Using a prusik when abseiling

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Jasoneye
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Using a prusik when abseiling

Post by Jasoneye » Mon Jul 17, 2017 7:56 pm

There are a number of ways to configure a prusik back-up when abseiling. Each method has both advantages and disadvantages, like many other climbing (and other) practices. With this in mind I thought it a good idea to start a discussion covering these advantages and disadvantages for those of us who don't use a prusik back-up at the moment but are planning on starting.

When I first started using a prusik, I extended my abseil device with a long quick draw made up with screw gates, and clipped a short prusik beneath that. The idea being to keep the two separate.

I found this finicky and changed to a prusik above the abseil device, clipped into the waist band of my harness (this was shortly after Tod Skinner died). I've used this method ever since.

What are other guys using and happy with.
Last edited by Jasoneye on Mon Jul 17, 2017 9:47 pm, edited 1 time in total.

RyanKarate
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Re: Using a prusik when abseiling

Post by RyanKarate » Mon Jul 17, 2017 8:36 pm

Personally I don't like (have tried a few times) using the above the device method. But you need two hands on the rope to abseil. One above on the prusic and one below the device.

Using below the device method your brake hand doubles up as the prusic control hand and therefore frees your other hand for a third limb on the wall for better control over edges, swings, grabbing the rock, etc. Even down climbing/abseiling when the rope is running precariously over sharp edges.

Use a lanyard to extend your device. I use 1 lanyard and 1 locking beaner. Lanyard is halved in my belay loop, going up to the locker with bug. 60cm lanyard gives a comfortable 30cm extension. French prusic below device also clipped to belay loop using another locker. Prusic short and neat. Tie over hand to shorten prusic to right length helps a lot.

Be aware using clip gates - they could be forced open when abseiling over a ledge. Beaner grinds over the edge. Could open or cross load dangerously.

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emile
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Re: Using a prusik when abseiling

Post by emile » Mon Jul 17, 2017 9:35 pm

RyanKarate wrote:
Mon Jul 17, 2017 8:36 pm
Use a lanyard to extend your device. I use 1 lanyard and 1 locking beaner. Lanyard is halved in my belay loop, going up to the locker with bug. 60cm lanyard gives a comfortable 30cm extension. French prusic below device also clipped to belay loop using another locker. Prusic short and neat. Tie over hand to shorten prusic to right length helps a lot.
I also like this method, the extension really makes abseiling a lot more comfortable for me. Only difference is I clip the prussik to the leg loop.

On the discussion around knotted ends and ropes flying around in the wind: I have found it useful to coil the rope and hang it from a long sling below me, it feeds easier from below than from around the neck and I'm also a little paranoid about having so much rope around my neck.

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Re: Using a prusik when abseiling

Post by RyanKarate » Tue Jul 18, 2017 6:30 am

Big advantage for me when clipping the prusic to the belay loop is I can change/switch control hands on the fly quite easily and flip the rope to the other side of me when it gets really awkward.

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Re: Using a prusik when abseiling

Post by mokganjetsi » Tue Jul 18, 2017 6:39 am

What advantage is there to set the prussik above the belay device? Seems like a bad idea to me actually.
If you need to escape the system, carry an additional length of cord with you to set another prussik above the ATC only when needed?

IdratherBeCimbing
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Re: Using a prusik when abseiling

Post by IdratherBeCimbing » Tue Jul 18, 2017 7:27 am

by mokganjetsi » Tue Jul 18, 2017 6:39 am

What advantage is there to set the prussik above the belay device?
If you go read the near death experience abseil thread by Charles from last week it will be easy to see the advantage of a prussik above the device , in the scenario he narrowly escaped abseiling off the end of his rope (no knot in the end ) however if he had a prussik below the device he would not of felt the end of his rope coming dangerously close to the device . the major benefit of placing the prussik above the device is that if you make a colossal F$ck up and do abseil off the end of rope the prussik will catch you and save you life (and while it may seem like some extra effort to use it ultimately would cover you for slightly more situations I think) the major thing remember in this instance would be that the prussik shouldn't be out of your reach as this would make things slightly more difficult if you did want to sit in your harness mid abseil.

