Catenary - would you buy krypton piano wire?

[thinwater]

^^ Corrosion. Never debated that and I said that I would not. It is better to see data. What you said is generally obvious. I would also bet lunch only a few % of the people use their chains that hard or keep them that long, and this is only a problem if you do BOTH (corrosion and enough use for it to accelerate wear). You do, but few people cruise that much. I see a lot of tiny anchors in marinas that assure me they don't go far!

Toughness and elastic elongation. 200 feet of grade 80 chain will stretch 3 feet at the WLL, while grade 30 will stretch only 1-foot. That is the difference for the lifting industry. You have to admit that is interesting, since chain only fails when they are snatch loaded (can't prove that, but I think it is very nearly self evident). I'm surprised that no one has discussed this variable. You can rhetorically dismiss the issue by switching the discussion to hardness--which is a separate issue--but there it remains; high strength chain is more elastic. I think we are dismissing that rather casually, without discussion.

The best answer? It depends on the boat. My last boat I would not have used grade 80 because grade 43 was enough and grade 80 was not available smaller. There was no need to ponder. My current ride makes more sense with rope--chain would be massively stupid. I suspect the universe of boats were grade 80 is the smart choice is limited. But I'm not in the fight.

 

[Neeves]

That is a nice explanation Thinwater, but I am afraid I don't see much relevance to a marine application where the steel is immersed in salt water.

The concern is not that G7 chain corrodes faster because it is softer. No one has suggested that. The concern is that G7 corrodes faster because when switching to this chain the diameter and weight are reduced, but the forces produced by the boat are the same.

The thinner chain is significantly lighter (which is the aim) and therefore moves around more in an anchoring application. This can be seen quite easily underwater. This extra movement creates more abrasion on the galvanising both from the chain links rubbing on the seabed and also from the chain links rubbing against each other. The extra movement and abrasion wears the galvanising and it fails earlier.

The chain wears most rapidly at the apex where the links join. As well as the greater movement seen when using thinner, lighter, G7 chain versus a thicker G4 chain, the bearing surfaces where the chain rubs together are smaller with thinner chain. As an example, think of two round 10mm bars verses two round 8mm bars mated together. The contact surface area is considerably less for the 8mm bars. This surface area acts as the bearing and wear surface, but as the boat size has not been reduced the force remains the same, and compounding this, as the weight of chain is less the links are moving more.

.

This lacks statistical significance.

G70 has been available for decades from ACCO, that is now a part of Peerless. Dashew has used G70 on his, expensive, expedition boats. G70 does not enjoy a large market share - but it has been used for decades. Interestingly many of its users, such as Dashew, describe their experiences and are looked at a 'role models'. None of them have ever suggested that G70, sized smaller, has a very short life, though most in not all have used ACCO G70 chain, not Maggi.

There is no evidence that ACCO G70 has a reputation for low life.

You have used G70 from a different manufacturer, who do not have a stellar reputation for the quality of their galvanising.

You appear to have had issues with performance but have, for what ever reason made muted (if any) comment at all on this issue. You have had plenty of opportunity to warn potential users.

You have made no indication of the quality of the original quality of the galvanising of your chain. Basically you have no idea if the quality met specification. You have no idea of the thickness of the coating nor its integrity.

But despite this - you are prepared to damn all G70 - as suffering the same issues you describe.

With respect to this thread - the galvanising coating will be at least 30% thicker than standard HDG minimum specifications. Secondly the galvanising coating with be harder than standard HDG (and as has been indicted hardness reflects abrasion resistance). The actual thickness of the coating is easy to measure, accurately - it would be part of specification.

This is repetitive - the US Navy/Marines use this same coating because it has a higher abrasion resistance than HDG. The US Navy/Marines have set a specification of 80 microns, normal spec for HDG is 70 microns, and the specification for the chain the subject of this thread is 100 microns. Unfortunately though there are specifications for the thickness of galvanising on short link anchor chain these are never quoted in available batch QC sheets. I have advocated that coating thicknesses are defined for each batch - but no-one has shown any enthusiasm. It would be cheap and easy to conduct. As you point out the life of the galvanising determines the life of chain. It does not fail because it breaks or distorts - it fails because it corrodes - yet there is no data available to the user - he buys blind.

