Rope from cyffty tested

[Cantclimbtom]

However, damage doesn't occur like that. A unicore is safer, but a standard rope will bunch on the central strands.

Yes, it's a bit of a sales-pitch for their unicore ropes!
I hear are stiffer handling and have a reduced durability to general wear and tear, all at a higher price. It's theoretically possible for the pattern of wear, where a sheath could be cut through all the way round, which is actually analogous to being cut down 1 side in a line approx 50% longer than the diameter (due to the diagonal weave of the sheath). It's unlikely but abrasion over a really nasty edge (sub-optimal rigging!) with bouncing during jumaring.

In that perfect storm of serious misjudgement and unusual misfortune, a sheath might get cut. Clearly it'd bunch on the rope but I wonder just how far someone might fall before that stops them, if there is a big runout/drop below them. Best case scenario would be a sphincter loosening experience, time to get the emergency prussics out. Ascending bare strings above a big drop knowing abrasion is probably continuing would create a lot of brown-adrenaline in the pants

Thankfully this thread is confirmation that good quality ropes are tough!

 

[ChrisB]

In the Beal video, it appears there's only a short length of rope below the cut, and no knot, so the sheath just slides off the end. Perhaps intended to frighten people into buying unicore ropes? It would be interesting to see what happens with a knot. How far would you fall, and how fast would you stop - would there be enough shock loading to break the core?

I've cut loaded ropes when practicing pick-offs, and they didn't fail like that. In that case, however, the caver was attached by a descender, not a jammer, and as the rope elongated there was some transfer of load to the rescuer. I expect the descender vs jammer was the major factor. It's unfortunate that abrasion is more likely to damage the sheath during jumaring than abseiling.

 

[mikem]

The jumar would presumably grip the sheath to core better than most descenders - anyway it's happened to numerous people, usually whilst abseiling, & does apparently provide for quality brown trouser moments!

 

[Fjell]

What I was interested in was a drop test, say FF1. What I have taken from a number of tests on normal rope is that the sheath fails and slides at about 4kN. I got the impression the peak load was below what a straight drop test on rope would be, and also that the core didn’t usually fail. Nor did the jammer. So in other words a FF1 on a jammer was distressing, but it didn’t mean you would die. You might well be stuck. I am thinking more of a rebelay failure.

I have always assumed you fall on the Croll, and it was probable that the top jammer was still there. I have never seen that test anywhere, but it seems an obvious one. You would come up short on the safety link?

What happens if you do it on a unicore rope? Is there a risk of more damage than the non-unicore rope? Can a jammer actually cut a rope? I have had various jammers with pins in to apparently prevent that happening - is that a real thing?

 

[royfellows]

I think a matter worth consideration is the effect of low PH on nylon rope. We all know what the big trip in Parc is notable for, and low PH does go in hand with it. Years ago I had a conversation with Phil Brown about it, and he did admit some concern. I think that this testing has gone some way to aleviating those fears.

 

[mikem]

I thought the pins were to prevent the cam pulling up through the jammer, rather than stop it cutting a rope (although it presumably also has that effect)- the teeth are only on one side, so it wouldn't completely desheath the rope anyway