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Re: Using a prusik when abseiling

Post by mokganjetsi » Tue Jul 18, 2017 8:47 am

IdratherBeCimbing wrote:
Tue Jul 18, 2017 7:27 am
If you go read the near death experience abseil thread by Charles from last week it will be easy to see the advantage of a prussik above the device
shot for the answer but i do not think it is a valid reason - tying knots at rope's end should be standard practice with deviation only in exceptional circumstances (Charles was strangely fortunate); so I guess my question is "is there any benefit having the prussik above the belay device as a normal course of action?"

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Nic Le Maitre
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Re: Using a prusik when abseiling

Post by Nic Le Maitre » Tue Jul 18, 2017 9:28 am

IdratherBeCimbing wrote:
Tue Jul 18, 2017 7:27 am
the major benefit of placing the prussik above the device is that if you make a colossal F$ck up and do abseil off the end of rope the prussik will catch you and save you life
I've done a fair amount of empirical testing on prusiks grabbing or failing and I'd be hesitant about making that blanket statement without evidence to back it up. Prusiks are finicky things, particularly in dynamic situations. I'm not saying they won't work, I'm just saying there is a good chance they might not.

Abseiling off the end of the rope is prevented by other means, like knots, checking, etc. If it's super windy, or a heinous bushy abseil, then feeding the rope into a backpack and abseiling with the backpack hanging below you works well. Or looping the rope over a sling with loops that get progressively shorter as the reach the top of the pile works well too.

Extension of your device and prusik on your belay loop is safer than on the leg loop. I've seen video of someone being forced upside down by a prusik on their leg loop.
Happy climbing
Nic

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Re: Using a prusik when abseiling

Post by IdratherBeCimbing » Tue Jul 18, 2017 9:57 am

I feel as though this is another one of those red hearings we find so often in the climbing world here there is actually not definitive correct or wrong answer its up to the individual and their discretion ,
by Nic Le Maitre » Tue Jul 18, 2017 9:28 am .I've done a fair amount of empirical testing on prussiks grabbing or failing and I'd be hesitant about making that blanket statement without evidence to back it up. Prussiks are finicky things, particularly in dynamic situations. I'm not saying they won't work, I'm just saying there is a good chance they might not.
my previous post was definitely referencing specifically the incident from last week , you cannot deny that in that particular circumstance the safety would have been vastly increased with a prussik above the device. ultimately though I feel like the topic could go round and round in circles and we all end up giving our opinions but a definitive answer is never found . my opinion is I personally would read the situation and base it off of that but definitely knowing how to execute both methods safely and when to use them would be the best option. a quick google search will show that this topic has been debated many a time on this and other forums.

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Re: Using a prusik when abseiling

Post by Hector » Tue Jul 18, 2017 10:07 am

For cragging days (i.e. one or two abseils) I normally use a French prussic clipped with a screwgate into my legloop, and my abseil device clipped to my belay loop.
For multiple raps (like off a wall) I'll extend the abseil device and clip the prussic to the belay loop. For this setup I've found a PAS works really well: girth hitch the PAS through the harness (legloops & waist belt, not belay loop - Todd Skinner), clip the abseil device within comfortable reach, and have a screwgate clipped to the last loop of the PAS. When you get to the next anchor use this screwgate to clip in hard, then dismantle the abseil device & prussic. For the next rap, rig the abseil device and prussic, weight the rope to test it, then unclip the screwgate from the anchor and clip it to the abseil rope above the device so it doesn't flap around and it reminds you to clip it in first at the next stance. Its good practice to have a second girth hitched PAS or sling for redundancy/flexibility on the stances.
I like the prussic below the device because then the device is taking most of the weight (like it should). Even if the prussic slips a bit it still creates friction through the device.
I've found a French prussic is way easier to manage than a normal prussic which jams up tight and is a nightmare to undo when weighted.