And you have no idea if your coating was 40 microns or 200 microns and you have no idea of the integrity of your coating.

Coating integrity - Viv Cox made a study of galvanised chain and the results were published in YM, I think the detail is on his website. He described a simple and cheap test to assess the integrity of a galvanised coating.

The rest of the post is pure speculation - you (nor anyone else) has any idea of the comparative wear rates of abrasion/corrosion resistance of small but hard chain vs abrasion/corrosion resistance of larger, soft chain. You are guessing

Again there is no evidence that ACCO G70 at one size smaller has serious issues of lower life, whether galvanising or wear and corrosion of underlying steel, than G30, nor G43.

Your theories seem interesting but there is no evidence they have any validity. In fact the available evidence suggest your experiences are not worth of mention for ACCO galvanised G70.

The area merits serious investigation (as it was raised as a critical issue by someone who otherwise might be seriously interested), which will be conducted - as has been said.


The other factor you ignore is the influence of better acceptance of snubbers, or bridles. Today we use snubbers to decrease dynamic loads, rather than simply to take the load off the windlass or stop the chain rattling on the bow roller. Secondly users are using longer, and longer, snubbers than were used historically and we are accepting that increased elasticity - by employing specific rope construction - is beneficial. There is no intent to use HT chains in isolation but to use in conjunction with mechanisms to reduce dynamic loads - which will reduce any abrasion on the crown of links.

Too long the rode has been considered a combination of unmatched components - we would not do that in rock climbing, they have not done that in the lifting industry for decades and hopefully out hulls are designed as an engineering whole - not a mismatch of pieces. There seems no reason to continue past practice - but to design rodes to suit specific vessels and needs. We have that opportunity - and guess work should have no part.

Jonathan

 

[Neeves]

Where does the query about the galvanising come from. If the same hot dip process is used then the protection will be similar though the consequences of wearing out the galv on a thin chain will obviouslt be worse - HT steel rusts at the same rate as ordinary steel

So to sum up:
1/ 6mm will wear and corrode faster
2/ its catenary effect will be less

I reckon you are solving a problem which doesnt exist.

its a different galvanising process. The process allows a specific thickness of coating to be applied. I can vouch for this - I have specified specific coating thickness - these have been achieved. Measurement is easy, cheap and accurate. Find me an HDG operator who can offer that, or any, accuracy. The process produces a coating that is harder than conventional HDG. This has been validated by independent testing by the University of Newcastle (Australia). The longevity of the process is the reason it is specified by the US Navy/Marines.

 

[noelex]

Jonathan, you started this thread and asked several questions about the use of G70 chain. For example from post #1:

If you were buying a new yacht and you are sceptical of the historically reported necessity for catenary would you consider lightweight anchor chain? Or if not why not - what might convince you?

In many respects the same is true of G70, though not as extreme. You can replace 10mm G30 with 8mm G70 - why is the uptake so slow. Many agree catenary is overrated - but this does not result in sales of G70 - Maggi must despair

You now seem upset that someone has attempted to answer these questions. I have more experience anchoring with G70 chain than many, but it is obviously only my opinion that I am voicing.

I think the thread has been useful, but if don't want the opinions of others I would suggest not starting this type of thread.

Let's try and respect alternative points of view.

 

[Neeves]

I value all opinion.

I am pointing out that I think your experience (which is not an opinion but something that happened - your galvanising lasted 3 years, that's not an opinion it is a fact) is unusual in that your experience has not been documented by anyone else. I have questioned, given your current passion - why it was not described earlier.

I have also said that I will test the variation in gal and underlying steel wear (and corrosion) and validate, or otherwise, your experience as being typical or not. I have samples of Maggi G70, Peerless G70, Campbell G70, PWB (same parent as Peerless), Peerless and Campbell G30 all in 5/16th" or 8mm, I will buy some PWB 10mm G30 and I have samples of HT 6mm and 8mm (the latter from 2 suppliers). I have already tested Maggi G70 vs Campbell and Peerless G70 and HT G80, all in 8mm sizes for abrasion, but not subsequent corrosion. These latter tests support the idea that a 100 micron coating would be advantageous and that the galvanising proposed is harder, more abrasion resisting than HDG (confirming evidence from America). I might add - my testing of Maggi chain did not fill me with confidence, very strong but the galvanising was questionable - especially as it 'failed' the test described by Viv Cox.

