Author Topic: Video of Scott's Locked Bowline Slipping on Protrusion  (Read 958 times)

KnotLikely

  • Full Member
  • ***
  • Posts: 26
Re: Video of Scott's Locked Bowline Slipping on Protrusion
« Reply #15 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.

agent_smith

  • Sr. Member
  • *****
  • Posts: 1179
Re: Video of Scott's Locked Bowline Slipping on Protrusion
« Reply #16 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).
« Last Edit: May 11, 2020, 02:53:15 AM by agent_smith »

Dan_Lehman

  • Sr. Member
  • *****
  • Posts: 3909
Re: Video of Scott's Locked Bowline Slipping on Protrusion
« Reply #17 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*
====

roo

  • Sr. Member
  • *****
  • Posts: 1841
    • The Notable Knot Index
Re: Video of Scott's Locked Bowline Slipping on Protrusion
« Reply #18 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.
If you wish to add a troll to your ignore list, click "Profile" then "Buddies/Ignore List".


KnotLikely

  • Full Member
  • ***
  • Posts: 26
Re: Video of Scott's Locked Bowline Slipping on Protrusion
« Reply #19 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.
« Last Edit: May 15, 2020, 03:05:38 AM by KnotLikely »

roo

  • Sr. Member
  • *****
  • Posts: 1841
    • The Notable Knot Index
Re: Video of Scott's Locked Bowline Slipping on Protrusion
« Reply #20 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.
« Last Edit: May 14, 2020, 09:22:58 PM by roo »
If you wish to add a troll to your ignore list, click "Profile" then "Buddies/Ignore List".


KnotLikely

  • Full Member
  • ***
  • Posts: 26
Re: Video of Scott's Locked Bowline Slipping on Protrusion
« Reply #21 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.

SS369

  • Global Moderator
  • Sr. Member
  • *****
  • Posts: 1882
Re: Video of Scott's Locked Bowline Slipping on Protrusion
« Reply #22 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.

Dan_Lehman

  • Sr. Member
  • *****
  • Posts: 3909
Re: Video of Scott's Locked Bowline Slipping on Protrusion
« Reply #23 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*
====

KC

  • Sr. Member
  • *****
  • Posts: 284
    • latest project
Re: Video of Scott's Locked Bowline Slipping on Protrusion
« Reply #24 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.
Rope-n-Saw Life
"Nature, to be commanded, must be obeyed" -Sir Francis Bacon
We now return you to the safety of normal thinking peoples.
~ Please excuse the interruption; thanx -the mgmt.~