Mooring Swivel

[Neeves]

This is a thought provoking thread.

http://www.cruisersforum.com/forums/f118/lost-our-due-to-a-bad-mooring-swivel-206078.html

There is simply not enough information but the swivel has had a very unimpressive performance.

Its a $28 swivel retaining, or not retaining as the case might be, what looks like a rather attractive yacht. There is little point in using a rated and Proof Tested shackle etc etc if the rest of the pennant is not similarly rated (and the same would apply to an anchor rode).

Jonathan

 

[Kelpie]

A very sad tale.
The remaining part of the swivel looks unworn. I wonder how it failed.
My preference is for a swivel located part way up the riser, and the largest that can physically be fitted to the chain.

 

[Yngmar]

Why is there a hex head on the pin? Is it just a bolt? That would make me very suspicious.

 

[vyv_cox]

That design of swivel is very poor and should be avoided. Relying on the threads of a nut and bolt, even with a tack weld between the two, is asking for trouble. The stainless ones sold for anchoring are very poor and I believe are actually intended for fishing gear.

 

[Neeves]

I don't know this particular swivel, obviously, but I have seen some that have a threaded shaft welded to 'U' components, the nut screwed on and the nut welded. So the device is held together by 2 welds and a threaded nut. This is not dissimilar to some stainless swivels (some of which have a shaft with a cap welded on).

Vyv summarises above.

I'm interested in that the owner of the yacht appears to have defined precisely where the swivel came from - almost as if he bought it. There is no indication the swivel comes from a reputable manufacturer (and I could see no embossing on the shackles - but I might not have looked sufficiently carefully).

As I said in the opening post - not enough information.

As Kelpie said - there does not appear to be any wear - the shackles that are neatly moused seem almost unused. The swivel did not fail from prolonged usage and wear - my money is on a poor weld.

Jonathan

 

[Graham376]

Failure is usually due to the weld holding the nut corroding away and then the nut comes undone. Recommended life (from my supplier) is 3 years but check the weld annually. I had one fail after 4 years and when I replace the current one will drill and pin the nut.

 

[Praxinoscope]

That design of swivel is very poor and should be avoided. Relying on the threads of a nut and bolt, even with a tack weld between the two, is asking for trouble. The stainless ones sold for anchoring are very poor and I believe are actually intended for fishing gear.

Surprised that you dismiss the S/S versions, I have used the same S/S swivel on my mooring now for 10 seasons, I check it regularly and it’s washed and stored in the dry each winter, it is still in perfect condition.
Just going down to the boat now so will add photo of it in situ later.

 

[Praxinoscope]

Surprised that you dismiss the S/S versions, I have used the same S/S swivel on my mooring now for 10 seasons, I check it regularly and it’s washed and stored in the dry each winter, it is still in perfect condition.
Just going down to the boat now so will add photo of it in situ later.

A couple of photo's of S/S swivel after 10 seasons. It's due for replacement in 2019. The nut seems to be riveted not welded.

 

[noelex]

I witnessed underwater the gradual failure of a similar swivel on an anchored boat. The owner was lucky not loose the yacht.

 

[vyv_cox]

A couple of photo's of S/S swivel after 10 seasons. It's due for replacement in 2019. The nut seems to be riveted not welded.

I am not sure what the difference might be between drying and fully immersed stainless steel gear on a mooring but it is usually best avoided. My destructive tests, shown on the website, found this type to be far weaker than other anchor swivels.

 

[Praxinoscope]

I witnessed underwater the gradual failure of a similar swivel on an anchored boat. The owner was lucky not loose the yacht.

I'm surprised the swivel gave way before the shackle with no locking on it decided to come undone. there always will be the odd failure, and the shackle swivel etc. do not look like S/S to me but virtually new galvanised, and look like a different construction.

 

[vyv_cox]

Failure is usually due to the weld holding the nut corroding away and then the nut comes undone. Recommended life (from my supplier) is 3 years but check the weld annually. I had one fail after 4 years and when I replace the current one will drill and pin the nut.

