Author Topic: Fisherman-knot-like bends.  (Read 5887 times)

X1

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Fisherman-knot-like bends.
« on: December 30, 2012, 06:50:51 PM »
   The Fisherman knot is a bend made by two inter-penetrating overhand knots. It is not the only such knot possible. At the attached pictures, see another one, and a retucked variation of it.
  I have re-tucked the tails of each overhand-knot link of the retucked variation through the central opening of the other link, but this was not necessary - the bend works very well in its simpler form, without it. The purpose of this re-tucking was twofold : to orient the tails so they become parallel to the standing ends, and to use them as a core to the overhand knots - so these overhand knots can not shrink further, and the first curves of the standing parts of the bend will remain as wide as possible. ( Of course, when/if tied on stiff materials, the overhand knots would have never been able to "close" completely - but now the additional presence of the bulk of the rope segments of the tails through their central openings can help them remain even wider than they would have been without this re-tucking of the tails.)

X1

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Re: Fisherman-knot-like bends.
« Reply #1 on: December 30, 2012, 06:59:39 PM »
   If we want to entangle the two links even further, and in order to shorten the length of the knot so it becomes more compact, we can cross the "spines" of the two Pretzel-shape looking overhand knots. See the attached pictures for the two similar knots that are generated this way. ( We can not speak about two inter-penetrating knots any more, of course, but of two interllinked overhand knots.)

Dan_Lehman

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Re: Fisherman-knot-like bends.
« Reply #2 on: January 03, 2013, 08:20:27 PM »
   The Fisherman knot is a bend made by two inter-penetrating overhand knots.
It is not the only such knot possible. At the attached pictures, see another one,
and a retucked variation of it.

It's what I call "pull-together" structure : each end ties
to the opposite some knot, and then they are pulled together
to lock.  Your first variation fits this, but then with re-tucking
and whatever the mess (!) is in the 2nd post you've gone
away from this notion into some heavy interlocking.

The fisherman's knot is also compact and nicely resistant
to abrasion, the way it doesn't have protuberances that isolate
some part to abuse.  Looking for other knots with this likeness
to the f.k. should turn up the blood knot, and ... !?


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X1

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Re: Fisherman-knot-like bends.
« Reply #3 on: January 03, 2013, 09:37:44 PM »
  Your first variation fits this, but then with re-tucking and whatever the mess (!) is in the 2nd post you've gone
away from this notion into some heavy interlocking.

  The "mess" is not anything different than what was already at the two last pictures of the first post - same knot(s), only shorter, and, of course, with more entangled links. However, I prefer to keep the notion of "interlocked" overhand knots for more "heavy" entanglements, so I have used the softer term " interlinked" ( the sequence goes like this :  inter-penetrating, inter-linked, inter-locked )
  As "inter-penetrating" knots I mean the knots where the standing end and/or the tail of the one/first link penetrates the other/second link, without any further entanglement that would offer more friction support to the whole knot - for example, without them being twisted around segments of the other/second link.
  Notice that this definition has no relation with the mutual position of the nubs of the two links relatively to their standing ends. The two links can be pushed or pulled the one on the other, but this does not change the way the segments of the one link are tangled with the segments of the other - which determines the characterization of the bend. Now, it may happen that the links of the "inter-penetrating" bends are always pushed against each other, indeed, but this happens only because the knot would not be secure if they were pulled the one from the other - the inter-penetration is a weak entanglement, by itself. It needs to be supported by the correct relation of the bulks of the nubs of the two links, so they will be able to form a secure bend.
   

kd8eeh

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Re: Fisherman-knot-like bends.
« Reply #4 on: January 08, 2013, 02:12:32 AM »
Some time ago, i described a knot as related to a fisherman's knot, and it appears to be the same as the knot you present here, albeit with one extra tuck of the ends to form a knot that twists as it is loaded (i believe i described it in a discussion of collars in knots).  Why is it that you said this was derivative of a zepplin knot moreso than a fisherman's knot?  I understand why you said it is zepplin-knot like, as it could qualify as a rope made hinge.

