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Ab protection when anchor fails ...

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kritter 22 Apr 2017
say I have a french prusik on a doubled over rope I'm abbing down.
and I'm cleaning extenders/pro on the way.
the prusik is there in case I lose control of the descent.
but what if the anchor gives out - is the prusik the appropriate protection against this also?
 DerwentDiluted 22 Apr 2017
In reply to kritter:

The word 'no' springs immediately to mind.

In this scenario, if I'm reading you correctly, protection would be of the, ethereal, angel type.
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kritter 23 Apr 2017
In reply to DerwentDiluted:

this is the Beginners/ Improvers board, right? how about elaborating on that 'no' ?
I should add that only one side of the rope passes through the extenders/pro below.
 olddirtydoggy 23 Apr 2017
In reply to kritter:

If the anchor at the top gives then the whole lot heads south. You would fall. Maybe if it gave at the top and there is still gear placed near to the top then that might hold after the rope grabs it and shock loads the piece.
 Fellover 23 Apr 2017
In reply to kritter:

If the anchor that the rope is attached to fails, then a prusik attached to that rope won't help atall. In general there is no protection against the anchor failing when abbing. Not quite sure how you're in a situation where you have gear clipped to one strand of your ab rope?

Different scenario but you can protect against top anchor failure when being lowered off a (usually sport) route and stripping quickdraws by having a prusik on the rope coming up through the quickdraws from belayer to anchor.
 balmybaldwin 23 Apr 2017
In reply to kritter:

If I understand scenario correctly, it could be of some use, but only in the same manner as before (a substitute for a hand on the dead rope, and only effective if properly engaged). Except this time instead of just keeping you in situ should you let go of the rope, it would have to hold a potentially big fall, and I wouldn't trust it to be effective.

Depending how low you are cleaning the route could make this question academic as you'd deck before the rope could catch you, and of course it would depend how good that next bit of pro is too.

I'm struggling to work out how this situation would occur though except in an emergency in which case stopping to strip gear is unlikely. Soloing perhaps but then you'd have an auto arrest device

kritter 23 Apr 2017
In reply to Fellover:

> having a prusik on the rope coming up through the quickdraws from belayer to anchor.

would the prusik round both strands not behave the same way?

kritter 23 Apr 2017
In reply to balmybaldwin:

yes, it is soloing I have in mind. but apart from less dynamicity no different from having a human belayer below,
and electing to come down by ab instead of lowered.
if the anchor went, the fall would be limited to twice the distance down to the next pro so decking isn't a given, I believe.
3
kritter 23 Apr 2017
In reply to balmybaldwin:
I'd imagined swapping out the arrester for a bug to do both lines but on reflection the arrester could be left in place and the prusik still put round both strands.

on second thoughts, it probably wouldn't do having two rope strands coming into the prusik at different angles, so better to put both in a bug....

the fall is the same as a leader fall as far as I can see.
the issue seems to be whether a prusik will a) survive an F2 fall force b) melt the rope!
Post edited at 01:21
1
 tehmarks 23 Apr 2017
In reply to kritter:

The only way the prusik will help save you if your anchor fails is if you're still high up on the route, caught by gear you haven't yet stripped, and it mitigates against you letting go of the rope when you have your 'oh shit' moment. Generally speaking, if your anchor fails while you're abseiling you're going to have a serious accident. A fatal accident, in all likelihood.
kritter 23 Apr 2017
In reply to tehmarks:

how is this different from a leader fall?
I cannot see that it is.
3
Lusk 23 Apr 2017
In reply to kritter:

To save yourself worrying about all this, just make sure your top anchor is sound.
In reply to kritter:

If you've just climbed up then it's more usual to rig the top anchor & be lowered by your belayer, stripping the 'draws as you descend, rather than abbing. If someone else is going to climb the route after you, you might leave the 'draws in so they can lead the route with 'draws preplaced. The last 'draw might then save you should the top anchor fail. If you are stripping them all & are halfway down & then the top anchor fails, then try to land well & hope for the best! If the top anchor looked dodgy, I would be lowered carefully & leave 'draws in the 2 uppermost bolts to try to protect against anchor failure - a small price to pay for some security/peace of mind. If you are abbing off the anchors on a multipitch sport route, there is precious little you can do to mitigate against anchor failure, but there is no shock loading when abbing, so it shouldn't just snap or pull out. Trusting in situ gear doesn't come naturally to me - how old, how rusty, how well placed etc keeps running through my mind!! I've yet to experience failure, but I try damn hard not to fall, & don't really test the limits of my ability. I'm more confident in trad gear that I have placed to my satisfaction
 balmybaldwin 23 Apr 2017
In reply to kritter:
Sorry deleted my post. I'm getting confused. I still can't work out your position, but I'm fairly sure the fall will have to also take into account the distance between the next bit of pro and the anchor because of the slack created in the rope. As far as I see it the fall is at least the normal leader fall plus at least one rope length form the anchor to the next bit of pro depending on whether you are abbing on one or 2 sides of the rope it's about the amount of slack that becomes available when the anchor fails

