Slings & runners from spliced dyneema rope? (12-strand Amsteel-ish)

In advance -- asking your patience & forgiveness for a kind of an oddball question.

I understand that it may tempt people to reply with some variation on "Why would you bother? Just do what everyone else does -- tie nylon, or buy pro-sewn dyneema webbing." I can't stop you, so fair warning -- that's not really what I'm looking for, here.

Anyway... I recently started learning to splice 12-strand dyneema rope and splice/swage steel wire rope. They're each pretty straightforward, if you can invest $100 in some tools and take a few weeks practicing. Kind of a fun crafty sort of vibe.

Working with this stuff has got me wondering why (12-strand) dyneema rope isn't more popular for climbing slings. We already use plenty of sewn dyneema *webbing* -- which has some caveats and tons of opinions -- but I've rarely heard of climbers using spliced D12 rope to re-sling cams/chocks or make runners.

On the physical merits, D12 rope seems to be a good candidate -- strong AF, durable, UV resistant. For pre-made continuous loops, spliced ropes are just as efficient and reliable as our box-stitched webbing.

It's not good with knots, but is D12 rope any worse than dyneema webbing we already use? (Legit question -- this struck me as a possibility.)

Bend radius is another potential caveat. Flat webbing can be stronger than the same weight of round rope, in a super tight bend. You'd have to watch the sling holes on cams & chocks, so you're not creating a weakness around a sharp corner.

I suspect it might be on account of the lack of splicing knowledge amongst climbers? None of our common gear textiles really lend themselves to easy, reliable splicing techniques. So there's no reason for climbers to get any kind of splicing experience, or own splicing tools, unless we happen to get exposed to it from another source.

Possibly related to that same lack of experience -- maybe climbers don't trust that DIY dyneema splices will hold the weight they're supposed to? Bad splices could kill you, just like bad knots or bad sewing. But splicing isn't black magic -- there are specific procedures and techniques that produce reliable results.

So I guess I'm pondering these possibilities -- and wondering if I'm missing any other reason that spliced D12 wouldn't work as well as the other approaches?

Highliners use spliced hollow braid hmpe quite often in rigs. Soft shackles as connectors, short pig tails to extend backups or backup sections, various different anchor configurations with whoopee slings, loops, eyes etc. 

I think the biggest reason it isn't prevalent in climbing is because there is no/little need as most things that you could DIY splice are readily available from climbing stores. 

However I've also considered splicing my own climbing gear. Whoopee slings as aiders is something that I've found to work well. I've put eyes on the ends of a ~35m length of 2mm dyneema to use as a tagline on rappels. I recently made some short loops of 1/8" technora to use for friction hitches on skinny ropes. BD ultralights use spliced loops covered by plastic instead of swaged cables. Arborists use quite a bit of spliced gear, mostly eyes in double braid ropes though.

Any sling type item would have to be super niche/specific application otherwise I'd just use off the shelf slings. Smileys project on instagram has some posts here and there of spliced gear, I think including some alpine slings.

I'd drop test at least a couple dozen before actually using them. I'd also suggest informing your partner.

4 point whoopee sling highline anchor monstrosity. Not my design. 

1/4" shackle double wrapped as a mainline segment connection for highline webbing. I've moved down to 4mm shackles to reduce the size of the button knot.

Misc soft shackles for highline rigging

Technora loops

Erik J wrote:

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I think the biggest reason it isn't prevalent in climbing is because there is no/little need as most things that you could DIY splice are readily available from climbing stores. 

...

Any sling type item would have to be super niche/specific application otherwise I'd just use off the shelf slings. Smileys project on instagram has some posts here and there of spliced gear, I think including some alpine slings.

Man, those are some NEAT ideas you mentioned, way beyond what I was thinking of... The whoopee sling aider is especially cool!

Re: Need... I don't think there's anything we actually *need* dyneema rope for -- but that's equally true of dyneema webbing. But if there's any job D12 could do better than the existing alternatives, it'd be nice to have the option.

Off the top of my head, I really only have a couple of specific ideas where spliced D12 cord could have a functional advantage over webbing:

 • Slinging hexes & Big Bros with tiny (~1/4") sling holes... The standard approach is a triple fishermans knot in a loop of 6mm tech cord. Which is fine -- but spliced D12 would be stronger (assuming both the knot & splice are done correctly) and less bulky.

