Worth the difference G40 v G70 anchor chain

[Thedreamoneday]

I'm looking to replace my anchor chain due to wanting longer length. I've looked on Jimmy Greens website, they offer Maggi G40 and G70, whilst I understand G70 is stronger (I'm probably going to go for this as I plan to anchor quite a lot) is it really that much better and if so, what is 'better' and what's wrong with G40? What's the 'actual' difference?

Is it noticeable, for example last longer?

Thanks

 

[Nigelb]

I thought the key benefit is that it might allow you to go down a chain size ie from 10mm to 8mm therefore reducing weight forward or allowing you to carry more scope. But the price differential is significant!

 

[macd]

G70 is essentially heat-treated G40, making it perhaps 25% stronger. The general view these days seems to be that the main point of going for the higher spec is to reduce the size (and thus weight) of the rode carried. Most boats manage perfectly well with G40 or G30.
G70 won't last any longer. That depends most of all on the quality of the galvanizing, not the rating of the chain.

Good info here (from one of the more illumiating forumites): https://coxengineering.sharepoint.com/Pages/Chaindefinitions.aspx

 

[Thedreamoneday]

I thought the key benefit is that it might allow you to go down a chain size ie from 10mm to 8mm therefore reducing weight forward or allowing you to carry more scope. But the price differential is significant!

You're right about the cost difference, it's nearly twice the price.

But is that the only benefit, down a size?

 

[NormanS]

Size for size the G70 is stronger, but how often do you hear of anchor chains breaking? if, like old-fashioned me, you believe that the catenary of the chain helps to absorb any shock loading, caused by yawing or waves, you will stick with heavy chain. If, on the other hand, you have a particularly light-displacement vessel, the lighter chain might be better for you.

 

[Deleted member 36384]

It is explained in the links below G40 is 400 MPa UTS and G70 700 MPa UTS according to data from the Rocna page.


https://www.morganscloud.com/2011/05/11/things-to-know-about-anchor-chain/
http://kb.rocna.com/kb/Chain

 

[Thedreamoneday]

Size for size the G70 is stronger, but how often do you hear of anchor chains breaking? if, like old-fashioned me, you believe that the catenary of the chain helps to absorb any shock loading, caused by yawing or waves, you will stick with heavy chain. If, on the other hand, you have a particularly light-displacement vessel, the lighter chain might be better for you.

My boat is a Moody 376, so reasonable displacement, currently has 45meters of 8mm chain, I'm after longer and I'm staying with 8mm so is it better to have G70 or will i not notice in any way?

G70 is essentially heat-treated G40, making it perhaps 25% stronger. The general view these days seems to be that the main point of going for the higher spec is to reduce the size (and thus weight) of the rode carried. Most boats manage perfectly well with G40 or G30.
G70 won't last any longer. That depends most of all on the quality of the galvanizing, not the rating of the chain.

Good info here (from one of the more illumiating forumites): https://coxengineering.sharepoint.com/Pages/Chaindefinitions.aspx

I'll have a good read of the above links, thanks.

 

[Neeves]

My boat is a Moody 376, so reasonable displacement, currently has 45meters of 8mm chain, I'm after longer and I'm staying with 8mm so is it better to have G70 or will i not notice in any way?



I'll have a good read of the above links, thanks.

If you intend keeping the same size chain you will be wasting your money. Reports of correctly sized and made by someone reputable G30 or G40 chain failing are noticeable by their absence. If G30 does not fail then it is strong enough so why go to G70.

The idea of using G70 is that you can use the smaller link size, so if you had 10mm you could down size to 8mm. However if you are usjg 8mm there is no G70 in 6mm so that option is closed. G70 is more expensive than G40 but if you were downsizing some of the price differential narrows.

Peerless (America) are now selling metric G70 (and G40) from their warehouse in Germany. You would need to contact them through their international sales office.

The biggest problem with G70, other than price, is that if you downsize you need a new gypsy and there are no connectors (shackles) that are small enough to fit the metric links and strong enough. You thesefore need to buy some form of connector, to get the compatible strength) and an 8mm Maggi connector (see their website) costs stg70 and is enormous (might not fit your bow roller).

