Author Topic: Relative security of multiple-loop knots  (Read 7175 times)

roo

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Re: Relative security of multiple-loop knots
« Reply #15 on: June 13, 2013, 08:17:47 PM »
   The roo-man does not understand how the bowline works, how the Zeppelin knot works, he does not understand that a not-needed knot tied on a line is a dangerous thing, especially in climbing and boating, bow he does not understand the difference between a hitch and a fixed loop ! He thinks he will change the way ships are tied on the docks, and persuade sailors to stop using the bowline, and start using the slipped buntline hitch ! Oh my KnotGiod ! Watching too much TV does not teaches you many things about the world...I will hire 4 bodyguards ( because I will need them...) and I will go to the harbour first thing in the morning tomorrow, to twll people to use skipped buntline hitches as mooring knots ! Where are you, spirit of Ashley, why you have abandoned me ?  :)
More empty avoidance. ::)

If you'd like to address the content of my posts, I'll be here.  Hopefully we can find a cure to your allergy to hitches. :)
« Last Edit: June 13, 2013, 11:48:08 PM by roo »
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agent_smith

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Re: Relative security of multiple-loop knots
« Reply #16 on: June 21, 2013, 03:04:19 AM »
Some edits herein...

[ ] Added: #1085 (double figure 8 loop) is proven to work in a load sharing anchor configuration - that is, one loop is attached to an anchor point and the second loop attached to the other anchor point. Tests in an Australian facility (near Sydney NSW by B Proctor and R Delaney) demonstrate that when one of the loops is suddenly cut, it does not trigger catastrophic failure of the remaining knot structure. The loops in #1085 can be adjusted to achieve 'equalisation' - Note: Shortening one loop has a corresponding opposite effect on the other loop - meaning the other loop lengthens.

[ ] #1072 is not a practicable solution for building a load sharing anchor

[ ] Here's an interesting one for thought: You can use 'Purcell prusiks' to build a load sharing anchor system. This provides an in-built shock absorber on each leg of the multi-point anchor system. I personally have used Purcells to build load sharing anchors many times over the past few years - it works well. Obviously, you need to have the Purcells pre-tied. Note: Sterling USA make 'bound' prusik loops - these are great tools for climbers (and rope rescue technicians).

[ ] The Bowline is likely the first type of knot used by climbers/mountaineers - you can see photos of Hillary using it on Everest. (Note: They modified it by using a various tactics such as a 'double strangle').

...

roo is correct - ABoK#1047 is the most widely used and relied upon tie-in method in the world of climbing.

The main point is that the rope must be tied directly into the front of the harness - there must be no intermediate connector involved (eg a carabiner).

roo is also correct in his position that there are no recorded deaths due to arbitrary/random failure of #1047. A point worth noting is that EN892 dynamic climbing ropes don't just randomly fail either - in fact, there is not one single instance in the history of rope making where an EN892 rope has failed due to a defect/manufacturing error.

So what causes the deaths then? Answer = human error
(as an exercise, google the so-called 'EDK' knot and also 'tie-in knots for climbing' - the web is full of information and disinformation about knots - hopefully I wont add to the 'disinformation' in my post :) )

Now, here is where the waters get a bit murky:
ABoK #1047 is very secure and stable in all loading profiles encountered in a climbing situation (ie rope is tied directly into the harness - with no intermediate connector).
However, as ropes have become thinner and thinner over time and, as some climbers have gained weight (eg myself!), after a free-fall, ABoK #1047 can be somewhat challenging to untie. Now, with modern sport climbing techniques, multiple repeated free-falls are the norm - several sequential falls can be taken by a climber while 'working' a route - and the climber is generally not lowered back to the ground after each fall. He/she remains hanging in mid-air and then after a brief rest, gets back on the rock and tries again. In this type of scenario, ABoK #1047 can be a real PITA (pain-in-the-arse) to untie - particularly when your fingers and hands in general are 'pumped' and you are maximally fatigued.

This has been the catalyst to find a 'better' method of tying the rope into the harness.

Enter the Bowline (#1010).

Experienced/knowledgeable/skilled knot practitioners will all tell you never to trust your life to #1010.

Why?

Because it is not stable and it is not secure under cyclic loading profiles (tension-on, tension-off, tension-on and then tension-off again). Cyclic loading leads to gradual loosening of ABoK #1010. And when that happens, its the old 'express elevator to hell' trick - also known as 'decking', 'hitting the deck', 'ground-fall', 'logging big air time', etc.

Okay - so what do we do about it?

Answer = We modify ABoK #1010 and make it more stable and secure.

