UKC

If the sheath is cut and some of the core strands.

Jesus take the wheel

A couple intact strands of nylon core will be enough to allow you to start an abseil.

and finish?!?!

and doubled over so it can pulled.

In this scenario does it cut whilst already loaded as an abseil? Otherwise you would just isolate it (overhand) and abseil past the knot.

You didn’t specifically say you wanted to survive.

The question should never arise. If you have a partially cut rope tie it off with a bight and pass the knot.

I'd probably go for an overhand on a bight.

I’d read somewhere that an Alpine butterfly knot is ideal for this, and I’d filed it away in my brain, along with a hazy recollection of how to tie one. Maybe it is the ideal knot, but not if I can’t actually remember how to tie one when I need it. I’ll replace it in my brain with the overhand. 

I can't for the life of me see if you're joking or not. Sorry about that ):

Assuming you're not - don't use it - get another rope and abseil on that

On the basis of a somewhat drunken bridge-swinging exercise quite a few years ago, when we realised the main rope was horrifically worn through and decided to test it to destruction, the answer is surprisingly few.  Think it held at three or four strands?

I do not want to know why you are asking...

Well that is a bit reactionary and not very calm and scientific.

I am asking so that I could get an answer and yours is the the most fact based so far so thank you.

so some fag packet maths that might kill you if any of it is wrong.

You weigh 75 Kg, peak force on an abseil is apparently hard to achieve double this so 150Kg / 1.5KN (source, unknown - probably one of those hownot2 videos)

Rope is Mammut 11mm semi-static, breaking strain 32KN , sheath contributes negligible strength

Rope strength is proportional to area (google says so, must be true)

Hence, you could cut 95% of the rope and it would still be safe to abseil on as you only need 4.6% of the rated strength. So if the rope has 20 cores , you could cut 19 and still be safe on 1 core.

Do test this, with a backup, and report back. 

It’s one of those questions where if you have to ask the question, you know the answer.

How much is your life worth?

Reactionary and not very scientific.

Thanks.

Obviously you wont die if you are only 4m off of the ground when you pass the 'cut'.

3 cores. 

An appropriate choice for someone who seems somewhat blasé about risk.

But your OP isn't very scientific either! No details of the cut sheath or the core strands, even how many they are. No context at all - are you retreating after failing on a climb when the rope is damaged and you want to continue? Can you call on others for a rescue? Can you get off another way e.g. over the top of the crag, or is an abseil on the damaged rope the only way off? Or did you damage a rope away from the crag and are now wondering if you can use it? Details, please, for a scientific answer...... thanks!

Edit. And how high up are you?

I hope that you didn't post this 80m above a pounding sea at Gogarth.

I'm very tempted to go to the Stößenseebrücke tomorrow with a retired rope, a backup rope + a sharp knife and report back. Lead falls on the climbing wall have been kind of lacking in excitement lately, my belayer's too good. I'll do some nice bouncy abseils and get back to you with photos; watch this space!

PS what's the best place to upload photos/videos for all to see? 

I would replace "obviously" with "probably" - but you are still in line for a good maiming if it all goes south.

I suspect no one will be able to give you a scientific answer. It’s not something manufacturers would test - they would just tell you to retire / cut the rope. As would most people. Anyway, it would need to be rope specific - different diameters and so on.

At the end of the day, anything beyond superficial sheath damage means the rope is compromised. Abseiling on it would add unnecessary risk to an already risky activity. 

TBF, in the heat (or cold) of the moment, I would have few qualms about abseiling past a nick in the rope that had partially cut the sheath and a few core strands, particularly if tying it out with a knot would cause delay that had its own objective dangers.

But I'm pretty sure I would retire that rope thereafter - perhaps chop it to make a wall rope.

Another consideration is that if the sheath is fully cut, you risk stripping it from the core - particularly if you are using some form of traction device. You probably wouldn't deck (you tied knots in the ends, right?) but the sheath would jam in your device and your mate might have trouble abseiling past the bare core.

