Author Topic: What defines a Bowline? - structure, characteristics, topology  (Read 124737 times)

knotsaver

  • Sr. Member
  • *****
  • Posts: 281
Re: What defines a Bowline? - structure, characteristics, topology
« Reply #345 on: April 01, 2017, 03:52:23 PM »
<
please, read my previous post first (at the previous page!)
http://igkt.net/sm/index.php?topic=3233.msg39594#msg39594
>
...

Re(-re)ading the old articles, I'm reminded of another point:
the **nub** matches that of angler's/perfection loop (#1017)
but one's ends are the other's eye legs (!).
( http://igkt.net/sm/index.php?topic=4480.msg38577#msg38577 )

Please look at the attached picture.
Same nub but different behaviour.
The Angler Loop is a nice eye, it is TIB, it is not PET, it is difficult to untie.
The (Lehman (Sorry Dan I continue to name it Lehman)) Locked Bowline is a secured Bowline, it is TIB, it is PET, it is easy to untie.
Does the PET quality of an eye imply easiness of untying it?

Worse misspelling than 'prussic' even, this 'PET' vice 'TIB' !!

Not all of my *bowlines* are PET or TIB (some are),
but the PET ones by definition are thus when attached
--to ANYthing!

Why do you say that, Dan?
Am I missing something?

Ciao,
s.
« Last Edit: April 01, 2017, 03:55:25 PM by knotsaver »

Dan_Lehman

  • Sr. Member
  • *****
  • Posts: 3719
Re: What defines a Bowline? - structure, characteristics, topology
« Reply #346 on: April 01, 2017, 04:19:30 PM »
Please look at the attached picture.
Same nub but different behaviour.
The Angler Loop is a nice eye, it is TIB, it is not PET,
 it is difficult to untie.
The (Lehman (Sorry Dan I continue to name it Lehman)) Locked Bowline is a secured Bowline,
it is TIB, it is PET, it is easy to untie.
Does the PET quality of an eye imply easiness of untying it?
No.
And "easy to untie" is a YMMV per materials, forces, & needs
--i.e., maybe the need is likely to be able to do so, possibly
w/help of tools.  I saw this knot (perfection/anglers loop once
in some commercial-fishing/-marine cordage lying about,
and it appeared that the knots were used qua mid-lilne eyes!?

Quote
Worse misspelling than 'prussic' even, this 'PET' vice 'TIB' !!

Not all of my *bowlines* are PET or TIB (some are),
but the PET ones by definition are thus when attached
--to ANYthing!

Why do you say that, Dan?
Am I missing something?
?!  "post-eye tiable" implies that one can --indeed,
that one MUST be able to-- tie the knot after attaching
the line to the <anything, including harness> .  Now, by
Agent_Smith's response, I see the *technicality* that
only the first eye can be PET-made but then one must
have the extant partially completed nub there when
making eye#2 (if not doing the jump-rope tying of taking
a twin-eye bight-end around the body and all!).

--dl*
====

Dan_Lehman

  • Sr. Member
  • *****
  • Posts: 3719
Re: What defines a Bowline? - structure, characteristics, topology
« Reply #347 on: April 01, 2017, 04:28:59 PM »
My point was that trying to form an attachment with #1080 to a climbing harness via the TIB method is problematic. I stated that is COULD be done - but, it would be a ludicrous process.
As I've recently (self-)triumphed in figuring out how to tie
a fig.8-(or 9-...)based eyeknot with just such a "jump-rope"
maneuvre, I will gainsay "ludicrous".  (My triumph : pull bight
up through smallish eye of e.g. overhand eyeknot and then
twist it a few times (damn nasty torsion creator, this) and take
it around the body :: point is, the resulting eyeknot canNOT come
untied sans reversing that, which isn't going to happen; and it's
unlikely to have the oh-eyeknot component come untied, either
(nor be heavily loaded, being the returning eye leg & tail both).
BUT, concern for this particular fig.8 structure is how it might
loosen, still-tied-topologically or not --that is a concern.

