Author Topic: Non slipping bend in Dyneema  (Read 67155 times)

allene

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Re: Non slipping bend in Dyneema
« Reply #75 on: January 27, 2014, 04:54:53 AM »
Now that I am done with these bends I come back to questioning the first knot that I opened this thread with.  I just did two tests.  I tested the initial knot that I presented against the last knot.  They both started to slip at the same point.  That was the first time I had the last knot slip.  I paused 30 seconds and pulled some more.  Both held and the first knot won.

As the goal was ultimately to improve on the triple fisherman's knot I did a bake off on 7/64 Amsteel between the first knot and the triple fisherman's knot.  No contest, the triple fisherman's knot slipped and the first knot did not.

I have come full circle.  I like the knot I started with.  It has these advantages:  1) You can look at it and see if it is tied correctly.  2) It is a better looking knot. and 3) It can be untied after being loaded up.

The disadvantage is that it slips at some unknown value when pulled really fast.  But not as soon as the triple fisherman's knot.

Humm... 

roo

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Re: Non slipping bend in Dyneema
« Reply #76 on: January 27, 2014, 05:11:58 AM »
The average failure is at 39% of breaking strenght on a sample of 5.  This is a vast improvement over the triple fisherman's bend.  In the test, two slipped at 35% but held after a 30 second pause and went on to break at around the 39% number.  The fisherman's slip as low as 25% by comparison.

The test was done on 3/16 line and the average break was at just over 2,000 pounds on a straight pull which means a knot between two eye splices.

Improving on what was (is) the industry standard has to be good enough.  Thanks to everyone here for all the great ideas and coaching.

The failure was probably at the 180 degree bend and probably caused by the line compressing to less than 1 diameter.  It would have to stay at 1 diameter to reach 50%.
Forgive me if I missed it, but did you ever try the extended stevedore bend from the teflon floss thread?

« Last Edit: January 27, 2014, 05:15:02 AM by roo »
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allene

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Re: Non slipping bend in Dyneema
« Reply #77 on: January 27, 2014, 05:24:41 AM »
^^ I think so. I know I tested one dental floss knot.

I am going to repeat here that I am settling on where I started with the knot I submitted first.  When is slips in tests, it slipped at about the same point that the new knot does if not higher.  Test showed it slipping at 40%.  My test show it slips less than a triple fisherman's.  It can be untied and is stronger than the last knot if both knots are pulled slowly.  What's not to like.  So after dozens of tests, I am back where I started.  I am also done testing.  I found a knot significantly better in Dyneema than a triple fisherman's.  Easy to tie, can be untied.  Good enough.

Allen

Dan_Lehman

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Re: Non slipping bend in Dyneema
« Reply #78 on: January 27, 2014, 05:40:03 PM »
Two prusiks, as I have offered is not in the realm of the unthinkable, nor are they so complicated that one can not inspect them easily.

  No... but just COUNT the number of tucks and/or spins !  :)
When you go over 2, you return to your drawing board - until all really easy-to-tie
AND simple topologically and/or geometrically knots are exhausted.

The testers should be exhausted before any of this is
done; and we shouldn't be so stupid as to just toss
out another & another-like-it-but-different knot tangle
on hopes that by some magic it might work (although
it brings nothing, structure-wise, new to the test bed).
And we do want to have a knot that doesn't require
copious amounts of rope!

Re-tucked zeppelin?  They've already done #1408
(roughly) and #1452, which slipped without hinting at some
promise if only ... <slight revision>.  To these, though,
what I wonder about is the variation in which such
interlocked-overhands knots made the U-turn a turNip
--i.e., turn 360 degrees and collar thus the opposing
S.Part.  For there is some hint at least that the turNip
has some grip that can be enhanced by repetition.
(Recall that the in the Brion Toss videos one sees the
double bowline slipping, and a not-quite mirrored bowline
holding to rupture.)  I'd hoped that the cooperative
surround-&-nip-the-tails #14xx structures would get
sufficient nip esp. with the 2nd tuck; but maybe it's
the quick transfer of force that moves the 1st tuck
and thus quickly simultaneously is moving the 2nd
as well --no pause of stretching yield (and the movements
go in same direction, adjacent).  !?  <argh>

Roo has urged that offset fig.10, "stevedore" knot;
I wouldn't expect this to be at all strong enough for use
(breaking before some others slip?!), but the particular
nipping structure is something I'm trying to incorporate
into some other structure (such as the blood knot)
--and keep running into the makes-bulky/awkward problem.
--i.e., a sharp U-turn that nips the tail(s) enough to give
resistance that then enables the rest of the knot to
be tightened further.

