Anchor chain 8mm or 10mm

[eddystone]

I am truly loath to start another anchoring thread but my simple proposition is as follows:
Intend replacing the 21kg plough and chain on 1999 Bav 42, 43.5’ish LOA and 8.5 ton displacement with Rocna mk1 25kg and 60 m G40 8mm and 30 metre octoplait.
Bav say German Lloyds say 8mm good for this size of boat; Jimmy Green tables say need 10mm.
What size would you go with? (oh and what diameter rope to splice on?)

 

[GEM43]

I went with 80m of G70 8mm from Jimmy Green. Greater strength than 10mm g40 whilst being considerably lighter. 25kg Vulcan, 44ft loa, monohull. 10m snubber run to midship cleat. Proven its efficacy in some windy conditions in W Scotland. I'm content with it. I'm not a great believer in the theory of a heavy chain catenary for strong winds.

 

[vyv_cox]

8 mm grade 70 is nearly 1.5 times stronger than 10 mm grade 30 and around 2/3 of the weight, so a considerable saving for 100 metres, about 80 kg less. However, if you need to change your windlass gypsy the cost can be considerable.
Lots of info here Chain

 

[Sea Change]

What's the effect on chain and galvanising lifespan if you go down a size?

 

[noelex]

What's the effect on chain and galvanising lifespan if you go down a size?

In my experience, it has a significant effect on shortening the chain life, at least switching from 12mm G40 to 10mm G70.

 

[geem]

In my experience, it has a significant effect on shortening the chain life, at least switching from 12mm G40 to 10mm G70.

We get circa 3 years from our chain in full-time cruising mode. In the Caribbean is almost impossible to get it regalvanised. We have to replace it or the rust flakes on deck start to make a real mess. For us, G45 chain in 10mm does the trick. It's actually cheaper to buy in the French islands than it is back in the UK.

 

[GEM43]

We get circa 3 years from our chain in full-time cruising mode. In the Caribbean is almost impossible to get it regalvanised. We have to replace it or the rust flakes on deck start to make a real mess. For us, G45 chain in 10mm does the trick. It's actually cheaper to buy in the French islands than it is back in the UK.

Interesting, how many nights at anchor over the three years? I see that 80m of G70 8mm is £1400 from JGM, so if you’re at anchor for 1,100 nights (3 years) that’s about £1.25/nt. I reckon that’s reasonable, we have to accept that most things on board are consumables, nothing lasts forever.

 

[vyv_cox]

What's the effect on chain and galvanising lifespan if you go down a size?

Galvanising is never as good on heat treated alloy steel as it is on mild. Not sure why this should be but it does seem to be the case.

 

[noelex]

We get circa 3 years from our chain in full-time cruising mode. In the Caribbean is almost impossible to get it regalvanised. We have to replace it or the rust flakes on deck start to make a real mess. For us, G45 chain in 10mm does the trick. It's actually cheaper to buy in the French islands than it is back in the UK.

10mm G40 is a reasonably sized chain for your yacht, so I would expect a typical chain life. If you decreased to 8mm G70 (which has a similar strength), the lifespan would be less, assuming other factors were equal.

PS: where did you find the best deal for chain in the Caribbean.

 

[Sea Change]

We currently have 12mm chain. 47ft 11.5t boat.
It's up for replacement, and I already have a spare windlass with a 10mm gypsy (plus a functioning stripper arm... which the one with the 12mm lacks... grrr).
I can see a strong argument for buying new 10mm chain. The current stuff piles up quickly in the locker and I need to clear it every 6-8m or so.

If I go down to 10mm, should I be considering a stronger grade?

 

[geem]

10mm G40 is a reasonably sized chain for your yacht, so I would expect a typical chain life. If you decreased to 8mm G70 (which has a similar strength), the lifespan would be less, assuming other factors were equal.

PS: where did you find the best deal for chain in the Caribbean.

Thr boatyard in Le Marin were cheapest last two times we were there

 

[geem]

We currently have 12mm chain. 47ft 11.5t boat.
It's up for replacement, and I already have a spare windlass with a 10mm gypsy (plus a functioning stripper arm... which the one with the 12mm lacks... grrr).
I can see a strong argument for buying new 10mm chain. The current stuff piles up quickly in the locker and I need to clear it every 6-8m or so.

If I go down to 10mm, should I be considering a stronger grade?

