Adustable Spliced Deviation Cord

[Tommy]

Just stumbled across this: https://www.teufelberger.com/en/trex-loopie.html

Import may be difficult, but this is trivial to make up from some 12 braid dyneema for anyone who feels it would be useful for them on e.g. an alpine expedition with deep caves.

Tangential to the use of 5mm sheathed dyneema and AS(s?) Hangers from memory.

 

[JoshW]

Look very similar to whoopie slings in the hammock world.

 

[AlexR]

I’ve been using whoopie slings as adjustable deviations for about 4 years now (self made), they do work well but it’s surprisingly how few times the adjustability actually comes in useful.
Mine are from 4mm dyneema, I do have load testing data somewhere but basically “more than strong enough”.

Their use with AS hangers is a bit limited, unless you spliced an eye into the hanger, but with the “locking” bit of the sling that means your anchor to rope distance is at least 40cm or so, plus the knot. In practice I often want my anchor point closer than that.

EDIT:
Just noticed the linked adjustable sling is a slightly different design to what I use, but the point of minimum distance limitation still stands. The backsplice shown does not reliably prevent the cordage from disappearing into the splice, I’d add a knot as well. Then again the folks at Teufelsberger probably know a lot more about this than I do.

 

[AlexR]

It’s also possible to use a type of soft shackle with AS hangers, though I use them with 6mm concrete screws (like the ones shown below).
5mm dyneema gives an acceptable yield strength in the region of 13kN depending on direction of pull.
They’re a bit of a faff to make though.

 

[Tommy]

I agree Alex about the limitations on minimum length and the back loop not preventing the cord from disappearing, I hven't thought of a better wat of doing it than a knot. You can sometimes use a locking brumell splice and short bury to tidy loose ends depending on what you're making, that won't work here.

Minimum length - I haven't done or seen any testing to know what lengths you can get away with, any recommendations I've seen are around achieveing the full strength of the cord (or as close as possible), hence long burys, but this may not always be necessary...

Anyway, just academic nerdy for me as I barely do any local caving these days, let alone alpine expeds.

Soft shackles are a faff, especially with nice button knots and caringly tapered buries, but if you're not anticipating high loads e.g. horizontal tensioned lines, why not use cord thicker than 5mm and take some shortcuts to bring the faff factor down? Which part connects to the hanger/rope in those soft shackles?

Alternatively buy them online from paraglider manufacturers - check out the variety in their designs, the Kortel one is nice. As a side note they're used in paragliding partly to get around fatigue of aluminium krabs - they can and do break on people in flight, maybe one a year globally, nice single point of failure. As usual the krabs are generally 10-20 years old though...lots of cycling loading vs caving. We just care about saving a few tens of grams because we're weight weenies.

I've somehow posted this in a well off-piste part of the forum, can someone move it to the gear section? Gosh, I've truly become an armchair caver who can't use a computer properly.