HMPE is so slick but also so static that force gets
transferred/conveyed throughout the knot such that
it is frustrating the binding.  Contrast this with tying
the highly elastic physical-therapy tubing, where one
would need to deliberately haul hard on parts, and
possibly try to lubricate the material, even, so as
to deliver some setting force, tightening into the
full knot!
Then, again, I wonder if even should it suffice to hold,
would the blood knot with tails knotted jointly into
an overhand stopper prove to give too much movement
on in-practice loading on further tightening such that
heat then dealt a lethal blow?  But this is not a trim knot;
just maybe one that can do the work, in a pinch.
(NB: the blood knot can be tied so that the tails
exit together, same direction (what I have in mind for
the stoppering of the tails), or in opposite directions
(which I've seen done even though it amounted to
an asymmetric knot --a half-turn difference between
halves-- in some commercial fishing joining of heavy
(3mm?) monofilament nylon line.


--dl*
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allene

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Re: Non slipping bend in Dyneema
« Reply #79 on: January 27, 2014, 05:55:43 PM »
btw, here is my writeup. http://l-36.com/no_slip_knot.php.  Done, out of line, ready to move on.  I am sticking with the knot I started with.  Better than the triple fisherman's and can be untied.  I think that is a good thing.  Many of these retucked knots, including the somewhat stronger variation I show on this page, cannot be untied.

In terms of the Brion Toss video.  Rate of pull has everything to do with determining if these knots slip.  That knot slips if pulled quickly.  That pull was slow.  My modified water bowline does not slip even if pulled quickly.  Knots did not slip for me and slipped for Estar.  Testing is very subjective.  What is the goal.  My goal was a knot better than the triple fisherman's, easier to tie, and can be untied.  Achieved goal, time to move on.

Allen

xarax

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Re: Non slipping bend in Dyneema
« Reply #80 on: January 27, 2014, 09:54:07 PM »
HMPE is so slick but also so static that force gets transferred/conveyed throughout the knot such that it is frustrating the binding.  Contrast this with tying the highly elastic physical-therapy tubing, where one would need to deliberately haul hard on parts...so as to deliver some setting force, tightening into the full knot!

+1 ( :) )
This is not a knot.

allene

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Re: Non slipping bend in Dyneema
« Reply #81 on: January 28, 2014, 05:45:24 AM »
Retucked Zeppelin against my first knot with variation.  I used that because the Zeppelin double tucked would not be a knot you could untie so I wanted to compare like knots.  The zeppelin slipped.

OK, that was too easy.  So I did a loop with my first knot, the one that can be untied, and the double tucked Zeppelin.  the Zeppelin came undone and my first knot held.

It is unreasonable to test 80 knots when all the similar knots are not even close to strong enough.

Allen

allene

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Re: Non slipping bend in Dyneema
« Reply #82 on: January 28, 2014, 08:49:47 AM »
you claim that it slip less and/or it is stronger... Why

Because I tested it :-)

I do not believe that you can just add twists and tucks and create a knot that will not slip in Amsteel or your extended figure of eight would not slip.  That said, even the knot I presented slips if you pull it fast enough.  It just slips less.

We have a knot that does not slip in Amsteel that has been used for a long time and had very high loads put on it called a diamond knot.  My knot is a bend version of that knot.  That is why I started with it.  A diamond knot starts out life as a carrick bend and gets two tucks.  It doesn't work as a bend very well so I moved the tucks until I got a nice looking bend.

So what is the goal here?  It is not to test all possible combinations of two strings or even the known universe of bends.

Let's start this way.  I have proposed two knots.  One can be untied and one cannot.  One is slightly stronger than the other.  They are both stronger than the industry standard triple fisherman's knot which cannot be untied.

If you can propose a knot that is stronger and simpler than the knot I presented, I will test it.  THEN you can propose a simpler one that might be stronger and I will test that as well.  I am tired of testing weak knots.  Propose your strongest knot that is simpler than the one I proposed.  Your move.

Allen

allene

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Re: Non slipping bend in Dyneema
« Reply #83 on: January 28, 2014, 06:17:38 PM »
I decided to try your two knots but I cannot figure out how to tie them. I spent some time trying and colored one of the lines to help.  I googled the "Oyster Bend Knot" and found a link titled "how do you tie an Oyster bend.  It referred to Abok 1427, which was no help.  If you assert that these are simpler knots, you are going to have to show how to tie them.  If they are harder to tie, they are not simpler.

