Bigger is better, part 2

[JonJo]

Originally Posted by Andrew Troup

Jonjo

regarding chain designations:

I have no knowledge of how the current situation came about. I was under the impression that (for example) G7 is an abbreviation of G70 (which in turn is an abbreviation of G700, for 700Mpa nominal) because it's more legible when stamped on a small chain link.

I had assumed that "Grade L" and suchlike were PWB's proprietary designations, which I think were around before the likes of G30, but I could be entirely off beam.

Serafini use the same Grade L and Grade P designations.

I think the Australian standards designate Grade L and Grade P, there are other designations for higher grades.

Jonathan

[Kenomac]

It's amazing how these discussions about anchors just keep going and going. Just buy a one size larger Ultra anchor or something similar (new age) along with the appropriate chain for your windlass gypsy and be done with it. Keep your old anchor in the locker as backup.

[Coops]

Originally Posted by JonJo

Serafini use the same Grade L and Grade P designations.

I think the Australian standards designate Grade L and Grade P, there are other designations for higher grades.

Jonathan

L grade is the highest grade in Australia that I know of sold retail at chandlery level. PWB is stamped on the L grade because PWB make the chain. Whitworths also sell CMP L grade as well as PWB but my info is that this stuff comes from China. I would not swear to that being a fact though. There may well be higher grades for commercial usage but I have never come into contact with anything about it.

Coops.

[Dockhead]

Originally Posted by Andrew Troup

I personally think G7 chain is already a bridge too far. I consider it too fragile in respect of longer term risks such as stress corrosion cracking, notch sensitivity (ie lack of toughness), intolerance of unfair loads or damage, regalvanising embrittlement risks et al.

So I guess it goes without saying I think the notion of using even higher tensile material for anchor rodes to be scary and misguided.

No doubt someone will push the envelope further, but I think there are good reasons why old salts leave that process to others, especially in respect of what is effectively the last line of defence any boat can have.

There is almost always a tradeoff, for a given class of material, between increased performance and reduced reliability, and/or tolerance of misadventure and accidental abuse.

I tend to agree with this. However dearly I would like to take 100kg out of the very tip of my bow, I just don't like the idea of being at the edge of the envelope with the chain.

I think ground tackle should be oversized, and should be as idiot-proof as possible, with large margins of error everywhere possible. It should be capable of withstanding abuse and surviving misadventures. As Andrew perceptively pointed out a few posts up -- it's not peak performance that we're looking for, anyway. It's the absence, as far as possible, of weaknesses. These are very different things. I want my ground tackle to hold if I am forced to anchor with short scope or in marginal bottom; I want it to tolerate snatch loads in case I make a mistake in choosing an anchorage and end up with a broken snubber (not a hypothetical). An overstressed, overengineered G70 chain doesn't seem the right kind of design philosophy there; pace Steve Dashew.

Furthermore, although I don't quite worship at the catenary shrine like Andrew does, I do think that the role of catenary is somewhat underrated in these discussions. Catenary might be meaningless in ultimate conditions, but it is definitely not in meaningless in real, practical, everyday anchoring situations. And we should be caring as much or more about practical, everyday anchoring situations, as we do about ultimate conditions.

A heavy anchor chain in less than ultimate conditions protects the anchor from snatch loads, improving its holding, and provides a friendly, gentle motion at anchor. Especially in deep water.

[JonJo]

Originally Posted by Coops

L grade is the highest grade in Australia that I know of sold retail at chandlery level. PWB is stamped on the L grade because PWB make the chain. Whitworths also sell CMP L grade as well as PWB but my info is that this stuff comes from China. I would not swear to that being a fact though. There may well be higher grades for commercial usage but I have never come into contact with anything about it.

Coops.

Grade P, known in the rest of the world as G4 (or G40) is made by both PWB and Serafini - but effectively only when demand merits (and demand is low). Last time I spoke with Serafini they had none in stock. Serafini sell over the counter to personal callers, otherwise through Beaver. PWB sell through Whitworths. Both Serafini and PWB also distribute through the windlass companies and maybe other outlets. Serafini chain is stamped 'L' or 'P'.

CMP Grade L chain is made in their Ningbo factory. They also make BBB, G3 and G43 They also have a higher grade, cannot recall if its G43, G4 or Grade P, at boat shows (in Oz) but I have never seen it in a chandlers (and the chandlers know nothing about it). The chain is sold under the CMP Titan brand (but it might be Titon) and they have recently introduced gal bow and 'D' shackles under the same branding. The shackles are embossed with WLL and a 3/8th bow would be a WLL 1t shackle (which might not actually be 'good enough' for a G43/G4 matching sized chain - not sure, but they are certainly good enough for a G3/Grade L).

