Author Topic: KNOT TESTING GUIDELINES - is IGKT best positioned to set fundamental guidelines?  (Read 5218 times)

agent_smith

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My original concept and purpose behind starting this thread was to mobilize a concerted effort to address the shortcomings and failings of knot testing and reporting of results.

I maintain and reaffirm that there is no current body or entity that a knot tester can turn to for advice in the following:
[ ] knot naming conventions
[ ] knot form and structure (geometry) - ie getting the dressing correct for a particular knot species
[ ] what to test - eg rather than the default pull-to-failure mindset that permeates the entire sub-culture
[ ] use of appropriate control knots to draw comparisons against

NautiKnots source of continued irritation is linked to his belief that current institutions (eg cordage institute USA) already address statistical sampling methods and proper use of tensile (force) generating machines so that testers can obtain reliable results.

But this misses the point entirely.

There are principally 3 distinct forms of testing carried out:
1. Hobbyist/enthusiast style testing done by interested individuals who largely act in isolation. This type of setup is not a business enterprise. It is typically conducted at the testers home (but it could be carried out in a garage/shed or even the persons backyard).
2. Semi-formal testing done in a non-certified lab with mechanised equipment and is generally done by individuals who hold themselves out as possessing an expertise. This type of setup is sometimes a business enterpise  - eg rope access and/or vertical rescue business enterprise.
3. Formal testing done in a certified lab in accordance with their accredited procedures - but the individuals behind the tests are typically lab technicians first and knot enthusiasts last. This type of setup is usually a business enterprise.

I think NautiKnots source of irritation is linked to #3. In a formal certified test lab - everything is done in accordance with strict protocols. There is specialised force generating equipment that is carefully calibrated - and an environment that is purpose built to carry out a range of destructive style testing.

In #1 above, funds are typically very limited and so is spare time. There is no formal environment in which to operate. There is no strict use of calibrated force generating instrumentation.

In #2 above, usually the tester(s) have access to more funds and may have setup a pseudo lab. A good example would be 'Rope Test Lab' run by Richard Delaney in NSW Australia. He is a roping enthusiast but his 'lab' is not 'certified' as such. Within Australia, such lab certification is typically done through 'NATA' (National Association of Testing Authorities). Note that 'NATA' is not specifically knowledgeable about knots and knot structure. NATA is about setting up a test lab so it can test articles consistently and reliably to a certain standard.

This is largely what the cordage institute is.
It is not specifically knowledgeable about knots and knot geometry. Its more about measurement and pulling test articles to failure. Although the word 'cordage' is embodied in the title, this has more to do with cord/rope construction rather than knot tying.

And this is where NautiKnots source of irritation comes from.

As it currently stands, well funded knot testers could turn to a certified lab and request a set of tests (for a fee). The certified lab would not have any expertise on how to tie the knot specimens or what to test. This would be the responsibility of the individual who hires the use of the lab facility for a fee.

In Richard Delaney's case, he is not a certified lab - but, he does have a pseudo lab environment and access to motorised force generating equipment. Richard would not turn to 'NATA' or the 'Cordage institute' for advice when testing. This is because 'NATA' and the 'cordage institute' do not possess specialized expertise in how to tie knots and what to specifically to test.

Whilst I have due respect for testing authorities such as 'NATA' and the 'Cordage institute', these entities do not possess specialised expertise in knot tying.

Hopefully, Nautiknots irritation will subside, now that I have clarified that testing authorities do not possess specialised expertise about knots and knot tying. These entities focus on reliability of test methods and the machinery that produces the tensile forces. And it is all based around the mindset of 'pull-to-failure'. If I contacted the Cordage institute and asked them;
"How do I tie and test the Offset overhand bend?"
Their response would be; "          " (blank).

Remember that all entities and authorities consist of people (humans like you and me). It is the people that comprise the entity. Merely because an entity carries a title such as 'NATA' or 'Cordage institute' or 'IEEE', does not by itself automatically grant expert level knowledge about knot tying.
« Last Edit: August 20, 2018, 12:36:06 AM by agent_smith »

agent_smith

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This is my attempt at shifting into 1st gear - in order to cease spinning wheels and going nowhere.
Note that this is only 1st gear - but at least its a start.

And so...  I propose the following as a basic framework for knot testers and aspiring knot testers.
This shouldn't be too onerous / difficult to achieve.

