Author Topic: Video of Scott's Locked Bowline Slipping on Protrusion  (Read 3374 times)

roo

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Video of Scott's Locked Bowline Slipping on Protrusion
« on: May 08, 2020, 09:13:38 PM »

Since this is a matter affecting a practical knot, the practical knot folks in this sub-forum should also see this.  I noticed that once slipping starts, it is really easy to keep sawing away even if you pause and resume.  The protrusion must be affecting the knot body in some way.

This video was produced as a result of an incident report posted here:
https://igkt.net/sm/index.php?topic=6773.msg44540#msg44540

I have a new found respect for YouTubers and what a pain it is to produce videos.  This isn't my normal test area, so it was a bit of struggle to keep everything steady while I shot the video.
« Last Edit: May 08, 2020, 09:31:10 PM by roo »
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agent_smith

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Re: Video of Scott's Locked Bowline Slipping on Protrusion
« Reply #1 on: May 08, 2020, 11:49:40 PM »
To anyone reading and viewing this post - including the video.

THIS IS HOW MISINFORMATION PROPAGATES ON THE INTERNET

Note my following points:
1. That EN892 dynamic rope isn't used.

Only a reckless or incompetent person would lead climb with EN1891 low stretch rope.

2. That the knot in the test video is not dressed and cinched tightly.

Only a reckless or incompetent person would lead climb with a loosely dressed knot.

3. The size of the eye that the tester created for video is half the size of mainland USA.
Tie-in knots for climbing are not set like this. No climber would tie an eye this large - it is absurd.
The tester clearly has no concept of how climbing tie-in knots are tied to the harness.

4. The failure mode as depicted by this tester does not recreate real climbing conditions.
It cant be reproduced in real climbing conditions.
Therefore, the design of the test and its depiction is manifestly wrong and proves nothing.

5. Other tests with correct EN892 rope and a properly cinched knot with load reaching 5.2kN were unable to reproduce the results of this video.

6. The video of the test obscures the top and bottom half of the field of view. We cant see what the tester is doing.
The tester is initiating a carefully choreographed sequence on a loosely tied knot and the wrong rope.
Maybe there are gremlins that exist on a real rock surface who grasp the eye legs of your tie-in knot and then initiate some see-sawing pulling (downwards) all while the Standing Part (SPart) has no load?

Dan_Lehman

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Re: Video of Scott's Locked Bowline Slipping on Protrusion
« Reply #2 on: May 09, 2020, 12:13:49 AM »
To anyone reading and viewing this post - including the video.

THIS IS HOW MISINFORMATION PROPAGATES ON THE INTERNET
...
Careful, or you'll herniate yourself!

That it's a YMMV situation (ring-loading slippage is)
should be understood.

It is amply worthwhile to see knot behaviors in
various ropes, esp. ones closely associated with
each other such as the Cordage Institute-defined
"kernmantle" ropes are.  (I prefer to broaden that
term to mean *sheath over NON-rope (read, multiple
entities, from fibres to strands) core*, but it's clear
that current market forces chose the narrower term.)
A climber might well fancy using the same good,
recommended knot for tying off his BW II anchor
rope to something (requiring a nation-state-sized eye).
So, thus, was Lyon Equipment's testing of the clove
hitch
, which rockclimbers use for tying off belays,
but which LE's testing found holding only in their lone
dynamic rope (climbers use) and not low-elongation
ropes (LE's main focus), and likely this difference
could catch a tyer by surprise!

--dl*
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roo

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Re: Video of Scott's Locked Bowline Slipping on Protrusion
« Reply #3 on: May 09, 2020, 12:27:37 AM »
To anyone reading and viewing this post - including the video.

THIS IS HOW MISINFORMATION PROPAGATES ON THE INTERNET
Look in the mirror.  As I mentioned in the other thread,  I'm not taking any testing advice from someone who assumes that knots are only allowed to exist in taut line:


Answer: No - there is no such vulnerability and no such failure mode in real-world climbing conditions.

Assumptions:

4. That the tie-in knot was maintained under continuous body weight at all times during the test.
Something about KnotLikely's rope is close enough to the BlueWater II in the video.  It's probably the coefficient of friction.  The single coil just isn't enough for lower friction rope in this scenario:
« Last Edit: December 01, 2020, 04:20:35 PM by roo »
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agent_smith

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Re: Video of Scott's Locked Bowline Slipping on Protrusion
« Reply #4 on: May 09, 2020, 12:39:18 AM »
per Dan Lehman:
Quote
Careful, or you'll herniate yourself!
?
The herniation might occur when the gremlins pulling down on the eye of the tie-in knot cause alarm to the climber!

