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  #31  
Old 11-25-2012
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Re: Folding prop help

I had Martec folders on the last two boats I've owned and have been happy with their performance. Even cruisers enjoy the extra speed under sail. I would check with Martec to see if you have the right pitch. It seems low for a Yanmar diesel with reduction gearbox. May have been for a direct drive A4.
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  #32  
Old 11-25-2012
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Re: Folding prop help

Don't know about the diesel, but a direct drive A4 would never swing that prop. Probably OK with a reduction drive, but a direct drive, no way.
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  #33  
Old 11-26-2012
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Re: Folding prop help

You may want to consider the feathering prop option. We had a two blade folding prop on 23' sloop we sailed across the top of Oz a few years back and found it took a fair wack of power in reverse to throw the blades open - which is always a white knuckle experience in a small crowded marina!

Mico our 33' Alajuela cutter had a 2 blade fixed prop which, together with the fact her new 39hp engine had been bolted directly to the engine beds, caused the whole boat and our tooth fillings to vibrate something terrible. We have a 2/3 full and deep, integrated keel and at the top of it's rotation, when the blades aligned with the vertical stock of the keel we experienced significant loss of thrust and the subsequent cavitation.

After refitting Mico's engine with new engine mounts and switching to a 3 blade Hydralign feathering prop, she's now as smooth as silk - although we nearly came a cropper when we first reversed out of our pen after putting her hard into reverse as we used to have to do with the folding prop only to discover a feathering prop is equally effective in reverse as it is in forward

Hydralign are a Sydney based company and have a wide range of feathering options at really competitive prices. Mico has an aperture rudder and they were very helpful in matching a prop to suit.

Fair winds,

Mico
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  #34  
Old 06-19-2013
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Re: Folding prop help

Quote:
Originally Posted by jfdubu View Post
IT,
I have the same power plant a and martec folder, 12x6 I think, on my J28,
7500lbs bare. Forward works fine but the motor/prop vibrate a bit at certain rpms. Reverse is a suggestion, not a command. I get 5.5 knots at 2500rpms in forward. Reverse does hardly anything until it actually starts moving in reverse and the blades open up full. Then it moves fine backward.

It sounds like you props may not be opening properly. Any kind of crud will really effect the prop function. A few times I've noticed "bad behavour" with the prop and a quick dive and clean off straightens it out. Based this being the end of the season and may the problem wasn't noticed early prop crud is my guess.

John
Do you think early prop crud will cause the engine to die when placed into fwd?
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  #35  
Old 06-19-2013
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Re: Folding prop help

rope in the prop will stall an engine,i hava a maratec and my thoughts are if your cruising,in a 24 hr day of sailing you will gain an extra 10 miles or so at 5 knots thats 2 hours eariler arrival per day and sometimes at the end of a 40 hour its nice to get in sooner rather than later.if you sail more than motor get a folder,if you motor more than sail get a fixed 3 or 4 or 5
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  #36  
Old 06-19-2013
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Re: Folding prop help

A lot of sailors have the idea that folders are very inefficient.
Someone actually tested it. You may be surpised to see some of the results.

http://www.flexofold.com/upload_dir/...onthly_low.pdf
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  #37  
Old 06-19-2013
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Re: Folding prop help

Quote:
Originally Posted by ltgoshen View Post
Do you think early prop crud will cause the engine to die when placed into fwd?
Not likely. More likely you'll go much slower under power and/or have to run the engine harder to go the same speed.
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