Anchor chain: How rusty is too rusty

[Macka1706]

Well guess you will never understand if you refuse to read and learn from the extensive published data and just rely on what people have always done.

Nothing I have written or referred to can be remotely considered a flight of fancy. It is all documented and in the public domain.

Your claim that heavier chain helps better setting is simply not true. What sets anchors is the load applied not the weight of the chain. Watch any of the videos of anchors setting and you will see the chain lifting from the bottom before it moves the anchor. The angle of pull is determined by the scope - that is the more rode out in relation to the depth the lower the angle of pull. I read what that source of the diagram said and the diagram proves nothing and the sketchy explanation is just wrong. All it says is what it says - nothing about aiding setting of the anchor. That is your invention.

I did not say that the popularity of substantial chain means little in science. What I said is that science and empirical data based on it does not support the need for heavy chain. The use of heavy chain (and heavy anchors) long predates any serious scientific work and is embedded by for example the unchanged recommendations from various sources. The work on anchors and anchor design over the last 20 years has disproved most of the long held views on the subject.

I have never said to ignore catenary. All I have said is that there is no data that measures what it does nor what the difference is between different weights of chain in use. How can you make a rational decision about buying heavier chain than necessary if you don't know what additional benefit it brings?

I do not know why you continue to talk about the loss of strength due to corrosion as a reason for buying heavier chain. Why would any one do that? The safety margin of chain, even 6mm is far greater than any boat of the size the OP has could ever generate. That is a fact, and even a 50% loss in strength would still exceed the load the boat could apply.

Your last sentence does not make any sense. There is no need to compromise with 6mm chain. It is more than adequate in terms of strength. It will set his anchor in exactly the same way as heavier chain using the same scope. If you have difficulty with this then read the data on which it is based and the testing work that has been carried out to demonstrate this is so.

You are right and iffy.
Look at some shots of Ships and their anchoring. Specially Tankers we used to work with at refinery's 99% the "heavy" chain is laid along seabed. with multi ton of anchor just laying there.
IF they don't physically backup and set it. Or a Cyclone happens along. That's where it stays until they winch it up again. THEY hold. And many a time (when younger) We'd pop over the side and most yachts around us were laying to their chains with picks just laying there or part set. Specially in sand.
I always have a lighter line with bright orange float on end. Spliced on tipping eye on front of "most" picks. VERY handy in rocks, coral, and weed.o
The "strength " of chain links is highly reduced if you stay on pick over multiple tides. you twist and twist and twist.
I saw a 45ft steelie once in river up Norh after a coupla weeks his chain had shortened that much it pulled the pick and while at work she drifted down to the mouth.(Daintree). Another one. He actually snapped a link. ALWAYS install at least one swivel in ALL anchors at Stock end..

 

[Macka1706]

Just consider how many boats you have seen with chain rigging.

Go back in my generation when Stainless shrouds and stays etc didn't exist. (too exxy)
Galv was king. BUT 90+% of us trawlermen/Sailors. Had some chain for bottom metre of shrouds etc. As Salt water infiltrated and killed the Galv wire Quick Smart.

 

[NormanS]

Norman - you must be bored. It must be pleasant to have so much time on your hands. You were the one to mention rigging.

J

Jonathan, I spilled my breakfast tea over that one. Bored? It's not me that writes interminable essays, basically saying the same thing.
Anyway, I'll be out of your hair in a day or two. Just getting set for a six week cruise. If I see some 4mm chain I'll save it for you. Lots of it used to be used for the chain pulls for toilets with overhead cisterns. Yes, lavvy chain.

 

[vyv_cox]

Goodness knows what goes on in your mind, you seem to rattle about looking for people to disagree with on the grounds of your own brand of voodoo science.

You say there is no empirical evidence, but down the years mariners have relied on heavy chain to help anchor setting, most still do - You ignore it.

We know that the use of rope with a chain leader is universal, it helps anchor setting. Empirical evidence - You ignore it


I quote an reasonable external source to outline the almost universally accepted explanation:

"The benefit of this catenary action is that it decreases the initial angle between the seafloor or ocean bed and the anchor rode. "

First you seem not to have read it, then seem to think it is my invention (despite being in italics and quotation marks) then you flounder again 12 hours later:
"Please explain why you think this is relevant as I can see no explanation" Read the above, in bold, italic with quotation marks, taken from my post 29


You say there is no hard data to tell us if the effect is great or small - Your perverse position is: there is no data so we can safely ignore it.


You say the popularity of substantial chain means little in science, I agree. But it does demonstrate how the average boatowner thinks, given a free choice. For years you have been telling us how many people love modern boat design, how many people buy in mast furling, how popular bow thrusters are, how folk have embraced sail drives. - Yet on this occasion - it can be ignored.