In an abseil accident, I reckon you’re most likely to land on your posterior rather than on your feet. Landing on your posterior on the ground from 4m up probably won’t kill you but would probably result in quite a few fractures vertebrae and all that that entails (unless the ground is very soft, eg bog or bushes).

Edit - if the damage is 4m from the end, it’s a total no brainier to chop it. If it was 20m in, you could tie it off as an alternative and abseil past the knot, although it’s a bit of a faff. 

I tested this on a Tower Rescue course once and myself (plus rescue dummy) held on one strand.

Was good fun, and slightly unnerving, tapping through each loaded strand with a knife but it gave me an unshakeable confidence in a well-maintained rope. I even gave the one strand a good bounce and it still held.

slightly mischievously, if the above "peak force when abseiling cannot be achieved as double of static force" is true (and you really have to jump on it to do that) then a single 3mm beal cord could be used if you weighed less than 90Kg. 

Not convinced that I would be first in line to test that as the margin for safety if you are dragging it over a sharp edge is somewhat limited, but thinking about it it does give me more confidence about abbing off of a slightly frayed 11mm rope.

hyper pedantically - if it's 4m from the lower end and you have 4m on the floor, then you won't even get weighted - but we are adding more unknowns onto the original pile of unknowns...

The thinnest cord rated for abseiling (doubled) is 6mm I think - brought out by Petzl recently, think it’s reinforced with something to make it harder wearing. In fact that might be for abseiling with the other strand being a normal rope. As you say, in theory you could abseil on thinner cord. In extremis, I suspect it’s been done for short distances and being very careful with sharp edges. I imagine you’d need to put the dead end through an Italian hitch to control the descent speed. Even then, I’d be amazed if you could abseil in control on less than two strands of 5mm.

Damaged sheath exposing the core to rapid damage would be my concern as well. 

Alpine butterfly would do too. I went for overhand as it basically replicates the EDK used to join two halves (albeit further down the abseil and with the ends joined) , however you need a decently long tail to ensure it doesn't roll through. 

I can attest to hanging on a low stretch 9mm rope by one strand, not climbing but industrial cut snatch  rescue for the comms industry. Pretty old school way of rescuing from quite few years back (changed now) I was doing some cpd with another trainer 

Just tie a knot to isolate it, then learn to abseil past a knot. 

I'd have thought if half the core and sheath were cut in one place that should still easily be strong enough, as long there were no complicating factors like sharp rock edges. As someone pointed out 5mm accessory cord can take body weight and there must be more weight bearing fibres even in a cut rope. Using a classic abseil might actually cause less stress on a weakened rope and avoid jamming the rope in a device?

I remember leading on a single, partially severed, half rope and trying to find a belay before the damaged area reached the belayer, but carrying on anyway if the pitch was longer. Hopefully the length of rope then in the system would have decreased the impact of a leader fall. Fortunately didn't need to test it.

Or even better yet. The OP said it was doubled over to pull through. Set up a retrievable abseil with a carbainer and make sure the shot end is the end you pull on. You'll only ever ab on the full strength bit. Used this technique to bail on a big wall due to coreshot rope

https://www.petzl.com/INT/en/Sport/Multi-pitch-rappelling-with-a-single-rop...

Second picture down 

As a counterpoint to some of the 'hanging from a single thread' stories...

I climbed the Old Man of Stoer with a couple of friends, many years ago. On the approach, the tide was low and we waded across. On our return, it was much higher and we decided to use an in-situ Tyrolean across the channel. On the mainland side, the sheath was totally gone and the core fibres exposed, but intact. Alec came across last and George and I decided it would be amusing to see if we could bounce the rope to dip him in the water. A few loud twangs later, three or four of the fibres had parted and we were hastily urging Alec to complete his traverse in double-quick time.

I guess this illustrates what the sheath does for you in terms of protection from UV and other damage. Obviously the tension in a (bouncing) Tyrolean would be good deal greater than for an abseil.

Yeah. That's standard technique for pull through caving trips.

The best use of a damaged rope I've had is shortening them, perfect for grit crags etc... less rope to pull through and coil, equals more routes in a day! 

