Selecting a Chain Grade

JHH5-14740

In the last chapter we covered chain types, based on an interview with two engineers at Peerless Chain, which makes the Acco brand that we recommend.

Now let's look at chain grades with a critical eye, based on our own decision-making process when we last replaced the anchor rode on Morgan’s Cloud.

  1. Introduction
  2. 4 Vital Anchor Selection Criteria and a Review of SPADE
  3. SARCA Excel Anchor—A Real World Test
  4. SPADE, SARCA Excel, or Some Other Anchor?
  5. Rocna Resetting Failures and evaluation of Vulcan and Mantus
  6. Some Thoughts On The Ultra Anchor, Roll Bars and Swivels
  7. Specifying Primary Anchor Size
  8. Kedge (Secondary Anchor)—Recommended Type and Size
  9. Third Anchors, Storm Anchors and Spare Anchors
  10. Anchor Tests—The Good, The Bad, and The Downright Silly
  11. Making Anchor Tests More Meaningful
  12. We Love The Way Our Anchor Drags 
  13. Things to Know About Anchor Chain
  14. Selecting a Chain Grade
  15. Anchor Chain Catenary, When it Matters and When it Doesn’t
  16. Anchoring—Snubbers
  17. Anchor Rode Questions and Answers
  18. Q&A: Hybrid Rope And Chain Anchor Rodes
  19. Anchor Swivels, Just Say No
  20. A Windlass That Makes The Grade
  21. The Perfect Anchor Roller
  22. Install A Wash-down Pump—And Save Money!
  23. Anchoring—Kellets
  24. Anchoring—Chain: Stoppers, Termination and Marking
  25. 20 Tips To Get Anchored and Stay Anchored
  26. Choosing an Anchorage
  27. Choosing a Spot
  28. 15 Steps To Getting Securely Anchored
  29. One Anchor or Two?
  30. Two Anchors Done Right
  31. It’s Often Better to Anchor Than Pick Up a Mooring
  32. Yawing at Anchor, The Theory and The Solution
  33. Yawing at The Anchor, an Alternative Cure
  34. How To Use An Anchor Trip Line
  35. ShoreFasts—Part 1, When to Use Them
  36. ShoreFasts—Part 2, Example Setups Plus Tips and Tricks
  37. ShoreFasts—Part 3, The Gear
  38. Gale And Storm Preparation, At Anchor Or On A Mooring
  39. Storm Preparation, All Chain On Deck
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Scott Flanders

John, very well thought out. We had elongated links added to the ends of Egret’s 3/8″ G4 chain at the factory allowing the larger forged shackle pin you suggested. For those who don’t have elongated links with existing chain, Wichard makes a special forged stainless steel shackle that well exceeds the chain’s strength.

We also had the chain re-galvanized twice. Once in the U.S. and once in New Zealand. The New Zealand re-galvanize was much better.

S.

Victor Raymond

Hello John,

This is excellent. Rajah Laut came with 1/2 in chain. It was a bit rusty at one end so switched it end for end. Sooner or later I am going to have to go through the same process as you have just done but I appreciate your blazing the trail. In the end I suspect the gypsy issue will be the hard one to swallow.
Thanks again for an excellent review (as always.)

Victor Raymond

Hi John,
Who wouldn’t like the thought of moving up to 400 feet AND still have a weight savings?
I wonder if there is any recycle possibility with older but good chain? Maybe ACCO as a manufacturer would be interested in a buy back program? I am probably dreaming here.
Thanks again.

David

What are your plans for the gypsy/wildcat issue? (Gyspy Wildcat sounds like a great name for a band, no?) We wanted to use 5/16 G70 for our system but our windlass mnfr (Lewmar H3) doesn’t offer a gypsy for it. They also don’t have a gypsy for 3/8″ HT (G40), which was Plan A, shot down in flames. We love the windlass – has performed flawlessly – but the sparse gypsy offerings are an issue. We ended up with 5/16th G40, which worries me a bit. I wasn’t aware that a custom gypsy was even a possibility. Have you heard of other windlass manufacturers offering them, or is that the sort of thing you can order from a good machine shop?

Eric Klem

John,

You are correct that most wildcats are cast although there is usually a bit of post machining and broaching for the keyway. I also think that your assessment that it would be too expensive to have a single unit machined is probably right. The block of raw material alone would be quite expensive. Looking at one, you would really need to build one that is 2 pieces bolted together (many already are) because otherwise the tool aspect ratio wouldn’t work since it gets pretty narrow pretty far into the part. To do the keyway properly, it should be broached(more $$) although you can sometimes cheat and machine one that is close if the depth is small relative to the key size. Lewmar actually has a bunch of .dxf and .stp files available so you would stand a pretty good chance of being able to put a model and drawing together for a shop.

If you can buy it rather than getting it custom, that will definitely be the way to go.

Eric

Eric Klem

I think that you made an excellent choice for your situation. I keep hoping that galvanized G70 with end links will become more readily available than it is now. For the time being, I use a size larger of G43 due to ease of purchase but I certainly wouldn’t mind going a size smaller with a higher grade.

If you old chain’s only problem is that it makes a mess, you have enough chain to set up a whole bunch of whaler sized moorings. Our mooring chain (much larger than 7/16) is old anchor chain from a much larger vessel that I used to work on which discarded it due to the galvanizing getting thin which doesn’t matter a bit to me when it is sitting down in the mud.

Eric

Henrik Johnsen

Hello..!
We used to have 60 m (200 feet) Stainless steel 13 mm anchor chain on our 47 feet, alu sail yacht, but when it started to show some corrosion in the welding’s we found it wise to have it removed. We also had some thoughts of getting a longer chain. A new SS was out of the question due to the cost, so we started the research on what to do. Mainly based on the many clever thoughts about anchoring from John here (thanks’ a lot..!!), we decided to go for a 10 mm (3/8”) G70 chain.
We ended up getting 120m (400 feet) Italian made 10 mm (3/8”) DIN 766 RINA certified Aqua7 Cert (G70) hot dip galvanized chain. On our request it was delivered with pear-shaped end links making it possible to fit shackles big enough to match the MBL of the chain. The new chain weighs just 2,3 kg (4,6 Lbs.)/meter so even if we the doubled the length, it only added the total weight with 50 kg (100 lbs.).
Until recently we used to have (at least) three anchors on board, located at the front in the anchor locker, but we´re getting more and more happy with our 55 kg SPADE as our main anchor. This summer we spent 6 weeks sailing north of Spitsbergen (80` North) and we just had to reset the anchor once, due to heavy kelp, so we told the old 35 kg BRUCE good bye..! That´s make us down to just two anchors, with a 35 kg SPADE as our second, giving us just 15 kg (30 lbs.) added weight all over.

