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      A Few Simple Rules   05/22/2017

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wristwister

ID this folding prop please

23 posts in this topic

My Tartan 30 currently has a 2 blade fixed prop mounted (see 1st pic below), but it came with an extra 2 blade folding prop (see 2nd & 3rd pics). The boat is on the hard now for bottom paint and other stuff, and while it's out I'm considering swapping on the folding prop. Lots of good info on SA regarding fixed Vs folding props. I understand I may have to goose the throttle to unfold in reverse, but otherwise motoring performace shouldn't be affected, and I'll be pleased with the sailing performance.

 

Question, can anybody identify the make of this folder? It's geared if that helps. Pros/cons of this particular prop? Any other words of wisdom I should consider before making the switch?

 

Thanks

 

gallery_35769_392_13699.jpg

 

gallery_35769_392_6083.jpggallery_35769_392_2456.jpg

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^^ those are terrible pictures. Can you post something bigger and better exposed?

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It looks like your camera lens is heavily smudged. Try cleaning it before taking the next photos?

 

It looks vaguely like a Flex-O-Fold.

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Yeah, those pics came off my phone, not great. Here's the full resolution version of one of them if this helps:

 

gallery_35769_392_513704.jpg

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Allen, thanks for sharpening that picture up. That helps.

 

FB, those holes appear to be pivot pins for the blades, although they're not normal set screws. The heads follow the contour of the hub, like maybe they were fastened then ground down flush with the hub.

 

I've got 5 days before I have to make the decision whether to keep the fixed prop on or swap on this folder. Any other ideas/opinions out there?

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FB, that HSN prop looks close, although the folded up view doesn't resemble mine, see below. With my prop the blades mesh right together when folded, where the HSN prop the maintain their different profiles. This brings up new concerns though. My blades seem to have considerably more material that that HSN, meaning more weight, more centrifugal force, more likelyhood of failure? Also, my blades don't appear to have nearly as agressive a profile in reverse as that HSN.

 

 

HSN prop closed:

gallery_35769_392_431.jpg

 

My prop closed:

gallery_35769_392_2456.jpg

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Allen, thanks for sharpening that picture up. That helps.

 

FB, those holes appear to be pivot pins for the blades, although they're not normal set screws. The heads follow the contour of the hub, like maybe they were fastened then ground down flush with the hub.

 

I've got 5 days before I have to make the decision whether to keep the fixed prop on or swap on this folder. Any other ideas/opinions out there?

 

My question was about the tops of the pivot pins themselves. Yours look like there is something screwed down through the tops of them, which would be unusual and why I posted a pic of the HSN prop (which I have never come across in real life.)

 

I don't understand your hesitancy to use a folding prop. "More likelihood of failure"? Are you under the impression that folding props are prone to failure?

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Thanks FB. I'll take a closer look at those pins later today and see if I can add clarity

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I think the choice between fixed and folding comes down to where you want to optimize your performance. If you just motor out of the slip and back and the only time you do extended motoring is if the wind quits on you, use the folding. If you motor early each Saturday morning over to Catalina and take a comfortable sail back on Sunday afternoon, use the fixed prop. If you race, I think you get an allowance for a fixed prop, not sure about your area, but that becomes a decision probably favoring the folding just because it is always better to be in front in a race.

 

I faced the exact same decision a few years ago. My boat had a 3 blade fixed and an old 2 blade folding in the locker. I put the folding on and never looked back. When it was time for the new engine and new prop, I went with a Martec and love it. I can't go backward though but it will stop the boat -- eventually.

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My blades seem to have considerably more material that that HSN, meaning more weight, more centrifugal force, more likelyhood of failure?

I wouldn't worry too much about mechanical failure from the weight. Your prop looks like a quality geared folder. I think the difference in geometry you note is a trade off between drag when folded and efficiency when motoring. Yours being the less draggy when folded but somewhat less efficient when motoring type.

 

If the prop is the right size and pitch for your engine, has the right taper and nut for the shaft and if you can figure out how to zinc it in your setup it looks like it should work.

 

PS -- http://www.flexofold.com/2-blade-racing-propeller/ shows the racing and regular geometries for two bladed folders.

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Radice, in France, is the closest I found. http://www.elicheradice.com/eliche-a-2-pale-pieghevoli/&m58LangNew=ENG

 

 

 

I'm surprised there's no name punched into the bronze somewhere. The name on my Max was hard to see until I buffed it up.

 

The French prop you linked to has set screws mounted in the hub tang ends. The OP's prop does not. It is possible, however that the OP's prop is an older version.