This subject has been almost exhaustively examined in this forum and by many others in the wider climbing community. Opinions are like cars - some people like Toyota Land cruisers, others prefer Nissan Patrols, some prefer Jeeps, some prefer Landrover Discovery while others prefer a Hummer. Who is right? Who is wrong?

One popular way of securing "#1010" is to use the so-called 'Yosemite finish'. Does this trick work? Answer = yes it does. But roo has a point, it also depends on the stiffness (see rope modulus article at the AMGA website... this link was working at time I wrote this post: http://www.google.com.au/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&ved=0CDEQFjAB&url=http%3A%2F%2Famga.com%2Fresources%2Fvarious%2FSequential_Failure_Paper.pdf&ei=0LXDUcLAHsWViAen1YGIBA&usg=AFQjCNEhz7ISMQ4oidnlpehtwgA2hEq1rg&bvm=bv.48293060,d.aGc&cad=rja ) of the rope you are using. Stiffer ropes might not behave so well with the Yosemite finish. There are other tricks we can employ - eg my own 'EBSB' variant discovered while playing around with Dan Lehman's 'EBDB'. There are still more variants out-there-in-the-wild. Not all have been subject to rigorous scientific testing - so caution needs to be applied.

As for the Portugese bowline, ABoK "#1072", this is not by itself going to improve the situation.

ABoK "#1085" is not a practicable method of tying a rope directly into a harness either!

So yes, the tried and tested ABoK #1047 is practicable, it is secure and it is stable. Arguably, it is also 'relatively' easy to learn and most importantly, is 'relatively' easy to remember.

I for one have no trouble trusting my life to ABoK #1047. I have climbed extensively since early 1983 and still climb frequently today (Himalaya, New Zealand, every major crag in Australia in all States and Territories and have established well over 100 first recorded ascents. I have also personally established a major new climbing area in Australia - Fredericks Peak). I have sustained literally over one thousand falls in my lifetime - some falls as big as 20m (metric). Since I am still typing this post in this forum, I must therefore still be alive and kicking. So I have extensive practical experience with ABoK #1047.

Most of my falls have been sustained on ABoK #1047. However, in relatively recent years, (since about 2009) I've been increasingly using and relying upon the 'EBSB bowline' variant. It is proven to work. As to whether it is 'better' than #1047 is debatable. It comes down to factors such as; ease of untying after repeated hard falls, the diameter of rope you are using, your body mass, and your level of knowledge and skill.

In summary, I do not believe that "ABoK #1072" is a practicable solution as a tie-in knot for climbing applications. I also don't believe that "ABoK #1085" is practicable either.

There has been some discussion about the Zeppelin loop as a possible solution and it has some strong supporters (roo?). In my view, this knot is harder to teach and harder to remember (ie memory retention) for novice climbers. before anyone starts jumping up and down and screaming...this is just my view. I hold this view because the zeppelin loop requires thinking in 3D - whereas "ABoK #1047" can be held flat (in a 2D plane) and its a simple matter of 'retracing' the path of the rope. Most learners can acquire the skill of tying ABoK #1047 'relatively quickly. It is not so easy to force the Zeppelin loop into a flat 2D structure and then weave the tail through the correct areas of the knot to create the finished product.

Also, there is no large body of evidence of in-field testing of the Zeppelin loop that I am aware of...(I could be wrong though) - but I have not found any test data or field tested evidence-based data re the Zeppelin loop. If there is, I would like to read and study it.

I believe that "#1047" and derivatives of "#1010" will be around for some time to come - and I don't see this situation changing in my lifetime.

Mark


« Last Edit: June 25, 2013, 03:38:33 PM by agent_smith »

X1

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Re: Relative security of multiple-loop knots
« Reply #17 on: June 21, 2013, 03:42:18 AM »
roo is also correct in his position that there are no recorded deaths due to arbitrary/random failure of #1047.

   Iff you mean that I said something like this, you are parooting roo too much ! I said that there were deaths due to the "grave, lethal mistake", of "leaving a non-functioning knot tied on a climbing rope" (sic).
   Read what I did say, please, and compare it with the usual roo s twisting my words :

in the future I hope to take up rock climbing
  Please, never, ever, even think about leaving a not-functioning knot still tied on a climbing rope !
  People have died because of this grave, lethal mistake !

