The Offshore Voyaging Reference Site

Q&A: Breaking Load Of Anchor Chain

Our latest thinking on chain starts with this chapter.

Question: Do you have views on breaking load of main anchor chain compared to weight of boat? Our new boat is 40’ long and weighs something like 12 metric tons (26,000lbs) and a ‘standard’ 10mm (about 3/8”) galvanized chain has a breaking load of approximately 6 tons.

Answer: Some thoughts that may help you choose chain:

  1. There is a lot of very poor chain around, made in the Far East, that should be avoided. In the USA and Canada we always recommend that people buy chain from Acco only. I’m not sure if this chain is available in Europe but I’m sure that there must be a good chain made in Europe. The key thing is that the manufacturer should have proofed (tested) every link and be willing to put that in writing.
  2. For a boat your size we would normally suggest 3/8″ (just a tad smaller than 10mm) chain if BBB type with a safe working load of 2650lbs (1202kg).
  3. We prefer to talk about safe working load (SWL), not breaking load, since chain repeatedly subjected to loads above its SWL will, in time, weaken and become unsafe. Generally, SWL is about 1/4 of breaking strength.
  4. Although BBB chain used to be the standard for anchoring, on Morgan’s Cloud we use, and are increasingly recommending, Acco G40 high tensile chain that is over twice as strong as BBB. For example, G40 3/8″ has a SWL of 5400lbs (2449kg).
  5. The challenge with using high tensile chain is that you must find high tensile shackles to get a strong enough shackle to match the chain. We use G209A from Crosby.
  6. There is an even stronger chain called G70, but here, to get the same strength in the shackles, you must order it with special oversized links at each end.
  7. On your boat, by using the right high tensile chain, I think you could go down one size to 5/16″ (8mm) and save a lot of weight that could then be put into a bigger anchor.
  8. Many people will tell you that you need much heavier chain than the sizes we are talking about here, but we feel that is not correct and that weight is better put into a larger anchor or more chain length. For example, Steve Dashew tells me that one of his Sundeer 64 boats went through the big hurricane in Grenada anchored on 3/8″ Acco G70 chain with winds of well over 100 knots and big seas.
  9. Also, although it is purely anecdotal information, I have never heard of a yacht’s chain rode breaking though we have all heard of boats being lost due to a dragging anchor. Keeping that in mind, I know where I want to put the weight.
  10. I do think it is important that a nylon snubber is used in extreme anchoring situations to relieve the chain and gear of shock loads.
  11. I think that the idea that the catenary caused by heavy chain has benefit is wrong since on Morgan’s Cloud in winds of gale force, even with all 100 meters of our 7/16″ (about 11mm) chain out, it pulls out straight. So at the very time you need it most, there is no catenary.
  12. When we next buy chain we might go down to 3/8″ G70 chain to save weight and carry an extra 30 meters. Our thinking is that once you have a good type of heavy anchor (we like SPADE), having plenty of rode length is the next biggest contributor to anchoring security. It also lets you get away from the bumper-cars games in some crowded anchorages, by allowing you to anchor in deeper water than most other boats can.
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I can agree with most of what you say concerning make and type of chain and need for a nylon snubber etc. Where I differ is in that catenary in my view is a very important factor in preventing snubbing, and thus taking any shock loading off the anchor, provided you are in deep enough water to allow the chain to take up its natural curve due to its weight and length. In shallow water it has been shown that when subjected to strong winds and heavy seas no matter how much chain you have out it will straighten out and pull the anchor upwards and out of the bottom. Years ago when I started sailing we used to use an ´Angel`. Simply, this is a weight that is slid down the chain on a retrieving line and hangs underneath the chain. This increases the catenary and acts as a shock absorber. The Angel was a product made by Potters of London, it had a number of heavy galvanised weights that could be added as necessary. However, any weight on a suitable hook-like sliding device can be used to good affect. I used an old cast iron heavy disc from a very old marine petrol paraffin engine for a long time slung from a large bow shackle.

Francois DULIEGE

I believe a good solution to the connection between chain and anchor is the Stainless Steel “Maillon Rapide Quick Link”.
The 3/8″ model (9 mm chain) has a working load of 1.4 t and a breaking load of 7 t (5x safety factor !!!).
The 7/16″ (10 mm) has a WLL of 1.8 t and a BL of 9 t.
I have no commercial involvement in any way with Peguet, but I have used their products since many years and they are very reliable (and expensive…).
Thank you for a very useful site.

Colin Speedie

Hi Francois

Thanks for the suggestion and the link – I’ve never seen anyone use these screw type carabineers for such an application, but that doesn’t mean that they don’t work!

I don’t doubt that they may well be strong enough, but I’ve a couple of queries – do you find that they ‘articulate’ well enough at the anchor end, as they are rather long and narrow – I use a bow shackle to make sure there is no resistance at the anchor to ensure that there is no resistance to the chain moving as the boat swings. And how do you secure the threaded ring. Do you use a locking compound such as Loctite, for example?

