Comparing techniques used for eye splicing double braid polyester (=Class 1)

[s/v Jedi]

This was already mentioned but it only sunk in tonight: the McLaren paper shows that a splice of 1 fid length is actually weaker than a splice of 1/5th of a fid. The shorter the splice, the stronger it becomes but also more difficult to perform. Mind blown.

Also, I learned that the Sailrite splice is actually the Brion Toss splice, in detail

[Alan Mighty]

Originally Posted by s/v Jedi

About history: polyester double braid was invented in the 50's by Samson. That's 65 years of experience which should be enough to find which splices do not work. I believe that every splice described is better than 90% of rope strength.

Samson Rope, the cordage manufacturer started by James Pike Tolman (1847 – 1915) in 1878 as the J. P. Tolman Company and renamed in 1888 after adopting in 1884 a trademark of a strong man (Samson) slaying a lion, only claims it developed the "first synthetic double-braided rope" in 1957.


Tolman had invented an improved switch braiding machine in 1883 (US patent 304045, granted 1884) and improved it further several times. Tolman's company made single braid using those machines (natural fibres at first) and braided cord was their big seller.


In the 1950s, a number of Germans invented and patented various kernmantle lines (kernmantle is sometimes called 'core-mantle' in what used to Ænglish and is now written as English regardless of the pronunciation of the name), especially aimed at the mountain-climbing market. Most of those kernmantle lines had a braided cover and either a parallel or a laid core. But I think there were also some with braided cover and braided core.

Originally Posted by s/v Jedi

Did you know Dyneema is a Dutch invention? DSM invented and produces all Dyneema. They recommend 60x diameter for the bury for coated Dyneema and 100x diameter for uncoated Dyneema.

Of course, every Aussie elementary school kiddie learns that in First Babies!


Do you know the history behind the name 'Dyneema'?


Dutch State Mines (aka DSM, I'll return to this later) proposed the name 'Dynema', a portmanteau word they'd created by fusing Greek δύναμη dynami, strength; + Greek ίνα ina, fibre. To whom were DSM proposing the name? Oh, it was to executives of Toyobo Corp (東洋紡績株式会社 or Toyoboseki Corporation), the Nipponese company which could provide the fibre spinning capacity. The Toyobo executives did not like 'Dynema', it sounded wrong to Nipponese ears (if you object to using 'NIppon' instead of 'Japan', please consider that in the 1930s Nipponese wanted to change the name of their country in English to 'Nippon'. The US govt refused and argued that all countries had to use the English name and that the English name of Nippon was 'Japan', which is the Fujian-language version, picked up by Portuguese merchants, sailors, and priest when they got to Malacca, of one name used in Nippon - so it's a southern Chinese reading of the kanji pronounced riben in modern standard Chinese and as Nippon or Nihon in modern Nihongo). The Toyobo execs suggested that the middle vowel be lengthened. Hence Dyneema.


And what is DSM? Koninklijke Nederlandse Staatsmijnen literally Royal Netherlands State Mines, a state-owned company, started in 1902 to mine coal in Limburg. For a reason unknown to me (lack of national pride? kowtowing to Englanders?) KNS prefers to call itself Dutch State Mines. (yes, a state company, just like state-owned companies in China etc that are demonised by some!)




Who did the inventing? A long story (but one that every Aussie elementary school kiddie learns in Second Babies; most of them forget it and most all teachers don't teach it well because it doesn't show up on any test or exam). It's a long read, but a damn good story. Here's the elementary school text book version:


DSM diversified into chemicals particularly in the sectors of food, health, and materials as it ran out of coal. The last coal mine closed in 1973.


In 1957 Albert Johan Pennings (b. 1932) went to State University of New York to be a PhD candidate in the just created Cellulose Research Institute of SUNY at Syracuse NY. The founding director of the Cellulose Research Institute was Dr J. J. Hermans, formerly professor of physical chemistry at Universiteit Leiden who had a deep interest in natural and synthetic polymers and under whom Pennings had studied at Leiden.