 • Double slung cams with smaller-than-thumbloops... I love doubled slings on my cams, but I have some older Tech Friends with smaller sling holes that don't quite have enough room for a double wrap of webbing, sewn or not. Spliced SK99 D12 ~5mm might work, without giving up any strength.

Beyond that... I guess it might be cheaper than paying a re-slinging shop to sewn new webbing loops on cams? But only if your time is free

Ryan Lynch wrote:

Man, those are some NEAT ideas you mentioned, way beyond what I was thinking of... The whoopee sling aider is especially cool!

Re: Need... I don't think there's anything we actually *need* dyneema rope for -- but that's equally true of dyneema webbing. But if there's any job D12 could do better than the existing alternatives, it'd be nice to have the option.

Off the top of my head, I really only have a couple of specific ideas where spliced D12 cord could have a functional advantage over webbing:

 • Slinging hexes & Big Bros with tiny (~1/4") sling holes... The standard approach is a triple fishermans knot in a loop of 6mm tech cord. Which is fine -- but spliced D12 would be stronger (assuming both the knot & splice are done correctly) and less bulky.

 • Double slung cams with smaller-than-thumbloops... I love doubled slings on my cams, but I have some older Tech Friends with smaller sling holes that don't quite have enough room for a double wrap of webbing, sewn or not. Spliced SK99 D12 ~5mm might work, without giving up any strength.

Beyond that... I guess it might be cheaper than paying a re-slinging shop to sewn new webbing loops on cams? But only if your time is free

Cheers. I very much enjoy puttering about with splicing projects and ideas. However I'm very hesitant to implement new or different ideas or techniques to "live" equipment (where failure = death) as I don't have the resources to test the things I make and the ideas I have. Having a break test rig would be sweet.

Reslinging cams or other gear could be an appropriate use case. Would have to be wary of how they hold up over time with abrasion.  D12 sk99 5mm in a loop would be mega overkill for reslinging gear though; theoretically would break at 60+ kn. This pdf, particularly slide 14, might be of interest to you.

Something to consider is is the effect of bend radius on the strength of hmpe hollow braid. The rule of thumb I use - again, check out that pdf - is if the bend radius of the material is tighter than its own diameter then it will lose strength. Conversely, the ability to make super strong slings/items out of thin hmpe may have a negative effect on the gear you are attaching it to. See the classic example of reslinging C4's with skinnier slings or cord reducing the strength of the thumb loop cable. In my case, skinny soft shackles attached to sewn loops on highline webbing causes problems; I can make a 3mm soft shackle that's 35+ kn strong, BUT the sewn loop it is attached to experiences a super tight bend radius around the thin shackle and experiences a significant loss in strength. See this blog post.

I have made:
* spliced eye rabbit runners 120cm long, IIRC 3mm Langman Q1, to me, personally... acceptable strength compared to trad gear single strand, more than strong enough doubled up. I keep one in my chalk bag pocket. - 15g
* spliced eye open cordellette, extra excessively small cord, probably strong enough for weird alpinists, but completely pointless because I can never see myself actually using it
* whoopie sling minimal footloops for ascenders, with soft shackle attachment - 28g
* just general soft shackles
* spliced dyneema with a polyester/technora sheath 5.5mm x 120cm, loop sling... like one of these nice new cord slings, but no sewn connection. Coppa 5000. Was a PITA.

Loop splicing dyneema isn't ideal. Splicing an eye on an end is easier to feel better about. Hollow braid dyneema, technora, etc... its all structural. There is no core with any sort of strength reserve. This is a major downside in things which will see significant abrasion -- friction hitch loops. Sheath + core construction is where its at. Unfortunately, trying to splice a dyneema loop sling and keep a sheath, is pretty difficult. For some sailing double braids the sheath is so tight to the core that it is basically not worth the time or blisters you will get trying to make it happen...Like Marlow Excell Elite... SK99 core, poly/technora sheath. As well, if you forgo the sheath, hollow braid dyneema opens up and snags on things pretty easily compared to conventional dyneema webbing loop slings.

