anchor connectors

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All we do it crank the pins up tight and dot the other side with a centre punch.

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I have had a s/s anchor connector without a swivel for a while now but not fitted. I was worried that the pins would come undone. Is dotting with a centre punch the best way to go?
 
Some time ago I read a letter submitted to Yachting Monthly by a reader. This gentleman mentioned how he was using a 1/2" double jaw rigging toggle as a connector to join his anchor to the chain cable.

OK, it does not have a swivel in it, but his philosophy for using this instead of a standard (non-swivelling) anchor connector was that the toggle will allow for a sideways pull on the anchor - whereas a standard connector will just have a large bending moment applied to it when a sideways load is applied. And apparently some of these standard connectors have failed from sideways pulls like this.

Has the forum got any views or opinions re using a rigging toggle as a connector?
 
hylas, who posts here, and is the designer of the Spade, has suggested using a rigging toggle in the past, in this forum. You could try searching, or maybe he will jump in.

ps - he's French and I think he spelt it 'toogle' /forums/images/graemlins/smile.gif
 
I am a metallurgist with 30 years experience in failure diagnosis /forums/images/graemlins/grin.gif You might be right or you might not. I just didn't bother to do a detailed examination, having better things to do than spend a couple of days in the lab.

In the letter to YM I suggested that it could be incorrect heat treatment but that could equally have rendered the fitting susceptible to stress corrosion. The facets showed some sign of penetration of corrosive media throughout so I favour the stress corrosion. Corrosion fatigue is also a possibility and does have some attraction as this mechanism effectively reduces the fatigue limit of the material to zero. Without a microscopic examination it is not possible to discern the crack morphology, therefore impossible to say. The position of the cracks also suggests that bending of the jaws with lateral loading may have been a factor. I doubt very much whether an axial force was responsible.

No idea of the source.
 
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The position of the cracks also suggests that bending of the jaws with lateral loading may have been a factor. I doubt very much whether an axial force was responsible.

[/ QUOTE ] Yes, that seems clear from the photo and there is no apparent plastic deformation so both facets seem to have failed at the same time - in a F3. It seems strange, I am trying to imagine what was actually happening down there around the time of failure; what would we have seen?

I think that it does matter - a great deal - what caused it. If we are arguing that this is a case of corrosion of a stainless component that belongs to a metallurgist with 30 years experience in failure diagnosis then what hope is there for the rest of us!?

If this was a case of simple brittle fracture, the process perhaps started by corrosion or minor damage, due to an over-brittle part (improper heat treatment) then we can avoid it happening again by taking this up with the manufacturer and buying from manufacturers with a better quality control procedure in place. Let's keep in mind that your vessel and lives could have been lost. This might have been a coroner's investigation.

Given your extensive experience in metallurgy, I am very surprised that you had better things to do than spend time in the lab getting to the bottom of it....especially when you then went on to carry out a test report for YM.
 
Vyv

There will be more people reading this thread who are just yachty people than there will be metallurgists. Whilst you have the knowledge to be able to asses a product better than most, the likes of me have to rely on what it says on the packet! So I would be interested to know why and how you assessed the swivel that failed, prior to purchase.
 
The more I think about it the more it looks like shock. As though the rode was too short in a chop, while the anchor was well embedded or trapped, or something similar, perhaps?
 
Bejasus - I don't know those ones but don't have any major issues with the way they have their keepers as a rule. We do similar on our big beast and the new 'nearly big beast'. Our are a lot smaller though. Without having a close look I'd say the look OK in theory. One could think that if they went the extra to put the keepers in they will probably have done other bits good as well.

We thought hard about keepers in the range but didn't think they were needed and went a sightly different way. Our cheeks are cast with a tad of outway splay. When you crank up the pins the last 2 turns out take a lot of grunt which pulls the cheeks in a bit and the tension holds the pins very well. As mentioned above you can centre punch the end a smidgen for that bit of extra security. So far many 1000's gone out and only 1 questioned (not failed) so we are happy.

The big thing to watch in swivels is the bit in the middle that holds it all together. Most fail in this area. Some do the bolt screw way and can very easily just un-screw. This has happened here with some a plonker 'got in real cheap'. 2 boats ended up on the putty. They looked a bit like vyv_cox one above actually.

It is a bugger really as we get comments about 'our' swivels doing bad things when in fact they were some others. The nature of the beast says that they all will look similar, a bit like chain. A bit of chain goes bad so everyone thinks our chain is bad. They don't see the bad one was from china and ours from Italy, an Apples V's Oranges thing.

Like anything take a good hard look at the item and the people who make it. If you have doubts don't go there and keep looking. Peace of mind is nice to have at 3am in 60knts.

have a great week-end all
 
<< Given your extensive experience in metallurgy, I am very surprised that you had better things to do than spend time in the lab getting to the bottom of it >>

It's not quite that easy, as I have been retired for three years. The failure occurred in Ibiza, from where I did not return for some months. I have no direct access to a lab, so I would have to spend my time and money on doing the investigation. I don't think the magazines would fund it as they consider this kind of article to be 'too specialised'. The YM article was nothing to do with ther failure. I was already in discussion with YM about destructive testing but when Simon Jinks left it went onto the back burner. My fracture letter brought the subject back to the front and I followed it up with Simon's successor.

In the end, I know nothing about the swivel's manufacturing process, manufacturer or seller. I think I bought it in Holland although I'm not even certain about that. So what would be the benefit of an investigation? What could I advise about buying these things other than what I have already done via the YM article? Buy from a reputable manufacturer, make sure the SWL or some significant data is stamped on it, buy the forged type with no bolted fixing at the chain or anchor connection. That's it.
 
