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Old 13-02-2011, 18:59   #46
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The bucket comparison above is a good one. When I think about dragging our 24 inch 3-blade open vs feathered it is about the same as at least one bucket. On ours, the blades are curved and designed for forward. This is reasonable since 99.9% of motoring is forward. I still get plenty of reverse though. The transmission is hydraulic 2.5:1 and the engine turns about 1100 but with the prop flattened out and the engine up to 2500 I get massive thrust.
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Old 13-02-2011, 19:35   #47
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Thanks for the input! Didn't mean to steal the thread, but thought it ws relevant to the discussion.

I think there is some truth to the comments about towing a bucket, but as the wind speed increases, to say 20+ kts, I think you could likely tow a dinghy, or a bucket and still make hull speed. Cut loose the dinghy or bucket, and you are still only doing hull speed, IMHO.

I do totally agree that in lighter winds, it would allow one to reach hull speed, or near, more often that with a fixed prop.
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Old 13-02-2011, 21:22   #48
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The problem on many boats is where the bucket is. The turbulance directly in front of the rudder may cause other unpleasant things to happen. We have all seen every type of boat bottom, prop, rudder & keel layout immaginable. There are a lot of boats with fixed props. They have been arround a long time. The outcome on any particular boat is dependant on many varibles. It is probably more important to feather on small boats than on large considering the drag ralative to power. I wouldn't want to tow that bucket around the planet but it may be perfectly acceptable for the average day-sail in moderate conditions of your choosing.
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Old 22-03-2011, 14:32   #49
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Re: Feathering Prop Choices / Manufacturers

In the end I got 3 blade Flex-O-Fold instead of the feathering prop I was orginally thinking about. In reading every comparison article I could find, even ones in a lanugage I couldn't read except the charts, I came to the belief that the feathering prop's "advantage" in reverse was minor.

And if anyone else reads this: I sent Flexofold 4 emails asking for sizing and pricing and waited 3 months. I finally called them, which they answered, and got the info. And when I told them of the emails they looked them up and found them in less than 5 seconds.......So if you to get an answer from them I recommend to call not email.

Now if they respond to my email about not packing the spare zinc that I paid for all will be good.
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Old 28-07-2011, 09:49   #50
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Re: Feathering Prop Choices / Manufacturers

I love my Volvo-Penta three blade folding prop so much that when we decided to sell Glorious, our Hood Gulfstar Custom 40, I took it off. The new owner will get the original 3 blade fixed prop which I had re-conditioned and balanced. I paid $1050 for it a few years ago. We call it the squid because that's what it looks like folded. I've seen so many MaxProps, AutoProps,etc.; all pitted,seized,tweaked... I wish everyone could experience these wonderful props. The V/P is sitting out in the shed at 5,000 feet in New Mexico, waiting for my next boat to wrap around it.
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Old 28-07-2011, 09:59   #51
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Re: Feathering Prop Choices / Manufacturers

those of us with formosa 41/ct41/seawolf hardin 41 will find the folding / feathering props do NOT fit in the space provided for a prop in our space between rudder and keel. is not a big deal on our boats as there will be no gain with a folding or feathering prop, as in a performance cruiser.
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Old 28-07-2011, 10:09   #52
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Re: Feathering Prop Choices / Manufacturers

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Originally Posted by lancelot9898 View Post
I have a Max Prop on the boat for 25 years now and while I have no evidence to prove this but I think the benefit is as you state is in light air. I know that I can reach hull speed easily in 15 knots towing a dinghy and I would think that would present pretty good drag. Light air performance is enhanced by the feathering prop however two other benefits...1. shaft does not rotate(no need for brake) and 2. much better reverse. The one disadvantage is that there is some efficiency lost in forward since the blades are flat compared to the curved fix blade. Not sure if applicable but upon thinking about that last statement more, I've been in a small speed boat powered with a corvette engine with flat blades.
yep, I've had 4 max props, much better reverse, efficient and never ever had a problem.
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Old 28-07-2011, 10:30   #53
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Re: Feathering Prop Choices / Manufacturers

I agree with Cheechako. The advantage in a folding or feathering prop is only in light air. Apature(sp) in a glass boat such as yours can be changed by any competent fibreglass person to accomodate any change in prop configuration unlike a wood boat without changing the rudder, which also isn't against the law. " Don't be a slave to tradition, Jonathan. If you think a change is a good idea, do it and let others follow you." Jim Egan, 1975
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Old 28-07-2011, 11:05   #54
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Re: Feathering Prop Choices / Manufacturers