Erik J wrote:

Cheers. I very much enjoy puttering about with splicing projects and ideas. However I'm very hesitant to implement new or different ideas or techniques to "live" equipment (where failure = death) as I don't have the resources to test the things I make and the ideas I have. Having a break test rig would be sweet.

I wouldn't even trust a slow pull test, for cam slings & general purpose runners... Soft shackles whoopee slings, etc seem to get mostly used in sailboat & highline rigging, which seem to involve a lot more steady pulling -- rather than climbing, where we have to worry about very fast, sudden loads during lead falls. I would need to see some drop testing before I took it climbing -- except maybe for aid & rapp use.

The further testing differs from the actual use case, the more opportunities there are for Unknown Unknowns to creep in.

Reslinging cams or other gear could be an appropriate use case. Would have to be wary of how they hold up over time with abrasion.  D12 sk99 5mm in a loop would be mega overkill for reslinging gear though; theoretically would break at 60+ kn. This pdf, particularly slide 14, might be of interest to you.

True, a skinnier line may hold the weight -- but then you'd have to worry more about abrasion and accidental cuts.

I'd consider skinnier cords with some kind of cover -- maybe clear plastic tubing, like on gear slings, to make it easy to inspect.

Something to consider is is the effect of bend radius on the strength of hmpe hollow braid. The rule of thumb I use - again, check out that pdf - is if the bend radius of the material is tighter than its own diameter then it will lose strength. Conversely, the ability to make super strong slings/items out of thin hmpe may have a negative effect on the gear you are attaching it to. See the classic example of reslinging C4's with skinnier slings or cord reducing the strength of the thumb loop cable. In my case, skinny soft shackles attached to sewn loops on highline webbing causes problems; I can make a 3mm soft shackle that's 35+ kn strong, BUT the sewn loop it is attached to experiences a super tight bend radius around the thin shackle and experiences a significant loss in strength. See this blog post.

That's a good point... I don't have any immediate use cases where the bend radius is that small. I don't have many thumb-loops style cams, but I do have a few WC friends that might run into that kind of problem.

Bend radius was a consideration for the two use cases I mentioned... IDK if you have a WC tech friend handy, but the stem ends in a swaged solid steel eye, not a spliced loop. The bend might be a problem, but I think 4-5mm could work. But it needs a drop test to really say for sure.

Big Bros have a pretty generous angle cut in the sling holes, to help increase the bend radius. Nice little design thing that I never noticed until I started thinking about this... Hexes are kind of a crapshoot.

There is version of dyneema where the process increases the strength more than the SK-99, the 3mm has a break strength of around 5000 lbs, the SK-99 around 3500 lbs. New England Ropes and Robline make a single braid version, V.elo uses it  with poly/technora cover, called Dy-tech.

A great splice for dyneema that only requires a fid and a half of bury is Samsons Tuck-Bury splice, compared to the three fids needed for the full bury splice.  Both retain nearly the full break strength of the cord, or rope.

Dyneema tends to flatten, and is stronger when it can. Keeping it round in a tight cover, or u shaped thimble makes it weaker.

I mostly splice hitch cords and the Tuck-Bury makes them stronger and easier to use with covers. The green loop is Beal’s BUL, the splice crossover is centered in the eye, to make the rest flexible enough for friction hitches. Had one tested, static pull, and it broke at a little over one and a half the 12 kN break strength, the end opposite the eye.  I intend to test the Petzl PUR hitch cord to see if it is a guaranteed YGD type situation that is always suggested.

I've used Splices extensively in sailing. It is something I have pondered extensively for climbing. Not so much as a day to day use but for the emergency bail scenario. I think it would be possible to use but you would need to have some for of quality control. 

Brocky wrote:

There is version of dyneema where the process increases the strength more than the SK-99, the 3mm has a break strength of around 5000 lbs, the SK-99 around 3500 lbs. New England Ropes and Robline make a single braid version, V.elo uses it  with poly/technora cover, called Dy-tech

I haven't been able to find any references to a material stronger than sk99. I did find a V.elo product called "Dy-tech" but it's made of sk78.

Do you have a link to any of the products that use it? I couldn't find it on NE or Rob's site, either.

