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Old 20-11-2008, 02:06   #1
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Breaking an Anchor Chain

Ok we all know the relative sizes and strengths of anchor chain and what boat size the manufacturers recommend.

....truth or lie time........

I want to know if any body has had a chain snap.

Need to know boat size, and weight, circumstances, and chain size and type.

Dont want conjecture's about cheap this and best that....

I want to know if someone has snapped their chain. SIMPLE.
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Old 20-11-2008, 09:03   #2
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Quote:
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I want to know if any body has had a chain snap.
.
Oh yes, it happens !!

The last one I saw was in the port of Fogo isla in Cap Verde archipelago.

The boat: a steel French boat « Passagers du Vent » 12 meters (about 40 ft) and around 12 tons, the chain size :10 mm
The boat was moored, stern to the quay with the anchor from the bow (full chain line) and a scope of around 3/1.

A big swell was coming in, from time to time coming over the breakwater when the chain broke; the boat went to hit the quay with a severely bent ruder...

Now, you have to think at the forces evolved, the energy formula is ½ M V² or half the weight of the boat x by the square of the speed – If your anchor don’t drag, and without any elasticity of the mooring line (chain) the force will BY FAR exceed the resistance of the chain.

And this is why, with strong wind, you should ALWAYS have some king of « damping » - either a mixed chain/rope rode or a good snubber...

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Old 20-11-2008, 09:12   #3
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Personally

I've personally only ever distorted and stretched the links but I've seen plenty of snapped chains in permanent mooring systems. My boat was hit in a storm a few years ago, to the tune of 25k in damage, due to snapped shackle.


It think with the previous generation of anchors it was difficult for them to hold the bottom enough to exert chain snapping loads, unless the chain was grossly undersized. With the new generation anchors the possibility is greatly exacerbated when many will hold 5000 pounds or more of pull.

My anchor chain is over sized, as is my rode, and I replace the chain every 5-6 years.
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Old 20-11-2008, 10:17   #4
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I don't have the details, but I did see a chain break on a cruising boat. The boat was in the low 40's in length. Two crew. Skipper sends the crew up to the bow to prepare to anchor. He turns the boat way out from the anchorage in deep water, she lets the anchor go, he yells 'Not here', she throws on the chain brake, the chain stops, the anchor and chain tail drop to the bottom.

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Old 20-11-2008, 12:50   #5
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Old 20-11-2008, 16:28   #6
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In fourteen years of world cruising, I never broke a chain, and I never met a person who broke a chain. We used 200 feet of 3/8 inch high test chainand had an anchor bridle with two arms that were twenty feet each.

While anchoring around coral, we have had galvanizing rub off on a coral bottom. We have had a few mighty jerks on our 200 feet of chain, but it never broke.

