Author Topic: Cordage Movement & Melting Damage Risk?!  (Read 2225 times)

Dan_Lehman

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Cordage Movement & Melting Damage Risk?!
« on: February 02, 2018, 01:35:15 AM »
Rather than further this irrelevant discussion to the OP
of another thread, let's continue here.

Roo wrote
Quote
I'm not arguing that no force is transmitted around the object, merely that the 100% load at the standing part gets reduced to something below 100% past the entry point.

This becomes especially evident when you consider what happens to a Gnat Hitch when it is pre-snugged around an object, causing the legs to spread.  This is most easily seen by tying the hitch around a large test fixture and see at what leg angle the hitch stops contracting in free air and starts acting like a standard loop.  It's usually just shy of about 90 degrees.

So in an actual snug condition, instead of free air, we'd expect this balance point to occur even sooner.  And indeed, in high load testing of such hitches, it's not at all unusual to see the knot body to lift off the object and leave a gap, much like a loop.

And Agent_Smith reacted
Quote
The gnat hitch must not be used as a tie-in knot to a climbers harness - despite any assertion that a gnat hitch will reach a balance point (equilibrium) and stop cinching like a noose.
When tied into a climbing harness, the gnat hitch will act like a noose and cinch up tight - and so during the violent force of a free-fall, significant friction and resultant heat stress will occur to the harness textile material. The impact force of a fall is dynamic - and not a steady acting force - it is a sudden shock load.

Tie-in knots for climbing must be eye knots that do not collapse or tighten like a noose. The eye must be fixed.

The use of #409 (Poachers noose) and #1120 (scaffold noose) as termination knots for cows tails lanyard is used extensively in the rope access industry (see my previous link to IRATA code of practice). The noose is formed on a metal carabiner - not a textile harness.

To which Roo challenged :
Quote
I will take your lack of photos of the phenomenon you predict as concession that your nylon-melting hypothesis cannot be taken seriously.

If you want to be taken seriously, you need to do testing.

And I got searching.  Here is my first find, which is of rope
movement WAY more than a hitch will see,
but at forces WAY less than a fall will give --a question
of balance?!

Quote
http://www.theuiaa.org/documents/safety/Use_of_slings_when_lowering_off_and_abseiling.pdf
In 5mm cord (how thick harness loops?), of 9mm rope
only a meter of "lowering" an 80kg (standard UIAA mass)
cut through the sling.  (Hmmm, would that there were
some Kevlar slings to test!)  Thicker slings or rope (11mm)
took longer to (be) cut through.

I'm thinking that the clove hitch would fare well worse
than the less-material-to-move gnat hitch (but there might
be some other hitch to play the role I envisioned that would have
less potential movement (e.g., there's a constrictor-like oddball
in Hansel&Gretel's Encyclopedia...... (p.98#311, IIRC) !)

--dl*
====

agent_smith

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Re: Cordage Movement & Melting Damage Risk?!
« Reply #1 on: February 02, 2018, 01:46:31 AM »
Dan,

Can you change the title of this thread to:

"Noose versus fixed eye knot in direct attachment to harness for climbing or work at height applications"

This title more accurately reflects the precise nature of my concerns.

I would say that if any full-time climbers or rope access technicians are reading this thread - they might be inclined to chime-in and provide an opinion on why not a single training agency on Earth (our planet) recommends a noose structure as a means of rope attachment to a harness (nylon-to-nylon / textile-to-textile direct interface).

Mark

roo

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Re: Cordage Movement & Melting Damage Risk?!
« Reply #2 on: February 02, 2018, 05:18:48 AM »
After doing another battery of scaled-down tests (to safely allow absurd strains) on webbing with hard repeated impacts and not the slightest hint of melting or even warming, I think this nylon-melting myth is busted.

The webbing stayed pristine, as should be expected.  The amount of squeezing and standing part movement is pretty much equivalent to what one would see in typical bends such as a Carrick Bend or Zeppelin Bend. 

This opens up several advantages for a Gnat Hitch attachment for a belay loop:

1.  Less rope usage.

2.  Knot simplicity.

3.  High security.

4.  Reduced snagging risk because the gaping loop hole is eliminated.
« Last Edit: February 04, 2018, 01:02:39 AM by roo »
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agent_smith

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Re: Cordage Movement & Melting Damage Risk?!
« Reply #3 on: February 02, 2018, 10:27:48 AM »
Quote
I think this nylon-melting myth is busted

Obviously an extensive battery of tests have been conducted and peer reviewed - which led to the alarming conclusion posted above.