KNOT TESTING GUIDELINES (A basic framework)

Checklist:


[ ] Determine the purpose of your test
    eg; to determine the MBS yield point (ie load at which the knot breaks) or to investigate something else? (eg at what load does the knot jam or, at what load is instability triggered or, which dressings improve or lessen stability?)
     - if you are of the 'pull-to-failure' (ie break it) mindset, ask yourself "why?" Why is it important to pull your knot specimen to failure?
     - what are you trying to prove?
     - is 'pulling the knot to failure' really going to conclusively prove anything? (note that harness tie-in knots dont break when you take a lead/climbing fall...there is no force that a falling climber can generate that will break a knot. Your climbing rope is more likely to fail due to cutting/sawing over sharp edges). Even in highlines, where the line tension is maxed out, still doesn't break knots. In this case, your anchors are more likely to fail or yield. If you are of the general population mindset that pulling knot 'A' to failure against knot 'B' to failure proves superiority of one compared to the other - you should re-think your proposition!

[ ] Determine the type of cordage/rope that you will use for the test
    - this is crucial. The type of material plays a significant role in how the knot will respond to load.
    - slippery materials such as 'dyneema' will behave differently to regular EN1891 certified low stretch abseil rope
    - what diameter cordage/rope will you use? The larger the diameter, the greater the force required to reach its MBS yield point
    - maybe you want to use 2 different rope diameters (eg a 'end-to-end' joining knot to see how it responds to increasing load)
    - are you testing ropes that conform to an EN standard? (eg EN 892 dynamic climbing rope)
    - is it imperative that you test human-rated ropes that conform to a standard? (eg EN 1891, EN 892, etc)
    - is your rope/cordage in brand new (unused) condition? Or is it aged? If aged, how old?
    - either way, it is important that you are very clear on exactly what type of rope/cordage you are using

[ ] What type of test facility are you?
    - I am a 'backyard' tester. I do not have any sophisticated test apparatus. I am not well funded and I don't like math (ie statistics).
    - I have a pseudo test lab. It is not a certified lab but, I do have access to force generating equipment and limited funds.
    - I am a certified nationally accredited test lab. I have calibrated force generating equipment and computers to measure and document results. I am reasonably well funded.

    NOTE: The level of expectation scales according to which test category you fit within. If you are a 'backyard' tester, we are not going to criticize you for failing to use calibrated digital instrumentation and avoiding hard statistical mathematics!

[ ] Check in at the IGKT website/forum and run your test idea there.
     - although full of nerdy knot enthusiasts, the IGKT has some exceptionally talented individuals who have unique insights into all things knot related. They can provide expert level advice all free-of-charge.

[ ] Use appropriate naming conventions for your knot specimen so it can be properly identified

    eg; Where possible, use 'ABoK' reference numbers.

[ ] Pay close attention to knot 'dressing' (ie form and structure)
    - dont be sloppy - be ruthlessly accurate in getting the dressing correct!
    - diligence is the key

[ ] Photograph your knot (before, during and after your load test)
    - take your photos against a plain while background...eg, use a plain white bed sheet as a background for your photo
    - make sure all segments of the knot structure are visible in the image (including the 'tail' end)

[ ] Repeat your test several times to obtain a reasonable statistical sample (ideally, at least 5 repeats)
    - breaking or jamming knots costs money - we know this. Keep in mind that a test sample of '1' is not sufficient to draw any conclusions...you need to do more than just one test.

[ ] Use a 'control'
    Try to be 'scientific'...all good science testing uses what is known as a 'control'.
    Link to info about scientific 'controls': https://en.wikipedia.org/wiki/Scientific_control

[ ] Measure the force that you are applying to the knot
    - try to use force generating equipment that has a 'gauge' so you know how much tensile force you are applying
    - digital is best but, if you only have an analog gauge then this will suffice.

[ ] Report your results
    - make sure you write a conclusion

...

Mark Gommers
« Last Edit: July 05, 2018, 11:25:11 PM by agent_smith »

KC

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i don't approve of road racing, but see pro-racing as measurement, competitive development; that in end drives us forward.
i think strength tests are good, but not total purpose, just benchmarks and expanded understanding as we groom the mechanics.
.
Standardization would be good, nice list, but wouldn't throw away thoughts and observations of the mentioned testing associations;
to get their experiences as well as draw them into helping mature this, and then also adhering and leading with it.
.
i think that safety awareness should be part of this; as pushing knot to 'explosion' especially if metal link is attached can be hazordous to people, expensive testing gear etc.
.
i liked Eric22 / alan_lee's http://igkt.net/sm/index.php?topic=6120.msg41258#msg41258
>> shows deformities, changes, damage to line  >> data is data, and seeing what really happens makes so well makes simpler watching more tangible and intuitive.
>>perhaps anti-climatic w/o knot explosion, but still many lessons shown >> data is data
and safer to walk to edge and not jump off, knot explosion could have been injurious, taken out measuring device etc.
>> should look to have safety guidelines, suggestions if not just warnings
.
i think several tests and different materials done at same time /circumstance / tester
>>in playing around when could, i have made eye to eye sling with different Bowline's
one of the things testing is tail in eye or not  >>  1 Bowline of each on ea. end of sling to same type carabiners pulled by truck
>>different materials seem to break earlier on the 'innie' and others on the 'outie' side of the home-made sling
no meter, just who fails first: the most direct Nip of 'outie' missing Bitter End or w/less directness but more primary force on both parts of final turn around SPart of 'innie'.
.
i'm all with observing the proper geometries, as really the most key concept anyway
>>and think naming or at least family groups should be formed by respect of such geometries and force flow thru them.
>>but for reachability outside to the masses, some groupings by type of usage are necessary; or at least need to be allowable.
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.~

