Stainless Steel anchor chain

[Neeves]

A reason for the thread

When I first looked at high tensile gal chain the doom sayers all said - bah! HT chain its brittle, it will snap like a crisp (or chip if you have crunchy french fries). I then tested it to find 2 things

Americans demand that HT chain has a 20% elongation, but G3, G4 and G7 have only a 15% elongation to break. I also found some American anchor chain does not meet American standards (and no-one says or find it to be brittle) and that gal HT chain have an actual elongation of over 20%. Basically the armchair critics had no idea. (Some HT chain is brittle - but not gal HT chain I tested). G70 had abetter elongation than some G3 and G4.

So I wondered if the idea of crevice corrosion and work hardening would rear their heads, how they applied to duplex stainless and then was it relevant.

The amount of stainless I see on bows, or in the rode, including the rode itself (and anchors) suggests its all a bit peripheral. Work hardening and crevice corrosion might be an issue - but not under the conditions most of us experience. I have not heard of an Ultra anchor failing, other than by bending (and that's an issue with many anchors). Not a single person on the shackle thread made mention their stainless shackle had failed. And if stainless chain was failing we would surely know - as everyone could then have said 'I told you so'!

So far here, 19 relies is not much, - there do not appear to be any issues, other than price.

Looking at Jimmy Greens prices, and the prices I quoted earlier then duplex chain is slightly more than twice the price for the same sized Maggi G70. If I've got that wrong correct me. I recall reading Noelex suggesting he was changing his G70 every 4 or 5 years. Duplex chain comes with matching connectors, all G60 - so no need to go and search for something that fits.

And then you get all the advantages of less towering, cleaner chain, more chain in the chain locker (the latter I had not thought of.

On chain wear - the first few metres, don't get much wear, they do not drag over the seabed as far as the next few metres and the last few metres are hanging and don't get worn. So its the middle part of the used rode that gets the wear. I assume Duplex is quite hard, so it should wear better than normal stainless.

Jonathan

 

[William_H]

I have had all stainless steel on my swing mooring for now about 10 years. The chain itself is of an unknown type coming from the inside of a lime kiln. I use ordinary 316 10mm shackles. There is no sign of wear on the links in a period when I would have replaced GI chain many times. There has been one case of apparent crevice corrosion in one link of the chain. Most peculiar being on the outside of one link. It looked like terredo worm had got in.
One thing I do know is that stainless steel shackles and GI chain don't go well together as GI chain wears/ corrodes quite fast. So yes I would go for all SS anchor chain but for cost. olewill

 

[Neeves]

A danger is, and possibly the cause of the horror stories - stainless steel appears to be designated a 'quality' but that quality can vary. I was asked to test some 316 chain from China. It was marked 316 and looked lovely. It was 8mm.

It failed at just over 3t, lower than most 8mm gal G30, which would normally fail at just under 4t, say 3,500-3,800kg. The stainless failed at 3,200kg. I think the strength, in isolation, would allow a supplier to sell against a min strength of 3t. But it started to elongate, permanently, at just over 500kg. I assume this was the link distorting rather than the links, or the wire itself, actually stretching, so bending and tightening of the crown rather than the links getting excessively long. It deformed at such a low load that I suspect it would quickly be of a dimension not to fit a gypsy so had it been used as an anchor chain one would soon notice.

But I also assume it would work harden quickly - and with repeated use, assuming it still fitted the gypsy, it would catastrophically fail (at below the UTS I found)???

I also tested 2 x 316 shackles , both 10mm, both bow shackles. One, from a very reputable distributor, failed at well under 4t the other from a corner shop in Hong Kong failed at over 6t. Distortion in both was severe at the point of failure. But both 316 but vastly different.

So we tend to lump all stainless with the same characteristics - but like 'ordinary' steel maybe we should learn to differentiate.

But cost - its an initial and daunting investment but if the duplex chain performs then my, personal, view is that it looks cost effective (though actually I am not sufficiently convinced yet). So my head says yes but heart says no (and my heart rules my wallet on this issue)!

One other advantage of duplex is that it comes in a 6mm format, so anyone who wanted to downsize from 8mm, to save weight, space, could throw stainless into the mix. Currently neither Peerless nor Maggi make a 6mm short link gal G70 so duplex opens a new possibility.

Jonathan

edit

For those lucky few in the nether regions the contact for both Petersen and Cromox is Bridco in south Qld. They hold stock of some items.

close edit

 

[OldBawley]

A reason for the thread
On chain wear - the first few metres, don't get much wear, they do not drag over the seabed as far as the next few metres and the last few metres are hanging and don't get worn.

