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Old 22-06-2012, 07:44   #61
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chain broke! Twice!

What a lot of information to absorb.

Ok. in the last two days my anchor chain broke twice, so I need some suggestions!

We are in a Leopard 42 Catamaran with 10mm / 3/8 inch BBB (I think) chain. Not totally sure as the pitch length is just short of 1 1/8 inches which according to my Bible (Nigel Calder) puts it half way between the BBB and High Test sizes. It is three years old, and was bought by the charter company in BVI when the boat was still in charter, so I am guessing it is the cheaper BBB.

Here is what happened:

The first time our anchor got caught under a rock, the chain was bent around the bow roller side posts. I guess the boat lurched and jerked at it. The link was bent, and parted cleanly at the weld.

We went and found a better place to anchor and put out our Fortress with nylon rode, while we went into town (Calvi, Corsica) to see what we could do. We came back with a stainless steel hammer-it-together C-link from uship.fr. No idea on breaking strengths etc. At the same time we decided to end-for-end our chain.

We then decided to replace our nicely holding Fortress with our regular anchor. In a force 7, of course, just to add to the fun. But NOT a lot of waves.

So we pull up the fortress and put down the regular. We let out a bunch of chain (I think about 40m in 5m below the keel = about 7m to deck height.). But the anchor didn't seem to snag, so we let out a bunch more chain. Still we were rapidly drifting off downwind.

Eventually we realised something was amis. Yep, we are a bit slow! So we pulled it all in again only to find ... no anchor!

Well, back to the trusty fortress.

Today the wind had dropped so we did a GPS grid search with the dinghy and found the anchor (thanks to clear water!). We brought up the anchor to find it still attached to 20m or chain. Remember this is the end-for-end, ie the bit of chain that has never been used before, it has just sat at the bottom of the locker and looks in excellent non-rusty condition.

So, clearly a second link had parted. But no sign of the actual broken link.

This is very concerning. Previously we have had no problems with the chain. And this section of chain has certainly never been under any strain before.

The first break I can understand, but still am concerned that it gave way at the weld in such a clean manner.

The second break? What do we make of that?

So, where do I go from here? Does this mean the whole chain is suspect and we should replace the lot?

If so, do I go with BBB or the same size of HT, given that the links work nicely in our horizontal windlass?

Appreciate all your sage advice.

Noel
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Old 22-06-2012, 07:58   #62
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Re: BBB vs High-Test Chain

i use high TENSILE chain. bbb doesnt have the breaking strength that ht does. if your boat is not heavy and you are not going to be in high wind and big sea anchorages, bbb will be fine. has been touted for decades....but i will continue to use high tensile chain form my heavy boat.
where the chain is manufactured alsohas a lot to do with strength and breaking at the welds--chinese chain isnt welded nor galvanized well and WILL break.
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Old 22-06-2012, 08:12   #63
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Re: BBB vs High-Test Chain

Hi Noel,

Your chain is not trustworthy. There is nothing you can do to make it safe. I'm sure you know this and just want time to process it. Replace that chain with something that you trust and never look back.

Regarding BBB vs HT vs G70 (I use G70 BTW) I've found that if I use 3/8" BBB on my 8' dinghy it never has any problem but 1/4" G70 on my aircraft carrier breaks at the least puff of wind.

That little bit of humor is just to point out that you need to match the chain to the application.

If your expected load peaks do not exceed the WLL of 3/8 BBB, use it. If they do exceed the WLL then go to 3/8 HT. If you like to have a larger margin of expected peaks to WLL go G70. Also, with G70 you may be able to drop a chain size.

In any case match the chain pitch to the wildcat on your windless.

But back to the key message - Your chain is crap. Replace it now.

Regards, E
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Old 22-06-2012, 08:26   #64
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Re: BBB vs High-Test Chain

The BBB should not be breaking from a simple jerking motion. I heard this happening one time in the early 90s and it turned out to be fairly new Chinese chain which parted like your at the weld...commonly known as a cold weld.
Scrap that chain (don't sell it to someone else) and take a piece of it to a reputable marine chain supplier. BBB has the advantage over high test for lying down on the sea bed better, due to it's weight, aiding with the anchor digging in.
ACCO (American Made) has a breaking strength of 11,000 lbs and a safe working load of 2700 lbs.
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Old 22-06-2012, 13:07   #65
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Re: BBB vs High-Test Chain

Yeah, I figured you would all say that. As you said, I just needed some time to process it all.

So, I need to bite the bullet and hunt down some decent chain.

I'm still not clear, however, as to how I estimate the loads that I might put on the anchor chain. To be realistic, I guess I need to plan for at least a force 10. Is there a calculator out there that can estimate the loads for a catamaran? Lots for a monohull, it seems.
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Old 22-06-2012, 13:35   #66
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Re: BBB vs High-Test Chain

Personally, I would steer well away from high test chain. I want weight in the catenary to take out shock loading. Look at it from an extreme to get the point. An anchor rode made out of some space-age-light-as-a-feather but stronger than steel material, say Spectrasuper. I would NEVER use that on my anchor, if the boat snatched in a gust, we would pluck the anchor out of the bottom. We love our heavy chain. It has saved us over and over again. In G-town in 2001 460 boats at anchor. So many people came up to us to ask why we never hunted around on anchor. The answer is heavy chain. We are approaching 5000 nights at anchor. We like our sleep. We like our heavy chain, with NO swivel and NO snubber. Our boat is 66000 pounds.
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Old 22-06-2012, 13:52   #67
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Re: BBB vs High-Test Chain

Good chance what you have is 10 mm. That is what came on our voyage 430, and which I later changed to 5/16 G40.


