Splicing Double Braid Dyneema

[chris95040]

Originally Posted by Kenomac

We have two new jibs, what is the best way to attach the sheet ends? I've always just used bowlines, is there a better way?

I use a single line with a cow hitch in the middle. Bowlines can snag on fwd lowers, etc.

I do recall reading about some shortcoming to this method, but I can't remember what. Cow hitch probably isn't meant to be totally loaded on only one lead, but I've been doing it this way without a problem for decades.

Oh I bet it doesn't work with super slippery stuff. My lines are polyester, sta-set I think.

[Dockhead]

Originally Posted by GrowleyMonster

Have you tried using the instructions for sta-set in the New England Ropes splicing manual?

http://www.wesspur.com/images/pdfs/n...lice-guide.pdf

I am sure that the breaking strength of the eye is quite sufficient. The breaking strength of the core-only eye is nearly as great as doubled core, which is to say, greater than the standing part of the rope. However, I like the cover in place on any double braid rope, for chafe and UV protection. I think if you can manage either of the two methods in the above mentioned manual or the Samson's manual or the German "Schpleissebuch" (I probably butchered the spelling) and lock stitch the throat, maybe serve the splice as well, you will be good to go.

Now the disclaimer... I have not actually spliced Dyneema double braid. Single braid with a brummel type splice, yeah. Nylon double braid up to 12" Samson on ships, yup. Polyester double braid on sailboats, sure. But my opinion on how to splice Dyneema double braid is worth approximately what you paid for it.

The principles are different for dyneema, since the stuff is so slippery.


I'm sitting next to the to-be-repaired dyneema sheet in my salon, and marvelling at the stuff. This new sheet is one size down from the original polyester (14mm vs 16mm) yet almost twice as strong, with a fraction of the stretch. And it seems to weigh less than half -- I can lift the whole coil with one finger. Light as a feather; I believe it will float.

Because it was one size smaller, it wasn't even all that much more expensive than polyester would have been, even though it's good racing grade SK78 dyneema. And it's so pleasant to handle.

Boy, I love this stuff. Next I'm going to change out my main sheet for 12mm racing dyneema from 14mm poly -- that is presently the last piece of major running rigging on the boat which is still polyester.

[SailRedemption]

I will be trying Samson Class 2 eye splice soon for some MLX I have which is a dyneema core line. That's the splice they recommend for those types of rope cordage. I'm good at the Class 1,but haven't tried the 2 yet. It doesn't look that much harder, just very different in the steps.

[GrowleyMonster]

I couldn't let it rest. My google-** was getting rusty and neglected so I did a search and came up with this:

https://www.youtube.com/watch?v=0gkFk8DVsoM

Definitely needs lock stitching and whipping, though. The method looks pretty easy, and if the bury is long enough it should hold.

[UNCIVILIZED]

Here's some info from Samson Ropes on; cover stripping, splicing, & lock stitching --> http://samsonrope.com/Documents/Spli..._Cover_WEB.pdf

[Stumble]

Originally Posted by GrowleyMonster

I couldn't let it rest. My google-** was getting rusty and neglected so I did a search and came up with this:

Definitely needs lock stitching and whipping, though. The method looks pretty easy, and if the bury is long enough it should hold.

Growley,

See how the last bit of core gets jammed up trying to get it to bury. This makes me thínk you are going to have a major stress risor right at that point. Frankly absent some good load testing data I don't think this splice would retain close to maximum strength. It looks good, but mechanically I think it is suspect.

One of the really nice things about dyneema is unlike poly doublebraid it remains splicable after being used. If you are concerned about UV or abrasion damage you can just pull a couple feet of the core out of the cover, cut off the damaged core, and end for end splice a new dyneema leader onto the core.

Basically you can replace just the last couple of feet of the line without needing to replace the entire section. Better, you can do this over and over again pretty much forever until the internal section is damaged some other way.

[Stumble]

Originally Posted by SailRedemption

I will be trying Samson Class 2 eye splice soon for some MLX I have which is a dyneema core line. That's the splice they recommend for those types of rope cordage. I'm good at the Class 1,but haven't tried the 2 yet. It doesn't look that much harder, just very different in the steps.

Class I lines cannot be spliced with Class 2 methods. Class 2 splices swap the load path between the cover and the core as part of the splice, if you do this with Class I lines the first time they are loaded up the cover will herneate due to strength and stretch differences.

[SVNeko]

Originally Posted by Dockhead

The principles are different for dyneema, since the stuff is so slippery.


I'm sitting next to the to-be-repaired dyneema sheet in my salon, and marvelling at the stuff. This new sheet is one size down from the original polyester (14mm vs 16mm) yet almost twice as strong, with a fraction of the stretch. And it seems to weigh less than half -- I can lift the whole coil with one finger. Light as a feather; I believe it will float.

Because it was one size smaller, it wasn't even all that much more expensive than polyester would have been, even though it's good racing grade SK78 dyneema. And it's so pleasant to handle.

Boy, I love this stuff. Next I'm going to change out my main sheet for 12mm racing dyneema from 14mm poly -- that is presently the last piece of major running rigging on the boat which is still polyester.

I take it you are not using a dyneema line with a poly cover. If it is uncovered dyneema, do you plan to do anything different in the handling? Extra winch wraps? Will it stay in the winch jaws? Will clutches grab it adequately?

[Benz]

Originally Posted by GrowleyMonster

I couldn't let it rest. My google-** was getting rusty and neglected so I did a search and came up with this:

Definitely needs lock stitching and whipping, though. The method looks pretty easy, and if the bury is long enough it should hold.

