8mm Galvanised Calibrated Grade 40 Chain

CaptainBob

CaptainBob

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After my thread last year where I was trying to work out if it was best to go for Italian Grade 70 chain or some other Grade 40 I concluded the Grade 40 on sale by Bradney was the way to go.

Price quoted was excellent.

I phoned just now to take the plunge and finally order 60m of it and it turns out that Bradney has been sold and the new owners no longer sell Grade 40. Only grade 30.

They advised that Grade 30 would be fine because the breaking load is 3 tonnes whereas the Grade 40 they were offering had a MSL of only 1.5 tonnes.

These two figures should not really be compared directly I suspect. Grade 40's breaking load presumably would be above 3 tonnes if Grade 30 is 3?

Will I be fine with their Grade 30?

Or should I go elsewhere and get some Grade 40? Any suggestions?

Please note that my boat is a ketch of 13 tonnes and 38 foot and broad beam. It would normally be advised to have 10mm+ on a boat this size, so I was trying to get the best 8mm I could, without breaking the bank.
 
CaptainBob said:
They advised that Grade 30 would be fine because the breaking load is 3 tonnes whereas the Grade 40 they were offering had a MSL of only 1.5 tonnes.

These two figures should not really be compared directly I suspect. Grade 40's breaking load presumably would be above 3 tonnes if Grade 30 is 3?
Click to expand...

Correct. I don't know what MSL stands for, but I'm assuming it's effectively a working load figure. Comparing it against break load is nonsense and reflects badly on them.

From memory, most of the chain and fittings I looked at last year used a safety ratio of 4:1, except for the shackle which was rated for lifting at 6:1.

Pete
 
CaptainBob said:
They advised that Grade 30 would be fine because the breaking load is 3 tonnes whereas the Grade 40 they were offering had a MSL of only 1.5 tonnes.

These two figures should not really be compared directly I suspect. Grade 40's breaking load presumably would be above 3 tonnes if Grade 30 is 3?

MSL is presumably Maximum Safe Load so definitely not the same a breaking load. I would expect (not an expert) a factor of 3 or 4 between the two making the Grade 40 +50% or +100% stronger than the Grade 30.
Click to expand...
 
I have figures for 8mm G30 of WLL 800kg, breaking force 3,200kg. For G40 I have WLL of 1,000kg, but I have no figure for breaking force. I would expect it to be 4,000kg, retaining the same safety factor.
 
You can see all the data at http://coxengineering.sharepoint.com/Pages/Chaindefinitions.aspx

The 1.5 tonne SWL figure for Grade 40 seems high. In 8 mm chain the grade is the same as the UTS in kN, i.e. Grade 30 fails at 30 kN (3 tonnes) and grade 40 at 40 kN (4 tonnes). Chain normally has a safety factor of 4:1. When I suggested buying Grade 40 a day or two ago it was because your boat is somewhat on the borderline for 8 mm and grade 30 might be a little light. The suggestion of going to Bradney, amongst others, was because their grade 30 was well into grade 40 when I tested it. I would buy elsewhere, Jimmy Green for Maggi chain known to be grade 40, William Hackett for Chinese chain nominally grade 30 but actually much better.
 
Salty John said:
8mm, G30 is adequate for your boat size.
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Correct , and not just because of the breaking strain, but because of the weight. Part of the reason for using chain is because of the catenary action of the chain which acts as a damper.
A 13 ton wide beamy 38 footer needs at least 11mm chain.
 
Eyore said:
Correct , and not just because of the breaking strain, but because of the weight. Part of the reason for using chain is because of the catenary action of the chain which acts as a damper.
A 13 ton wide beamy 38 footer needs at least 11mm chain.
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He said it _was_ adequate didn't he?

Anyway, unfortunately, the catenary thing has been disproved repeatedly. As soon as conditions are such that there might be a problem, the chain is as near straight as makes no odds that in fact you might as well be using all rope if it weren't for the chafe.



I've gone ahead and ordered 50m of 8mm Grade 40 DIN 766 from Jimmy Green. Couldn't bring myself to stretch to 60m. This 50m cost, with delivery, over £100 more than it would have done for 60m of the same grade at Bradney - but they don't sell it any more.

I've bought 20m of 14mm rope also to splice on the end giving us 70m total. More than we've ever needed in 5 years of anchoring around the UK much of the time.

(Incidentally we have a Rocna and have had a Rocna for 4 years now (25kg on this boat, 15kg on previous). We've anchored hundreds of times on every different bottom you can think of in the UK. We've anchored in winds up to sustained 55 knots. We often anchor with less than a 3:1 scope out due to tight swinging room. We once (in a full gale) dragged 10m and then stopped. On retrieving the anchor it had a MASSIVE ball of weed in it. Other than that we haven't moved a mm.)
 
CaptainBob said:
Anyway, unfortunately, the catenary thing has been disproved repeatedly. As soon as conditions are such that there might be a problem, the chain is as near straight as makes no odds that in fact you might as well be using all rope if it weren't for the chafe.
Click to expand...

News to me ,then again again after 40 years sailing call me old fashioned but I wasn't aware that seamanship had changed. However its your boat , so its your decision needless to say but it really pisses me off when boats drag in an anchorage due to inadequate anchoring gear.
 
True enough , but its horses for courses.There is a big difference between a 38ft Colin Archer and a 38ft Bavaria as to what anchor gear they should have.
 
When Hylas (RIP) was posting here he was a strong advocate for rope rodes. His boat was a heavyweight 48 ft world-girdler (surprise - a Hylas) which he was then cruising in the Magellan Strait and further south. He used a Spade, either steel or aluminium, with a short length of chain for wear resistance and the remainder rope. He worked closely with Alain Fraysse, author of the excellent mathematical studies that have revised our knowledge of anchoring.
 
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