Author Topic: Scotts locked Bowline (failure mode)  (Read 2954 times)

agent_smith

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Re: Scotts locked Bowline (failure mode)
« Reply #45 on: May 09, 2020, 02:24:21 AM »
While I was pondering roo's reflection in a mirror, it occurred to me that he could also run a second test.

It would be a reflection of his first test - where everything is 'reversed'.

That is, he could use EN892 rope instead of incorrect EN1891 rope.
He could dress and cinch the knot tightly - as opposed to loosely.
He could ensure the eye is no larger than 100mm - instead of half the size of mainland USA.

This would create a fair and accurate representation of the parameters in a real climbing situation.

If roo chooses not to run this second test - it would indicate that he is unwilling to report in a fair and balanced manner - choosing only to report biased tested results.
Furthermore, knowing that his original test is being propagated through the internet and likely being misreported/overstated, he has a duty to correct this situation.

SS369

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Re: Scotts locked Bowline (failure mode)
« Reply #46 on: May 09, 2020, 05:23:18 PM »
Quote
Thick BlueWater II is stiff line.  It's hard to get it to cinch tighter, and even if you managed it, it doesn't take much motion at all to spring to where it wants to go.

I don't agree with this. I can easily pinch a bight to close it smaller than one diameter.
I also don't believe that an eye that large is a real world use that will get snagged in the way you've contrived.

roo

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Re: Scotts locked Bowline (failure mode)
« Reply #47 on: May 09, 2020, 07:48:27 PM »
I don't agree with this. I can easily pinch a bight to close it smaller than one diameter.
I'm not disagreeing with the proposition that it is possible to get a tighter knot, especially if you are in the upper percentiles for strength.  I part ways with the idea that testing should give preference to the easiest conditions for a knot and ignore the rest of the bell curve.
« Last Edit: May 09, 2020, 08:00:33 PM by roo »
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SS369

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Re: Scotts locked Bowline (failure mode)
« Reply #48 on: May 09, 2020, 08:00:22 PM »
I don't agree with this. I can easily pinch a bight to close it smaller than one diameter.
I'm not disagreeing that it is possible to get a tighter knot, especially if you are in the upper percentiles for strength.  I part ways with the idea that testing should give preference to the easiest conditions for a knot and ignore the rest of the bell curve.

With any testing of knots, there should be a benchmark to adhere to. A fully tightened knot, such as minimal spaces within the structure would qualify for such adhoc tests.
Many knots will fail when left loose.
If you can't reach that benchmark, then I'd say the test doesn't qualify.

roo

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Re: Scotts locked Bowline (failure mode)
« Reply #49 on: May 09, 2020, 08:09:59 PM »
I don't agree with this. I can easily pinch a bight to close it smaller than one diameter.
I'm not disagreeing that it is possible to get a tighter knot, especially if you are in the upper percentiles for strength.  I part ways with the idea that testing should give preference to the easiest conditions for a knot and ignore the rest of the bell curve.

With any testing of knots, there should be a benchmark to adhere to. A fully tightened knot, such as minimal spaces within the structure would qualify for such adhoc tests.
Many knots will fail when left loose.
If you can't reach that benchmark, then I'd say the test doesn't qualify.
The pictured knot is hardly "left loose".  After some motion and bumps, even a tighter Scott's Locked Bowline knot could easily get looser than the one shown.  The tight hairpin change of direction at the lower edge of the knot doesn't lend itself to easy closing.  During failure in the video with the standing part sliding through the knot, it's not surprising that this ends up springing back more.

Nor does the two parts of rope going through the upper collar lend itself to a compact upper region.

One nice thing about the Figure of Eight loop, by contrast,  is that the gradual curvatures make for easier tightening and less tendency for spring-back.
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SS369

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Re: Scotts locked Bowline (failure mode)
« Reply #50 on: May 09, 2020, 08:44:37 PM »
I don't agree with this. I can easily pinch a bight to close it smaller than one diameter.
I'm not disagreeing that it is possible to get a tighter knot, especially if you are in the upper percentiles for strength.  I part ways with the idea that testing should give preference to the easiest conditions for a knot and ignore the rest of the bell curve.

With any testing of knots, there should be a benchmark to adhere to. A fully tightened knot, such as minimal spaces within the structure would qualify for such adhoc tests.
Many knots will fail when left loose.
If you can't reach that benchmark, then I'd say the test doesn't qualify.
The pictured knot is hardly "left loose".  After some motion and bumps, even a tighter Scott's Locked Bowline knot could easily get looser than the one shown.  The tight hairpin change of direction at the lower edge of the knot doesn't lend itself to easy closing.  During failure in the video with the standing part sliding through the knot, it's not surprising that this ends up springing back more.

Nor does the two parts of rope going through the upper collar lend itself to a compact upper region.

One nice thing about the Figure of Eight loop, by contrast,  is that the gradual curvatures make for easier tightening and less tendency for spring-back.