Understood, but it does leave many of us wondering for ourselves. I have now examined my brand new Kong of what you call the 'better sort'. It is clearly a sand casting machined on the outside surfaces for cosmetic rather than engineering purposes. The male halves of the swivel castings have been turned but the facing female halves haven't (odd or is it just to ensure clearance rather than low friction?). Anyway, clearly brittleness is the issue with such a product. One would expect these castings to be batch tested and certified for hardness and tensile strength, if being used in life-safety applications.

I had expected to find them forged, at least at the high stress points, but clearly they have not been.

Do you, or does anyone else, have a view on that in the case of the Kong product? Is a simple sandcasting good enough?
 
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Do you, or does anyone else, have a view on that in the case of the Kong product? Is a simple sandcasting good enough?

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There are literally many many 1000's out there in use. From what we have seen the failure rate is a huge pile lower on Kong swivels (and ours) than shackles, even taking the dis-proportionate number of each in use.

That pretty much answer the question I think.

When it comes down to real use most good swivels and many not so good ones will still have a pile more grunt than the average anchor will hold anyway. In your average anchor system the anchor is still the item that causes most problems. Sadly the anchor appears to be the ONLY thing most people look hard at in their system.

Obviously the anchor and all other system issues are still a gazillion miles below the number of problems which would be called 'Pilot error' /forums/images/graemlins/smile.gif
 
Thanks for putting that straight - you do the best you can and when a debate comes along like this, it is a good time to air all the information and it forms an information base for people in the future.

I think is was earlier this thread, or a similar one running at the same time, that someone observed that his chain rusted more quickly after fitting a stainless swivel. I was discussing this with a mechanical engineer friend this evening and was wondering how significant this can be, in practice? I was wondering whether seizing small beads of magnesium (from fresh water anodes) with stainless wire to the rear of the stainless swivel would reduce the effect. This would become a local anode to protect the (zinc) galvanised chain and anchor.
 
Just been down at my boat and had a wonder around to see what was new, not much except a real nice J124. Not a cruiser as such but just a good looking yacht.

Just happened to see a 'new' swivel on the bow of a visiting yacht, we get a lot here. This was one of the Douglas marine ones mentioned above by Bejasus. Had a close look at it and, to be honest, 2 of the crew. How would you like to be cruising with 2 daughters aboard, one is 19 the other 21 and very far from hard on the eyes. The Dad (owner) said he does spend a bit of time chasing away 'local visitors' /forums/images/graemlins/smile.gif

Anyway the swivel. Looks OK but I would have done a few small things different. It has a bog standard bolt up the guts and I don't like all of the swivel action being on a bit of thread, I like the idea of full round bar more. The keepers were quite big and what that may do to the strength in that local area I'm not sure. Good oversized pins each end. Stainless with no signs of staining.

It has been 1/2 way around the world on a boat that prefers to anchor. It looks fine. It was the 10mm size. So I'd make a few small changes but otherwise it seemed quite OK.

Yeap your right there Lemain, a good thread. I don't think any action between the SS swivel and chain is any sort of worry. Having seen a lot I have never seen anything to suggest that that is an issue. The comment about the 1st few links being beaten up could have been caused by more than just the swivel. We see many rodes where the first bit has been hammered and most of those didn't have swivels. I'll chuck a SS swivel onto some galv chain and put it onto our test platform. It'll take a while but maybe interesting, just never know.
 
I wonder if the localised corrosion of links close to the swivel is caused because the zinc galvanising is depleted there more quickly, as it is trying to protect a more noble metal? The underlying steel links would then be attacked. I have certainly noticed the same effect, also where I have had stainless C-connectors in the chain.
 
I will try the magnesium anode trick and see what happens. If they are sacrificed then they have done some good. Meanwhile, the instructions on the Kong tell you to "grease and block" the assembly screw. The French and Spanish instructions use the verb "to cut". If they mean 'lock', how, if you have greased the thread?

How should I assemble the Kong? /forums/images/graemlins/confused.gif
 
I thought that there was a risk of the stainless seizing without grease (I forget the term) and I would like to be able to remove it when needed - the bolt has a good allen head so should come out if not seized in. Is Loctite likely to be permanent, in this environment? Come to that, does it work, immersed in seawater for long periods?
 
It's called galling. I have only ever experienced it in rigging bottle screws, not in a connector or shackle despite tightening as much as possible.

See a thread on Page 1 about prop locking - some posters know the correct grades of underwater loctite. I have only ever used a conventional grade and it seems to hold well on connectors after fairly lengthy periods underwater, although not permanently, of course
 
Loctite should be fine even the everyday stuff. A trick to get loctite undone is to apply a bit of heat or so I'm told, never tried it.

Maybe there is some stray volts running down your anchor rode. Maybe that has something to do with those few end links losing galv. I do know stray volts will run down mooring lines and so on which are only nylon/polyester with salt water on them. Steel would conduct better and when they hit the SS fitting it's easier to burn the galv off and head out that way. I'm guessing a bit here.

You 2 gents seem a bit better at the technical side of things, what do you think about that? Or maybe a combination of that and the SS next to the steel. I'm told that in an ideal situation 1 volt can eat 9kg of mild steel in a year. I have seen a very minimal current do some quite surprising damage over a year or so before it was picked up on.
 
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