Stupid questions about anchor chain

[Lynette]

Callibrated chain ... don\'t think you are right.

We have two 50m lengths of 5/8" chain aboard, one calibrated the other not. The calibrated runs smoothly through our SL Pacific power windlass. The uncalibrated looks identical, and mostly runs OK - but every so often it snags. Then you have to stop and let a bit out again. There must be a difference even if only slight.

 

[Johnjo]

I have a S.L upright manual windlass fitted and use uncalibrated chain
with it, It's in constant use and never had any problems with the chain
riding up or jumping, had problems with the windlass itself, another
story! on my boat with my kit I would replace the chain with one length,
Uncalibrated is not that expensive to buy and the peace of mind it will
give when the wind is blowing will be well worth it IMHO.

mike

 

[mtb]

Re: But

How do you measure the windlass to get the correct chain !!! and is it deemed good enough for the job of perhaps saving the boat when you realy need it , if it's noyt 100% correct.
Danbrit has a great length of new anchor chain I was told that it was the wrong size for the windlass !!! but I will want to check this for my self , if it is the wrong size I'l use the chain to make up another mooring line chuck it in a nice big concrete block and add it to the crane cables , well a bloke has to be sure to be sure ......
Cheers
Mick

http://homepage.ntlworld.com/boats
I need a couple of oak tree's .. for me trawler

 

[Celena]

Re: Link confusion

Where do you get the 25% from? If it's the back splice I read some US test results from a link somewhere that showed about 87% of the strength of the rope!

 

[vyv_cox]

Re: Link confusion

From a post in this thread from jfkal. I'm not claiming anything, and I have seen no evidence that anybody really knows. This subject has been aired here many times but there has never been a definitive answer. I would like to see some testing and I am most willing to participate.

Are you sure you are talking about the same thing? The topic was chain joining links, not splices.

 

[wayneA]

Re: But

Thanks for the post

Good question. The chain that is on runs/holds well, so I will just measure that - now I know how ;-)

THX

Wayne

 

[wayneA]

Re: Link confusion

I would also like to see (participate in) some testing.

Part of the reason for wanting to increase the chain length is that I now sail in the Bristol Channel. With a tidal range of 11 meters+, running at 3 to 4 knots, I would like to be sure that if I had to use it 'in anger', it would stand up to the job!

BTW thx for the posts

Wayne

 

[hylas]

Re: No secret . .

YES I Am.. let's say.. at least for the anchor and absolutly not for the mooring line.. :0)
Just have a look at my "profile".. and you will know (nearly) everything about me.. :0)..

 

[rickwat]

Re: Link confusion

From West Marine Catalogue 2001 - P651- "Connecting Links, Galvanized,heat-treated,drop forged steel. As strong as similar sized Proof Coil chain when rivets are peened into countersunk holes" For3/8in chain they quote Working Load Limit of 2650lbs and for the link 2750lbs. There are a lot of useful figures for chains, shackles, ropes and other types of connectors.

Rick

 

[hylas]

Re: SAFETY - Please believe me..

Please, never use a C link for joining two pieces of chain..
I don't know the adresses of British manufacturers of these connecting links.. but at least have a look at the WEST marine catalogue and I PERFECTLY know the characteristics of these "C" links manufactured in France..
Although you will use one size bigger that the chain (ie: 12 mm C link for a 10 mm Chain) its breaking load is BY FAR much lower than the breaking strenght of the chain..
This is YOUR security and the security of your boat.. and to spare a few tens of Pounds (the cost of a new chain) you will have very HIGH risks..
I'm not a chain manufacturer (nor a manufacturer of C links :0) )

If you use a splice to connect chain and rope, NEVER use a rope to rope splice after a "u" turn in the last chain link.. and ALWAYS a direct rope to chain splice..

 

[wayneA]

Re: SAFETY - Please believe me..

Hylas

Thx for your posts.

In an earlier post you suggested that 25 meters of chain with a nylon warp would be long enough. As most of my experience has been with all chain, I'd be most interested in your views, considering the conditions of the Bristol Channel as mentioned in my earlier post.

Thx again

Wayne

 

[ronniewood]

The only way to guarantee a welded link is to find a chain manufacturer or distributor with a flash butt welding machine. This melts and reforms the link material under pressure - like an old fashioned blacksmiths weld.

To find one you could try A1 Welders in Inverness who specialise in making the welding machines and they may know of one in your area.

Galvafroid is o.k. if regularly checked and touched up but still nowhere as good as hot dip galvanising.

 

[vyv_cox]

Re: SAFETY - Please believe me..