We weigh 18/19 tonnes so no option to drop to 8mm unless we go to G70. G40 10mm would be fine for your weight

 

[Neeves]

There is no evidence that smaller chain loses its galvanising faster than heavy chain. There may be a difference but given the variables and the fact you cannot compare like with like - the idea is another phurphy - dreampt up to justify heavier chain. I conducted some abrasion tests on chain of various sizes, so comparing like with like - and though abrasion was severe (in my test) there was no difference between 12mm and 6mm chain. The big difference was in the method of galvanising.

Light chain would be criticised as not being on the seabed, its more easily lifted - if this is true it is abraded less frequently than heavy chain. Abrasion is a function of weight (of the link) heavier for a larger chain and area - and the light weight is 'balanced' by smaller area.

Hot dipped galvanised, HDG, chain, the common method for galvanising, is coated to a gal thickness of about 80 microns (if you are lucky). The fact chain galvanising lasts for 4 years - which seems to be a common life for liveaboards, is amazing - that's 20 microns a year or roughly 1.5 microns a month.

An alternative method of galvanising is Thermal Diffusion Galvanising, TDG, aka Sherardising, Green Cote, Armorgalv (there maybe other variants. The beauty of TDG is that the coating is harder (more abrasion resistant) and you can specify coating thickness which can be achieved with a surprising degree of accuracy (our Armorgalv coated chain was coated to a specification of 100 microns (so more of a harder coating) the US Navy specifiy 80 microns.

Armorgalv was more abrasion resistant in my tests and is one reason the US Navy use the process (the other reason being - they cote HT chain and can therefore use lighter chain, which is easier to handle. They calculate that the longer life of TDG chains saves than millions of US$.

There is (maybe are) Shardising facilities in the UK, Green Cote operate In Europe and there are at least 2 Armorgalv operators in Israel (where their specific process was developed there are plants in the US and Oz). The Israeli Armorgalv facilities and the one in Oz and one in the US have processed leisure anchor chain. I'm involved, but not commercially, in Oz where 1000m of chain have been processed to date. I developed the process for chain in Oz and I act as an unpaid quality control technician for people who 'have seen the light', hence the 1,000m of chain

Apparently Viking Anchors are looking at establishing a fabrication facility in Asia - they may use TDG for their galvanised process (to a 100 micron specification)

As Vyv mentions high tensile steels don't take to HDG galvanising as well as lower tensile steels. The TDG process, which operates at lower temperature than HDG is a better process than HDG (because it does not re-temper the steel) - but allows a thicker and harder coating to be applied to the higher tensile chain - which is why our 6mm HT chain was coated to 100 microns.

Abrasion is not the only process that removes galvanising - acidic seabeds (common in estuarine locations and 'old' port facilities) will remove galvanising (of any process.much more quickly than abrasion - don't anchor in locations where the mud smells of 'sulphur'.


If you want a longer lasting chain and also want to down size then talk to the Sharadising facility in the UK. Buy grit blasted G100 chain, specify a 100 micron coating and enjoy another benefit of the 21st century. Don't fear light chain - the catenary you are sacrificing can be replaced entirely by a good snubber, the chain will last longer, your power demands will reduce and you will have more space in your locker. The TDG coated G100 x 6mm chain will have a WLL similar, slightly less, to the G30 x 10mm chain it replaces. But demand the 100 micron coating and check that you get it!


If I'd known then what I know now I would have considered coating a 4mm G100 chain not the 6mm chain we used (to replace G30 x 8mm chain). One downside that is a discouragement is that no-one makes a windlass with a 4mm gypsy (though you could, possibly, use a horizontal drum winch.

Jonathan

 

[geem]

There is no evidence that smaller chain loses its galvanising faster than heavy chain. There may be a difference but given the variables and the fact you cannot compare like with like - the idea is another phurphy - dreampt up to justify heavier chain. I conducted some abrasion tests on chain of various sizes, so comparing like with like - and though abrasion was severe (in my test) there was no difference between 12mm and 6mm chain. The big difference was in the method of galvanising.

Light chain would be criticised as not being on the seabed, its more easily lifted - if this is true it is abraded less frequently than heavy chain. Abrasion is a function of weight (of the link) heavier for a larger chain and area - and the light weight is 'balanced' by smaller area.

Hot dipped galvanised, HDG, chain, the common method for galvanising, is coated to a gal thickness of about 80 microns (if you are lucky). The fact chain galvanising lasts for 4 years - which seems to be a common life for liveaboards, is amazing - that's 20 microns a year or roughly 1.5 microns a month.

