Author Topic: Break testing of the Alpine Butterfly Knot  (Read 12423 times)

Dan_Lehman

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Re: Break testing of the Alpine Butterfly Knot
« Reply #30 on: May 03, 2015, 06:50:52 PM »
X. posted some images more recently, too --adding the version-A after I remarked of the missing "perfect form".

   " adding the version A after I..." :) :) :)
  Your ability to distort facts and history is remarkable, indeed !
  It was exactly the other way around !  :)
Nooope, it's your penchant for taking offense,
for seeking it in everything, and so mis-taking
the meaning intended : simply, in that particular thread
you (kindly & quickly) supplied that image (and
that thread is moREcent than the others, yes).

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I am sick and tired to repeat the same things over and over again !
Unless it's the raving about a hinge in the zeppelin,
or ... .

--dl*
====

xarax

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Re: Break testing of the Alpine Butterfly Knot
« Reply #31 on: May 03, 2015, 07:21:15 PM »
in that particular thread you (kindly & quickly) supplied that image

   Aha ! I see ! You have been swallowed by a wormhole, and you are now at the other side !  :)
   Because I HAD SUPPLIED THIS SAME IMAGE 5 ( five ; one, two, three, four, five : you can use your fingers to count, you know  :)) years ago ( ago, before, in the past, then, etc : PAST tense...)

1. http://igkt.net/sm/index.php?topic=2198.msg15419#msg15419
2. http://igkt.net/sm/index.php?topic=2198.msg15419#msg15419
3. http://igkt.net/sm/index.php?topic=2198.msg15419#msg15419
4. http://igkt.net/sm/index.php?topic=2198.msg15419#msg15419
5. http://igkt.net/sm/index.php?topic=2198.msg15419#msg15419

(Repetition is the mother of knowledge
This is not a knot.

knot rigger

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Re: Break testing of the Alpine Butterfly Knot
« Reply #32 on: May 04, 2015, 12:54:09 AM »
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You're being ambiguous

If I was ambiguous, it was on accident.  I was merely making observations on the question of the two versions of the figure 8 loop.  As I said, I'm not convinced there is a difference in strength, it is an unanswered question to me.  (ie, up for debate)  The question is important to me, as the figure 8 loop is part of the foundation of rope's access work, and much of what I do.  I, and my co-workers, rely on a figure 8 loop knots that I tied every day, and you can see how their strength may be of some interest to me. 

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which pins both claims I think to 2nd versions

correct, I have 2nd editions of both texts.  If you'd like me to scan and send you the pertinent pages of Life on a Line I would be happy to.

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Any idea where I can find a copy of Rob Chisnall's Reference manual? 
Not of any official source

I would be interested in obtaining a copy, if anyone knows where I can.

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10 %-points" or purely "10%".

I agree that Merchant is could be more specific here.  He just says 10%

Given that he states this can be difficult to show with breaking tests, I am dubious of performing these test, but I may proceed anyway if I feel I may obtain meaningful results.  It would be an interesting challenge, if nothing else.

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Do you have [Neil Montgomery's Single Rope Techniques]?

Not yet, I ordered a copy on amazon.  I'll share what I find.

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??  Common wisdom?  I don't see evidence of what I'd
call "wisdom" --it would have to be inferred by absence of
counter statements--, but rather a common ignorance
of the difference

Indeed, it may be common ignorance.. but ignorance by persons, who as a group, trust this knot with their lives, and the lives of others. 

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Personally, I agree with the common wisdom, but I have been tying 8s
Merchant's way since I read his book.  His way certainly can't be worse!

Why not?

Well, that is a good question.  One, an appeal to the greater wisdom of the industry at large.  Two, if there is a difference, it is only 10% or less (according to the "experts") and a fig 8 knot is still one of the strongest, secure, and easily verifiable knots for the purpose.  Three, Dr. Merchants reasoning is sound IMO, that his "stronger" version has a larger radius first bend in the load bearing line.  It stands to reason that a wider bend is stronger than a tighter bend.  The question, to me, is if this slight difference has large, or important influence in how the knot performs.