As mentioned chain life is dictated by galvanising quality and that has nothing to do with strength. Peerless currently have the best galvanising.

Jonathan

 

[Neeves]

It is explained in the links below G40 is 400 MPa UTS and G70 700 MPa UTS according to data from the Rocna page.


https://www.morganscloud.com/2011/05/11/things-to-know-about-anchor-chain/
http://kb.rocna.com/kb/Chain

G70 has a UTS of 700 MPa prior to galvanising. The heat of galvanising degrades the strength by anything between 15% and 20% so the 700 MPa is incorrect for galvanised G70. Note that in America imperial G70 is sold with a 3:1 safety factor, G30 (imperial and metric) and metric G40 are sold with a 4:1 safety factor and Maggi's G70 a 5:1 safety factor. Sometimes UTS is not quoted only WLL (and then the safety factor is hidden in the small print). Quoting only WLL gives an inflated figure for imperial G70, etc, so take care with the data.

Jonathan

 

[vyv_cox]

The only significant advantage is the weight reduction. When Paul and Rachel Chandler refitted Lynn Rival after their return from capture they changed from 10mm G30 to 8mm G70. With the kind of chain length needed for world cruising this results in a saving of around 100 kg in the most affected part of the boat, plus a useful strength increase.

 

[Boo2]

The biggest problem with G70, other than price, is that if you downsize you need a new gypsy and there are no connectors (shackles) that are small enough to fit the metric links and strong enough. You thesefore need to buy some form of connector, to get the compatible strength) and an 8mm Maggi connector (see their website) costs stg70 and is enormous (might not fit your bow roller).

Istm that one reason for buying G70 chain is that is you really cannot get the hook out then using a stronger chain than shackle ensure you lose the least possible money when you do finally manage to break something ? Of course I don't know how hard it is to actually put a load of several tons on an anchor rode to achoeve that...

Boo2

 

[Neeves]

Istm that one reason for buying G70 chain is that is you really cannot get the hook out then using a stronger chain than shackle ensure you lose the least possible money when you do finally manage to break something ? Of course I don't know how hard it is to actually put a load of several tons on an anchor rode to achoeve that...

Boo2

If you are using branded 8mm G30 (or even unbranded Chinese chain from a reputable supplier) it will break at about 3,500kg to 4,000kg load (the minimum load it should break at is 3,000kg). The chain should be the 'weak link' - everything else should be stronger (anchor, shackle etc), Something on the yacht will break long before the chain, bow roller or you will pull the windlass out of the deck! The WLL of 8mm G30 is 750kg and the yield (when it starts to stretch) load is about 2 x WLL. In my testing yield is slightly more than 2 times WLL, so actual yield is at about 1,750kg. Good chain, G30, G40 and G70 should stretch about 15% - 20% before it breaks (some is much more brittle). But once the chain stretches at some point it will not fit into your gypsy (the links will be too long and it will jamb). I don't know how forgiving windlass gypsies are (to extra length) so I do not know when this mismatch occurs (and it may vary for different windlass suppliers). But reports of chains breaking are simply not available, nor are reports of chain stretching - so basically no-one puts the sorts of loads I describe on their chain - even in extremis. Chain does break and chain does stretch - but commonly its very old, or bought very cheaply.

Engines develop about 100kg thrust for every 10hp. So if you have a 30hp engine you can develop a thrust or load of about 300kg. To even get to the WLL you would need to take a run at it - and its not a practice I can recommend, or even suggest you consider. Cut your losses (and the chain), buoy it and come back prepared to dive on it.

Jonathan

 

[NormanS]

That's funny. A few weeks ago, I think it was you in another thread, was talking about the fantastic loads imposed on chain etc, when retrieving the anchor in a sea. I remember suggesting that if you were unduly worried about it, all you had to do was to adjust the clutch screw on the windlass, so that it would slip, rather than breaking or stretching the chain. Anglers do it all the time with their reels.

