The Chain Splice is used when a 3 strand line needs to be directly attached to a chain in a way that does not create a bulge. This is often necessary if an anchor rode is fed in or out of a hold or anchor locker through a narrow opening or through a sharp angle on a windlass.
The chain splice places stress on the line where it rubs against the chain and this spot should be checked occasionally for signs of chafe.
Making a Chain Splice
First you need to make a constrictor knot or bind the rope about a foot from the end. The actual length will depends on your line thickness. It's better to have more than to run short.
Melt the ends and put some tape on each of the 3 ends. It helps to make a tapered tape end.
Mark each of the lines with a number. I put the numbers with a magic marker on the tape.
Unravel the 3 strands up to the constrictor knot and flatten them so that line number 1 is the centre line.
Take line 1 and thread it through the first link of the chain from the top.
Take lines 2 and 3 and thread them through the first link from the bottom to the top on each side of line 1. Line 1 will be in the middle and lines 2 and 3 will be on either side going around the first chain link in opposite directions.
Take number 1 line and go over one strand of the rope and tuck it under and out of the next strand. So over one under one.
Do this for other 2 strands.
Tighten the 3 strands and take a look at them. They should all have gone over and under a strand and should be at the same level. If one is higher then check your over and under strands and re do it. In a way this is the hardest part of the whole thing. Each of the 3 strands of the twisted rope should have a strand sticking out of it.
It will look like you are weaving the strands against the twist of the rope.
Tighten the strands but do not make them too tight. The chain should be able to move easily against the splice so it does not bind when it goes through fittings and windlass.
Keep going around and tucking your ends checking them every turn. Go in the same order you started 1-2-3. After each turn the 3 stands should come out of the rope evenly and each strand of rope should have a strand sticking out from under it. It's hard to see the weaving in a single coloured rope. When you are practicing it is easier to use markers and colour each of the 3 strands a different colour. That way you can easily see the weaving.
When you are thinking of finishing off, cut about a third of the thickness of the rope off and tuck a turn with the thinner strands. Do this again with 2/3 of the strands removed. This will taper your splice nicely. When you are finished cut off the tips leaving about a quarter inch sticking out.
The splice should blend in nicely with the rope with no sudden thickening because of the thinning of the last few inches.
Take a small mallet, a shoe or just your hand and gently tap and even out the splice. Tug it and coax it to make it even and round.
The finished splice should bend easily on the chain and not bind.
You can remove the constrictor knot if you want but its not necessary.
Some rope materials are notorious for not wanting to stay knotted. Polypropylene is particularly bad.Article in All about knots on strong hitches for slippery and difficult rope. Also discusses what makes a knot strong.
email me if you find mistakes, I'll fix them and we'll all benefit: Christine