Quote
Dan, the 'Myrtle' (in my view) does have a collar.
Hmmm, then what eye knot does not have one?
I see out & back in-reverse (bight-forming) as a collar,
or as #1033 does though not actually "back in" (the rabbit
hole, nipping loop),
vs. out-&-around-in-same-direction, which makes for me
"loop" vs. "bight".

--dl*
====

agent_smith

  • Sr. Member
  • *****
  • Posts: 946
Re: What defines a Bowline? - structure, characteristics, topology
« Reply #348 on: April 07, 2017, 12:01:34 AM »
Quote
Quote

    Dan, the 'Myrtle' (in my view) does have a collar.

Hmmm, then what eye knot does not have one?
  per Dan Lehman

The nuances and complexities of language (particularly English) - makes it hard to capture every possible case - sort of like legislation (law) always seems to have loopholes and issues with interpretation.

Here is my understanding - based on many discussions, analysis and debates herein the IGKT:

A collar is a special structure in a Bowline. It has the following characteristics:
[ ] it performs a U turn around the SPart
[ ] it has an entry leg and and exit leg
[ ] the entry and exit legs are encircled and gripped/crushed by a functional 'nipping loop' (and the nipping loop is loaded at both ends)

Some qualifying remarks:
1. The common #1010 Bowline has a classically formed collar structure - a U turn around the SPart and the entry and exit legs lie in parallel. It is easy to recognize. Things get tricky where the collar structure is not classically formed.
In my view, the legs of the collar do not need to be in perfect parallel alignment - that is, they may cross each other (eg #1033 Carrick loop).

The nipping loop has been defined - it also has particular characteristics - such as tension force existing at both ends - when load is applied to the knot.

Example (thought experiment):
#1047 F8 eye knot does not have a 'collar'
1. There is no nipping loop in #1047...and therefore nothing grips entry + exit legs (because they dont exist)
2. The legs of a collar must be encircled and gripped by a nipping loop - again this does not exist in F8 eye knot
3. F8 eye knot is disqualified from being a member of the Bowline family - it has a completely different structure.

We can perform the same thought experiment on other 'eye knots'.
The test is:
1. Does the knot structure have a nipping loop?
2. Does the knot structure have a collar (which performs a U turn around the SPart and has 2 legs)
3. Are the entry & exit legs of the collar encircled and gripped by a nipping loop?

Summary:
1. The collar and the nipping loop are closely linked structures, each having distinct characteristics.
2. The collar always performs a U turn around the SPart and it has 2 legs; an 'entry' leg and an 'exit' leg.
3. The nipping loop encircles and grips both legs of the collar.
4. The legs of the collar do not need to lie in parallel - they may be crossed.
5. If there is no nipping loop, this automatically disqualifies a knot structure from being a 'Bowline'.

Mark G

Edited for clarity and to wrap up with a summary.
« Last Edit: April 09, 2017, 04:32:13 AM by agent_smith »

Dan_Lehman

  • Sr. Member
  • *****
  • Posts: 3719
Re: What defines a Bowline? - structure, characteristics, topology
« Reply #349 on: April 07, 2017, 10:24:56 PM »
Quote
If there is no nipping loop, this automatically disqualifies the structure from being a 'Bowline'.

But the recent question was re "collar",
and note that your def. of it requires a nipping loop,
which I think you might want to retract?!

In any case, as I said, I lean more towards bight vs loop
in seeing a collar vs. not.

As for "nipping loop", well, there comes the issue of any
significant tension to satisfy that "both ends" aspect; I
think that this'll be problematic (though I am sympathetic
to the assertion vs. sheet bend).

--dl*
====

agent_smith

  • Sr. Member
  • *****
  • Posts: 946
Re: What defines a Bowline? - structure, characteristics, topology
« Reply #350 on: April 09, 2017, 04:38:52 AM »
Quote
But the recent question was re "collar",
and note that your def. of it requires a nipping loop,
which I think you might want to retract?!
  per Dan Lehman

No retraction required.
The collar and the nipping loop are separate structures - with each having its own distinct characteristics.
Possibly confusion caused by the 'relationship' between these two structures within the Bowline.