NautiKnots

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NautiKnots source of continued irritation is linked to his belief that current institutions (eg cordage institute USA) already address statistical sampling methods and proper use of tensile (force) generating machines so that testers can obtain reliable results.

But this misses the point entirely.
No, you missed my point entirely.  I never promoted the use of tensile strength as a useful measure of knots.  Nor did I ever say that the Cordage Institute is a source for information on knots.  Now you are the one trying to put words in my mouth and your assertions are utterly false.

ALL my statements were about testing methodology and statistical significance, not about what tests were being performed, nor about what tests should be performed.  I simply said that although the IGKT is skilled at knot tying, it is not skilled at designing consistent, repeatable, and statistically significant tests, and could learn from the exmaples of others.

At this point, you have exhausted my desire to participate, so I have stopped following this discussion.  You need not worry about further posts from me.  I simply leave you with this food for thought:

If you truly want to be a "key player" in setting standards for knot testing, is it really wise to begin by summarily dismissing all published work by
  • the de-facto standards body of the cordage industry, and
  • the world's largest association of technical professionals?
Do you really believe that you know more about how to construct scientific tests than they do?  Good luck -- I have little faith in your success.

Regretfully,
Eric

agent_smith

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NautiKnots,

I think you have a strong desire in wanting to defend yourself in relation to some imagined proposition.

And your desire to defend appears to be linked to your belief that methodology established by testing authorities is very important - and should not be ignored.

There is no intent to extinguish existing methodology established by 'testing authorities'. To the contrary, they are complimentary and should coexist with these established testing methodologies.

Dont forget the 3 different types of testers:
1. Backyard type testers who largely act in isolation
2. Pseudo lab testers (eg Rope test lab...Richard Delaney)
3. Accredited/certified testing labs with calibrated equipment and measurement recording devices.

Expectations and accuracy scales according to each type of tester.

For example, I think it would be unreasonable to hold a 'backyard tester' to the same level of rigor as an accredited and certified test lab. In contrast, we would expect an accredited, certified test lab to produce scientifically valid test results.

Perhaps your views re consistency, and collecting statistically valid test data is aimed largely at accredited, certified test labs and (possibly) pseudo test labs?
« Last Edit: July 28, 2018, 10:32:34 PM by agent_smith »

Mobius

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So, let's say someone finds a test facility, has a camera, has some selected rope (maybe various dimensions?) of the same construction/materials and wants to invest some life to run some tests. What list of procedures, protocols, etc., etc., can they use that the results won't be systematically poo-pooed or nitpicked?

Backyard or field testing and even some of the sources online of tests gone by are regularly picked apart for one thing or another here.

If we have an agreed upon check and set up list, then it makes sense to to do the investment. That is what I hope to see this thread develop into.

SS

Indeed, that is why I am rather hesitant to offer suggestions in this thread or post any sort of 'conclusion' from home trials of a knot I test. That is especially true if I do some trials and they happen to contradict someone's theoretical proclamation about their cherished knot. Been there, done that, and it has not been worth the insults I received on this site in the past ???


KNOT TESTING GUIDELINES (A basic framework)

Checklist:


[ ] Determine the purpose of your test
    eg; to determine the MBS yield point (ie load at which the knot breaks) or to investigate something else? (eg at what load does the knot jam or, at what load is instability triggered or, which dressings improve or lessen stability?)
     - if you are of the 'pull-to-failure' (ie break it) mindset, ask yourself "why?" Why is it important to pull your knot specimen to failure?
     - what are you trying to prove?
     - is 'pulling the knot to failure' really going to conclusively prove anything? (note that harness tie-in knots dont break when you take a lead/climbing fall...there is no force that a falling climber can generate that will break a knot. Your climbing rope is more likely to fail due to cutting/sawing over sharp edges). Even in highlines, where the line tension is maxed out, still doesn't break knots. In this case, your anchors are more likely to fail or yield. If you are of the general population mindset that pulling knot 'A' to failure against knot 'B' to failure proves superiority of one compared to the other - you should re-think your proposition!

