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Old 07-10-2019, 12:56   #1
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G70 chain vs G4

I am considering replacing 3/8 G4 chain with 5/16 G70 chain as the working load is similar enough.. (4700 vs 5400), but the weight reduction is ~30%

I cannot find any information on the link design so can anyone comment on practical experience as to whether the G70 links will run over a gypsy designed for G4/HT chain?..

thx
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Old 07-10-2019, 13:19   #2
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Re: G70 chain vs G4

This excellent website documents the differences in size for both metric and imperial chain:

Chain – Cox Engineering

It is unlikely that the same gyspy will work with the change you propose. However, while most gypsies only tolerate a reasonably specific chain size, some are much more versatile.

If you can obtain a short sample of the chain it is reasonably obvious if it will work.
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Old 07-10-2019, 13:23   #3
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Re: G70 chain vs G4

It's not a function of the chain material, but of the link dimensions. 5/16 chain has a shorter link length than 3/8 and won't ride properly in a gypsy designed for 3/8.

It's more complicated than that, because even with ISO/DIN/EN standards there are many different chain pitches even in the same nominal size, so you have to know what the gypsy is designed for (short link, ISO, ...).

And lastly you do get a little variance based on materials. ACCO, for instance, has the same dimensions in G43 and G70 3/8 chain, but they use different dimensions between G43 and G70 in 5/16 chain.

Bottom line, in switching from 3/8 to 5/16 chain you will likely also be swapping out the gypsy on your windlass (but check with the windlass manufacturer first).
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Old 07-10-2019, 14:41   #4
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Re: G70 chain vs G4

As a clarification, i understand i would need to swap the gypsy from the current 3/8 for this project..

unfortunately the Lofrans Tigres does not spec a gypsy for a 5/16 G70, simply a 5/16 HT/G4 version.. so i am not able to test fit without investing in a gypsy..

thx
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Old 07-10-2019, 14:46   #5
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Re: G70 chain vs G4

Then it will all come down to what chain is available to you. Maggi, for instance, publishes identical dimensions for the G4 and G7 chains, so they can swap quite easily. Acco publishes slightly different values for G4 vs G7 in 5/16. They'd probably both work, but a bit more of a guess.

I'd find out exactly what chain you want to buy and then order the gypsy to match, Lofrans offers an awful lot of options to match most chains, you just need to know if the chain is ISO dimensions, or BBB, or...
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Old 08-10-2019, 17:20   #6
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Re: G70 chain vs G4

Just went down this road in the other direction. G4 and G7 links are different length. You will need a gypsy specifically for ACCO G70 chain, Maggi is close but get a foot or two and see if it fits or not. While the numbers of weight versus strength look great the folks who make my windlass don't like to use G70 as it's more brittle and does not tolerate heavy cyclic loads, It's designed for holding down static loads like a truck of felled trees going to the mill. It doesn't like being violently, repeatedly tugged or yanked on like anchors in heavy winds/seas. It snaps without deforming. The G4 will deform/elongate gradually the G7 will not. Then there's the strength of the G7 will be cut in about half if not properly re-galvanized which apparently few people do.
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Old 08-10-2019, 17:36   #7
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Re: G70 chain vs G4

I swapped from 5/16 g4 to 5/16 g70 acco chain with a Lewmar gypsy. The gypsy worked the same on both, not great, not bad.
I eventually ditched the g70 chain and went to 3/8(10mm). The galvanizing on the G70 didn't wear well. The regalvanizing shop refused to work on g70 chain.

I ended up with a new Maxwel windless, and new Maggi 10mm g40 chain. So far the Maggi galvanizing has been superior to the Acco.
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Old 08-10-2019, 22:44   #8
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Re: G70 chain vs G4

Quote:
Originally Posted by Paul L View Post
I swapped from 5/16 g4 to 5/16 g70 acco chain with a Lewmar gypsy. The gypsy worked the same on both, not great, not bad.
I eventually ditched the g70 chain and went to 3/8(10mm). The galvanizing on the G70 didn't wear well.
The short life of the galvanising on G70 chain is the biggest drawback. It is particularly an issue for people full time cruising and anchoring most days of year. When used in this way the required replacement/re-galvanising schedule is really too frequent to be practical.
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Old 09-10-2019, 01:08   #9
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Re: G70 chain vs G4

I've said it before... chain breakage is a very uncommon event with chain in decent condition. My opinion is that folks worry too much about chain strength... do remember that SWL isn't breaking strength. In the very unlikely event of winds strong enough to generate breaking loads on the chain, it is highly likely that the anchor will have upset long before the chain fails. Of course one does not wish to routinely exceed SWL, but as a one time event, the world won't end if you get somewhere between SWL and breaking loads.