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Now you scare me : how can CMC come out with such
nonsense?!!!  I mean that in the sense that LOTS of
testing has put its strength well higher than 50% !!

I had no intention of giving you a fright!  ;)  It seems clear to me that CMC revised there assertions based on the presence of new data.

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the no-longer-easily
available Dave Richards testing

If anyone could provide me Mr. Richards testing, I would appreciate it.

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I could suggest Outdoor Knots by Clyde Soles
(and w/help from ...  ;D ) as a fresh, different treatment.

Thanks for the tip, I'll pick up a copy

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Okay, not an acronym, but ... what is "birdcage"
qua verb?!  And "trapeze" as in the usual thing,
with people swinging?  --and then "would eventually
BREAK" ??!  What's with the swinger, then?!
As for friction of jacket on HMPE core : I'd think that
there'd be not much --less than for other then HMPE,
anyway.

Okay, "birdcage" is a terms usually applied to a deformation of wire rope, usually due to shock loading, where the strands gain a permanent deformation, or twist, that allows you to see daylight through the lay of the line.  It looks like a little metal birdcage.  I used the term to describe a similar deformation, or bump, in the 12 strand core of the rope I describe.

The rig I describe has a "crane bar", (a metal bar from which the trapeze is suspended).  The crane bar is held up by two chain hoists, and has four guy wires to hold it's position.  The crane bar is first flown in (down) slightly below its final position, the slack guy lines are a then attached to achors on the ground, and the crane bar is flown out (up) to its final position, thus tensioning the guy lines.  Then the artist swings on the trapeze for her act, which cyclically and dynamically further loads the guy lines.

The guy line rope is constructed of a vectran core, with a polyester jacket.  The guy lines had spliced terminations on each end.  The original construction of the guy lines (the ones that birdcaged) was that the jacket was stretched equally tight as the core during fabrication.  The eventual failure of these lines occurred at one of these bumps.  After failure the external appearance of the line was hourglasses at the failure point, indicating that the core had ruptured, while the jacket was still intact.  Cutting open the line, to inspect the core, showed the rupture point to be very fuzzy and extremely elongated, signs of a failure due to abrasion.  This failure mode occurred on multiple lines within a few days of each other.  We initially replaced the lines with new ones fabricated the same way: with the jacket tight to the core, and the replacement lines began showing the same bird-caging within weeks.  I then fabricated a new set of line, but with the jacket very slack.  Even under tension, the jacket could be easily milked along the line.  These new lines never exhibited any of the bird-caging the previous lines did.  Also, the new lines had a much softer hand to them than the old ones.  The old lines were very stiff, and coiling them was similar to wire rope, or very stiff kernmantle.  The new lines felt like a soft class one double braid.

Dan_Lehman

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Re: Break testing of the Alpine Butterfly Knot
« Reply #33 on: May 04, 2015, 10:12:51 PM »
correct, I have 2nd editions of both texts.
If you'd like me to scan and send you the pertinent pages of Life on a Line
I would be happy to.
Thanks for confirmation & offer.  I have the latter,
but might ask particular questions re On Rope, 2nd ed..


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10 %-points" or purely "10%".

I agree that Merchant is could be more specific here.  He just says 10%
As do so many others, alas.

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Given that he states this can be difficult to show with breaking tests,
I am dubious=>[doubtful] of performing these tests, but I may proceed anyway
if I feel I may obtain meaningful results.
It would be an interesting challenge, if nothing else.
I would tie specimen knots in both ends.  For this test,
since you have a seemingly well-calibrated device, you
could make them same-orientation,
or otherwise you have --in addition to what the device
might record, in absolute values-- A-vs-B testing.  In
either case, with eye knots at both ends, you get one
that survives intact, for examination.  Now, were the
results so pure that dressing-XYZ was always breaking
and leaving dressing-PQR the survivor, you might feel
that you'd found a pattern, BUT would want to get a
surviving weaker dressing and so need to double up
on that, at least for this point of record.

