Author Topic: Data on the blimp knot? (Or suggest a better knot for climbing anchor slings)  (Read 917 times)

PolymathArtisan

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Hi all and a happy new year!

I'm doing a introductory Scottish winter mountaineering course which is difficult, because there isn't much snow or ice in this neck of the words at the moment!). A lot of the anchor building techniques I have learned basically come down to putting a sling around a strong point (a tree or a big rock etc.), tying a stopper knot in the middle of the sling and then tying or clipping in and loading the anchor. Here is a good example: (though the slings I've been using are mostly flat tape/webbing, rather than rope).


(from here)

The trouble is that when loading the anchor - especially if loading it several times, or just very heavily - the knots become very difficult to untie. This is massively compounded in the mountains of Scotland or the Alps because your fingers are often very cold (especially if you're standing around dismanling an anchor and not moving much).

The knot most commonly used for this is the overhand. This surprised me. I thought the overhand was known to jam pretty easily and weaken the rope quite a lot compared with other knots. (but maybe this is hearsay, I can't cite a source off the top of my head). The second choice is the figure of eight, about which I had similar doubts. After that i think people tend to go for a figure 9, a stevedore etc, to increase the dynamism of the anchor.

My thoughts immediately went to the Blimp Knot. (as some of you might remember, I really like the blimp knot) Because of it's Zeppelin-like structure, I presume it's a lot less likely to jam, and so could be easier to undo. If so, does anyone know of any data on the blimp knot that i could use to back up my use of it? (because climbers seem to be slow to adopt new things techniques like that unless there is some decent evidence to back it up).

Or otherwise: can anyone suggest a different knot which might be an improvement on the standard overhand? 

Thanks!

KC

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i'd prefer a wrap_3/pull _2 or little brother wrap_2/pull_1 to put seam bffered from loading as far as possible around to inspectable side/towards loading of host mount. 
.
Knot/seam would take less loading/less jamming, and would use Dbl.Sheet Bend as non-jammer anyway.
>>Would give plenty of 'teepee'/'nose as shown to not bend legs of support too much
>>this gives better strength/efficiency of device usage, but less grip of the forsaken across pull now truer to loading.
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agent_smith

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per PolymathArtisan:

Thanks for your question.
All the answers you seek (and much much more) are at the PACI website (knots page).
Link: http://www.paci.com.au/knots.php

I have had to apply tighter security to my work because of out-of-control stealing my intellectual property.
In the last 12 months, I have issued 12 take-down notices and commenced legal proceedings against commercial operators who have used my IP without permission to generate a profit.

Just fill out the IP application and all should be good.

...

Some quick observations...

You haven't given us a full and proper context for the 'anchor'. What exactly will the 'anchor' be used for?
Is the anchor used for establishing a retrievable abseil system? Or is it for belaying a climber (ie a 'second' climber who is following the 'lead' climber)?

1. Your photo hides the end-to-end joining knot which would be located behind the tree trunk.
What joining knot did you use?

2. The Blimp knot (#582) you refer to is not appropriate for your application and is not required.

3. I find myself agreeing with KC that the standard 'wrap 3 - pull 2' is very effective because it is a multi-directional anchor that is jam resistant. However, this is just a best guess because you haven't provided a proper context/application for the 'anchor'. A 'wrap 3 - pull 2' is effective with both webbing and rope. I personally don't use a #1412 Water knot / Ring bend / Tape knot to crate the join. Believe it or not, a simple #1410 offset water knot (offset overhand bend) is just as effective.

4. I find it interesting that you show a tree - one you are above the tree line, there are no trees! (obviously). Also, a 'big rock' typically exists at the base or the top of a cliff - not part way or half-way up it. More likely scenario is that you would be using a geologic rock feature such as a 'thread' or a chock stone. You would also likely be using wired nuts (eg wired chocks) and maybe hex's. When building an anchor from removable protection devices (eg wired nuts) - a 'cordalette' made from 5mm-7mm diameter high strength accessory cord is best practice.

5. If you are building an anchor for a retrievable abseil system, it is implied that the anchor is sacrificed/abandoned. This means your 'anchor' would be construct from material that can be given up...ie it is cheap and not essential for the rest of the route. Usually this means webbing/tape (not rope/cord).

Dan_Lehman

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Your pictured knotted structure shows no TAILS?!