Also, thank you for the pointer about the Samson Tuck-Bury splice... That is WAY cool! Definitely useful for short loops.

It is SK78, but made with a different process.  STS-HSR Heat Set is from NER, sold at West Marine, Robline’s is called Ocean 5000 STS, available at fisheriessupply.

3mm Oceans on the left, NER’s 3mm, and 2mm Ocean, next to a Bic pen used as a fid for tucking

"SK99 Max", etc... different manufacturers have different product names.

I just found this post and wanted to say that I think splicing will probably become more popular as time goes on, as it's a great way to solve all sorts of problems, allowing climbers to make customised components that don't need sewing or bulky knots. I'd highly recommend getting a copy of Seb Constant's book 'Mountain Essentials' as this was the first book I saw that covered splicing and really small dyneema cords. 

Andy Kirkpatrick wrote:

I just found this post and wanted to say that I think splicing will probably become more popular as time goes on, as it's a great way to solve all sorts of problems, allowing climbers to make customised components that don't need sewing or bulky knots. I'd highly recommend getting a copy of Seb Constant's book 'Mountain Essentials' as this was the first book I saw that covered splicing and really small dyneema cords.

Thank you for the book recommendation, Andy -- I'll take a look.

I've been teaching myself splices, the last few months... I also built a backyard break-testing rig from a cheap crane scale and a come-along. It's been really helpful for learning to trust my own work.

Ryan Lynch wrote:

Thank you for the book recommendation, Andy -- I'll take a look.

I've been teaching myself splices, the last few months... I also built a backyard break-testing rig from a cheap crane scale and a come-along. It's been really helpful for learning to trust my own work.

Got any pics or details about the break test rig? I've got a rock exotica enforcer on loan from a buddy's work and want to set something up

Erik J wrote:

Got any pics or details about the break test rig? I've got a rock exotica enforcer on loan from a buddy's work and want to set something up

depending on what your trying to break, you could break the enforcer. They aren't meant for crazy highloads.

a crane scale/load-cell and a chain hoist will get ya where you're trying to go.

Follow @zartman_rigging on instagram to see some of his spliced dyneema slings and quickdraws. UIAA tagged and tested. 

https://www.instagram.com/p/C4_JMn1rTW0/?igsh=MTJld3dmNmJxdzB4dA==

@Erik J ... I don't have any good pics of the whole setup, but it's basically a no-name Chinese digital crane scale and a Vevor cable-puller, strung up between two big trees. The scale is rated to 3,000kg, and the cable puller to ~3,600kg.

For safety, I rigged some weak-link "fuses" out of soft shackles... Each fuse has two SS in parallel -- one shackle is longer and breaks reliably above 3,500kg, while the other is shorter and breaks reliably below 2,500kg. So if I accidentally tension the rig beyond 2500kg, the weaker shackle will break, but the stronger shackle will prevent it from extending more than a few inches.

I also tie Amsteel backup tethers to most of the components, and cover as much of it as possible with heavy moving blankets.

@Mr Rogers ... I use a crane scale, and it's OK for slow-pull testing. But crane scales don't generally have high sampling rates, so the accuracy of their measurements gets worse as you pull faster. I've tried drop-testing with mine, and the results are mostly nonsense.

Ryan Lynch wrote:

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@Mr Rogers ... I use a crane scale, and it's OK for slow-pull testing. But crane scales don't generally have high sampling rates, so the accuracy of their measurements gets worse as you pull faster. I've tried drop-testing with mine, and the results are mostly nonsense.

very well understood. If you're using a chain hoist or any other manual piece of kit.. sampling rate is likely not the issue.

But yes for drop testing you need to up your game.

Andy Kirkpatrick wrote:

I just found this post and wanted to say that I think splicing will probably become more popular as time goes on, as it's a great way to solve all sorts of problems, allowing climbers to make customised components that don't need sewing or bulky knots. I'd highly recommend getting a copy of Seb Constant's book 'Mountain Essentials' as this was the first book I saw that covered splicing and really small dyneema cords. 

Any clarification on which Mountains Essentials by Sebastien Constant? I am guessing Ice, Snow, Mixed Techniques & Strategies?