The issue is not instantaneous 'melting', rather - it is the progressive damage caused by direct nylon-to-nylon contact which is exacerbated by knots that act like a noose. Obviously, at the moment of impact in a free-fall event, a 'noose' will try to cinch tight (like a hangmans noose) - and this will cause accelerated wear on the textile material of the climbing harness. Direct nylon-to-nylon contact during free-fall events is known to cause wear - a possible cause of some serious/fatal accidents (eg Dan Osman) - and a worn harness belay loop is thought to be a causal factor in Tod Skinners case. The point being that 'sawing' action of nylon rubbing against nylon is a known causal factor of accelerated harness wear.

If any novice climbers stumble across this forum and find this post - please consider this advice.
Please review the attached photos. Note the warnings on using a noose as a tie-in knot to a harness for climbing applications.
Only use knots that have a fixed eye...do not use knots that act like a noose (which collapse and cinch tight as load is applied).

I have only shown the #1047 F8 eye knot, and the #1010 derived EBSB Bowline. Another alternative is Scott's locked Bowline (which is one of the simplest locked/secure Bowlines discovered).

I repeat again my warning of not using knots that act like a 'noose' for tying a climbing rope into a harness.
Those who ignore this advice should visit this site: http://www.darwinawards.com
Darwin awards are given to people who - through acts of unbelievable stupidity - remove themselves permanently from Earth's gene pool.

Mark G

« Last Edit: February 02, 2018, 01:30:01 PM by agent_smith »

roo

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Re: Cordage Movement & Melting Damage Risk?!
« Reply #4 on: February 02, 2018, 03:55:50 PM »
I repeat again my warning of not using knots that act like a 'noose' for tying a climbing rope into a harness.
Those who ignore this advice should visit this site: http://www.darwinawards.com
Darwin awards are given to people who - through acts of unbelievable stupidity - remove themselves permanently from Earth's gene pool.

Mark G
I see you updated your photo to get the connection wrong!  Now you have the Gnat Hitch trying to catch two points ::).  You had a general noose/hitch attached to the single belay loop before! See screen grab below.  It makes it extremely hard to attribute this to a simple error on your part.

Is this what you stoop to when your theories fall apart?

I'll repeat; "the webbing stayed pristine, as should be expected.  The amount of squeezing and standing part movement is pretty much equivalent to what one would see in typical bends such as a Carrick Bend or Zeppelin Bend." 
« Last Edit: February 02, 2018, 06:06:15 PM by roo »
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agent_smith

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Re: Cordage Movement & Melting Damage Risk?!
« Reply #5 on: February 02, 2018, 09:38:59 PM »
Quote
I see you updated your photo to get the connection wrong!  Now you have the Gnat Hitch trying to catch two points

Oh dear.

The photos shown are typical climbing harnesses - that's how they are designed!
Your comment immediately reveals deficient knowledge about climbing in general.
Any experienced climber reading your reply would also immediately know that you dont know much about climbing in general.

Hmmmm - and you are giving advice that is bordering on negligence - that is, advising people that it is okay to tie-in with a knot that acts like a noose is negligent.

Edit Note: Highlighted the word 'negligent' to draw its attention to readers.
« Last Edit: February 02, 2018, 09:41:13 PM by agent_smith »

roo

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Re: Cordage Movement & Melting Damage Risk?!
« Reply #6 on: February 02, 2018, 09:51:35 PM »
Quote
I see you updated your photo to get the connection wrong!  Now you have the Gnat Hitch trying to catch two points

Oh dear.

The photos shown are typical climbing harnesses - that's how they are designed!
Your comment immediately reveals deficient knowledge about climbing in general.
Any experienced climber reading your reply would also immediately know that you dont know much about climbing in general.
Please.  You were even involved with this lengthy thread on the topic of tying into the belay loop:
http://igkt.net/sm/index.php?topic=4444.0

Also, you were showing tie-in to a single webbing point earlier.  Sorry, you can't have it both ways.  It should be fairly clear that the discussion is about a single hitch point.

From the thread that spun off this discussion:

[...]
A secure hitch can be a viable option for many harnesses that have good single point tie-in location [...]