David:
We have a LEWMAR Ocean3 windlass and had to get a new DIN 766 10 mm gipsy, witch it took us about 8 weeks to get..! Our dealer here in Norway told us they´re having a hard time getting spare parts from Lewmar on a general bases. Obviously Lewmar don´t pay much attention to the after market, witch’s a shame since they have very well functioning products.

Jon Valen-Sendstad

interesting to hear about your chain decission, I am in the same situation and plan to change my 90 m 12 mm chain (of unknown quality and origin) into 100 m of 10 mm. Can you tell me what vendor/manufacturer to contact ? And what was the cost of your 120 m ?

Jon

Nick Kats

Great article, John. Consistent with your previous writings, and neat to see a specific example. G7 is the way to go. Though I find the prospect of custom fabricating a wildcat a bit intimidating.
My input here is: it is easy to add rope to the chain to lengthen the scope. Or use all rope with a secondary anchor (with a little chain). In my case I can use perhaps 1200′ of minimum diameter 3/4″ rope, which is in 250-400′ sections.

Dick Stevenson

Henrik,
Can you say more about your chain purchase: contact person, Manufacturer of the chain, were the larger links executed by the manufacturer or a secondary shop?
Thanks,
Dick Stevenson, s/v Alchemy

Colin Speedie

Hi Dick

Henrik may have got his elsewhere, but the original supplier would almost certainly have been Maggi of Italy, their Aqua 7 chain. This has been rather difficult to get hold of outside Italy before, but I see that Jimmy Green Marine (good firm) are now offering it in the UK.

Best wishes

Colin

Henrik

Hello..!
Sorry for my late reply.
As Collin suggesting, we got our Aqua7 chain directly from Maggio Group in Italy.
They was very supportive during the mail contact we had previous to my order. It took about four weeks to produce the chain, and all together it took 6 weeks from my order was made until it was delivered on my door step.
120 m Aqua7 10mm DIN 766 RINO certified chain was EUR 1600,- inclusive shipping, (exl VAT, since Norway isn’t a member of the EU) but then again I had to pay 25% Norwegian sales tax to get it through the custom.

Henrik

Jon valen-Sendstad

Thank you for the information. It is getting expensive I see. New anchor (Spade or Rocna) + New Chain = Euro 2500 , more or less. But probably Worth it, I can get rid og 100 kg Chain and ad 20 kg to the anchor it self.
Jon

Henrik Johnsen

Jon
Yes this solution will make your wallet thinner, but for sure it increased our quality of sleep during anchorage.
Our intention, exept swapping, was adding more meters to the anchor chain, rather than saving weight, and in the combination of a heavy (55kg 110lbs) Spade anchor, we now feel very secure when at anchor. The possibility to add some extra meters of chain when the wind picks up, helps the anchor to stay put. We think that this feeling of security is well worth the the cost of the ground tackle rig.
Henrik

Chris

Hi Henrik & John
Thank you for you recommedation on Maggi. I went the same route. 100 m of G70 8 mm chain + certifiate was delivered within 4 week from making the order.
John, am about to order a Rocna. Web site table suggests 25kg size for my yacht (40 ft, 13,000 kg, double ender, long keel ketch). Based one your and forum members commenst I should go at least on size (33kg) and possibly two (45kg) up. It that correct. My windlass in Lofrans Falocon (1700 W engine).
Many thanks & greetings from Poland.

Dick Stevenson

Thanks Colin, I have been in touch with Jimmy G. Mar. and felt good about their product, but it is good to get confirmation. Dick

Alex

Hi John
Do you have any thoughts in regards to Acco’s “short link” version of the G-70, in comparison to the NACM, long link one?
The reason is that i shall probably be able to get a stock gypsy for my windlass if i go with the “short link” version, whereas the NACM long link one would require a custom gypsy, which i find a bit intimidating
I know WLL is the same, and that Short Link is slightly heavier (154lb/100ft vs 134 on NACM). I was wondering if stacking in the locker could be an issue.
Thank You
Alex

Alex

Hi John – thanks for the quick reply
I think what puzzled me is the fact that Peerless’ website has 3 versions of the G70 chain: “Grade 70 Domestic Transport Chain (NACM)”, “Grade 70 Import Transport Chain (NACM)” and “Grade 70 Import Transport Chain (SHORT LINK)”. They all have the same WLL, but Link size varies, especially in the case of the “short link” version. Weight per ft is slightly lower with the longer link as well (some 12% difference).
I checked with my windlass manufacturer, and they have a stock gypsy that seems to accomodate the Short Link version (pending confirmation with a sample of that chain).
I was wondering whether there would be any difference in performance between the Short and Long link versions. My guess is that the Long Link may perhaps stack slightly better thant he Short Link inside the locker.
Best regards
Alex

Wil

Hi John,

I was hoping for an update on this article. I’ll be replacing the CQR on my soon-to-be boat with probably a Rocna and would like to go with G70 chain. As Alex mentioned above, there is a ‘regular’ link length G70 3/8″ (NACM) Acco chain http://chains-fittings.peerlesschain.com/viewitems/grade-70-chains/rial-chain-grade-70-domestic-transport-chain-nacm-? , and a ‘short link’ G70 3/8″ Acco chain http://chains-fittings.peerlesschain.com/viewitems/grade-70-chains/-chain-grade-70-import-transport-chain-short-link-? chain. Neither one comes even close to Acco G43 3/8″ Domestic Hi-Test ISO chain in link dimensions. But I’m not telling you anything new about the G70 Acco Domestic NACM chain, we know it ‘doesn’t fit’.

Long preamble, here we go: how did you do for finding a G70 gypsy for your G70 chain? Did it end up costing you a bundle? What about starting a thread on what you and others consider to be the better quality anchor winches with the best selection of chain gypsies, maybe even a G70 gypsy (I saw that Lewmar makes one with a long lead time)?

It looks like the Acco G70 needs to be hot-dipped, and you mention having the large links put on the ends. I couldn’t find it on Defender, I have a question into them asking about it. Do you know of other domestic sources for G70? I am aware of G70 at Jimmy Green Marine in the UK, and West Marine has it at bend-over prices http://www.westmarine.com/acco—grade-70-hot-dip-galvanized-high-strength-chain—P005_154_001_512 , I’d like to find it at a better price if possible. Thanks, Wil

Wil

Thanks, I missed the Windlass requirements chapter and have read it. I’ll be looking into Ideal and Lighthouse windlasses, great to know. Is your windlass an Ideal? Where did you have the G70 gypsy made?