Jonathan

I think you have it wrong or we are talking different things.
Worn to me means de diameter of the steel is worn down to 6mm by friction between the links. ( See pic blue arrow )


Others will refer to worn as the outside of the galva is gone by dragging over sand.
The worn I mean happens where the chain is hanging.
It is its own weight and the continues moving of all the links that causes it.

Our boat has very low windage, I guess the pull on the anchor is zero in 95 % of time. The length of chain lying on the bottom takes all the power that is needed to keep the boat anchored.
Maybe big cat´s with huge windage put a bit more pull ton he chain.
I use SS chain for the kedges, but kedges are not used continuously, so wear is not existent.

The strength of a chain is not the only value to consider.
Catenary, so weight is even more important.
So sizing down to 6mm, no good. Shock load will be devastating.

 

[Neeves]

OldB,

I will not debate much of your post as I believe YM will have a a concise and carefully argued article on catenary in March?, or that was the last I heard, maybe April. (I hope this does not betray a confidence and can be seen as a mechanism to ensure sales of that issue increase and sub numbers rise )

But if your chain is sufficiently heavy that your yacht does not veer then you will have no, or minimal, seabed abrasion. In most anchorages veering patterns are varied, different yachts veer differently, and the number of times we see it and have people mention it here - suggests chain abrading on the seabed is, or will be, common. Without abrasion people would not lose gal and lots of people complain of gal loss. I think you are most unusual, and maybe, lucky

Shock loads are non existent with 6mm chain (it could be piano wire were it strong enough) - that's what snubbers are for. If you have shock loads, your snubbers are not long enough or they are too large a diameter.

If I had to toss up between buying 10m of nylon or investing in (75m of) 10mm chain (both will remove shock loads) - I know which would be cheaper, reduce weight in the bow, need the smaller windlass and use less power in the windlass, need a smaller anchor locker and have less frequent towering. Stainless steel, or duplex, adds another dimension - it arguably will last long (as there is no gal to lose) it will not get as dirty as gal, so either be clean, or easier to clean, and it will tower even less and thus potentially make better use of space in the anchor locker. It also has the strength of American G70 and is not much weaker than Maggi G70. It has compatible connectors, which is more than can be said of G70. It looks absolutely gorgeous. If it lasts more than 2 times the life of G70 its paid for itself

Heavy chain is very early 20th century - there are products available now that were not even dreamt of 50 years ago - but the concept of catenary, in an anchor rode, has not taken them into account. If you go back 50 years I suspect the idea of catenary did not have the importance it is given today. In the absence of the electric windlass I suspect many used a mixed rode, a short length of chain but mostly cordage. Cordage was preferred to hand retrieval of all chain. So if 'no catenary' was good enough for other fathers and grandfathers - why is it so important to us?

Wait for the article (it has nothing to do with me and nor do I know what it says) I am sure it will be the basis of some impassioned posts.

Jonathan

edit

If you are sufficiently interested in snubbers then this link might help

http://www.practical-sailor.com/blo...394:197827a:&st=email&s=p_waypoints012716&v=A

close edit

 

[OldBawley]

Full time liveaboard, always on anchor. Catenary means comfort.
We do sail an old type of boat, very heavy, low windage, huge keel and more of the boat in the water than over it, so we already have a boat that does not move around at anchor.
Behind 50 meters of chain, using a 6 meter 16 mm nylon snubber with incorporated rubber dampener even force 8 is comfortable.
Above 8 nothing is comfortable. The noise alone.
A friend sailor living on his yacht has a mooring. Mooring well constructed, about 10 meter of very heavy chain, then nylon. Although a big yacht, living on that mooring is a lot less fun.
He told me that during storms standing in his boat is not advised. Snatching is so brutal that one is tossed in all corners.
Katabatic winds combined with Se storms vary the wind strength from zilch to force 10 in seconds.
OK, those are conditions most cruisers will never experience, we do. Quite often.
One more advantage of our snubber set up : the snubber is attached to the king post but comes on board trough a heavy block on the end of the bowsprit. This reduces pitching and yawing even more.

We often use kedges to fix the stern of the boat. I prefer using kedges thrown into under water rocks over landlines. Those anchors have 10 meter of SS chain, then sinking rode. It has happened quit often that people in dingy´s or even keel yachts pass just behind the boat, and so have the rode into their propeller of hit the rode with the keel.
For some reason those people are the opinion that is is my fault they are blind and or ignorant.
So I have bought two lengths of 30 meter 5 mm long link chain. Cheap stuff. Rowing the kedges out I control the flow of chain by foot. Since no more cut rode.

