Author Topic: Mirrored Girth hitch bowline  (Read 11039 times)

Dan_Lehman

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Re: Mirrored Girth hitch bowline
« Reply #15 on: July 25, 2012, 07:24:33 PM »
   Here are two simple schematic drawings of the two ways we can pass the third ( the "3 ") rope segment through a nipping loop .( See the attached pictures).

Beautiful images, helpful to visualize what we've been considering!

But I would opt for the first with "3" moved one circle
anticlockwise --anticipating some draw upon these
by the heavy loading of the SPart, and some compression
of tail "3" to soften the *deflection* it makes in the SPart,
which continues past it to a harder U-turn at the next diameter.

Btw, I think it would help to show which of the others is
"1" --i.e., what comes loaded from the eye; and "2" is
then the "rabbit goes back into the hole(s)" passage.
"1" I surmise has firmer countenance which might have
bearing on its effect re strength & hence placement.

ORRRR, in the 2nd positioning, here I'd move "3" one circle
in the opposite (i.e., clockwise) direction, with similar thoughts
in anticipation of loading/compression/U-turning.

--something some heavy loading can begin to shed light upon
(and then break tests possibly show to be largely negligible!).


--dl*
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Dan_Lehman

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Re: Mirrored (aka Girth hitch) bowline
« Reply #16 on: July 25, 2012, 07:40:50 PM »
Quote
Would this knot really give much more security than say a double bowline with a DOH stopper? This just seems way to complicated unless you're one of us knot tyers.

To my surprise, I've more than once read of the strangle knot
(aka "DOH stopper") tie-off coming untied (!).  In one case, possibly
with knot-against-wall movements up a crack?  --and, we might ask,
oddly w/o notice of the then flapping-about untied tail!?
THIS mirrored bowline should retain its form more surely
than the one you suggest, which doesn't so much prevent
the SPart from feeding into the knot and loosening it (even
w/stopper secure, unless you've *Yosemite'd* the tail and
tied strangle'd the SPart snug to the nub).  But, many
things have been tried, and many have worked pretty well.


I was looking for the practical application.
With this monster (as the OP likes to say) taking up around 64 rope diameters ...

How did you measure it?  --something I did for some knots
way back, w/tedious thread or rubber-banding to mark the
points of exit from the "nub".  It's a nice datum to attach
to knots, possibly with some sort of other indicator that
would say whether the knot could be efficiently tied, or if
it needed beaucoup material to tie, even if it consumed
less in the nub once done.  (Maybe if I can find that note paper
on which I've some list of knots so measured, I can post it
and we can supplement it bit by bit for other knots (and
taking some 2nd-appraisals in various materials!).)

But, really, being on the order of the common fig.8,
and being something one would tie in anticipation of
taking a lot of falls --tying once, at the start of a climb,
or working of some "problem"--, it's worth the minimal
bother to be able to UNtie it when done --vs. having
to hammer a jammed knot into submission.  (YMMV with
how "lightly" you fall --the 110# lass vs. the 220# lunk.)


.:.  Think "RISK architecture" --a computer term indicating
processor design that favored doing many/repeated simple
tasks quickly vs. complicated/specialized ones, and which
seemed to rule the day in that.  In knotting, what might
be "complicated" in parts/crossings/ ... could yet be pretty
quickly & simply wrought by means of easy tying actions.

Here, IF one understands the working of a *bowline*
(we won't hold one to be able to define that!  ;) ),
it should be no big deal to understand the back'n'forth
extension to a commonly known (girth/cow hitch) base
--yes, it'll take (just) that much longer, but it's not a big
deal to do.  (The *slop* of it all --what can be, sans some
not inconsiderable time to dress-- might be offputting.)


--dl*
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« Last Edit: July 26, 2012, 04:40:27 AM by Dan_Lehman »

Dan_Lehman

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Re: Mirrored Girth hitch bowline
« Reply #17 on: July 25, 2012, 08:28:03 PM »
I would leave the collar around the SPart less tight.

   On the contrary, I believe that a tightly dressed knot, being more compact at the first place, right from the beginning - that is, even before its loading - is working better as one piece, one integrated whole. The tensile forces running within its elements would have a better chance be distributed into the whole knot s nub, to be absorbed by a greater portion of the rope segment, so  there will be less danger for an isolated small area to bear the full power of the loading, and to become the weak link - a guess !   

1) http://igkt.net/sm/index.php?topic=3951.0

To my eye (upon putting some real load onto such a construction),
the tightly set bowline makes for obvious serious deflection
at the crossing point of the collar and nipping loop,
instead of taking effectively no deflection at the first
point and a lesser one at the 2nd, delivering force
into/around the loop.

