Author Topic: Non slipping bend in Dyneema  (Read 67159 times)

allene

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Re: Non slipping bend in Dyneema
« Reply #120 on: January 29, 2014, 11:38:57 PM »
Allan, Thanks for your effort in forums and your promotion of Anarchism.  Will You consider these two bends.  I would like to test if the continued bend is more secure than the bend not continued.

I tied both knots in a loop in Lash-it.  Both knots slipped at the same time and the one with the shorter tail let loose first.  Hope this is what you wanted to know.

xarax

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Re: Non slipping bend in Dyneema
« Reply #121 on: January 29, 2014, 11:49:20 PM »
   Luca had tied the BadBrother. ( See the attached picture, and a one-tuck-less version of it, at (1)). A nice Zeppelin-like bend !  :)
   Another "similar" bend is the Oval bend (2). 

 1.  http://igkt.net/sm/index.php?topic=4662.msg30153#msg30153
 2.  http://igkt.net/sm/index.php?topic=3741.0
« Last Edit: February 07, 2014, 12:43:34 PM by xarax »
This is not a knot.

allene

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Re: Non slipping bend in Dyneema
« Reply #122 on: January 30, 2014, 12:32:19 AM »
I tied several ball versions starting with the same basic lose configuration so I understand what you are saying.  What I am saying it that none of those forms are correct for what I intend the knot to look like.  There are many knots, I am sure, that have this issue although the only one I can think of is the luggage tag knot, you call it something that escapes me.  That can be tied around another line and then you can change it to a figure of eight.  Still an accepted knot.  What I am saying is that this knot can be tied and done so repeatably.  You can also tie it and make it come out wrong if you pull on the tails past the point of just sungging them up.

What I am saying is that my knot looks like the picture presented. If it looks like something else, it is not the same knot, it is something else.  You might notice that Ashley said the Carrick bend has a different name when tied a different way (Josephine).  All I am saying is the diamond knot looking arrangement you get if you tighten the knot from the tails is a different knot.  It might be stable, perhaps a better arrangement, don't know, but it is different.

BTW. Your Oval bend slips when compared to my first bend.  You should test them first. :-)

xarax

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Re: Non slipping bend in Dyneema
« Reply #123 on: January 30, 2014, 01:02:14 AM »
  Ashley said the Carrick bend has a different name when tied a different way (Josephine). 

  You are right, but you use the wrong arguments and examples !  :) Ashley does KNOT say this... :) When you tie, or even read about knots, you should be a little more careful... Read again what Ashley does say, and you will understand you cut too many corners...
  So yes, my opinion is that even two topologically identical knot can be different from each other, if they "lock" in a different geometrical form. Curiously, I was not able to persuade Miles about this... :). I believe that the fact that topology is a more basic property of shapes than geometry, and that Knot theory is a discipline of Topology, made him reluctant to accept this - and to miss the "bistable" knots. In an ideal world, with no deformation of the cross section and no friction, tensioned knots will settle in one, and one only, final form, where the rope length will be minimized. Just because of this, mathematical and ideal knots can only exist in "closed" forms, without ends.
  As I tie this knot more times, I begin to like it more ! It is very convoluted, for my taste, but if this is the price to pay to Dyneema, let it be ! However, personally I need to know how all the known simple bends behave when tied on this material, before I will accept the need for a tuck-tuck-tuck knot...And I will have to tie and try the other "decorative" maximally interweaved fig.8-to-fig-8 and Pretzel-to-Pretzel knots, to see how they fold when tied on so slippery a material...
   
« Last Edit: January 30, 2014, 04:57:47 AM by xarax »
This is not a knot.

allene

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Re: Non slipping bend in Dyneema
« Reply #124 on: January 30, 2014, 01:25:42 AM »
I am pleased you are beginning to warm up to my knot.  I will point out that if you want to know how all the known knots do in this material you are going to have to get a test setup.