 

[Neeves]

I had interpreted Boo2's post as suggesting heavy force was one way of dislodging an irretrievably snagged anchor (caught in rock - not simply well set). In which case you would not want the clutch adjusted such that it slips. I had assumed he meant you could tug at the anchor and break it free but if you had G70 the chain would not break but a shackle might fail - I was suggesting this was unlikely (as the shackle should be stronger than the chain, G30 or G70) and the chain so strong you are more likely to rip the yacht apart than break the chain.

There is also a difference between using a force which you, the owner, impose and unpredictable snatch loads imposed by waves. In the latter having the clutch able to slip is obviously very advantageous - as you pointed out.

Jonathan

 

[noelex]

The only significant advantage is the weight reduction. When Paul and Rachel Chandler refitted Lynn Rival after their return from capture they changed from 10mm G30 to 8mm G70. With the kind of chain length needed for world cruising this results in a saving of around 100 kg in the most affected part of the boat, plus a useful strength increase.

This is the reason for buying G70 chain. By reducing the size of chain one step (say from 10mm to 8mm or 12mm to 10mm, there are very significant weight and storage savings.

This reduced weight and volume can be utilised by carrying a longer length of chain, a larger anchor, it can also be used to reduce the weight in the bow, or a combination of these benefits.

The first two will increase your holding ability and/or enable you to anchor at greater depths, the last one will increase your sailing performance.

If you don't want to go to the expense and trouble of reducing the chain size, there is no point going for G70 chain unless your existing chain has been selected incorrectly and is inadequate.

G70 chain is harder to get, you need to be more careful with connecting shackles and I suspect it is not as long lasting.

 

[Neeves]

G70 chain is harder to get, you need to be more careful with connecting shackles and I suspect it is not as long lasting.

Why do you suspect it does not last as long?

You can buy from Jimmy Green, or Peerless stock in Genrmany.

Jonathan

 

[IamDiscoDad]

I thought half the trick to holding well was the weight of the chain...

 

[Neeves]

I thought half the trick to holding well was the weight of the chain...

This is an old and discredited idea.

You can test that idea out yourself.

Deploy about 30m of chain, say 8mm, in shallow water. Take one end of the chain, pull it, and give it a bit pf grunt and you can pull it over the seabed, just you, single man power - the chain is offering virtually no hold at all.

Now add a decent anchor one designed for a 30'/35' yacht - you will need a decent 4x4 to break its hold - the anchor will hold to about 2,000kg assuming you are dragging chain and anchor over sand.

You can pull the chain - say about 100kg of tension, pulling the chain, and the 4x4 showing the anchor will hold about 2,000kg.

The chain offers no hold - you rely on the anchor. You could use dyneema, instead of chain, chosen to have the same WLL or tensile strength as chain - but effectively no weight. The trouble is the dyneema floats and will be a hazard to your own yacht, (its a yacht - the dyneema will tangled round the sail drive and keel) and be a hazard to passing yachts.

If you deploy 30m of appropriately sized chain and a decent anchor. and the wind gets up - then the chain will not touch the seabed at all - exactly what mechanism is allowing your chain to provide any friction at all. You can deploy more chain - if you have it, if there is room but the friction (as you prove with you pulling the chain) offers minimum of hold.

You can extend the testing a bit further.

Take a steel Spade or a steel Excel and compare the hold of the aluminium models. You will find the steel Excel or Spade, say 15kg models, have the same hold as the 8kg aluminium models. Similarly take a same sized genuine Danforth and compare with a Fortress and the 2 anchors, steel Danforth and aluminium Fortress will develop the same hold.

Its not weight but design. The aluminium versions may be, or not be, as strong, or of less robust strength - but that's an engineering issue. Excel beefs up its strength by using HT aluminium, the 5075 alloy (costing an eyewaterinw amount) - but the alloy versions develop similar hold to their steel brothers.

Jonathan

 

[NormanS]

I expect that ten years having passed, the OP has made his decision about his chain.

 

[Seven Spades]

I can/t see the advantage. You want the chain to be heavy for the full caterinary effect. The heavier the chain the less chain you will need to deploy.