Author Topic: Analysis of Bowlines paper uploaded for review and comment (PACI website)  (Read 109099 times)

Dan_Lehman

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   I did some rough and ready testing of the slack security...
   I tried a vigorous shaking of the knot for 30 seconds...

   I believe we should establish a few guidelines for such tests, otherwise we would not be able to compare and evaluate any results we may acquire from them. Anybody would be able to "shake" an eyeknot differently, and "see" different things - because, as we all know, most knot tyers wish so badly to "see" only what they had already convinced themselves they "know" ... :)
Oh, I assure you, I much wanted the EBDB to hold
that "Devil's material" small, hard-stranded,
slick, polypropylene cord that was sent to me
(in anger & disgust!) : when it didn't hold, on my
initial tying, I acknowledged only losing a battle
on account of lack of trying, and I re-tied, with
deliberately forceful setting --"THERE, take THAT,
ha!"  And it took it for a while, but only a short
while, and then . . . those turns around turns
--3dia each way, so nice-- all expanded.
(I might have uttered some curse, at that point.)

The same material, tied with a "Janus" bowline,
only worked loose-ish --the turNip expanded but
the "janus'd" bights tried and failed to open much
like scissors (instead of rotating), and more of a
workable knot remained.

But "horses for courses"; rockclimbing rope is not
so devilish --less slick, less springy, more compressible.
But one needs to set the EBDB's turns around
turns tight.  Those of the SPart will be heavily loaded
on a fall; but those that bind them (when slack),
of the tail, will be no tighter than manual setting,
and hence the key to untying.

Quote
A future situation, where we would have a few circumstantial, differently designed and performed, and subjectively evaluated "tests", can be worse from the present situation, where we have no tests at all !
It should not be bad but helpful, to some
degree, if the testing is well described --which
it seldom if ever is, alas.  (E.g., was Roo's rope
--Bluewater II-- new(ish)?  (All I have of that
brand is ancient and pretty darn intractable;
but I have some newer PMI "E-Z Flex" (which
is well contrasted with their regular which might
be aptly named "No-Flex"!   ;D  ) ) 

Quote
  1. What was "vigorously shaken" ? The Standing End only, or the whole eye-knot, the eye included ?
  2. Which was the angle between the eyelegs during the shaking ?
  3. Was the eye free to move/rotate around the wrapped object, or not ?
  4. Was the eyeknot pre-tensioned at the start of the shaking, and, if yes, to what degree ? Any shaking, however vigorous and prolonged, will not be able to loosen a very tight knot, of course - so we should not only certify that the compared eye-knots were tightened to the "same degree", but we should also decide/define this degree.
  5. An important element that should be always decided/defined, too, is the length of the Tail. I have seen that, during "shaking", the motion of the Tail influences the behaviour of the whole nub : a longer Tail, which is shaken along the rest of the knot, can help the nub remain more compact, for a longer time.     
   
  Also, we should describe the "shaking", with more precise terms. For example, we can specify the exact location of the point of the line, and the path and frequency of its repetitive movement, which induce this "shaking". I have seen that a "shaking" of the eye-knot by the Standing End, which involves short instances of pulling of this End, has a very different effect on the loosening of the nub, as it was anticipated.
Yes, if one grasps the eye and shakes,
there should be some compressive effects
that wouldn't come to the nub if the eye
were freely rotating around something.

But, in large measure, the tests are not needed
to exact some **degree** of security, but more
of a pass/fail check.  Even in the quite-different
material of that "devil's material", seeing the EBDB
loosen did give some useful information, a caution
to tying and so on.  (Maybe to use some further
extension, such as a 2nd collar & tuck.)


--dl*
====

knoeud

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Some good discussions going on here! :)

I think the fact is there are too many parameters in each test so that  we cannot extend or generalize any results to other situations.

That being said, my main interest is rock climbing and the falling situations with the Bowline knot. So the rope is a dynamic rope with a diameter between 8.9 and 11.

 As I understand the knot world, two main concerns are security and strength of the knot. I have used a Yosemite bowline for more than a year, climbing 5 hours a week. No surprise until now. Then I have recently switched to double bowline to improve the strength. Next step was naturally the EBDB to theoretically improve the strength using the 3 diameter system, but also improve the security with a tucked tail. 

