Splicing Advice -- Dyneema

[Dockhead]

So I've got myself some 12-strand, single-braid Dyneema, and I need to splice some pieces of it to some Barton Low Friction Rings, and to make some eye splices.

I've read various helpful things on here, and I thought this was particularly good:

http://www.cofc.co.nz/docs/dyneema-s...ing-manual.pdf

So I think I'm just about ready to give it a try. But do I correctly understand that the splice itself is nothing else but the end stuck through the standing part twice, and then stuck up into the hollow rope to bury the end? How does that hold anything? : puzzled :

[Kenomac]

The same way this Chinese finger trap works.

[thinwater]

Originally Posted by Dockhead

So I've got myself some 12-strand, single-braid Dyneema, and I need to splice some pieces of it to some Barton Low Friction Rings, and to make some eye splices.

I've read various helpful things on here, and I thought this was particularly good:

www.cofc.co.nz/docs/dyneema-spectra-splicing-manual.pdf

So I think I'm just about ready to give it a try. But do I correctly understand that the splice itself is nothing else but the end stuck through the standing part twice, and then stuck up into the hollow rope to bury the end? How does that hold anything? : puzzled :

It's even simpler than that. The pass-throughs are ONLY to stabilize the splice against slipping when slack. You can splice just as well with just the bury, stabilizing the splice with lock stitching. I've made splices and had them broken, so I am quite sure of this.

Just ask the vendor:
http://www.samsonrope.com/Documents/...UL2012_WEB.pdf

This is easier to adjust when the fit is critical.

[DefinitelyMe]

Yes it works very well. I used dyneema as a winch cable when i was working on a mooring barge and we spliced it by just burying the end into the standing part, nothing else. The greater the load, the more it grips the inside piece. Just be aware that it will creep when new, so if you're trying to make it up to a very specific length (like when i was using it to make a new baby stay) it can take some doing to get it to the right length when under tension. The two tucks before the bury probably help to minimise the creep but you will still get some, and i'm not sure i really like them as every bend of the rope and separation of the cover strand weakens the rope. The lower the stretch, the more this is important, so for dyneema it's very important. If we ever tied a knot in our winch cables they would break really fast right on the knot, and with a load that was only a fraction of the breaking strain of the line.

[Dockhead]

How very cool! Remarkably easy to do.

[transmitterdan]

Originally Posted by Dockhead

How very cool! Remarkably easy to do.

You must lock stitch the simple splice where you feed the end back inside itself.

A proper Brummel splice benefits from a locking stitch but you don't have to if you don't want. The "coolest" way to make this splice is shown here:

McDonald Brummel | Make a Brummel Eye Splice using McDonald method | Splicing Knots

NOTE: This video only shows the first part. It does not show the bury finishing touch. You can get that pretty much anywhere or it's just obvious.

[Paul Elliott]

Remember to properly taper the buried part. I've heard that a short or non-existent taper can greatly weaken the splice.

[thinwater]

Actually, Dyneema requiring long turns is urban legend dating back to Kevlar. Because Dyneema is both flexible and slippery, it equalizes loads very well.

Don't believe me, check Samson bend radius data. Thimbles, if used, are for abrasion, not strength. It is full strength, eye-to-eye without them, and since it is hard to find thimbles that can really take the load, they are often omitted.

[Seaworthy Lass]

Originally Posted by Dockhead

So I've got myself some 12-strand, single-braid Dyneema, and I need to splice some pieces of it to some Barton Low Friction Rings, and to make some eye splices.

I've read various helpful things on here, and I thought this was particularly good:

http://www.cofc.co.nz/docs/dyneema-s...ing-manual.pdf

So I think I'm just about ready to give it a try. But do I correctly understand that the splice itself is nothing else but the end stuck through the standing part twice, and then stuck up into the hollow rope to bury the end? How does that hold anything? : puzzled :

I haven't used the method described in your link, but a simple long bury works extremely well without any additional tucks, as long as the bury length is adequate (roughly between 64-72 times the diameter of the line). If the bury is given a long smooth taper (¼ - ½ the bury) the splice strength is over 95% of line strength.

The only problem with Dyneema is that it is slippery and if a long bury splice is being loaded and unloaded the tail can slip out in time and it is safer to use some locking stitches. Alternatively splice a locked Brummel instead of a long bury. Your method is similar to a locked Brummel I think , probably eliminating the need for any locking stitch.