You have presented may knots that I have tested.  All but one of them slipped far before mine.  The one that didn't slip, broke before the first bend.  And I would argue it was more complicated and certainly more difficult for me to tie, although perhaps that is from practice on my knot.  Although you think my knot is twist and tuck, or whatever you said, it is very easy to tie.

To undo it, you stick a marlin spike through the center and then pull the tails out (remove spike first).  The marline spike is particularly easy to stick through the knot there because there is a natural indent.  Mostly when putting a spike through a knot, it is very difficult and you risk sticking it through your hand.  Not on this knot, it is easy.

allene

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Re: Non slipping bend in Dyneema
« Reply #125 on: January 30, 2014, 01:50:59 AM »
I tested two versions of the tucked reverse Carrick bend.  One my first bend and the other a ball of twists formed by pulling hard on the tails.  The first thing I noticed was that the ball of twists capsized into another form so I am not sure what it is.  Then in testing, it slipped well before the first bend would have.   Conclusion, tying it wrong is not a good idea.

xarax

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Non slipping bend in Dyneema
« Reply #126 on: January 30, 2014, 02:44:04 AM »
  The great advantage of this bent ( except from the fact that it is symmetric, as it should be...), is that, although it needs 3 tucks, it is very easy to remember and to tie. Also, the fact that the not-yet-retucked knot is an alternative Carrick bend, with whch every sailor is familiar, makes its tying method even more convenient.
   If it will be proved that it does the same job, re. slippage and strength, with the triple fisherman s knot, it would revolutionize the tying of knots on Dyneema ! And if it will be proved that no simpler knot can do the same job ( which I still think it is very premature to claim...), the name of this bend will be written with gold letters ! :) I would t even think of tying a triple fisherman's knot instead of this, in applications where the wide spread tails / "ears" do not pose any problem.
   Even if it remains somehow "flat", as in the picture I had it shown in a previous post, it would not slip more easily than if it becomes more elongated. We should not forget that the Carrick bend is an already retucked knot - while the Zeppelin bend, or the Double harness bend, for example, are tied with one only tuck. So, the retucked forms of all the Carrick bends are quite complex knots, and do not slip easily.
   If Allen proves that the retucked "Classic" Carrick is much inferior to the retucked "alternative" one, as it seems he did, that would be very important - even if the knot itself will not be established.
   We should wait for more detailed tests, on bigger lines. I would like to see numbers for the 1/8" and the 1/4", and comparative tests of this bend and of the current industry benchmark, the triple fisherman s knot.
   Anyway, I am glad we can use this bend, too, as a benchmark, to continue searching for secure bends tied on this material, which nowadays has many applications.
   As it happened with many bends where the working ends are retucked through the central opening, the Tails can cross each other in two different ways. I prefer the form of the knot shown in the attached pictures, where the two large rims remain in contact along a longer arc, because the Tails do not pass in between them. However, those pictures are pictures of a bend tied on ordinary material, and only moderately tensioned - tied on Dyneema, the image of a loaded knot may well be slightly different - however, I do not believe that it will deviate much from the basic contour lines it already shows.
« Last Edit: January 30, 2014, 04:49:53 AM by xarax »
This is not a knot.

xarax

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Re: Non slipping bend in Dyneema
« Reply #127 on: January 30, 2014, 03:54:19 AM »
   Pictures of a simpler but somehow similar bend - because we had enough of all those complex bends that had filled the thread without any reason ! :)
   It is the Snug bend ( M. B11 ), which can also be seen as a modification of the falsely tied Hunter s bend :
   http://igkt.net/sm/index.php?topic=3204.msg19167#msg19167

   If the Snug bend is a good-looking bend - and I believe it is, indeed -,  I do not see why the retucked alt. Carrick bend of Allen will be not ! :)
« Last Edit: January 30, 2014, 04:52:54 AM by xarax »
This is not a knot.

allene

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Re: Non slipping bend in Dyneema
« Reply #128 on: January 30, 2014, 04:57:44 AM »
^^ Your photos of the First Bend, the one that opened this thread, look exactly like it always does when I tie it.  If find this classic shape easy to inspect so I can tell if it was done correctly.  I think I only did it wrong once and it was easy to spot.  The four parallel strands on one side, two full in the center and one half on each end along with the crossed strands on the back side are what I always see.  Nice job and great pictures.