I would indeed like to push Defender a bit more. Would you be willing to PM me the invoice# (if it’s easy to find) of your Defender G70 chain purchase? If not, what date (as close as you can remember) did John Harries (was it in your name?) buy it?

Hope I’m not being too pushy with the questions here…..

BTW, the 3/8″ G70 ‘short link’ chain is 0.030″ shorter than 3/8″ G43 chain (1.19″ vs. 1.220″) and 0.050″ narrower than G43 (0.55″ vs 0.600″). I guess the only way to see if it will work on a G43 gypsy is to try a length of it out……would the dimensional difference be cumulative, as the short link G70 is wound in by the G43 gypsy……

Wil

John, as mentioned above in my June 22 post, here is Acco ‘short link’ G70 chain: http://chains-fittings.peerlesschain.com/viewitems/grade-70-chains/-chain-grade-70-import-transport-chain-short-link-? chain , 3/8″ link dimensions are: 1.19″ x 0.55″
‘Regular’ Acco G70 here: http://chains-fittings.peerlesschain.com/viewitems/grade-70-chains/rial-chain-grade-70-domestic-transport-chain-nacm-? , 3/8″ link dimensions are: 1.374″ x 0.551″

Wil

PS, I did find another source of G70 domestic chain at a much better price http://www.1st-chainsupply.com/chain/gr70_bulk.htm. I have a question into them.

Wil

Wil

Eric, thank you for the benefit of your experience. There is indeed a lot to weigh. One thing I’m not clear on….is your G43 chain 3/8″? You could have gone with 3/8″ G70 chain and saved some weight, no? Or 5/16″ G70 ?
Wil

Dick Stevenson

Wil, Another windlass to consider is Lighthouse. We have 15 yrs with ours, probably thousands of anchoring situations, and I would be hard put to think of any improvements I would make on it.
Dick Stevenson, s/v Alchemy

Wil

Hi Dick,
I’ll have a look at Lighthouse winches, thanks much.
First question to them: do you make a G70 gypsy?
Regards,
Wil

Wil

Dick & John,
Here’s the reply to my inquiry about a G70 gypsy from Lighthouse:
Dear Wil N. Stevenson,
Thank you for your interest in our products. The 1501 series can accommodate all of the Calibrated ISO chain sizes and grades up to 7/16″ Size. We do make gypsies for the G70 sizes. However, the ACCOR G70 measurements are somewhat different than what Peerless chain quotes. Go 70 chain is a transportation chain which is quite different than anchor chain in that its metal chemistry is Boron Manganese Steel heat treated for hardness. This is where the strength comes from ordinarily this is not used as anchor chain because it is very brittle and lacks elongation modulus and it is not calibrated to run over chain wheels repeatedly. This was popular during the early 80’s on Tournament Sport Fishers but soon died out due to many broken anchor rodes. However, we still make gypsies for these chains.
The best anchor chain presently available is the ISO Gr4 Hi Test chain which accepts hot galvanize vey well and was developed by our US Navy to increase strength and serviceability in the 104′ gun boats. In that case they were able to decrease the size from 1/2″ to 3/8″ ISO Gr4 chain yet increase the strength of the rode. You will find this type chain on most voyaging yachts and off shore commercial work boats these days.
J. Walker

Wil

Thanks John, I’ll look into it a bit further, get some more opinions.

Wil

Oh yeh, I know about the internet and its ‘opinions’. I was specifically thinking of Ideal to talk to next. But they might also have the same belief system about G70. I was really curious about Jordan Walker’s quote “This was popular during the early 80′s on Tournament Sport Fishers but soon died out due to many broken anchor rodes.”. Did that indeed happen? Not disparaging Jordan in any way, just wish there was some way to verify statements like that.

Eric Klem

Hi Wil,

Here is one more internet opinion on this. There has been a lot of talk about whether G70 chain is brittle and it really isn’t. From a performance standpoint, what you should be concerned with is energy absorption and tolerance to defects.

From an energy absorption standpoint, it is important to look at the big picture. Anchor loads are dynamic loads so you can’t look at them as a simple static number. The more energy absorption you have in the system (this is a generalization and ignores tuning the system), the lower the peak loads will be and it is those peak loads that give you the issues, not the average load. The dampers that you have are the anchor dragging, the chain catenary, chain drag through the water, chain stretch, snubber stretch and the bows drag through the water. If you change to lighter, stronger chain, you change both the chain stretch and the catenary. Catenary has been discussed a lot and while you get less damping with lighter chain, the amount of damping from this is so low in extreme conditions that it really doesn’t matter. With chain stretch, it is similar. In storm conditions, your snubber might be stretching 3-4′ and your chain might be stretching 6″. Therefore, how much energy I can get the chain to absorb through stretching does not worry me, I worry about keeping the snubber intact. If you look at the ultimate limit of the chain, lower grade chain can absorb more energy relative to its ultimate strength than higher grade chain as it continues to carry a load for a relatively large displacement after yielding. However, this difference occurs at stresses which in my opinion, you should never see with properly sized chain. If you look at the account of the Sundeer 64 that rode out a cat IV/V hurricane in Grenada on 3/8″ G70 chain, they reported that their chain did show elongation although their snubber parted so there must have been huge shock loads. This boat did experience conditions which caused their chain to yield and they would undoubtedly have been slightly better off with 7/16″ G43 but that is a big boat for the chain and the conditions were horrendous so I don’t think that this isolated incident is an issue. For energy absorption, I like to try to keep a good snubber intact and not rely on the chain, especially loaded past the yield strength.

Regarding tolerance to defects, bigger chain is going to be better. If you loose 1/16″ to corrosion, that is a big portion of a 1/4″ chain but not nearly as big a deal on 3/8″ chain. The same thing applies to notches which cause large stress concentrations. For our own boat, we use G43 chain and I have never considered G70 as it would mean going with 1/4″ chain which is simply not tolerant enough for me and would need to be replaced sooner with corrosion.

I hope that this is helpful. There is a lot of stuff to weigh and if I were in John’s shoes, I would probably be looking to G70 like he did but for other boats lower grades can make sense.