I'm sure you have a great deal of good experience to support your statements. However, the West Marine website clearly says that the C-link, when assembled correctly, is as strong as the chain. I have used them for at least ten years now and, although I cannot claim to have tested one in extremis, I have certainly not had one fail. So, rather than simply asking us to believe you, what evidence do you have that these devices are unsafe?

Vyv

 

[hylas]

Re: SAFETY - believe me..

It's simply a question of "bon sens"..

The Breaking Load Limit of a chain is related to two points :
1º the characteristic of the metal used
2º the diameter of each chain link

look carefully at those "c" links: I don't have info about the metal used, but I can suppose that it is about the same than the one used to manufacture the chain.. and therefor it should have the same resistance.. (daN /mm2)
Now, when the "C" link is assembled, there are at least four parts where the diameter is only half of the general diameter..
How would it be possible to achieve the same resistance with only half of the diameter...
It would be interesting to have PBO making tests of all these "connecting stuff" "C" links, swivels, including rope to chain splices...

 

[hylas]

Re: chain versus Wrap

Sorry I don't have any experience of the Bristol Channel but I don't think it should be very different taht the places I've been anchoring..

I already gave my opinion about comparison between chain and rope.. please find them again...

The main and ONLY advantage of the chain is that it is the only and perfect mean to avoid shaffing of the anchoring rode on agressive sea beds...

Except this point, chain has all disadvantages..:
Stored in the bow chain locker, it ad an heavy weight where it should not be
- Chain is working on the opposite it should work:
o with light wind, it give a perfect horizontal pull to the anchor and the best holding
o with moderate wind, its weight and catenary effect give a perfect shock absorbing effect.
o As the wind build up, the chain will become more straight (and this with as few as 25/30 knots of wind) then the pulling angle will increase and as a consequence, the holding of the anchor will decrease.
o When the shock absorbing effect will be necessary, the "bar tight" chain will not give it any more..

If there will be some waves entering the mooring place, the resulting shocks will be then directly transfered to the anchor, which then has more chance to break free.. and more serious, the chain is subject to high "picks" of pulling force and has very high risks of breaking..

Which lenght of chain??

During the last seven and half months, I spent 129 days moored (out of 228) into 61 different moorings. The mean water height has been 6.50 metres and the scope 5/1. The total lenght of the mooring line was about 30 meters for which 23.5 metres has been lying on the bottom (30 - 6.50 m)
Therefor, I believe a lenght of about 25 meters will be perfect.. If the water height is less, then you will be anchoring with an all chain line.. if the wind build up.. you will give more lenght but the wind will push the boat and the rope line will not shafe on the bottom..

Which length of anchoring rode??

Holding is in direct relation with the pulling lenght of the rode.. (or better, the pulling angle).
Generaly speaking, with a scope of 4/1 you will have about 55 % of the maximum holding of the anchor, with a scope of 6/1 about 70 % with a scope of 8/1: 80 % and with 10/1 about 85 % the maximum. - 100 % holding will be achieved with an horizontal rode or a "Infinite/ 1" scope.
Increasing the scope will be efficient up to 10/1 - With more than 10/1, a large increase of the scope will only give a negligeable increase of the holding... Therefor, the total lenght of the mooring line has to be adapted in relation with the conditions you are expecting to meet and should be about ten times the water height you will have to anchor in.. (I suggest 100 meters)

What to use with the chain??

Natural fibers are no longer used.. out of "Chemical" fibers, the one which has the best elasticity (shock absorbing effect) is polyamide (Nylon, Perlon, Enkalon...).. as the breaking strenght of the 10 mm chain is 5 tons, a 16 mm polyamide line will be well adapted.. (5.6 tons) Don't oversize the rope.. Yes you will increase the strenght but at the same time you will decrease the elasticity.. and "Elasticity" is the secret..

You have the choice of three strands rope or eight strands rope (also called "square line") Eight strands rope is better..

How to connect rope to Chain??

Remember: A CHAIN HAS THE RESISTANCE OF ITS WEAKEST LINK...

a) With an "eye" splice over a thimble and then a shackle on the chain..
ALWAYS use a shackle one size biger than the chain.. and secure the pin with a monel wire.
This is a perfectly safe solution but the eye splice will have difficulties to go throuh the bow roller.. will no pass the windlass gipsy and will never go through the deck pipe...

b) with a rope to chain splice..
Two ways: the wrong one and the right one..
a) NEVER splice the rope over the rope after a "U" turn into the last chain link.. you will loose about half of the rope resistance
b) Make a direct rope to chain splice. This is quite easy to do.. when you know how!!!.. Unfortunately it is not possible to make drawings on this forum, but leave me your E.mail address and I will send you free and personnally, all necessary explanations..

I can spend hours or even days talking about this subject.. giving you looonnnggg mathematical formulas, and if necessary to convince poeple, I will.. This is a complex and highly technical subject and I'm not planning to write pages about it on this forum....

