International Guild of Knot Tyers Forum

General => Practical Knots => Topic started by: roo on May 08, 2020, 09:13:38 PM

Title: Video of Scott's Locked Bowline Slipping on Protrusion
Post by: roo 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.
Title: Re: Video of Scott's Locked Bowline Slipping on Protrusion
Post by: agent_smith 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?
Title: Re: Video of Scott's Locked Bowline Slipping on Protrusion
Post by: Dan_Lehman 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*
====
Title: Re: Video of Scott's Locked Bowline Slipping on Protrusion
Post by: roo 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:
Title: Re: Video of Scott's Locked Bowline Slipping on Protrusion
Post by: agent_smith 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.
Title: Re: Video of Scott's Locked Bowline Slipping on Protrusion
Post by: agent_smith 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.
Title: Re: Video of Scott's Locked Bowline Slipping on Protrusion
Post by: jimmyh on May 09, 2020, 04:13:35 AM
Interesting. Can you get other bowline variants to do the same thing?
Title: Re: Video of Scott's Locked Bowline Slipping on Protrusion
Post by: roo 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. 
Title: Re: Video of Scott's Locked Bowline Slipping on Protrusion
Post by: Gordias 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):
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.
Title: Re: Video of Scott's Locked Bowline Slipping on Protrusion
Post by: roo 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 (https://igkt.net/sm/index.php?topic=6773.msg44540#msg44540) 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 (https://notableknotindex.webs.com/figure8loop.html) and the Monsoon Bowline (https://notableknotindex.webs.com/monsoonbowline.html) is overkill for you there are other possibilities:

Water Bowline (https://notableknotindex.webs.com/waterbowline.html)
Zeppelin Loop or Double Zeppelin Loop (https://notableknotindex.webs.com/zeppelinloop.html)

And my personal favorite for avoiding snags completely with excellent security (https://igkt.net/sm/index.php?topic=6076.msg40892#msg40892) 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
Title: Re: Video of Scott's Locked Bowline Slipping on Protrusion
Post by: Gordias 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.
Title: Re: Video of Scott's Locked Bowline Slipping on Protrusion
Post by: SS369 on May 10, 2020, 07:18:46 PM

Quote
Except that KnotLikely's incident involving the failure mode (https://igkt.net/sm/index.php?topic=6773.msg44540#msg44540) 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.
Title: Re: Video of Scott's Locked Bowline Slipping on Protrusion
Post by: Dan_Lehman 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*
====
Title: Re: Video of Scott's Locked Bowline Slipping on Protrusion
Post by: Dan_Lehman 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]
Title: Re: Video of Scott's Locked Bowline Slipping on Protrusion
Post by: roo 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
Title: Re: Video of Scott's Locked Bowline Slipping on Protrusion
Post by: KnotLikely on May 10, 2020, 10:38:38 PM
This video shows the effect that happened to me, except my harness loops were the dowel rod.

The ongoing eye-leg part of the nipping loop, Even When Fully Dressed And Tightened, is not held securely in place when there is any belayer slack.  The last portion of the nipping loop is secured only by the standing line and the collar.  These are simply not designed to stay tight in most single nipping loop bowlines when there is any slack in the standing line or the eye-loop.

The ongoing portion of the eye loop feeds back through 1mm of rope which is all that is necessary for the returning eye-leg to be free enough to feed a few mm of rope back into the nub to loosen the collar.  This is what the knot looks like when I am done with a single top-rope gym climb.  It does not stay extremely tightly set, though it maintains its shape and does not fall apart.

A few mm of extra line in the collar is enough for a snag.  As the returning eye-leg is bound in place by the collar snag, the force of a falling climber is applied to the ongoing eye-leg, resulting in the belay slack being taken up by the belay loop.  I'll try and get a video of this posted when I get a chance.  There is initial friction to overcome, but once the nipping loop starts to feed through (as shown in this video) there is nothing to stop it.

Yes, I'm talking about rated climbing rope.  Yes, I am talking about a knot initially set as tightly as possible before leaving the ground.  Yes, I am discussing slack in the standing line while lead climbing.
Title: Re: Video of Scott's Locked Bowline Slipping on Protrusion
Post by: agent_smith on May 10, 2020, 11:59:50 PM
KnoLikely's initial proposition (way back in earlier post) is that it was the collar that got snagged.
This has now been morphed into something of an entirely different character.
Snagging a collar to cause core disruption isn't within the realm of possibility.

The initial test conditions created in roos so called Eureka test were off nominal - and therefore invalid.
He would have to run the test again - using an eye set to 100mm and with EN892 rope.
If setting a loose initial dressing state - this would only serve as the 'control group' for the test.

Quote
The ongoing eye-leg part of the nipping loop,
The nipping loop is the nipping loop.
The outgoing eye leg is the outgoing eye leg.