You have presented your assessment of the abrasion and corrosion as fact, I don't see it as fact but, as you now say opinion. I will test that opinion and anything else that is raised.

I might remind you that you presented as fact that G70 had a harder outer skin and softer inner layer and that once the skin was abraded the chain would not have the same strength - this has not met much support. I'd also mention again that your experience is of one suppliers whose galvanising quality has not been considered 'as the best' - which you did not mention to qualify your comments (and that I think might be contributory to your experience). This latter is my opinion - it will be tested with samples.

I think fact or opinion that enjoys an alternative 'opinion' and validation of facts all merit airing as one opinion, in isolation, does not lead to an exploration of ideas. Your opinions are as valid as mine and as a user are gratefully received - just because I have a different opinion does not mean your are ignored or wrong - so there is no need to be sensitive.

Robust discussion can lead us forward. I cannot agree with the stifling of opinions and fortunately YBW offers a fair basis.

Jonathan

 

[GHA]

You now seem upset that someone has attempted to answer these questions. I have more experience anchoring with G70 chain than many, but it is obviously only my opinion that I am voicing.

I think the thread has been useful, but if don't want the opinions of others I would suggest not starting this type of thread.

Let's try and respect alternative points of view.

:encouragement:

 

[RupertW]

This lacks statistical significance.

G70 has been available for decades from ACCO, that is now a part of Peerless. Dashew has used G70 on his, expensive, expedition boats. G70 does not enjoy a large market share - but it has been used for decades. Interestingly many of its users, such as Dashew, describe their experiences and are looked at a 'role models'. None of them have ever suggested that G70, sized smaller, has a very short life, though most in not all have used ACCO G70 chain, not Maggi.

There is no evidence that ACCO G70 has a reputation for low life.

You have used G70 from a different manufacturer, who do not have a stellar reputation for the quality of their galvanising.

You appear to have had issues with performance but have, for what ever reason made muted (if any) comment at all on this issue. You have had plenty of opportunity to warn potential users.

You have made no indication of the quality of the original quality of the galvanising of your chain. Basically you have no idea if the quality met specification. You have no idea of the thickness of the coating nor its integrity.

But despite this - you are prepared to damn all G70 - as suffering the same issues you describe.

With respect to this thread - the galvanising coating will be at least 30% thicker than standard HDG minimum specifications. Secondly the galvanising coating with be harder than standard HDG (and as has been indicted hardness reflects abrasion resistance). The actual thickness of the coating is easy to measure, accurately - it would be part of specification.

This is repetitive - the US Navy/Marines use this same coating because it has a higher abrasion resistance than HDG. The US Navy/Marines have set a specification of 80 microns, normal spec for HDG is 70 microns, and the specification for the chain the subject of this thread is 100 microns. Unfortunately though there are specifications for the thickness of galvanising on short link anchor chain these are never quoted in available batch QC sheets. I have advocated that coating thicknesses are defined for each batch - but no-one has shown any enthusiasm. It would be cheap and easy to conduct. As you point out the life of the galvanising determines the life of chain. It does not fail because it breaks or distorts - it fails because it corrodes - yet there is no data available to the user - he buys blind.

And you have no idea if your coating was 40 microns or 200 microns and you have no idea of the integrity of your coating.

Coating integrity - Viv Cox made a study of galvanised chain and the results were published in YM, I think the detail is on his website. He described a simple and cheap test to assess the integrity of a galvanised coating.

The rest of the post is pure speculation - you (nor anyone else) has any idea of the comparative wear rates of abrasion/corrosion resistance of small but hard chain vs abrasion/corrosion resistance of larger, soft chain. You are guessing

Again there is no evidence that ACCO G70 at one size smaller has serious issues of lower life, whether galvanising or wear and corrosion of underlying steel, than G30, nor G43.

Your theories seem interesting but there is no evidence they have any validity. In fact the available evidence suggest your experiences are not worth of mention for ACCO galvanised G70.