Quote
That it's a YMMV situation (ring-loading slippage is)
should be understood.
?
No - it doesn't when tying-in with EN892 rope and having a properly dressed and cinched knot.

Quote
It is amply worthwhile to see knot behaviors in
various ropes, esp. ones closely associated with
each other such as the Cordage Institute-defined
"kernmantle" ropes are.
?
Only from a purely academic point of view but the tester must declare the initial parameters and how the effect can materialize
 in real world climbing.
A statement such as; "The test conditions depicted in the video cannot be recreated in a real climbing situation."

Quote
A climber might well fancy using the same good,
recommended knot for tying off his BW II anchor
rope to something (requiring a nation-state-sized eye).
No lead climber would use EN1891 rope as a tie-in knot to his harness.
Even in top rope climbing, EN892 is the norm - because most modern self-braking belay devices are designed to function optimally with EN892 rope. Using EN1891 low stretch rope in a self-braking belay device can cause unpredictable results. Also, modern self-braking belay devices work better with ropes less than 11mm diameter.
As for tube type belay devices - again, they are principally designed to operate with EN892 rope. Using EN1891 rope in a tube type devices can be difficult to manage.

Yes- EN1891 rope is used to build anchors at the top of a cliff. If Scotts locked Bowline was employed to anchor the EN1891 rope to a sturdy tree - it would not be subject to the unrealistic loading conditions depicted in roos unrealistic video.

Quote
So, thus, was Lyon Equipment's testing of the clove
hitch, which rockclimbers use for tying off belays,
but which LE's testing found holding only in their lone
dynamic rope (climbers use) and not low-elongation
ropes (LE's main focus), and likely this difference
could catch a tyer by surprise!
Drifting off topic of roos unrealistic test conditions as depicted in his video.
Clove hitch is known to have performance variations in different ropes with differing modulus / bending stiffness.

agent_smith

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Re: Video of Scott's Locked Bowline Slipping on Protrusion
« Reply #5 on: May 09, 2020, 12:42:48 AM »
per roo:
Quote
Look in the mirror.
I did - and I saw gremlins magically pulling down on the eye of a loosely tied knot.

Quote
I'm not taking any testing advice from someone who assumes that knots are only allowed to exist in taut line:
There in lies you problem.
You need to take advice on how to set up a valid test for climbing tie-in knots.
You might be suffering from selective memory roo... in that the original point was a climbing tie-in knot.

I think the notional concept of a climbing tie-in knot has been lost in translation.

jimmyh

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Re: Video of Scott's Locked Bowline Slipping on Protrusion
« Reply #6 on: May 09, 2020, 04:13:35 AM »
Interesting. Can you get other bowline variants to do the same thing?

roo

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Re: Video of Scott's Locked Bowline Slipping on Protrusion
« Reply #7 on: May 09, 2020, 04:45:02 AM »
Interesting. Can you get other bowline variants to do the same thing?
I know it affects the standard bowline, but I do plan on checking certain others when I get some time.  I'll have to think about candidates, but it's not like there are lots of single-coil bowline variants that are in significant life-critical use, so it shouldn't be too burdensome. 
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Gordias

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Re: Video of Scott's Locked Bowline Slipping on Protrusion
« Reply #8 on: May 10, 2020, 11:48:14 AM »
Interesting. Can you get other bowline variants to do the same thing?
I know it affects the standard bowline, but I do plan on checking certain others when I get some time.  I'll have to think about candidates, but it's not like there are lots of single-coil bowline variants that are in significant life-critical use, so it shouldn't be too burdensome.
Roo - thanks for posting the video.  While I don't think it says anything about the security of any bowline, I'm glad I've seen it.

Just before I read this article, I was experimenting with this myself using light (approx 4mm diameter) hollow braided cord. 
To start with my conclusion: I agree (more or less) with agent_smith's judgement of the video.

