Flexofold propeller galvanic corrosion

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Olianta

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Hi,

Last year I purchased a sailboat built 2010. The sail drive is fitted with a Flexofold 2 blades folding propeller. Last year I sailed her from the Baltic to the Black Sea and there was a lot of motoring, appr. 500 hours. When I hauled her out in December I noticed a lot of galvanic corrosion on the shaft as can be seen on this picture.
http://www.ybw.com/forums/asset.php?fid=68336&uid=99012&d=1552078504

I do not see any twin anodes on the propeller itself, like the ones I did have on the Flexofold propeller on my previous boat looking the same as the ones currently offered on their website. https://flexofold.com/folding-prope...llers/48-2-blade-saildrive-folding-propeller/

The Volvo 130S sail drive shaft anode is working but it does not prevent the corrosion on her propeller shaft.

It seems my current boat is fitted with an older model two blade Flexofold folding propeller,

I wrote two letters to Flexofold requesting politely some kind of advice and solution to the problem but unfortunately I did not get any response.

I would appreciate any advice how to deal with the problem.
 

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The older Flex-o-Folds did not have any anodes although my recent 2 blade one does. Perhaps check the resistance between the visible part of the shaft and the hub of the prop. I believe that the two should be isolated but if they are connected it would suggest that the insulation in the hub has been breached.

Richard
 
The link to your prop picture doesn't work for me. However, a recent enquiry by me to Flexofold got a reply the same day. Might check your junk/spam folder if it was emailed. You could also try Darglow as UK agent.
 
RichardS said:
The older Flex-o-Folds did not have any anodes although my recent 2 blade one does. Perhaps check the resistance between the visible part of the shaft and the hub of the prop. I believe that the two should be isolated but if they are connected it would suggest that the insulation in the hub has been breached.

Richard
Click to expand...

I don't think the hub is isolated from the shaft. Certainly not on my flexofold which looks to be identical to the OP's.

to the OP - You mentioned corrosion on the shaft but it looks to me as if the corrosion is on the hub of the prop. The shaft looks ok. Maybe they've not answered because they don't consider the shaft to be their problem. Try emailing again telling them it's the hub that's he problem.
For information I have a shaft anode fitted and also added a hull anode nearby when I fitted my flexofold 4 yrs ago. The shaft anode needs replacing every year and the hull anode every 2/3 yrs. I didn't like their recommend that the prop didn't need an anode so did it my way. Seems to work.
 
I can’t see the OP pictures, either.

I have a 3 blade flexofold. My boat has a hull anode which I have not changed in 5 years.

The Yanmar saildrive leg has an anode which isn’t too eroded after a 6 month season but I always replace it.

The prop has an anode on its nose and this seems to have variable erosion. This season it was almost depleted to the point of being ready to fall off. I paint my prop to try to reduce the cathode surface area. I did a fair amount of motoring early in the season so perhaps washed some of the paint off, promoting electrolysis.
 
greeny said:
I don't think the hub is isolated from the shaft. Certainly not on my flexofold which looks to be identical to the OP's.

to the OP - You mentioned corrosion on the shaft but it looks to me as if the corrosion is on the hub of the prop. The shaft looks ok. Maybe they've not answered because they don't consider the shaft to be their problem. Try emailing again telling them it's the hub that's he problem.
For information I have a shaft anode fitted and also added a hull anode nearby when I fitted my flexofold 4 yrs ago. The shaft anode needs replacing every year and the hull anode every 2/3 yrs. I didn't like their recommend that the prop didn't need an anode so did it my way. Seems to work.
Click to expand...

Sorry, my English was not precise. As you state the corrosion on the hub. I have sent to Flexofold the same picture and one more.
What do you mean by hull anode. Where exactly have you placed it. Can you send a picture?
 
greeny said:
I don't think the hub is isolated from the shaft. Certainly not on my flexofold which looks to be identical to the OP's.

to the OP - You mentioned corrosion on the shaft but it looks to me as if the corrosion is on the hub of the prop. The shaft looks ok. Maybe they've not answered because they don't consider the shaft to be their problem. Try emailing again telling them it's the hub that's he problem.
For information I have a shaft anode fitted and also added a hull anode nearby when I fitted my flexofold 4 yrs ago. The shaft anode needs replacing every year and the hull anode every 2/3 yrs. I didn't like their recommend that the prop didn't need an anode so did it my way. Seems to work.
Click to expand...