If you are descending on 2 ropes through a bug, with pro on one rope below you, and the anchor fails, wouldn't that mean that the bug would be on the wrong side when the rope comes taught on an anchor point below it?

I told you I'm still confused and can't imagine how you get into the situation you describe
Post edited at 01:36
kritter 23 Apr 2017
In reply to balmybaldwin:
the rope to the anchor is irrelevant. I'm still above a piece of pro and I'm prusiked to the rope coming up from the belay.
the bug becomes irrelevant as well.
the issue has to be only the prusik - see above ... F2
Post edited at 01:45
1
kritter 23 Apr 2017
In reply to kritter:

if the prusik was attached above the bug then the prusik would be ineffective if the rope slipped through and ran into the bug.
so it would have to be leg loop attached.
In reply to kritter:

How were you planning on arresting any fall you had while soloing up and clipping bolts? I can see how you are hoping the prusik might save you if anchor failure occurs on descent (ie fall to & below the next 'draw, ground anchorage & prusik holding you while rope that was above just falls away). Prusik might be able to withstand that - try simulating it with a big weight. Might it be better with both strands clipped on ascent (as twin ropes)?
 Fellover 23 Apr 2017
In reply to kritter:
> having a prusik on the rope coming up through the quickdraws from belayer to anchor.
> > would the prusik round both strands not behave the same way?

I was talking about being lowered off a route here not abbing. In the lowering off case, it wouldn't make any sense to put a prusik around both strands of rope as they're moving in opposite directions.

In the abbing case, if your top anchor fails and you have removed all the other gear as you go down (like you said you were doing) you will just fall - the rope isn't attached to anything anymore so the prusik won't help. The rope would just pull through the gear that it's still clipped to lower down.

The one scenario I can see where it would help is if you also had the rope anchored at the bottom of the pitch (sorry if I've missed you saying this somewhere), then in which case it would be equivalent to taking a leader fall, but with the link from the rope to your harness being the prusik. This is the same scenario as would happen if the top anchor fails in a lowering off scenario with a prusik around the 'up' rope that I was talking about before.

As to whether a prusik linking rope and harness can cope with a leader fall, probably yes. Most 5mm cord breaks at about about 5kN I think, you have two strands in the prusik so get 10kN, but then the double fishermans knot reduces the strength, I can't remember by how much exactly but lets go for a conservative 50%. I don't know how much the wrapping around the rope in the actual prusik knot reduces the cord strength but I doubt it's as much as 50% and as it's in series with the double fishermans it's a weakest link scenario - only the biggest reduction matters. So we have 10kN x 50% = 5kN which is a breaking strength larger than the force generated at the harness in most leader falls. A lot of ropes will only give an ~8kN force in the UIAA FF 1.7 test, so if it's not a high FF fall you'd probably be fine. Using a 6mm prusik cord would obviously increase the max force it could take.
Post edited at 02:23
 Fellover 23 Apr 2017
In reply to kritter:

> if the prusik was attached above the bug then the prusik would be ineffective if the rope slipped through and ran into the bug. so it would have to be leg loop attached.

If you are going to be in scenario whereby the prusik ends up catching you I'd personally much rather it was on my belay loop than my leg loop...
 John Kelly 23 Apr 2017
In reply to Fellover:

IIRC in a fall (even a quite modest fall) friction between the prusik loop and the rope cuts through the prusik or in extreme examples the rope
In reply to John Kelly:

Not sure if i i misunderstanding this but

Wont you and the prussic be above the piece of gear you are now relying ?

Therefore all that will happen is that you will fall> the prussic will hold> and pull through all the rope going through gear to the ground?