The area merits serious investigation (as it was raised as a critical issue by someone who otherwise might be seriously interested), which will be conducted - as has been said.


The other factor you ignore is the influence of better acceptance of snubbers, or bridles. Today we use snubbers to decrease dynamic loads, rather than simply to take the load off the windlass or stop the chain rattling on the bow roller. Secondly users are using longer, and longer, snubbers than were used historically and we are accepting that increased elasticity - by employing specific rope construction - is beneficial. There is no intent to use HT chains in isolation but to use in conjunction with mechanisms to reduce dynamic loads - which will reduce any abrasion on the crown of links.

Too long the rode has been considered a combination of unmatched components - we would not do that in rock climbing, they have not done that in the lifting industry for decades and hopefully out hulls are designed as an engineering whole - not a mismatch of pieces. There seems no reason to continue past practice - but to design rodes to suit specific vessels and needs. We have that opportunity - and guess work should have no part.

Jonathan

Your paragraph on snubber has got me thinking which is always a bit dangerous. Although I use a short snubber with rubber snubber on it in light condition I let out a lot more rope (if there is anchoring room) when its gets heavier. So given that I've been convinced by the maths and reality behind the pointlessness of catenery I should reconsider having a long chain at all and go to a short 20m or so chain to avoid chafe and use my long anchor rope for the rest.

Hmm...but I like the backup of chain taking the strain if the rope snaps.

 

[noelex]

I have also said that I will test the variation in gal and underlying steel wear (and corrosion) and validate, or otherwise, your experience as being typical or not.
Jonathan

I always read the results of anchor and chain tests with interest. But if I understand your experimental protocol correctly, it will not be looking at the primary corrosion difference between G30 and G70.

To do this you need to match thinner G70 chain with thicker G30 chain and subject both examples to the simulated movement of a boat using these chains at anchor. Both yawing from side to side and moving around the swinging circle.

If the simulation is accurate, I believe the lighter, thinner G70 will be moving around more than the thicker, heavier G30 chain. This extra movement will cause the galvanising to wear more rapidly on the G70 chain, especially in the critical area where the chains join.

Looking at the galvanising thickness and quality together with the underlying steel wear etc of various chains will be interesting information, but wont show why G70 corrodes more rapidly. For this you will need to simulate the greater movement of the thinner, lighter G70 chain at anchor.

 

[Neeves]

Noelex,

Thank you for that.

I think you are assuming that a G70 moves around more than a larger sized G30/40. In isolation this may be true but with a carefully matched long snubber I have an open mind as my experience suggests a long snubber markedly reduces movement of the yacht. As I emphasise - the objective is to have a matched rode - not some haphazard collecting of components. I have no pre-conceived idea and do not accept, nor discount that 'good' G70 will corrode more rapidly, in a smaller size - as I keep emphasising - your experience is not reflected by anyone else so statistically it is not sound - but cannot be ignored.

I believe some other tests are planned to look at snubber, or bridle, design.

I need to test HDG G30 and G40 in 10mm and 12mm each of them against my existing stocks of HDG G70 (all in 8mm), and my stock of alternate galvanising G80, in 6mm and 8mm and G100 in 6mm and 8mm.

The intent is to abrade, dry, then soak in seawater for a period, then abrade again then soak again etc. The focus, taking note of your opinions, is to look at wear on the crown.

Don't expect results quickly - the last time I tested it took 70 days for each test .

The results will be published in Practical Sailor in the fullness of time.

Jonathan

 

[Neeves]

Rupert,

Thousands of people have used mixed rodes for decades. One reason was that there was not the availability of cheap electric windlass. Now we have reliable windlass - all chain is a very easy option.

A reason now to use all chain is that the whole rode is abrasion resistant (ignore catenary). If you anchor in areas where abrasion is not an issue then a textile rode, or part of it is feasible. At the other extreme - In coral it would be unacceptable. If you do have abrasion on your textile portion of the rode - you will see it and its not difficult to replace, wherever you are in the world.

We use a mixed rode, when we deploy a second rode and use it as a primary in mud when we deploy a Fortress.

Its not unusual to have a mixed rode.