In thirty plus years of full time cruising, I've seen two broken chains. One was so rusty that a Mexican fisherman had condemned it... and a very low bucks French Canadien yottie bought it from him. It failed under very mild conditions. The other was 12 mm chain used during a cyclone by a ferrocement square rigger of enormous displacement. Huge (ex landing craft) Danforth anchor, 100 ft chain, no snubber... BANG!

There are IMO better things to worry about!

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And dealing with the corrosion issues with G70 is a non-starter for me
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Old 09-10-2019, 01:55   #10
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Re: G70 chain vs G4

Quote:
Originally Posted by Mystic38 View Post
I am considering replacing 3/8 G4 chain with 5/16 G70 chain as the working load is similar enough.. (4700 vs 5400), but the weight reduction is ~30%

I cannot find any information on the link design so can anyone comment on practical experience as to whether the G70 links will run over a gypsy designed for G4/HT chain?..

thx
The less weight result will be less holding power, all good though if you are a marina jockey and don't anchor often.
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Old 09-10-2019, 02:08   #11
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Re: G70 chain vs G4

FWIW:
NACM: Welded Steel Chain Specifications
https://ia800503.us.archive.org/3/it...chain.2003.pdf
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Old 09-10-2019, 05:00   #12
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Re: G70 chain vs G4

Quote:
Originally Posted by Scubaseas View Post
... folks who make my windlass don't like to use G70 as it's more brittle and does not tolerate heavy cyclic loads, It's designed for holding down static loads like a truck of felled trees going to the mill. It doesn't like being violently, repeatedly tugged or yanked on like anchors in heavy winds/seas. It snaps without deforming....

The windlass manufacture worries me. They should know better. More likely, they just don't make the correct gypsy. Another concern is that the structure of the windlass was based on G30 chain and is just not up to the load. G70 is relatively new in the marine market, and you won't find a windlass that was designed from the ground up for it. I can see why they would shy away. (Yes, I understand that the windlass "should" only be lifting the chain and anchor, but we all know, and the manufacture knows, that it will be used to pull the boat to the anchor and break it loose.)



In fact, the yanks a chain gets at anchor are not nearly as sudden as the jolts and vibrations chains face in both hauling and industry. And I'm pretty sure they have thousands of times more experience than sailors.



In fact, G4 chain is not rated for lifting or securing loads because it is NOT as tough (yield before break) or fatigue resistant as G7 chain. It has a history of failure in industry. You can Google this. OSHA and DOT agree. Every industry group agrees.


There is also a misconception that G7 is akin to hardened steel. In fact, it is good grade of spring steel, which is what you use for cyclical loads, like the springs under your car (G4 springs would last long).



This is just a durable urban legend.
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Old 09-10-2019, 05:14   #13
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Re: G70 chain vs G4

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Originally Posted by peter57 View Post
The less weight result will be less holding power, all good though if you are a marina jockey and don't anchor often.


Absolutely false. Weight in the chain is meaningless when itís pulled straight.
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Old 09-10-2019, 05:53   #14
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Re: G70 chain vs G4

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Absolutely false. Weight in the chain is meaningless when itís pulled straight.

I'm more of a moderate on this subject. Depending on the wind, weight helps. But only so much.


Another way of looking at this in many cases is that you can carry MORE G70 chain in the same locker a the same weight. An equal weight of G70 will offer better catenary than lower grade chain and will also bury better with the anchor. It more scope required? In some cases yes (poor holding ground), in some cases probably no (very strong winds when the chain gets straight) and the anchor wants to bury deep).



There are a range of answers, each with compromises.
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Old 09-10-2019, 09:59   #15
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Re: G70 chain vs G4

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I'm more of a moderate on this subject. Depending on the wind, weight helps. But only so much.


Another way of looking at this in many cases is that you can carry MORE G70 chain in the same locker a the same weight. An equal weight of G70 will offer better catenary than lower grade chain and will also bury better with the anchor. It more scope required? In some cases yes (poor holding ground), in some cases probably no (very strong winds when the chain gets straight) and the anchor wants to bury deep).



There are a range of answers, each with compromises.


Ok, Iíll buy that.
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