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Old 08-05-2014, 15:08   #1
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Folding vs feathering props

There are a couple of important questions I need to get some experienced input about, regarding folding vs feathering shaft props, before replacing our fixed ones on our Prout 50 Quasar. We have some problems to decide which will be the over all best for our purpose, which is blue water cruising for long periods in various waters.
We have he same price on Flexofold as on the Featherstream, so it is mainly a matter of the practical issues.
First, how much problem is the low reverse thrust on folding props. We already today need to use a lot more rpm on reverse than on forward when turning, because of the lower reverse gear on the Yanmar gearbox.
Secondly, how large is the problem whit catching various things with a feathering propeller when sailing?
Third, how much difference will a rope cutter do, to lower the risk of getting something in the rotating propeller?
...and fourth, and other important thoughts...?
Thanks.
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Old 08-05-2014, 15:34   #2
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Re: Folding vs feathering props

there are lots of past threads on this

I have had both a FlexOfold and A Max Prop and am happier with the FlexO Fold because it has better power and is more efficient (better fuel economy) in forward and I haven't noticed any difference in reverse between them. And the FlexOFold was like $1000 less expensive.

Far as cutters, I've never caught a pot in the prop. Have caught them on the keel, but never the prop.
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Old 08-05-2014, 17:06   #3
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I have a max prop and it's pretty awesome having full thrust in Reverse especially if you travel inter coastal. If your shaft is rotating the props not completely feathered. It seems to me a feathering prop has to be designed to close together and wouldn't be as efficient. Maybe sailorboy1 got better results with a feathering prop instead of a max prop because it had a different pitch. But that's just speculation. I guess it comes down to what's more important having full thrust in Reverse or having less possibility of fouling on crab traps. if the price is the same
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Old 09-05-2014, 04:53   #4
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Quote:
Originally Posted by sparrowhawk1 View Post
I have a max prop and it's pretty awesome having full thrust in Reverse especially if you travel inter coastal. If your shaft is rotating the props not completely feathered. It seems to me a feathering prop has to be designed to close together and wouldn't be as efficient. Maybe sailorboy1 got better results with a feathering prop instead of a max prop because it had a different pitch. But that's just speculation. I guess it comes down to what's more important having full thrust in Reverse or having less possibility of fouling on crab traps. if the price is the same
Oops totally screwed that up. Replace feathering with folding the second and third time I used it
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Old 13-06-2014, 01:11   #5
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Re: Folding vs feathering props

I would personally stay away from any folding prop for ocean cruising, because of the reverse thrust issue. The other point of importance is strength and reliability, if it flies to pieces at the wrong place/time, you can have a major or even final problem.

The mostly synthetic feathering Kiwi-Prop has become quite popular due to its low cost and comes with a spare blade. Well... not for long distance cruising as far as I am concerned, but this is just my opinion.

I can't see a feathered propeller catching any more than a fixed one for example and it is quite difficult to get tangled up there if the propeller is not turning anyway.

I have a Max-Prop here and a rope cutter in front of it, floating ropes like polypropylene can get sucked under quite easily when turning or manoeuvring. In the end, I think it is a matter of preference and what you see as most important in relation with your cruising plans.
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Old 13-06-2014, 02:53   #6
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Re: Folding vs feathering props

My boat came with a saildrive and feathering prop. Reverse thrust was dismal and forward thrust yielded something like 3.5 knots.

I was gifted a used Max Prop. After a couple of trials to get the right settings it is phenomenally different. 5.5 knots in forward and more thrust than I can use in reverse without the tiller being snatch away from me. It was like having a completely different boat. Single best upgrade I ever made including autopilot.

Panic stops when docking are possible now.

The problem with folding is the more you gun them in reverse the more they want to fold.

I won't get into a debate - maybe modern designs have overcome the laws of hydrodynamics but feathering is the way to go. As for snagging stuff? How do you handle now? Rope cutter and still once in a while you will have to dive under.

The "bigger and heavier" the boat, the more I would appreciate "positive thrust" of a feathering prop, I am sure of it.
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Old 13-06-2014, 03:16   #7
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Re: Folding vs feathering props

I changed from a volvo 3 blade folding to a Max-prop. We had serious issues with excessive propwalk and damned little revers. Reverse was so poor that stopping in a crowded marina was entertaining to say the least.
It was also difficult to set an anchor properly (because of the propwalk)

The maxprop has virtually eliminated the propwalk (I almost wish it had some more) and reverse is sull blow. Stops the boat on a dime

So I'm very happy with my maxprop, although I have some issues with it not feathering properly.

You can read about that in this current thread:

Maxprop - Issues with Feathering - Page 2 - Cruisers & Sailing Forums
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Old 13-06-2014, 03:37   #8
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Re: Folding vs feathering props

Quote:
Originally Posted by Ex-Calif View Post
My boat came with a saildrive and feathering prop. Reverse thrust was dismal and forward thrust yielded something like 3.5 knots.

<snip>
Crumbs!

That should read folding prop. Missed the edit window :-(
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Old 13-06-2014, 03:39   #9
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Re: Folding vs feathering props

It's a tough choice for cat drivers because you've got twice the number of props so twice the drag. Many cats have folders, rather than feathering props, because of this. I think there are folding props which have decent reverse. There are some tests on the web if you google around. IIRC, there was a really good German test a few years ago which tested thrust versus rpm in forward and reverse, and drag when feathered or folded, of nearly all props available for sailboats.

