Can I use 8mm chain on a 40ft boat?

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I sail a 40ft seven tons awb, anchoring regularly around the north west Scotland. The boat currently only has 35m of 10mm chain, which I'd like to increase to 60m.
The windlass hasn't been working well the last couple of seasons and is probably twenty years old and may need changing.

Can I go to 8mm chain?
Main advantages would be decreased weight and the chain would pack away easier into the locker.

Thanks.
 
some 8mm chain is proof tested to above the BS of 'ordinary' 10mm.

You would need to look at the specs and proof certificate; it's a techy decision.

But if you believe that chain weight on the sea bed is what stops anchors dragging, then staying with 10mm is 'better'.
 
Vyv will confirm or deny this, you'd be well within the theoretical load capacity of good 8mm G30 chain @ 3.2 tonnes ULT and, on an American website you'd probably be urged to consider 6mm G70 chain.

These sites should further confuse (or give you the information to make a more nuanced decision)

www.morganscloud.com/2007/05/01/breaking-load/

alain.fraysse.free.fr/sail/rode/anchor/anchor.htm
 
sarabande said:
some 8mm chain is proof tested to above the BS of 'ordinary' 10mm.

You would need to look at the specs and proof certificate; it's a techy decision.

But if you believe that chain weight on the sea bed is what stops anchors dragging, then staying with 10mm is 'better'.
Click to expand...

I upgraded from 8mm to 10mm, boat is 38' 11 tons, no regrets, I am of the school who believes weight is important, other threads in here would disagree, but thats what being subjective is and we may agree to disagree. From memory the 10mm is about 1.3 kilos heavier than the 8mm, my anchor locker is big enough to take the 70m with room to spare, may add another 20m to it. Has had no effect on how she lies in the water, takes a bit more than the extra to get her bows down, has a long very heavy keel, but if you do upgrade be aware of the possible effect on yours.
 
We have a boat similar to yours with 90m x 8mm chain and a 20kg Spade. Being in the eastern Mediterranean we anchor 90% of the time and have no issues at all.

John
 
You have the option of going to a stronger grade. As has been suggested, grade 70 is the strongest available in galvanised marine chain, 8 mm G70 is twice as strong as 10 mm G30 and less than half the weight. Alternatively you could go to grade 40. I know someone who bought Maggi Grade 70 in Levkas so this could be a good option for you. Most Chinese chain is well made grade 30 that meets grade 40 spec. It is possible to buy Turkish and Greek made chain but I would be wary of them.
 
Depends where you will anchor and what conditions - I believe that the weight of the chain is important in stopping a boat dragging, so 10mm would be my choice. We have 80 metres of 10mm on a 12.3m LOA boat
 
Many thanks for all the replies. Thought it was doable, but it's always good to hear of others experiences. Using 8mm chain, also means that I can go longer as well, so can possibly go for 80 metres instead of 60 metres.
 
I'm Ionian based as well and I'm going to change down from 10mm to 8mm so I can get another 20 m in the locker and get a chain that piles more easily.

Anchored in Levkas with just 2m of water under the keel last year, about 65m of 10mm chain out and 40kts steady over the deck the chain was bar taut, no way was the weight of the chain on the bottom any help! It was all up to the CQR which over the course of a couple of hours, ploughed about 50m through the muck at the bottom of the harbour.

I only need to replace my gypsey as the rest of the windlass works fine. Going to have to machine an adaptor for a newer model as my windlass is obsolete though.

Having 100m in the locker allows anchoring a bit further out when it gets crowded!
 
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PhilipH said:
I believe that the weight of the chain is important in stopping a boat dragging, so 10mm would be my choice.
Click to expand...

This is a picture of what is happening underwater.

This is just with the setting force of the engine. In strong wind the force will be much higher. Not much catenary visible here. It is hard to imagine an increase in chain size would make much difference to the angle of pull at the shank.

image.jpg1_zpsx3qyrjee.jpg
 
vyv_cox said:
You have the option of going to a stronger grade. As has been suggested, grade 70 is the strongest available in galvanised marine chain, 8 mm G70 is twice as strong as 10 mm G30 and less than half the weight. Alternatively you could go to grade 40. I know someone who bought Maggi Grade 70 in Levkas so this could be a good option for you. Most Chinese chain is well made grade 30 that meets grade 40 spec. It is possible to buy Turkish and Greek made chain but I would be wary of them.
Click to expand...

vyv

who sells this good quality chain and how can you tell?
 
nimbusgb said:
I'm Ionian based as well and I'm going to change down from 10mm to 8mm so I can get another 20 m in the locker and get a chain that piles more easily.