An alternative method of galvanising is Thermal Diffusion Galvanising, TDG, aka Sherardising, Green Cote, Armorgalv (there maybe other variants. The beauty of TDG is that the coating is harder (more abrasion resistant) and you can specify coating thickness which can be achieved with a surprising degree of accuracy (our Armorgalv coated chain was coated to a specification of 100 microns (so more of a harder coating) the US Navy specifiy 80 microns.

Armorgalv was more abrasion resistant in my tests and is one reason the US Navy use the process (the other reason being - they cote HT chain and can therefore use lighter chain, which is easier to handle. They calculate that the longer life of TDG chains saves than millions of US$.

There is (maybe are) Shardising facilities in the UK, Green Cote operate In Europe and there are at least 2 Armorgalv operators in Israel (where their specific process was developed there are plants in the US and Oz). The Israeli Armorgalv facilities and the one in Oz and one in the US have processed leisure anchor chain. I'm involved, but not commercially, in Oz where 1000m of chain have been processed to date. I developed the process for chain in Oz and I act as an unpaid quality control technician for people who 'have seen the light', hence the 1,000m of chain

Apparently Viking Anchors are looking at establishing a fabrication facility in Asia - they may use TDG for their galvanised process (to a 100 micron specification)

As Vyv mentions high tensile steels don't take to HDG galvanising as well as lower tensile steels. The TDG process, which operates at lower temperature than HDG is a better process than HDG (because it does not re-temper the steel) - but allows a thicker and harder coating to be applied to the higher tensile chain - which is why our 6mm HT chain was coated to 100 microns.

Abrasion is not the only process that removes galvanising - acidic seabeds (common in estuarine locations and 'old' port facilities) will remove galvanising (of any process.much more quickly than abrasion - don't anchor in locations where the mud smells of 'sulphur'.


If you want a longer lasting chain and also want to down size then talk to the Sharadising facility in the UK. Buy grit blasted G100 chain, specify a 100 micron coating and enjoy another benefit of the 21st century. Don't fear light chain - the catenary you are sacrificing can be replaced entirely by a good snubber, the chain will last longer, your power demands will reduce and you will have more space in your locker. The TDG coated G100 x 6mm chain will have a WLL similar, slightly less, to the G30 x 10mm chain it replaces. But demand the 100 micron coating and check that you get it!


If I'd known then what I know now I would have considered coating a 4mm G100 chain not the 6mm chain we used (to replace G30 x 8mm chain). One downside that is a discouragement is that no-one makes a windlass with a 4mm gypsy (though you could, possibly, use a horizontal drum winch.

Jonathan

The accepted rule is that once you have lost 10% of the chains diameter, it is scrap. You obviously lose 10% more quickly in 8mm chain than 10mm chain.
When you consider that 8mm chain will be dragged around more than the heavier 10mm chain, then I think it is fair to assume that 8mm chain won't last as long as 10mm chain due to abrasion. You pointed this out yourself. This is very relevant in a liveaboard boat where you spent the vast majority of your time at anchor.
Most people will not go to the trouble of buying none galvanised chain and having it Sherardised for an extra unknown life expectancy. These just want off the shelf chain at reasonable cost.
These factors are why we buy G45 10mm chain in the Caribbean at reasonable cost and we don't drop to G70 8mm chain at considerable cost. We would be scrapping it in 4 years

 

[Supertramp]

I replaced G40 10mm with the same
recently on a high windage 36ft 8630kg nominal displacement. About 10000kg in cruising trim. I also have a 25kg anchor (Epsilon).

I would have been happy with G70 8mm but decided it was not worth the cost to change (windlass gypsy change needed).

On the weight question, I concluded that on a cruising boat like mine the extra 60kg is a drop in the ocean, even given its location. I would feel differently if I was racing, travelling light or in a multihull.

I don't leave rope attached and store only chain in the locker to stop the chain sitting on damp rope. I hose the locker with fresh water on return to my home marina. I am at anchor for about 60 nights a year so slowing in-locker corrosion worries me more than in use effects.

 

[Bobc]

10mm chain and a 25Kg Rocna on my Bavaria 49. Perfect.