While the video makes this look easy, it is actually really difficult to do. Different degrees of cover tightness (and helix patterns), and different cover materials affect how the splice will go. For instance, a cover with a technora/poly blend (done so that jammers will hold it better) will be far harder, since the technora doesn't like to stretch. If you have a heat-treated-prestretched (a la Dynice DUX or Marlow's MAX) core, the splice is fatter due to the greater amount of material, and thus harder to get into the cover.
Another thing is the bigger diameter line, the more force required to suck in the splice.
It is for these and other reasons I believe that NER and Samson recommend the "flap out" method of dealing with the cover--because burying it is so curmudgeonly.

If anyone who has done these splices has any tips for making them easier, I'd be eternally grateful for them.
Ben
zartmancruising dot com

[Paul L]

Originally Posted by Benz

While the video makes this look easy, it is actually really difficult to do. Different degrees of cover tightness (and helix patterns), and different cover materials affect how the splice will go. For instance, a cover with a technora/poly blend (done so that jammers will hold it better) will be far harder, since the technora doesn't like to stretch. If you have a heat-treated-prestretched (a la Dynice DUX or Marlow's MAX) core, the splice is fatter due to the greater amount of material, and thus harder to get into the cover.
Another thing is the bigger diameter line, the more force required to suck in the splice.
It is for these and other reasons I believe that NER and Samson recommend the "flap out" method of dealing with the cover--because burying it is so curmudgeonly.

If anyone who has done these splices has any tips for making them easier, I'd be eternally grateful for them.
Ben
zartmancruising dot com

Tying off the flap is what I do, using the Brion Toss instructions. It is too much of a battle trying to bury the last cover flap. I think having the cover on the splice is better than the splice shown in the OP. It adds some chafe and UV protection .

[SailRedemption]

Originally Posted by Stumble

Class I lines cannot be spliced with Class 2 methods. Class 2 splices swap the load path between the cover and the core as part of the splice, if you do this with Class I lines the first time they are loaded up the cover will herneate due to strength and stretch differences.

I don't think my comment was understood. I have been splicing class 1 lines (regular poly double braids and the like) with class 1 splices. Being comfortable with that I had to do a few class 2 splices on the MLX I had which is a class 2 type line with a dyneema core.

I pretty much follow Samsons splices via their nice book. I'll. Have to get pictures of my eye splice and whipping when I get to the boat.

[Stumble]

Originally Posted by SailRedemption

I don't think my comment was understood. I have been splicing class 1 lines (regular poly double braids and the like) with class 1 splices. Being comfortable with that I had to do a few class 2 splices on the MLX I had which is a class 2 type line with a dyneema core.

I pretty much follow Samsons splices via their nice book. I'll. Have to get pictures of my eye splice and whipping when I get to the boat.

You are absolutely correct I misread what you had so clearly typed.

[UNCIVILIZED]

Originally Posted by SVNeko

I take it you are not using a dyneema line with a poly cover. If it is uncovered dyneema, do you plan to do anything different in the handling? Extra winch wraps? Will it stay in the winch jaws? Will clutches grab it adequately?

As a general rule, it's best to use covered Dyneema for things like sheets on cruisers. And almost without exception on the bits that'll be on winches or in clutches, since it's just too slippery for them to work well on it reliably. Plus which it has a fairly low melting point, & if/when the loads on it are high, then it's easy to damage it via this route, especially when surging it on winch drums & similar.

By surging, I mean easing it out a couple of inches at a time when it's heavily loaded. As on larger racing boats, earlier on in it's introduction to sailing, Dyneema was being damaged this way, at times even with standard Polyester jackets on it. Thus the "invention" of high tech covers like Ice Floss, etc. Which have Technora, Kevlar, PBO, & other materials that are great at dealing with heat, in their construction.

EDIT: It's definitely worth noting that there are huge differences between both rope brands, & specific ropes made by a manufacturer, as to how tightly woven the line covers are. As well as how tightly the covers grip the dyneema cores. For example some Marlow ropes have incredibly tightly woven covers. Which are great in terms of durability, & for preventing core slippage. But that also make them a huge pain in the ass to splice, as it's very, very tough to pull the core out through the side of the cover. Ditto on feeding it back in.

Dockhead, perhaps you could share your experiences with the different lines you've tried? As I know that some have been a lot more satisfactory than others.

Also, when choosing lines, if you're not well versed in what's available, & the characteristics of each, it pays to talk to professionals about such things. Preferably ones that are familiar with more than just Samson, & New England ropes. Not that said companies don't make good stuff. It's just that there are a few dozen others to choose from as well.

[SVNeko]

Originally Posted by UNCIVILIZED

Plus which it has a fairly low melting point, & if/when the loads on it are high, then it's easy to damage it via this route, especially when surging it on winch drums & similar.

Hmmm strange. I always find it harder to melt the end of a dyneema cored line than a poly one.

[UNCIVILIZED]

Originally Posted by SVNeko

Hmmm strange. I always find it harder to melt the end of a dyneema cored line than a poly one.

" Its melting point is around 130 to 136 °C (266 to 277 °F),[8] and, according to DSM, it is not advisable to use UHMWPE fibers at temperatures exceeding 80 to 100 °C (176 to 212 °F) for long periods of time. It becomes brittle at temperatures below −150 °C (−240 °F).["
https://en.wikipedia.org/wiki/Ultra-...t_polyethylene