Feathering or Folding Prop?

On my old yacht fitted a 3 bladed Autoprop. It was simply fantastic, saved revs, saved fuel, faster under sail and very good when motor sailing. Would have fitted same to new boat, but not enough room with a long keel, keel mounted rudder and cut out for prop. So fitted a 4 bladed Variprop. Excellent thrust in either direction, smooth, swift sailing. Thing is the Variprop locks over for each direction, whereas Autoprop uses centrifugal force to continuously set the right pitch for the revs, speed, resistance and other conditions pertaining at the time. So if your prop has plenty of room, send off for a quote from Bruntons. Can't sing their praises enough, not cheap but actually value for money, oh, and don't worry about the bearings etc, totally up to the environment even on mud moorings.
 
Another vote for Bruntons Autoprop. I fitted it two years ago in place of a fixed three blade prop. Huge improvement. If you ever do any motor-sailing it's fantastic, because the pitch automatically alters to suit.

No connection, just a satisfied customer.
 
I also have been looking to change to feathering or folding.
To me the YM tests showed that the Flex-o-fold was the best folding prop and the Featherstream the best feathering.
YM, as always, bottled out on actually setting out any conclusions, don’t want to offend advertisers presumably.
At SIBS I went to the various suppliers, turned out Darglow make the Featherstream in the UK and are the importers for the Flexofold .
Interestingly, for my size prop, the Featherstream, with the boat show deal, was less than £100.00 more than the Kiwi (which did not come out very well in the tests)
The YM tests also seemed to show that there was little difference if any between the 2 and 3 blade folders.. The 2 blade Flex-o-fold is about £300.00 less than the eathering.
I am still agonising over folding v feathering.
 
Tranona said:
. I suspect also that some of the performance "improvements" reported by some owners reflect their desire to justify the expense rather than reflect reality.
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No doubt, but I can confirm the drag effect of a 3 blade prop. Had one on the Silette outdrive leg of my cat and the difference between sailing with the leg down and the prop in the water compared to the leg up was a consistent 0.5 knots. This is likely to be a bit bigger effect than on a mono because the prop wasnt hidden in any way by a keel and because the cat relied on slim slippery hulls.

On my current boat I have a Radice folder. I can't comment on the drag of it but in other respects it isnt that good. There's a loud clunk on forward engagement, reverse is weak, and engaging reverse when going forward brings a lot of vibration as the blades flap together like the flippers of a performing seal. if it dropped off (please!) I would replace it with a 3 blade featherer.
 
FlyingSpud said:
Interestingly, for my size prop, the Featherstream, with the boat show deal, was less than £100.00 more than the Kiwi (which did not come out very well in the tests)
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can't argue about the tests which were done systematically. But the Kiwi on Tigger is brilliant in reverse: it engages immediately and is very "powerful". I'd go for a feathering one if you are cruising - they don't have to "open up" before working.
 
If you are a cruiser then whatever you do stick with 3 blades over 2.

Other than that there are several good designs, many of which have been mentioned above. All seem to be excellent props and will do the job very well.

My own choice was the Gori 3 bladed folding prop. The particular reason I chose that over the Maxprop/Autoprop was very specific to my installation - I am restricted in the diameter that I can fit and the Gori needs a slightly smaller diameter than the others (probably because the hub is much smaller).

The Gori is first class - does everything you can expect. It has the unusual (?unique) property of opening in the opposite direction when going in reverse, so it presents a properly profiled leading edge to the water in both foward and reverse. That means that it's performance in reverse is actually better than a fixed prop.
 
Oddly, the YM tests showed that for a folding prop, of the size they were working with, the 2 blades were no worse than 3 and sometimes better.

The guy at the Darglow stand at SIBS explained this by saying that on a small prop, the blades are so close together, in effect each blade disturbs the water for the blade behind it, so the prop gets less drive.

I don't know if this is correct, but it seemed possible
 
FlyingSpud said:
YM, as always, bottled out on actually setting out any conclusions, don’t want to offend advertisers presumably.
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YM could have concluded what was we thought was "best" for the test boat. But what would the point be unless you had a Beneteau oceanis 323 and agreed with our views of "best"?

We printed all the results we could fit in. We like to think that with all the results in front of them our readers could make up their own mind. Some want sailing performance, some want motoring performance, some want to increase power astern, some want to reduce prop walk. How do we recommend a prop for you?

No one prop will solve all these problem, and it would be unfair of us to recommend one prop when they all have their gains and loses. The results were there for you to decide whether you want 0.2kt increase in speed and pay £300 for the privilege. The choice is yours.
 
Sorry I know this tread is a bit old now.
I've been researching this quite extensively and have narrowed it down to three props.
The Slipstream folding, the flex-o-fold two and three. I've read the YM test or jest as some manufacturers have callled it.

I have a 1985 Seawolf 30 which is a quick bilge keeler. She is very sensitive to bottom growth and slows down quite a lot with even a small amount of fouling. Taking this into consideration I'm hoping a folding prop with give me at least a knot of sailing speed.

I'm only interested in the slip stream because I have been offered one at the same price as the flexifold three blade and the fact it's stainless. No anode, stronger and lighter(?)

The Flex-o-fold did the best in the limits of the YM test. So despite it not being a comprehensive test logic dictates this is the one to go for. A part from word of mouth which is important but as also mention above biased. EG I was told by a marine engineer at the boat show who had nothing to do with props stay clear of the Kiwi. Yet speak to someone who's got one and they're wonderful. Ask Moody owner which is the best yacht to buy guess which one he will say. Personally I think they're too slow (see what I mean)So this is all we have to go on.

My question is do I need a three blade prop or will a two surfice. My current prop is a 15in 11 three blade. Bob at Darglow said that I would see a big difference with a two blade. Not so much in manouvering, but in power in the rough stuff. He means in really rough stuff when perhaps you just want to get the hell out of there as quickly as possible. Obviously manouvering will be effected but I think one will just get used to this. So has anyone changed from a three to a two?
ps Didn't mean about Moodys.
 
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We've a 3-blade slipstream on our 18ton heavy displacement cruiser and have been delighted with it. We have added (on an average passage) an extra knot when sailing, get more forward power than we did with our old 3-blade fixed - and once you get used to how to bring the power on, she goes astern fine.

Suggest you go the horses mouth - drop Ben Hawke (the boss man) an email - info@seahawk.com.au - ask him what he would recomend. He's a straight arrow and won't bulls**t you.
 
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