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Old 25-06-2019, 14:15   #1
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Are folding props worth it?

My PDQ32 is an LRC model with two Yanmar 2GM20F, shaft drive with three blade props (Michigan DJ, 15 x 9, top quality I've been told). When sailing, the trans is in neutral and the props spin freely. What I don't know is how much of a hit in speed I'm taking with these props and how much better folding props would be. If folding props would give me a knot or more in speed it would be worth it to me. Right now, she can do about 6-7 knots in 12-15 knots of wind, beam reach. If I could get that up to 7-8 knots, I would be happy.

What are the estimates on speed advantage for folding props?
Would you make the change?
If so, any recommendations on the brand?
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Old 25-06-2019, 14:22   #2
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Re: Are folding props worth it?

We put a feathering prop on our full keel monohull and I can sure feel the difference in lighter winds. Heavier air it removes the noise of a spinning prop
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Old 25-06-2019, 14:28   #3
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Re: Are folding props worth it?

Hello, Jerry,

I don't know if it would be the same for a small catamaran as it is for monohulls, but for us on one mono, the change from a 3 blade to a 2 blade folder was 1.5 kn boat speed in light air. Towing a 3 blade prop is like towing a bucket behind you. Of course, a mono has both skin friction and weight against it in light airs.

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Old 25-06-2019, 15:23   #4
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Re: Are folding props worth it?

The difference between 6 knots and 7 knots is about 60 seconds a mile. If you look at PHRF a 60 second per mile differential generally equates to about 10 feet of LOA. The impact of a fixed prop on performance is huge.
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Old 25-06-2019, 15:33   #5
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Re: Are folding props worth it?

Quote:
Originally Posted by Jerry Woodward View Post
My PDQ32 is an LRC model with two Yanmar 2GM20F, shaft drive with three blade props (Michigan DJ, 15 x 9, top quality I've been told). When sailing, the trans is in neutral and the props spin freely. What I don't know is how much of a hit in speed I'm taking with these props and how much better folding props would be. If folding props would give me a knot or more in speed it would be worth it to me. Right now, she can do about 6-7 knots in 12-15 knots of wind, beam reach. If I could get that up to 7-8 knots, I would be happy.

What are the estimates on speed advantage for folding props?
Would you make the change?
If so, any recommendations on the brand?
I doubt you will that increase with a folding prop over a free spinning fixed prop. A locked fixed prop maybe, but I doubt for a free spinning one.

But the noise is another issue.

With that said I made 3 purchase right off when I got my current boat
- dinghy davits
- a bigger anchor
- a Flex o Fold 3 blade prop that has never had a problem
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Old 25-06-2019, 16:20   #6
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Re: Are folding props worth it?

I'd agree with sailorboy1 that a knot would be more than I think you would see. For example, PHRF typically gives you 9 seconds per mile adjustment. We were sitting around a table pounding down margaritas wondering how some boats could be so slow and enjoy the 750 mile rally we'd just completed for more than a day more than others. We came up with five guaranteed "go slow" moves to extend your enjoyment. We couldn't agree on the order but fixed prop was near the top. A dirty bottom helps a lot also. Not having a downwind sail will guarantee you get more time at sea. Poor sail trim (generally over trimming when going downwind) and generally just sailing the wrong direction (sailing too high for speed but crushing your VMG, wrong tack etc.)
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Old 25-06-2019, 16:46   #7
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Re: Are folding props worth it?

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Originally Posted by Sailmonkey View Post
We put a feathering prop on our full keel monohull and I can sure feel the difference in lighter winds. Heavier air it removes the noise of a spinning prop


Bingo, exactly. Itís not the speed boost at high winds and speeds that everyone speaks to that makes them worth while.
If your near hull speed, it just doesnít matter, however the difference between 4 and 5 kts is huge, doesnít sound like much, but your going what 20% faster?
For us itís the difference between sailing and motoring
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Old 25-06-2019, 17:27   #8
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Re: Are folding props worth it?

Folding every time, for noise as well as speed. A knot is optimistic, but close to that.
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Old 25-06-2019, 17:48   #9
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Re: Are folding props worth it?

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Folding every time, for noise as well as speed. A knot is optimistic, but close to that.

Lots of boats can't have a folding prop but need a feathering prop. There is not enough room for a folding prop.
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Old 25-06-2019, 18:27   #10
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Re: Are folding props worth it?

I'm not sure but my GUESS is that folding or feathering props would make even more difference to a cat because you have 2 of them for a start.
Don't know the market in USA but see quite a few good used folders for sale cheap locally
Prefer folders on monohulls myself but it depends on wether you prefer sailing or motoring I suppose or your % usage of either mode
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Old 26-06-2019, 01:28   #11
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Re: Are folding props worth it?

We swapped our 2 off fixed 2 blade props for 2 off Radice 2 blade folders. No spinning shafts, boat sails in much lower wind speeds, as A64 says it's the speed gain at 4-5 kts which is significant, increasingly less so at higher speeds. For a PDQ, I would say a no brainer.
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Old 26-06-2019, 09:22   #12
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Re: Are folding props worth it?

Like most things it does depend on what kind of sailing youíre planning. For us cruising we had a Volvo folding prop but have now switched to a feathering prop and itís better still. Make a big difference over distance .
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Old 26-06-2019, 09:28   #13
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Re: Are folding props worth it?

I switched out a pair of fixed three bladed screws for a pair of Kiwi Props on a Lagoon 42 TPI. Lost about 1/2 knot of motoring speed in the same conditions, but gained a knot and a half in 18 knots of true wind. Went up total knots above 20 knots true wind, no discernable improvement in winds higher than that. Easy to maintain and individual blades are easy to replace underwater. If you will be sailing more than motoring, these are the ticket.
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Old 26-06-2019, 09:32   #14
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Re: Are folding props worth it?

First off, feathering (maxprop) is MUCH better than a folding prop.

If you are the typical intracostal cruiser (motor 90% of the time) then no, not worth going with a folding/feathering prop unless you are racing. If you are making long passages, crossing oceans, they are definatly a plus. 1/2 knot is 12miles in a day , or up to 3 hours a day for the typical cruising boat.
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Old 26-06-2019, 10:24   #15
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Re: Are folding props worth it?

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First off, feathering (maxprop) is MUCH better than a folding prop.

Why do you believe that? Just curious.
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