Eric

Wil

Eric, thank you for the benefit of your experience. There is indeed a lot to weigh. One thing I’m not clear on….is your G43 chain 3/8″? You could have gone with 3/8″ G70 chain and saved some weight, no? Or 5/16″ G70?
Wil

Eric Klem

Hi Wil,

My chain is 5/16″ G43. I tried to size my system for 3600lbs which comes from the ABYC recommendation for sizing a permanent mooring for our boat (rounding up 36′ to 40′). At first glance, it would appear that 1/4″ G70 doesn’t have quite enough strength at 3150 lbs WLL but it is actually stronger than 5/16 G43 (12,600 versus 11,700), they just use a safety factor of 4 on everything but G43 which uses 3. Going to this 1/4″ G70 chain would save me almost 1/2 lb/ft but I feel that 1/4″ chain is simply too small for a cruising boat. This is only my opinion and you could certainly cruise safely with the small, strong chain it is just more sensitive to corrosion and abrasion. If I were deciding between 3/8″ G43 and 5/16″ G70, this would not be a big concern for me but our boat is small enough that we don’t need that type of strength.

The other thing about G70 chain is that it is actually marginally lighter than the same size G43 chain due to link geometry. I would doubt that most applications would have a compelling reason to compare two chains of the same size but significantly different strengths so this probably does not matter.

Eric

Dick Stevenson

Wil,
The “J” in J. Walker is Jordan and from my point of view, he is a jewel among marine vendors (as is the company and product).
Dick Stevenson, s/v Alchemy

Wil

Thanks Dick, good to know Jordan is a knowledgeable person.

Sam

This is so much more than I ever thought I needed to know about anchor chain. Thanks for the indepth examination . I’ve been enlightened!

Torbjørn

Hi,

I have a question regarding rigging of the snubber. From the post above the need for a snubber to reduce the shockloading on the system is pretty well documented. But how do you rigg the snubber? Specifically how do you connect a nylon snubber rope onto the chain at a point which is not the bitter end (with it’s G70 pearlink and appropriately sized shackle) without introducing a weak link in the whole setup?

Torbjørn

Eric Klem

Hi Torbjorn,

I realize that your post is directed at John but I thought that I would jump in and mention a method that has been gaining in popularity recently. We have been using this method and I feel that it represents the best method for us at this time.

What we do is splice an eye in the end of the 3 strand nylon snubber around a stainless steel thimble. We then attach this eye to the chain using a “soft shackle” made from dyneema which is simply passed through the middle of the chain link. Soft shackles typically have a breaking strength of around 1.75X the line strength. We use 5/16″ chain and a 3/16″ soft shackle fits really easily but we have a 1/4″ one for our storm snubber which works fine but takes an extra 5 seconds to put on. These have approximate breaking strengths of 8500lbs and 13500lbs. We use G43 chain which has a breaking strength of 11700lbs so our storm snubber attachment is stronger than the chain. If we went to G70 chain with a breaking strength of 18800 lbs, it would be slightly weaker. If we wanted to compare 3/8″ G70 (26000 lbs) our attachment of a 5/16″ soft shackle would be good for around 21500 lbs. I guess that the answer is that it isn’t quite as strong in absolute single pull terms but it still gives a reasonable safety factor when compared to the expected loading. Because of the low stretch properties of dyneema, you don’t need a really high safety factor like you do for nylon.

UV will degrade dyneema over long periods of time so that is important to keep in mind. There is also some wear on the soft shackle but my best guess at our replacement interval is probably 200 nights at anchor which is reasonable and as good as the snubber itself. Besides anchor technology, I actually think that dyneema has been the biggest improvement for our safety of anchoring/mooring in recent years. We actually attach the boat end of our snubber using dyneema (the downside is you can’t adjust the length of nylon) as well as our mooring pendants and this has virtually eliminated chafe for us because there is no movement through the bow chocks but we still retain the shock absorbing characteristics of the nylon.

Eric

Torbjørn

Eric,

I though that was an excellent reply and a lot easier a solution than the industrial chain hooks that I have been looking at! I have to say I love these high strength dyneema lines.

Have you used this setup in a storm situation as well? No chafe problems?

I would be interested in hearing solutions from other people as well. Though this did sound like an excellent solution!

On using high modulus lines out past the leads on deck, i definitely agree. I have spliced up some old dyneema core halyard rope with an eye in either end and in swelly marinas use this to the exit of the lead. Then tie the mooring line into it. No creaking from mooring lines, no chafe, and only a very small sacrifice of elasticity.

Thank you for a good reply!

Torbjørn

Eric Klem

Hi Torbjorn,

We added different dyneema parts in phases so it is a bit hard to remember exactly what conditions each part has been subject to. I am pretty sure that the worst prolonged conditions the soft shackle has seen are on the order of 40 knots sustained gusting to around 50 with about a quarter mile of fetch so not much wave action. We did have about 20 minutes of 50 knots and 2 miles of fetch in a thunderstorm this summer which had some pretty good chop making the boat jump around a lot. It is worth noting that we have never used our storm snubber so this was all with the 3/16″ soft shackle on a 36′ 17,000lb boat. The only damage that I have ever seen on the soft shackle was where I had one strand get slightly frayed in a specific area but I don’t know the exact cause. These conditions are far from extreme conditions so I can’t say for certain that this method would work but I feel it is the best compromise of ease of use and security.

Our mooring pendants are much heavier duty (2X 1″ double braid nylon to 3/4″ dyneema) but they have seen significantly worse weather. They have dealt with 4-6′ waves on multiple occasions and show no signs of wear when many other boats nearby have broken free or had severe chafe. We are almost never at a dock but I have often wondered why people do exactly what you do with a piece of dyneema going through the fairleads so it is nice to hear that you are doing it and finding that it works well.

Eric

Dick Stevenson

Dear Torbjorn,
You asked about attachment and I concur with John about the use of rolling hitches. We have used a rolling hitch on a long snubber for 20-30 years without a problem. A couple of additional thoughts:
John mentions double in his reference to Wikipedia on rolling hitches. If the same as we use on Alchemy, he means to add a loop at either end of the knot. This takes a moment longer, but makes it easier to untie after load and adds a bit of security.
Like all knots, but particularly with those that unload and load regularly, taking a second to tighten up the knot on the chain really helps. A loose sloppy rolling hitch may “roll” on itself under big load otherwise.
Unlike most ground tackle decisions, less is more with snubbers (stretch is the goal). I used 3/8” 3 strand nylon on my 12 ton boat and 7/16” on my 16+ ton boat. Chafe is too boat dependent to comment on, but my snubbers last 2-4 years of 75-100 nights a year anchoring.
Strength is not an issue with these snubbers if high quality nylon 3 strand is bought. Remember, we are talking about anchoring a boat, not mooring it (anchored boats are regularly attended).
I am not sure what the advantage is to the dyneema system as described. It sounds more complicated and harder/longer to execute.
My best, Dick Stevenson, s/v Alchemy

Eric Klem

Hi John,

I am using the dyneema for the attachment on both ends but the snubber is still primarily nylon. We do this mostly because of how fast and easy it is to take on and off (easy to do with one hand in the dark in under 5 seconds and never jams or falls off) but it has also proven to be extremely chafe resistant. The real key with this system is the soft shackle.