SO it seems folks here are more and less OK with the strength of these knot variations and most of the discussion is on its security (for example in a shaking situation etc.). Frankly for me I can just make an overhand knot for the tail to secure it. However, I am yet concerned to find a STRONG variation of all these bowline knots that is easy to tie and un-tie.

SS369

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Quote
The most convenient way to observe the nature of the Scott's Lock Bowline capsizing event is to tie the knot in bungee or shock cord.  Elasticity seems to play a role.

Really? I believe this is a bit of a stretch. (Not just a pun.)

So, to investigate this I took a 3/8" bungee cord, tied the knot, stretched it to the point of no longer stretching (maximum elongation) and photographed it at that point. What I found is: The nub of the knot formed as all the others have, a tad more in areas perhaps. (The tail end bent forward more within the collar.) But, certainly no capsizing.

It still performed admirably to resist ring loading, both at rest and at full tension.
It did not untie easily, but did without the use of tools.

In simple fairness, I tied a Fig.8 loop (an accepted tie in eye knot) and found that it deformed almost to the point of being unrecognizable. (Needed duck billed pliers to untie it.) This proves to me that not all knots are suitable for All materials. Perhaps that is what you've been trying to say?

IMO, you must not be tying it well, or are tying it to fail along the lines of your claim.

* Is anyone else having this challenge?

SS

SS369

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Some good discussions going on here! :)

I think the fact is there are too many parameters in each test so that  we cannot extend or generalize any results to other situations.

That being said, my main interest is rock climbing and the falling situations with the Bowline knot. So the rope is a dynamic rope with a diameter between 8.9 and 11.

 As I understand the knot world, two main concerns are security and strength of the knot. I have used a Yosemite bowline for more than a year, climbing 5 hours a week. No surprise until now. Then I have recently switched to double bowline to improve the strength. Next step was naturally the EBDB to theoretically improve the strength using the 3 diameter system, but also improve the security with a tucked tail. 

SO it seems folks here are more and less OK with the strength of these knot variations and most of the discussion is on its security (for example in a shaking situation etc.). Frankly for me I can just make an overhand knot for the tail to secure it. However, I am yet concerned to find a STRONG variation of all these bowline knots that is easy to tie and un-tie.

Good day knoeud.

I too climb as frequently as I can. (Not nearly as much as I would love to!)
So far, it has not been proven that increasing the diameters within the nipping area does indeed increase resistance to breaking, but I am willing to speculate that it might.
In regards to climbing, I don't believe that you are going to exceed the breaking strength of your rope unless it is too old, damaged or some other influencing condition has been met. That is for you determine. Given those detrimental circumstances, any tie in knot will place you in more jeopardy.

If you like the bowline for a tie in, want a simple affair that has increased security (and possibly increased breakage resistance), ring loaded security, and ease of untying, I recommend that you give a few or all of the variants in Mark's (or others offered in the Forum) paper a safe try and get a feel for which one you like.

I personally have adopted and use the simple locked bowline that I have offered in the thread of that name.

SS

knoeud

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I recommend that you give a few or all of the variants in Mark's (or others offered in the Forum) paper a safe try and get a feel for which one you like.
Yep, I am doing this every other day! ;) which will simply determine which variation is a practical knot for me. However, I have developed some theoretical analysis of different knots over the years which I want to summarize in a bowline variation.

So far, it has not been proven that increasing the diameters within the nipping area does indeed increase resistance to breaking, but I am willing to speculate that it might.

I don't think any of our hypothesis will be proven any soon. However, I feel a stonger knot is the one with 
1.  with the least curvature (as has been mentioned in the documents), and less tight nip. As we speculate, the 3 rope diameter will do just that. SO I''ll want to have it.

2. Also I think it is not just the "the tighter the nip, the greater the chance the rope will break"
My hypothesis is that having the standing part out-side of a first loop will help to increase the strength. I haven't seen any documentation for this hypothesis. on this subject, the only close analysis I know of, appeared in "Knotting matters, vol. 7, page 3" regarding the outside curve of a Fig 8. I have attached a fig for clarity. The claim is that with outside curve of standing part (point x) for a fig 8, the knot is 15% stronger (limited test of course). So basically I think the same is true for a double bowline and may explain its strength. Therefore, I want the two loops too in my bowline knot.

