Author Topic: Zeppelin Bend: Security and Strength  (Read 38853 times)

knot4u

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Zeppelin Bend: Security and Strength
« on: July 02, 2010, 06:57:55 PM »
We don't have much historical data on the security and strength of the Zeppelin Bend.  I opened this thread to talk specifically about the security and strength of the Zeppelin Bend relative to other knots.  This topic is discussed a bit in some other recent threads, but it wasn't the main topic.

Yes, this topic is wide open.  Further define the parameters, as you see fit, in your replies.

Some questions for discussion:
How does the Zeppelin Bend compare against other bends that are known for NOT jamming easily (e.g., Double Sheet Bend, etc.)?
How does the Zeppelin Bend compare against other bends that are known for jamming easily (e.g., Double/Triple Fisherman Bend, Figure Eight Bend, Overhand Bend, etc.)?

Here are some pretty cool stress tests on Zeppelin Bend:
http://www.youtube.com/watch?v=Givv9cBB_Hw&feature=related
http://www.youtube.com/watch?v=_-uQrx7yPYM&NR=1

I won't summarize the videos.  I'll let you watch!  ;)

Here's a source that shows tests results of the Double Sheet Bend, Double Fisherman Bend, Figure Eight Bend and some others:
http://www.xmission.com/~tmoyer/testing/High_Strength_Cord.pdf
http://www.caves.org/section/vertical/nh/50/knotrope.html

I have not seen a comprehensive test that includes the Zeppelin Bend versus other bends.
« Last Edit: July 02, 2010, 07:01:29 PM by knot4u »

Dan_Lehman

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Re: Zeppelin Bend: Security and Strength
« Reply #1 on: November 19, 2010, 07:37:57 PM »
."
   Dan Lehman replied that :
   "There is a noticeable difference of geometry if one orients the knot's tails in a certain way.  In the simple and commonly presented geometry, they align adjacent on the axis of tension, SParts making a 1-diameter turn around them; but in the version I intend, the Sparts turn more broadly, and that is what leads me to conjecture "greater strength".  Getting this orientation takes some careful placing of the ends and then careful setting --dressing AND setting are mindful acts."
   " In the disposition of the knots' tails, I see a trio [at least] of orientations for Rosendahl's bend ."

To which you might have taken your fingers off of the keyboard and endeavored
to discover these geometric variations (and maybe offer additional assessment as
to their *durability* over a range of loading/force).  Or do you think I made them up?
Schematically, the principal differences can be shown (font surviving
--oh, what we lose in non-ASCII! ) as below, the upper one showing SParts
surrounding cross-sections of tails oriented adjacent & parallel to tension,
with the lower one showing the tails oriented about 45deg to this, and so
giving the more gradual, stronger(?) curvature.

 ======\\
           O O
          \\======

 =====\\
           O\\
          \\ O
           \\======

Now, it could be that the issue is more subject to fine aspects of material,
and that what might look good at setting time will, when push comes to shove
towards a rupture force, be converted to the upper orientation.

Quote
I notice the telling absence of any mention to an erroneous previous claim
 ( that the Zeppelin bend feeds "generously" on its tails while it is been tightened ...

Which is hardly surprising (the absence, i.e.), as that wasn't the point of discussion (strength).
But, it is certainly the case that the result of tying can vary per setting method,
and esp. in some materials more so than others it is necessary to pull the ends
to draw the knot up properly --otherwise, one has what might be referred to as
some kind of "opposed Bowlines " structure, each SPart leaning firmily
into one side of its collar vs. passing less firmly across its center.

Quote
I can not help but to pay attention to the results of other peoples keyboard,
I have to say, ...

But showing this attention by mere regurgitation of those results gets us
nowhere --we have the original instance, after all.  (Though in some other
forums full copy-repetition is sometimes useful to preserve what is later
deleted --we don't suffer that problem (deletion) here.)

Quote
My theory is that, in the case of Zeppelin bend, the two tails (acting together, as a unified entity)
and the two loops of the overhand knots, function as a pivot hinge . Any subtle geometric
difference in this arrangement does not results in any noticeable difference of the bend s strength at all.

But that's a non-responsive theory given the presented fact of geometric variance:
either you have to demonstrate that the variance doesn't exist (or, as I suggest above,
exists in a sort of temporary & tenuous way only),
or you need to explain a theory of knot strength that makes the variance irrelevant.
Most of us are yet holding to some notion that curvature plays a role in strength
(though it might be less than we suspect, material variant (e.g., super slick stuff
not so much helped)), and so observations of effects on curvature rate at least
a worthy conjecture to the question.  Just saying "I don't think so" doesn't help.