After his research on cellulose in a gel state and graduation in 1962, Pennings returned to the Netherlands and, with a recommendation from Dr Hermans, was recruited to the Fundamental Polymer Research department of DSM, the director of which was Ronald Koningsveld (b. 1925).


Pennings started a research program of fractionating polyethylene molecules by their length so he could study the properties of long-chain high-molecular-weight polyethylene. One day in 1963 he happened to be spin-stirring a solution of polyethylene and noticed the stirring had caused crystals of quite long polyethylene molecule to form. Pennings suspected that longer polyethylene molecules would be stronger than short ones and be valuable products. That was at odds with the prevailing belief that shorter molecules of polyethylene suited flexible products such as fibre and film while the longer molecules would be stiff and only good only for a few structural applications.


After five years further work, Pennings was in 1968 able to withdraw enough crystal fibres of ultra-long ultra-heavy polyethylene for direct study proving that UHMW polyethylene fibres were much stronger than steel and flexible.


Koningsveld and DSM were unimpressed. Koningsveld’s stance was that a new fibre was not a core focus for DSM and, given the existence of such strong aramid fibres as Kevlar, saw no selling point for a unproven strong UHMW polyethylene fibre.


Koningsveld and DSM tolerated Pennings’ continuing efforts to research UHMWPE, publish his findings, and patent his work. His patents ( e.g. US4137394, application filed 1977, granted 1979, based on academic publications in 1970 and 1973) were assigned to Stamicarbon, a special purpose subsidiary of DSM set up in 1947 for intellectual property: the name derives from Staatsmijnen + carbon, referring to coal.


In 1971, Pennings started his academic career at Rijksuniversitiet Groningen (State University of Groningen), initially as a lecturer, while remaining a consultant to DSM. That university-industry link allowed Pennings to introduce promising PhD students to DSM, which would fund a student’s research in return for patents on new discoveries assigned to DSM.


DSM changed its attitude to UHMWPE in 1978 and assigned other employees, including Pennings’ former PhD student Paul Smith and then another PhD graduate from Groningen, Pieter J. Lemstra (b. 1946), to the job of scaling up Pennings’ technique for industrial production. Smith and Lemstra extracted several batches of UHMWPE fibre but faced the problem that the fibres were entangled in a unusable mess.


One batch, first dissolved in a solvent to disentangle the fibres then cooled to a gel state, happened to be extracted from the gel on a Wednesday, and stretched into parallel fibres by Friday. Without particular intent, the batch was left over the weekend to dry. The result was the first batch of strong, aligned and usable UHMWPE fibre.


The patents for their ‘gel-spinning’ process (US4344908, filed 1980, granted 1982; and US4422993, filed 1980, granted 1983) were later celebrated as the 10th most important invention in the history of the Netherlands.


Pennings, who was not included on the patents, was not impressed. He ended his relationship with DSM and turned instead to Akzo NV and Union Carbide to continue his work on UHMWPE and other subjects.


Rijksuniversitiet Groningen elevated Pennings to full professor in 1980. He retired as professor emeritus in 1997. At DSM, Lemstra was left in charge of a weakened UHMWPE project. By 1982, DSM’s chosen yarn spinning partner company reported that the melting point of UHMWPE was too low and dismissed UHMWPE as ‘candlewax’ with little industrial value.


Another DSM engineer, Robert Kirschbaum (b. 1952), who had shared daily commutes with Paul Smith when Smith and Lemstra made their initial discovery, was struck by the significance of UHMWPE being about 15 times stronger than steel and joined the remaining small team which continued work – in their own time on weekends and public holidays – although deprived of dedicated funds and time.


The four chemical engineers of the team would climb over the fence of the DSM compound on weekends to continue their lab work. Their spouses slipped pizza pies under the gate for their lunches.