Jonathan

 

[thinwater]

Your paragraph on snubber has got me thinking which is always a bit dangerous. Although I use a short snubber with rubber snubber on it in light condition I let out a lot more rope (if there is anchoring room) when its gets heavier. So given that I've been convinced by the maths and reality behind the pointlessness of catenery I should reconsider having a long chain at all and go to a short 20m or so chain to avoid chafe and use my long anchor rope for the rest.

Hmm...but I like the backup of chain taking the strain if the rope snaps.

I think quite a few of us feel that way. It's all about chafe. I don't worry above the water, because on a multi-hull you always have a bridle (the rope on the roller is not tensioned). But below is always a question mark. Depends a lot on the area. I have also been playing with fiber chafe leaders.

 

[Neeves]

Noelex,

On beefy, maybe beamy is less offensive, boats, like catamarans, we all use bridles and I identify, possibly incorrectly or for other reasons, that a longer bridle (longer than I would have thought necessary for snubbing) seems to reduce yawing, noticeably.

With this in mind I might have thought your new yacht might benefit from a bridle (not suggesting that it is beefy) but in looking at your yacht you do not appear to have bow fairleads - but I might be mistaken.

How are you going to rig a snubber, or bridle and, very much thread drift, if there are no bow fairleads how do you rig springs.


Secondly - you have described in detail your experiences with G70 and made very useful contributions on what is needed for testing - I'd welcome your comments on how to do the testing.

The first part of the post is addressed to Noelex - but I'd welcome any ideas in how someone might test for abrasion/corrosion and also making that comparison on different sizes of chain. Its relatively easy on the same size of chain - different chain makes it more complex - but I'm sure there is an acceptable (and realistic) solution.

Jonathan

 

[noelex]

Noelex,

On beefy, maybe beamy is less offensive, boats, like catamarans, we all use bridles and I identify, possibly incorrectly or for other reasons, that a longer bridle (longer than I would have thought necessary for snubbing) seems to reduce yawing, noticeably.

With this in mind I might have thought your new yacht might benefit from a bridle (not suggesting that it is beefy) but in looking at your yacht you do not appear to have bow fairleads - but I might be mistaken.

How are you going to rig a snubber, or bridle and, very much thread drift, if there are no bow fairleads how do you rig springs.

With their large beam, bridles work well on catamarans.

On some monohulls bridles can help, so are worth a try, but generally the limited separation of the two legs means the effect is much less. Because bridles move the attachment point backwards compared to leading the snubber over the bow roller, they sometimes make things worse. Rather than speculating and generalising, some trial and error is best way to resolve if a bridle is worthwhile on a monohull.

On our last yacht a bridal made no difference, so was not used. It will need some experimentation with the new yacht to see what works best. The anchoring system is not properly finished yet. There are a number of options for the snubber, but once again this has not been decided.

There are some fairleads on the stern (to avoid rope chafing on the solar arch), but the bulwark is very strong and is topped with a round bar that is designed to act as a fairlead for most of the cleats . This means the rope can be lead at any angle so it is ideal for springs. There are 8 large double cleats, so springs would normally be rigged from a dedicated cleat.

 

[noelex]

Secondly - you have described in detail your experiences with G70 and made very useful contributions on what is needed for testing - I'd welcome your comments on how to do the testing.

The first part of the post is addressed to Noelex - but I'd welcome any ideas in how someone might test for abrasion/corrosion and also making that comparison on different sizes of chain. Its relatively easy on the same size of chain - different chain makes it more complex - but I'm sure there is an acceptable (and realistic) solution.

I think the most accurate way would be to do a practical test and anchor for the same duration with thinner G70 chain and thicker G40 chain and note the loss of galvanising. If you talk to cruising sailors there are few that have effectively done this test when they have switched chain types. Some have documented these results.

Have a look at this report, as an example:

https://svneko.com/2016/12/20/extremely-disappointed-in-maggi-chain/

They used Maggi Aqua 4 (grade 40 chain) for 6 years with minimal rust and the chain had been used by a previous owner so was actualły 10 years old. They then changed to Maggi Aqua 7 (grade 70) and went one size smaller. After one year it displayed "alarming amounts of rust and corrosion". It was replaced after 18 months. Both chains were made by the same company, the only differences were a change from G40 to G70 and a reduction in chain size of one step, as is normally done when switching to G70.