 

[NormanS]

A couple of points: Where does "Duplex" come from? My understanding was that simple bike chain was "simplex". Double roller e.g. Reynolds chain was Duplex, triple link roller chain was "triplex" etc. I don't think you're advocating that type of chain for anchoring.

I'm inclined to dispute your assertion that catenary wasn't considered important 50 years ago. In fact, I think in some ways the opposite is true. 50 years ago, chain was just chain, and exotic grades with much higher load capacities were not considered for anchor chains. Chains were specified to give plenty of strength, but also to provide catenary to prevent any shock loading. Now that much stronger chain is available, and a lot of boats are more weight conscious, there is understandably a tendency to use smaller, lighter chain. While perfectly adequate in strength, it loses out in catenary, hence the use of nylon snubbers etc. I make no judgement as to which is the better option, except to say that with light-displacement boats, where carrying extra weight is an obvious disadvantage, light chain with a snubber would seem to be indicated. Conversely, with a heavy displacement boat, where the extra weight of heavy chain has minimal effect, there is nothing wrong with using Heavy chain, and benefitting from its catenary.

 

[Kelpie]

Peter Smith, of Rocna fame, believes that in most setups catenary effectively disappears in a decent breeze (I think f6 and above, from memory). He therefore advises more weight in the anchor and less in the chain, for the same total weight.
He may not be totally unbiased but I found it quite a persuasive point.

(Of course he might start selling Rocna branded chain and then change his story...)

 

[Neeves]

Norman

Hopefully someone will come along and advise the derivation: 'duplex', as applied to high tensile stainless steel. I have simply been repeating a usage I have seen - and I may well be at fault

I suggested that many boat owners, 50 years ago (and the many would be small in today's terms) might use chain plus cordage simply because as they had to deploy and retrieve by hand and they sacrificed catenary for convenience (and we still see the same today - as some still use a mixed rode). They made the judgement convenience was a better option than catenary.

I do agree that 50 years ago chain was just chain - another point I tried to make was that much thinking has not changed (even if the choice has). Many think only in terms of that same, let's call it traditional quality of, chain, forgetting we have G40, G70 and high tensile stainless. We have seen the thinking in this thread - mention 'stainless' get work hardening. Mention stainless get crevice corrosion. In other threads mention G70 get brittle and hydrogen embrittlement. All thinking that possibly has historic foundation (I'm far too young to know ) but no foundation in the materials used today.

There is nothing wrong with using a 12mm chain on a heavy displacement vessel other than the fact that it merits consideration there are other options which might offer benefits (not previously thought of). Cheaper windlass, less power draw, smaller cables, smaller volume of chain, less towering in the locker. Blindly suggesting that catenary is the 'only' answer denies other options - which you do mention.

So, there is nothing wrong with using heavy chain, it has been proven eminently successful for years. But that does not mean it is the best option today, there might be other options - they merit airing and they might be found wanting.

Jonathan

 

[Neeves]

From the Cromox catalogue

cromox Nautic. Stainless
Windlass Anchor and Forerunner Chains
cromox anchor and forerunner chains offer superior durability and service life.
• Duplex steel 1.4462 has double the breaking force compared to Grade 30
• Materials with an increased- PRE value are suitable in warm seawater
• Increased weight savings and service life
• Smooth operation
• No “piling” inside anchor locker

Jonathan

edit

and from the International Molybdenum Association

Duplex stainless steel

Duplex stainless steels are called “duplex” because they have a two-phase microstructure consisting of grains of ferritic and austenitic stainless steel. The picture shows the yellow austenitic phase as “islands” surrounded by the blue ferritic phase. When duplex stainless steel is melted it solidifies from the liquid phase to a completely ferritic structure. As the material cools to room temperature, about half of the ferritic grains transform to austenitic grains (“islands”). The result is a microstructure of roughly 50% austenite and 50% ferrite.

close edit

 

[Neeves]

Peter Smith, of Rocna fame, believes that in most setups catenary effectively disappears in a decent breeze (I think f6 and above, from memory). He therefore advises more weight in the anchor and less in the chain, for the same total weight.
He may not be totally unbiased but I found it quite a persuasive point.

(Of course he might start selling Rocna branded chain and then change his story...)

Peter Smith's anchors, both Rocna and Vulcan are made and marketed on his behalf by CMP. CMP also make anchor chain in China under their Titan brand. They make metric G3, G4 and imperial BBB, G3 and G43. I do not think they make stainless, of any quality, and I have not seen G70 (but there is plenty coming out of China so this might have changed or to be changed). Peter Smith has 'manned' exhibition stands, close to home METS, where he has promoted both, his anchors and CMP's chains. The combination of the 2 lines is meant to be synergistic and some chandlers do sell both lines (I visited one in Piraeus), but many do not.