Preferential weld corrosion does not occur if the rod has been selected correctly. For mild steel piping carrying seawater in offshore applications the filler rods will have about 0.25% chromium to make the weld more noble than the main body.

 

[noelex]

I'm surprised the swivel gave way before the shackle with no locking on it decided to come undone. there always will be the odd failure, and the shackle swivel etc. do not look like S/S to me but virtually new galvanised, and look like a different construction.

The swivel was a stainless steel, not a galvanised model, but I agree a single failure such as this does not mean much statistically. Nevertheless, it was scary watch the swivel gradually open up over an hour or so. Especially as it started with only a tiny crack that could be easily be missed.

The skipper could not be convinced that there was a problem.

This photo from about 1/2 hour before shows the swivel construction a little better:

 

[Praxinoscope]

The discolouration around the break and around the nut suggests that this was a poor quality S/S, I wonder if the boat owner had bought it cheap on ebay? And to fail to seize a shackle indicates a rather careless attitude to his/her mooring.

 

[noelex]

And to fail to seize a shackle indicates a rather careless attitude to his/her mooring.

Yes, I agree.

Too clarify this swivel was on an anchored boat not a boat on a mooring.

 

[Praxinoscope]

Ah yes looking at your photo I can see it is at anchor.

 

[Neeves]

I'd suggest, as Praxinoscope suggests, the problems might be deeper.

The original thread (on CF) is desperately sad.

But the mousing of the shackles is not what I might call 'professional'. Our shackles on our mooring are preened (is that the word). The swivel itself (in the picture) seems, undernourished? - sort of a but thin for something that you are going to use to secure your pride and joy (and possibly your 3rd biggest investment - after husband/wife, house).

So - I am sympathetic, saddened (the yacht looks as if it was gorgeous) but....?

Why would anyone trust something that cost $29? Why would anyone buy a component to which they trust their pride and joy to a component the manufacture of which has not the pride to attach their name??

The environment is harsh - why was he surprised that $29 was not enough.


I make no apologies - we reap what we sow.

Jonathan

Edit

When our mooring is renewed I sit on the mooring barge of our 'service agent'. I accept that many do not have the time. However our provider makes the comment - I am unique, no-one else bothers. He does not mind I am 'nosey' - I don't distrust - I have this fascination in how our investment is secured.

close edit

 

[Kelpie]

Just in case not all those participating in this thread have actually read all the way through the relevant blog post, some facts about the mooring:
It had been laid about a year before the incident.
It was not laid by the person who lost their boat.
The $29 swivel was shown as an example of a similar type only.

So it was a mooring loaned in good faith, by a friend who ended up giving a lot of their time helping the poor family whose boat was lost. The boat was to be left on the mooring while the family flew home, and the accident happened just before they were due to get their flight.

 

[Neeves]

Thanks Kelpie, I confess I had not read the blog ( for some reason I had assumed the salient points were in the thread).

A year is not long, moorings should last, much, longer. Normal, frequency for servicing is, 1 year?, allowing a 3:1 or 4:1 safety factor

The fact it happened to an innocent 'bystander' does not alter anything - it would have happened anyway. The fact it was an innocent bystander meant the issue was aired (otherwise it might have been quietly shelved).

If the swivel posted was similar - it does not make it better - it still looks similarly cheap and nasty.

It does not matter whose fault it was, that is an issue for the party's concerned.

There are a variety of lessons - and it is the lessons that are important - to us

Jonathan

 

[vyv_cox]

The discolouration around the break and around the nut suggests that this was a poor quality S/S, I wonder if the boat owner had bought it cheap on ebay? And to fail to seize a shackle indicates a rather careless attitude to his/her mooring.

I would say this is a very common type of failure in marine srrvice, stress corrosion cracking. I have recently added some case histories showing it, under rigging on the website. It can happen to many types of stainless regardless of quality.

None of the shackles and swivels in my anchor rodes are seized: indeed it is not possible to do so. I use Loctite 242 and have done for many years. None has ever come undone and take quite a torque to undo at the end of the season.