A more controlled test could be done, but I think it would require a mechanical system to simulate the movement of the boat. If this was done in the water, the lighter, thinner chain would move more and the loss in galvanising could be measured.

 

[Neeves]

I think the most accurate way would be to do a practical test and anchor for the same duration with thinner G70 chain and thicker G40 chain and note the loss of galvanising. If you talk to cruising sailors there are few that have effectively done this test when they have switched chain types. Some have documented these results.

Have a look at this report, as an example:

https://svneko.com/2016/12/20/extremely-disappointed-in-maggi-chain/

They used Maggi Aqua 4 (grade 40 chain) for 6 years with minimal rust and the chain had been used by a previous owner so was actualły 10 years old. They then changed to Maggi Aqua 7 (grade 70) and went one size smaller. After one year it displayed "alarming amounts of rust and corrosion". It was replaced after 18 months. Both chains were made by the same company, the only differences were a change from G40 to G70 and a reduction in chain size of one step, as is normally done when switching to G70.

Interesting real life example.

I do find it difficult to accept that there is a suggestion that the only differences in the 2 rodes was size and steel grade and these 2 changes caused a reduction in life from 10 years (or even 6 years) to 1.5 years. The idea that the galvanising of the G70 might have been at fault does not appear to be considered.

As I continue to repeat - Maggi has a poor reputation for galvanising, aired on YBW, Peerless/ACCO are not subject to a poor reputation and has been making and selling gal G70 for decades. Dashew has been promoting G70 for decades - and continues to do so.

There is, to me, an increasing amount of evidence to suggest that control of the process, or quality control, might have a greater influence on life of the gal coating than anything else.

You mention 'some' have documented and 'as an example' - this suggests, other documentation other examples - and more links?

Jonathan

 

[KellysEye]

> Vyv Cox has some interesting pictures showing just how near-straight chains get in even moderate conditions.

In that case there is not enough chain out or it is not heavy enough for the weight of the boat or both.

 

[vyv_cox]

> Vyv Cox has some interesting pictures showing just how near-straight chains get in even moderate conditions.

In that case there is not enough chain out or it is not heavy enough for the weight of the boat or both.

Nonsense. I have witnessed my chain near-straight and all off the bottom with a scope of 10:1 in winds of about 30 knots. My boat is 35 ft, 7 tons and I use 8 mm chain, which all authorities agree is perfectly satisfactory.

As usual, you raise a point that has already been shown to be incorrect several times previously. Some learn from their mistakes: you clearly do not.

 

[Greenheart]

Regarding the equivocal virtues of beloved chain, there's too complex a cocktail of knowledge and opinion here, for my minimal experience to take any view, although I'll feel wiser assuming we finally reach any conclusion.

I only wonder whether, if the benefit of chain is largely the prevention of roaming round the rode's scope within an anchorage, plus the possibly notional reassurance of its solidity (which itself may in fact be adverse in extremis), may it not be more effective, less effort and equally safe to eradicate the many questions and costs of chain altogether, and simply set a well-spread pair of modern fast-setting anchors on all-rope rodes?

Coral notwithstanding. There's rather less coral in the Solent, than I remember from boyhood.

 

[AntarcticPilot]

One thing I really don't understand. The mechanics and mathematics of catenary curves is extremely well understood; I recall learning it at A-level! Wikipedia has an excellent description of the maths for those who, like me, have forgotten the details. The way a chain hangs, the distribution of tension along the chain and many other facts are well understood. Fair enough to debate the suitability of particular types of chain for particular usages, but debating the nature of the catenary makes no sense - it is so well known that it is taught to 17-18 year olds!

 

[Greenheart]

I thought the catenary debate arose because it is now fairly widely accepted that under the tensions experienced in relatively gentle tide/sea states, an inelastic chain cable is drawn taut between the boat and the hook...so the idea that its weight helps prevent snubbing, ceases to apply.

In fact with no elasticity at all, it's more likely to break out the hook, than a rope rode...so sections of stretchy line need adding to the chain simply to replicate the catenary effect, which left to gravity alone, isn't up to the job.