The only thing I would recommend is that you calculate the amount of bury required depending on the diameter of the line you are using, than the fixed amount they recommend.

Originally Posted by transmitterdan

You must lock stitch the simple splice where you feed the end back inside itself.

A proper Brummel splice benefits from a locking stitch but you don't have to if you don't want. The "coolest" way to make this splice is shown here:

McDonald Brummel | Make a Brummel Eye Splice using McDonald method | Splicing Knots

NOTE: This video only shows the first part. It does not show the bury finishing touch. You can get that pretty much anywhere or it's just obvious.

This is the method I use, but I don't use a locking stitch with it (I have never heard of the tail shaking loose with a locked Brummel).

Originally Posted by Paul Elliott

Remember to properly taper the buried part. I've heard that a short or non-existent taper can greatly weaken the splice.

Evans Starzinger did some work on this and found that if the end was buried with zero taper the breaking load was 85% of the line and with the end not buried and just sticking out it was around 80%.

It sounds like a big loss, but in practice I think the working loads are usually far from approaching the strength of the line if Dyneema is used, so this probably isn't critical. I am a braces and belt type of gal, so I taper carefully over a long length .

SWL

[Paul Elliott]

Originally Posted by thinwater

Actually, Dyneema requiring long turns is urban legend dating back to Kevlar. Because Dyneema is both flexible and slippery, it equalizes loads very well.

Perhaps, but Evans Starzinger did some testing of the Dyneema buried splice and found that the taper length did indeed affect the breaking strength. Here's a chart from his report:

[Seaworthy Lass]

Originally Posted by Paul Elliott

Perhaps, but Evans Starzinger did some testing of the Dyneema buried splice and found that the taper length did indeed affect the breaking strength.

I think Thinwater was referring to the need for a thimble rather than the need for a long taper? Single braid Dyneema can turn over quite a tight radius and not lose much strength.

[Seaworthy Lass]

Dockhead, just a couple of practical tips:
- Unless you are using very thin line, it will be impossible to thread a darning needle with it. Just use a fid for the whole job. A short fid will still work (it will just bury as you push it along).
- Pushing the Dyneema together (ie compressing its length) as much as possible opens up the centre beautifully and allows the fid to slip through easily without catching any of the strands. Snagging the strands internally apparently weakens the splice.

SWL

[Dockhead]

Wow, thanks to everyone for this wealth of information!

I've had to put this aside for the evening but I will report tomorrow how it all ends up. I'm using a ball point pen rather than a fid, but this seems to working fine. It's easy to open up the structure of the rope (6mm 12 strand single braid is what I'm using).

[thinwater]

Originally Posted by Seaworthy Lass

I think Thinwater was referring to the need for a thimble rather than the need for a long taper? Single braid Dyneema can turn over quite a tight radius and not lose much strength.

Yes, the need for a thimble.

In fact, I provided several splices to Evan (I was doing stuff for Practical Sailor at the same time, but he was focused on splices, whereas I was focused on stitching). Before you get to hung up on the 60x, consider that I supplied samples that had limited chafing (only 2-3% or cross sectional area in one case) with a 25:1 bury and a 5:1 taper, and they broke at the chafe!! Put another way, a properly sized line is NOT going to fail at any splice over 80%. It is going to fail somewhere else, where something rubs. Heck, 45% knots seldom fail. I seriously doubt the OP is working at over 10% BS. It's chafe.

Just sayin', don't take you eye off the ball.

[Seaworthy Lass]

Originally Posted by Dockhead

I'm using a ball point pen rather than a fid, but this seems to working fine. It's easy to open up the structure of the rope (6mm 12 strand single braid is what I'm using).

If you are using a ball point pen then I think you may struggle with step 1 of your method, where the standing end needs to be pushed through doubled up. You would find the 'McDonald Brummel' or simply the 'Brummel used feeding both ends' (a very simple method, just be a bit tedious if your line is very long) easier with a ball point, as only a single bit of line needs feeding through at any stage .

SWL

Edited to add: Looking at it again, you probably don't need a fid or ball point to push the line through in step 1 at all - just enlarge the hole with the ball point, double up the standing end and push it through by hand. Let us know how you get on using a ball point instead of a fid.