Some observations (not actual tests) below with a standard bowline and "Scott's Locking Bowline" (Mark Gommers' terminology from his document on the PACI site):
  • When I held the nipping loop open, so it was possible to slide the loop, it was quite easy to lengthen and shorten the eye of the bowline
  • The perfect place to hold the nipping loop varies on whether I'm reducing or expanding the eye
  • I used two types of cord, one relatively new and clean, with a nearly circular cross-section, one old and "flattened", which is less slippery.  I could change the size of the eye with either one
  • The same thing was just as easy with "Scott's Locked Bowline"
  • If I don't hold the nipping loop open, the standard bowline tightens and the eye can't be expanded or contracted.  Because of that, I've never previously considered using this approach to "tune" the side of the eye - but IMO it's very convenient, so I'll use it in future
  • I started the "slipping experiment" because a mild version of the slipping effect happened by accident with "Scott's Locked Bowline" while I was working out a good sequence for tightening it
  • Needless to say, tightening both knots sensibly makes this kind of slippage extremely unlikely (perhaps "almost impossible", but I'm not a knot expert so I can't make such a claim :)
Background: I started playing around with this because I had a question about the "Yosemite Bowline", came here, found PACI thanks to a link in a thread, read Mark's excellent document, and decided to switch from the Yosemite Bowline to "Scott's Locking Bowline".  I'd played around with the "Monsoon Bowline" earlier (https://notableknotindex.webs.com/monsoonbowline.html - roo's site?).  It seems very secure, but it's a little too hard to tie for my purposes.  It meant that I recognized the "locking part" of  "Scott's Locking Bowline" immediately though, so I knew it wouldn't be too hard to tie and tighten, and this turned out to be the case. 

It's now my "go-to" "reinforced bowline", and will remain so unless someone serious demonstrates that it has a weakness.  That video is entertaining - but only in the way it's fun to show someone what happens when you tighten a "grief knot".  IMO it contains no useful information about the security of bowlines - though with the right framing it might be a useful reminder that a knot isn't tied until it's correctly finished.
« Last Edit: May 10, 2020, 12:34:56 PM by Gordias »

roo

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Re: Video of Scott's Locked Bowline Slipping on Protrusion
« Reply #9 on: May 10, 2020, 05:09:23 PM »
It's now my "go-to" "reinforced bowline", and will remain so unless someone serious demonstrates that it has a weakness.  That video is entertaining - but only in the way it's fun to show someone what happens when you tighten a "grief knot".  IMO it contains no useful information about the security of bowlines - though with the right framing it might be a useful reminder that a knot isn't tied until it's correctly finished.
Except that KnotLikely's incident involving the failure mode shows that this can occur as knots loosen in many rope types as they see flogging or other motion even among those "daily teeth flossers" who go to great lengths to eliminate most areas of daylight in their knot.

It might be beneficial to explore termination knots that can tolerate some deviation from absolute tightness especially since it is not known how much deviation is needed to make the Scott's Lock Bowline susceptible to the failure mode.   Thus far, it doesn't take much.

If you dislike the Figure Eight Loop and the Monsoon Bowline is overkill for you there are other possibilities:

Water Bowline
Zeppelin Loop or Double Zeppelin Loop

And my personal favorite for avoiding snags completely with excellent security and simplicity is tying to a belay band/loop or carabiner with a Gnat Hitch.
https://notableknotindex.webs.com/gnathitch.html

I think that would be especially attractive for you, Gordias, being someone who places a high value on ease of tying.

related:
https://igkt.net/sm/index.php?topic=6081.msg40871#msg40871
https://igkt.net/sm/index.php?topic=4444.0
« Last Edit: May 11, 2020, 05:19:02 AM by roo »
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Gordias

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Re: Video of Scott's Locked Bowline Slipping on Protrusion
« Reply #10 on: May 10, 2020, 07:12:07 PM »
Thanks for the link to KnotLikely's post.  I think I jumped to the end of that thread before checking out the details, and never went back to the start.

I just tried to replicate something like what KnotLikely described in the nearest thing I have to climbing rope these days: 15-year old 8(ish) mm kernmantel rope that we used to use for large hexes.  (BTW these days I only use it to practice tying new knots :)

I only tried once for each of standard bowline and Scott's locked bowline, but I was able to replicate the slide effect, lengthening the eye, both times.  All I had to do was loosen the collar until both legs were more-or-less straight, then pull on the side of the eye connected to the nipping loop. I doubt it would happen often IRL, but even once is enough to raise concerns.

Thanks for the links for the other three knots. I'll try them out during the week.