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Re: Using a prusik when abseiling

Post by IdratherBeCimbing » Tue Jul 18, 2017 10:25 am

Infact here is a link to this forum and topic 4 years ago @ Nic Le Maitre viewtopic.php?t=10634 .very interesting to see what everyone's opinions were the and now ( although apparently Charles has always thought safety precautions were just faf)

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Re: Using a prusik when abseiling

Post by mokganjetsi » Tue Jul 18, 2017 10:56 am

Hector wrote:
Tue Jul 18, 2017 10:07 am
(legloops & waist belt, not belay loop - Todd Skinner)
this seems to come up quite a bit - high profile case resulting in over-caution? how many other belay-loop failures have there been?

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Re: Using a prusik when abseiling

Post by BrianG » Tue Jul 18, 2017 1:03 pm

Hector wrote: ↑Tue Jul 18, 2017 10:07 am
(legloops & waist belt, not belay loop - Todd Skinner)
this seems to come up quite a bit - high profile case resulting in over-caution? how many other belay-loop failures have there been?

Thanks for the discussion: instructive to all I'm sure.

I agree with you Willem: however tragic Todd Skinner's accident was, I'm sure a proper inspection of his belay loop (which climbers should be doing on all their kit on a regular basis anyway), would have resulted in him replacing his harness. I also don't buy the thinking that kit should just be replaced because it's getting old but maybe that's a debate for another thread (but to stir the pot :pirat: , I use a 20yr + old harness for the gym. it's had limited outdoor use and has been well looked after by one owner - me. the only reason I don't use it outdoors is it's bloody uncomfortable. I feel totally safe in it).

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Re: Using a prusik when abseiling

Post by Old Smelly » Tue Jul 18, 2017 1:14 pm

I think Hector and Nic have made very good arguments. It is all about applying your knowledge in a given situation to ensure your own safety, but using a set up that you know is reliable is paramount. Whether you rig an extension or use your leg loop the objective of the prussik is to act as a failsafe hand to the belay device, whereas when rigged above the belay device it is there to hold your weight - which is a different application. Doubtless one can use either -as long as you know what you are doing. So once again it is down to good practice and thinking things through clearly.
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Re: Using a prusik when abseiling

Post by Nic Le Maitre » Tue Jul 18, 2017 2:44 pm

BrianG wrote:
Tue Jul 18, 2017 1:03 pm
this seems to come up quite a bit - high profile case resulting in over-caution? how many other belay-loop failures have there been?
AFAIK, Todd is the only confirmed one and from what I understand, his belay loop was damaged/cut through and failed at the cut rather than the bartacking failing.
IdratherBeCimbing wrote:
Tue Jul 18, 2017 9:57 am
my previous post was definitely referencing specifically the incident from last week , you cannot deny that in that particular circumstance the safety would have been vastly increased with a prussik above the device.
Your own personal sense of safety might well have been increased, but in actual fact it might have been a false sense of security as the prusik may or may not have functioned as expected. I'd be hesitant to rely totally on a prusik in that kind of situation. I'd rather check the ropes, put knots at the ends etc.