Quote
Pulling the standing ends would do the job, and the Zeppelin bend will dress itself to some
 stable geometric form, that has nothing to do with the knot s strength.

This is demonstrably false.  I suspect that in your moderately slick, firm, round
kernmantle ropes it is much true; but there are other ropes, and perhaps especially
laid ropes (having their surface groves for friction) well *seasoned* in the field
will behave differently, as will stiff ropes.  This is readily seen with material in hand.

--dl*
====
« Last Edit: November 20, 2010, 04:41:12 AM by Dan_Lehman »

Dan_Lehman

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Re: Zeppelin Bend: Security and Strength
« Reply #2 on: November 20, 2010, 05:45:54 AM »
XaraX, you go beyond questioning to tiresome.
If you persist in screaming with your eyes shut tight, even the pretense
of a dialogue is gone.  I have tried to explain things carefully; it is something
others at least can follow and try themselves.  To the extent that I have
loaded the knot versions, they are different (and amply stable in their
differences).

As for that supposed uniqueness of Rosendahl's bend re the ends making
a "pivot point", we have already seen posted what belies that assertion
--the so-called "False Zeppelin", with same-handed Overhands.

--dl*
====

youngknot

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Re: Zeppelin Bend: Security and Strength
« Reply #3 on: January 17, 2012, 12:41:53 PM »
My interest in the Zeppelin Bend stems from explorations of failed bowlines.  Climbers all know to secure bowline bitter ends, especially with kernmantle ropes whose smooth surface can slip free when loads are intermittent, such as rocking moored boat or swaying trees.  In looking at Ashley, Butterfly, Hunters (aka Rigger's) and Zeppelin Bends, I am impressed that whereas the first and third typically can jam, and the butterfly bend can be sometimes shaken free, the Zeppelin excels in all these areas. I believe it is because among all four of these "two-overhand-linked" simple bends, it and the Hunter have bitter ends emerging against and opposite each other.  This I think means even loosely-dressed Zeppelin Bends, the moment a jerk is applied, press these bitter ends tightly and the ensuing friction prevents budging.
To this end, I am making directions so that one bitter end is employed as the start of a fixed loop, analogous to how the sheet bend becomes a bowline.  Writing the directions for TYING this (is it new?) loop were difficult, but are shortly forthcoming.  The resulting fixed loop I am just starting to test, but it seems to hold, loosely dressed, in 7 mm kernmantle rope, as a foot loop, being repeatedly jerked, it neither runs, jams nor unties.  This same rope and test done to a unsecured bowline often loosens and fails, as is all too familiar.  I am aware and do use the Yosemite finish on bowlines in non-test situations, and agree with its excellence, owing I believe to a similar factor as found in the Zeppelin: the bitter end emerges from the same loop as the SPart, and friction secures its position over all long-term uses.

Sweeney

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Re: Zeppelin Bend: Security and Strength
« Reply #4 on: January 17, 2012, 02:01:38 PM »
The loop from the Zeppelin bend is well known - see http://notableknotindex.webs.com/zeppelinloop.html for example. Personally I use the alternative method shown for both the loop and the bend (though if teaching the bend I would use the "b & q" method). The loop certainly seems secure and is easily undone.

Barry

xarax

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Re: Zeppelin Bend: Security and Strength
« Reply #5 on: January 17, 2012, 02:27:14 PM »
have bitter ends emerging against and opposite each other.

  The direction the tails point to after they leave the knot s nub, has nothing to do whatsoever  with the security or strength of the Zeppelin bend ( or of any bend...). We have dozens  of bends with a similar aspect...
   For the uniqueness of the Zeppelin bend in relation to the tails functioning as shear-forces-bearing pivots of a rope-made hinge, search for the terms "pivot","hinge", "shear" in this forum.
   The so-called  "Zeppelin loop", is a loop based on the topology only of the Zeppelin bend, but not on its mechanism / function. ( So, the name of this loop is, in fact, misleading ).  When a third end of the Zeppelin bend is loaded, the knot behaves in an entirely different way than the most symmetric original bend. The situation is similar with the bowline, where we can not speak of having a Sheet bend any more - because what we really have has a superficial only resemblance with the one link of the Sheet bend. When both ends of this link are loaded, as it happens in the bowline, we do not have a Sheet bend any more, we have a bowline !  :)
   Any secure bend can be transformed into a secure loop. There is no point of doing this with the Zeppelin bend or with any other bend, because we have dozens of secure bowline-like loops, which have the additional great advantage to get completely untied the moment you pull out the tail.