3. The last concern is how to tuck the tail so that it is secure and also easy to tie.
I have no hypathesis on this one ;), so I will continue my tests. [remark: As of today, I and a group of people we climb with don't find the EBSB+Y very practical since the tail is not easy to pass through the both loops]



SS369

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Hello knoeud.

Since we are speculating, till further notice, I offer this. The simple locked bowline does indeed contain three diameters within the nipping area and so there is part of your search. The tail tucks easily and straight forward, easy to remember. Simple to do with your eyes closed even.

But, I have to wonder if the increased mass inside the nipping area allows too much rope movement and thus allows friction to build to a point where heat is substantially generated at extreme loadings. At lesser loads it may, and I believe it does, cause a cushioning as in the example of you've shown with respect to the Fig.8/Dbl Bowline.

As been said here in the Forum, "Any sufficiently complex tangle can resist untying, etc.) But at what cost in other effects.

So try a Dbl Bowline with a "simple lock" and see how that grabs your sensibilities. I suspect you'll find it more than robust enough and simple to boot.
I personally don't find it necessary for my climbing needs.

SS

knoeud

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Hello knoeud.

Since we are speculating, till further notice, I offer this. The simple locked bowline does indeed contain three diameters within the nipping area and so there is part of your search. The tail tucks easily and straight forward, easy to remember. Simple to do with your eyes closed even.

But, I have to wonder if the increased mass inside the nipping area allows too much rope movement and thus allows friction to build to a point where heat is substantially generated at extreme loadings. At lesser loads it may, and I believe it does, cause a cushioning as in the example of you've shown with respect to the Fig.8/Dbl Bowline.

As been said here in the Forum, "Any sufficiently complex tangle can resist untying, etc.) But at what cost in other effects.

So try a Dbl Bowline with a "simple lock" and see how that grabs your sensibilities. I suspect you'll find it more than robust enough and simple to boot.
I personally don't find it necessary for my climbing needs.

SS

Thanks SS369, I have actually tested your DB version since by default all knots I test are DB ;), but I need to gather the feedback of my friends too, will post  a summary of feedbacks soon.

in a related speculation, I have also been trying this EBDB modification of mine which is not a Y but tucks the tail nicely. Don't know if anyone has reported or tested this modification. Suggestions are welcome.

SS369

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You're welcome knoeud.

I'll look for your feedback in the upcoming days.

I can't fault your knot's end result (takes a bit more fiddling to dress and tighten, but hey we're knot tyers, and maybe harder to check for a novice), but,  if you are comfortable with using it, just test it some more under all the scenarios you could possible encounter. Close to the ground! ;)

SS

xarax

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   knoed, do not ask a farmer which one of his cows is better !  :) The Scot s TIB bowline ( left- and right-handed, shown, side by side, at (1)), is a much better eye-knot than the simple Scot s locked bowline ( which has this ugly sharp curve at its second/lower collar ) - and it is also TIB ! When you can have a TIB eyeknot, which has each and every of the advantages of a not-TIB one, and can also be tied in-the-bight following an easy to remember and quick tying method, why you would prefer the not-TIB version ? If you take a walk at the TIB bowlines area of the KnotLand, you will see that there is no reason to return back !  :)

1.  http://igkt.net/sm/index.php?topic=4517.msg30269#msg30269
This is not a knot.

SS369

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   knoed, do not ask a farmer which one of his cows is better !  :) The Scot s TIB bowline ( left- and right-handed, shown, side by side, at (1)), is a much better eye-knot than the simple Scot s locked bowline ( which has this ugly sharp curve at its second/lower collar ) - and it is also TIB ! When you can have a TIB eyeknot, which has each and every of the advantages of a not-TIB one, and can also be tied in-the-bight following an easy to remember and quick tying method, why you would prefer the not-TIB version ? If you take a walk at the TIB bowlines area of the KnotLand, you will see that there is no reason to return back !  :)

1.  http://igkt.net/sm/index.php?topic=4517.msg30269#msg30269

Uh oh, the Bovinator is striking again. :)

Quote
The Scot s TIB bowline ( left- and right-handed, shown, side by side, at (1)), is a much better eye-knot than the simple Scot s locked bowline ( which has this ugly sharp curve at its second/lower collar )
And what do you substantiate your claims that those are "much better"with? Put your life on a line use? Feeling?
Many knots have a sharp bend and so must be ugly as well.
If you are going to sell your cows, you'll have to do better.  ;)

Although being TIB is a good thing, it really has no use to the tie in procedure. PET is what is needed more so.
I am not claiming the simple locked bowline (the one I offered) to be the end all eye knot, but it is a simple locked version of the standard bowline. If the standard bowline works and someone would like a security enhancement that offers a resistance to ring loading as well, it fills the bill.