My choice is extend belay device upwards, French prusik below, also off the belay loop. You just have to watch that the belay device doesn't mind the prusik.
Happy climbing
Nic

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Re: Using a prusik when abseiling

Post by IdratherBeCimbing » Tue Jul 18, 2017 3:47 pm

@ Nic Le Maitre I personally disagree while yes there would still be a possibility of the prussik not catching ,Im not personally going to go and stake my life on the observations of another , perhaps if someone actually went out and properly tested the variables Like prussik chord diameters to rope diameters (on both static and dynamic ropes ) and then set up the system with both configurations ( above and below) and then actually properly analysed (ie put it onto paper and the published it) we might just be a bit closer to a definitive answer but I don't think thats going to happen any time soon. so again I say this debate could go round and round in circles

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Re: Using a prusik when abseiling

Post by RyanKarate » Tue Jul 18, 2017 4:04 pm

Nic, would you be so kind to jot down a few of your findings from -
Nic Le Maitre wrote:
Tue Jul 18, 2017 9:28 am
I've done a fair amount of empirical testing on prusiks grabbing or failing and I'd be hesitant about making that blanket statement without evidence to back it up. Prusiks are finicky things, particularly in dynamic situations. I'm not saying they won't work, I'm just saying there is a good chance they might not.

Even if your findings are just from personal mess abouts/experience - How much should we be trusting a well dressed, sufficiently wrapped, correct diameter ratio, prussik in static and dynmic situations?

Im at peace with trusting them below the device where they will take less of the load and less friction....

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Re: Using a prusik when abseiling

Post by Nic Le Maitre » Tue Jul 18, 2017 5:44 pm



They work well when set properly, wrapped tightly and most importantly, when left alone. The above video shows part of one session of drop testing using normal/3-wrap prusiks (8mm on 11mm) with a 160kg mass. The prusiks were intended to catch the mass when the main line was failed. The belayers knew that it was coming but not exactly when. Overall our catastrophic failure rate (i.e. load would have hit the ground if not caught by a backup fixed line) was around 60% IIRC.

We think that either the belayers minded the prusiks open or dynamic coefficient of friction was not sufficient for the prusiks to bite. Anyway, I'd be hesitant to rely on a prusik above the belay device for two reasons:
1) If you abseil off the end of the rope, you are highly likely to grab rather than let go of the prusik especially since you are already minding it to abseil.
2) The rope moving through the prusik might not be generating enough friction for the prusik to grab.

There are better ways of preventing abseiling off the end of the rope and the other method, prusik below, is, IMO, better and doesn't generate the (potentially) false sense of security that comes with prusik above.
Happy climbing
Nic

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Re: Using a prusik when abseiling

Post by ant » Tue Jul 18, 2017 6:02 pm

Here are two good summaries of the topic with pictures:

http://www.ropelab.com.au/prusik-self-belay-issues/
http://www.chockstone.org/TechTips/RapBackup.htm

What neither quite articulates clearly, is that there are two options when the prussic is BELOW the device:
1) off the legloop - convenient and fine for 1-person loads and quick problem solving*
2) off the belay loop (and device-extension required) for 2-person loads or extended hanging around

The issue with the (1) is that under large load, or lots of moving, the legloop is slowly brought up and sucked into the device causing discomfort or lock-failure.

Ant

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Re: Using a prusik when abseiling

Post by mokganjetsi » Tue Jul 18, 2017 7:09 pm

IdratherBeCimbing wrote:
Tue Jul 18, 2017 3:47 pm
this debate could go round and round in circles
i dunno dude, i have yet to see a single good reason to have the prusik above the belay device; and a bunch of potential negatives. super happy for Snort but that situation was not normal - there will be instances where it could save your bacon but that's only because a (bigger) issue was missed upfront. a bit like escaping a flaming car wreck because you weren't buckled up.

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Re: Using a prusik when abseiling

Post by Old Smelly » Wed Jul 19, 2017 7:41 am

Nice articles ANT (need Ant icon) :thumright
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Re: Using a prusik when abseiling

Post by Q20 » Wed Jul 19, 2017 10:56 pm

All this messing around with prusiks - just get a shunt. :pirat:

It is far more constant than a prusik for abseiling (i.e. its bite does not depend on number of wraps, how old/new prusiks are, thickness etc: so you get very used to how it works.
I extend the belay device 30cm above belay loop (60cm sling doubled through harness) , shunt on belay loop. Once you have used it for a while, you will know just how hard to squeeze the shunt to slide down the rope - no skin abrasion at all. I use left and for shunt and my right hand is well over a metre below my left hand guiding the rope, so even if I went off ends there is a good chance the shunt would catch me (in this configuration it becomes totally second nature to let go of the shunt in anything happens)

Other benefits over prusiks:
Much faster to put on/off the rope the rope
does not slip, jam, or get sucked into belay device
does not squash two ropes together (as in when you tie prusik around two half ropes)
Works better for pulling hard on stuck ropes, z hauling, pulley back ups
Easier for ascending a rope - slides up the rope instead of needing to be pushed
Less wear on ropes (smooth metal vs nylon on nylon)

and you can use it as a safety for climbing with a fixed line (single or double) - but use a second back (ropeman, microtraxion too)

BUT carry prusiks too (for when you need more than one rope-grabbing device) such as passing knots etc
One life, one body. Use them well.

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Re: Using a prusik when abseiling

Post by PeterHS » Thu Jul 20, 2017 9:22 am

Q20 wrote:
Wed Jul 19, 2017 10:56 pm
All this messing around with prusiks - just get a shunt. :pirat:
Thanks to the OP and all above for the many comments, observations and opinions.

Just as there is no 'one size fits all' attitude to risk, together with scenarios that widely differ, it does not surprise that there are many different schools of thought. I always find this useful as it helps me to compare what I do with what others do and to make my own mind up about what's best for me and in situations I find myself in.

Forgive me if I am wrong, Q20 and other, but isn't the risk with a shunt that in times of emergency the human reaction is to grab the device, thereby releasing the grip on the rope, which is the very opposite of what is needed.

But then, is that not likely with a prussic too?

Just my R1 worth,

Ciao,

Peter

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Nic Le Maitre
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Re: Using a prusik when abseiling

Post by Nic Le Maitre » Thu Jul 20, 2017 9:50 am

Q20 wrote:
Wed Jul 19, 2017 10:56 pm
(in this configuration it becomes totally second nature to let go of the shunt in anything happens)
Or use the pull cord, that's what it's there for. Letting go of the shunt is going to require a conscious effort of will to overcome the panic reaction.
Just my 2c.
Happy climbing
Nic

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Re: Using a prusik when abseiling

Post by mokganjetsi » Thu Jul 20, 2017 10:21 am

have been using a shunt for rope-soloing (aad making a knot in the rope when i have a hands-free for a near fail-safe setup). only reason i'm not using a shunt for abbing is the weight & clutter. will need to see how well i can control the rope speed with a shunt as well. but reconsidering its viability :thumright

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Re: Using a prusik when abseiling

Post by Justin » Thu Jul 20, 2017 10:24 am

PeterHS wrote:
Thu Jul 20, 2017 9:22 am
isn't the risk with a shunt that in times of emergency the human reaction is to grab the device...

But then, is that not likely with a prussic too?

Correct you are Peter, newbies/untrained persons (and probably some experienced people) do very often grab tight (usually a reflex motion) when something out of the ordinary happens (this is why I never give an auto locking belay device to a newcomer belaying me for the first time).
Nic is correct in calling for a 'pull cord' - see also the image below (from the Shunt User Manual) on how best to grab the shunt during a descent.

The prusik will be far more forgiving (more friction in play) if you grab it tight (and need to recover). They also twist the rope a fair bit.

I'm strongly considering a shunt at this time.
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Nic Le Maitre
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Re: Using a prusik when abseiling

Post by Nic Le Maitre » Thu Jul 20, 2017 11:18 am

There are a bunch of rope access toys that do the same job more safely than the shunt but unfortunately none of them work on double ropes. There were a number of deaths/injuries attributed to grabbing shunts hence their banning in rope access. All of them were user error. There is nothing wrong with using a shunt, just be very aware of the potential for accidents.
Happy climbing
Nic

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