Well it is certainly well tightened. I wouldn't leave it like that for my use, especially in a life critical situation.
And I certainly don't believe that I will ever be in a scenario where the eye is that large and a "protuberance" will engage this knot as in the way you're forcing a failure.
If you accept the dressing and tightness of the video'd knot then please don't volunteer to be my climbing partner. ;-)
As for loosening up; it is the user who is responsible for diligence of their own safety.

Please lets not bring other knots into this thread. They have there own foibles.

agent_smith

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Re: Scotts locked Bowline (failure mode)
« Reply #51 on: May 10, 2020, 02:37:45 AM »
What continuously amazes me is the fact that there is no tester willing to step up to the plate and run the same test using EN892 rope in a properly dressed and cinched Scotts locked Bowline.

Furthermore, it also amazes me that none of the current crop of hobbyist/enthusiast testers test the other versions of Scotts locked Bowline.
They seem to fixate only on one of the 4 possible versions and also fixate on an eye half the size of mainland USA.

When pondering these facts - it strikes me as highly unusual and hints of experimental bias.

A potential problem with hobbyist/enthusiast testers is that they are not held to account for the design and structure of their testing regime.
They are free to undertake and publish whatever 'results' and 'conclusions' that fit their personal narrative. Human bias can also be driven my emotional desire to vindicate a personal opinion.

Here's a challenge for a hobbyist/enthusiast knot tester:
1. I challenge you to use EN892 rope
2. I challenge you to dress and cinch the knot tightly with an eye not exceeding 100mm
3. I challenge you to test all 4 versions of Scotts locked Bowline

And finally, I challenge you to publish your test results (with strict adherence to the above points) and write a conclusion.

KnotLikely

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Re: Scotts locked Bowline (failure mode)
« Reply #52 on: May 14, 2020, 11:36:32 PM »
This is the mode of failure that happened in real life. (Second video without me also holding the tail in place with the collar).

Make the knot tighter and you'll get more resistance.  At some point, you won't be able to overcome the initial friction with bodyweight.  Standard Scott's bowline (as opposed to the left hand / cowboy version) does not stay tight enough to prevent body weight from pulling standing line slack through.  Test all you want.  Decide that it is impossible all you want.  It happened in real life.  The slack all pulled into the eye-loops.

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, 03:06:22 AM by KnotLikely »

roo

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Re: Scotts locked Bowline (failure mode)
« Reply #53 on: May 14, 2020, 11:51:36 PM »
Somehow the tail stayed almost perfectly in place when this happened in real life.
My guess (as stated in the other thread) is that this might be consistent with a failure mode as shown in the video at the beginning of that same spinoff thread:



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SS369

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Re: Scotts locked Bowline (failure mode)
« Reply #54 on: May 15, 2020, 07:18:43 PM »
I don't agree with this. I can easily pinch a bight to close it smaller than one diameter.
I'm not disagreeing with the proposition that it is possible to get a tighter knot, especially if you are in the upper percentiles for strength.  I part ways with the idea that testing should give preference to the easiest conditions for a knot To Fail (As it should read)and ignore the rest of the bell curve.
I'm sorry that you seem to not have the determination or ?strength? to snug this knot as it should be, although it takes very little effort. Please don't use it.

If I use any knot, your gnathitch loose for example, it too will fail. Push or pull enough and Eureka! Please don't use it loose!

I have tested, with my own existence, this eye knot and used it exclusively for my eye knot needs and have never had a failure of any kind. I don't use it loose. And I tie in with it, using it with confidence born from my own tests and evaluated usage.
Other users have given positive feedback.

To anyone concerned: If you feel uncomfortable using it - don't.

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roo

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Re: Scotts locked Bowline (failure mode)
« Reply #55 on: May 15, 2020, 07:52:19 PM »
I don't agree with this. I can easily pinch a bight to close it smaller than one diameter.
I'm not disagreeing with the proposition that it is possible to get a tighter knot, especially if you are in the upper percentiles for strength.  I part ways with the idea that testing should give preference to the easiest conditions for a knot To Fail (As it should read)and ignore the rest of the bell curve.
I'm sorry that you seem to not have the determination or ?strength? to snug this knot as it should be, although it takes very little effort. Please don't use it.

I would request that when you quote my posts, you do not insert your own verbiage to make it look like I said something I did not say.
« Last Edit: May 15, 2020, 07:53:05 PM by roo »
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SS369

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Re: Scotts locked Bowline (failure mode)
« Reply #56 on: May 15, 2020, 08:55:53 PM »
Your request is under consideration.
It did look as though you forgot to write it though. I thought I was being helpful.
Next time I'll try to be more thoughtful.

KnotLikely

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Re: Scotts locked Bowline (failure mode)
« Reply #57 on: May 17, 2020, 09:09:15 PM »
Scott, do you set and dress this knot by tugging on the returning eye-leg until the collar folds the knot in half?