The issues with the knot is that it can slip but it can also lock up.  It depends, I think, on how fast you pull it.  The numbers for slip were 35% on this and 40% on the variation where the tails come out parallel the the standing ends.  The knot looks the same by the way, when tied with the variation but it cannot be untied like the standard.  When pulled slowly, it was stronger but I would have to go back into the other thread to find the numbers.

Allen

xarax

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Re: Non slipping bend in Dyneema
« Reply #129 on: January 30, 2014, 06:01:55 AM »
  I do not understand why on Earth had you referred to a tying method of the asymmetric knot - when you were tying the symmetric ? ! ?
  All this time I was thinking and talking about the knot shown at :
  http://www.bethandevans.com/pdf/modified%20Carrick.pdf
  as you told us, at :
  http://igkt.net/sm/index.php?topic=4756.msg30712#msg30712
  It seems we had consumed many bits and bytes without any reason...
  Anyway, the symmetric knot is nice, indeed - and if it is adequately loaded, it does not retain this "flat" initial form it had in my first picture of the it, and it becomes much more elongated, and sleek. My problem is that, by using stiff and thick climbing ropes, and because I can not load them enough, for their size, I also can not force a complex knot s nub to shrink as much as I would had liked. Usually, in the case of simpler bends, even a knot that is lightly loaded, relatively to its size, takes a more or less compact form, which does not differ so much from the form of a more heavily loaded one. However, the friction forces generated inside this convoluted retucked Carrick are so great that, if the loading is not enough, the knot can remain "flat" for ever !  :)
   
« Last Edit: January 30, 2014, 12:22:06 PM by xarax »
This is not a knot.

allene

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Re: Non slipping bend in Dyneema
« Reply #130 on: January 30, 2014, 06:46:25 AM »
oops.  I did not catch that Estar had it wrong.  Makes me wonder if that is why it slipped for him and not for me.  Throws into doubt the data as well.  I wish I had a calibrated setup... 

Allen

allene

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Re: Non slipping bend in Dyneema
« Reply #131 on: January 30, 2014, 08:24:42 AM »
^^ Could it be that the same properties of the knot that make it hard to load are what is making it not slip in Amsteel?

By the way, that picture clarifies why I was having so much trouble getting my point across.  If you tie it like that, it does not have the nice properties I kept asserting.  I feel really bad about missing that.  I sent a note to Estar to see if that was the latest drawing and expect to hear tomorrow.

Allen

xarax

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Re: Non slipping bend in Dyneema
« Reply #132 on: January 30, 2014, 12:41:31 PM »
  Could it be that the same properties of the knot that make it hard to load are what is making it not slip in Amsteel ?

  Of course. ( On an ordinary material and under a moderate loading ) the fact that the tension induced from the Standing ends is already absorbed 100% before it reaches the Tail ends, proves that the friction forces within the nub are so great that the knot "locks" before it "folds", so it can remain "flat" and not become as compact and streamlined as we wish. On Dyneema and/or under heavy loading, it will fold before it will lock - but one has to tie it on Dyneema to see this, and I, for one, have not !  :)
This is not a knot.

allene

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Re: Non slipping bend in Dyneema
« Reply #133 on: January 30, 2014, 04:13:17 PM »
Here is a video of the knot being made in double braid accessory cord.  This should clear up a lot about the knokt.

http://youtu.be/o82mmdoIrvY

allene

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Re: Non slipping bend in Dyneema
« Reply #134 on: January 30, 2014, 04:26:06 PM »
Estar will be retesting using the correct knot this weekend.  We should be getting some better numbers.  I ran a test of the version on the pdf against my first bend and the correct way produces a much stronger knot as would be expected.  I hope you enjoy the video and will be interested in your comments.

Allen