Did instructor training on Padua University testing tower (used for testing climbing gear and training courses). They discovered that they could cut strands on a loaded rope one by one and get down to can't remember exactly but lets say 2 or 3 strands before the rope failed. They then wanted to see if this would be the same with a high-impact cutting force, from a falling rock perhaps. So they set up a rig to deliver a high-speed cutting force onto a weighted rope. What they discovered shocked them: despite setting up the impacting blade in such a way that it could cut no deeper than a few strands, the rope failed. They weren't sure what was going on but it seemed to be some form of domino effect.

If the sheath is completely cut it might roll off the core making the strength of the remaining strands irrelevant.

I've held my whole body weight (85kg)on a single 3mm strand of paracord.

It snapped when I bounced on it, sounded like a pistol shot.

So in extremis I'd be "happy" to abb on two strands of a 7 strand rope.

Or even learn to abseil past a knot, before such a scenario arises.

At stanage not worth it. In the Alps or high mountains you may have no choice but to risk it!

All depends on the situation.

Don't worry your abseil will end at some point.

As others have said we need more detail. Is it a charity abseil? Fancy dress?

See last bit of this video; https://www.youtube.com/watch?v=bsEAtIiY_BQ&t=44s

If tying a loop off to isolate leave enough to tie an overhand knot in it too. Then you have a 'solid' loop to clip in to to protect the changeover.

I've abbed in ignorance on a 10mm that got cut around 30% I guess.  Only found out on retrieval or I would have knotted it out

You could do some maths.  ?75% of the strength of 10mm rope is core.  5mm tat has strength X...etc.

My guess is that as 3mm cord will take ?300Kg, it'll be a tiny proportion of the 10mm that's actually needed.

The force is applied in a totally different way in the instance (a vector multiplying the load in the rope)

I'd be asking if a rope damaged like that will run through a device without jamming, and also how you'd be able to prussik up past the damage.

Oh, I'm sure I've read Andy Kirkpatrick say that you can break 2kn micros bounce testing them on aid, but that's obviously on a static system of etriers+micro.

I saw an incident indoor climbing where someone was resting between attempts on the crux of a lead route and didn't notice that the tight rope was rubbing on a sharp hold on an adjacent route.  They took a fair number of falls.

When they lowered off they noticed the sheath and about 1/3 of the core had been cut through.

had to do this once on the W Flank in a chimney with plumbed running water.  a long way down the rope we found the sheath missing and some of the core and it stretched nicely when loaded!  Someone had put a prussik bridging the damaged bit hopefully.  There was a tiny precarious ledge just enough to transfer from the bit above to the bit below the damage.  No option of going back up unfortunately so we said our prayers and used it ...

these things build character,

apparently ..

Eeek!

My answer is similar having once destroyed a rope pulling one car sideways out of undergrowth, very very roughly with another. In reality you need very few core strands to bear bodyweight but if you knew you needed to know that you'd always bypass the problem!

jk

I have done that (in real life), it works, and so I'm able to type this post. 

In reply to the rest of you horrible lot:

If you can't tie our damage and pass a knot in both ascent and descent, don't abseil or jumar! These are basic lifesaving skills, learn them!!!!!

[/shouty rant]

Threads like this really bring home how little I know (and how lucky I've been). I could probably wing some of it on the fly if I had to but I really wouldn't like to.

I'll book myself a course come spring.

3mm cord (tied loop) will catch a small fall let alone hold bodyweight. A younger more curious me tried it once.

<edit> pretty sure it was 2mm cord

Jk

Been thinking a bit more about this. I remember the story that Joe Brown recalled in the "Don Whillans last climb" video, where a climber apparently tested his confidence after a fall by abbing off Dinas Cromlech on a bootstrap anchor ("with only one boot?!" as Whillans replied 😁).

That's all well and good if you really know your onions but if not, such antics are probably best avoided.

So, I would suggest that if you need to ask the question "how risky is this very risky thing?" then the answer for you is probably "too risky for you to try". Well that's my approach anyway.