 

[Neeves]

The accepted rule is that once you have lost 10% of the chains diameter, it is scrap. You obviously lose 10% more quickly in 8mm chain than 10mm chain.
When you consider that 8mm chain will be dragged around more than the heavier 10mm chain, then I think it is fair to assume that 8mm chain won't last as long as 10mm chain due to abrasion. You pointed this out yourself. This is very relevant in a liveaboard boat where you spent the vast majority of your time at anchor.
Most people will not go to the trouble of buying none galvanised chain and having it Sherardised for an extra unknown life expectancy. These just want off the shelf chain at reasonable cost.
These factors are why we buy G45 10mm chain in the Caribbean at reasonable cost and we don't drop to G70 8mm chain at considerable cost. We would be scrapping it in 4 years

The 2 reputable proponents of G70 chain were both Americans, Dashew and Starzinger - I think Dashew was the individual who started the usage and had ACCO, which became part of Peerless, galvanise G70 Transport Chain. I think both are highly respected as long term cruisers with a significant presence in high latitude cruising. Starzinger was awarded medals for his exploratory work and Dashew renowned for his expedition motor yachts (in which he advocated lightweight chain).

I'm don't determine what other people might want or do - I simply suggest there is an option and if you are so inclined it is possible to have a custom rode made to your own specification. The fact that a number of owners in Australia have taken my ideas on board and collectively had 1,000m of light, high tensile, chain galvanised suggest some people put their money in my ideas and suggesting they can be bothered. Australians have never been reputed to be flamboyant with their money - it seems Australians think the concept is good value for money.

If you want sophistication, North Sea oil rigs, you buy much more expensive G120. G100 black chain is a commodity - in Australia its not expensive and I'm sure its cheap as chips in the UK.

The US Navy have replaced 'conventional' HDG chain with lighter, high tensile TDG chain, some of which is G120 - because it saves money. I don't know what chain it replaced G30 or G43. The chain they chose was smaller link sized and Armorgalv coated. The replaced chain was retired because the larger chain abrades more quickly than the smaller HT TDG link. The US Navy were scrapping their original chain well within 4 years.

Jonathan

 

[fredrussell]

We get circa 3 years from our chain in full-time cruising mode. In the Caribbean is almost impossible to get it regalvanised. We have to replace it or the rust flakes on deck start to make a real mess. For us, G45 chain in 10mm does the trick. It's actually cheaper to buy in the French islands than it is back in the UK.

I assume you’ve done the calculations to compare stainless chain with galvanised. How many years would the stainless chain have to last to make it comparable (on a cost basis) with galvanised chain I wonder?

 

[geem]

I replaced G40 10mm with the same
recently on a high windage 36ft 8630kg nominal displacement. About 10000kg in cruising trim. I also have a 25kg anchor (Epsilon).

I would have been happy with G70 8mm but decided it was not worth the cost to change (windlass gypsy change needed).

On the weight question, I concluded that on a cruising boat like mine the extra 60kg is a drop in the ocean, even given its location. I would feel differently if I was racing, travelling light or in a multihull.

I don't leave rope attached and store only chain in the locker to stop the chain sitting on damp rope. I hose the locker with fresh water on return to my home marina. I am at anchor for about 60 nights a year so slowing in-locker corrosion worries me more than in use effects.

Our boat is 18/19t in cruising trim. We plan to cruise the Caribbean and beyond for next few years. Converting to 8mm chain for us would be a problen apart from the need to swap gypsies, when we can't replace rusted out 8mn G70 or get it regalvanised. At that point we would be back to 10mm G40. It isn't worth the expense or hassle on our heavy boat. We gain nothing

 

[Neeves]

Our boat is 18/19t in cruising trim. We plan to cruise the Caribbean and beyond for next few years. Converting to 8mm chain for us would be a problen apart from the need to swap gypsies, when we can't replace rusted out 8mn G70 or get it regalvanised. At that point we would be back to 10mm G40. It isn't worth the expense or hassle on our heavy boat. We gain nothing

Frankly the difference in galvanising rate loss between 8mm or 10mm chain is 'nothing'. If it were years different it would be important but its probably dictated by the quality of the galvanising not the chain size and the day of the week it was galvanised..

If you swap your gypsy from 10mm to 8mm it would be prudent to keep the 10mm gypsy anyway - its not as if its a great weight.

Interestingly Starzinger and Dashew both thought down sizing had merit and Dashew's yachts were around 40,000kgs, Hawk I recall was around 14t`and 47' aluminium Van De Stadt.

But its only a difference of 85kg on your yacht, 100m of either 8mm or 10mm - it does not even merit a discussion

Jonathan