I also mentioned using the belay loop here: http://igkt.net/sm/index.php?topic=6081.msg40871#msg40871
« Last Edit: February 03, 2018, 12:53:22 AM by roo »
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agent_smith

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Re: Cordage Movement & Melting Damage Risk?!
« Reply #7 on: February 03, 2018, 04:06:40 PM »
Quote
Also, you were showing tie-in to a single webbing point earlier.  Sorry, you can't have it both ways.  It should be fairly clear that the discussion is about a single hitch point.

This thread is bordering on nonsense - I am almost aghast at how this is evolving into an almost oxymoron episode.

Quick educational tour is in order:
Recreational climbing harnesses come in 2 general designs as follows:
1. Single attachment point (mostly used by commercial school groups and some indoor climbing gyms); and
2. Dual attachment points (the most common type used by serious climbers - the climbing rope is fed through to capture 2 independent segments of the harness).

Now - you can try to obfuscate the crux of this matter as much as you like.
No matter which style of lower body recreational climbing harness (ie sit harness) you use - it is only advised to tie-in using a fixed eye knot. Tie-in knots that act like a noose significantly boost wear rates - via direct nylon-to-nylon (textile-to-textile) contact.
A noose will - a the moment of impact - collapse and cinch tight. A fixed eye on the other-hand, will not collapse and cinch tight.

A 'gnat' structure will act like a noose - it is not a fixed eye knot.

I an unaware of any climbing harness manufacturer in the entire world that would advise using a tie-in knot that acts like a noose. Most advise using #1047 (F8 eye knot) - which has a fixed eye. Any of the secure Bowlines can also be used (because they have a fixed eye that does not act like a noose).

I challenge you to find a climbing harness manufacturer that recommends a tie-in knot that acts like a noose. You wont find any...because it is obvious that using a noose will cause accelerated wear and tear on critical load bearing parts of the harness.

...

Now, I am trying to understand why you persist with this contest.
Any serious climbers who stumble across this thread will be stunned  by your advice that using a tie-in knot that acts like a noose is fine. They will (like me) be scratching their heads wondering why you are persisting with disseminating information that is bordering on negligence.

I think the underlying reason why you persist is deeply rooted in the fact that you don't like being challenged - you fee threatened - and this angers you. So you retaliate.
I can understand your basic human emotional need to retaliate - its sort of a flight or fight response (you choose to fight on to the bitter end no matter what the cost).

Look - it is obvious to me that you are not a lead climber. I am...I have been lead climbing (trad routes) since 1983 on a full-time basis - it is my occupation. I have personally established over 75 first ascents in Australia (ground up style - no prior top rope rehearsals or abseil pre-inspections). I have also attempted a first ascent in a satellite rock spire in the Ogre group (Karakorum Himalaya) and have several seasons of ice climbing in New Zealand south island (weather and time beat us in the end).

Search my name...Mark Gommers climbing - you will find the evidence.

I would be keen to see evidence of your lead climbing experience.

Interestingly, in all my long years of climbing experience - I have never seen anyone tie-in to their harness using a knot that acts like a noose.

I don't know if I care to reply anymore to this thread - because honestly, I'm getting bored with this child-like behaviour.

Mark G
« Last Edit: February 03, 2018, 04:12:55 PM by agent_smith »

Dan_Lehman

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Re: Cordage Movement & Melting Damage Risk?!
« Reply #8 on: February 03, 2018, 07:56:19 PM »
Quote
This title more accurately reflects the precise nature of my concerns
Your concerns are arguably more narrow --a subset of...--
than the survey should be (as "nylon-on-nylon" warnings
come in other places).

As you note, it isn't necessarily that any single event will
be catastrophic to new rope, but some cumulative damage/wear
could result.  (There was a tragic case of a famous climber
 [Todd Skinner, yes (alas)]<-edit
--American-- whose belay loop was soooo badly worn (by
perhaps only normal events, but years of ...) that it broke
as he hung on rappel (3 years or so ago?).)