Some Bowlines do not have classically formed collars (which includes both legs).
An example is #1033 (Carrick loop).
The nipping loop is easy to see in #1033.
I suspect that the collar structure is not so obvious to some observers - and so it is dismissed as being a 'Bowline' variant.
« Last Edit: April 09, 2017, 04:39:23 AM by agent_smith »

knotsaver

  • Sr. Member
  • *****
  • Posts: 281
Re: What defines a Bowline? - structure, characteristics, topology
« Reply #351 on: April 10, 2017, 04:50:57 PM »
Does the PET quality of an eye imply easiness of untying it?
No.
And "easy to untie" is a YMMV per materials, forces, & needs
...

Yes, but the geometry and the way the knot is loaded are important factor for instance

I saw this knot (perfection/anglers loop once
in some commercial-fishing/-marine cordage lying about,
and it appeared that the knots were used qua mid-lilne eyes!?

I think in that way the perfection/anglers loop perhaps is more easy to untie, because by loading the other end the nub doesn't jam as in the normal case (without loading the other end).

"post-eye tiable" implies that one can --indeed,
that one MUST be able to-- tie the knot after attaching
the line to the <anything, including harness> .  ...

ah, ok, I had misunderstood. Thanks.

Ciao,
s.

agent_smith

  • Sr. Member
  • *****
  • Posts: 946
Re: What defines a Bowline? - structure, characteristics, topology
« Reply #352 on: October 17, 2017, 10:29:51 AM »
Just posting some comments from Xarax re the 'collar'.... as his 'proxy'.

Email received from Xarax
Quote
The nipping loop is the primary characteristic, indeed - but we should not underestimate the role of the collar , the "proper" collar (  the "invention" of the collar sealed the fate of the bowline s development. It was as ingenious a step as the invention of the nipping loop ). Those Myrtle+stopper "bowlines", for example, are not bowlines enough ! 😉☺ The "proper" collar, which collars the Standing End ( standard bowlines ) or the ongoing eyeleg ( "Eskimo" / anti-bowlines ), seems a much simpler, and much more advanced solution. The Myrtle "collar" is a "link", not a "proper" collar.

Proxy posters comments:
The white background images are mine...thought I'd add them for further clarity...

Edit: Outdated image corrected...
« Last Edit: October 17, 2017, 11:15:23 PM by agent_smith »

KC

  • Exp. Member
  • ****
  • Posts: 185
    • latest project
Re: What defines a Bowline? - structure, characteristics, topology
« Reply #353 on: October 19, 2017, 12:54:46 PM »
Quote
I have to go with what DerekSMith said. One of the fundamental aspects of a bowline is the inclusion of a Sheet bend.
"...
In my personal view, there is no functional nipping 'loop' in a Sheet Bend. And the Sheet Bend is not an eye knot.

And this comes back to what is the definition of a 'loop' (and indeed...what is a 'nipping loop'). I had required that the nipping loop must be loaded at both ends in order to qualify. In a Sheet Bend - the nipping structure is not loaded at both ends...and so it is not a 'nipping loop'.
..." Mark Gommers   
.
i think though, loop draws close just the same, powered by same SPart;
just Sheet has a stop, Bwl draws thru but  to only half load on other side, other half is on other side of eye, trying to escape choke of nipping loop *.
.
Kinda same structure to start, with forces flowing thru differently;
>>Sheet would have fully loaded tail trying to escape nipping non-loop  vs. Bwl only half force tail trying to escape
>>both instances have same key deformity in SPart
.
The re-route of force does allow forming eye for Bwl as it's added innovation
>>but i do believe it inherits some structure and properties from Sheet Bend
.
i do have a hybrid, been playing with, and will draw out over weekend; have tested it out even more with hurricane work of late; and it has been a good friend.
i see the common deformity loading as the problem strength/efficiency wise.
And some pictures here show softening it as 1 route;
but i try to offload/re-route some of the force around the deformity instead with basically coils around SPart from tail to carry part of finite load that route, around major deformity of nipping loop.
.
edit:


.
Seems in well dressed form:
Left half of eye-load carries on 'spiral' routing around nipping loop (below it)
>>would seem if nipping loop is still major deformity/ defining weakness:
>>if half loaded on that leg of eye support, would only have half the in-efficiency(?)
.
Seems also that nipping loop could pass some load to spiral w/o fully routing thru major deformity of nipping loop
>>especially if upgrade nipping loop to RT.
.
Seems forces tracing thru spiral grips SPart above major deformity and perhaps stabilizes that area as load forces re-join to SPart.
Spiral ('linear RT'?) seems would add some extra dynamics to line
>>but would also seem spiral area stiffens area of line and easier to leverage against line on some occasions possible
>>this would be for eye connection, not running bwl.
.
i always look to compare lacings to base lessons of things like this to basics of Square/Sheet/Surgeon's etc. ;
this design shows the pull across loaded SPart as Sheet vs. pull along SPart like Surgeon's from either side of the eye!
.
Normal Bwl all eye loading forces trace  thru and combine at major deformity nipping loop to then transfer to SPart.
i favour several other forms of lacings with the 'spiral' / 'linear-RT' build in slings and other eyes.
.
*Sheet vs. Bwl Nipping is Hitch vs. HH ; perhaps even different forms of HH?
>>And in end, both hand over full force load to SPart at the same most deformed part of highest loading and changes/impacts.
« Last Edit: October 27, 2017, 03:56:48 AM by KC »
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.~

SS369

  • Global Moderator
  • Sr. Member
  • *****
  • Posts: 1788
Re: What defines a Bowline? - structure, characteristics, topology
« Reply #354 on: November 05, 2017, 05:54:38 PM »
Hi KC.

You may be interested in this thread. > http://igkt.net/sm/index.php?topic=4283.0 It has some variations on the theme.

At one time I did an adhoc test, tug of war style, using the braided bowline against a simple locked (mine) version of the #1010 using 6mm rope and the braided specimen was the loser. It broke at the location where the sp entered the nipping area. I had hoped that some force would have been dissipated along and through the braid weave. It is very secure though, just not as efficient of rope use as other eye knots.

SS

KC

  • Exp. Member
  • ****
  • Posts: 185
    • latest project
Re: What defines a Bowline? - structure, characteristics, topology
« Reply #355 on: November 15, 2017, 12:08:52 PM »
Wow, thanx!
.
Really seems you are trying to watch for same signatures and properties and dressing to allow them.
Really seems like 1 side of eye slips thru nipping loop to be carried on the weave, and introduced over distance , separate from other half of load on eye for less immediately impacting change.
.
Are you saying broke outside of braid as Nip or in braid sheath before Nipping loop?
>>noted  distortions ?
>>will be trying myself , but have no dynamoter (any more!) etc.
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.~

SS369

  • Global Moderator
  • Sr. Member
  • *****
  • Posts: 1788
Re: What defines a Bowline? - structure, characteristics, topology
« Reply #356 on: November 15, 2017, 01:47:28 PM »
YW KC.

It was hard to watch at the same time as applying the load, but it looked like the spot of contact, just after the braided collar as the nipping loop encircled the bight legs. So, I concluded that there was no significant shedding of load along the braid. Super secure though.
The constriction and first bend at the nip led to the rupture. That is where the markings I had put indicated as well.
Look forward to your results too. Please share.

SS
« Last Edit: November 15, 2017, 11:51:30 PM by SS369 »

Dan_Lehman

  • Sr. Member
  • *****
  • Posts: 3719
Re: What defines a Bowline? - structure, characteristics, topology
« Reply #357 on: November 15, 2017, 05:35:48 PM »
... but it looked like the spot of contact, just after the braided collar
as the nipping loop encircled the standing part.
So, I concluded that there was no significant shedding of load along the braid
Firstly, I don't follow the highlighted text : the nipping
loop aka "turNip" IS the SPart (making its initial turn);
it encircles the bight legs of the (here, quite extended)
collar.

As for shedding of force via the "braid", well, no,
that must be seen as a pipe dream : the SPart gets
100% loading to the braid's at theoretical best 50%
--in a theory ignoring friction : i.p., the effect
of the (why do we call it ...) nipping loop.
The SPart will, in relatively elastic cordage,
stretch thus *thin*, making an even skinnier thing
for the braid to grip, alas.  But the braid isn't getting
even 50% force continued; the imbalance is aggravated.