Eric

Eric Klem

Hi John,

I make up my own soft shackles using Amsteel because that is what I have around. For the soft shackle on my normal snubber, I use the “better soft shackle” design on L-36.com as it is easy to work with and secure (other than our storm snubber, this is the type we use exclusively on the boat). Our storm snubber has a larger diameter Kolhoff style soft shackle as the “better soft shackle” won’t fit through the chain nicely in the bigger diameter. I hadn’t looked at the L-36 homepage in a while and I just saw that they have a “high strength soft shackle” developed in conjunction with Brian Toss and Evans Starzinger which apparently has a strength equivalent to 230% of the line breaking strength instead of 175% which sounds kind of interesting. This soft shackle is simply looped through a chain link and through an eye splice in the nylon with a thimble.

Looking at my post above I realize that I wasn’t clear on the boat end of the snubber. For this, we put a brummel splice in a piece of dyneema and cow hitch it into an eye splice in the end of the 3 strand nylon. I really like how this works on our mooring pendants but I have some mixed feelings with the snubber because of the inability to adjust the amount of nylon although I don’t worry about chafe at all anymore.

Eric

Eric Klem

Hi John,

I was thinking about this subject again seeing the recent comment exchange on Colin’s snubber post and realized that I should update this information. We still use the “better soft shackle” design for normal anchoring but I have now made up a few of the “high strength soft shackle” variety to go with our storm snubber. Both of these types result in the same maximum line diameter so they fit through the same size chain link but strength increases from ~175% of line strength to ~230% when going to a well tied high strength one. For us, this means that we now have a 3/16″ soft shackle on our storm anchor rode instead of a 1/4″ one which fits through the 5/16″ G4 chain more easily and is now stronger than the chain.

I find the high strength version to be slightly less convenient to use so it is not our everyday one. It also took a while to find good instructions for how to tie the knot.

Eric

Eric Klem

Hi John,

We use several soft shackles around the boat right now. I have found them useful instead of steel shackles in cases where I don’t want the noise or danger of a steel shackle. Because we have hank on headsails and switch them regularly, we use one to attach the jib sheets. I have been pleasantly surprised with how secure they are even with a badly flogging sail.

If you find other good uses, I would love to hear about them.

Eric

Erik de Jong

Hi John,

I’ve read your anchoring chapters a few times now, as well as similar stories on other websites (Rocna’s for example) and I conclude that the only advantage to a higher grade chain seems to be weight saving, but it comes at a high cost.

Upgrading the quality of the chain is a very good option to make the boat go better through waves, but in some cases, and that really depends on the boat and it’s layout. You can keep the money in your pocket by moving the chain into the keel and remove ballast from your boat instead ie. use your chain as ballast. Another advantage is that you have no chain at all in the bow anymore and the winch can go at the foot of the mast as well, shortening the length of the cables significantly.

The difference is that the chain needs to travel a long way over your deck, basically from the mast base to the bowroller, which unfortunately can not be incorporated on every existing boat. The disadvantage is that it causes a lot of noise on the deck, and it requires protection as well in order not to damage the deck, the advantage is that you have several meters of chain exposed at the time, making visual inspection “on the go” a lot easier.

The articles I read on this topic, including yours, are all complete and thorough on the subject of differences between the chain types, my compliments for that.
The only thing I’m missing is that there are, as with every problem, more solutions to choose from, in this case one with a better end result and at much lower cost.

Jon Valen-Sendstad

Confused about size of anchorchain!
By now I must have read everything available on the web, including these posts, about selection of chain and loads on the rode/chain. And what an amount of different methods and opinions I find out there! Mostly helpfull, but also confusing.
There is a lot on whether to chose BBB, G40, G43, HT or Grade 70, galvanized, stainless or combination of rope and chain. So, yes, everybody seem til land on G43 or G70, for saving weight and/or increasing length, but there is hardly any conclusive discussions about the load you have on the chain.
So which «facts» to rely on? ABYC states that my 50 ft (15m) sloop will have 6400 lbs force on the rode in 60 knot wind, wheras a much refferred to author, Robert Smith (nav.eng), claim to have measured on a 51 ft. sloop in 60 knots wind only 2211 lbs.
It is known that the figures from ABYC include a large safetyfactor (but not known how big)and that the figures from Bob Smith are actually measured numbers (and including 30 deg veering and waves), and for all boatsizes and winds they are far smaller than ABYC.
I tend to believe in Bob Smiths figures and will use them in calulation of my chain. I have allready decided to use a Aqua 70 from aquachain. (Thanks to Henrik on this site)
The chain manufacturers use from 3 to 5 as a safetyfactor (Aqua 7 use 5) in order to calculate SWL from MBL, so there should be no need to add safety more than once. What you need is the real load, namely Bob Smiths values or other measured or correctly calculated, multiply them with 3, 4 or 5 (dependendt on chain type and application), and you end up with your minimum MBL.
So my boat, the 50 ft, sloop, will need a chain with a MBL of 11.055 lbs (5X 2211) in order to withstand the force from 60 knots of wind.
I have allready decided on a 40 kg Rocna, and Rocna recommends a 8mm G70 chain for this size of anchor.
From this I conclude that an 8 mm Grade 70 chain with MBL of 7000 kg ( 15.555 lbs) is more than strong enough.
Right or wrong?

Best regards
Jon Valen-Sendstad

Eric Klem

Hi Jon,

You have hit on one of the most frustrating things to me in terms of anchoring system selection which is the expected loads. The short version of my post is that I would tend to agree with John’s reply. A few years ago I spent a lot of time trying to look at the small amount of data available on these loads to try to make sense of it. There has been some effort to look at this from both a static and dynamic standpoint although no one has put in the effort to create a really good predictive model. I think that the takeaway was that there are a ton of factors that can influence the loads so it is really tough to accurately predict them. Because of this, it comes down to how conservative you are in your assumptions.

Selecting the expected load really starts with what the worst weather you expect your system to work in is. For me, I try to size around 60 knots steady in a reasonably protected anchorage (less than 0.5 miles of fetch) because we end up anchored out in nor’easters from time to time and have been aboard for a few tropical storms. If you expect your main anchor to be adequate for hurricanes in Florida, you would need to go to a much higher speed and if you only want to daysail and don’t expect anything worse than a 35 knot thunderstorm, you could size for much less wind. In truth, while I have given a value in terms of windspeed, it may be more useful to look at a number like wave height if you plan to anchor out in rough conditions.