The Kiwi prop is good ..In fact i have a good one for sale, make me a stupid offer and you can have it . As long as u pay the freight.


www.byamee.com
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Old 09-08-2011, 07:52   #55
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Re: Feathering Prop Choices / Manufacturers

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I love my Volvo-Penta three blade folding prop so much that when we decided to sell Glorious, our Hood Gulfstar Custom 40, I took it off. The new owner will get the original 3 blade fixed prop which I had re-conditioned and balanced. I paid $1050 for it a few years ago. We call it the squid because that's what it looks like folded. I've seen so many MaxProps, AutoProps,etc.; all pitted,seized,tweaked... I wish everyone could experience these wonderful props. The V/P is sitting out in the shed at 5,000 feet in New Mexico, waiting for my next boat to wrap around it.
I have a 3 blade folding Volvo on my 41 ft cruiser, saildrive. The problem with it has been lack of power on reverse - not enoung accelaration when backing in strong wind take-offs in marinas. When the boat is catching some speed the propellers kicks in, but the wind has already caught the boat. When starting ahead the acceleration is OK and when cruising the Volvo propeller is great, efficient and quiet.

Have you had also such lack of acceleration at the start of backing?
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Old 09-08-2011, 18:45   #56
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Re: Feathering Prop Choices / Manufacturers

Hi Johannula, Quite the contrary to your experience, the V/P not only gave powerful thrust but stopped the 12 ton whale bottom from 6 kns. in two boat lengths in the main fairway at Ventura Harbor and gathered sternway quickly enough to astonish us. So, we did it a bunch more times with pretty much the same results. The Hood design has moderate freeboard without excessive windage; what about your 41 footer? The blades are the same shape as a nuclear sub and doesn't cavitate, which in my humble opinion, is the biggest thief of efficiancy.
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Old 11-08-2011, 14:25   #57
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Re: Feathering Prop Choices / Manufacturers

Hi Jonathan,

what are the dimensions of your Volvo-propleller? Mine is 18x15 and I have just learned that 20x13 would do much better reversing. I was also surprised to learn that cavitation has a large effect on propeller performance in low speed and high power (like fast take-off). The larger diameter propeller is less likely to cavitate. I have a S-drive , so the clearenece will be a problem with large diameters.

When comparing propellers we quite often look just on the brand/type of action and not on dimensions.
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Old 29-08-2011, 09:02   #58
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Re: Feathering Prop Choices / Manufacturers

We did some measurements on our Volvo 3 blade problem of lacking reverse power.

It turned out that those perceptions were right. There is less than 50% power available, when comparing to forward operation. That was obvious both when measuring acceleration from 0 to 3 kn (5 sec fwd , 12 sec reverse ) and pulling test.
We also made an underwater video of the propeller
It shows the reason for lack of backing power. The blades are folding partially and cavitating.

As I wrote before, Volvo is a great prop FWD and you can manage in good conditions by giving more rpms when on reverse, but the top power is not there when you really need it.

There might be some differences between propellers of different dimensions. Perhaps some of them stay fully open and behave well. That would explain Jonathan Reitters good experience.
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Old 29-08-2011, 14:22   #59
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Thumbs down Re: Feathering Prop Choices / Manufacturers

Volvo-Penta three-blade prop have by their curved blades a rather large weight on the outer edge of the prop. Thereby they open quite well when reverse compared to other folding props. But there is a risk if you change from forward to reverse to fast. The gears in the S-drive will break. Learned by practice. http://www.cruisersforum.com/images/icons/icon13.gif
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Old 29-08-2011, 14:40   #60
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Re: Feathering Prop Choices / Manufacturers

Lars_L

The curved blades of Volvo-Penta three-blade prop work two ways: they have a rather large weight on the outer edge of the prop which helps to keep it open by centrifugal force as you pointed out.

They also have most of their area on the outer rim which causes the pitch (and suction force of the propeller) to have more effect in the opposite direction (folding the propeller). As you can see in our video, the folding force is too great on reverse at low speeds.

Perhaps you are doing better, if the propeller has relatively small pitch.
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