--dl*
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X1

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Re: Mirrored Girth hitch bowline
« Reply #18 on: July 25, 2012, 09:28:57 PM »
I would opt for the first with "3" moved one circle anticlockwise --anticipating some draw upon these by the heavy loading of the SPart

   Good point ! Thanks. My advice was that the "3" should not settle  to the position shown at the second drawing, near the crossing point - so it would be wise, indeed, to anticipate some rotation imposed by the standing part AND the by the eye-leg-of-the-standing-part... because, in this girth hitch nipping structure, both  nipping loops will draw all the three penetrating rope segments towards the same direction ( both clockwise, or both anti-clockwise).

I think it would help to show which of the others is"1" --i.e., what comes loaded from the eye
 I surmise [that "1"] has firmer countenance, which might have bearing on its effect re strength, & hence placement.

   I have no idea about this... This question, ( which should better be the "1", and which should better be the "2" ), is quite subtle, I believe - and it may even be proved to be too complex to analyse, at least for me. I had narrowed my investigation, and commented only on the simpler, more evident problem, the optimal position of the "3"rd / last leg, in relation to the position of the other two, and of the crossing point(s) of the nipping loop(s). 
   Speaking of the crossing point(s), I should like to mention another problem, that we encounter in the case of the Mirrored Water bowline. There, the crossing point of the first/higher nipping loop, and the crossing point of the second/lower nipping loop, are not aligned vertically - as they are at the Mirrored Girth hitch bowline. So, a penetrating rope segment that passes far from the crossing point of the first niping loop, would also pass near  the crossing point of the second nipping loop - a mess ! Moreover, as the two nipping rings would start to squeeze and compress the three rope diameters, the first leg of the first nipping loop ( the continuation of the standing part)  would "draw" the first rope segment it touches - and then all the others - toward one direction, while the second leg of the second nipping loop (the continuation of the eye-leg-of-the-standing-part ) would draw the same or another rope segment it touches, and then all the others, towards the opposite direction ! Even if the first effect will be more pronounced than the second - due to the more heavily loaded standing part- nevertheless here we do not have the cooperation we had in the case of the Mirrored Girth hitch bowline - so the amount of rotation of the rope diameters inside the nipping loops during the last phase of the loading, would be difficult, or even impossible, to predict in advance ... I have not said a word about the way we should pass the "3"rd leg through the nipping loops in the case of the Mirrored Water bowline, have I ?... :)

some heavy loading can begin to shed light upon
(and then break tests [would] possibly show [ the whole matter] to be largely negligible ! ).

  That is one of the reasons I have presented this matter the way I did  :) - commenting upon the Mirrored Girth hitch (B) bowline, shown by Mark Gommers !  :) I hope he will test those two variations someday, and he will report his results to us all.
« Last Edit: July 25, 2012, 11:31:09 PM by X1 »

X1

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Re: Mirrored Girth hitch bowline
« Reply #19 on: July 25, 2012, 09:48:19 PM »
the tightly set bowline makes for obvious serious deflectionat the crossing point of the collar and [the] nipping loop,
instead of taking effectively no deflection at the first point and a lesser one at the 2nd,
delivering forceinto/around the loop.

    How much a deflection is desirable - it may distribute the tensile forces to more than one point- , and how much it is dangerous - it may locally harm the material, and be the cause of the first cracking - is a subject I do not know anything about - but I guess it can be resolved only by detailed experiments. 

X1

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Re: Mirrored Girth hitch bowline
« Reply #20 on: August 19, 2012, 04:58:06 PM »
it would help to show which of the others is "1" --i.e., what comes loaded from the eye;

   In the case the arrangement of the three rope diameters into the nipping loop is the one shown at the attached picture, the location *3* should better belong to the *1*st rope segment that passes through this nipping loop, i.e, the eye-leg-of-the-bight.
   Two reasons :
   1. The leg that comes loaded from the bight has not formed a U-turn / a collar yet. Therefore, any nipping action on it, at this stage, would probably be wasted - the gripping force of the nipping loop would be unable to confront the full 50% of the load by itself. It is better if the greater part of the loading is first absorbed at the collar s rim, and the nipping loop takes action only afterwards -when the loading would have been already reduced at the collar quite a bid, and it would be much lighter for the nipping loop to bear it successfully.
   2. Each time, and at each point, the working end passes through - and is gripped by - the nipping loop, friction absorbes a great portion of the total tensile force. We can say that each one of those times and places is a line of defence of the knot, that protects the tail from slipping out of the nipping loop. It is better if those successional lines of defence are arranged according to the degree of their effectiveness, from the weaker to the stronger one. This way, under heavy loading, the most probable case would be the one where all those lines of defence would be utilized at the same time, i.e. the total load would be dissipated on the entire length of the line prior to the tail. So the segment of the line between the eye-leg-of-the-bight and the tail would participate in its entire length, and it would always be tensioned, : there would be no slack - a sure recipe for a tight, compact knot, with all its parts collaborating together in the effort of the knot to secure the tail from slipping out of it.
   So, when we have three rope diameters going through the nipping loop, it is better if the diameter that is located in the "blind spot" ( the location of the nipping loop where the working end is gripped less  effectively - the *3*, at the attached picture ) would be the one corresponding to the first  passage of the working end through the nipping loop - and so on.