The outgoing eye leg begins at the point where it exists from the knot core.

per KnotLikely:
Quote
This is what the knot looks like when I am done with a single top-rope gym climb.  It does not stay extremely tightly set, though it maintains its shape and does not fall apart.
?
I would suggest that you have not properly dressed and cinched your tie-in knot.
In the past 10 years of extensive lead and top rope climbing with Scotts locked Bowline (see image for 'my preferred' version) - I have never had a loosening event (ever).

Quote
There is initial friction to overcome, but once the nipping loop starts to feed through (as shown in this video) there is nothing to stop it.
One wonders how the initial friction is overcome while in the act of climbing.
You must have commenced climbing with an improperly dressed and cinched knot.
Its simply not possible to loosen by itself  - there has to be causality.
It is resistant to slack shaking and cyclic loading.

Quote
Yes, I am discussing slack in the standing line while lead climbing.
There is something rather peculiar going on - in terms of how the purported failure mode can actually get started and then propagate. Direction of loading is key here...
If you were lead climbing, the knot nominally lies in an inverted orientation in your harness - such that the SPart is pointing downwards.
If you were top rope climbing, the knot lies in its upright orientation - such that the SPart is pointing upwards.

This alleged 'snag' could not actually occur while in the act of climbing upwards.
Any purported snag of the eye of the knot would immediately cause alarm - and result in halting upward progress.
It would be quite a feat for any snag to catch a 100mm eye.

If the lead climber was being lowered back to the ground - the knot would lie in its upright orientation - with the SPart pointing upwards.
Again, while being lowered to the ground, the 100mm size eye would somehow have to catch upon a snag.
This is another feat to accomplish.

I just spent another entire weekend rock climbing (both lead and top rope) using Scotts locked Bowline.
I tried to catch snags in the 100mm size eye - with no luck.
I actually took 2 free-falls on a bolted sport route - and I found it impossible to scrape the front of my body down the rock surface while I was falling.
I would have injured myself in the process - so I simply could not get my body close enough to the rock to catch  any 'snags' while free-falling.

i did not climb a slab route. I'll try that next time - but again, I would have to scrape the front of my body down the rock surface - which would cause personal injuries. So its a difficult test objective in real-world climbing - in that the climbers body has to be in very close proximity to the rock surface - which is remote (ie highly unlikely).

I also ran a load test to expand the eye of Scotts locked Bowline and reached 5.2kN peak load.
I detected no core failure or enlargement of the eye - other than that caused by normal stretch under load.

EDIT NOTE 1: Image should be of reasonable quality now.

EDIT NOTE 2:
Scotts locked Bowline actually has 4 different geometries (I have only shown 3 - don't have 4th image as yet).
Scott actually drew my attention to this fact many years ago, pointing out that there are in fact 4 different geometries.
My personal favorite version is the first image - with the tail outside configuration.
The reason for this is that when the eye is circumferentially loaded (ie hoop stress) - the core takes on the characteristics of a #1431 Sheet bend and resists slippage.
There is nothing wrong with the tail inside versions - all versions are inherently secure.
Part of my confidence in the tail outside variation is that I have extensive real-world climbing experience with it. I have climbed something in the order of 500 single and multi-pitch routes in the past decade using this version and never had an issue with it (that includes free-falling).
Title: Re: Video of Scott's Locked Bowline Slipping on Protrusion
Post by: Dan_Lehman on May 11, 2020, 06:30:28 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
Pushing a firm rope is done as one might think
(re pushing, if not re rope).
There doesn't seem to be much tension on the
SPart in the video, as it variously moves from
side to side, contrary to something with some
resistance being drawn --tensioned-- downwards,
that's all.

Anyway, I got nowhere trying to replicate it,
which is quite in contrast to the free-flowing
you're showing.
I DID get some of the snagged-collar opening,
and --to OUR surprise-- without the knot spilling
(given a mod. long tail, but not terribly long).


--dl*
====
Title: Re: Video of Scott's Locked Bowline Slipping on Protrusion
Post by: roo on May 11, 2020, 06:38:57 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
Pushing a firm rope is done as one might think
(re pushing, if not re rope).
There doesn't seem to be much tension on the
SPart in the video, as it variously moves from
side to side, contrary to something with some
resistance being drawn --tensioned-- downwards,
that's all.
The standing part was draped over a cup-holder to keep it out of the way, with the remaining rope weight offering minimal tension.
Title: Re: Video of Scott's Locked Bowline Slipping on Protrusion
Post by: KnotLikely on May 14, 2020, 09:02:31 PM
https://vimeo.com/418599010

The knot is not built to stay rock solid tight.  The nipping loop and collar are not structures that are made to prevent the ongoing eye-leg from feeding back through the 1mm necessary to allow the returning eye-leg the ability to give an extra couple mm to the collar.

https://vimeo.com/418599156

I was holding the tail in this video.  Yes, I'm only pulling on the ongoing eye-leg.  The returning leg is directly stuck on a snag.  Yes, there should be extra friction from the harness loops sliding down the rope, but there should also be much more weight than me just quickly tugging.  I can't currently get video of this on the wall (without endangering my skull).