I've never once seen a picture of it that way, but that would explain why you think we have it set so loosely.  I generally tighten extremely hard without deforming the shape pictured in agent_smith's photos.

If I push the tail's hard turn around the nipping loop at the same time as I tug the returning eye-leg as hard as I can, the knot folds in half and the S-Part makes a hard bend.  I never really set it like that because I expect the S-Part to straighten on a fall until it forms the nipping loops.

I don't think of the collar of a bowline as something required to stay tight.  Am I wrong about that?
« Last Edit: May 20, 2020, 03:47:33 AM by KnotLikely »

SS369

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Re: Scotts locked Bowline (failure mode)
« Reply #58 on: May 17, 2020, 09:39:22 PM »
Scott, do you set and dress this knot by tugging on the returning eye-leg until the collar folds the knot in half?

I've never once seen a picture of it, that way, but that would explain why you think we have it set so loosely.  I generally tighten extremely hard without deforming the shape pictured in agent_smith's photos.

If I push the tail's hard turn around the nipping loop at the same time as I tug the returning eye-leg as hard as I can, the knot folds in half and the S-Part makes a hard bend.  I never really set it like that because I expect the S-Part to straighten on a fall until it forms the nipping loops.

I don't think of the collar of a bowline as something required to stay tight.  Am I wrong about that?

Hello Knotlikely.

I dress my and set all my knots tightly. I believe that a loose or slightly loose knot promotes failure or weakening due to friction upon load tightening. The movement under strain is mitigated more so if well tightened. IMO

I'm sorry you don't think that the collar should stay tight. My personal belief is that it should, as should the other parts.

As for the locked bowline, I tighten it in no particular order, just get it tight. When it is snugged well, I take and check it by pulling the eye legs apart (ring load it). I consider it ready for my use then.

Yes, the collar bends the SP and tail, but that straightens some under load.
It is then near to impossible to grasp the collar and pull it as shown in your video. Or I am such a weakling that I just can not do it.
As a climber and a man who works with his hands strenuously all day, I don't think the latter is quite so.

Once the collar is flexed back and forth the knot parts can be loosened for untying.
I have never been able to fail it, in any way, in various cords and ropes that I own ( a huge collection of many makers media) tied the way I do. Although, in tiny string or yarn it forget about untying it.  ;)

I have never claimed that this "lock" is the end all, be all. It is just a Simple lock, that works, for the #1010 common bowline.
Used correctly, it is a competent addition to secure the #1010.

One should have confidence in their tie in and if you lack this, use something else, by all means. It is your life on-a-line.
All knots (even spliced eyes) can fail, somehow, someway, whether by insecurities, jamming or breakage.

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Dan_Lehman

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Re: Scotts locked Bowline (failure mode)
« Reply #59 on: May 17, 2020, 11:00:42 PM »
Scott, do you set and dress this knot by tugging on the returning eye-leg until the collar folds the knot in half?
That was an admission some years ago,
but I think he's adjusted since then.  IMO, that is
NOT a properly set bowline (and in any case
is destined upon expected loading to pull out the
collar --can't load the nipping turn w/o getting past
the (too-tightly set) collar otherwise, though it
can be that the SPart yet is overly bent even so.
Also, the one-diameter bend is a hard thing to sell
to firm rope!

And such a binding isn't all so stable : in e.g. the
Perfection/Angler's loop (#1017), that is how the
SPart encompasses the eye legs, and can jam
rather firmly (but maybe its jamming has been
over-rated, for practical uses), but both of the
surrounded parts are under tension along with
the surrounding one; whereas in the BWL of a
tucked-out tail, the tail is NOT loaded,
and the 2dia widening the collar into tightness
can shift into a perpendicular-to-that orientation
(vs. collar-bight apex, one below the other,
so effectively a 1dia turn just backed up by
a 2nd 1dia part) --like having utility poles
in a straight line vs. in a triangular (for 3) group
such as can be found at piers.

Quote
I don't think of the collar of a bowline as something required to stay tight.
There is a variation --an extension-- that provides an
opposed-bight collar, which then can oppose the
basic one for a good tight nip on the SPart.
(Follow from the common BWL taking the tail
as the SPart's draw will take it (as done in the
Yosemite BWL and around on the outside
of the near side of the collar, back in on other
side between SPart and that collar side,
and --this is key to being able to loosen it--
then tuck out through nipping turn with
slight twist over/around SPart --which is what
makes this so-tucked tail a tool/lever to use
to prise out some bit of SPart, later, to loosen.

THIS knot can be set tight, as the SPart need
not bend one way or other, the opposed-bights
come together around IT.
AND I think it will defeat the particular loosening
mechanism you discovered fortuitously.  (bonus)


--dl*
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« Last Edit: May 17, 2020, 11:12:01 PM by Dan_Lehman »