And given your relatively not-so-strong material (if you
are indeed continuing to use something like that),
you should be able to get a good firm set as I specify
with pulling on tails, to try for that, *baked-in*, twin-part
path-shaping for the SPart to bear against.  At least, this
is my theory and the best sense I can make of how that
"stronger form" (my label) could in fact be stronger
(for the turn around the eye legs seems rather sharp,
arguably worse than using the other end qua SPart).

But, another aspect of this "perfect form" (not the
Layhands form, mind)  fig.8 is that maybe with
the "weak form" one gets less hard constriction of
the eye legs and therefore they bring more gripping
effect where they collar the SPart and that is
what gives strength --some frictional off-loading of
force at the entry point!?  --Theory-2, which, note,
puts significance to effects coming before any hard
radius of turning is encountered.  ;)
(In any case, it is interesting to note that the eye knots
are often found stronger than the end-2-end knot!?
(E.g., one fellow used a truck to do A-vs-B end-2-end knot
testing, and all specimens were anchored w/fig.8 eyeknots
none of which ever broke (even vs. a case where effectively
the same structure was there, in the "twin fig.8s" joint
which is essentially two eyes sharing the eye strands!?).)
(CMC 3rd ed. has end-2-end & eyes equally at 80-81%.)

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Do you have [Neil Montgomery's Single Rope Techniques]?

Not yet, I ordered a copy on Amazon.  I'll share what I find.
Great, thanks much!   :)

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Indeed, it may be common ignorance.. but ignorance by persons,
who as a group, trust this knot with their lives, and the lives of others.
Which could be a point to worry about!
I recall Tom Moyer lamenting that despite his efforts to warn
some group about the dangers of the offset fig.8 end-2-end knot
(aka "fig.8 EDK"), they seemed unconcerned about it.

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Now you scare me : how can CMC come out with such
nonsense?!!!  I mean that in the sense that LOTS of
testing has put its strength well higher than 50% !!
It seems clear to me that CMC revised there assertions based on the presence of new data.
Yes, fine, but also in the face of solid other data
--or did they admit to having indulged "youthful indiscretions"
at prior data gathering/interpreting/recording?!?   ::)

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If anyone could provide me Mr. Richards testing, I would appreciate it.
Ah, it came out nicely, via Agent_Smith's hosting --voici
www.paci.com.au/downloads_public/knots/03_Cordage_Institute_Tests.pdf
And here are remarks about the mistakes in the labeling
of data --a simple case of A vice B & vice versa : soooo
simply noted (even w/o correction), but Smith it seems
has found levels of "embeddiing" of error upon error,
sadly w/o a sane reviewer to set straight.  And, so it has
languished in Purgatory of non-presented status, waiting
for Godot.  Thanks again to Agent_Smith for doing better.
www.forums.caves.org/viewtopic.php?f=5&t=12907

NB : knots are identified nominally; we do NOT see images
asserted to show geometry!

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I could suggest Outdoor Knots by Clyde Soles
(and w/help from ...  ;D ) as a fresh, different treatment.

Thanks for the tip, I'll pick up a copy
NB: the "square fisherman's" got mis-represented in the
photo --it there is actually a, um, "thief fisherman's" : yeah,
tied a thief knot backed with strangles (not how the
climbing community names things, but ... .  (Clyde protested
that it couldn't be, for he doesn't know how to tie the thief;
I infer that, yes, he doesn't, but tied what he intended (and
missed) by flipping his ropes around to tie off with the strangle
and --these being short pieces-- confused tail w/SPart !
OTOH, arguably, this shown is better, easier to untie
(just make sure that the strangles stay tied --which,
if they're set snug to the thief, they have grounds to
be more secure, as slippage will snug them up further!)
.:.  a play in double-edgedness!
(I saw photos too late for corrections to be made.)