E, is it hard to find galvanized G70 , and gypsey to match?
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Old 22-06-2012, 14:07   #68
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Re: BBB vs High-Test Chain

Quote:
Originally Posted by ggray View Post
Good chance what you have is 10 mm. That is what came on our voyage 430, and which I later changed to 5/16 G40.


E, is it hard to find galvanized G70 , and gypsey to match?

West Marine sells Galvanized 5/16" G70 form Acco. WM will cut you a 1.5' sample to test out on your windless.

-E
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Old 22-06-2012, 15:21   #69
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Re: BBB vs High-Test Chain

Hey Noel...If it were me, I'd take a poll on the Cat threads as to what others are using. I have a Mono which is in the 14,ooo lbs range. I have 3/8 BBB which is some what over-rated. 5/16 proof would have been fine.
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Old 22-06-2012, 15:37   #70
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Re: BBB vs High-Test Chain

Quote:
Originally Posted by ggray View Post
Good chance what you have is 10 mm. That is what came on our voyage 430, and which I later changed to 5/16 G40.


E, is it hard to find galvanized G70 , and gypsey to match?
Call Washington Chain Supply in Seattle. They can custom order you G70, and they ship all over the US. Their prices are substantially lower that WM (even on Port Supply).

I replaced the gypsy and the new 5/16 G70 feeds just fine on the Maxwell 5/16 HT wheel.
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Old 22-06-2012, 16:05   #71
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Re: BBB vs High-Test Chain

Thanks!
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Old 22-06-2012, 16:52   #72
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Re: BBB vs High-Test Chain

Quote:
Originally Posted by LifePart2 View Post
Yeah, I figured you would all say that. As you said, I just needed some time to process it all.

So, I need to bite the bullet and hunt down some decent chain.

I'm still not clear, however, as to how I estimate the loads that I might put on the anchor chain. To be realistic, I guess I need to plan for at least a force 10. Is there a calculator out there that can estimate the loads for a catamaran? Lots for a monohull, it seems.
Unfortunately, knowing the loads is near impossible due to differing boats, wave heights, etc. As a starting point, the ABYC provides some loading numbers to work from. Personally, I use the "mooring" numbers for anchor chain meaning that you would need an anchor chain with a working load limit (not breaking strength) of on the order of 4000lbs which means that you would definitely want G40. Chances are you will never get even close to that number but chances are also really good that you will far exceed it if you end up anchored in a surf line in a bad storm. Here is a link to the table:
Design Loads for Deck Hardware - ABYC Section H-40, table 1 Cruisers & Sailing Photo Gallery

Provided that you stay with 3/8" chain, the weight per unit length is basically the same for BBB and G40 meaning that the catenary effect that you get will be the same. In extreme conditions, there won't be any catenary with either one and you will be relying on an shock absorbers that you might have and your anchor.
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Old 22-06-2012, 18:22   #73
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Re: BBB vs High-Test Chain

I personally think chain specifications do not mean that much! OK--- sure, not many would recommend using 1/4 BBB. But my point is how many chocks, cleats, fiberglass hulls are anywhere near as strong as most chains???

My chocks are good quality SS secured to the bow with two each 1/4-20 SS bolts each. I had to back them up because the Silverton did not! They relied on the fiberglass. I can just visualize the thing being ripped out under a modest load.

All should remember that a chain is no stronger than the weakest link and that link could well be your boat. I expect to read replies where chocks and cleats on somebody's boat are secured using 3/4" SS bolts b with 1" SS backing plates under the chocks/cleats with a reinforced bow structure. It just aint so folks. JMHO

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Old 22-06-2012, 19:04   #74
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Re: BBB vs High-Test Chain

I agree totally and weight added to a boat should be considered also. It pays to thoroughly go threw your entire ground tackle system and beef it up to a reasonable degree. Even backing plates will pull out of F/G, given the right load.
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Old 22-06-2012, 21:05   #75
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Re: BBB vs High-Test Chain

I don't understand the North American preference for high tensile chain for anchor cables. It seems to me like EXACTLY the wrong material for this particular job.

The prices paid for tensile strength in steel alloys are:

1) Lower ductility than lower tensile 'mild' steels, and consequently lower Impact strength.
The low ductility means that an impact load causes irreversible 'strain hardening', which increases the tensile strength even further, but at further expense to ductility.
Impact strength decreases severely with increasing tensile strength, and even the tiniest crack, anywhere along the chain, amplifies this disadvantage considerably.
High tensile chains, used for lifting, are recognised as very delicate, and must be condemned if they come under a shock load, even only once. They are not used for towing, snigging, demolition or any of the more robust roles for chain .

2) Reduced Corrosion resistance
I'm not thinking about visible corrosion, but about susceptibility to 'stress corrosion cracking', which is on a smaller scale, and much more serious.
It happens when you repeatedly load a corrodible metal in a corrosive environment.
Crack susceptibility is greatly exaggerated because the material at the pointy apex of the crack, every time load comes on, is 'mined' and carried swiftly away by - in this instance- the chlorides in seawater. The crack being established interacts horribly with the lack of ductility mentioned above.

3) More variability in properties, and more susceptibility in terms of breaking strength and impact strength to (say) suboptimal galvanising.
High tensile steel is also much more prone to problems where it is welded.
Mild steel is considerably more forgiving of 'average' welding and galvanising procedures, and of general wear and tear.


Reducing the size of the chain makes these problems more serious: firstly because of the obvious direct effects (less inherent resistance to a given load) and secondly because the impact loads are greatly increased by going to a smaller, lighter, less 'saggy' chain, as Gilana's owner points out

To me, choosing high-test chain is like choosing a racehorse because of the phenomenal power to weight ratio, when what you actually need is a draft-horse.
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