So you will hit the ground but maybe the friction will slow you down... only hope is the route is long enough and youve knotted the end of the rope which catches in first QD.
 John Kelly 23 Apr 2017
In reply to idiotproof (Buxton MC):

Misunderstood
I'm replying to 'fellover' who thinks prusik fail because braking strain exceeded, I think they fail if shock loaded because they slip and the friction generated cuts one of the ropes.
FWIW
I think the original post refers to a rope solo system, too complex to address, David Coley book is good on this
 lithos 23 Apr 2017

as i understand the OP (it has come out of discussion not been clear) the OP is considering lead soloing (an advanced technique) ie rope anchored/fixed at ground, paying out as they go up (using what a mod gri gri ?). Then thread anchor and abs off (to strip gear) and wants to protect the ab against top anchor failure.

what you could do if worried about the top anchor (is actually not ab of and build a better belay!)
with one line fixed at base is...

* make sure there was couple of metres of slack in the fixed line going through the gear
* extend my belay device (bug/atc) with a sling
* clip a hms into belay loop (below bug) and clove hitch on fixed line (or use a gri gri)
* pull fixed line slack through as you go
* swear a lot at the faff

this sounds like a load of faff and potentially dangerous and I do not recommend it at all !

rings a too many alarm bells for me, build a bomb proof anchor to ab off and appreciate the implications of failure
and this is not a beginners technique to be done after watching a youtube video !


 Fellover 23 Apr 2017
In reply to John Kelly:

> IIRC in a fall (even a quite modest fall) friction between the prusik loop and the rope cuts through the prusik or in extreme examples the rope

Maybe, it's a technique I've seen recommended by petzl and I would have thought they would have tested to make sure it didn't have any friction melting problems before recommending it.
 TobyA 23 Apr 2017
In reply to kritter:

Unless you have someone belaying you on both strands of rope and one rope is still through some runners I don't see how the top anchor failing could lead to anything but hitting the floor?
1
 lithos 23 Apr 2017
In reply to TobyA:

rope solo leading.... see my reply above
 Cheese Monkey 23 Apr 2017
In reply to kritter:

If your anchor fails you have messed up or it wasn't an anchor in the first place.
1
 drsdave 23 Apr 2017
In reply to kritter
I'd go for one of these )), VIZ might even be selling them



http://www.theinertia.com/news/alex-honnolds-inflatable-backpack-for-free-s...
 climbwhenready 23 Apr 2017
In reply to kritter:

Let me get this clear, you posted a question to which the answer is obviously "no" in the "Starting out" forum then made out you were lead soloing before quickly leaving the thread.

As this is "Starting out", let's just leave the answer as "no" for anyone who might find it in the future.

A "Rocktalk" level answer would be "No, so build a proper anchor."
kritter 23 Apr 2017
In reply to climbwhenready:

I don't think the answer is a resounding No as you state.
for starters Fellover mentions Petzl having done something like this although there are no details as yet. Others are also not so dismissive.
Many others seem to be certain this is simply a one way ticket to the deck and they are wrong.
the issue is whether a prusik knot will hold a high factor fall as for a lead climber.
I'd love to hear of some testing results regarding that.
1
 springfall2008 23 Apr 2017
In reply to kritter:

You question is very vauge and hence you get a no answer

Please explain your set up, where the ropes are going, the anchors and what type of gear you have and where and you might get a better response!
 PMG 23 Apr 2017
In reply to kritter:
> "the issue is whether a prusik knot will hold a high factor fall as for a lead climber."

No, it is not reliable. Source: Pit Schubert: Sicherheit und Risiko in Fels und Eis (vol. 1)
This conclusion is based on laboratory tests and real life accidents.
Post edited at 21:05
 DerwentDiluted 23 Apr 2017
In reply to kritter:
"The overall findings indicate that even when prusik loops are "properly' tied, set and spaced they have an alarming tendency to catastrophically fail in drop tests under a variety of circumstances'

An eye catching line from one study on prusik loops by Jerome Stiller presented to the International Technical Rescue Symposium, Tucson AZ 2000.
A very interesting read as it address' this very issue, albeit in a rescue rigging situation.
Post edited at 21:08
 Andy Say 23 Apr 2017
In reply to kritter:

I think the answer is still 'no' unless you also have a ground anchor that does not fail. Let's take a sport route as a simple example. You solo it clipping bolts. You arrive at the top anchor to lower off and put a prusik on as protection. Both you and the prusik are above the top bolt so if your top anchor fails you are going to deck it. If your prusik is below the top bolt how exactly are you going to get to the top anchor.
I have soloed a considerable number of sport routes: it is soloing rather than proxy leading
 Fakey Rocks 23 Apr 2017
In reply to drsdave:

What about wing suits... They seem to have copied this off wingachuting.
 Andy Say 23 Apr 2017
In reply to kritter:

> I don't think the answer is a resounding No as you state.for starters Fellover mentions Petzl having done something like this although there are no details as yet. Others are also not so dismissive.Many others seem to be certain this is simply a one way ticket to the deck and they are wrong.