In the US, Sheldon Kavesh and Dusan C. Prevorsek of Allied Corporation, which produced Kevlar aramid fibres, read Pennings’ academic papers and developed and patented a process for producing UHMWPE fibres that was similar to that of Smith and Lemstra (US4413110 filed 1982, granted 1983; US4536536 filed 1983, granted 1985; US4551296 filed 1984, granted 1986). The lawyers for Allied Corporation (later Applied Fiber Manufacturing of Honeywell International) decided the similarity meant Allied should pay license fees to DSM for what Allied preferred to call ‘high modulus polyethylene’ and trademarked as Spectra. The cash flow from Allied’s license fees meant that Kirschbaum’s team regained research funds and approval from DSM management for further development.


A corotating twin screw extruder, invented by Professor emeritus Dr. Han Henricus Eduard Hubertus Meijer (b. 1949) of the Department of Mechanical Engineering and Department of Polymer Chemistry and Technology of Technische Universiteit Eindhoven, accelerated production of UHMWPE fibres. DSM found a new yarn spinning partner: Toyobo Co. Ltd. (東洋紡績株式会社).


Toyobo has experience spinning fibres since 1882 when its ancestor company, Osaka Boseki, formed.


DSM Dyneema, a new subsidiary, was formed to produce Dyneema powder, fibres, and unidirectionally-aligned fibre reinforced materials (bullet resisting sheet, made at Greenville, North Carolina).


DSM Dyneema and Toyoba in 1991 formed a joint venture, Nippon Dyneema Co., to spin fibre into yarn at Tsuruga City. Toyoba transferred spinning technology to the new DSM High Performance Fibres plant at Heerlen, the Netherlands.


The High Perfomance Fibre technology manager, Koos Mencke, improved on the Toyobo technology so DSM-produced Dyneema yarn was stronger than Nippon Dyneema yarn and Spectra.


In 2002, the American Chemical Society awarded ‘Heroes of Chemistry’ status to Koos Mencke, René Steeman, and Jean Beugels of DSM High Performance Fibres for their efforts producing Dyneema personal and vehicle armour.


In 2010 DSM awarded Professor Han E. H. Meijer the DSM Performance Materials Award.


The Nippon Dyneema plant in Tsuruga City and the DSM High Performance Fibres plant in Heerlen each produce about 3,200 tons of UHMWPE yarn a year.


With the approval of DSM, Toyobo brands UHMWPE sold in Japan as Izanas.

[Alan Mighty]

Originally Posted by s/v Jedi

This was already mentioned but it only sunk in tonight: the McLaren paper shows that a splice of 1 fid length is actually weaker than a splice of 1/5th of a fid. The shorter the splice, the stronger it becomes but also more difficult to perform. Mind blown.

Yes. Heather McLaren noted that much more work need to be done. Her term paper is not a polished work (she went on to do her Masters at a uni in either Norway or Sweden and is now focused on lubrication).


Remember that one scientific paper is not the last story. Her test needs be repeated. No one has picked up the opportunity (Heather explicity said it needs more work).


Heather McL reckoned that the shorter splice would slip (and did) under cyclical strain. But for a steady strain, it did the job superbly.


In Katherine Milne's work (best read in the Milne & A J McLaren paper, even though double braid is only one of three subjects), Milne & A J McL also had to reduce the length of the splice to 1/3 and then to 1/5 to get the splice to slip.


That's one of the magics of braid in contrast to laid rope. Laid splices depend on the friction from the number of tucks. Too few tucks and the splice slips. With braid, the strength of the splice comes from (1) simple friction from the tuck; increased by (2) compound friction as the braid cover constricts under strain and so presses everything (the core, the cover-in-core, etc) together, multiplying the friction.


Milne & A J McL also point to (but A J McL has not himself or directed one of his students to) the notion that when we make a splice, we break and abrade some of the fibres. So a shorter splice means less abrasion and breakage of fibres (but also less friction). So the less abrasion + breakage balances the lower friction.