Kind regards


Francois DULIEGE

Hi Colin,
The advice to use Peguet Maillon Rapide (and no other brand !), comes from Alain Poiraud, who invented the Spade anchor, and who wrote the best book I ever read on mooring techniques.
Sadly, Alain passed away one year ago, and I don’t believe there is an English version of his excellent book. Among other topics, he covers the absolute need to have an elastic mooring line, and highly recommends a mix chain/rope line.
We have a 43 feet west system boat (10 t), and use a 20 kg Spade, 60 meters of chain n° 10 (7/16″), and 60 meters of squareline. So far, I believe the Peguet link is creating a very “mobile” link between the chain and the Spade, allowing for change in wind direction without the link being stressed in a wrong angle.
I use loctite to secure the link, and I trust it is safe as the threaded part is fairly long, and the quality of the machining is such that there is no play.
In fact, when I turned my chain upside down after 5 years (2 years ago), it took me a great deal of effort to unscrew the link.
Sail safe,

Colin Speedie

Hi Francois

Many thanks for that.

I knew of Alain Poiraud, and as the designer of the Spade I’d be very inclined to listen to anything he said – and he was a combative and amusing contributor to many web forums, whose thoughts were always well worth considering, and I’ll certainly try to pick up a copy of his book when I’m next in France.

I’d certainly agree with the need to mix chain and warp. We carry a little more chain (75m), with 30m of 20mm anchorplait spliced into it, and even when we are lying to chain alone, we have long nylon snubbers, which take all of the shock loading off the anchor – one of Alain’s main points, as I remember.

I’ll have another look at the Peguet site – and if the price isn’t too terrifying maybe give the Maillon Rapide a try – it sounds like an interesting option.

Best wishes



Hi John,

What do you think about using G70 chain on a 48ft sailboat with a displacement of 45,000 lbs? We are a cutter rig with two furling headsails and moderate freeboard. Conventional wisdom would have us using 3/8 G40 which has a SWL of about 1000 lbs more than the 5/16 G70, but at .5 lbs more per foot. We plan or carrying 300 feet of chain so the weight difference would be significant. The chain rode would be attached to a 110 lb Bruce.





Thanks for the advice. We have not bought the anchor yet and based on some recent reading we will go with the Manson Supreme. I liked the Rocna but it looks like they may have had some quality control issues recently. West Marine’s website has some pictures from readers who have had the shanks twist under load.

Regarding the chain size. We will follow your advice on the size. The thought of less weight in the bow was rather enticing though….. But keeping your house off a reef is much better in reality. And to be honest the bow should be able to take the weight. If not we can remove some equipment from the forward berth.

Also, it looks like you are big on customer service. That said, I posted a comment under your section for the windlass on “Morgans Cloud”. We have recently removed the 80’s era Ideal Windlass on our vessel and have had to contact Ideal several times via email and phone and they have been great. Our windlass should be heading up to their shop in Rhode Island for re manufacture next so we will have to let you know how they do. If your interested.




You say:
“There is a lot of very poor chain around, made in the Far East, that should be avoided. In the USA and Canada we always recommend that people buy chain from Acco only. I’m not sure if this chain is available in Europe but I’m sure that there must be a good chain made in Europe. ”

We´re about to exhange our 60m/ 180 feet stainless 13mm anchor chain, and have found that there are no European producer of steel chain anymore. According to numerous chain retailers (Norwegian) we have spoken to, all retailers are getting their chain from China. They all have only good words to say about the quality of the chain coming from China, as long as speaking of sertified grade chain, like G40 or G70. They all says it´s good to go, and have, at least, the same quality as European produced steel chain used to have.


Maggi Chain (Preston) said ACCO does not do hot galvanizing any more. What have you heard?
also having trouble finding a gypsy that will take grade 70 – 5/16 chain. Our windlass is a
40 foot D. Peterson aluminum sailboat. I want to carry 400 feet of chain.


Hi all, good Peter Smith (Rocna maker), quantitatively supported article echoing John’s opinion on the irrelevance of chain catenary effect:
Apologies if this source is referenced in more recent ‘Anchoring’ material, I just happened to read this post today and see it’s not been mentioned so far…

Steve Zambroski

John….I am planning on world cruising on my Sabre 402 (40ft), I am changing out my windless, anchor and chain. My boat is sensitve bow weight, the original owner had 250ft of BBB 3/8. I am planning on getting a Spade or Rocna 55lbs anchor. I am limited on the size of windless due to space constraints in the anchor locker but the working load is approx 600lbs for the windless. So I am using approx 200lbs for my anchor and chain weight. Do I go with 5/16 Acco G4 or G70 with 150ft plus 250 of 8 plate or do I drop to 1/4 Acco G70 with 200ft plus rode. your thoughts?

Steve Zambroski

John……I talked with a technical person at Peerless (Acco) this morning regarding their G70, G4, BBB products. Without going into all the detail because Acco asked me not to post the safety factors that are not published but I could summarize. The breaking strength times the safety factory (not published) of 5/16 G4 and the 1/4 G70 are almost the same. The safety factor is different for the products. Huge weight savings for me, hence more chain. I hope this helps people that are having concerns about dropping in size. The G70 1/4 fits with in the dimensional window of BBB or G4 for the windless… it should work. Famous last words.