   
« Last Edit: January 17, 2012, 02:36:13 PM by xarax »
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[Inkanyezi] gone

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Re: Zeppelin Bend: Security and Strength
« Reply #6 on: January 17, 2012, 05:34:25 PM »
I am making directions so that one bitter end is employed as the start of a fixed loop, analogous to how the sheet bend becomes a bowline.  Writing the directions for TYING this (is it new?) loop were difficult, but are shortly forthcoming. 

I opened a subject on the board about a tying method for this in http://igkt.net/sm/index.php?topic=2146.msg15093#msg15093

If you, in the third image, imagine the end coming back to complete the knot, you have a tying method for the loop.
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[Inkanyezi] gone

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Re: Zeppelin Bend: Security and Strength
« Reply #7 on: January 17, 2012, 05:37:48 PM »
/.../   Any secure bend can be transformed into a secure loop. There is no point of doing this with the Zeppelin bend or with any other bend, because we have dozens of secure bowline-like loops, which have the additional great advantage to get completely untied the moment you pull out the tail.

Although I mostly agree on Xarax's post, I disagree on the last sentence. It is not always an advantage that a knot is very easy to undo by just withdrawing one tuck. The security of the Zeppelin Loop may well override this perceived disadvantage.
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[Inkanyezi] gone

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Re: Zeppelin Bend: Security and Strength
« Reply #8 on: January 17, 2012, 05:48:07 PM »
Here are some test results that go against conventional wisdom.  I just did some testing with the the Zeppelin Bend on fishing line, and the results were surprising.

Using 10 pound test monofilament, I tied a Zeppelin Bend in the same line as an Albright Special.  I used a magnifying glass to inspect proper dressing and started over if I thought a knot was dressed improperly.  I pulled the line on each end until something broke.  The line broke at the Albright Special.

I repeated this test 5 times and received the same result each time.  The line consistently broke at the Albright Special and not at the Zeppelin Bend or anywhere else.  By the way, the Zeppelin Bend jams up in 10 pound test monofilament.

I haven't done any actual testing of this very knot, but when I tested various knots in monofilament fishing line, I came to the conclusion that it is important to lubricate the knot when drawing it up. Fishermen often do this with saliva, wetting the line, so that it glides smoother till the knot sets well. Invariably I found knots that were not licked on breaking against one that was spitted on.
« Last Edit: January 17, 2012, 05:49:00 PM by Inkanyezi »
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xarax

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Re: Zeppelin Bend: Security and Strength
« Reply #9 on: January 17, 2012, 05:58:16 PM »
The security of the Zeppelin Loop may well override this perceived disadvantage.

   Perhaps I should have better said "convenience" instead of "advantage"...
   However, I insist that there are dozens of bowline-like loops that are at least as secure as the so-called " Zeppelin loop" - i.e. they will break before they will start to slip. What is the point of choosing in the first place and then using one out of the many bends-turned-into-loops, especially when it is now tied in a quite different, more complex way than the simple way we use to tie the original knot ?
   As much as I admire THE Zeppelin knot, the bend, I detest the so-called "Zeppelin loop"...It is like using gold because it is a heavy metal...  :)
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roo

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Re: Zeppelin Bend: Security and Strength
« Reply #10 on: January 17, 2012, 06:00:31 PM »
  Any secure bend can be transformed into a secure loop. There is no point of doing this with the Zeppelin bend or with any other bend, because we have dozens of secure bowline-like loops, which have the additional great advantage to get completely untied the moment you pull out the tail.
But those bowline variations are often less secure, or less stable in different load configurations, or harder to adjust, or harder to inspect for errors because they're a mess, or use more rope, etc.

