hardly worth it in sailing in the Bay.

Our friends on Rhapsody, a Sewind 1200, have a pair of folding props and the have jammed with growth. Repeatedly. Next haul they are planning on switching.
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Old 06-07-2006, 10:59   #18
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Here's the MIT study. It's worth a look before you spend the money.

http://thepracticalsailor.com/Files/.../propeller.pdf
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Old 06-07-2006, 11:50   #19
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My main objections to freewheeling the propellor are 1) picking up lines, lobster pots and other rubbish (yes there are a lot in my area) and 2) I find the noise irritating. I have actually not found any difference in speed under sail.

Thanks for the report: it does seem to be restricted (as all reports have to be) in method (various problems with simulating reverse and freewheeeling props) and coverage (3 blade folders? Other makes?). Also it mentions the benefit of the autoprop is less than expected because of 'restictions due to hull speed'. As we know, this is less of an issue with cats (OK, some cats) due to high LWL:Hull beam ratio, so does this affect the results? Anyhow, useful report, but does not replace experience from the field! (or 'sea' I guess)
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Old 23-07-2006, 22:16   #20
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f ixed 3 bladed props 2 for $500
folding 3 bladed props 2 for $4600 - $5900

Plus maint....


I know a couple people didn't pay that much for there boats! ;-)
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Old 26-07-2006, 19:43   #21
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Flex-O-Fold

I had the boat for two years before installing two blade Flex-o-folds on my 2GM20 with SD20 saildrives, and heading to Trinidad and back. The performance improved over the original fixed two blades, and backing up was fine. I believe performance was better when sailing and while running only one engine as well.

However, only when I entered the Bay of Fundy and struggled in frigid water filled with lobster pots and buoys did I find the great extra! If I saw the rope in time, and didn't wrap the line too hard, I could cut myself free of the trap and re-install the buoy, unravel the line, and remove the mess with a boat hook while leaning over the back steps with a mask on. Once untwisted and loosened, I could pull the line off the folded prop. Anybody want some slightly used polypropylene?
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Old 26-07-2006, 21:10   #22
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Anyone have thoughts on Varifold?
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Old 27-07-2006, 15:26   #23
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Hmm i am also not sure if i should let my 2blade fixed props on saildrives at my 3ym30 Yanmars spin freely, or put in reverse gear like it was suggested by a few people.
I heard there is too much wear on the transmission when it is turned without oilpressure ???
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Old 27-07-2006, 18:23   #24
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If your sail drive has a separate oil resevoir for the tranny, it doesn't depend on the engine oil pump for oil pressure. In this case you can freewheel the prop when sailing as the transmission is lubricated at all times. If not, you need to put it in reverse.

Rick in Florida
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Old 28-07-2006, 03:43   #25
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The only way to get it right is to check with the manufacturer of the gearbox.
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Old 28-07-2006, 04:14   #26
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Okay, will read through the Yanmar saildrive manual ! Thanks !
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Old 28-07-2006, 10:18   #27
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kiwiprops

Hi, everybody. (I'm new to this great forum)

Had anybody used these ones?

http://www.kiwiprops.co.nz/

In theory they are perfect (free independent lightweight feathering blades) but would like to hear some experienced comments

Juan Josť
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Old 28-07-2006, 13:45   #28
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I have heard good comments about them, but alas, they don't do anything over a 50hp engine rating.
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