Last point, I'm currently in the LAS PALMAS (Canaria) harbor covering the A.R.C. event.. I had the curiosity to check the mooring line of those boats which will cross the ocean and spend plenty of time anchored in the Caribean.. I was affraid to realise than more than half the float has a dangerous mooring line.. (Not talking about inadequate anchors) Main points are:
A too small, rusted and not secured shackle
The use of "beautifull stainless steel anchor connector" The most common one has an axe drilled to put a "security " screw on the opposite side.. although this is a wonderfull idea to avoid unscrewing of the axe.. the hole in the middle of the axe decrease the strenght. - For a 5 tons chain resistance, this connector has only three tons of resistance.. check yours!!!.
Swivels.. theory is perfect, but under loads, swivels doesn't work.. but more than that, it is important to check their breaking strenght.. ?Not only with a "on line" pull but also with a side way pull..
Connecting links.. they have a breaking strenght of only few hundreds of kilo.. NEVER use them on a mooring line.

What to use to connect the anchor and and the chain??

a shackle is perfect.. as before, always one size bigger than the chain..and secure the pin..
the simplest and perfect way is to use a toggle.. the same you use for your rigging.. and again one size bigger than the chain (12 mm for 10 mm chain)

Well.. anymore question?? :0)

Fair winds and peacefull anchorages..

 

[Jacket]

Re: SAFETY - believe me..

>Now, when the "C" link is assembled, there are at least four parts where the diameter is only half of the general diameter..

It gets worse than that. In two places, the parts which have only half the cross-sectional area of the main links are further weakened by having a hole drilled through them for the rivets, which further reduces the available cross-sectional area. In fact, the holes roughly half the area again, so the links probably only have about 25% of the strength of the chain.

The only way that the links can be the same strength as chain is if the steel used for the links has a failure strength 4 times that of the steel used for the chain. this is not possible. Unless exotic (and very expensive) steel alloys are used, at most, the steel used for the links may be 15-25% stronger than that used for the chain. So this would still mean that the links are 70% weaker than chain.

 

[vyv_cox]

Re: SAFETY - believe me..

I think you are making incorrect assumptions, although I am not making any claims for these links, just trying to find the answers. West's site says that the metal used is heat treated, therefore stronger, whereas chain is always in the annealed condition in my experience, strength about 315 MPa. It is perfectly feasible, without going beyond the bounds of normal engineering steels, to produce these links to be three times the strength of an annealed low-carbon steel, say 900 MPa. I take your point about the thickness, but this would still result in a component 1.5 times stronger than the chain.

Some years ago I carried out a failure analysis on a "Kenter" type link from a marine anchor chain and that was made to a high standard, hardened and tempered. It was much stronger than the chain to which it was attached.

What I can do is to measure the hardness of a link and of some chain. There is a direct comparison between hardness and ultimate tensile strength, so this should at least give some idea. It always seems to me that the main body of the link is hardened although the rivet part is not.

 

[vyv_cox]

Re: SAFETY - believe me..

Actually, the load is not being carried 100% by the rivetted part, but by the C design. It's exactly the same concept as a carabiner. The force is not carried by the screw or latch gate in a carabiner but by the two turns of the metal. The same thing applies to the reduced thickness - it is not a fundamental load-bearing part. The latch, or in the case of the link the rivets, helps to prevent the link from straightening. Because there are two of them per side they are more effective at doing this than the single contact points of a carabiner, so like-for-like the links would be stronger than the carabiners used by climbers, cavers and such people.

 

[Chris_Robb]

Following with Interest!

I have always been nervous about the strenght of these connectors and the nice shiny stainless steel moring swivels.

I think though that I would bottle out in using them, and instead of adding extra chain, I would be inclined to follow Hylas's advice, and halve the amount of chain I carry and add Nylon Warp. His arguements are so compelling that I am going to re look what I do totally. I will save the weight of 50 mtrs of 10mm chain perhaps?

 

[Jacket]

Re: SAFETY - believe me..

Whoops! Ignore half of what I've said. I've just looked at the WEST marine site, and seen the C-links you're talking about. The ones I've seen in the past were a slightly different design, where the rivets were used to carry the load. These definately will only have about 25% of the chains strength
With the WEST marine ones, the case is slightly different.
The C-links rely on bending strenth- they'll fail when the links are pulled straight. Therefore there ultimate strength depends on their yield strength, which will depend on the way the metals treated. In this case, its possible that the links can be as strong as solid chain (though I'd prefer to carry out a few calculations before trusting my yacht to one of them).
Maybe its the fact that there are at least two very different designs for joining links that has lead to all these arguments?