You constantly embroider and misrepresent my posts. You tell us that my central claim is:

" - that chain failure can be avoided by having heavier chain"

Lets look at what I actually said:

"* If you neglect a chain you can afford to do it longer and more safely with larger diameter chain"

You increase your safety margin that's all. It's actually irrelevant if the failure mode is by neglect, manufacturing defect, or snatch loads on a fouled anchor.


I have no idea why you rely on flights of fancy, there are good, solid factual reasons for the OP to compromise with 6mm chain. Until it is proven other wise, anchoring performance is not one of them.

.

'We know that the use of rope with a chain leader is universal, it helps anchor setting. Empirical evidence - You ignore it'

Most people use a short length of chain for wear resistance, not to aid setting. In fact Fortress recommend that rope be attached directly to the anchor without chain for optimum setting. I doubt very much that a 5 metre length of 8 mm chain would have the slightest influence on setting.

 

[doug748]

..extensive published data and just rely on what people have always done.

.... It is all documented and in the public domain.

Your claim that heavier chain helps better setting is simply not true. What sets anchors is the load applied not the weight of the chain. Watch any of the videos of anchors setting and you will see the chain lifting from the bottom before it moves the anchor. The angle of pull is determined by the scope - that is the more rode out in relation to the depth the lower the angle of pull. I read what that source of the diagram said and the diagram proves nothing and the sketchy explanation is just wrong. All it says is what it says - nothing about aiding setting of the anchor. That is your invention.

I did not say that the popularity of substantial chain means little in science. What I said is that science and empirical data based on it does not support the need for heavy chain. The use of heavy chain (and heavy anchors) long predates any serious scientific work and is embedded by for example the unchanged recommendations from various sources. The work on anchors and anchor design over the last 20 years has disproved most of the long held views on the subject.

I have never said to ignore catenary. All I have said is that there is no data that measures what it does nor what the difference is between different weights of chain in use. How can you make a rational decision about buying heavier chain than necessary if you don't know what additional benefit it brings?

I do not know why you continue to talk about the loss of strength due to corrosion as a reason for buying heavier chain. Why would any one do that? The safety margin of chain, even 6mm is far greater than any boat of the size the OP has could ever generate. That is a fact, and even a 50% loss in strength would still exceed the load the boat could apply.

Your last sentence does not make any sense. There is no need to compromise with 6mm chain. It is more than adequate in terms of strength. It will set his anchor in exactly the same way as heavier chain using the same scope. If you have difficulty with this then read the data on which it is based and the testing work that has been carried out to demonstrate this is so.

There is no conclusive literature otherwise you would not be relying on broad statements backed up by nothing. Flatulent theories and repetition on these pages sums most of it up.

The only solid, recent practical work I have noted has been done by Steve Godwin (as usual). He has explored the matter in a pragmatic way and for most sailors it chimes with their preferences.

Those who want to use undersized anchors and chain, or all rope, can do so. Most sailors I know are looking for margins that work in their favour.

.

 

[lampshuk]

Gosh! I'd forgotten how much the Forum loves an anchor thread.

In case anyone's interested, I did call BGD and spoke to a very helpful gentleman and through discussion concluded that getting 15-20m of new 8mm chain and discarding the worst of the existing chain was probably a pragmatic way forward - driven as much by compatibility with my current anchor and other hardware as anything else. I will probably use 2 of their stronger D Shackles to join the chain lengths rather than a split link.

All I need to do now is actually order it!

Thanks, all, for the energetic and informative discussion.

Lampshuk.

 

[Neeves]

Hey.
My 32 fter had a bulkhead welded in with stiffeners to strengthen deck for Staysail (Cutter Halyard) I had a 1in Divider Marine ply fore and aft. Port side had 6mm x 100m. with 100m 20mm Nylon splices on behind for day and short term Pick use.
Stbd side had a 82lb Admiralty pick with 120mtrs of 8mm SHort(triple b) chain and a deck box for the Nylon.

Well. Maybe soft was the wrong word but H/T Treatment was gone. around 8 galvanisers I know must be wrong too. They all said the same thing when I was regalving over the 70 ish yrs I've been sailing. AND stretching some chains (Mainly lifting heavy loads) Most just get tank to temp. Load. rattle it around then lift it to drain.
Personally, I just bought Triple b Short,galv. Hammerlocks and shackles to suit. Made up several 8ish foot 30mm Nylon snubbers with clear hose over top metre.for stemhead wear. Never had a problem anywhere I went. (42fter I made 40mm Snubbers).
We used H/T Single chains and and wire strops for heavy lifting with the cranes
Nobody I know ever had any problem with triple b chain of correct links for their boat in ANY conditions. and living in Townsville. Douglas and Darwin for 50 plus yrs. We swung to a few good breezes (Cyclones).