Somehow the tail stayed almost perfectly in place when this happened in real life.  I assume that it was pinned by the snag, somehow.  I slid a few feet down a vertical face.  I assume the knot was pointed down (gravity, and all) and turned up when it hit what it snagged on.  The knot, as pictured in this video, is not immediately post setting.  I held the standing end and banged it on the ground two times then immediately took this video.  I would guess this is equivalent to having climbed a little bit.  Scott's lock (non left hand / cowboy version, at least) knot does not stay perfectly set.  This is rope that I have personally climbed on at, and was purchased by, my gym before it was cut into sections for discarding.  I was given this piece to practice tying with.  It is most certainly a rope built and rated for climbing.  I trust that my gym and insurance company are not messing around.  I'll be happy to get the brand and model when they open back up.
Title: Re: Video of Scott's Locked Bowline Slipping on Protrusion
Post by: roo on May 14, 2020, 09:21:35 PM
Somehow the tail stayed almost perfectly in place when this happened in real life.
This is another clue that makes me think that the snag might have been more like the first video in this thread.  A loop-only snag would make a much bigger and easier target.

Things happen so quickly during a fall, it's hard to see in the moment.
Title: Re: Video of Scott's Locked Bowline Slipping on Protrusion
Post by: KnotLikely on May 14, 2020, 11:07:55 PM
Somehow the tail stayed almost perfectly in place when this happened in real life.
This is another clue that makes me think that the snag might have been more like the first video in this thread.  A loop-only snag would make a much bigger and easier target.

Things happen so quickly during a fall, it's hard to see in the moment.

I looked up and saw the snag on the wall as it fell off.  I do not believe my eye loop touched anything except for my harness.
Title: Re: Video of Scott's Locked Bowline Slipping on Protrusion
Post by: SS369 on May 15, 2020, 07:23:35 PM
https://vimeo.com/418599010

The knot is not built to stay rock solid tight.  The nipping loop and collar are not structures that are made to prevent the ongoing eye-leg from feeding back through the 1mm necessary to allow the returning eye-leg the ability to give an extra couple mm to the collar.

https://vimeo.com/418599156

I was holding the tail in this video.  Yes, I'm only pulling on the ongoing eye-leg.  The returning leg is directly stuck on a snag.  Yes, there should be extra friction from the harness loops sliding down the rope, but there should also be much more weight than me just quickly tugging.  I can't currently get video of this on the wall (without endangering my skull).

Somehow the tail stayed almost perfectly in place when this happened in real life.  I assume that it was pinned by the snag, somehow.  I slid a few feet down a vertical face.  I assume the knot was pointed down (gravity, and all) and turned up when it hit what it snagged on.  The knot, as pictured in this video, is not immediately post setting.  I held the standing end and banged it on the ground two times then immediately took this video.  I would guess this is equivalent to having climbed a little bit.  Scott's lock (non left hand / cowboy version, at least) knot does not stay perfectly set.  This is rope that I have personally climbed on at, and was purchased by, my gym before it was cut into sections for discarding.  I was given this piece to practice tying with.  It is most certainly a rope built and rated for climbing.  I trust that my gym and insurance company are not messing around.  I'll be happy to get the brand and model when they open back up.

I'm seeing this video as proof of your ability to easily untie the knot using whatever rope you are using in the video.
If you are out to prove this knot's insecurity then you'll have to show it in a more useful way.
And if you don't care for it, just use another...
BTW, it is not just for tying in.
Title: Re: Video of Scott's Locked Bowline Slipping on Protrusion
Post by: Dan_Lehman on May 15, 2020, 07:31:31 PM
If you need to guard against snagging,
ack, that I think implies a more *involved*,
complex knotted structure.  The mirrored bowline
has a SPart collar that leads of course to the eye
and tail-wise to a back'n'forth through the two
nipping loops; which two loops should impede
the sort of SPart-flow that you saw.  (They did
stop that in slick HMPE for one Brion Toss test.)

One has other ways to make some compound
structure with greater protection; note that the
bowline can be cast into a line *atop* any
other knot, then have its tail reeved into that.


--dl*
====
Title: Re: Video of Scott's Locked Bowline Slipping on Protrusion
Post by: KC on May 16, 2020, 10:23:41 PM
If the single leg of SPart was fully loaded,
and each leg of eye 1/2 loaded;
as Equal & Opposite loaded pair..
.
Is definitively different than going around locking mechanism with force path
>>let alone using 1 side of the E&O pair to pull lock apart.
>>in many forms
An RT mechanism would make less likely
because of 3 half arcs upgrade from 1 of force
.
Have seen in some texts the reason for innie not outie on BE of Bowline was not to snag to invert when unloading ships.