By all means test them all.

SS

Dan_Lehman

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I don't think any of our hypothesis will be proven any soon. However, I feel a stonger knot is the one with 
1.  with the least curvature (as has been mentioned in the documents),
and less tight nip.
As we speculate, the 3 rope diameter will do just that. SO I''ll want to have it.
It depends how the 3 diameters are disposed;
one needs to examine the SPart when it's heavily
loaded, nevermind anything else.

Doing that with a fig.8 might lead one to question
the broad-turn=more-strength theory, as there often
isn't such a broad turn to be found; rather, IMO, there
is something to the constriction around the SPart of
the eye-legs' U-turns (collars).

First objection is re "strength" : ropes don't break at knots,
experience shows, so how can some supposed strength be
important?  (And I recall an observation by one mariner about
damage after a hurricane severely stirred up a marina of boats:
some lines were in fact broken, but not at the bowlines (or eye
splices) (so, likely cutting effects came into play).  (Strength is
especially not relevant for abseiling --and yet some do mention
it!)

Furthermore, one must ask What is *strength*?!
--what is measured by a slow-pull device?
--or by a drop test?
--or by cyclical loading until abrasion proves fatal?
My surmise is that the last condition can prove a bane
for some knots that win on the first : precisely because
their SPart curves gradually over longer distance and
so has more movement during loading, there is more
friction-generated degradation in cyclical loading,
and ... the test device is shown to be a poor model
of practical concerns.  NB!

Quote
2. Also ...
My hypothesis is that having the standing part out-side of a first loop
will help to increase the strength.
//
The claim is that with outside curve of standing part (point x) for a fig 8,
the knot is 15% stronger (limited test of course).
Because ... ?!

The image you show is one I regard as absurd :
a) the supposed "outside" for the dbl. bowline is hardly
that --the doubled loop lies adjacent to, not around--;
b) the fig.8 image is ridiculous --and, yes, so broadly
used (what does that say about the users, AND readers?!)--,
as round-crosSection material will not hold such a pictured,
on-top-outside-of orientation.

Rather, in a properly dressed fig.8 one has one of
the parallel/twin parts reaching to the axial end of the
knot and when loaded bearing against its twin, or the
other part reaching less far and pulling away from its
twin and bearing into other parts of the knot (and it
seems to make a broaded turn --but look closely!).
(Most presentations of this knot family don't even
recognize the difference (and leave ambiguous which
end is loaded).)

I'll have to check what KM#007 (or nearby) says and who ...,
but my best information comes from Canadian climber and
IGKT founding member Rob Chisnall, who by illustration DID
seem to recognize the real difference in loading (and of the
proper setting --which he nicely illustrated), and his assertion
from some limited testing was a difference of --MIND THE
UNITS : % POINTS, not %-- 10 %-pt.s e.g. 70% vs. 60%,
and that for the loading of the end reaching farther and
pressing into its twin (which loading, btw, makes the knot
body assume more of a 45-degree angle to the axis of
tension; the other loading makes it more parallel).

Lyon Equip. did testing with this recognition but not so
much smarts about it in setting --i.e., I would want to
haul hard on the tails to impart more curvature to the
bearing-into-them SParts, for when push comes to shove,
the load on such rope will be WAY more than my setting
and should well challenge the curvature-inducement.
Lyon found some benefit to the overhand by this orientation,
but not with the fig.8; IIRC, the fig.9 might've been
slightly favoring the other way (but much variance),
and the fig.10 was maybe back to this way?

AND, to this, Dave Merchant opined that these more
complex knots (8-9-10) suffered more from dynamic loading
than did the simple overhand, which he presumed was
from the movement of rope and friction.

