Author Topic: Non slipping bend in Dyneema  (Read 67981 times)

allene

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Re: Non slipping bend in Dyneema
« Reply #30 on: January 23, 2014, 07:05:35 PM »
^^ It would help if there were instructions like in animated knots, or like the pictures Estar posted.

Dan_Lehman

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Re: Non slipping bend in Dyneema
« Reply #31 on: January 23, 2014, 07:13:49 PM »
   Thank you. You keep testing everything against your knot, and not against each other, and doing so you deprive us from valuable information
I made a loop of each knot and larks head knotted the two loops together.
 It broke at the larks head.
Please explain the eye-2-eye joint:
"larkshead-knotted" could mean
 (as it does in rockclimbing circles
   (where "larksfoot" seems embedded in UK jargon,
     from an old knotsbook error))
making the structure in one eye through the other
--which structure can, and often naturally does,
capsize into what resembles the square/reef knot--,
or that each eye is formed into said hitch
through the other (which is more difficult to tie).



Quote
One of the knots suddenly exploded and the test piece fell.

BTW, what sort of recoil are you seeing with this
very low-stretch HMPE line?  I know that you've been
cautioned about it and probably didn't need the advice,
but is this low-stretch material all so fierce?  --fierce
enough (!)? --or relatively benign?  Nylon, of course,
is rubberbandishly fierce.


--dl*
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allene

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Re: Non slipping bend in Dyneema
« Reply #32 on: January 23, 2014, 07:39:07 PM »
Larks head, Luggage tag, girth.  All depends on where you learned the knot.  I learned in kite flying

The Lashit is 500 pound rated.  It has no recoil but the staset I pull with snaps by me when things let go.  When I test larger line, I tie a safety line at the far end and it grabs the line. However, my normal test line is holding up my fence until the cement dries and I am using the safety lone as the test line.  Bottom line is the snap isn't great and it doesn't go where I stand.

allene

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Re: Non slipping bend in Dyneema
« Reply #33 on: January 23, 2014, 08:07:40 PM »
Can you post a picture or specific link to what you want tested?  The threads have variations.  O want to make sure I have the right ones.

Dan_Lehman

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Re: Non slipping bend in Dyneema
« Reply #34 on: January 23, 2014, 08:30:47 PM »
Larks head, Luggage tag, girth.  All depends on where you learned the knot.
I learned in kite flying.

But to the question : what do you mean by it?
Again, did you luggage tag one eye through another
--ONE eye doing the knotting, not both--;
or did both eyes form the whatever-called structure
through each other's structure's then-formed hole?

(To the naming, one can see some discrimination
between the cow hitch in which just one end is loaded,
and the girth hitch in which both are (perhaps most
frequently seen of shopping tags, and attachments
of round slings in climbing).
)

--dl*
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allene

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Re: Non slipping bend in Dyneema
« Reply #35 on: January 23, 2014, 09:11:10 PM »
^^ two loops are joined and the result looks like a square knot.  Call it what you want. Everyone calls it something different as far as I can tell.

Allen

allene

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Re: Non slipping bend in Dyneema
« Reply #36 on: January 23, 2014, 09:58:56 PM »
which one is the strongest and least likely to slip?

estar

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Re: Non slipping bend in Dyneema
« Reply #37 on: January 23, 2014, 10:50:36 PM »
after watching this thread, and pulling some of the suggested bends . . . my conclusion is that we will not find a "simple" bend that does the job in this material, and that we already have a solution that is better than a complex bend . . . Two EStar's tied together . . . does not slip, breaks at about 50%, is 'relatively' compact, and we all already know how to tie the buntline so it is easy to learn/remember.

 

SS369

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Re: Non slipping bend in Dyneema
« Reply #38 on: January 24, 2014, 01:57:44 AM »
Good day Allene and Estar.
Thank you for your interest and work on this.

I'd like to throw in a few possibilities for your search and testing. You can view these and their tying at this site http://www.southee.com/Knots/Knots_Bends.htm. The knots I am pointing to are #'s 17, 18, 20, and 22. Near the end of the page.

SS


allene

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Re: Non slipping bend in Dyneema
« Reply #39 on: January 24, 2014, 02:07:09 AM »
^^ those look promising and I think I have tested 17 and it does not slip.  It is nice to see a way to tie it that is more straightforward than the follow me method, which I found almost incomprehensible.  I will test these suggestions tomorrow along with the figure 8 knot previously referenced.

Allen

allene

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Re: Non slipping bend in Dyneema
« Reply #40 on: January 24, 2014, 03:06:19 AM »
I have 4 tests to report.  The above referenced knots.  I did not build #17 to see if it is what I already tested but #18, 20, and 22 slip against my knot.  I think #17 will not slip if it is the same knot I already tested. 

The figure of eight traceback knot, not sure which one I tested, was interesting.  Hard to call a winner.  At first, the figure of eight traceback slipped, then it locked up and my knot slipped and failed.  On another test, it was the other way around.  I am unable, with my setup, to pick a winner here.  My setup does a lot better when one knot fails easily, such as all the simple knots suggested.

Allen

Knot 17 slips at the same point as my knot.  The knot with the longest tails won.  I think it is worth further testing.
« Last Edit: January 24, 2014, 04:46:29 AM by allene »

Dan_Lehman

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Re: Non slipping bend in Dyneema
« Reply #41 on: January 24, 2014, 04:40:34 PM »
^^ two loops are joined and the result looks like a square knot.
Call it what you want. Everyone calls it something different as far as I can tell.