Our main problem with chain is the fact that it twists, and periodically I have to detach the bitter end to get out the hockles. The second problem is loss of galvanizing over time.
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Old 20-11-2008, 16:57   #7
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I know a Grand Soleil 39 which broke an older (weak?) anchor chain down in Costa Rica in 40 knots of wind. Another cruising boat broke its chain inside the atoll at Rangirioa when the wind shifted, the chain wound around a coral head, then the waves built. Another boat (Baba 40) in the same situation didn't break its chain, but broke its windlass. When that happens to us, we let out more scope and put a long snubber on to absorb the shock load.
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Old 20-11-2008, 18:29   #8
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I wholeheartedly agree with the general trend here - chain will not absorb shock, so you must have something in your anchoring system to act as that shock absorber. I use 3/8 HT chain on a 60 lb CQR as my primary. Boat (CSY 44) has a LOT of windage, and weighs in at about 19 tons when water tanks are full. I ALWAYS use my bridle when I anchor .... and I anchor 99.9% of the time. The bridle is made up of 3/4" 3-strand nylon rope. There is a chain hook in the center. Each "arm" is about 20' long, and is led through a hawse hole in the bulwarks to a large cleat on each side of the bow. Once the anchor is set I put the hook onto chain and let out enough additional chain so that it forms a large loop hanging free below the chain hook. In this way the strain of the chain is taken up by the bridle rather than having the chain attached directly to the boat. I also try to have at least a 7:1 scope. Thus, the first strain is absorbed by the cantinary of the chain, after which it is taken by the bridle. I have had a 50 footer drag down and get stuck on my bow in 35-40 knot winds so that both boats were effectively anchored on my anchor with no problem.
Also, to alleviate the twisting problem I use an oversized swivel between my anchor and the chain.
I have heard of boats breaking chains, but I've never had a problem.
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Old 21-11-2008, 01:23   #9
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thanks for the replys...seems that stretching links may be a problem more common than I thought.............
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Old 21-11-2008, 05:45   #10
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The only way I'd imagine a chain breaking is after long wear or under the stresses listed earlier. Understand thats why we have deserts...cause if my chain breaks I'm moving to the desert, hundreds of miles from water
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Old 21-11-2008, 19:50   #11
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Most of the time when chain breaks it's because not enough scope was used and the chain comes up hard when there's a big swell. Chain absorbs shock very well as long as you use proper scope. It's the weight of the chain and the caternary curve that absorbs the shock from surges. And in extreme weather you can use a weight half way down the chain to help absorb the shock. Never broke a chain or stretched any links and our boat was heavy. 36 feet and 13 + tons loaded for cruising.
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Old 22-11-2008, 05:01   #12
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Quote:
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chain breaks because it's not enough scope….
...It's the weight of the chain and the catenary curve that absorbs the shock from surges....
....And in extreme weather you can use a weight half way down the chain to help absorb the shock....
Sorry Santana if I have to disagree with your comments. They are the typical myths that are always surviving!

1° Scope is limited by the room and the weight you can carry on the bow of your boat. For me a 10/1 is a maximum.

2° I Know, for a purely mathematical point of view, to have the chain absolutely straight, you need an infinite force, but to have it « Nearly » straight, the force is minimal (for those who like formulas, go to the very interesting web page : Tuning an anchor rode : http://alain.fraysse.free.fr/sail/rode/rode.htm )
The shock absorption made by the catenary curve of the chain is minimal.

3° the last myth, the one of the « Angel » « Chum » « Sentinel » « Mobilest ».. If you are using a « manageable » weight, let’s say a maximum of 20 kg (44 lbs) – the shock absorbing action is also minimal.

As stated before, a good elastic snubber is a simple and efficient solution.

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Old 03-12-2008, 08:10   #13
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hockle issue

I have never had or seen a chain snap. I have ten fathoms of 3/8 BBB and 200 feet of 5/8 three strand on my bower. I have not had a hockle problem. Does everyone feel that hockleing is a non-issue with BBB chain as I have been led to believe? I am a coastal New England cruiser and have no necessity for an all chain rode. Not that it wouldn't be nice, it's just not a necessity here.
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Old 25-07-2011, 11:10   #14
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Re: breaking an anchor chain

I have had an anchor chain snap. My double keeled Westerly was anchored in tidal inlet. When tide came in, along with a strong wind, the boat must have floated and shot downwind, snapping the chain.

In similar conditions now, I'd put out a second anchor w/ a nylon rode. Or at least rig a bridle to absorb the shock.

Boat weight about 8,000 pounds. 1/4" proof coil chain. Scope at time chain snapped was more than 10:1 on a CQR anchor.

Boat ended up aground in someone's front yard for a month, till a higher tide came along.
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Old 25-07-2011, 11:20   #15
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Re: Breaking an Anchor Chain

Greetings and welcome aboard the CF, afeldma.

Under those circumstances, and on that boat (26' - 27' LOA?), I don’t think that a 1/4" PC chain (rated 1,300# WLL), in good condition, should have broken.
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