One could do something similar with bowlines.

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SS369

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If your anchor does not need to be position specific, just tie a multi-wrap sling and clip in around all of the wraps. Use whatever appropriate, easily untied, Bend to form the sling. With this, the anchor load is distributed to all the wraps and should ease the load on the knot.

SS

PolymathArtisan

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Thanks Agent Smith, very good answer! I'll clarify some stuff:

You haven't given us a full and proper context for the 'anchor'. What exactly will the 'anchor' be used for?
Is the anchor used for establishing a retrievable abseil system? Or is it for belaying a climber (ie a 'second' climber who is following the 'lead' climber)?
Either an abseil - retrievable or otherwise - or a belay in principle. I was instruceed in using anchors of this type for both but in practice most likely a belay (because of the reasons you identify in your last point).

1. Your photo hides the end-to-end joining knot which would be located behind the tree trunk.
What joining knot did you use?
It's not my photo, it's from the article I linked (unfortunately I don't have any photos of the actual anchors we were building). We were using pre-made sewn slings (nylon and dyneema, here's an example), so there is no joining knot. The only knot in the system is the one visible in the picture, which I think is mostly meant to shorten the length (circumference) of the sling going around the anchor object (the tree or 'big rock'. This is especially useful in cases where the a big sling is needed to get over the anchor (probably a rock), but a smaller sling would fit better around the area ofthat anchor where the sling will actually sit. (cant find an example picture e
at the moment.

It's this knot which I've been taught to use an overhand for, but of course when the sling is loaded (if the climber takes a fall or the belayer just has to lean on te anchor for any time), the overhand jams up terrible and is very difficult to undo in the middle of the Cairgorms with freezing hands in big gloves!

2. The Blimp knot (#582) you refer to is not appropriate for your application and is not required.

Given the above, I was looking for a stopper-type knot which could replace the overhand in that sitatuation (fulfilling the same role), but not jam (or at least not so easily). I immediately thought of thre Blimp knot. I certainly trust that you of all people would know if it was not appropriate, but could you explain why in a bit more detail please?

3. I find myself agreeing with KC that the standard 'wrap 3 - pull 2' is very effective because it is a multi-directional anchor that is jam resistant. However, this is just a best guess because you haven't provided a proper context/application for the 'anchor'. A 'wrap 3 - pull 2' is effective with both webbing and rope. I personally don't use a #1412 Water knot / Ring bend / Tape knot to crate the join. Believe it or not, a simple #1410 offset water knot (offset overhand bend) is just as effective.

Given that I was originally taught with pre-sewn slings I hadn't learned this one, but having now looked into I agree, looks great! Still, not applicable to my situation above unless one happened to have such an enormous presewn sling that it could be used in the bight as effectively one length (not a circle) and tied.

4. I find it interesting that you show a tree - one you are above the tree line, there are no trees! (obviously). Also, a 'big rock' typically exists at the base or the top of a cliff - not part way or half-way up it. More likely scenario is that you would be using a geologic rock feature such as a 'thread' or a chock stone. You would also likely be using wired nuts (eg wired chocks) and maybe hex's. When building an anchor from removable protection devices (eg wired nuts) - a 'cordalette' made from 5mm-7mm diameter high strength accessory cord is best practice.
True, above the tree line there are not trees! I have limited experience of the Scottish mountaineering whence my problem comes, but I will say that every day we went out we did find several large rocks along slopes. We Were'nt really climbing on 'cliffs' as such, but steep rocky slopes. This kind of terrain can also include large 'spikes' of rock which can also be used for a similar purpose (see for example this video).

You're right, we did also use wires and hexes, and they're great for building anchors, but my question here isn't really about that: I', wondering what the best knot is for the above situatin given that one is building such an anchor as in that situation (with a sewn sling).

5. If you are building an anchor for a retrievable abseil system, it is implied that the anchor is sacrificed/abandoned. This means your 'anchor' would be construct from material that can be given up...ie it is cheap and not essential for the rest of the route. Usually this means webbing/tape (not rope/cord).
True. (Mostly. Have you heard about Andy Kirkpatrick's upcoming book 'Down'? I've heard there's some interesting stuff about ghosting off anchors in there...). Still, I'm interested in using these anchors for belaying mostly, so it would still be useful to know.

Hope that clears things up a bit!

