Author Topic: Another Bend for Dyneema  (Read 921 times)

knotsaver

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Re: Another Bend for Dyneema
« Reply #45 on: August 07, 2017, 03:40:09 PM »
Hi Eric,

Quote
or what about the use of the #1459-1460 structure with Bowlines instead of seizings?
and #1457? :)
What leads you to think that the round-turns and half-hitches (1457), Whatknot (1459), or Whatknot and half-hitches (1460) would make a better central structure than a reef knot?  In my previous tests, two Bowlines eye-hitched (reef-knotted) together was unreliable.  Sometimes it held and sometimes it slipped.

Do you really see Whatknot there? I only see nipping loops! ;)
---

About your last post, do you think a Surgeon Bend will perform better than the Reef?
But above all, please try tying these variations (look at the attached pictures). They are based on a 3 nubs structure, two Standard Bowlines and the central part is formed by a 2 bights locking mechanism that bites/locks the 2 ends (after that we could retuck the ends through the nipping loops but perhaps the bend becomes too bulky...). We can tie the internal hitches close to the nipping loop of their loop, or close to the nipping loop of the other loop. I don't know which will perform better in Dyneema...
Here the 4 variations.
If the bends are not in tension the ends could not be so stable, we could add other turns (as in ABoK#523) or we could tuck the ends through the nipping loops or through the collars...
Ciao,
s.
« Last Edit: August 07, 2017, 04:25:07 PM by knotsaver »

NautiKnots

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Re: Another Bend for Dyneema
« Reply #46 on: August 07, 2017, 06:20:39 PM »
Do you really see Whatknot there? I only see nipping loops! ;)

Yes.  If you pull the two nipping loops of ABoK 1459 together (as will happen in Dyneema), then you get a Whatknot.  In fact, in the description, Ashley says "mechanically the knot is the exact duplicate of the Whatknot...".

Quote
About your last post, do you think a Surgeon Bend will perform better than the Reef?

No.  I previously tried the Granny / Whatknot as the central structure, hoping it would be easy to untie, but that idea didn't pan out.  The Reef Knot, however,  is easy to untie.  One can either pull the end bights apart (just like rolling the collar of a Bowline), or capsize the knot by tugging an end back.   A Ligature (Surgeon's) Knot would put a bulkier,  asymmetric structure in the center of the bend.  It should still untie easily by capsizing but I generally prefer symmetric bends to asymmetric ones.

Quote
But above all, please try tying these variations (look at the attached pictures).

Please don't take this the wrong way.  I really appreciate your interest and suggestions, but I can't try out every possible bend.  In addition to the time spent, each test takes about two dollars worth of Amsteel Blue, and I don't have a limitless supply.  I'm happy to conduct trials provided there's something to be learned, but I can't justify the expense otherwise.

Each of the bends you've pictured have nothing to prevent the Bowlines from capsizing, and they have nothing to secure the tails' tucks until the Bowlines are drawn together.  Those attributes make me highly doubtful that any of them will yield practical bends.  Given that, what do you hope to learn from testing them?

Sincerely,
Eric

knotsaver

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Re: Another Bend for Dyneema
« Reply #47 on: August 07, 2017, 10:19:57 PM »
Do you really see Whatknot there? I only see nipping loops! ;)


Yes.  If you pull the two nipping loops of ABoK 1459 together (as will happen in Dyneema), then you get a Whatknot.  In fact, in the description, Ashley says "mechanically the knot is the exact duplicate of the Whatknot...".


Eric, if the ends are seized, to my mind, the knot (the knot structure) works differently! But maybe I miss the point and I really don't know how the Dyneema rope works.

Thinking about  ABoK# 1454 and #1459 I tied the bend in the attached picture, surely it is a known knot and you can find other similar bends by searching the forum (for instance at
http://igkt.net/sm/index.php?topic=2871.0 )

I tied another bend based on ABoK #523, but it is a little bit bulky and I think it is untiable! maybe I will post in another occasion about fishing bends! :)

About your last post, do you think a Surgeon Bend will perform better than the Reef?
...   A Ligature (Surgeon's) Knot would put a bulkier,  asymmetric structure in the center of the bend.  It should still untie easily by capsizing but I generally prefer symmetric bends to asymmetric ones.
Sorry, here I meant a symmetric Surgeon, that is to say, double Half Overhand down and up.

But above all, please try tying these variations (look at the attached pictures).

Please don't take this the wrong way.  I really appreciate your interest and suggestions, but I can't try out every possible bend.  In addition to the time spent, each test takes about two dollars worth of Amsteel Blue, and I don't have a limitless supply.  I'm happy to conduct trials provided there's something to be learned, but I can't justify the expense otherwise.

Each of the bends you've pictured have nothing to prevent the Bowlines from capsizing, and they have nothing to secure the tails' tucks until the Bowlines are drawn together.  Those attributes make me highly doubtful that any of them will yield practical bends.  Given that, what do you hope to learn from testing them?