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Radice, in France, is the closest I found. http://www.elicheradice.com/eliche-a-2-pale-pieghevoli/&m58LangNew=ENG

 

 

 

I'm surprised there's no name punched into the bronze somewhere. The name on my Max was hard to see until I buffed it up.

 

The French prop you linked to has set screws mounted in the hub tang ends. The OP's prop does not. It is possible, however that the OP's prop is an older version.

 

That's what I thought, the hub taper is wrong too...but the blade design and mass seems close.

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My question was about the tops of the pivot pins themselves. Yours look like there is something screwed down through the tops of them, which would be unusual and why I posted a pic of the HSN prop (which I have never come across in real life.)

 

I don't understand your hesitancy to use a folding prop. "More likelihood of failure"? Are you under the impression that folding props are prone to failure?

 

Yes, the tops of those pivot pins have set screws securing them in place.

 

The service guy who's doing my prop shaft seal had a look at the prop. He said he hadn't seen one like it before, but it looked like a well made unit. He did question how this prop would propel the boat in reverse, as the reverse spinning profile of the blades is quite flat. He also mentioned a zinc problem, as the end nut on the shaft is the likely location for a zinc (boat's got no zinc whatsoever right now), and that wouldn't work with the folder.

 

My "strength" hesitance has to do with pics I saw somewhere of a folding prop blade busting off and punching a hole through the hull. That would suck, although I realize such a failure is probably rare.

 

So ... I'm leaning toward keeping the fixed prop on for several reasons:

 

1. I don't race this boat, other than the occasional beer can regatta

 

2. This is a cruising boat for the Puget Sound, where winds are fickle and sailors tend to spend much more time motoring than they'd like to.

 

3. Right after the boat splashes back in I've got a 2 day cruise with the wife and friends to take her to her new slip (Anacortes). Not the time to discover I made the wrong decision.

 

4. When vertical, that fixed prop seems to be well shrouded by the keel. I'll mark the shaft and hand turn it from inside if I want to reduce drag.

 

5. I can always swap props later while the boat is in the water.

 

Thanks again for the advice everybody.

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^^ sounds like a good decision but one thing needs to be pointed out. If your existing prop is bronze, you must have a zinc to protect it from the stainless shaft. These are usually installed forward of the prop on the shaft itself, not on the nut. If you cannot fit a zinc, the prop is going to be ruined in a year or two. A good alternative in that case would be a plastic prop.

 

Allen

 

aftend.jpg

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In 1985 I bought a French boat, a Feeling 920, in England. I don't remember if it was original equipment or was fitted by the dealer, but it had a geared folding prop like yours. It eventually fell apart and I was only able to recover one blade. Other than that it was a fine prop, worked very well in reverse. The only other problem was that there was a slotted link plate that connected the blades. when the blades opened the boss on the blades that rode in the slot would slam into the ends of the slot. This would eventually distort the link plate causing the blades to stick and not open properly. Every couple of years I would remove the link plate and touch it up with a file. Other than that it was fine.

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^^ sounds like a good decision but one thing needs to be pointed out. If your existing prop is bronze, you must have a zinc to protect it from the stainless shaft. These are usually installed forward of the prop on the shaft itself, not on the nut. If you cannot fit a zinc, the prop is going to be ruined in a year or two. A good alternative in that case would be a plastic prop.

 

Allen

 

aftend.jpg

 

 

 

There are more than one kind of corrosion from which an anode will protect your running gear. You've described galvanic corrosion but far more common is electrolytic corrosion (pictured above, unless I am very much mistaken.) The OP has plenty of room for a prop nut anode, assuming there is not room for a shaft anode.

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I wrote an article on the subject if you are interested. It is hard to say if the corrosion on the prop is from stray currents or from the lack of a zinc. Either one can ruin the prop. I am an electrical engineer and have had an interest in bonding and corrosion for a long time. I would guess that the prop in the picture was subject to electrolytic corrosion. By the way, you only get that if you have a faulty AC ground system, which most boats have because because isolators are expensive and boat builders like to leave them out.

 

http://l-36.com/bonding2.php

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This prop is not a Gori. Nevertheless, the way the Gori is made, is that there is a rubber bushing bit internal to the housing which isolates the shaft from the prop itself. It may be that this prop is done similarly.

 

BTW I have on my port engine what the Gori rep thinks is an original prop, which would make it 20 years old. Folders are just fine if cared for

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....the way the Gori is made, is that there is a rubber bushing bit internal to the housing which isolates the shaft from the prop itself.

 

This is true for Gori saildrive props only. Not the case on other Gori props.

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