Roo's point about the cinching-upon-impact movement
being --debatably-- much like that in common knots
is worth thinking about --both from accepting as within
range the hitch, and cautioning about cyclic damage for
knots in general, and maybe esp. some that have such
"gentle curvature" of the SPart and extended interface
before a hard U-turn that ... there is much material to
elongate when heavily loaded!
(The bowline likely sees fair movement back'n'forth
through its collar, but at such low pressure as to matter
little.  But I have wondered at some of the knots I've
fiddled wrt to this issue.  E.g., I suspect that knots with
the degree of looseness of mirrored bowlines could take
multiple drops (say, FF-1 : = length of rope = of fall)
and keep *giving back* much material vs. clamping
tight, "jammed" around it; but will such giving/taking...
show with a "shiny" sheath from frictional heat, of
the SPart's first nipping loop drawing back'n'forth
over the outgoing eye leg *root* /crossing point?!)

So, if there is even a limit to degree of damage of any
single event --i.e., yes, it will hurt rope, but not nearly
to catastrophe-- , a tie-in w/a hitch MID-WAY as part
of an overall eye-knot could be reasonable (for those
liking N things to count that would have to fail ...   :D ),
as I previously mused.

--dl*
====
« Last Edit: February 03, 2018, 08:00:44 PM by Dan_Lehman »

Dan_Lehman

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Re: Cordage Movement & Melting Damage Risk?!
« Reply #9 on: February 03, 2018, 08:00:00 PM »
Quote
I think this nylon-melting myth is busted

Obviously an extensive battery of tests have been conducted and peer reviewed
 - which led to the alarming conclusion posted above.

The issue is not instantaneous 'melting',
rather it is the progressive damage caused ...

Well, where's the extensive (or even ANY, specifically noting
our issue) testing data/report for hitch-like damage?
Pitt addressed the more extended (duration) abuse of lowering.
(To which I add :: IF THE CLIMBER LOWERED HERSELF,
there's be roughly half the force on the line!  --well,
outside of a top-rope situation, there's all the clipped-in
points to deal with, but ... ).

--dl*
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Dan_Lehman

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Re: Cordage Movement & Melting Damage Risk?!
« Reply #10 on: February 03, 2018, 08:10:07 PM »
This opens up several advantages for a Gnat Hitch attachment for a belay loop:

1.  Less rope usage.

2.  Knot simplicity.

3.  High security.

4.  Reduced snagging risk because the gaping loop hole is eliminated.

I don't think that "high security" is going to sell.  IMO, I've
some doubt about something sooo simple (like the bowline,
vs. structures that are more involved.  Yes, folks groan (NEClimbing
poster remarked ...!) at the so-involved mirrored bowlines,
but that, and the DAV-rec'd BoaBight give good assurance
in having so much stuff involved that, even loosely set, they
resist further loosening, and show loosening with telltale length
of tail (i.e., upon the last tuckings undoing).

If the squeezed set[ting] of the gnat *tires* after some time,
in the firm, slick-sheathed, bend-resistant cordage, maybe
helped with some rubbing against the wall, there's nothing
but a prayer left.  (To this complaint, there are like a few
tail-tuckings --gratuitous to the Purist, but ...-- that can
come to mind.)

Then there are some who like that "gaping hole" to serve
qua belay loop; there has even been discussion re this
ring-loading of the fig.8 eyeknot's eye, apparently
tried and okay's (BMC?).


--dl*
====
« Last Edit: June 23, 2019, 07:40:05 PM by Dan_Lehman »

agent_smith

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Re: Cordage Movement & Melting Damage Risk?!
« Reply #11 on: February 04, 2018, 05:15:59 AM »
Dan,

Would you be able to do me special request favor please?

Would you be able to track down a recreational climbing harness manufacturer that recommends a tie-in knot that acts like a noose?
Note: I use the term 'noose' to differentiate it from a tie-in knot that is a 'fixed eye'.

I would be most grateful if you could find such a harness manufacturer.

Dan_Lehman

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Re: Cordage Movement & Melting Damage Risk?!
« Reply #12 on: February 04, 2018, 10:57:43 PM »
... a recreational climbing harness manufacturer that recommends a tie-in knot that acts like a noose?

That's hardly answering any question, except what do
... recommend.  Softer would be whether they'd have
particular reason to warn against.  (After all, consider
that you're taking on some industry that recommends
NOT USING the bowline !)

--dl*
====
« Last Edit: February 06, 2018, 01:12:09 AM by Dan_Lehman »

Dan_Lehman

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Re: Cordage Movement & Melting Damage Risk?!
« Reply #13 on: February 06, 2018, 12:42:25 AM »
I browsed a couple of old (2008ish) gear catalogues of PMI,
Petzl, BlackDiamond, & OnRope1 --the BD one being pretty rockclimbing
centered, the others more broad or other-aimed (SAR, caving,
canyoneering, arborist).