That notion of Milne & A J McL also relates to the length I-II of core through which the cover is tucked. They suggested that two short a length of core meant that the core bunched up and caused more abrasion and breakage of fibres.


What goes on inside a Class 1 double braid splice is not simple.


And even abbreviated versions work (see the work of Bob Norson who I referenced in an earlier post)!


It's easy to think that the Norson Splice, the Norson Double Splice, or the Premium Ropes splices are shortcuts. Not enough tests have been done to show if the trade-off (less abrasion and breakage of fibres versus less friction) work. But Norson's farmyard test showed his Norson Double Splice worked (in the sense that the rope broke, not the splice; that's what happens in most of the Strathclyde Uni tests too - the point that you have to reduce the splice length to 1/3 or 1/5 for it to reliably slip!).

Originally Posted by s/v Jedi

Also, I learned that the Sailrite splice is actually the Brion Toss splice, in detail

Thanks for that gem of info. Cuts down on the number of techniques to cover. And tells me of a good video for the Brion Toss splice (which is my favourite technique, but which I've stuffed up two or three times because I do not do it enough).

[Seaworthy Lass]

6am here and I have decided to postpone my trip using weather as the excuse. 6°C, rain and gusts into the 30's would not normally put me off, but I am drawn to the discussion here .

Alan, that bit of history was fascinating! You are a mine of information (no pun intended).
Coincidentally, my trip today was to Zwolle, where DSM are based!

Originally Posted by Alan Mighty

...Of course, every Aussie elementary school kiddie learns that in First Babies.

.
I must have been playing hooky that day .

Alan, I am right in the heart of things here. I was in Groningen last week (the Rodin exhibition was the drawcard).
Thanks for the post. Background information such as that enriches my life here.

SWL

[Seaworthy Lass]

Originally Posted by Juho

Yes, X can be wherever one wants them to be (with E'). The drawing is generic. I drew E' further to left than E because the core would reach further to the left than cover if it is not shortened or shortened only moderately.
In the figure L and R have changed place. And L' and R' on the other side.

I have reversed them now . I was reading your text, not following the diagram and understood L was meant to be the start of the loop from the end of the rope we are working with, not from the standing end's side. It is actually the first mark made to indicate where the loop occurs.

Originally Posted by Juho

If the P point is the one that is marked after (or before) the core is extracted and the whole rope milked, I think it should be the same as L' (that should be at the R' position in the figure because L' and R' were swapped).

Yes, P is the point that is marked after the core is extracted and milked. Some methods skip the initial milking step.

I had taken L' to be where the core finally ends up opposite L, not where it was before the splicing. Your definition is simpler, so I have deleted P on the diagram as well.
L' is now where the core is marked at the point it is pulled out of the cover.

Originally Posted by Juho

In my drawing the splice is shown after the core has been shortened. In your drawing the core is still in its original length, I believe. If so, E' of my drawing should maybe refer to the S point of your drawing. The end of the core (including the point that is named E' in your drawing) is missing. I don't know how to draw the cut off part of core in my drawing. In your drawing the end of core could be named E'' (or S or whatever). Or what would be the best way to name the original and shortened end of the core (and match the drawings where the core is in its original length vs. shortened)?

Yes, my diagram shows the full length of both the core and cover.

I think this needs to be included, as that is the starting point. I have defined E' to be the end of the core at the start, not the end after cutting.

I think it would be more useful to leave E' where it is and marking the cut point seperately. With very thin rope EX approaches E'X' if the relationship between the core and cover are maintained and the length of tail bury of the core beyond the base of the loop is the same as that of the cover. That is a nice symmetry .

Note: Alan's table also needs to include the diameter of rope used in the videos. The relationship (expressed in Ø) between all the marks made on the core will probably be dependent on rope diameter, as well as on the method used.

