Referencing this research paper: https://www.researchgate.net/publication/344689340_Revision_of_Commonly_Used_Loop_Knots_Efficiencies
And replying to mcjtom…
Its hard to keep the word count to a minimum when critiquing a published technical paper.
Therefore - all the usual warnings of ‘don’t read - too much technical content ahead’ applies!
Although this is a technical forum dedicated to knot geeks and all things knotting - so in my estimation, the long word count
ought to be acceptable given the nature of the viewers/visitors demographic.
…
The problem with virtually all of these type of papers authored by academia - is that the primary underlying premise is that MBS yield (strength) is the only way to measure and understand knots. It is almost a pathological condition (particularly within the broader context of using knots in life critical applications - eg climbing/canyoning/caving/rope rescue, etc).
The authors of the paper defined ‘knot efficiency’ as:
Knot efficiency is defined as a proportion
of static breaking strength of a rope in which
the knot is tied (marked as x) and static breaking
strength of the same rope without the knot
(marked as y).
Knot efficiency (n = x/y) is usually expressed
in a percentage.
This definition is cliched and just plain wrong in my view.
And yet, it dominates the thought processes of most laypeople (ie it is the default way of thinking about knots).
Knot ‘efficiency’ (in my view) is measured by the following metrics:
amount of rope consumed to form the knot (less is better)
footprint (overall size/volume) of the knot core
stability and security
resistance to jamming
utility and loading profiles (the number and effectiveness of potential applications)
TIB (whether the knot is also Tiable In the Bight)
Interesting note: At para 3.3.7 the authors actually touch on these metrics - but fail to synthesize their significance in terms of ‘efficiency’.
The authors also define knot terminology incorrectly.
For example, their definition of the term ‘tied on the bight’ is muddled.
Their use of the term ‘wend’ is also peculiar. Tail is a better term in the context of what ‘emerges’ from the completed knot core - and has zero load.
The term ‘wend’ was invented to describe the end of the rope while it is being manipulated to tie and form the knot (which is a temporary state).
Their use of the term ‘stand’ could have been improved to SPart (standing part) - a bit of digging around could have uncovered this term.
The authors also use the term ‘ring loading’ - which (in my view) is not properly defined.
Ring loading appears to be constrained to an eye knot (ie loop knot).
And the authors appear to assume a transverse loading direction.
Which actually means the eye is loaded perpendicular with respect to the axial alignment of the SPart (ie at a 90 degree angle with respect to the SPart).
In my view, some assumptions were made.
The term ring loading could be construed as circumferential loading (ie hoop stress).
Note that an ‘eye’ of a knot can also be loaded axially with respect to the SPart (ie load is in axial alignment with the SPart) - which could be considered to be ‘normal’ loading.
I therefore hold the view that ‘ring loading’ is somewhat nebulous.
A better term (for the authors) is transverse loading.
Note that rope rescue technicians can and do load eye knots circumferentially (the Mobius Butterfly knot is efficient for this purpose).
(Meaning that the eye of the knot is pulled in all directions, outwards, which expands the eye).
And furthermore, the issue with transverse loading of the simple #1010 Bowline is that it is in fact cyclic loading which triggers rapid loss of security.
#1034 1/2 is more resistant to cyclic loading in the transverse direction. This is in contrast to loading that is ‘static’ (unchanging, and not cycling).
NOTE: There will be some members of the IGKT forum who will vehemently disagree on my proclivity for defining loading directions more accurately.
Also, knot terminology will always be contentious… for example my preference for ‘eye’ knot instead of ‘loop’ knot can cause convulsions and anger in some.
There are those who will ferociously cling to Ashley’s definitions - in no small way being influenced by tradition.
The ‘General conclusions’ (at #4) in the paper is formulated in a way that is unremarkable and almost meaningless.
For instance; … “With a probability
bordering on certainty, we may conclude that
the efficiency of loop knots is not constant as it
is implicitly presented across the vast majority of
published works, but it is a decreasing function of
static breaking strength of the rope.”
This is an unremarkable comment.
A little better is the second point:…
Furthermore, electron microscopy and high-speed thermal
imaging revealed that knotted rope is subjected to
temperatures of extraordinary extent as the knot breaks
(Sect. 3.3.10).
Although the proclivity of rope to heat up and melt is nothing new.
At 3.4 (Future research) - I would encourage the authors to closely and thoroughly examine the following:
- Why some knot structures are totally jam resistant (and contrasting this with knots that are prone to jamming)
- Dressing/geometry of a particular knot - and how this influences its jam resistance (eg different forms of #1047 F8)
- The influence and effect of varying the number of rope diameters inside the nipping loop of ‘Bowlines’.
- In eye knots that are loaded in axial alignment with respect to the SPart (ie ‘normal’ loading profile) - the effect of parallel eye legs versus eye legs set at different divergent angles.
…
In reference to Scott’s locked Bowline:
Yes - I consider there to be 4 different variations of Scott’s locked Bowline.
I don’t use the term ‘woven’ to describe the geometry - because this can be confused with a ‘woven Bowline’ (a different knot).
Only one of Scott’s locked Bowlines is ‘TIB’.
Yes - the Scott’s locking maneuver definitely improves resistance to cyclic transverse loading (in all 4 variations).
NOTE: When declaring there are 4 different variations of Scott’s locked Bowline, this is true within a defined chiral domain (eg Bowlines with ‘Z’ chirality).
EDIT NOTE: There are risks involved in giving feedback of a technical nature - because people are involved and there is an ever present threat
of hurting someone’s feelings. In my estimation, the key is to separate factual opinion evidence from personally directed attacks.
All I do is present the facts as I see it - but within the realm of knot science, many concepts are either evolving or challenging old traditions.
When you challenge old ideas or beliefs, it is inevitable that there will be individuals who feel angered or outraged (and so the natural human response is to retaliate).