There are some eye knots in which one can arrange
for the pair of 50%-loaded eye legs to jointly
oppose effects of the SPart, maybe to good effect.
Of course, there is the midshipman's knot / tautline
hitch
structures to do this, where if load isN'T shared,
then ... slippage (noose effect).  (And in such a structure,
one might expect "coil-away" hitches such as ProhGrip
/Blake's hitch
to prove stronger than a rolling hitch
in that their initial, stronger turns come near the eye,
which point the SPart has had to pass through some
possibly lesser gripping (& so, hurting) of the away
wraps!?)


--dl*
====

SS369

  • Global Moderator
  • Sr. Member
  • *****
  • Posts: 1788
Re: What defines a Bowline? - structure, characteristics, topology
« Reply #358 on: November 16, 2017, 12:05:41 AM »
I've edited my post. Just got in a hurry. Thx.

As for: "As for shedding of force via the "braid", well, no, that must be seen as a pipe dream". 
Well,  disagree, in part. The Australian braid fishing loop counts on this shedding/sharing of load. I don't see how this would not work with Rope knots.  http://igkt.net/sm/index.php?topic=863.msg5711#msg5711

In the case of my own experimentation, I just didn't add enough braided crossings. Too ungainly, although it made for a mighty secure loop, imo.
It was worth the effort to find out though.

SS


Dan_Lehman

  • Sr. Member
  • *****
  • Posts: 3719
Re: What defines a Bowline? - structure, characteristics, topology
« Reply #359 on: November 16, 2017, 02:17:33 AM »
As for: "As for shedding of force via the "braid", well, no, that must be seen as a pipe dream". 
Well,  disagree, in part. The Australian braid fishing loop counts on this shedding/sharing of load.\
I don't see how this would not work with Rope knots.

Well, there's the big difference in materials AND in setting forces
(and length!!)--you really need that far reach of the braid to bite
so that increased loading brings increased tension & nipping;
that's hard to accomplish.  If the nipping loop bites --and
recall that that's the whole *game* for a sheepshank!--,
one doesn't get tensioned gripping in the braid (unless the
away/SPart end of it is biting and pulling away with the
SPart's draw.  Then, again, in esp. dynamic ropes,
the change of diameter differences in SPart/eye-leg
create the smaller object to be gripped.

Having something that generates "serious" loading,
such as a 5:1 pulley with body weight, which even
then for many of us is well shy of potential loading,
is a good way to see things that armchair pulling
on might not notice.
(AND, on the other hand, as I noted for the offset
water knot/EDK
, doing low-force puling can
reveal things a single hard pull misses --I was amazed
to see the choking line of that knot just continually
ratchet out, tail consumed (why Mark insists on equal
tail sizes : a measure 2 B Sure if things are behaving,
well, at least in the case of biased slippage).

I came up with what I hope might go some way towards
getting the sort of off-loading of force along a length
of line that we seek for boosted strength
by designing some eye knots in which the twin eye legs
oppose pretty fairly the single SPart's twist.  I.e., the
eye legs --at the eye end of the nub-- presumably will
dominate forces there, and in trying themselves to
UNtwist their helical turning, impart --not merely,
passively resist-- twist to the SPart and a part that
it twists with.  (In the Bimini twist, the outer wraps
merely resist the internally twisted SPart from UNtwisting;
my knot(s) actively twist (in theory).)  At the
SPart's end of the knot, it will dominate (by then,
much force of eye legs has been consumed), and it
will pull straight, un"twist"ing and put all the curvature
into the part it had equally "twist"ed with, making that
part now "wrap"; but hope is that before the SPart
makes its U-turn (unlike B.Twist), its being twisted
is *enforced* by the eye legs.

(Then we see some tests that put simple knots
such as the bowline & fig.8 eyeknot at around
80% --even higher, in a case tested by Tom Moyer--
and we should question to value to getting higher
strength at such cost of knotting ingenuity/complexity!)

(In angling, it seems that high strength --apparently--
can come by (way!) understating line strength : I've
seen tests where knots come out stronger! )

--dl*
====