  ( I am sure you know which accident I was talking about - although, at this particular accident the knot could had saved the climber s life, if the rope was just a few meters longer... :( )
   
 
« Last Edit: June 21, 2013, 06:32:33 AM by X1 »

roo

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Re: Relative security of multiple-loop knots
« Reply #18 on: June 21, 2013, 03:46:17 AM »
roo is also correct in his position that there are no recorded deaths due to arbitrary/random failure of #1047.
Actually, I was discounting Mr. X's concern that a relic/leftover knot from untying a Figure Eight Loop ever caused a death.

As an aside, I've seen quite a few novices have problems tying a Figure Eight knot form, even without retracing.  They often outgrow this difficulty, but it underscores the importance of knots that can be easily checked for correctness.

I think novices can outgrow difficulty with a Zeppelin Loop, too, especially with a couple of methods from which to choose, and of course it doesn't hurt if they master the bend form first.  And its simple, clear, symmetric form makes it easy to check.

I'll digress from further diversion from the thread topic.
« Last Edit: June 21, 2013, 03:21:12 PM by roo »
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X1

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Re: Relative security of multiple-loop knots
« Reply #19 on: June 21, 2013, 03:49:39 AM »
roo is also correct in his position that there are no recorded deaths due to arbitrary/random failure of #1047.
Actually, I was discounting Mr. X's concern that a relic/leftover knot from untying a Figure Eight Loop ever caused a death.
No wonder he is still parroting the same thing ! ( twisting my words, again an again, in the most aroogant manner...)
Parroots can not leave their cage - and, after a while, they may even not wish to leave it any more...

X1

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Re: Relative security of multiple-loop knots
« Reply #20 on: June 21, 2013, 06:27:41 AM »
   roo is correct - ABoK#1047 is the most widely used and relied upon tie-in method in the world of climbing.
   Who is wrong ? Who said that the retraced fig.8 knot IS NOT " the most widely used and relied upon tie-in method in the world of climbing" ?
   IFF you mean that I said such a dumb thing, ever, or that "I" would have been able to say such a dumb thing, ever, you are parooting roo too much, again ! Roo desperately wishes to twist everything that I write, so he would be able to throw some "wise" one-liner against me... Apparently, it is the only thing "he" is able to do. Roothless counterfeiting of what I write.
   WHERE did roo say something about the ABoK#1047, that, supposedly, I had denied ( so "he" is correct, and "I" am wrong...) ?
   WHY he does not include the ABOK#1047 in his .... collection of knots, in the so-called "notable" knots index site , or at :
    http://igkt.net/sm/index.php?topic=1150.msg7851#msg7851
    http://igkt.net/sm/index.php?topic=1150.msg8157#msg8157
    http://igkt.net/sm/index.php?topic=1150.msg8216#msg8216
    http://igkt.net/sm/index.php?topic=1150.msg8220#msg8220
   
    QED
   
   
   
 
« Last Edit: June 21, 2013, 06:29:02 AM by X1 »

Dan_Lehman

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Re: Relative security of multiple-loop knots
« Reply #21 on: June 21, 2013, 07:04:24 AM »
Firstly, let me compliment you on the longest post not
addressing the topic!
 ;D

Enter the Bowline (#1010).

As though it was not already --and long prior-- there?
(Royal Robbins's book Basic Rockcraft <c>1971 only
shows the fig.8 as a middleman's knot!)

Quote
Because it is not stable and it is not secure under cyclic loading profiles
(tension-on, tension-off, tension-on and then tension-off again).
Cyclic loading leads to gradual loosening of ABoK #1010.

Really?  Do you have any firm evidence of this?
Say, of the lazy ebb & flow of water on a moored boat,
or some testing done with deliberate cyclic loading?!

The bowline can loosen, and so should be guarded
against that, somehow; but I'm unaware of any direct
evidence that cyclic loading is identified as a cause.


Quote
Okay - so what do we do about it?

Refer to another thread?
Use a locktight eyeknot or symmetric fig.9 eye knot?

Quote
some falls as big as 20m (metric).

Holy Run-out, Batman!!

 ;)

X1

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Re: Relative security of multiple-loop knots
« Reply #22 on: June 21, 2013, 07:46:07 AM »
 
   of the lazy ebb & flow of water on a moored boat,
   I had never seen or heard about a mooring bowline loosened due to this particular kind of cyclic loading...However, one should notice that mooring bowlines are tied on mooring ropes ! Not the stiff slippery climbing ropes...

symmetric fig.9 eye knot?
   I have no experience in climbing whatsoever, and my knowledge of this field is infinitesimal compared to agent smith s...I can only say that I have friends who use the retraced fig.9 knot in canyoning and speleology, because, they tell me, they trust it more.
 
« Last Edit: June 21, 2013, 07:47:45 AM by X1 »