You obviously know the answer, then .

If i understand you at all then I would sack the prusik idea completely and instead clip into a figure of eight knot in the rope. Go down to that knot and then retie, and clip into, another further down etc. You'll fall further but are unlikely to break anything (apart from yourself).

 Fakey Rocks 23 Apr 2017
In reply to kritter:

Just not many beginners jump this far in at the deep end.
+ Your prussik that was set for a downward pull will be now pulled as if to go up the rope, to the anchors end, if that makes any difference in this scenario or not,...
 Fakey Rocks 23 Apr 2017
In reply to kritter:
Is the anchor in this scenario your bottle opener setup....? https://www.ukclimbing.com/forums/t.php?t=657802&v=1#x8491358
Post edited at 22:26
 jkarran 23 Apr 2017
In reply to kritter:

> this is the Beginners/ Improvers board, right? how about elaborating on that 'no' ?I should add that only one side of the rope passes through the extenders/pro below.

Make a scale model if the thought experiment doesn't help.

Long and short of it: don't ab off shit anchors if you don't wish to die abseiling.
Jk
 lithos 23 Apr 2017
In reply to Rock to Fakey:

seeing that thread, maybe that where this has all come from. The OP has seen the petzl dox and expanding it to a failed top anchor. there is precious little info in the OP post, im not convinced its a deliberate troll, but these threads often go off piste.
 stoneback 23 Apr 2017
In reply to kritter:
Get a partner...
kritter 24 Apr 2017
In reply to lithos:

you got me - I'm still agonising over retreating and hit on this prusik idea.
so I wasn't really talking about an anchor but a regular bolt hanger hence my concern with it failing.
so it looks like this idea is about as excellent as the bottle opener one!

thanks everyone for the entertaining feedback. I shall track down one or both of the docs above. I don't know what the petzl doc is that keeps being referred to - just as well though, it might encourage me!
 Fakey Rocks 24 Apr 2017
In reply to kritter:
Perhaps just explain yourself / set up fully first, write it out before posting / get a climber friend / acquaintance (although i guess that's what we all are to all of us) to see if it actually can be understood before posting, to be sure people can give you the best feedback you are seeking, as in both those threads you did, not alot was clear + many guesses were made at what you meant
A bottle opener for example... various shapes + sizes, Some you could break with a hammer? , they may look metalic, but might be some cheap brittle weird composite crap that is only just strong enough to lift a bottle top, .... But perhaps Britool or Snap-on make a bottle opener too, that can also be used as a crowbar, type of strength.... but don't go checking!
Post edited at 09:11
In reply to kritter:

This isn't Zimpara in disguise is it? The prussic will catch the ropes and it will be like a leader fall onto any gear left in only with no second belaying ,the rope will pull through unless by a miracle it tangles and catches in a low piece of gear. Another miracle would be to hope this low piece was a peg or bolt as the upward pull would probably lift a nut out.
kritter 24 Apr 2017
In reply to freelunchprovider:

zimpara? I guess that is an insult.
as I stated in my opening post, pro is collected on the way down.
but in specifying a failed anchor I neglected to clarify which one.
so my apologies to all for the lack of clarity.

down below is my belay or bomber ground anchor.
above is the lower-off or single bolt hanger//tat or pro I'm abbing from - which then fails.

freelunchprovider: you say it will catch while others above cite reports of failure and unexpected behaviour of the prusik.

all: are there any. two strand fall arresters on the market in the style of the grigri, eddy or silent partner etc ?
 PMG 24 Apr 2017
In reply to Rock to Fakey:

Let's hope that the whole thread is just phantasy, a purely intellectual exercise with no links to reality whatsoever.
 springfall2008 24 Apr 2017
In reply to kritter:

Okay, so if you are being lowered off or have the other end of the rope tied down then the prussik might (or might not) work, so it's better to have than not have it. That said, unless I felt the abseil was risky and there was no alternative I wouldn't bother. If I was really concerned I might just leave another piece of gear as a backup rather than depending on my prussik, but you may feel differently.
 Fakey Rocks 24 Apr 2017
In reply to springfall2008:
Like with the prusik, surely any fall arrester is oriented for you to weight it with the top piece of gear holding?
If the top gear fails, the prussik, / fall arrester, eg shunt, is now heading up the rope, because the upper rope section comes / falls down as you fall, so you are now heading downwards to what was the top ends of the rope that were above you... The fall arrester wasn't meant to hold a fall in that direction.... It is now sliding up the rope, but will jam (might break) the anchor gear / crabs, as we now know the rope is also anchored below you, so you take a lead fall sliding down to the top ends, you may deck if low down the route when top anchor fails.