From here, I like to use the ABYC table to get my expected load. As you state, they applied a safety factor but it is necessary due to dynamics. It is true that in most cases the prediction is significantly higher than the actual but this is really only true for the lower windspeeds where the dynamic loads are not present. If you are in an area with lots of fetch, there is evidence to suggest that the ABYC underestimates the loads for high windspeeds as it is based on static and not dynamic forces. Keep in mind that your chain and snubber setup will have a huge effect on the loads. I think that the other thing that goes on is differences between average and peak windspeeds. Many people talk about peak windspeed as if it is the average when in truth the reported average windspeed will be far lower. Unless you are really confident that your boat sits there virtually motionless regardless of fetch and gusty winds, I find it hard not to use the ABYC numbers as the actual load numbers. In really bad storms, these numbers may even be low.

I then compare the load against the chain strength and this is where I apply the safety factor. This safety factor does help account for some error in the load (especially important in bad conditions where dynamics are present) but also some wear in the chain and fatigue. I feel comfortable with a 3:1 safety factor here.

Back to your original question of whether 8mm chain is sufficient for your 50′ boat. If we assume that it is of a moderate design and displacement and you are targeting 60 knots of wind, I would conclude that 8mm G70 is just slightly too small so 10mm would be appropriate. If you don’t expect to see these types of conditions or you are willing to accept much more risk, then you might consider it reasonable.

I don’t know how much bad weather you have anchored this boat through but you can learn stuff from your previous experiences. The easiest way that I can think of is to look at your snubber which is often the weak link. If you have been through the worst weather you ever expect to encounter and your snubber held, it gives an indication that the loads are probably lower than the strength of the snubber.

Eric

Dick Stevenson

Hey all,
Am I correct that the primary relevant measurement that should be used for forces on ground tackle is displacement, not boat length?
Also, for our purposes, is there any reason (for us) to use any other chain measurement stat other than SWL (safe working load) as long as you know the safety ratio it is working from. It is my take that any forces on the chain above the SWL harm the chain such as the fatigue issues that have been discussed in other contexts. If that is the case, it might be best to leave all the other measurements: MBL, UBL, WLL (working load limit, may be the same as SWL), etc. to the engineers as it for sure confuses me often.
Dick Stevenson, s/v Alchemy

Eric Klem

Hi Dick,

I wish that there was a single attribute that could be used to predict loads but I am not aware of one. In areas without many waves, the major force acting on the vessel is the wind so what is important is the resistance to it and how much the vessel sails around. In areas where there are large waves, these become the major outside force and displacement, hull shape, rotational inertia, etc become really important. Given that most people here size for storm type conditions, I think that displacement is probably the best measure that we have as it correlates reasonably well to the amount of energy that must be dissipated but it is still far from perfect. As Nick very rightly points out, the boat’s behavior is really important in all of this. Also, don’t discount the important of the rode as an all chain rode with no snubber will generally result in really high dynamic loads. Because the loads are so hard to predict, that is why I like to use the ABYC numbers as even if they are a bit conservative on average, they hopefully account for all of these issues.

Yes, using the SWL is a fine way to size the chain. The reason that I don’t do this is that the definition of SWL is not consistent which means it isn’t an apples to apples comparison but it is still safe.

Eric

Nick Kats

Dick
Displacement alone is not a good guide.
Take two boats of equal weight but one has far greater resistance to wind.
Or compare a boat that sails viciously at anchor, enormous jerking loads combined with extreme directional instability, with a boat that lies to peacefully, never veering off the eye of the wind, resistance to wind consistently at minimum, directional stability absolute.

Dick Stevenson

Nick,
Thanks for your thoughts. Yes, if equal displacement, the boat that catches more wind will exert more pull on the rode. I was questioning what was the most powerful determinate of rode pull for choosing anchor or chain size.
Face validity argues for windage (length of boat, rigging etc) being a primary consideration. However, in my casual observation of anchorages under siege, the lighter boats seem to not work their ground tackle nearly as hard as heavier boats, even if the lighter boats are larger and have more windage. Maybe it helps to think of a large cork boat with a great deal of windage, but almost no weight and image how little its force on the rode would be.
So, following the above, windage matters because it moves the boat, but displacement is primary as it is what exerts the force when the boat fetches up on the rode after a run-up during a gust or when a wave slaps a boat back. Lighter boats just can’t compete.
So, I might choose heavier ground tackle for a 40 foot boat than a 50 footer if the 40 footer had more displacement.
Thanks for the dialog.
Dick Stevenson, s/v Alchemy

Marc Dacey

Dick, in light of this useful discussion (particularly as “my” Alchemy has plenty of windage from the pilothouse and raised aft deck), I would be interested to know if you favour the use of a riding sail at anchor, and, in general, is there any data that can relate the use of a riding sail to the mitigation of loads on chain rode?

Yes, I realize that’s a vast engineering data set, but I was hoping to relate area of riding sail to reduction of “hunting” at anchor, and said reduction to the lessening of sheering loads on the rode and anchor. Even in a ballpark sense.

Nick Kats

Hi Dick, yes I agree displacement is the starting point. But I take it a lot further.
My experience of sailing at anchor with my current boat & with my last boat is extreme, probably more extreme than most will experience.
In intense squalls my last boat sailed at anchor something vicious. My current boat sits pretty in worse conditions – she hardly wiggles. The difference between the two was huge.
Assuming equal weight, my old boat probably needed an anchor 3 to 5x the weight of a similar anchor for my current boat.
Regardless of anchor size, a boat that sails viciously at anchor is simply not seaworthy.

Dick Stevenson

Erik,
Thanks also for your comments.
Also agree that there is no single attribute to predict loads. Also that there sh
Take your example of an anchorage well protected from waves where you argue that wind strength is the major force. I might suggest that wind is the motive force, but that displacement remains the most potent contributor to rode load. The wind gets the boat moving, but when it stops, it is the displacement that contributes most to rode load. This is made even more potent as, in challenging weather conditions, ity never fails to amaze me how variable the wind actually is.
Again, as written in my earlier email before I read yours, think of a vessel made of cork.
On the other subject, I am aware that the safety ratios for SWL vary, but are the other measurements, usually referring in some way to breaking load, consistent company to company, country to country?
As always, thanks for the dialog.
Dick Stevenson, s/v Alchemy

Eric Klem

Hi Dick,

Breaking strength should be comparable across all manufacturers in this application.