Strangely though the synergy between CMP with their chain and Rocna were meant to be part of the reasoning behind the combination Whitworths do not sell Rocna anchors and the people distributing Rocna's (or the ones I know in Oz) do not sell the chain. CMP chain also seems notable by its absence in Europe and America - Rocna is well known in both markets (Europe and America), but not the chain.

Jonathan

[Andrew Troup]

Originally Posted by JonJo

Andrew,

Thanks again,

....

Crudely quantifying

If G3 fails at 20% stretch, then 10% might be elastic and 10% (so 20% total) might be permenant deformation, G7 might be 15% and 5% (and G100 18% and 2%). I'm assuming same strength, but smaller and smaller chain.

If this uneducated 'summary' is correct then why is not this high elasticity good on the further assumption that WLLs are similar and are not exceeded. I have missed something, somewhere.

Basically Noelex 10mm G7 should be able to absorb more stress than the same sized G4, or G43 - its got more inherent elasticty.

Jonathan

The problem with that line of reasoning is that it works perfectly well all the way up to the ultra-high tensile point where the tempering is negligible or skipped altogether, and the material shatters explosively when tapped, having similar toughness to glass. This is not a sudden phenomenon, it's a steadily emergent one.
See my graph above*

Your reasoning takes no account of toughness.

However you're not alone among well informed lay people in misunderstanding these issues. In fact, it's very poorly understood, even by some people with considerable talent in engineering matters.

But it will take a bit of time to paint the elephant in this particular room in terms sufficiently black and white to convey the essence of the problem, without the elephant looking more like a zebra -- especially to do it with economy of words.

If you're interested, I'm happy to do that, but it might not happen today.

- - -
*which incidentally does not go all the way to "glass hard", because there is no engineering use for steel in that condition. Even if there was such a use, it would certainly look almost exactly unlike an anchor chain.

[Andrew Troup]

Originally Posted by Dockhead

...Catenary might be meaningless in ultimate conditions, but it is definitely not meaningless in real, practical, everyday anchoring situations. And we should be caring as much or more about practical, everyday anchoring situations, as we do about ultimate conditions.

A heavy anchor chain in less than ultimate conditions protects the anchor from snatch loads.....

Have you seen the video Peter Smith posted of the worst anchoring situation he got into, in his tour of the subantarctic and Antarctica?

He has the same size and length of chain as you, Dockhead (ie, 1/2" when he should have 16mm!) on a similar sized boat.

Nevertheless, in an exposed situation in South Georgia with gusts to 70 or 80 knots, in conditions where he didn't consider it safe to fit a snubber (because of insufficient sea-room to leeward), the catenary of his chain was sufficient to protect the bow roller, the chain and the bitts from damage, for a day or more.

Some of my early subantarctic sailing was done on a similar sized vessel, with 16mm chain. We never considered it necessary to fit a snubber, and despite some interesting situations, snubbing was never an issue.

[JonJo]

Andrew,

There are a few highly respected yachtsmen who advocate use of smaller G7 chain to the same (or similar) working load as the recommended G3 or G4 for that size of yacht. Peter Smith and Morgan's Cloud come to mind. Noelex has stuck his neck out and invested, certainly in the chain and maybe a new gypsy. But the philosophy is, down size the chain to save weight (but focussed at the correct WLL) and maybe carry a bit more chain (to access deeper anchorages). (I'm not ignoring the bigger anchor - just do not want to detract from the chain.)

The main negative mentioned over use of G7 is an inablity to re-galvanise and hydrogen embrittlement (which you do not really emphasise).

You have aired a whole new spectrum of disadvantages not mentioned by anyone else at all - and I think some, many of us, would benefit from any time you can invest to provide us an education. I do not think your taking time to post will inconvenience any of us (except as its pouring hard here I cannot get outside).

I hope I speak for many - we would love further input.

Jonathan

[noelex 77]

Originally Posted by Andrew Troup

If you're interested, I'm happy to do that.

That would be great.

Originally Posted by Andrew Troup

Nevertheless, in an exposed situation in South Georgia with gusts to 70 or 80 knots, in conditions where he didn't consider it safe to fit a snubber (because of insufficient sea-room to leeward), the catenary of his chain was sufficient to protect the bow roller, the chain and the bitts from damage, for a day or more.

I have not seen the video only stills. I always assumed he took the photo to specifically illustrate the chain angle and therefore took the photo with the snubber removed.
Did he anchor in those winds for a day without a snubber. Wow.

Kiwi Roa does appear to have a very tough anchoring system (bow roller chain stopper etc) but that is very hard on the anchor.

Insufficient sea-room does not seem a sensible reason (unless he was stern tied close to obstructions) the stretch in a snubber is only a few meters.

[noelex 77]

I think this must be the video:
The Rocna 55 is doing a great job.