Anchored in Levkas with just 2m of water under the keel last year, about 65m of 10mm chain out and 40kts steady over the deck the chain was bar taut, no way was the weight of the chain on the bottom any help! It was all up to the CQR which over the course of a couple of hours, ploughed about 50m through the muck at the bottom of the harbour.

I only need to replace my gypsey as the rest of the windlass works fine. Going to have to machine an adaptor for a newer model as my windlass is obsolete though.

Having 100m in the locker allows anchoring a bit further out when it gets crowded!
Click to expand...

It would seem fairly obvious that if you are anchored in such shallow water, no chain of any weight or description is going to give a useful catenary. In such shallow water, a little bit of chain next the anchor, and then stretchy nylon would be much better.
Conversely, if you anchor in deeper water, say 10 metres or more, there is a real benefit in the catenary in the chain. It's horses for courses, so ideally, it's better to be prepared for all eventualities, so plenty chain, plenty stretchy rope, and plenty anchors, used appropriately.
 
noelex said:
This is a picture of what is happening underwater.

It is hard to imagine an increase in chain size would make much difference to the angle of pull at the shank.
Click to expand...

You don't understand anything about the mathematics of catenaries evidently.
 
robertj said:
vyv

who sells this good quality chain and how can you tell?
Click to expand...

No doubt Vyv will be along shortly with an informed answer.
The 'How can you tell' will depend on the certification, if any, which arrived with the chain at the vendor.

In the meantime and out of curiosity I googled both Grade 70 and Grade 40 for UK sites, and found a predictable paucity of hits, and many of those were hits on threads here, often generated by questions such as yours. Hacketts, the chain and lifting gear specialist, scored hits for Grades 40 and 50 but not 70: http://www.williamhackett.co.uk
Jimmy Green Marine seem to be one of the exceptions, offering useful general information about chain products, plus chain specified as Grade 40 (and something referred to as Aqua7, which may be G70).

So my supplementary question of Vyv is why does such a parlous state of affairs prevail? Is it because we, the consumers, are ignorant or indifferent? Is it because the suppliers (chandlers in the main, I daresay) are unprofessional? To my mind this is an issue every bit as vital as that of brass skin fittings, and every bit as mired in poor practice. Is it this bad elsewhere?
 
noelex said:
This is a picture of what is happening underwater.

This is just with the setting force of the engine. In strong wind the force will be much higher. Not much catenary visible here. It is hard to imagine an increase in chain size would make much difference to the angle of pull at the shank.

image.jpg1_zpsx3qyrjee.jpg
Click to expand...

Great image, and completely useless :)

You were 2m of water with 8m of chain or 10m of water with 50m of chain? The chain is 6mm and a 60hp engine or 12mm and a 30hp engine?

Jonathan
 
MacD

There are a series of articles on chain in Practical Sailor 2014/15, Vyv's article in YM and on his website. Between them this resource covers G30, G40, G43 and G70.

There are only 2 suppliers of metric gal G70, Peerless (under their ACCO brand) and Maggi, branded Aqua7 (and Aqua4 for their G40 quality).

Usage of G70 is 'newish' and consequently user feedback limited. Possibly a reason for the paucity of feedback is that the majority of vessel owners use 8mm chain and to enjoy downsizing (and saving of weight) you would want to use 6mm chain - and no-one makes a 6mm gal G70 chain. The smallest metric chain available is 8mm, which might replace 10mm chain.

You should look to buy chain with a certificate of quality - if there is no certificate you should wonder why, as most reputable manufacturers will Proof Test every link and break test every batch. Determining galvanising quality is more of an issue, as no manufacturer provides any detail - but it is possible to measure gal thickness, see Practical Sailor, Jan 2015. The thicker the gal - the longer it will last. Anything less than 100 microns of gal should be avoided.

Chain failure of new chain, G30, G40, G43 and G70 is very rare. There are occasional instances but most chain failures are old chain or purchased from nefarious sources.

As Vyv has found through testing most chain in the UK available now is of Chinese origin and excellent quality but there is some Chinese chain that is of a lower quality. As most (all?) Chinese manufacturers do not mark their chain it is impossible to determine good from bad - though Vyv has a test on his website. Again, ask for a test certificate - if it is not available for your specific batch, perhaps wonder why not.

Jonathan
 
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