rope to long link chain elongated splice

[deep denial]

I need to splice rope to chain for my mooring - all chain would be far too heavy and all rope would invite chafe, so I have 3.5 m of chain from the buoy spliced to 2 metres rope along to the strong point on deck. For the past 4 years I have used a back splice to a larger link on the end of the chain - there is no room for a thimble. However this involves a very tight turn for the rope which is a theoretical concern, and on inspecting this year I see that the link which has been bound tightly under the turn is rusting badly, and the fibres of the rope are caught up in the rust and considerably weakened. I don't like it! So I thought I would try an elongated splice. This would involve using long link chain as there is no hope of threading the rope through the short link. But on looking at the dimensions of the long links I wonder if there might be a danger of the splice not holding if the links are too large - could the splice simply slip through. The rope is 28mm three strand, the 11mm chain links have internal dimensions of 64mm x 20mm. Am I worrying over nothing?

Ps after a long and difficult search I did eventually find the perfect chain at http://www.absoluteindustrial.co.uk...chain-grade-80-alloy-steel-yellow-painted-p45

 

[vyv_cox]

I used a long splice as you suggest on my original mooring strop. Instead of one link rusting at one place, about ten links rusted! I now use a back splice with the three strands of the crown knot through the final link.

 

[deep denial]

yes that's what I have had up to now. Apart from the rust I have never really been happy with the sharp bend in the rope

 

[ghostlymoron]

I've always attached my anchor with a back splice onto chain. My mooring is all chain though.

 

[alahol2]

Have you considered multiplait polysteel from buoy to deck?

 

[jdc]

28mm rope is so strong (ave BS 14.6 tonnes for Polyester(1) according to Marlow ropes, so 10x what your boat will pull in a F10) it must be chosen for chafe resistance, so why not let it go through the fairlead? In which case there would be room for a thimble.

Moving on to your actual question however, the preferred splce between chain and rope for an anchor warp is not a normal 3-strand back splice. Having the 3 strands through the chain makes it rather fat and the strands do not lie well and do not distribute the load evenly. The better method, but which requires more skill, is to pass only two of the strands through the chain, laying one back into the place of the third strand, and splicing the reaining strand into the rope in the normal way. This is just as strong since there are still effectively 4 strand thicknesses attached to the chain; indeed tests show it has at least 96% of the strength of the rope itself (3).

Details on how to do it are shown in the rigging handbook https://www.amazon.co.uk/Rigging-Ha...-Traditional/dp/0713669187/ref=dp_ob_title_bk

Ropes do lose their stength when bent around a curve, but 28mm 3-strand has three strands of dia approx 10mm. Putting this round 11mm chain is approx a 1:1 curve. This reduces the BS by about 50% (3) so that's about 7.3 tonnes. For comparison 11mm grade 30 chain(2) has a BS of about 5 tonnes, so I still wouldn't worry!

(1) Please use Polyester not Nylon. Nylon is marginally stronger but stretches much more. You have far to little length for the stretch to be any use at all, but stretch vastly increases chafe, so Nylon chafes much worse. Polysteel is a good alternative to Polyester.

(2) Henderson chain catalogue. Grade 30 is preferred for moorings, although one often uses a bit thinner but higher grade for the anchor.

(3) Evans Starzinger's article on load testing

 

[thinwater]

yes that's what I have had up to now. Apart from the rust I have never really been happy with the sharp bend in the rope

The rope is NOT bending sharply, because it is unlayed. This cuts the diameter by 3 times (JDC explained this). Second, the strands are only carrying 1/2 of the load (6 strands approach the last link--3 on each side), so it is still full-strength.

Counter intuitive, but you are not seeing what you think you are seeing. A backsplice is very safe. Yes, you do need to re-do this every 5 years. But even now, I bet it breaks at the base of the splice, where the stress is actually the greatest.

The best splice, IMO, is the irony splice. Still full strength and MUCH smoother over the windlass. This is also in Toss's book (above--good book).

 

[Daydream believer]

Details on how to do it are shown in the rigging handbook https://www.amazon.co.uk/Rigging-Ha...-Traditional/dp/0713669187/ref=dp_ob_title_bk

Thanks for that link. I was going to parcel that book, with some others, down the sailing club as i thought someone might want it to stick under a table leg.
But now I see it seems to be valued at £ 75-00 I will not be so quick to chuck it

 

[deep denial]

thanks for all. Some food for thought, although I'm not quite sure that I follow all the answers, or the logic! That irony splice looks nice, but £75 is too much for me!

 

[thinwater]

thanks for all. Some food for thought, although I'm not quite sure that I follow all the answers, or the logic! That irony splice looks nice, but £75 is too much for me!

Also #2858 in Ashley's Book of Knots.

https://www.practical-sailor.com/issues/37_75/features/Rope-to-Chain-Splice-Test_12172-1.html