SS369

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Re: Video of Scott's Locked Bowline Slipping on Protrusion
« Reply #11 on: May 10, 2020, 07:18:46 PM »

Quote
Except that KnotLikely's incident involving the failure mode shows that this can occur as knots loosen in many rope types as they see flogging or other motion even among those "daily teeth flossers" who go to great lengths to eliminate most areas of daylight in their knot.

Very difficult, for sure. It really is terrible to tighten a knot.
Sheesh, the drama words... to try and sell your point.

Dan_Lehman

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Re: Video of Scott's Locked Bowline Slipping on Protrusion
« Reply #12 on: May 10, 2020, 07:41:46 PM »
I just tried to replicate something like what KnotLikely described
in the nearest thing I have to climbing rope these days: 15-year old 8(ish)
mm kernmantel rope that we used to use for large hexes.
(BTW these days I only use it to practice tying new knots :)

I only tried once for each of standard bowline and Scott's locked bowline,
but I was able to replicate the slide effect, lengthening the eye, both times.
All I had to do was loosen the collar until both legs were more-or-less straight,
then pull on the side of the eye connected to the nipping loop.
I doubt it would happen often IRL, but even once is enough to raise concerns.

I too tried to replicate either of the slippage behaviors,\
in a variety of ropes.

For Roo's ring-loading slippage, I got nowhere.
And now in re-looking at his video, it looks as
though there was HELP in the slippage by some
downward force on the SPart to boost the draw
from below of its turning around through the knot!

Anyway, I got nothing in ropes I tried,
which included old but mostly unused PMI E-Z Flex,
8mm firm accessory cord, silky smooth flexible firm
yachting rope (possibly Sta-Set X).  (And now I'm
remembering and worried about where my 9mm
BW II relatively new piece is!)

In the latter rope (SS-X), I could open things up as per
KnotLikely, and surprised like Roo that the knot
didn't fall completely apart (with an ample tail),
but opened with the Scott's Lock still present but
distorted.

.:.  I'm not seeing a real problem here,
and wondering about Roo's actual test method.
> I saw gremlins magically pulling down on the eye of a loosely tied knot.
AND PUSHING DOWN from On High!


--dl*
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Dan_Lehman

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Re: Video of Scott's Locked Bowline Slipping on Protrusion
« Reply #13 on: May 10, 2020, 07:51:16 PM »

Some observations (not actual tests) below with a standard bowline and "Scott's Locking Bowline" (Mark Gommers' terminology from his document on the PACI site):
  • When I held the nipping loop open, so it was possible to slide the loop, it was quite easy to lengthen and shorten the eye of the bowline

Whoa!  What's this?  It's not the nipping loop but
the collar (or nothing at all, but ring-loading) that's
at issue here.  Holding the core component of any
BWL loose is sure to wreck havoc.

Quote
  • If I don't hold the nipping loop open,
    the standard bowline tightens and the eye can't be expanded or contracted.
Well, it SHOULD be the case that at least in some
circumstances / materials you WILL see slippage
on ring-loading (expanding the eye w/o tension
on the SPart of the eye knot),
as the loading there in a way does the "hold the
nipping loop open" work preventing a sure nip
of the tail.

Quote
I had a question about the "Yosemite Bowline", ...
NB : if you tie the YoBowl in the usual way,
take the tail wrap *wide* --i.e., to the opposite
side of the SPart from where it should be if one
has flexible enough rope for that (otherwise, the
"wide" position will be more natural, bending less
on the wrap)--
and then instead of tucking it out through the collar,
turn it back and out through the nipping loop.  In this
way, the wide wrap and tuck back through ...
will have the tail lightly *binding* the SPart,
preventing it from (easy) loosening.  (One still
needs to take some care in dressing of the parts
inside the nipping loop.)

Alan Lee has shown this sort of tail binding, I believe.


---dl*
====[/list]
« Last Edit: May 11, 2020, 06:26:09 PM by Dan_Lehman »

roo

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Re: Video of Scott's Locked Bowline Slipping on Protrusion
« Reply #14 on: May 10, 2020, 09:46:32 PM »
For Roo's ring-loading slippage, I got nowhere.
And now in re-looking at his video, it looks as
though there was HELP in the slippage by some
downward force on the SPart to boost the draw
from below of its turning around through the knot!
I assure you, there was no "pushing" of the standing part.  How do you push a rope? ;D
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