So, this is my modified diagram to incorporate the marks many manufacturers place, it does not cover Premium well, but they are a PITA marking the end of where the tail bury should be on the core, not the beginning:




Edited to add: better to call S S' instead I think, as it immediately then indicates it is a mark on the core.

[Seaworthy Lass]

Originally Posted by Juho

The end of the core (including the point that is named E' in your drawing) is missing. I don't know how to draw the cut off part of core in my drawing. In your drawing the end of core could be named E'' (or S or whatever). Or what would be the best way to name the original and shortened end of the core (and match the drawings where the core is in its original length vs. shortened)?

Juho, this is how I suggest modifying your diagram. It matches mine then and incorporates the end of the core that is cut off:



Edited to add: I have changed my mind. I think I would call S, S', as then it is is clear that it is a mark on the core, not the cover.

[Alan Mighty]

Originally Posted by Seaworthy Lass

I must have been playing hooky that day .

It's the new syllabus we old 'uns didn't get to enjoy.


Preparatory 1 (First Babies), and Preparatory 2 (Second Babies), now come before Year 1.


Under Prime Minister Trumble's wise (and strong and clear) leadership, kiddies are encouraged to be agile and innovative. They draft their first business plan in Year 1 (or do a project involving their first patent if their teacher is more disposed to science/tech/engineering thingies).

Originally Posted by Seaworthy Lass

Alan, I am right in the heart of things here. I was in Groningen last week (the Rodin exhibition was the drawcard).
Thanks for the post. Background information such as that enriches my life here.

A great place of which to be in the heart. If you follow the economic and political history from the Napoleonic Wars to now, you alternatively laugh and weep. The strangeness of half of the House of Nassau translocating from Germany to Netherlands and back and forth, doing deals with the Holy Roman Empire (of the German Nation) until they become the House of Orange. Just the oddness of orange (and people breeding carrots to be orange instead of a variety of colours from pasty off-white to purple, but orange to celebrate the House of Orange; not to mention the source of oranges in China and the bizarre evolution of the word that became 'orange'). Then all the way through to WW2 and the horror of life in the Netherlands in the late 1940s and 1950s.


I was brought up not far from my home marina in Scarborough, Moreton Bay. An area is that a ghetto of whitepfellas (and still has a great concentration of UK-origin voters who prefer Prime Minister for Life Trumble or, second choice, Hegemon for Life Pauline 'Red' Hanson nee Seccombe). But in the 1950s, that area hosted a surprising number of Netherlanders looking for a better life (and at least found a reliable source of food, when not a few of their family back home were close to starvation). So my first bicycle was a second-hand one my Dai bought from a Netherlander family: brakes connected by rods instead of push-pull cables. Kids my age who introduced me to a different way of looking at the world. And their parents who had lived through real hardship.


As for the history, consider what those people did: Hermanns doing a favour for a student, Pennings, Lemstra and his team (and their wives slipping them pizza every weekend), and the wonder of Prof Dr Han H E H Meijer, who could turn his hand to any problem and solve it. And it would not have happened without honest US lawyers who insisted that Allied pay license fees to DSM. Or the wise heads from Toyoba, working well outside their first language, who rolled the word Dynema around, shook their heads, and came up with that simple elongation of the vowel - something no big nose would think about - that created the magic of Dyneema.


No wonder that smart Aussie educationists decided that these lessons should be learned by every kiddie!


I'm a tad sorry that writing the kanji somehow screwed up the font size for the rest of that para and I noticed it not.


I'll aim to hit a few items on the job list then get back to a concordance of names for markings. And other things.

[Seaworthy Lass]

Originally Posted by Alan Mighty

A great place of which to be in the heart. If you follow the economic and political history from the Napoleonic Wars to now, you alternatively laugh and weep. The strangeness of half of the House of Nassau translocating from Germany to Netherlands and back and forth, doing deals with the Holy Roman Empire (of the German Nation) until they become the House of Orange. Just the oddness of orange (and people breeding carrots to be orange instead of a variety of colours from pasty off-white to purple, but orange to celebrate the House of Orange; not to mention the source of oranges in China and the bizarre evolution of the word that became 'orange'). Then all the way through to WW2 and the horror of life in the Netherlands in the late 1940s and 1950s.