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Okay, "birdcage" is a terms usually applied to a deformation of wire rope,
usually due to shock loading, where the strands gain a permanent deformation,
or twist, that allows you to see daylight through the lay of the line.
It looks like a little metal birdcage.
That was my surmise, except I've trouble with ...
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  I used the term to describe a similar deformation, or bump,
in the 12 strand core of the rope I describe.
... how one sees ANYthing in the core?!?!
What's happening with the sheath, to enable this?
(If it's in postmortem cut-&-see, well, okay; but it
still seems odd for the core to have such strength
to birdcage within a close-fit sheath, IMO.
--and more problems with Vectran, hmmm.
(Used on one of rockclimbing gear-seller's hi-mod
lines (5.5mm) and discontinued, for dubious results.)

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The guy line rope is constructed of a vectran core, with a polyester jacket.  The guy lines had spliced terminations on each end.  The original construction of the guy lines (the ones that birdcaged) was that the jacket was stretched equally tight as the core during fabrication.
//
I then fabricated a new set of line, but with the jacket very slack.  Even under tension, the jacket could be easily milked along the line.
I'm struck by "fabricated" : implying one's own making,
and not a (complete) "store-bought" product. !?

I'm stumped for an explanation, other than musing that
somehow there was a segment (or few) where the original
sheath was less married to core and slipped back'n'forth
over it, and the Vectan suffered not the polyester (though
the former is much better with heat, but not so, abrasion?!)!?
With a relatively tight sheath, it could be load bearing.
But with a slack sheath, the core didn't have such *oppression*.

And the failure was incomplete, not catastrophic --the sheath
was working, the guy still stabilized , the problem was seen
(before the hourglass ran out of time).  --and yet, in just
some few days (or was it a longer period per line, and that
each of the quartet of guys came to grief in short order?)!


--dl*
====
« Last Edit: May 05, 2015, 09:29:33 PM by Dan_Lehman »

knot rigger

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Re: Break testing of the Alpine Butterfly Knot
« Reply #34 on: May 05, 2015, 10:27:32 AM »
Quote
I could suggest Outdoor Knots by Clyde Soles
(and w/help from ...   ) as a fresh, different treatment.

Thanks for the tip, I'll pick up a copy

Dan, take a closer look at picture 7.21 in outdoor knots. 

Dan_Lehman

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Re: Break testing of the Alpine Butterfly Knot
« Reply #35 on: May 05, 2015, 09:45:28 PM »
Quote
I could suggest Outdoor Knots by Clyde Soles
(and w/help from ...   ) as a fresh, different treatment.

Thanks for the tip, I'll pick up a copy

Dan, take a closer look at picture 7.21 in outdoor knots.
:o  Oooops!   ;)  (must be the muscle-building version!)

Good eye (and I don't recall noticing this).

Now, putting it to test/check with 12.5# barbell metal,
I conclude that "muscle-building" is it (the right way,
i.e.) !  --for which the answer might be that there is
a further part of the hauling system which gives some
MA (even "TTAMA" --"Tex's Theoretically Aware MA").


--dl*
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knot rigger

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Re: Break testing of the Alpine Butterfly Knot
« Reply #36 on: May 07, 2015, 02:28:09 AM »
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Dan, take a closer look at picture 7.21 in [Outdoor Knots by Clyde Soles..

There is a great article by Dan Chisnall in Knotting Matters 97 (i think it's 97, it's not in front of me) about carabiner hitches with is the best treatment of the alpine clutch I've seen in print.  Mr. Soles picture is mislabeled, but also is anchored into a webbing sling without a girth hitch.  The girth hitch makes the AC much more stable.

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particular questions re On Rope, 2nd ed.

I imagine the page about the figure 8 loop, and the page about asymmetrical prussics would be of interest to you.  Send me a private message with any requests and I'll scan and send to you.  I'd rather not post copyrighted material, but I consider private sharing "fair use"

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If anyone could provide me Mr. Richards testing, I would appreciate it.
Ah, it came out nicely, via Agent_Smith's hosting --voici

Ahh.. I have seen this before, I'm sure I saw it from a link here before.  My testing rig isn't nearly so fancy as this set up.  And, I've determined from the manufacture that using this style of dnyamometer for break testing is a no-no.  I'm trying to see if my work will buy the correct type, but for now break testing is on hold.