Apologises to Richard.
Looks like the saildrive ones do have a sort of inner hub for shock protection and this may also be designed to give electrical isolation as well. As Richard says, if this is breached it may be your problem. Shaft drive hubs don't have this inner hub it seems.
The hull anode I fitted was one of the flat slightly spherical ones that are available at most good chandlers. I fitted it through the hull, as close to the prop as possible, whilst still keeping reasonable access to the inside connection. Line of sight to the item being protected is important. The inside of the through bolt is connected electrically to the boat bonding system. I can't tell you exactly where on your boat because manufacturers approach the bonding system differently and yours may be different to mine. Having said that I don't think I really needed to fit it as it's depletion rate is very slow and it's probably an unnecessary precaution I took.
I would email Darglow in UK and ask for their help if you are still getting no reply from Flexofold. They were very helpful when I bought mine and may well have seen this problem before and have the answer for you.
I can't send photos at the moment as I'm not at the boat but if you still need them in a couple of weeks when I get back just ask. The fitting and design of earth bonding systems is not complicated but can be contentious as different people have different ideas how it should be done. If you google it there's lots of info available on the web. However I do think Richard is probably correct in the first place in saying it may be a hub problem.
 
greeny said:
I don't think the hub is isolated from the shaft. Certainly not on my flexofold which looks to be identical to the OP's.

to the OP - You mentioned corrosion on the shaft but it looks to me as if the corrosion is on the hub of the prop. The shaft looks ok. Maybe they've not answered because they don't consider the shaft to be their problem. Try emailing again telling them it's the hub that's he problem.
For information I have a shaft anode fitted and also added a hull anode nearby when I fitted my flexofold 4 yrs ago. The shaft anode needs replacing every year and the hull anode every 2/3 yrs. I didn't like their recommend that the prop didn't need an anode so did it my way. Seems to work.
Click to expand...

Olianta said:
Sorry, my English was not precise. As you state the corrosion on the hub. I have sent to Flexofold the same picture and one more.
What do you mean by hull anode. Where exactly have you placed it. Can you send a picture?
Click to expand...

A hull anode will not be appropriate in this case because the prop hub of a sail drive Flexofold is insulated from the shaft. For an anode to be effective it has to have an electrical connection to the item it is protecting.

You cannot make an electrical connection to the hub of an insulated propeller. This is why they have to be protected either by the twin anodes fitted on the hub or by a cone or dome type anode fitted between the blades.
 
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langstonelayabout said:
Out of interest, what is an older Flexofold? I bought a new 2-blade Flexofold from Darglow 4 years ago and it certainly didn't have any anodes in, on or around it.

Was my propeller from the 'old' era or old stock?
Click to expand...

I bought my 2-blader from Darglow 2 years ago. None of the promo photos had an anode fitted but mine had a dome anode fitted to the flat end-plate.

Richard
 
I used to have a 2008 boat with a factory fitted 2 blade Flexofold with no anodes. When the boat was sold in 2017 the prop was virtually as new.
However I knew someone who had the same model of boat but a 2010. His nominally identical Flexofold - factory fitted - fell apart in one season.
After a lot of hassle he got a replacement under warranty and had no further problems.
There was someone else on the forum who also got one replaced under warranty - I think it was Little Grebe? I think his boat was maybe 2011. Have a search, there was quite a bit on the forum about it.
There is pretty strong evidence of some bad material in 2010.

Here you go - http://www.ybw.com/forums/showthread.php?467180-Flex-o-fold-propellor-longevity
 
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Mine was 2015, after the sterling efforts of the boat builder's U.k agents flex o fold eventually held their hands up to the original blades being defective.

Whatever was wrong with those blades caused some pitting of the hub similar to the OPs so I now have one of thier new composite hubs. Just cleaned the blades this afternoon and all looks as good as new.
 
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