Sincerely,
Eric

I wrote "please try tying..." (not "please try testing") ;) , so if you consider them interesting you can test or not (it's up to you obviously)...oh I'm only curious and because I appreciate the power of the 2 bights locking mechanism I think the structures I showed could perform very well. About the instability of the ends if there isn't tension, we could tie the loops very short ( for instance just 2 rope diameters) and maybe we could only put the ends through the 2 bights without the internal hitches (maybe) ...

 I don't know the Dyneema rope behaviour (I repeat) and so I don't know why the Bowline capsizes, but a well dressed knot is of fundamental importance...I think you will agree with me.

Happy tying.
Ciao,
s.
« Last Edit: August 07, 2017, 10:25:31 PM by knotsaver »

NautiKnots

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Re: Another Bend for Dyneema
« Reply #48 on: August 08, 2017, 12:11:39 AM »
Thinking about  ABoK# 1454 and #1459 I tied the bend in the attached picture...

The knot pictured raised an interesting question:  if the tail is tucked through the opposing Bowline's nipping turn, do you need the central structure at all -- or are the Bowlines themselves sufficient to back each other up?  I thought that was worth trying, so I tied the bend (like ABoK 1454 but with mirror-image Bowline structures and with the tails passed through each other's nipping turn) and put it on the winch.  I tested it and under moderate load, the bend rolled apart.  Afterwards, I realized that I hadn't looked to see if the Bowlines had capsized, so I tried again.  The Bowlines did not capsize, but they rolled.  Thinking back, I recall much higher tension on the line at the point where Bowlines capsized.

Quote
I tied another bend based on ABoK #523, but it is a little bit bulky and I think it is untiable! maybe I will post in another occasion about fishing bends! :)
I look forward to seeing it.  I too was trying to evolve bends that involved each working end taking nipping turns around both its own and the opposite standing end.  Then I tried the 6-nips (3 Water Knots?) which worked and is much simpler.

Quote
I don't know the Dyneema rope behaviour (I repeat) and so I don't know why the Bowline capsizes, but a well dressed knot is of fundamental importance...I think you will agree with me.

Lol, I don't understand Dyneema rope behavior either.  I certainly agree that proper dressing is important, but I've also found that Dyneema can easily re-dress a knot for you, no matter how carefully and firmly it is set up.  The Double-Dragon Loop, for example (even when dressed and pulled as tight as I could get), capsized and failed at relatively low load when tied in Dyneema.  The Angler's (Perfection) Loop, on the other hand, has drawn up tight and secure to the same geometry (swallowing very little tail) every time I've tied it in Dyneema.  I've used it for the end loops in attaching to my test rig many times, so I've certainly exceeded the sample size needed for statistical confidence.  I feel that a knot must be "self-dressing" (that is, it must draw up consistently to the same geometry on its own) in order to be trustworthy in Dyneema.

Regards,
Eric

Dan_Lehman

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Re: Another Bend for Dyneema
« Reply #49 on: August 08, 2017, 12:46:44 AM »
Please don't take this the wrong way.
I really appreciate your interest and suggestions,
but I can't try out every possible bend.
Indeed, I was about to say the same thing.  Much of
what is put forwards here is just stupid --e.g., MY idea
for the further-tucked bowline should not have passed
"the smell test," in that --THINK, THINK, THINK!--
the SPart has 100% tension and multiple parts coming
out of the nub imply a split of tension further than the
50-50% normal for two eye legs, and THAT requires
more offloading via friction in the nipping turn than
one can expect w/HMPE (which has been shown to just
*flow* out through even the dble. turn of the double bowline
in one Brion Toss testing!).  BTW, a sort of water bowline
but w/cow vs. clove as the compound nipping structure
DID hold, to break (at what Brion thought was not great force,
but w/o calibration read-out to confirm).

So, one must first have a reasonable expectation that
the candidate knot brings something to the table not
seen in the many failures.

Now, the bowline variation where the nipping turn
is the cloverhand IS something new, in that it makes
a doubling of nipping structure in a way different than the
slipping dbl.bwl and maybe more sure like the holding
water(-like) bowline !?

And I've found --and will soon post-- an image to go with that
extended fisherman's knot I described, and which was tested
but MAYBE not quite in desired form?!  That knot brought to
the table the tucking of tail at U-turn of SPart --presumably
a heavily loaded nipping point.


--dl*
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NautiKnots

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Re: Another Bend for Dyneema
« Reply #50 on: August 08, 2017, 04:17:35 AM »
Much of what is put forwards here is just stupid...

Well, I'm willing to try ideas that may seem stupid as long as I can learn something from it.  After all, my experiments so far have disproved several of my own hypotheses about what makes a knot secure in Dyneema, and I'm sure that my current understanding is still flawed.  I can't explain why some knots roll under moderate load while others that look less secure hold at much higher tension.  High nip is not the answer.  Neither is complication (extra tucks), nor reversal (u-turns).  Jamming (backing up one knot with another) apparently plays an important role, but cannot be the sole factor.  I have a feeling that there at multiple interacting variables and that the real answer is too complex for conventional wisdom to explain.