PolymathArtisan

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Your pictured knotted structure shows no TAILS?!
The picture isn't of an anchor I actually built (sorry, haven't got any photos of those I built), I got it from the article I linked to. It's made with rope, but the actual use case is with a pre-sewn sling (like this), so there aren't any tails.

(I realise now the picture is quite misleading. I was tired and a bit rushed when I made the original post; please forgive me. A tree is essentially an 'endless pole' (obviously not actually endless, but for all practical purposes...), so the type of anchor I'm talking about (dropping a sling over a large strong object) would actually be imposible).

One could do something similar with bowlines.
Could you elaborate a bit please?

agent_smith

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Reply from: agent_smith on January 07, 2020, 01:13:06 PM

   
Quote
2. The Blimp knot (#582) you refer to is not appropriate for your application and is not required.

Query from PolymathArtisan:
Quote
Given the above, I was looking for a stopper-type knot which could replace the overhand in that situation (fulfilling the same role), but not jam (or at least not so easily). I immediately thought of the Blimp knot. I certainly trust that you of all people would know if it was not appropriate, but could you explain why in a bit more detail please?

I specifically used the phrase 'not appropriate' because of the amount (ie length) of cord you need to actually tie and form the 'Blimp' knot. The length of cord/webbing you need to actually the form the 'Blimp' not is not insignificant. In many instances, you need all of the remaining residual length of material after its passed around an anchor point (eg tree, or geologic rock feature).
Also, given the nominal load that your anchor is expected to withstand - which is normally one person (or a single falling climbing), jamming of a simple overhand knot or F8 really isn't an issue.
In all the years I have been climbing and building anchors with a 'cordalette' (using 5mm-7mm accessory cord), I have never had any loads to the extent that jamming became an issue.
If you were concerned about jamming, just use an F8. You would need to apply some serious force to get an F8 to jam... and what circumstances would induce such a tremendous force? Presumably you are thinking in terms of a 'factor 2' fall? Even if you attempted to arrest a factor 2 fall - presuming the actual anchor point held - I doubt if an F8 knot would 'weld' and jam.

For building an anchor, I would always recommend accessory cord over webbing.
However, webbing would come in handy for a retrievable abseil or perhaps to 'extend' a runner to reduce the risk of 'protection' being dislodged by rope movement.

The weight of accessory cord compared to the weight of webbing is approximately the same - and so weight really shouldn't be the reason for choosing webbing.
We are talking about building solid and reliable anchors right?
Accessory cord is a superior choice of material.

Pre-sewn webbing slings have their place - but for mountaineering, an open (linear) length of untied webbing would be more versatile.

The 'cordalettes' i use are always accessory cord - and the joining knot of preference is the Zeppelin bend (rather than the usual default #1415 Double fishermans).
The Zeppelin bend is totally jam resistant - which means I can always untie my accessory cord and use it in an alternative way in the even of an emergency. If its tied with a jamming knot such as #1415, you have to live with the fact that it permanently joined and can't be untied.

PolymathArtisan

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Reply from: agent_smith on January 07, 2020, 01:13:06 PM

   
Quote
2. The Blimp knot (#582) you refer to is not appropriate for your application and is not required.

Query from PolymathArtisan:
Quote
Given the above, I was looking for a stopper-type knot which could replace the overhand in that situation (fulfilling the same role), but not jam (or at least not so easily). I immediately thought of the Blimp knot. I certainly trust that you of all people would know if it was not appropriate, but could you explain why in a bit more detail please?

I specifically used the phrase 'not appropriate' because of the amount (ie length) of cord you need to actually tie and form the 'Blimp' knot. The length of cord/webbing you need to actually the form the 'Blimp' not is not insignificant. In many instances, you need all of the remaining residual length of material after its passed around an anchor point (eg tree, or geologic rock feature).
Also, given the nominal load that your anchor is expected to withstand - which is normally one person (or a single falling climbing), jamming of a simple overhand knot or F8 really isn't an issue.
In all the years I have been climbing and building anchors with a 'cordalette' (using 5mm-7mm accessory cord), I have never had any loads to the extent that jamming became an issue.
If you were concerned about jamming, just use an F8. You would need to apply some serious force to get an F8 to jam... and what circumstances would induce such a tremendous force? Presumably you are thinking in terms of a 'factor 2' fall? Even if you attempted to arrest a factor 2 fall - presuming the actual anchor point held - I doubt if an F8 knot would 'weld' and jam.

