Optimised spliced loops

[zoidberg]

I'm looking to use one or more spliced loops in Dynice Dux/heat-treated SK75 rather like this one from Colligo Marine's site...

The question is 'What is the optimum bury of the tapered ends within the splice?' I've had offers of '34 x diameter', '50x', and '90x'. Can't all be right, can they? Does anyone here have the definitive, reliable answer?

 

[lw395]

I've done quite a lot of splices in small sizes of dyneema, often the core of 4mm Excel Racing, so roughly 3mm 12 strand?
I don't trust anything buried less than 100mm.
I prefer to bury 150mm, but with the last 30mm progressively tapered away to about 1/4.
I tend to do simple bury-the-end splices, with some stitched through whipping.
I don't think here is any harm in burying more, but possibly no gain?
For some things, on some dyneema, it's useful to bury a lot, like fill the whole rope, to give a round section that does not flatten.
Some splices in dyneema will come undone however much you bury, if there's no locking stitch, whipping or Bummell splice.
Top tip, calibrate how much burying 100mm or whatever shortens the standing part, if you have any interest in getting a strop the right length or two things the same!
So I'd say 33x, or 50x including the taper is normal and works for me.
HTH?

 

[zoidberg]

I've had to dig around, for there was a lot of 'uncertainty' and flannel. This, in response to my very specific query, is the word from Marlow Ropes' Technical Manager, who I consider to be authoritative....

The D12 splice relies on friction so the length of bury is very important, however if there's a Brummel lock in the splice then it won't slip and it'll appear as if a shorter bury is possible. I'll try and answer definitively:

In testing without a Brummel lock we've seen splices that slip and pull out instead of break with buries shorter than around 30 times the rope diameter. I.e. at 30 times there's a risk of slipping. To give us an acceptable margin and some confidence we say in our instructions that the bury should be 50x the diameter even though it's highly likely that 40 would be ok in most applications. We also recommend that the taper be in the last third of the tail and that ideally every strand should end at a different point. In testing a splice like this would normally break at the tip of the tail.

Adding a lock changes things somewhat in that even with a very short tail the splice can't slip, however the failure mode will change with a short tail. Instead of breaking at the tip of the splice the break now occurs at the lock, typically at around 30% lower than the quoted rope strength.

Unless you test ropes to destruction you're unlikely to be aware of this strength reduction. I hope this is helpful.

.... and so do I.

 

[lw395]

Bear in mnd that there's more to it than splices failing due to high loads.
I've had a couple of splices fail at near zero load, e.g. due to a rope flogging in the wind or being shaken about when a dinghy is towed behind a car. So I always lock the splices either with Bummel type splice or a few stitches and a little whipping.
Very few of my lines get above 10% of alleged breaking load, most much less than that. The dyneema is chosen for low stretch rather than breaking load.