I have been engrossed in this . It absolutely intrigues me, particularly as it confronts me each time I step out the door.

You can imagine how I love Greece. I frequently walked in the footsteps of Anthony and Cleopatra. The region is drenched in blood, sweat and tears. Powerplay, seduction, betrayal... It was mindblowing thinking back not just centuries, but millenia and coming across countless unmarked ruins that are likely to have predated the Romans. This is one thing that kept me for so long in Greece.

Originally Posted by Alan Mighty

As for the history, consider what those people did: Hermanns doing a favour for a student, Pennings, Lemstra and his team (and their wives slipping them pizza every weekend), and the wonder of Prof Dr Han H E H Meijer, who could turn his hand to any problem and solve it. And it would not have happened without honest US lawyers who insisted that Allied pay license fees to DSM. Or the wise heads from Toyoba, working well outside their first language, who rolled the word Dynema around, shook their heads, and came up with that simple elongation of the vowel - something no big nose would think about - that created the magic of Dyneema.

Yes, we do need to extend thanks. And to all the researchers that plug away often for years in the advancement of knowledge and often in hope of helping mankind. Often all this work leads to only the smallest of advances, but these are then the building blocks of bigger and better things. They are truly the unsung heroes in my opinion. They rarely share any of the fame and glory, not that that is usually their motivation.

Originally Posted by Alan Mighty

I'll aim to hit a few items on the job list then get back to a concordance of names for markings. And other things.

Alan, Juho has come up with excellent system for names for marking with a slight modification by me. I will define these properly in the next post.
Are you OK with these? We need some standard and just using Samson's notations (that do not cover all manufacturers) is not the best thing to do I think.

SWL

[Seaworthy Lass]

And here are the definitions to match Juho's marking system.
Juho, could you please check these?

Ø = rope diameter

Juho, K is the second additional mark I have thrown in. It affects the ease of making the splice, so if Alan's table is being used for comparison between methods, then this should be included. Alan had a row for this.

Alan, by the way, do you think it would be better to make your rows the columns and the columns the rows? As the list of methods grows is will then just continue down the page. Also results from different sources using the same method can be added. Comments about tapering need to be included I think, but perhaps full tapering methods can be added elsewhere, as Juho suggested (as can tips)?
In addition, I would add a column for rope diameter used in the procedure. I think this may affect things. The change in quantity of rope diameters need not be exactly proportional to the actual rope diameters.

It makes sense I think to get the notation and format of the table sorted out well first, then we can start filling in the data.

Developers of the method will not necessarily have you mark all the following, but these points do exist for each eye splice in double braid. To fill in Alan's table, some of these will need to be estimated. "Freezing" images from videos make this possible, particularly as fids are often visible, so we have a reference scale:

COVER MARKINGS:

E = end of the cover after the initial sharp trim

R = first mark for the base of the loop, usually specified in fid lengths
(therefore ER is the length of cover buried in at least the cover)

L = second mark for the other side of the loop and this is selected by the user depending on what loop size is needed
(therefore RL is the length of the loop)
The core is extracted at L
R coincides with L when the loop is formed

C = mark where the core enters the cover for the bury of the core in the cover
(therefore CE is the initial length of bury of the cover if enough core is allowed to cover this)
C is sometimes specified as number of strands from R. It may coincide with R.

X = mark where core exits and is cut off
(sometimes given as fid lengths and sometimes as a set distance from L)

K = mark where distant knot is tied, a distance of EK from the working end of the cover

CORE MARKINGS:

E' = end of core after the initial sharp trim

L' = mark that coincide with L before the core is extracted at L
(usually the first mark made on the core)
E'L' is not necessarily the same as EL, as sometimes the core is pulled out and milked back before this is marked.

