Changing from 10mm galvanised chain to 8mm stainless

[Irish Rover]

The 10mm galvanised chain on my boat is very rusty and I'm planning to change it. My anchor is s/s and I'd really like to have s/s chain as well to avoid future rust problems. I'd also like to have lighter chain which I think would make it easier for my wife getting the bridle on and off which is why I'm thinking about 8mm chain. The laden displacement of my 43' catamaran is around 14 tonnes. I've looked at the 8mm stainless available here in Türkiye and the standard is given as AISI 316. This has a working weight limit of 8.2 tonnes which doesn't appear adequate for my boat. So is changing to 8mm s/s a non runner?

 

[geem]

You need cromox s/s and deep pockets. Made in Germany

 

[noelex]

For warm salty waters such as the Mediterranean, you really need exotic compositions such as "duplex" (for example, 318) or "super duplex" stainless steels rather than 316. These are expensive.

Cromox makes both 316 and 318 anchor chains in G6. You will need 318, preferably with the enhanced electro polished finish.

G6 provides more strength than G4, but 8 mm stainless steel G6 chain is very marginal for your sized vessel.

 

[Irish Rover]

It has been suggested to me that 8mm G43 galvanised chain could be used instead of the 10mm G30 which I have at present. I haven't a clue so would be grateful for any guidance.

 

[GEM43]

I’ve just researched Cromox 8mm for my boat. 80m is £5,500. Then my wife tells me we’d need a shiny anchor to match. So about £8,500 all in then. That’s definitely not happening.

 

[Zing]

I just ran this exercise. I decided to go to G70 galv and downsize. Stainless didn’t make sense as it didn’t allow much of a downsize and the value for money was terrible.

Note you will probably need a new gypsy and depending on windlass it can be very expensive.

 

[Irish Rover]

So it seems downsizing from 10mm galvanised to 8mm stainless is a non starter. However my research tells me the wwl of 8mm G43 galvanised is nearly 50% higher than the 10mm G30. I appreciate I need to change the gypsy at a cost of €250 approx. Now I just need to see if I can find a reliable supplier of G43 in Türkiye.

 

[vyv_cox]

So it seems downsizing from 10mm galvanised to 8mm stainless is a non starter. However my research tells me the wwl of 8mm G43 galvanised is nearly 50% higher than the 10mm G30. I appreciate I need to change the gypsy at a cost of €250 approx. Now I just need to see if I can find a reliable supplier of G43 in Türkiye.

See my website for chain data. A common change is replacing 10 mm grade 30 with 8 mm grade 70. This saves considerable weight and is stronger. If you remember the Chandlers, Lynn Rival, that is what they did when rebuilding their boat after their kidnapping. A successful improvement.

G43 is an American grade that may not be widely available in Europe.
Chain

 

[Daydream believer]

Speak to the stainless steel federation in the UK. The general director that runs it is a keen sailor & is very interested in boaty queries. As I found out, when researching making rope cutters. He can blind you with science about the correct grades of ss to look for

 

[GEM43]

Is anyone aware of the existence of reliable load data for anchor rode? I have G70 chain but often wonder whether that degree of strength (7t) is needed. Could an anchor really hold a 7t pull? Could the deck cleat withstand a 7t load? Does a 70kt wind exert a 7t pull on a 15t monohull? Is 3t WLL perfectly adequate?

 

[Roberto]

Is anyone aware of the existence of reliable load data for anchor rode? I have G70 chain but often wonder whether that degree of strength (7t) is needed. Could an anchor really hold a 7t pull? Could the deck cleat withstand a 7t load? Does a 70kt wind exert a 7t pull on a 15t monohull? Is 3t WLL perfectly adequate?

Before breaking a chain will deform, and that would most probaby render it useless, at least the section which had deformed. FWIW I deformed my 10mm chain (spike loads of unknown entity), the links ''settled'' against each other on a given length and it became very stiff, after that it jumped every time it went over the gypsy and generally was a mess to deal with, until I cut the section away and eventually bought a new chain.

Later addition
Dangerous loads on the chain usually do not happen (only) during the 200kt blows of the strongestestest hurricanes, providing one integrates sufficient snubbing/elasticity precautions, but in other situations. Example deeply embedded anchors being retrieved when there are waves moving the bow up and down more or less violently: I use a short strop with a quick chain hook to advance little by little on the chain (and avoid at all cost the spike loads on the windlass), trying to exert sufficient force to slowly upturn the anchor from the soil and not letting the chain becoming bar taut, except a couple of bigger waves might momentarily get it bar taut, the whole boat bangs and vibrates, despite all precautions the chain deforms or breaks. On another occasion, anchorage on a rocky bottom after a few swings with the tide the chain got wrapped more and more by the bottom until it became almost vertical from the bow, again impressive loads on a single length of chain and anchor totally unloaded (and there was only current, albeit very strong).
If you can avoid those types of situations then windage might become your main parameter, I personally cannot be sure -lived through both types of situation- so prefer having chain with some excess reserve resistance.