60 knot winds: "Kiwi Roa" at anchor, enduring South Georgia Island - YouTube

[Andrew Troup]

Originally Posted by noelex 77

That would be great.



I have not seen the video only stills. I always assumed he took the photo to specifically illustrate the chain angle and therefore took the photo with the snubber removed.
Did he anchor in those winds for a day without a snubber. Wow.
The vessel does appear to have a very tough anchoring system, but that is very hard on the anchor.
Insufficient sea-room does not seem a sensible reason (unless he was stern tied close to obstructions) the stretch in a snubber is only a few meters.

It wasn't the stretch: his rationale was that at any moment they might need to quit the situation and there would not be time to deal with the snubber in his judgement, presumably because with the anchor dragging it would be a major battle just to get the nose splitting the wind in order to motor clear.

PS ON EDIT: Yep, that's the vid I was thinking of.
It turns out I misremembered about it being a day-long blow; it was several days.

[Andrew Troup]

Originally Posted by JonJo

Andrew,

There are a few highly respected yachtsmen who advocate use of smaller G7 chain to the same (or similar) working load as the recommended G3 or G4 for that size of yacht. Peter Smith and Morgan's Cloud come to mind....

Hmm - John Harries of M's Cloud was one of the people I was thinking of when I mentioned hugely knowledgeable lay people who had the wrong end of the stick as regards the relationship between tensile strength and toughness.

And he plumped for G7 chain partly on the advice of Peter Smith*, who was not using it* (and partly on the advice of a guy from Peerless whose advice was either wrong or misunderstood, on the specific issue of toughness - and in spite of his own reservations when he discovered that, even with larger links at each end of his shot of chain, he was unable to source shackles which were as strong as the chain ... sigh...)

*And another of the people I was thinking of, who had the wrong end of the stick on the issue of toughness, was his son Craig, as he demonstrated in this post, on this very forum:

http://www.cruisersforum.com/forums/...tml#post497210

Where he says
"You should size G7 with a slightly higher WLL than G4, to allow for its reduced handling of shock loading. However WLL is WLL and all chain breaks when it breaks, the particular failure mode (stretch or snap) is a bit of a non-issue."

I'll address why this last sentence is remarkably misleading and misguided when I respond to JonJo's request to lay out the toughness conundrum.

Neither Peter (in spite of what John Harries evidently thinks) nor his son is an engineer. They have an impressive grasp of anchoring-related issues (and in Peter's case, sailing and boatbuilding issues) but some of the more counter-intuitive aspects of metallurgy mean it is not a subject which is well suited to a narrowly focussed self-teaching effort by a lay person, regardless of their ability to focus, their intelligence and their experience.

So the current enthusiasm for G70 essentially originates from one guy: Steve Dashew, who again is a gifted and hugely experienced amateur, but he at least IS following his own advice ....

... but it's entirely possible he will never again encounter conditions which would test his anchor chain to the limit. Highly experienced people, late in life, are good at choosing shelter, predicting weather, and typically have nothing to prove by going into chancy situations. Even if that weren't true, he's only one data point, and a broken anchor chain is always going to be one of those "low probability, high consequence" events.

I don't personally know a single person who has been killed running a red light, but that doesn't make it a good idea.

[noelex 77]

Originally Posted by Andrew Troup

It wasn't the stretch: his rationale was that at any moment they might need to quit the situation and there would not be time to deal with the snubber

That makes sense, although I don't agree with the argument.

Doing anything at the bow in these sort of extreme conditions, even something simple like removing a snubber is difficult and time consuming.

I often wonder about those boats with complicated anchoring systems. If you start dragging It takes a long time, in those sort of conditions, to sort out multiple anchors and their connections. Even just cutting the anchors away is more difficult than it sounds, especially if factor in that it will be dark. (Anchors have a perverse preference for dragging at night )

I would still always fit a snubber in strong wind.

[Andrew Troup]

Originally Posted by noelex 77

That makes sense, although I don't agree with the argument.

Doing anything at the bow in these sort of extreme conditions, even something simple like removing a snubber is difficult and time consuming.

I often wonder about those boats with complicated anchoring systems. If you start dragging It takes a long time, in those sort of conditions, to sort out multiple anchors and their connections. Even just cutting the anchors away is more difficult than it sounds, especially if factor in that it will be dark. (Anchors have a perverse preference for dragging at night )

I would still always fit a snubber in strong wind.

Mate, all . you . need . is . some . decent . sized . chain.

No faffing around then, unless you go anchoring in the surf like some ... (You know who you are ;-0 )

[noelex 77]

I did have 13mm chain for 5 years on my current boat. I think the same as Kiwi Roa in the video (my boat is a bit smaller). I still always used a snubber with that set up.

For the last 2 years I have changed to 10mm G7. Wait what was that snap I just heard?