Eric

Dick Stevenson

Marc, I have no sustained experience with a riding sail, but if you could get it to act like a mizzen sail, I believe it could make an appreciable difference. My previous boat was a yawl which we cruised Bermuda to Maine for 15+ years. Generally, the mizzen would go up at the beginning of a holiday and would not come down till a month later, with occasional reefs thrown in when circumstances requested it. It made a big difference in storms/squalls. I would stay nailed to the wind, just like a wind vane. Casual observation on my part of boats with riding sails indicate some help but not to the degree of the mizzen. The “wedge” type riding sail appeared to be most effective.
My best, Dick Stevenson, s/v Alchemy

Marc Dacey

Thanks, Dick. I have two backstays going from the mast-top to the stern quarters, and the “wedge” riding sail should work well.

I agree on the mizzen. Had there been a reasonably priced steel cutter-ketch available to me when we bought our boat in 2006, I would have chosen that over a cutter, but I’m not unhappy with a cutter…I just would have preferred a cutter-ketch.

Dick Stevenson

Thanks Eric. That is what I would have supposed, but I have been mistaken before. Dick

Dick Stevenson

Marc, I loved my yawl a great deal, sailed well and was quite lovely, but I would not trade my present cutter for any other rig. The cutter (mast almost amidships) is just too efficient and versatile. The mizzen doubled a lot of the rigging work and made for a lot of dodging and weaving when moving around the stern of our previous boat. Sure was “salty” and pretty though. Dick

Dick Stevenson

Nick, Agreed and find your description of your previous boat unsettling. I think I was anchored near you a decade or so ago in Block Island. Glad your present boat behaves better and, yes, these boats that sail around do become un-seaworthy, if only because they can be a danger to others who do not anticipate their antics. Dick

Bryce

Hi all,

It’s chain replacement time on Aquabat, and I was wondering if anyone has any real-world experience with using Armorgalv for anchor chain?

I have spoken with the Australian Armorgalv representatives and they had some interesting comments. From what they’ve told me, I understand that navies are starting to use it, and it has apparently been used successfully on fishing fleets in northern Queensland (Australia). Their view is that it has some good properties including:
– Lasting twice as long as hot-dip galvanising in abrasive environments
– Flowing smoothly through the gypsy throughout it’s entire life (less chance of jumping off)
– Not introducing any hydrogen embrittlement during the galvanising process (especially important when talking about high tensile chain)

I’m mindful that due to it being a relatively recent technology, it doesn’t match with John’s requirements for use on a voyaging sailboat, and I’ll have to keep that in mind as to whether we want to be trendsetters.

Any practical experiences with it would be much appreciated.

Regards,

Bryce

P.S. For those who are searching for more information on various chains, practical-sailor have just recently published their review of galvanising coatings of various chains in their current edition.

Bruce Savage

Hi John
I am looking at replacing our Allures 44 anchor chain, which is 80 meters of 12mm G30 = about 260 kg. That’s a lot of weight on the bow! The Australian marine industry appears to be somewhat in the dark ages on higher tensile anchor chain and pretty much everyone here will tell you that Grade L (= G30) chain is the one to use. From my research so far I cannot source G40 or G70 hot dipped galvanised chain in AUS. Moreover I also cannot replace my 12mm chain because the chain here is in 8,10,13,16mm, they skipped the 12 for some reason.
I am looking at an option to import chain from New Zealand where a supplier deals in the Maggi Aqua 4 and 7 chain which looks very good.
The 8mm Aqua 7 looks like the right one for us and at the same length would take a massive 150 kg out of the bow.
I fully understand and agree with the chain weight having no effect on catenary for ultimate holding. My question is whether the lighter chain will effect the anchoring characteristics in milder conditions? I have observed that with the heavy chain in lighter winds the boat is often pretty much held by the chain weight on the ground, which effectively gives a shorter swing arc. The chain may be very curved on the bottom and only tend to straighten or drag when the wind is stronger. My concern with the lighter chain is that it will have less of this effect, which will make the boat swing around on a larger arc. Also the chain would therefore probably be exposed to more abrasion over it’s life. I am very interested if anyone has any real world experience of changes of a boats anchoring behaviour when changing to lighter chain?
Bruce

Gerben SYD

Hi Bruce, I was l0oking at that same Maggi Aqua 7 chain from Chains Ropes & Anchors NZ and it looks like a nice chain, but at a cost! Just like you I also found that here in Aus, the grades of chain are not in synch with what the rest of the world is using. Did CR&A say that they would put larger end-links on that 8mm chain? Otherwise, how are you going to get a similarly rated shackle between the chain and the anchor? Did you talk to Muir Winches in Manly Vale, North Sydney? As windlass makers, they know a lot about chain as well. If there is any decent chain in Aus, they would know.

Gerben SYD

Hi Bruce, it seems that AS/NZS 4344 may be similar or the same as NACM Grade 70 standards: see this product PDF: https://www.beaver.com.au/documents/catalogue/pdf/Section10_10.pdf
Also, that matches with Peerless description of G70 chain (http://www.peerlesschain.com/products/Grade-70-Domestic-Transport-Chain-NACM/), as cargo lashing chain, which is how it is referred to here: LC70 or L70. The Italian made Maggi G70 chain is made to DIN766/A standards. Overall, I am confused about these standards and the WLL of these different chains.
This Victoria based manufacturer, PWB makes LC70 chain, in that gold coloured galvanizing, but they also offer that same chain (??) in a hot dip galvanized version called fathom chains, that have the larger end links, so that they can accept hi-strength shackle pins. They write about this chain: “Manufactured from Grade L Chain with additional end link fittings, PWB Anchor Fathom Chains are supplied in a hot dip galvanised finish for added durability. 109 metres. The maximum working load stated is based on a Design Factor of 4:1. Fathom Chains are NOT certified for industrial lifting. Test certificates supplied.” but these fathom chain start at 10mm, no 8mm is being offered…
Maybe we should ask PWB to make a G70/L70, 60 fathom chain (109m) in 8mm?

Bruce Savage

Thanks very much for that info Gerben. I think that Maggi supply an oversized end link as standard on their Aqua 7 chains, I certainly would specify this before ordering. The Aussie g7 transport chains are interesting, tho obviously not galvanised. Apart from that, my concern would be whether the links are calibrated (consistent size) for the anchor winch. I haven’t priced them properly but based on comments from some of the chain sales people I’ve spoken with it sounds like they may be more expensive than Maggi. I think that getting this chain Armorgalv treated would be a very interesting option. The Armorgalv process is at lower temperatures than hot dip galv, so the HT properties are not compromised. Also hydrogen embrittlement cannot happen.
As a matter of fact I have now decided to get a bit more life out of my old chain and, being in Newcastle at the moment where Armorgalv is located, I have sent it in to get Armorgalved. It will be very interesting to see the result, I had a bit of a tour of what they do and it looks really good.
As far as the new chain goes I have bought myself some time and hopefully will be able to buy some in the future when we cruise by NZ, which will save a huge shipping bill.