You should Google rope soloing on usa forums, they do more over there, they post their setups.
Post edited at 21:56
 springfall2008 24 Apr 2017
In reply to Rock to Fakey:

Using a Prussik is a recommended way to lower off a sports route if you don't make the anchor??
In reply to PMG:

> Let's hope that the whole thread is just phantasy, a purely intellectual exercise with no links to reality whatsoever.

A voice of sanity. If the main abseil anchor fails (on a real abseil), you're dead or very seriously injured unless you're incredibly lucky. Sometimes you might be saved by some freak of nature or physics (cf. a whole book I've written around a comparable freak.)
 Fakey Rocks 24 Apr 2017
In reply to springfall2008:

Don't think so?! How? People use bail biners. S'pose you could clip to your top bolt, thread rope through it if its a staple, lower / ab off staple, but if its a hanger, thread prussik through hanger, ab off prussik, but i wouldn't fancy abbing off a prusik threaded in a hanger.
 springfall2008 25 Apr 2017
In reply to Rock to Fakey:

There's some links out there, it's when you join the two halves of the rope together with a prussik to catch an anchor failure:

http://www.ascenttraining.co.uk/wp-content/uploads/2013/08/Lowering-of-a-si...
 jimtitt 25 Apr 2017
In reply to kritter:

No-one to my knowledge has tested Prusiks on two strands when only one is in tension, personally I would never rely 100% on a single Prusik locking consistently anyway.
It is also going to be impractical in real life (overhanging routes) to abseil on both strands as you need a fair amount of extra slack in the anchored rope to be able to descend and can´ t get in to strip the gear.
In your scenario everyone abseils on one strand anyway and could use the Petzl idea, not that I´ ve ever seen anyone bother. The doubt about using a Prusik in this manner is you have to hold it to disable it when descending and then let go at the moment of failure and regrettably the normal reaction is to grip the rope (and Prusik) instead.
If the anchor/bolt is really that bad then anyone sensible leaves another karabiner on the next bolt down instead of all this faffing around for an unknown outcome.
 PMG 25 Apr 2017
In reply to springfall2008:

(1) The knot in the Petzl setup is the original Prusik not the French Prusik (see the OP) used in abseiling. (2) It is lowering so the rope is already tensioned meaning shorter fall. (3) It is for added safety only, not to remedy a weak bolt. (If it were the case I would have left a maillon on the next bolt.) (4) The protection is not reliable anyway (it may or may not work).
 lithos 25 Apr 2017
In reply to PMG:

and 7mm cord
 Rick Graham 25 Apr 2017
In reply to lithos:
> and 7mm cord

Tied triple


and only tested by Petzl on a short and small fall factor fall.

fingers crossed symbol required
Post edited at 17:56
 John Kelly 25 Apr 2017
In reply to Rick Graham:

You got a link Rick, cheers john
 Rick Graham 25 Apr 2017
In reply to John Kelly:

> You got a link Rick, cheers john

http://www.ascenttraining.co.uk/wp-content/uploads/2013/08/Lowering-of-a-si...

Here it is from the 2013 petzl handbook , I think.

Does not appear to be on the Petzl site nowadays, they may have had a reconsider.
 John Kelly 26 Apr 2017
In reply to Rick Graham:

Thanks
 Fakey Rocks 26 Apr 2017
In reply to Rick Graham:

They can't spell "off" correctly.
The link doesn't work / download is corrupted.
 John Kelly 26 Apr 2017
In reply to Rock to Fakey:

worked for me
 Fakey Rocks 26 Apr 2017
In reply to John Kelly:

When? Is it still working for you?

I get it downloaded but can't open it with error msg saying its corrupted or damaged.
 springfall2008 26 Apr 2017
In reply to Rock to Fakey:

It works for me, maybe you have an incompatible PDF reader?
 Fakey Rocks 29 Apr 2017
In reply to springfall2008:

Don't know i can download many and only not open the odd one or two, but just had another fail elsewhere, will try update, cheers.

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