X1

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Re: Fisherman-knot-like bends.
« Reply #5 on: January 08, 2013, 03:24:42 AM »
it appears to be the same as the knot you present here, albeit with one extra tuck

   An extra tuck is too many !  :) At those simple knots, an extra tuck can change the whole thing dramatically, in form as well as in structure (loading).
   Please, specify/remind me which knot/thread you mean, because I do remember the issue, but not the knot or the thread... :)
   See the attached pictures, for some other Fisherman-knot-type bends, presented earlier in this Forum.
« Last Edit: January 08, 2013, 03:27:53 AM by X1 »

kd8eeh

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Re: Fisherman-knot-like bends.
« Reply #6 on: January 08, 2013, 03:32:04 AM »
I just posted it in springy knots; it does have some spring to it.  You're pictures explain what you are talking about very well.  Thanks.

Dan_Lehman

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Re: Fisherman-knot-like bends.
« Reply #7 on: January 14, 2013, 10:05:13 PM »
   See the attached pictures, for some other Fisherman-knot-type bends, presented earlier in this Forum.

I heard that there were photos of knots presented for
which I'd not given much (expressed) attention!    :D

My guess re strength is that in some of these cases,
where the SPart turns against a tail rather than directly
against the opposite SPart, strength will rise.  There are
also likely gains in security, and we can recall that in the
Dave Richards's testing the fisherman's knot slipped
in I think two of the three ropes.

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X1

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Re: Fisherman-knot-like bends.
« Reply #8 on: January 14, 2013, 11:33:42 PM »
I heard that there were photos of knots presented for which I'd not given much (expressed) attention!    :D

Rumours...Dont pay any attention to them !  :)

My guess re strength is that in some of these cases, where the SPart turns against a tail rather than directly against the opposite SPart, strength will rise.

   May be because some tension is dissipated/absorbed at those SP-to-tail contact points, before it is transmitted further. It is like we have a collar before the point the tension will be absorbed to 100%.
   However, we need/beg J.P to test all those conjectures - because knots are a veeery complex mechanical systems. The fact that they work, and, once tied, they work by themselves, without any further intervention by us, gives the false impression that they are simple things...but they are not ! That explains why we have not yet any computer programs able to simulate/predict their behaviour, although ALL buildings, bridges, and other man made HUGE ( in comparison to knot ) structures, are nowadays built after they have analysed and solved by computers - and ONLY BECAUSE they have been analysed and solved there. We would nt feel safe to step on a high-rise building or a long bridge if its integrity was based on pen and paper calculations, or guesses:)

Dan_Lehman

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Re: Fisherman-knot-like bends.
« Reply #9 on: January 15, 2013, 02:26:32 AM »
My guess re strength is that in some of these cases, where the SPart turns against a tail rather than directly against the opposite SPart, strength will rise.

May be because some tension is dissipated/absorbed at those SP-to-tail contact points,
before it is transmitted further.

I'm thinking of protecting the nipped SPart
rather than the bending one.  In one test of
8mm kernmantle tied around a 'biner in a
strangle noose it was the noose-SPart that broke
--at entry into the tightened strangle knot--,
not the turn around the (roughly 10mm) 'biner
or the knot's SPart.
(But I think that there was some other testing
of the same structure in thicker rope in which
the break occurred at the pin.)

In #1490-A, the SParts can/should draw their
nipped tails around the opposite SPart and so
pad (and broaden) that pressure point, whereas
this won't happen in #1490-B.


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X1

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Re: Fisherman-knot-like bends.
« Reply #10 on: January 15, 2013, 03:47:41 AM »
I'm thinking of protecting the nipped SPart rather than the bending one. 

( I include 4 other pictures of the same nots, for an easy comparison )

   In re.ABoK#1490 B, the (elastic) bulk of the tail works like a bunper, and can absorb some of the tension coming into the one s link curved section of the standing part, before this s,p. meets the other link s straight section of the standing part. This tell me that re.ABoK#1490 B would be stronger than the re.ABoK#1490 A. The tail "protects" the bending standing part of the one link, absorbing some of the tension it bears, before its dangerous meeting with the nipped standing part of the other link. Why you -are thinking we should seek the opposite, I can not understand... As I have said in the J.P. s  thread, do not be misled by where exactly the rope breaks ! Ropes and rods - loaded solid objects, in general - do not always break exactly where and when we expect them to break, at their weakest point or during the maximum loading. At least that is my understanding, out of the few things I know on this matter.