Anchoring is a mix of light and/or heavy single pick.
econdly, heavy shackle 40ish ft chain and second pick on front of. Dropped and set first.
third. Two picks dropped 45 to 60deg part .
Two for'ard and one at stern to hold bow into sets/wind if differing lengths on twin pick drop don't work.
Then the three way anchor set on the one riser with swivel, if leaving boat for a while.
Lots of differing ways. MOST of the old school ways do hold. Always have a decent swivel on head of stock on pick.
ALL Picks. Have fun hey.

.

I think you have a steel yacht.

I confess to laziness - most forum members own fibreglass yachts and I comment on that basis. I'd go a bit further than that most forum members have fibre glass yachts that have all the excess weight squeezed out of them by accountants. Nothing wrong with building light - but one of the implications is that weight, or additional unnecessary weight matters. The reason most buy these yachts is because - that's what is available, are well known (their vices and that of the builder are known). Most people don't have the time to maintain a steel yacht, nor a 40 year old fibreglass yacht.

But the suggestion that HT galvanised chain turns to a BBB, or 3G quality when re-galvanised is - rubbish. As a simple example Peerless galvanised G70 is a heat treated versions of their G43 chain, which is an alloy chain, not heat treated. I took a galvanised G80 chain and had it regalvanised - the strength of the single galvanised and double galvanised were similar. Peerless ran similar tests on their G70, based on the G43 feed - and achieved the same results.

I have always said that what works for you is right - but that does not mean there are different practices that might also be right for you (you might have benefitted from longer snubbers).

Galvanising HT chain benefits from application of different galvanising processes. Technology has moved on.

BBB, G3, G30 chain is not heat treated. It would never be defined as high tensile. Re-galvanising 8 times will not impact the strength of the steel - using the chain such that if needs to be regalvanised 8 times (if that is what you mean) will result in some loss to abrasion and corrosion - and that loss with weaken the chain (but the steel specification and metallurgical characteristics will remain the same).

Jonathan

 

[Neeves]

Gosh! I'd forgotten how much the Forum loves an anchor thread.



Lampshuk.

You must have an appalling memory.

Jonathan

 

[Neeves]

There is no conclusive literature otherwise you would not be relying on broad statements backed up by nothing. Flatulent theories and repetition on these pages sums most of it up.

The only solid, recent practical work I have noted has been done by Steve Godwin (as usual). He has explored the matter in a pragmatic way and for most sailors it chimes with their preferences.

Those who want to use undersized anchors and chain, or all rope, can do so. Most sailors I know are looking for margins that work in their favour.

.

Surely you are not serious. Steve was the man who damned Rocna - one of the most popular anchors on yachts over the last few years. When questioned he argued.

Dashew recommended undersized chain and his yachts are hardly 'chicken feed'. But you and Steve know better.

Many people drive Range Rover - offering margins that work in their favour - means absolutely zilch

Jonathan

 

[Neeves]

Jonathan, I spilled my breakfast tea over that one. Bored? It's not me that writes interminable essays, basically saying the same thing.
Anyway, I'll be out of your hair in a day or two. Just getting set for a six week cruise. If I see some 4mm chain I'll save it for you. Lots of it used to be used for the chain pulls for toilets with overhead cisterns. Yes, lavvy chain. Have a great time. We will miss both your earthy humour and practices from times past. It is truly amazing how technology has moved on.

But Norman - repetition is so easy, just copy and paste. No effort required. You complain but you read every post - I know that because your replies are similar, but not the same.

We are away for only a few days, temperatures day time are gorgeous but at night gets down to a chilly 2-4 degrees. It certainly makes off watch a real pleasure at night (and Josephine is suggesting maybe wimps are right to not sail in the winter months).

Jonathan

 

[Macka1706]

But Norman - repetition is so easy, just copy and paste. No effort required. You complain but you read every post - I know that because your replies are similar, but not the same.

We are away for only a few days, temperatures day time are gorgeous but at night gets down to a chilly 2-4 degrees. It certainly makes off watch a real pleasure at night (and Josephine is suggesting maybe wimps are right to not sail in the winter months).

Jonathan

Come over here Johnathon. Our Winter lasts, at most. Around 8 ot 10 weeks 26/28 daytime mostly and maybe hits around 8/10c overnight. Possibly a few colder days in there. Rest of yr goes from 32/36 daytime and a nice Balmy 26ish O,Night. Heaven
If i ever came back there. I'd freeze to death. I can still remember the snow up to the windows in Winter and heating engine sump overnight on my car so I could turn the engine over and drive to work in the morning.('50's to early '70's)
Look at Google Earth and bring up "The Keppell Islands" group. We live on that shoreline up on one of the hills. Pacific Heights.
THAT is the reason I took my family to Aust when I did. For them. Willing to work. It's there. I retired at 49yrs. Was where I wanted to be in life. Cruised ever since. I know quite a few more in same situation.

 

[Tranona]

Not sure why you are posting this. Jonathan is based in Sydney, cruises up and down the East coast and I believe is currently somewhere in the Pacific. It is Norman who lives in Scotland.