C' = mark where cover enters the core for the bury of the tail
(usually L'C' is specified in fid lengths)
This distance is what I call a "fudge factor"

X' = mark where cover exits the core before it is milked back into the core
(Not always specified: sometimes the user is just instructed to make it long enough to bury the cover tail, sometime is it just specified to be excessively long so there is plenty of length of core for the desired cover tail length to be buried)

R' = mark that coincides with L when the core tail is cut off

S' = mark where core tail is cut off
It coincides with X when it is cut off
(therefore R'S' is the initial length of the core that is buried below the loop, and
E'S' is the length of core cut off
R'S' initially roughly = LX)

The relationship between core and cover is unlikely to be static I think, so distances between marks on the core and marks on the cover may alter under load.

My hypothesis is that when too much core is cut off, under load CC' will lengthen and decrease the amount of bury of cover in the core, and R'R will lengthen and decrease the amount of bury of core in the cover below the loop.
This may weaken the splice.
Also all the movement generates heat and may additionally weaken the splice.

If the core is not moving when it is too short, then there is excess cover below the splice and this will probably weaken the line.

See Juho's excellent diagram to instantly see the effect of the core moving. If it is occuring it is because the core is sliding back down the rope to where it was originally before any core was pulled out ie R & C will stay in the same spot, R' and C' will be moving.

I find the amount of core cut off in some methods disturbing, and that is essentially what generated this thread (see post #8). It made no sense that this could be done.
I may be totally wrong. That has been previously known to occur .

SWL

[Juho]

Originally Posted by Seaworthy Lass

Juho, this is how I suggest modifying your diagram. It matches mine then and incorporates the end of the core that is cut off:

What do you think of this? I used S' (and upper row of the names) for the shorting point of the core since all core markings are so far marked with prime. I added also S for the cover, although it is typical that the cover is not shortened at all (therefore at the same place with E).

[Seaworthy Lass]

Originally Posted by Juho

What do you think of this? I used S' (and upper row of the names) for the shorting point of the core since all core markings are so far marked with prime. I added also S for the cover, although it is typical that the cover is not shortened at all (therefore at the same place with E).

Perfect .
It is more logical placing all the marks for the core on one side and the cover on the other, as you have done.

I don't know if you noticed, but I had already renamed S as S', as it made more sense to have all the core marks indicated with a '

To complete things, yes, add S as well. Is is actually possible that in some methods (where tapering occurs) that some of the end of the cover is accidentally cut off, creating an ES value.

SWL

[Juho]

I had to remove one line near the R point since it disturbed my eye too much now when both core and cover have colour.

[Seaworthy Lass]

Agreed, LOL.
And for the sake of consistency, I will change the colour of my cover and core to match yours.

So using this latest diagram of Juho's:




This is the matching diagram when the rope is laid out and marked before splicing (sorry, my graphics aren't the best ):

[Seaworthy Lass]

I am just changing some of the comments on R' and L' in post #84, so just have a look back before commenting.

It is confusing me, as I initially called L R and R L and I can't get that out of my head

SWL

[Seaworthy Lass]

Originally Posted by Seaworthy Lass

My hypothesis is that when too much core is cut off, under load CC' will lengthen and decrease the amount of bury of cover in the core, and R'R will lengthen and decrease the amount of bury of core in the cover below the loop.
This may weaken the splice.
Also all the movement generates heat and may additionally weaken the splice.

If the core is not moving, then there is excess cover below the splice and this will probably weaken the line.

NOTE:
If there is excess cover below the core then the relationship between core and cover will then be different. The breaking strain of the line will probably then be reduced and the line will break somewhere along its length when it does break, not at the splice. It may even break some distance from the splice.

The problem with this is that unless you know exactly what load caused the line to break, you will say "Nothing wrong with my splice, it held. It was the line that broke".

SWL