Allen

alpineer

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Re: Non slipping bend in Dyneema
« Reply #84 on: January 28, 2014, 08:11:26 PM »
Sir Xarax, it's well nigh high time for you to step up to the plate and begin testing these knots with the material in question. Allen has been doing so. What's your reason for not doing so yourself? Being the author of many suggestions proffered here, I think you're a most suitable candidate.
« Last Edit: January 28, 2014, 08:27:24 PM by alpineer »

allene

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Re: Non slipping bend in Dyneema
« Reply #85 on: January 28, 2014, 09:23:29 PM »
I found these pictures when I google the knot.  But I could not tie it.  As an example of instructions on how to tie a knot, let me show you what I posted for the knot I presented.

http://l-36.com/no_slip_knot.php

That is a step by step tutorial of how to tie the knot.  Contrast that with your ability to tie it given just the picture below.  And this picture is more open and I would say easier to follow than the pictures you posted.  I have some difficulty following which strand goes over some of the hidden strands.  I have to look at both the front and back to figure that out and as I can only keep three things in my mind at one time I get lost.  I ranked at in the top percentile group in tests on 3-d reasoning so I can imagine that  I am not the only person who would have a hard time.

« Last Edit: January 28, 2014, 09:33:13 PM by allene »

xarax

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Re: Non slipping bend in Dyneema
« Reply #86 on: January 28, 2014, 09:28:46 PM »
Sir Xarax

  A "free" man, but not a Sir ( or a Lord, or a Von, or a De, etc...) !  :)

What's your reason for not doing so yourself ?

  The most basic one : I can not ! :) I was not born to be an experimentalist... Perhaps having an idea of the talent this job requires, and the long, hard, lonely work which, most often, is not even conclusive, makes be reluctant to attempt it...You know, people can not do much different / dis"similar" things - do you know a car designer who was also a car driver ? An artist who was also a scientist ? Unfortunately, there were never many people like Fermi ( for example ( ? ? ) ).
This is not a knot.

xarax

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Re: Non slipping bend in Dyneema
« Reply #87 on: January 28, 2014, 09:35:21 PM »
   Allen, those are fine pictures, for KnotGod s sake ! Beautiful, clear pictures, that show the tying of this knot in a step-by-step, unambiguous way ! I would be happy if I was able to tie such knots, and test them, and take such pictures, at the very start of my knot tying pass-time ! 

    P.S. Two more old pictures of the Oyster bend. I do not have anything else in my files - if you wish, I can take new, decent pictures, but I have to wait the sun - which now is on your neck of the woods !
« Last Edit: January 28, 2014, 09:47:26 PM by xarax »
This is not a knot.

Dan_Lehman

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Re: Non slipping bend in Dyneema
« Reply #88 on: January 29, 2014, 01:19:25 AM »
In terms of the Brion Toss video.  Rate of pull has everything to do with determining if these knots slip.  That knot slips if pulled quickly.  That pull was slow.
Allene, do you recall what slipped --was it the
un-stoppered tail (making the usual single tuck
as for the water bowline), or the amazing eye-collapsing
flow-through of material seen in his dbl.bowline test?
For the former case, the mirrored bowline has the additional
tail tuck.  (Although I think you might've said that you tried
this one, as well.  Brion did NOT (at least not in that video).

Btw, I was happy to see either you or EStar remark over
in the SailingAnarchy thread that the stated allowable
range of rates of pull per some standard was HUGE
--and it has been put forward in the thread as though
it would resolve differences of results, egadz!

Do you have a known rate that we can keep track
of for reference?  (I don't think exact readings are
so important as a ballpark, roughly <this rate> vs.
<that rate> idea of what small/large differences of
rate show in results.  And as for rockclimbing loading,
you're surely well slower than what they'd experience.)


--dl*
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Dan_Lehman

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Re: Non slipping bend in Dyneema
« Reply #89 on: January 29, 2014, 01:29:47 AM »
   See the attached pictures, and, please, be a little patient. Our brain has not evolved to grasp 3D shapes, especially when we see only 2D projection of them !
Speaking for yourself, I'll accept this --"+1"  :P

But IMO the knot shown is riduculous to proprose
at this time of results shown by EStar & Allene --there
is way to clearly an easy slippage path for the well-rounded
turns and oblique tucks of this knot : I wouldn't expect it
to come close to holding.

THIS much analysis we should do before wasting away
one more precious bit of time, effort, & material.  Stop
and take stock of what has, what hasn't slipped (and
how!).  Re "how", we might be chary in some cases of
whether inaccurate tying allowed some transformation
of form --capsizing, such as can happen in normal materials
with the venerable bowline apparently (see the many
images of this in Knots in the Wild thread), or some
straightening of a part expected to by its curvature achieve
some effect.


Btw, Allene & EStar, on the slipped knots, are you seeing
any evidence of the material melting?


--dl*
====