I see a variety of harnesses.  SOME have a *clip-in* ring
of metal, which sort of concerns me re diameter (I've read
"10mm" for some separate rings, but am not sure that
what is part of the harness is as thick). Others have no
discernible means of closing --as though awaiting some
binding hitch or really snug eye to effect this (e.g., the
Goliath Expedition) !?  Some have two built-up attachment
eyes coming together, and the rockclimbing one's have a
belay loop connecting waist belt anchor point to the joined
leg-loops rather cord-like part; it seems that one will want
the looseness between waist & leg loops for activity, and
they should come together only on a fall being caught
(so a hitch would not be happy here).

It occurs to me to wonder at the compression of webbing
by the rope --esp. a hitch-- on catching a fall.  The lower
connecting point of the rockclimbing legloops is rather
rope-like, but the belay loop isn't --though I think that
it's advised NOT to tie-in to this--, nor other tape points.
Consider this one, the Fusion Climb Centar; anchor point
sure doesn't give much to hitch around (diameters, substance)!
www.amazon.com/exec/obidos/ASIN/B00J0W4Y92/ezclimbingharnesses-20


 - - - - - - - -

Another tie-in-structure idea :
1) clove hitch to tie-in thread (well, if all so darn skinny!);

2) take hitch tail up and put in a bowline,

3) then bring eye-knot tail down to tuck *through*
the clove h. --i.e., run it along tie-in "thread",
which increased hitch-to bulk-- ; and finally

4) take tail --which needed to be long enough-- up
to tuck through the bowline's nipping loop,
giving a 3rd diameter and further security.

The eyeknot should be abutting the hitch,
and thereby giving what I'll call "security by crowding"
--i.e., neither adjacent knot can loosen much, because
the other is in the way!  (And yet both knots can be
moderately loose.)  (The mirrored bowline has this
sort of slack security if properly dressed --so many parts
bumping into each other.)

And, no, this isn't violating the NO HITCHES rule,
really; the clove operating really as twin eyes
and distributing force over the 4 strands leading
around the anchor point (2 eyes, i.e.).


--dl*
====

agent_smith

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Re: Cordage Movement & Melting Damage Risk?!
« Reply #14 on: February 06, 2018, 12:44:16 AM »
Quote
you're taking on some industry that recommends
NOT USING the bowline !

A distraction/diversion off topic.

To save a lot of wasted time - I think you and I both know that there is no rock climbing harness manufacturer on planet Earth that recommends using a knot that acts like a noose as a means of 'tying-in'. This is not a comment...it is a fact.

Perhaps another way to look at this issue is to ask "Why".
That is; Why is it that rock climbing harness manufacturers never recommend a tie-in knot that acts like a noose?
Good question!

Answer: A noose will attempt to collapse at the moment of impact in a free-fall event.
Look at this photo: http://cruxcrush.com/2015/04/01/ten-reasons-why-men-are-better-at-climbing/ (No - not Arnold, but the one underneath!)
Now imagine at the moment of impact - what would happen if the climber had tied in with a 'noose'?

We already know that nylon-on-nylon isn't good in high energy falls.
I did some experiments several years ago with 3 wrap prusik hitches subjected to a factor 1 free-fall. The prusik hitch disintegrated in a puff! (see attached photo).
If you look at the photo - you will see evidence of melting (remnants of the prusik hitch are 'fused' to the parent rope).

Nylon-on-nylon saw-through is thought to be a causal factor in the death of Dan Osman.
Link: https://en.wikipedia.org/wiki/Dan_Osman (scroll down to 'death')

And please visit this link: https://groups.google.com/forum/#!topic/rec.climbing/gW92OrNs7_o
Report from:
 Chris Harmston
Quality Assurance Manager. Materials Engineer BS, ME.
Black Diamond Equipment Ltd

His conclusions were: "What is to be learned from this accident?  NEVER LET NYLON SLIDE AGAINST NYLON!  You should already know this."

...

Anyhow, I think there is sufficient information here to put the gnat (noose) quietly to bed. It definitely has its place in the world of knotting but, that place is not as a tie-in to a rock climbers harness.

EDIT NOTE: Links should be working now.
« Last Edit: February 06, 2018, 12:46:44 AM by agent_smith »