Allen

Allen, this is not really a matter of "calling":
it is a question of the fundamental geometry
of what this *knot* is that we're calling --however
we choose to name it!  And, no, actually, the result
--at least when used commonly in tape by rockclimbers--
doesn't always look like a square knot : sometimes
(and quite surprisingly seemingly most of the time w/KPowick!?)
it can stay as one sling girth-hitched to an eye
--the former collaring itself, the latter pure bight/eye!
(Kolin Powick did an examination of sling joints,
and to my amazement he had seemingly just one
pair collapse into the like-a-squareknot form!
Which form in this common case of slings, we should
observe, is asymmetric in shaping of the two pieces!)

Btw, I vaguely recall some old data sheet from one
of the then major rope companies stating that the
joint of two bowlines joined as you have done
proved stronger than if simply reeved eye through eye.
(And I'll surmise that in both cases the breaks came
at this joint, not in the bowlines.)


--dl*
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« Last Edit: January 24, 2014, 04:49:36 PM by Dan_Lehman »

Dan_Lehman

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Re: Non slipping bend in Dyneema
« Reply #42 on: January 24, 2014, 05:05:29 PM »
Knot 17 slips at the same point as my knot.  The knot with the longest tails won.  I think it is worth further testing.

The end-2-end knot I recommended above (post #47),
Ashley's #1408 (and simiarly his #1452, which is
more commonly presented) with the extended tucking
I describe
should hold.  Or else it will exhibit a new level
of rope fluidity, I think!  The draw of the two S.Parts,
turning jointly in one direction, should bind the tails
ever more tightly together; that even this structure
(which, note, stands in contrast to the opposite-directions
rotation in Shakehands, the #18 you tested)
could slip is understandable; but I think that one further
tucking of the tails through that heavily loaded central
nipping circle should see the knot draw up and lock.
(Maybe it will lock to the point of being hard to untie.)

Note that the aforecited on-line document gives
Ashley's #1452 / Ashley's Bend as its #3.  BUT
it gets the dressing wrong, or of an inferior form:
the tails as show in the red & blue diagram should
be dressed & set to cross in that relation,
not align abutting each other and not crossing
as the photograph of the completed knot shows!
(That version is also secure, but IMO produces a
less appealing curvature of the S.Parts, and will
not so readily feed into the extended tucking
that I recommend.)


--dl*
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estar

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Re: Non slipping bend in Dyneema
« Reply #43 on: January 24, 2014, 05:32:49 PM »
Allen asked me to test two things:

(a) One was a bend suggested above - it's number 17 here (Sennit Knot).  I am out of the amsteel at the moment so pulled it in endura braid (a very similar dyneema single braid)  it slipped at 815lb.  For reference I tested a double fisherman in this line, which slipped at 615lbs.  The slipping loads have quite high variability -  there is probably a significant difference there, but it is still only 29% of rated strength (Note: that is the loop load - the knot load would be about half - see comments below, but those are for dacron so the frictional effects would be smaller here)

( b ) The other was to test the breaking strength of the modified carrick bend in dacron line. I used stayset and tested the Zeppelin, regular carrick and modified carrick. These were 'straight pulls' and not loops.  If we set the Zeppelin strength at 100%, the regular carrick was 75% (significantly weaker than the Zeppelin) and the Modified Carrick was 105% (the same as the zeppelin).

While I was doing that, I did some extra pulls to provide a little test data toward the question that we have debated in the other thread, about frictional effects.  I did a 'straight pull' on the zeppelin, lets say that is 100% strength.  If I do a 'loop pull" (that is the line is a loop around two smooth pins tied with a zeppelin) it is 222%, you would expect 200% without any friction, so the friction of the pins is adding 22% 'protection' to the zeppelin weak point. When I do a 'loop pull' with one end cow hitched around one pin I get 232%, so 32% added 'protection' of the knot by friction.
« Last Edit: January 24, 2014, 05:36:24 PM by estar »

estar

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Re: Non slipping bend in Dyneema
« Reply #44 on: January 24, 2014, 06:00:24 PM »
The end-2-end knot I recommended above (post #47),
Ashley's #1408 (and simiarly his #1452, which is
more commonly presented) with the extended tucking
I describe
should hold.  Or else it will exhibit a new level
of rope fluidity, I think!

Well, then you will be able to learn something today . . . it slipped at 630lbs, about the same as the double fisherman I just tested (post above). 630lbs (27% of rated line tensile)  was the 'loop load', so the knot load would be (very roughly) half of that.  I have pictures . . . but they just show the tails sucking into the knot.

Just FYI . . . The knot as shown in your picture, without the extra tucks, slipped at 295lbs.

As I noted in a post above, the breaking results have very tight standard div's, but the slipping loads are much more variable.  My suggestion is that it is best to take the slipping loads as mere indications of 'high' 'medium' or 'low' slipping.  If I were doing 30 or 50 pulls each knot we could narrow the slipping mean, but I am only doing 3 or so pulls with these knots that slip so easily and clearly less than our benchmark knots.
« Last Edit: January 24, 2014, 06:11:30 PM by estar »