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I'm struck by "fabricated" : implying one's own making,
and not a (complete) "store-bought" product. !?

On the topic of the trapeze guy lines,  Yes, we did the splices in-house.. so we (I) fabricated them.  Here is a quick timeline of the saga as far a I remember from a few years back.  The original lines we're quite old (a couple years?) when they started to fail.  We had two fail within one week of each other, but it wasn't catastrophic.  One was found outside of a show when the measured tensions in the system we're too low.  And another was found by visual inspection.  We replaced all the lines with ones fabricated in the same way, with a tight cover, (tension balanced with the core at time of splicing).  This 2nd set showed the same bumpy birdcages within a few weeks, and we knew they we'er destine to fail like the first set.  We then made a 3rd set with the cover intentionally very loose, and they lasted a long time, over a year until I left the show after that, and they we're still doing fine.  For all I know, they may still be in use some 3 or 4 years later.

Two things may have been going on.  Vectran hates a tight bend, and in handling of these lines (especially the stiff handed first two sets) there may have been kinks that we're put in the core, that then became weak points where the rope eventually failed.  The other thought is that there was some friction between the core and cover that slowly wore through the weak points at the bumpy birdcages.  We we're using the vectran core due to it's low stretch, but then there was the polyester jacket that has a different way or stretching.  Perhaps the cyclical loading of the system was causing the jacket to stretch and rub over the core, which moved less that the jacket.  I'm not 100% on the cause of the failure, but I am 100% sure that putting slack in the cover made the bumps go away.

alpineer

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Re: Break testing of the Alpine Butterfly Knot
« Reply #37 on: May 07, 2015, 03:12:17 AM »
On the topic of the trapeze guy lines,  Yes, we did the splices in-house.. so we (I) fabricated them.  Here is a quick timeline of the saga as far a I remember from a few years back.  The original lines we're quite old (a couple years?) when they started to fail.  We had two fail within one week of each other, but it wasn't catastrophic.  One was found outside of a show when the measured tensions in the system we're too low.  And another was found by visual inspection.  We replaced all the lines with ones fabricated in the same way, with a tight cover, (tension balanced with the core at time of splicing).  This 2nd set showed the same bumpy birdcages within a few weeks, and we knew they we'er destine to fail like the first set.  We then made a 3rd set with the cover intentionally very loose, and they lasted a long time, over a year until I left the show after that, and they we're still doing fine.  For all I know, they may still be in use some 3 or 4 years later.

Two things may have been going on.  Vectran hates a tight bend, and in handling of these lines (especially the stiff handed first two sets) there may have been kinks that we're put in the core, that then became weak points where the rope eventually failed.  The other thought is that there was some friction between the core and cover that slowly wore through the weak points at the bumpy birdcages.  We we're using the vectran core due to it's low stretch, but then there was the polyester jacket that has a different way or stretching.  Perhaps the cyclical loading of the system was causing the jacket to stretch and rub over the core, which moved less that the jacket.  I'm not 100% on the cause of the failure, but I am 100% sure that putting slack in the cover made the bumps go away.

That's interesting kr. Rope manufacturers might be interested in hearing of this.

knot rigger

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Re: Break testing of the Alpine Butterfly Knot
« Reply #38 on: May 07, 2015, 05:42:40 AM »
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That's interesting kr. Rope manufacturers might be interested in hearing of this.

Hmm... It never occurred to me to tell the manufacture about it, we we're focused solely on solving the problem.  maybe I'll drop them a line.. too bad it was so long ago, if I had thought of it at the time I could have sent the broken bits into them.  alas

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I could suggest Outdoor Knots by Clyde Soles
(and w/help from ...   ) as a fresh, different treatment.

Dan, more bad news about Outdoor Knots I'm afraid :( re-read the section titled "coiling basics"  the paragraph beginning with "When coiling laid rope..."  (sorry I can't provide a page number, I have an ebook version.  BTW I should know better, knot books are always better in print, they always suck as an ebook)  So far the errata count is up to three items, and I haven't gotten half way through the book!

I do really like his section about rope construction, material choices, etc.  It's well put together.