Quote
... don't find the EBSB+Y very practical since the tail is not easy to pass through the both loops]
I think that having the minimal body and then
TWO extensions to it makes a tough knot to tie.
Prefer the dbl (or water) bowline with double collars
--"Janus'd".  The 2nd collar helps keep the eye leg up
snug to the body (the collar of the SPart should be
left not-so-snug, to not so bend it), and arrests the
tendency of any rope from this side to creep in;
and without this assisted loosening, the feed into
the knot of the SPart, w/o ally, doesn't go far in
loosening : the knot stays tied, to hold the next fall.
(But each fall does move some rope, and this is something
to examine with some test of repeated loadings.)

Re this last point --of an untightly gripped SPart enabling
repeated movement in heavy loading, consider another
of my ventures to getting a secure-in-kernmantle tie-in:
the locktight loop, in which a structure somewhat
like the (multiple) strangle knot grips very tightly,
BUT has a *back door* that remains loosenable (whew!).

Let's see if this URLink works, to this forum:
OK - original sketches to get us started:



Russ
Understand that the exact number of overwraps is a matter
of judgement per circumstance, but these show reasonable
starting points.  Version II was hoped to be better with stiff
rope.  These knots are meant to be set TIGHT (in contrast to
the mirrored bowline which is shown too tightly set by Mark
--constraints of image space, I think--, and fares well enough
rather loose.


--dl*
====

roo

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The most convenient way to observe the nature of the Scott's Lock Bowline capsizing event is to tie the knot in bungee or shock cord.  Elasticity seems to play a role.
Here's are some pictures with the standing part shown (under tension) on the top of each picture.  The untensioned line is the free end.  Each picture shows a progressive step in the capsizing process.

(update: a variant that fixes this issue:  http://notableknotindex.webs.com/monsoonbowline.html)
« Last Edit: June 24, 2014, 10:54:32 PM by roo »
If you wish to add a troll to your ignore list, click "Profile" then "Buddies/Ignore List".


xarax

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ANY one of the many knots that have a sharp bend in its nub ( while it could well had avoided it ), is an ugly knot

  An nice example of such an ugly knot is offered by Dan Lehman in this very page : See the first/at the left of the two spring-based-shock-absorber-looking loops, shown in his recent post. ( By this, I do not wish to convey the false impression, that the second/at the right loop, is much prettier !  :) ).
« Last Edit: June 17, 2014, 02:22:34 AM by xarax »
This is not a knot.

knoeud

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It depends how the 3 diameters are disposed;
one needs to examine the SPart when it's heavily
loaded, nevermind anything else.
I agree.

Quote
Quote
2. Also ...
My hypothesis is that having the standing part out-side of a first loop
will help to increase the strength.
The image you show is one I regard as absurd :
My bad, the fig 8 is simply an illustration from KM007. Such a harsh statement towards the founding members of Knotting Matters Dan!!! ;)
Well an illustration is what it is "an illustration"!

the point is, Bill Marsh in his book "Modern Rope Techniques in Mountaineering" -
advises: ".....always ensure that the main rope lies on the outside of the first bend in the knot (see Point "X" in the diagram). If this is
on the inside, the knot is weakened." Alan WALBRIDGE has tested this for fig 8 and confirmed based on limited experience.

The interesting thing is that you never find a Fig8 (or other variations of it) in ABOK where the Spart is inside! Ashley has always managed to magically draw the Spart curve outside! in this world of internet this information has been lost and every other site and book illustrates this in a random in- or out- manner with no care!

I think the hypothesis holds for the bowline too.

Quote
I'll have to check what KM#007 (or nearby) says and who
Did you get one in its time? ;)


Quote
Quote
... don't find the EBSB+Y very practical since the tail is not easy to pass through the both loops]
Prefer the dbl (or water) bowline with double collars
--"Janus'd".  ... the knot stays tied, to hold the next fall.
(But each fall does move some rope, and this is something
to examine with some test of repeated loadings.)
As you know this is of major importance for sport climbing, which consists of repeated tries of the crux and thus Repeated falling and loadings!!

I will add the other knot in our climbing knots.
« Last Edit: June 17, 2014, 09:43:13 AM by knoeud »

knoeud

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Hey folks, anyone knows where Mark Gommers is??

I want to update his paper to include a summary of these discussions, so the pdf stays up to date!
I remember he provided the .doc at some point for people to update. anyone know where the source .doc is?