 

[geem]

Is anyone aware of the existence of reliable load data for anchor rode? I have G70 chain but often wonder whether that degree of strength (7t) is needed. Could an anchor really hold a 7t pull? Could the deck cleat withstand a 7t load? Does a 70kt wind exert a 7t pull on a 15t monohull? Is 3t WLL perfectly adequate?

Have a play on ChatGP. You can ask it specific questions and it will show you the calculations and assumptions. Just keep refining the inputs until you get what you want

 

[ashtead]

I asked on a separate post if I needed to replace my galvanised 60m chain if buying a shiny new anchor to replace existing Lewmar -general view was not needed-if buying a chain for all that cash I would shell out for stainless steel-I guess it depends how much you anchor though per annum -in relation to cost of a 14tonne cat it seems modest expense and compared to marina charges maybe on a per day basis? How many more years do plan crusing before selling up etc?

 

[barca nova]

The 10mm galvanised chain on my boat is very rusty and I'm planning to change it. My anchor is s/s and I'd really like to have s/s chain as well to avoid future rust problems. I'd also like to have lighter chain which I think would make it easier for my wife getting the bridle on and off which is why I'm thinking about 8mm chain. The laden displacement of my 43' catamaran is around 14 tonnes. I've looked at the 8mm stainless available here in Türkiye and the standard is given as AISI 316. This has a working weight limit of 8.2 tonnes which doesn't appear adequate for my boat. So is changing to 8mm s/s a non runner?

if you ever got near to even half of the 8.2 tonnes limit you would rip your cleat out of the deck. But why on earth do you want to add the weight of a steel chain to a cat which sails best with low weight

The only benefit of a heavy chain is in the weight of the catenary. If your boat ever pulls that chain straight, then the shock load will either pull out the anchor or the deck fixing. By far the best solution is chain at the bottom to resist abrasion then a long length of stretch 3 core nylon rope to give shcok absorption.

 

[Irish Rover]

if you ever got near to even half of the 8.2 tonnes limit you would rip your cleat out of the deck. But why on earth do you want to add the weight of a steel chain to a cat which sails best with low weight

The only benefit of a heavy chain is in the weight of the catenary. If your boat ever pulls that chain straight, then the shock load will either pull out the anchor or the deck fixing. By far the best solution is chain at the bottom to resist abrasion then a long length of stretch 3 core nylon rope to give shcok absorption.

?

 

[fredrussell]

if you ever got near to even half of the 8.2 tonnes limit you would rip your cleat out of the deck. But why on earth do you want to add the weight of a steel chain to a cat which sails best with low weight

You weren’t to know as it’s not mentioned in OP but Irish Rover has a motor-cat. No sailing involved.

 

[barca nova]

Thank you Fred. I would still be concerned, perhaps even more so since motor cats look to have more windage . The strength of a system is its weakest link and in the case of an anchor with chain it is either the grip of the anchor or the strength of the cleat fixing. Snatching when the chain is pulled taut with test both these points.

I'll put it another way. Would you like to do a bungy jump with a steel wire rather than an elastic one?

 

[Irish Rover]

Thank you Fred. I would still be concerned, perhaps even more so since motor cats look to have more windage . The strength of a system is its weakest link and in the case of an anchor with chain it is either the grip of the anchor or the strength of the cleat fixing. Snatching when the chain is pulled taut with test both these points.

I'll put it another way. Would you like to do a bungy jump with a steel wire rather than an elastic one?

I'm struggling to understand what point you're trying to make in the context of my wish to change to a lighter chain, but if you've something useful to add I'd be happy to hear it.

 

[NormanS]

Thank you Fred. I would still be concerned, perhaps even more so since motor cats look to have more windage . The strength of a system is its weakest link and in the case of an anchor with chain it is either the grip of the anchor or the strength of the cleat fixing. Snatching when the chain is pulled taut with test both these points.

I'll put it another way. Would you like to do a bungy jump with a steel wire rather than an elastic one?

Chain on cleat??

 

[Zing]

Thank you Fred. I would still be concerned, perhaps even more so since motor cats look to have more windage . The strength of a system is its weakest link and in the case of an anchor with chain it is either the grip of the anchor or the strength of the cleat fixing. Snatching when the chain is pulled taut with test both these points.

I'll put it another way. Would you like to do a bungy jump with a steel wire rather than an elastic one?

A snubber would be usually applied to make this a non-issue.