As to rope cutters: If you get a rope around your prop at a moment when you need engine power, you are stuffed. You not only lose engine power, but it's possible for a rope in your prop to rip out the stuffing box and sink the boat. This situation can and does lead to loss of boats and even lives. So I would not want to cruise without a good rope cutter on the prop shaft. I use an Ambassador Stripper, and it has saved my bacon a couple of times. This problem is not quite so bad for cats since you have another propulsion system, but even on a cat, I would not want to be without rope cutters.

Like Sailorboy, I've not actually had a pot rope in my prop, but had one on my rudder once, which was quite a lot of trouble as it happened in the Channel Islands with a wicked tide running. But I've run into discarded bits of rope and net, and once got the end of one of my own pile lines into my prop. Thank God for the cutter.
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Old 13-06-2014, 03:46   #10
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Re: Folding vs feathering props

I've not had a rope in my prop, but a couple of years ago, a boat came into the harbour we were in under sail (blowing pretty bad that day). The crew did an ok job of landing (bit of a smash against the pier), but had to sail in because they had a rope around their prop. I always carry full scuba, so I ended up spending the better part of an hour under water cutting away the rope for them.

Convinced me that the investment for a rope cutter was minor
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Old 13-06-2014, 03:58   #11
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Re: Folding vs feathering props

This subject has been beaten to death here on CF and elsewhere. This is my summary of information.

The data show that folders vary in their reverse thrust numbers, so anecdotal condemnation is meaningless. IN particular, the Flex-O-Fold three blade folder has excellent thrust in reverse.

The data also show that feathering props are inherently less efficient than other types because their design requires the blades to not have twist in their shapes. No getting around this, and it can be significant. On our previous boat we switched from a good two blade folder to a three blade feathering prop. The static thrust in reverse was definitely better... but the fuel economy was reduced by a measured 25%. This is directly attributable to the inefficient blade shape. Many feathering props allow easy pitch adjustment, and that can be a plus in fine tuning engine loading. In the sizes that most of us use (16-20 inch diameter) the large hub diameter of most feathering props adds to their inefficiency.

In another thread on CF, some folks report difficulty in getting MaxProps to feather correctly. We never had that problem with our Auto Stream feathering prop, but it seems to be an issue with some designs. The absolute drag of folders is usually a bit less than similar size feathering props, but that is not a big factor for us cruisers. Finally, in general, folding props, especially the F-O-F are less expensive than the equivalent feathering prop, especially the MaxProp.

IMO, the sole advantage of feathering props is greater static thrust in reverse. To us, this is not an overwhelming advantage. Sure, it is good when you are stuck in the mud bank, but this is not a major factor in my choosing a prop.

Cheers,

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Old 13-06-2014, 04:50   #12
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Re: Folding vs feathering props

I replaced my Max-Prop with a Flexofold prop and have been extremely satisfied. We caught lobster pot warps all the time with the Max-Prop. We caught one and only briefly with the Flexofold. And much better performance with Flexofold.
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Old 13-06-2014, 04:56   #13
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Re: Folding vs feathering props

Over the last 18 months we have been getting used to our Autoprop which is a type of folder and it seems to be very good in both forward and reverse.
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Old 13-06-2014, 04:59   #14
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Re: Folding vs feathering props

I have also checked the various propeller tests I have found, and come to the conclusion, as already said, that feathering props have good or decent forward thrust and comparably good or very good reverse thrust, but have the higher risk of getting things in the propeller while sailing. The folding props have good or very good forward thrust with better fuel economy and bad or very bad reverse thrust...and have a minor risk of collecting stuff while sailing.
When motoring I guess the risk is equal regardless of prop type.
But...and this is interesting...if the 3 bladed Gori props do what they say, I would get good or very good forward thrust, and almost the same reverse thrust, since they fold 180 degrees instead of 90. A bonus if needed is the "overdrive" possibility. The back side is that they are priced as high as the feathering ones or even higher.
Rope cutters it will be which ever props I choose.
I have a friend though, who has had a couple of Gori on his catamaran for a while, and he is very satisfied whit both the maneouverability in harbour and also the overdrive function with its better fuel economy.
Regarding the various suggestions and opinions, I would guess that it's mostly about what you are used and familiar to, and are satisfied with, regardless of being feathering or folding.
As for me it is mainly about the three issues of reverse thrust, long time motor sailing economy and not getting things around the propeller while sailing.
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Old 13-06-2014, 09:33   #15
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Re: Folding vs feathering props

Quote:
Originally Posted by Ex-Calif View Post
Crumbs!

That should read folding prop. Missed the edit window :-(
I was wondering about that, frankly. I thought "how wrongly sized a feathering prop did this guy install?"

Folding two-bladers are great on race boats and casual cruisers. It's a free extra half-knot in some cases due to the reduced drag. I have a Gori two-blader on my 1970s 33 footer. But they don't have a lot of oomph, nor are they great at stopping the boat. I dock in neutral and step off with lines. The time needed to deploy those blades is simply not responsive enough for me.

Our steel 41-footer has a four-bladed VariProp behind a full keel's "deadwood" (dead steel?). Like the AutoProp and similar featherers, it's all about the stopping and reversing. Folders are in this sense fixed. Feathering props (well, most of 'em) can be set at differing pitches for forward and reverse, although in many boats this will require experimentation. We wanted "econo" cruising for long periods because if we're not sailing, we are motoring right at the sweet spot of relatively flat water...such is the nature of passagemaking. But for anchoring or tight-quarters maneuvering in a marina, you want a nice, torque-y, boat stopping reverse with some authority. Within the ability of your engine and transmission to accommodate that, you can pitch the prop in reverse to obtain that. Nobody needs to make more than 2 knots in reverse, do they?
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