Author Topic: The definition of a loop  (Read 848 times)

agent_smith

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Re: The definition of a loop
« Reply #15 on: April 16, 2020, 05:00:06 AM »
per KC:
Quote
I'm sorry chilarity is part of things I've so much exercised to look past in force chase etc.
And yet - chirality is a real measurable property.
It exists - whether you choose to "look past" or not!

per Dan Lehman:
Quote
I expressly reference all this "helix" discussion and put
my point smack ON it.  To which I'm w/o reply.
I am replying...
In the first instance, there needs to be a definition of what a 'loop' is.
Secondly, a helix is a well understood geometric form.
There is ample scientific literature describing a helix.
The 'nipping loop' which exists as a component in Ashley's #1010 simple Bowline forms the basis of creating a helix.
That is, if the corkscrew rope geometry continued, it would would form a helix.
I conceptualize a 'loop' as being the initial base from which a helix can be created.

I have also looked to Harry Asher's 1989 publication: 'The Alternative Knot Book' - in which he introduces the concept of sense (which is in fact chirality).
Refer to attached images below...
Asher understood the concept that all 'loops' can have a particular chirality (which he also described as being left-handed or right-handed).

I note that Asher's understanding of chirality was not disturbed by any curvature of the SPart.
Rather, it is simply referring to the creation of a loop - which occurs when a rope segment crosses itself.
The descriptors; up, down, over and under are irrelevant for determining the chirality of a loop.

Note: Asher used the descriptor 'turn' to describe a 'loop'.
Asher appears to 'obfuscate' the terms loop, hitch and bight.
I find it difficult to extract a definitive explanation of each descriptor from his book.
For me, a 'turn' signifies that the rope will curve around a host and will be formed as a 180 degree U turn, a 360 degree turn and a 540 round turn (and so on).
Asher appears to conceptualize a 'loop' as the 'eye' of a #1010 simple Bowline or the 'eye' of a #1047 Figure 8.
What I conceptualize as an eye - Ashley regards as a 'loop' (same goes for Asher) - but they lived in simpler times with less pressing need to expand the science of knots.
For me, a loop has chirality while an eye does not.

Quote
Notably, I've not seen an answer as to how handedness
is assessed by A_S except for what he has published,
to which questions were put.
Indeed I have attempted to supply answers...it depends on how receptive you are willing to be!
I have already clearly stated that I see Ashley's #1010 simple Bowline as having Z (right-handed) chirality.
In other words, the 'loop' within #1010 has a geometry that is right-handed (Z).
The physical location/bending of the SPart does not disturb the chirality of the loop (ie nipping loop)..
If you lay a length of cord on a flat table, then curve that cord so that it crosses itself - you have formed the base of a helix.
If you continue spiraling that cord in the same direction, you create a helix.
If you flip it over (inversion) - it makes no difference to the direction of the spiral/curvature.

...

Quote
What I want to be seen is how the SPart's curvature
FITS the R-handed helix FOR A WHILE, HERE.

(But, then, as it comes back up *behind* itself
vs. "going away" like strands of a R-handed rope,
we have our problem; the outgoing eye leg DOES
reach away in that direction, but resumes a straight
path per tension; and in the case of ITS "initial turn"
--views as it comes INTO the turNip--, we have there
a rather too-hard a turn (or is it?).)
Its hard to extract a meaningful  understanding of your proposition without a clear diagram.
For instance, when your write; ..."Its (the SPart) initial turn"...
For me, it is irrelevant as to which rope segment is the SPart and which is the outgoing eye leg.
It doesn't make any different to the chirality of the loop.
When you take a length of cord and then curve it until it crosses itself - you have formed a loop (in fact a base from which a helix could be formed).
I am reluctant to assign concepts such a clockwise or anticlockwise to the direction of the spiral.
I prefer to use left-handed (S) or right-handed (Z) as descriptors to define the chirality.

I suspect that even looking for a dictionary definition of a 'loop' will yield no general agreement.
I found this:

LOOP (definition)
noun: loop; plural noun: loops
    1.
    a shape produced by a curve that bends round and crosses itself.
    "make a loop in the twine"

EDIT: Image quality difficult to obtain...should be reasonable now.
« Last Edit: April 16, 2020, 06:46:08 AM by agent_smith »

Keystoner

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Re: The definition of a loop
« Reply #16 on: April 16, 2020, 09:55:00 AM »
Dude, you're not seeing the big picture. Just ask Lehman--he's on a whole another level and he sees everything (that he wants to see ::)).
« Last Edit: April 16, 2020, 09:56:19 AM by Keystoner »

KC

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Re: The definition of a loop
« Reply #17 on: April 16, 2020, 09:56:40 AM »
It is not a factor in my search of force flow as definitions here.
More of the window dressing sometimes obscuring those things;
that i seek to look past, not to.  And have trained eye so.
Rope-n-Saw Life
"Nature, to be commanded, must be obeyed" -Sir Francis Bacon
We now return you to the safety of normal thinking peoples.
~ Please excuse the interruption; thanx -the mgmt.~

Dan_Lehman

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Re: The definition of a loop
« Reply #18 on: April 18, 2020, 08:56:00 PM »
Quote
I expressly reference all this "helix" discussion and put
my point smack ON it.  To which I'm w/o reply.
I am replying...
In the first instance, there needs to be a definition of what a 'loop' is.
Secondly, a helix is a well understood geometric form.
There is ample scientific literature describing a helix.
The 'nipping loop' which exists as a component in Ashley's #1010 simple Bowline forms the basis of creating a helix.
That is, if the corkscrew rope geometry continued, it would would form a helix.
I conceptualize a 'loop' as being the initial base from which a helix can be created.
But in which case one is effectively considering that latter,
and my point was to stand apart from that (we agree on
helical handedness, which quite matches that for laid rope).

Quote
Quote
Notably, I've not seen an answer as to how handedness
is assessed by A_S except for what he has published,
to which questions were put.
Indeed I have attempted to supply answers...it depends on how receptive you are willing to be!
I have already clearly stated that I see Ashley's #1010 simple Bowline as having Z (right-handed) chirality.
In other words, the 'loop' within #1010 has a geometry that is right-handed (Z).
The physical location/bending of the SPart does not disturb the chirality of the loop (ie nipping loop)..
(Why not ... YOUR images in this thread?)

How do you regard the handedness of #488 (if a joint
bothers you w/its two pieces of material --one a bight--,
then let's do the traditional make-an-eye-knot closing
of it by fusing the two tails --done) ?!

It's an example that sees a quite obvious helical
turning of the SPart out around the bight.
But you would call it ... opposite to this bending.
*I* want to focus on THIS part --"the initial turn"--
because I believe that to the extent there is some
physical/behavioral effect, it is significant HERE
(the 100% loading into the "nub"), irrespective
of later turns & twists and any *righting* of
handedness the opposite way.
   And to my point here:
Quote
What I want to be seen is how the SPart's curvature
FITS the R-handed helix FOR A WHILE, HERE.
For the important "while" of heavy loading.

Quote
I prefer to use left-handed (S) or right-handed (Z) as descriptors to define the chirality.
"Handedness" IMO best fits for practical rope/knots talk,
and for defining things   b y   t h e   h a n d s,  after all.

--dl*
====