For building an anchor, I would always recommend accessory cord over webbing.
However, webbing would come in handy for a retrievable abseil or perhaps to 'extend' a runner to reduce the risk of 'protection' being dislodged by rope movement.

The weight of accessory cord compared to the weight of webbing is approximately the same - and so weight really shouldn't be the reason for choosing webbing.
We are talking about building solid and reliable anchors right?
Accessory cord is a superior choice of material.

Pre-sewn webbing slings have their place - but for mountaineering, an open (linear) length of untied webbing would be more versatile.

The 'cordalettes' i use are always accessory cord - and the joining knot of preference is the Zeppelin bend (rather than the usual default #1415 Double fishermans).
The Zeppelin bend is totally jam resistant - which means I can always untie my accessory cord and use it in an alternative way in the even of an emergency. If its tied with a jamming knot such as #1415, you have to live with the fact that it permanently joined and can't be untied.

All very good points, thanks for your time answering. One of the reasons I like this forum is the level of detail and care one can get on a topic. Such attention is rare in any field (especially in the teaching) these days and it's nice to know that in small areas, by reading threads like this, I can really get a handle on the fine detail of technique and equipment.

I'm going to get some more accessory cord for my next trip.  :)

agent_smith

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You might almost be interested a discussion at Mountain Project forum here:
Link: https://www.mountainproject.com/forum/topic/118123835/direct-belay-off-of-series-anchor-variations

With that forum - you get comments/posts from quite diverse range of individuals - and with that comes a huge and noticeable variation in knowledge/subject matter experience.

In my view, the concept of 'rig for rescue' is typically overlooked in the outdoor recreation/adventure world.
What I mean by that is whenever you 'build' (ie install/establish) an anchor for climbing purposes, you should consider the implications of an unplanned event (ie something has gone wrong).
If the lead climber takes fall and is injured, the belay person will be thrust into the role of rescuer.

Therefore, it is logical to build an anchor from the point-of-view of having to potentially perform a rescue.
This is what I mean by the concept of 'rig for rescue'.

Looking at some of the concepts proposed in that mountain project thread - it is obvious that rescue considerations have taken a back seat.

I am also a strong advocate for not using your climbing rope to build the anchor. If you think about it, in a rescue situation, your rope is a crucial resource and you might need every inch of it.
People who routinely build their belay anchor with the climbing rope rob themselves of valuable rope length and; if it become necessary to 'bail' (ie retreat) - you would have to waste valuable time de-rigging to recover the precious rope so you can abseil/rappel to safe ground.

I would also comment that in very long (run-out) pitches - where the distance between 2 belay points is almost the entire length of your available climbing rope - you obviously wouldn't have any spare rope left to build an anchor from your climbing rope! So those who have the default mindset to build their belay anchors using their climbing rope may not have the skillset to think in other ways.

Using a 5.0-7.0mm diameter 'cordalette' is super simple - its cheap and light weight to carry and you can build a solid and reliable anchor without your climbing rope. It is easy to link up and 'equalize' 2 or more points of protection (although true equalization is not really possible - but you can get reasonably close).
 In a multi-pitch route, you would obviously need two (2) 'cordalettes'. The lead climber carries one and the belay person has the other...
Another benefit is that the load focal point (which Americans refer to as the 'master point') of the anchor is 'soft' - not a hard metal carabiner.
In terms of 'rig for rescue' - a 'cordalette' is a superior choice.

EDIT NOTE:
A lot of weight has been given in that thread to this test paper:
Link: http://staff.weber.edu/derekdebruin/fixedpointbelay/Comparison%20of%20Fall%20Forces%20between%20Fixed-Point%20and%20Redirected%20Belays%20in%20Recreational%20Climbing%20Systems.pdf

"In order to get the right answers, you first need to ask the right questions".
You will note an undercurrent of confusion regarding peak loading (peak impact force) using various types of belay systems and devices.
Read through all of the thread and the paper and you will notice the issue is 'static/fixed' belay versus 'dynamic/yielding/movable' belay.
Note how you keep seeing 'fixed/static' belay generating lower peak loads than 'dynamic/yielding/movable' belays?
The real underpinning physics is getting lost in translation...
« Last Edit: January 22, 2020, 12:29:45 AM by agent_smith »