Author Topic: Climbing knot name?  (Read 3213 times)

roo

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Re: Climbing knot name?
« Reply #15 on: January 30, 2018, 04:54:19 AM »
  On what do you base this assertion about physical properties?

How does one get all that compressive, frictional
force around the noose's SPart without affecting
what is upstream of that --namely, the passage
of the tension-bearing SPart down around the
harness tie-in points.
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.
« Last Edit: January 30, 2018, 04:55:14 AM by roo »
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agent_smith

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Re: Climbing knot name?
« Reply #16 on: January 30, 2018, 06:07:43 AM »
The original issue of the gnat hitch (noose) being used as a tie-in knot for climbing applications is being obfuscated and lost-in-translation.

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.

The attached photos:
1. Dangerous method - do not use a noose to tie-in (this is an analog to the gnat hitch/noose - they act like a noose - I dont have a photo of a gnat hitch/noose tie-in)
2. #1010 derived secure Bowline (EBSB)
3.  #1047 F8 (probably the most commonly used tie-in knot around the world)

In photos 2 and 3, the eyes are fixed (they do not collapse and cinch tight like a noose).
Mark G

roo

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Re: Climbing knot name?
« Reply #17 on: January 30, 2018, 10:33:31 PM »
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.
Gee, I thought the point of dynamic rope was to reduce sudden shock loads to modest loads that a human can endure. 

Anyway, you're descending beyond silliness with your grim reaper cartoons.  Instead of spending your time doodling, why not try to prove your assertions by dropping some weights and taking pictures of all the melted nylon? 

Most knot forms have some parts squeezing or compressing past other parts during load and survive quite easily.  I think we'll be waiting a long time for the pictures as my tests are unable to produce even a slight warming.

« Last Edit: January 30, 2018, 11:23:39 PM by roo »
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agent_smith

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Re: Climbing knot name?
« Reply #18 on: January 31, 2018, 01:29:19 AM »
I debated for a while whether I should reply any further to this nonsense.
But then I thought, okay - one last reply for any visitors to this forum who want a laugh.

Look - roo, its evident to me that you are not knowledgeable about climbing and how things generally work in climbing (and working at height) activities.

And that's fine - we can't be experts in all fields of endeavor.
Some people are expert in decorative knots (I'm certainly not).
Others have expertise in sailing related knot applications - and that's also fine.

But, it is plainly evident to me that you simply don't have the depth and breadth of experience to comment on knots that are used in fall-arrest applications for climbing and/or working at height.

So given that this is plainly evident - why should I waste my time educating you?
Normally I give advice under paid contract - so I would be happy to invoice you for my time if you wish to learn about climbing and general work-at-height.



agent_smith

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Re: Climbing knot name?
« Reply #19 on: January 31, 2018, 03:55:46 PM »
Found some spare time to snap a few photos of 'offset overhand bend' (aka offset ring bend) and some corresponding eye knots.
I haven't shown all possible variations - just 3 to compare.

Please note that all photos are showing knots loosely dressed for ease of examination.

Mark G

roo

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Re: Climbing knot name?
« Reply #20 on: January 31, 2018, 04:10:11 PM »
Normally I give advice under paid contract - so I would be happy to invoice you for my time if you wish to learn about climbing and general work-at-height.
Your biography, doodles, derogatory language, deflection, etc. is not evidence of your theory.   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. 
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SS369

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Re: Climbing knot name?
« Reply #21 on: February 01, 2018, 12:22:53 AM »
Normally I give advice under paid contract - so I would be happy to invoice you for my time if you wish to learn about climbing and general work-at-height.
Your biography, doodles, derogatory language, deflection, etc. is not evidence of your theory.   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.

It is time to take the back and forth, off original topic subject matter, either private or in another thread please.
Thank you.

Dan_Lehman

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Re: Climbing knot name?
« Reply #22 on: February 02, 2018, 12:07:12 AM »
Normally I give advice under paid contract - so I would be happy to invoice you for my time if you wish to learn about climbing and general work-at-height.
Your biography, doodles, derogatory language, deflection, etc. is not evidence of your theory.   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.
Touche' !

Yes, we SHOULD have some sort of drop-test-with-rope-movement
results for consideration (rather than the Nth testing of same ol'
knots devoid of detailed explanations ... --such as I recently posted
a URLink) !!  Surely there become discarded harnesses, and even
newly minted ones put to the test by manufacturers --either to
warn of the vulnerability, or to tout resistance to it (say, by
incorporating high-temp-resistant Kevlar into it) !?

I have conceived of a hitch-solution to the tie-in problem
as a way to have another in multiple, safety "back-ups",
e.g. as follows ::

1) tie a clove hitch to the harness (1st bonus : this puts
2 dia. of rope through then, which might be Good, IF
equally loaded)

2) (having left ample tail...) tie a strangle knot on tail
of clove near the hitch (this will serve first qua binder
on another tail, and in back-up work qua stopper against
the hitch) ; then

3) put in a bowline with the tail --something one can do
with a "PET = post-eye-tyable" eye knot--, and then

4) tuck the eye knot's tail through the binder (strangle)
and tighten up.

.:.  Now, the hitch first loads like double eyes --no running
against harness.  The binder cannot much loosen, given
the proximity of hitch & eye knots on either side.

So, first the eye knot has to loosen and come untied
(which it does somehow after the binder has lost grip
of its tail!);
then a fall loads the hitch which is closed down by the
compressing of the strangle (but with rope movement,
now); the strangle would have to loosen a lot, and
then migrate off a rather longish eye-knot&tail length
of end of rope before it cannot assist hitch-holding
(though if it CAN, I surely don't expect a mere clove
hitch to be in any effective state!!).

Again, though, in part of the above there IS a risk
of rope movement, at possibly high-loading.

--dl*
====

agent_smith

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Re: Climbing knot name?
« Reply #23 on: February 02, 2018, 01:35:53 AM »
Dan,

With all due respect:

The moderators have already intervened to put a stop to this nonsense and off-topic discussion.
You are perpetuating this discussion further (why)?

May I suggest that a new topic of discussion be started and titled as follows:
"Noose versus fixed eye knot for direct attachment to harness for climbing and/or work at height applications"
In that topic, we could explore why not a single training agency on Earth (including international bodies such as the UIAA) do not recommend noose structures for tying-in. We could debate nooses and their effect on textile harnesses during a free-fall.
The debate could focus on fixed eye knots versus a noose tie-in and how each performs in a fall-arrest event.

EDIT NOTE:
Ahh, I just noticed you have tried to start a new thread - but the title should be changed to:
"Noose versus fixed eye knot for direct attachment to harness for climbing and/or work at height applications"

Amen.
« Last Edit: February 02, 2018, 01:40:29 AM by agent_smith »