I can see how tucking a tail through the center of a Reef Knot, and through the nipping turn of a Bowline might make them stronger, but it seemed strange to think that it might increase security.  I fully expected such tucking to make the Bowline less secure, and almost didn't test it.  But then I admitted to myself that I didn't really know the answer and tried it out.  The result surprised me.

Regards,
Eric

Dan_Lehman

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Re: Another Bend for Dyneema
« Reply #51 on: August 08, 2017, 09:11:03 PM »
Much of what is put forwards here is just stupid...

Well, I'm willing to try ideas that may seem stupid as long as I can learn something from it.
We should be advancing a rationale for WhyTestThis? and
what we think will happen.  That's a good way to put into
contrast the reality --so far as we can know it-- with the
beliefs.  --and a boon to learning from the efforts.

Attached are images for that extended fisherman's knot
discussed (& tested, like it shows?) above.

NB : The white rope stands in a mirroring orientation
to the illustration; the orange-to-black is in like orientation.
(And in both cases they are less helpful than the drawing.)

motto :: "HMPE, Abandon All Hope ye who try knotting this!"

Cheers,
--dl*
====
« Last Edit: August 11, 2017, 01:27:54 AM by Dan_Lehman »

NautiKnots

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Re: Another Bend for Dyneema
« Reply #52 on: August 17, 2017, 03:02:52 PM »
Is this what you mean by a "cloverhand bowline"?

I finally figured out how to tie a "Cloverhand Bowline".  I was looking at the Water Bowline (which is like a Double Bowline except that the nipping turns form a Clove Hitch) and didn't like how pull on the eye tends to separate the nipping turns.  In looking for a similar structure that pulled the turns together instead, I inadvertently came up with a knot that I recognized as a Cloverhand with a Collar, i.e. the "Cloverhand Bowline".  My previous efforts failed because I was tying the Cloverhand as shown in Ashley's diagram (running left-to-right, or downwards) when I needed to tie it reversely (right-to-left, or upwards).  With the standing end exiting from the bottom and the working end from the top, the Cloverhand does make a stable platform for a collar.

See the first image below.  It shows both sides of the "Cloverhand Bowline" (left and center).  The knot seemed to be crying out to have the working end tucked up through the collar (as shown on the right).  I doubt that the extra tuck has much (if any) effect on the strength or security of the knot, but it fills a gap in the collar and looks nice.

The second image below is the Double Bowline (front, back, and with the working end tucked through the collar) for comparison.  The two knots have a very similar appearance, but look closely and you'll see that the "Cloverhand Bowline" has an additional part on the side of the nipping turns.

I put "Cloverhand Bowline" in quotes because a purist might argue that this knot does not belong in the Bowline family.  It is not "Post-Eye-Tieable" (PET).

Anyway, I tried both the Double Bowline and the "Cloverhand Bowline" (with and without the collar tuck) in 3mm Amsteel Blue.  Both eye knots held (with little slippage during draw-up) in both configurations to their breaking points, which seemed similar.  I was able to untie them all without tools after loading.  The Double Bowline untied easily whereas the Cloverhand took some wiggling to let go.

Twin Double Bowlines (untucked) tied in the form of ABoK 1454 drew together under load and then jammed.  I was unable to untie them.

Twin Double Bowlines (untucked) tied in the form of ABoK 1455 with the eyes hitched (Reef Knotted) held without drawing together.  The nipping turns did not capsize, but one of them did pull through its collar, and I couldn't untie it.  When tied with the running end tucked through the collar, the knot seemed more resistant to pull-through.  I didn't perform enough tests to be confident, but in the few I did, the Double Bowline retained its dressed geometry.

Twin "Cloverhand Bowlines" (tucked or untucked) tied in the form of ABoK 1455 with eyes hitched (Reef Knotted) held without drawing together and seemed quite resistant to changing geometry. 

From a security/strength standpoint, the hitched twin "Cloverhand Bowline" bend seems the best so far, but the hitched twin collar-tucked Double Bowline bend is very close and is significantly easier to tie (the Double Bowline being PET) and to untie.  As an aside, the collar-tucked Double Bowline is also tiable in the bight (TIB).

I've come to the opinion that holding without drawing together under load is preferable.  You don't want a bend that starts moving once it reaches a certain tension, even if that movement is still secure.  First off, the bend may be somewhere you can't inspect it (like at the top of a mast), and secondly, movement may cause undesirable loss of tension (like in a halyard).  Therefore, I prefer these bends to my previous eye-hitched twin Bowlines with ends tucked bend.  All of them, however, take a fair amount of line to tie.  Given enough line, an end-to-end splice would be superior in every way.  I'd only tie a bend in Dyneema if something kept me from making a splice.

I hope that makes sense,
Eric