Much of what he says on smaller HT chain is a, succinct and quantified reiteration of Dashew's philosophy that he has honed over 3, maybe 4 decades. Dashew confusingly calls, what I call G70, System Seven. Duplex stainless steel chain, as far as I recall, is mentioned by neither Dashew nor Smith - but Cromox is quite new and post dates Smith's and Dashew's ideas.

Jonathan

 

[NormanS]

Peter Smith, of Rocna fame, believes that in most setups catenary effectively disappears in a decent breeze (I think f6 and above, from memory). He therefore advises more weight in the anchor and less in the chain, for the same total weight.
He may not be totally unbiased but I found it quite a persuasive point.

(Of course he might start selling Rocna branded chain and then change his story...)

I'm not sure, with his history, that I would believe anything that Peter Smith said.

 

[vyv_cox]

The Cromox reference is the first time I have come across duplex SS in chain, although I have known it in other applications for many years. As ever, there are so many different standards that their use contributes to the total confusion that exists in most people's minds (including mine). The BS 970 version is 318S13, in the same series as 304 and 316 but it may be better known as 2205, which is the UNS standard. In bolts I have seen it referred to as A5, in the series we know as A2 and A4. The one mentioned by Jonathan, 1.4462, is the German DIN standard that will eventually become an EN European standard by yet another designation! There are several compositions/types, lean, standard and super duplex, dependent upon chromium and nickel contents.

The Rocna shanks were supposedly made from 2205, as are several others, to improve resistance to bending.

 

[GHA]

I'm not sure, with his history, that I would believe anything that Peter Smith said.

Do you mean peter or his son?

 

[NormanS]

Re Duplex: Ah, so the Duplex refers only to the type of stainless steel. It's a bit confusing then to this simple soul to talk about Duplex chain, which has a different meaning altogether.

I'll never need to use any of these highfalutin' grades of chain, 'cos I still believe in the benefit of catenary, given by heavy chain, to which neither my boat, my windlass, or my chain locker object. But I'm not actively trying to convert others to the cause. Everyone has to choose what's best for themselves.

 

[rogerthebodger]

Re Duplex: Ah, so the Duplex refers only to the type of stainless steel. It's a bit confusing then to this simple soul to talk about Duplex chain, which has a different meaning altogether.

I'll never need to use any of these highfalutin' grades of chain, 'cos I still believe in the benefit of catenary, given by heavy chain, to which neither my boat, my windlass, or my chain locker object. But I'm not actively trying to convert others to the cause. Everyone has to choose what's best for themselves.

Duplex simply mean 2 (two) as in duplex chain, duplex radios, duplex steel grain structure,duplex back-stays, etc.

There are several grades of duplex stainless not just one.

A simplified guide to duplex stainless steel

http://www.bssa.org.uk/topics.php?article=668

 

[KellysEye]

>what were the circumstances in the case you refer to KE ?

The bottom therern is sand and he had been anhcoring there on and off for well over a year. I suspect the crevice corrrosion was caused by the chain being scratched by the sand and it wouldn't happen in mud. The corrosion resistance of stainless steel is dependent on the presence of an ultra-thin protective oxide film (passive film) on its surface so I suspect sand could remove that fairly easily.

 

[Neeves]

And Norman, I am at fault, your interpretation was correct. I can be lazy. 'Duplex chain' is so much quicker to type than 'duplex stainless steel chain'.

And as I have addressed this post to you. I have no axe to grind over duplex stainless steel chain - I started the thread to solicit any knowledge and opinion. In an earlier post I thought I made it clear that I can see the advantages but shudder at the price. Currently my wallet rules my thoughts. But the thread has drawn out those old and well entrenched, and incorrect, ideas.

It is very unlikely that I would change my mind - chain takes a very long time to evaluate and with any new development there may be characteristics that have not reared their head, yet, and for a product that needs something like 8 years to prove itself, over G70, it is a long time to wait. Others who value the lack of towering, cleanliness, bling, availability in 6mm sizings - might take a totally different view. If this thread has opened eyes (and minds) - its been a benefit.

Jonathan

 

[Neeves]

I posed this somewhere else.

If history had dictated that we all used high tensile stainless steel chain, of a correct strength, our anchor lockers and windlass were sized to suit and we all used decent snubbers etc - and then suddenly low tensile galvanised anchor chain were introduced, needing the bigger link, etc - would we all rush out and buy the cheaper option, changing our gypsies, losing the bling etc?? because we wanted the benefit of catenary.

Or would we worry about longevity, corrosion, extra weight in the bow (and be sceptical of the benefits of catenary (especially in winds over 25 knots) - and stick with what we have?

Jonathan