Author Topic: Double Harness loop ( ABoK#1420)  (Read 17847 times)

Dan_Lehman

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Re: Double Harness loop ( ABoK#1420)
« Reply #15 on: August 18, 2012, 03:59:17 AM »
    It is as easily done for one side as it is for two... .

In your dreams, perhaps.
In certain practical situations as I hinted, it is quite not so easy.

--dl*
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TMCD

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Re: Double Harness loop ( ABoK#1420)
« Reply #16 on: August 18, 2012, 01:41:58 PM »
Dan,
I've kind of got the impression you don't like the Carrick Bend, any particular reasons for that or am I wrong in that assumption? I don't use it because in the field it's a pain in the butt to tie correctly and it almost seems to untie to easily if that makes sense. Are you a Carrick Bend fan?

Regarding symmetry, I don't think a bend needs symmetry to be secure and strong but it certainly is more pleasing to the human eye.

X1

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Re: Double Harness loop ( ABoK#1420)
« Reply #17 on: August 18, 2012, 02:13:19 PM »
I don't think a bend needs symmetry to be secure and strong but it certainly is more pleasing to the human eye.

   Symmetry assures that the distribution of tensile forces into the knot would be equalized, so, within each link of the bend, the strength limits would be reached at almost the same time. Otherwise, there would be a weak and a strong link, one would break much earlier than the moment the other would approach its strength limit - not an optimum situation. Of course, I am always talking about bends tied on the same, or on a similar material.

    It is as easily done for one side as it is for two... .

In your dreams, perhaps.
In certain practical situations as I hinted, it is quite not so easy.

   I have not described any particular practical situation - neither did you... Anybody that has, or will, tie a Double Harness bend, would see who is dreaming !  :) The two links of the Double Harness bend(s) can, very easily, tied apart the one from the other, and then they can, also very easily, be forced to slide on their two interpenetrating standing parts, until the tails kiss each other.
   I can't imagine why you do not see this!?  :)

Dan_Lehman

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Re: Double Harness loop ( ABoK#1420)
« Reply #18 on: August 20, 2012, 03:44:24 AM »
Dan,
I've kind of got the impression you don't like the Carrick Bend, any particular reasons for that or am I wrong in that assumption?
I don't use it because in the field it's a pain in the butt to tie correctly and it almost seems to untie to easily if that makes sense.
Are you a Carrick Bend fan?

I don't use the carrick bend so much, but have noted its
apparent calling for the hardy crabbers out of Alaska who've
been featured in the t.v. series Deadliest Catch --and noted
that they were shown tying it by means of forming one end
into final form and reeving the other into it (a more error-prone
method than what I call --and is commonly presented-- "the
lattice form with capsizing")!?  It wasn't clear whether they
took any precaution in further securing the tails (although
I believe that tucking the tails through the lay isn't an option,
as the rope is too hard-laid for that).  The one aspect of the
capsizing-the-lattice-form method that is problematic sometimes
is preventing the tails from slipping out or some uneven
capsizing with unequal ropes (stiffer joining more flexible).
(Otherwise, I find that method fairly failsafe for formation,
and pretty easily constructed, even though the capsizing
might take some minding.)

Quote
Regarding symmetry, I don't think a bend needs symmetry to be secure
and strong but it certainly is more pleasing to the human eye.

And this thinking I mostly concur in, and so have marveled
at the popularity of the butterfly ("strait") bend vs. #1408
& #1452 !?  Given that in joining ends one has no need
for the butterfly's TIB ability, why not take advantage of
that condition and tie a symmetric knot?
But so it goes!

--dl*
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X1

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Re: Double Harness loop ( ABoK#1420)
« Reply #19 on: August 20, 2012, 09:35:42 AM »
Regarding symmetry, I don't think a bend needs symmetry to be secure and strong but it certainly is more pleasing to the human eye.