Keep in mind that if untying the Zeppelin Loop (even with its final loose overhand knot) takes less time than prying apart a less jam-resistant loop, you are gaining something in this regard.
« Last Edit: March 05, 2012, 01:58:15 AM by roo »
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roo

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Re: Zeppelin Bend: Security and Strength
« Reply #11 on: January 17, 2012, 06:02:17 PM »
[on security]
 - i.e. they will break before they will start to slip.
This is NOT a good definition of security.  Nearly all knots are more vulnerable from slack shaking than from slipping at high strain.  Most knots never just slip out of the rope at high strain unless you're using exotic low friction rope at high loads.   
« Last Edit: February 19, 2019, 11:56:26 PM by roo »
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xarax

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Re: Zeppelin Bend: Security and Strength
« Reply #12 on: January 17, 2012, 07:26:07 PM »
But those bowline variations are often less secure
Noope. They are 100% secure, always secure... :)
But those bowline variations are...less stable in different load configurations
Noope. They are stable in each and every load configuration.
But those bowline variations are... harder to adjust
Noope. On the contrary, the so-called "Zeppelin loop" is quite hard to adjust...
But those bowline variations are...harder to inspect for errors because they're a mess
Noope. Many of them are symmetric, neat, easy to remember how to tie and easy to inspect knots. On the contrary, the so-called "Zeppelin loop" is so badly deformed  - in other words, is such a mess - ( because the one tail of the original Zeppelin knot is now loaded ) , that even the mother of the Zeppelin bend herself would not be able to recognize it !  :)

But those bowline variations ...use more rope
Noope. I have actually measured  their rope length, and I have found that quite the opposite is true !  On the contrary, the so-called "Zeppelin loop" uses almost the same amount of rope the bend uses, to secure one  only tail, i.e. it uses the same  means to achieve half of the task of the original knot - which is not exactly a definition of economy, is it ? :)
a less jam-resistant loop
Judging from their form alone, I suppose that there are many secure bowline-like loops at least as jam-resistant as the so-called "Zeppelin loop" - but I admitt I have not actually measured this quantity that is called "jamming"- simply because I do not know yet how  to measure it...

[on security] - i.e. they will break before they will start to slip.
This is NOT a good definition of security.  Nearly all knots are more vulnerable from slack shaking than from slipping at high strain.

   ALL knots are 100% vulnerable to be untied, if they are left loose enough, if that is what you mean...  :) For me, security=no slippage under high load, even near the breaking strength of the knot -  and strength=no breaking before the load reaches a high percentage of the breaking strength of the rope.


« Last Edit: January 17, 2012, 07:27:17 PM by xarax »
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knot4u

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Re: Zeppelin Bend: Security and Strength
« Reply #13 on: January 17, 2012, 11:01:34 PM »
   Any secure bend can be transformed into a secure loop. There is no point of doing this with the Zeppelin bend or with any other bend, because we have dozens of secure bowline-like loops, which have the additional great advantage to get completely untied the moment you pull out the tail.

Or you can just tie a Double Dragon.

roo

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Re: Zeppelin Bend: Security and Strength
« Reply #14 on: January 18, 2012, 04:58:49 AM »
But those bowline variations are often less secure
Noope. They are 100% secure, always secure... :)
But those bowline variations are...less stable in different load configurations
Noope. They are stable in each and every load configuration.
But those bowline variations are... harder to adjust
Noope. On the contrary, the so-called "Zeppelin loop" is quite hard to adjust...
But those bowline variations are...harder to inspect for errors because they're a mess
Noope. Many of them are symmetric, neat, easy to remember how to tie and easy to inspect knots. On the contrary, the so-called "Zeppelin loop" is so badly deformed  - in other words, is such a mess - ( because the one tail of the original Zeppelin knot is now loaded ) , that even the mother of the Zeppelin bend herself would not be able to recognize it !  :)

But those bowline variations ...use more rope
Noope. I have actually measured  their rope length, and I have found that quite the opposite is true !  On the contrary, the so-called "Zeppelin loop" uses almost the same amount of rope the bend uses, to secure one  only tail, i.e. it uses the same  means to achieve half of the task of the original knot - which is not exactly a definition of economy, is it ? :)
a less jam-resistant loop
Judging from their form alone, I suppose that there are many secure bowline-like loops at least as jam-resistant as the so-called "Zeppelin loop" - but I admitt I have not actually measured this quantity that is called "jamming"- simply because I do not know yet how  to measure it...

[on security] - i.e. they will break before they will start to slip.
This is NOT a good definition of security.  Nearly all knots are more vulnerable from slack shaking than from slipping at high strain.

   ALL knots are 100% vulnerable to be untied, if they are left loose enough, if that is what you mean...  :) For me, security=no slippage under high load, even near the breaking strength of the knot -  and strength=no breaking before the load reaches a high percentage of the breaking strength of the rope.

Wow.  All bowline variations are everything to everyone ::).  It makes me wonder if you even read what you write.
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