Amazing Underwater Photos of an Anchor Swivel Failing

[DoubleWhisky]

Originally Posted by downunder

Now then you have shown us photos with at least half a dozen.

They were chics, not mermaids, downunder

My suspicion is the real Mermaids dig monohulls

[Cotemar]

Originally Posted by DoubleWhisky

They were chics, not mermaids, downunder

My suspicion is the real Mermaids dig monohulls

I always have plenty of women aboard, but never Mermaids. Noelex has a catamaran and a Mermaid. He is taking the game to a higher level.

Hope I do not talk in my sleep. My wife might not like me saying I wish I had a mermaid in the middle of the night..........

[DoubleWhisky]

Originally Posted by Cotemar

I always have plenty of women aboard, but never Mermaids. Noelex has a catamaran and a Mermaid. He is taking the game to a higher level.

Hope I do not talk in my sleep. My wife might not like me saying I wish I had a mermaid in the middle of the night..........

I learnt that You can have plenty of women aboard OR a Mermaid.
The choice is Yours

Just from the avatar photo i thought the Noelex' boat is monohull...
It look pretty like a yacht...

[Pelagic]

Originally Posted by Jim Cate

And FWIW, from casual inspection, the swivel is beefier than any other component of the system, and yet it is the thing to fail. Leads to the suspicion that it is of dubious heritage (ie, born somewhere in China).

And one has to wonder: with such a poor anchor design, set it what appears to be fairly loose sand and with only the rather small flukes buried, how come it didn't drag visibly during a stress cycle vigorous enough to straighten out that thick s/s bar. Possibly stuck on a sub-surface rock? Who knows...

So very interesting!

Jim

Hi Jim,

Looks like the skipper did not bother to set.

Also these type of large vessel anchors and chain depend more on sheer weight of ground tackle rather than digging in.

I have seen a sample before of a failed swivel and it was at the same point just below the swivels' shoulder.
Don't know why other than the swivel pin's hole accelerates corrosion and this is where the torque is greatest?

[DeepFrz]

The fact that he wasn't using a snubber put tremendous loads on the anchor gear. A snubber takes an amazing amount of shock load off the gear and the boat. I would bet that had he used a snubber the catenary of the anchor line would not have straightened at all.

Amazing photos. Thanks for posting.

[Wotname]

Originally Posted by noelex 77

My mermaid took these photos and she has documented something I never thought I would see. An anchor swivel opening up and failing in real conditions.

Has this mermaid any sisters (preferably an identical twin)?

This progression occurred over an hour and we both pleaded many times with the (I think) professional skipper to take some action. We managed to convince him to take a dive and see for himself, but he deemed it a problem to be solved after lunch.:bang head:

You need to find better neighbours. BTW, was this skipper greek?

……….
Finally, if a mermaid swims over and expresses concern, listen to her even if you are a professional skipper. She may know much more than you think from her sleek exterior.

Well, let me say that if your otter like mermaid surfaced beside me bearing such tidings, I'd be asking her kindly to slip back to the seabed with a handful of shackles to jury rig the rode etc while I prepared her a G&T and a plate of canapés

Boatie would have at least invited her on board for lunch

Yep, I think so...

Very impressive timing, very impressive photos and all round a great post. This is what makes CF stand out from the interwebby crowd IMHO.

[downunder]

Nolex,

Your mermaid is certainly progressing with practise on her anchor shots. also shows the value of a camera in a housing and the user practicing their skills.

Great shots.

Shows the value and advantages of having a diver on board, a real advantage when cruising.

Cheers

[downunder]

Originally Posted by DoubleWhisky

They were chics, not mermaids, downunder

My suspicion is the real Mermaids dig monohulls

How good is it to have a chic on board who is a mermaid.



The way to go.

[DoubleWhisky]

Originally Posted by downunder

How good is it to have a chic on board who is a mermaid.



The way to go.

Yes, yes, yes!!!

You are right

[S/V Alchemy]

Originally Posted by noelex 77

I think in this sort of situation we are better to try and learn some lessons rather than lay blame.

Well, it's not really to assign blame so much as to better enforce a shunning.
The initial arrongance of the pro skipper isn't as surprising to me as is the failure to notice the about-to-fail shackle and the clear problem of dissimilar metals in ground tackle. I'm sure the actions of your wife and yourself kept what would have been a horrible warning back at the level of cautionary tale.

One of the reasons I think it's great to dive on your own anchor is not just to observe how you've hooked in and potential nearby problems, but to see the anchors of others and to judge if it's worth it to stay close to their future issues, if they are already set up.

[Jim Cate]

Originally Posted by S/V Alchemy

...

The initial arrongance of the pro skipper isn't as surprising to me as is the failure to notice the about-to-fail shackle and the clear problem of dissimilar metals in ground tackle....

Alchemy, are you trying to suggest that this failure is due to dissimilar metals in the ground tackle?

If so, could you please cite some reference to stress/crevice corrosion in stainless steels being promoted by such a situation? I was not aware of this connection.

Jim

[S/V Alchemy]

Originally Posted by Jim Cate

Alchemy, are you trying to suggest that this failure is due to dissimilar metals in the ground tackle?

If so, could you please cite some reference to stress/crevice corrosion in stainless steels being promoted by such a situation? I was not aware of this connection.

Jim

My pleasure. I own a steel sailboat and had to get better informed on this topic. Here's a brief primer on the different types and causes of corrosion in stainless: Article: Corrosion mechanisms in stainless steel and here's an old if illustrated document from the oil industry, who have a variety of metals in contact in electrolytic fluids: https://www.slb.com/~/media/Files/re...494/p04_18.pdf

Here's a pretty basic Boat US article, which demostrates that there's a number of places on a boat where stainless and other metals can quietly fail: Types of Marine Corrosion - BoatTECH - BoatUS

But the book I return to time and time again (if you REALLY want to learn and remediate) is Nigel Warren's Metal Corrosion in Boats. It sits on the same shelf aboard as do the works of Calder and Gerr.


This will get you well-grounded (pun intended) in the subject, which, for obvious reasons, I find compelling. But I've still never seen "as it happened" photos like the one Noelex's Mermaid got. That's amazing stuff. I hope this has been helpful.

[robert sailor]

It was always my understanding that stainless steel could in fact develop crevice corrosion when linked to ordinary steel but it had to be underwater continuously which an anchor never is??

[akkebeng]

A faulty welding?

[donradcliffe]

I doubt the dissimilar metals had anything to do with the failure. I've used SS anchor shackles for decades with no corrosion problems. In addition, the failed part was hooked to SS shackles at both ends, so it didn't see dissimilar materials itself.