Bruce Savage

Oh also, the Armorgalv is costing AU$500, whereas regalvinizing would have cost about 700.
Changing topic, the thought of 260kg of chain in my bow has made me wonder about the pros and cons of moving the chain back temporarily for a long ocean crossing. I’m considering dragging the chain back and down below to the Centerboard area. A strenuous task, but doable. Then at the end of the voyage before arrival, drag it all back into the locker. We are heading up to New Caledonia and there is always a good chance of a fair bit of 60 degree tight reaching in strongish trade winds. I would leave the anchor on the bow with a rope rode in case of emergency.

Dick Stevenson

Bruce, Please note that there was a recent review of Armorgalv in Practical Sailor in recent months. I do not remember the results as I was not in the market. Also, for many hulls, PVC conduit/pipe down the crotch of the hull allows the chain to go back and forth to go back and forth from the bow without disrupting the storage. We store one half our chain amidships most of the season (rarely need it all) and pul three quarters back off shore (all that fits).
Dick Stevenson, s/ v Alchemy

Bruce Savage

Thanks Dick, I did read that Practical Sailor article which was very interesting. The conclusion of the article was that hot dip galv is better, but I am not convinced. For my situation where I am wanting a new lighter chain probably within the next year or so it was the cheaper alternative to fix a badly rusted chain and I am keen to see how it performs.
I like that idea of the PVC pipe but I have a watertight bulkhead behind the anchor locker which would be a problem.

Manuel Jose Berrocal

Can anyone tell me if you have had any experience with the new TITANIUM WICHARD BOW SHACKLES. They are expensive, but I am considering using them on a G-43 chain of 3/8″ or 7/16″, in order to avoid using a larger size PEERLESS SHACKLE with enlarged end link in the chain. I have not been able to find any retailer that would be willing to do the enlarged end links. The boat is a SPORTFISHER of 30,000 pounds.

Eric Klem

Hi Manuel,

There is a lot of confusion out there on sizing shackles relative to chain. I believe that a large portion of this confusion comes from people not comparing similar numbers. For example, the working load limit of G43 chain is typically quoted as 1/3 the breaking strength while the working load limit on a Crosby 209A is 1/4.5 compared to the breaking strength. Since you can typically fit a shackle one size larger than the chain, 3/8 G43 chain (16,200 lb breaking strength) can be coupled with a 7/16 209A (24,000 lb breaking strength). I don’t mind having the extra margin because the shackle is much more likely to get a weird side load than the rest of the chain. For this system, I would say it is appropriate for use with a boat that might exert loads of 5400 lbs (3X safety factor).

Where it gets really confusing is when people start talking about other manufacturers for shackles or shackles rated for other applications such as overhead lifting. In what I have seen from Wichard, they use a 3X safety factor for their stainless and titanium shackles. When comparing working load limits, this makes them look similar in strength to the 209A but in truth, they are significantly weaker because they have a lower breaking strength and there is no good reason why they should require a lower safety factor. Another way to put it is that you should be comparing breaking strengths and not working load limits. Titanium is a very cool although expensive material but I believe that the correct thing to use here is a good high strength galvanized shackle.

Eric

Dick Stevenson

Hey everyone,
I am looking for new chain and I am overseas. My gypsy is for Acco 5/16 G4 and I am looking at Maggi 8mm G4 (what they call Aqua 4).
To test the chain in the gypsy I plan to buy a 2m section, put it in the gypsy and secure with small stretchy nylon or big bungy and haul away seeing how well the gypsy holds and how the fit seems.
Any reactions to this plan or other suggestions?
Thanks for your thoughts, Dick Stevenson, s/v Alchemy

Manuel Jose Berrocal

Thank you John and Erick very much for your help. Sounds good to me. I am off to buy my chain and high strength galvanized shackle.

Manuel Jose Berrocal

Thank you Dick. That what I figured I should do. Thanks for the reassurance. I know the anchor’s bend. However, I did not know about the sew. I can do the SCAFFOLD with a double pass over the shackle, it will end up like the anchor’s bend, but without the need to sew. I have learned a lot in this site. I truly appreciate the input, from all. Best, MJ

Manuel Jose Berrocal

Thank you John. Validating my plan in this site represents a higher degree of confidence. Thank you for your comments.

Manuel Jose Berrocal

There must be an error in the web page system. I am able to read the post that ERIC KLEM sent to my e-mail, but I am not able to see it here. All comments to this article are in hiding now. I can only see the last three (3).

Manuel Jose Berrocal

Eric, thank you for taking the time to write such an interesting post on my behalf. It makes all the sense in the world. I am able to make an informed decision about my rode now. Much appreciated.

Drew Frye

You may have made a mistake in assuming that safety factor was related to use, risk, or marketing, and that the 3:1 for G43/G70 was somehow not as good as 4:1 for BBB.

The reason is that safety factors are NOT based upon breaking strength, they are based on yield strength (the point where bending becomes permanent). Because high strength steels are springier (can work closer to breaking without bending) they also endure far more cycling without fatigue (car springs, for example–try making those from low strength steel). Anchor chains fail from fatigue, never actual breaking strength.

The lower safety factors (relative to BS–they are the same based on YS) are based upon good science and engineering experience. Too bad they don’t report them as based on yield strength. For the rest of us, we should simply accept the WL value and go with it.

(I spent my entire career designing and inspecting refinery equipment, tanks, and pressure vessels. The above is based upon those codes, not opinion.)

Eric Klem

Hi Drew,

Very interesting information, I had never given it that much detailed thought but it makes perfect sense. As you surely know, the debate over how to apply a safety factor can be quite interesting as sometimes it is appropriate to work to a yield strength, a breaking strength or a fatigue limit and it depends on the application.

For other readers, as an example of what you are talking about, 4140 is a material which has many different heat treatments that yield different properties. Two different treatments of the same material result in values of 60ksi YS/95ksi TS for an annealed version and 140ksi YS/165ksi TS for one with more extensive heat treating. The low strength version has a yield strength that is only 63% of the tensile strength and the high strength version is 85%. There are materials that can be much more extreme. One example that sailors use all the time is 304 stainless which is 31ksi YS/73ksi TS.

Eric