And this thinking I mostly concur in

" [Symmetric] bends have the following advantages.
(I) There is less chance of mis-tying an SB, since any asymmetry is usually immediately apparent....Moreover, there is more likely to be an easily memorazable method of tying it, often symmetric itself.
(II) SB s are usually strong, since neither end is the weaker. That is, both cords in an SB have the same "strength", unlike asymmetric bends, for which inevitably one of the cords is the weaker, and hense the first to rupture under increasing load or tension. Hense, in general, SB a may be expected to be "stronger"....
   On these grounds one might claim that the "best" bends are symmetric."

Roger E. Miles, Symmetric Bends ( How to Join Two Lengths of Cord )
« Last Edit: August 20, 2012, 09:23:17 PM by X1 »

Dan_Lehman

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Re: Double Harness loop ( ABoK#1420)
« Reply #20 on: August 20, 2012, 07:23:18 PM »
Quote
[Symmetric] bends have the following advantages.
(I) There is less chance of mis-tying an SB,
since any asymmetry is actually--> usually immediately apparent
... .  Moreover, there is more likely to be an easily memorizable method of tying it --often symmetric itself.

(II) SBs are usually strong, since neither end is the weaker.
That is, both cords in an SB have the same "strength", unlike asymmetric bends,
for which inevitably one of the cords is the weaker, and hence the first to rupture
under increasing load or tension.  Hence, in general, SBs may be expected to be "stronger".

(III) From an aesthetic point of view, ...

   On these grounds one might claim that the "best" bends are symmetric.

Roger E. Miles, Symmetric Bends ( How to Join Two Lengths of Cord ), p.3 (Introduction)

Ah, good ol' REM !
Note the "usually" of his "I" ; I'm not sure I'd concur even
in this, but let's give that a nod of general favor.  (What any
one knot tyer realizes varies individually --and sometimes in
surprising ways (e.g., on this forum, and in another case on
a cavers forum, I recall presumed authorities making mistakes
re the fig.8 of all things!)

Re REM's "II", one could as much write "neither side is weaker",
but that misses the point of weakest link in knotting.
Still, in that I don't believe that difference in form necessarily
implies a dependable difference in strength (e.g., centuries on
and who knows which is the stronger side/half of the venerable
sheet bend  --X1, Knot4U, Roo, ... let's variously test THIS!);
i.p., in one dressing of the asymmetric, butterfly bend, both
sides look to take on good forms; their relative strengths might
vary with material, or possibly loading --and in any case be of
such slight difference as to beg the question of practical relevance.

Also, I think that in some cases (symmetric esp., but otherwise,
too) there can be what computer scientists call "race conditions" :
depending on details of actual loading, one side gets a *head start*
in tightening on the other (say, identically formed)  side (think
blood knot ), and therefore choke(nip)-impedes that SPart
from delivering force to its own choking turn, which enables
the head-start SPart to continue to deliver greater force,
exaggerating the imbalance in loading --maybe one SPart staying
pretty straight & un"deflected" in its tension, the other one
suffering curvature (ah, being "behind the curve"  ;) ) .

As for aesthetics ("III"), beauty's in the eye of the beholder!
(The "Rule of Thirds" is one of asymmetry.)


--dl*
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X1

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Re: Double Harness loop ( ABoK#1420)
« Reply #21 on: August 20, 2012, 10:55:51 PM »
...in some cases (symmetric esp., but otherwise, too) there can be what computer scientists call "race conditions" : depending on details of actual loading, one side gets a *head start*
in tightening on the other

 Good point - but even if this will happen in the initial phase or under light loading, later, at the final phase or under heavy loading ( near the strength limit(s) of each link ) the differences will be smoothed - because the rope(s) will "flow" inside the knot, something that could not have happened when the loading was still light. That is what I imagine that will happen - and that is also my understanding of what happens in the few videos I have watched in the net, of knots loaded near their strength limits. Of course, I am talking about slow tightening, where each part of the knot will have enough time to adjust and re-adjust its position inside the nub, and the distribution of forces would tend to reach a state of equilibrium. 

xarax

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Re: Double Harness loop ( ABoK#1420)
« Reply #22 on: July 19, 2014, 10:22:06 AM »
   Recent, better pictures of this loop.
This is not a knot.