[ ] Determine the type of cordage/rope that you will use for the test
    - this is crucial. The type of material plays a significant role in how the knot will respond to load.
    - slippery materials such as 'dyneema' will behave differently to regular EN1891 certified low stretch abseil rope
    - what diameter cordage/rope will you use? The larger the diameter, the greater the force required to reach its MBS yield point
    - maybe you want to use 2 different rope diameters (eg a 'end-to-end' joining knot to see how it responds to increasing load)
    - are you testing ropes that conform to an EN standard? (eg EN 892 dynamic climbing rope)
    - is it imperative that you test human-rated ropes that conform to a standard? (eg EN 1891, EN 892, etc)
    - is your rope/cordage in brand new (unused) condition? Or is it aged? If aged, how old?
    - either way, it is important that you are very clear on exactly what type of rope/cordage you are using

[ ] What type of test facility are you?
    - I am a 'backyard' tester. I do not have any sophisticated test apparatus. I am not well funded and I don't like math (ie statistics).
    - I have a pseudo test lab. It is not a certified lab but, I do have access to force generating equipment and limited funds.
    - I am a certified nationally accredited test lab. I have calibrated force generating equipment and computers to measure and document results. I am reasonably well funded.

    NOTE: The level of expectation scales according to which test category you fit within. If you are a 'backyard' tester, we are not going to criticize you for failing to use calibrated digital instrumentation and avoiding hard statistical mathematics!

[ ] Check in at the IGKT website/forum and run your test idea there.
     - although full of nerdy knot enthusiasts, the IGKT has some exceptionally talented individuals who have unique insights into all things knot related. They can provide expert level advice all free-of-charge.

[ ] Use appropriate naming conventions for your knot specimen so it can be properly identified

    eg; Where possible, use 'ABoK' reference numbers.

[ ] Pay close attention to knot 'dressing' (ie form and structure)
    - dont be sloppy - be ruthlessly accurate in getting the dressing correct!
    - diligence is the key

[ ] Photograph your knot (before, during and after your load test)
    - take your photos against a plain while background...eg, use a plain white bed sheet as a background for your photo
    - make sure all segments of the knot structure are visible in the image (including the 'tail' end)

[ ] Repeat your test several times to obtain a reasonable statistical sample (ideally, at least 5 repeats)
    - breaking or jamming knots costs money - we know this. Keep in mind that a test sample of '1' is not sufficient to draw any conclusions...you need to do more than just one test.

[ ] Use a 'control'
    Try to be 'scientific'...all good science testing uses what is known as a 'control'.
    Link to info about scientific 'controls': https://en.wikipedia.org/wiki/Scientific_control

[ ] Measure the force that you are applying to the knot
    - try to use force generating equipment that has a 'gauge' so you know how much tensile force you are applying
    - digital is best but, if you only have an analog gauge then this will suffice.

[ ] Report your results
    - make sure you write a conclusion

...

Mark Gommers

Mark, as you know I 'home-test' knots. I suggest to you that I actually home-trial knots, there is a distinction perhaps.

I am about to get very busy again with the start of the new school term. If you are interested in my thoughts I will try and find some time to provide them. The framework you provide above is off to a good start, FWIW.

Cheers, Ian.


agent_smith

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per Mobius:
Quote
it has not been worth the insults I received on this site in the past ???

Thats a harsh criticism. If your backyard testing fulfills certain minimum criteria, I am sure that everyone would appreciate your conclusions.
Some people get very fixated on a concept and will defend it to the end.

I can see one brewing already - with the distinction between 'backyard testing' versus 'home trials'.
The word 'trial' versus 'test', (is it a trial or is it a test?). Most people understand the concept of a knot test.
And 'home' versus 'backyard', (home implies at someones house, or perhaps your own house. What if you performed the 'test' at a park, in someones garage, or at someones workplace?).


Mobius

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Quote
it has not been worth the insults I received on this site in the past ???

Thats a harsh criticism. If your backyard testing fulfills certain minimum criteria, I am sure that everyone would appreciate your conclusions.
Some people get very fixated on a concept and will defend it to the end.

No, that wasn't harsh. Words like insulting, belligerent, and trollish behaviour immediately spring to mind for some 'feedback' I have received in the past. But let's move on, shall we?

I can see one brewing already - with the distinction between 'backyard testing' versus 'home trials'.
The word 'trial' versus 'test', (is it a trial or is it a test?). Most people understand the concept of a knot test.
And 'home' versus 'backyard', (home implies at someones house, or perhaps your own house. What if you performed the 'test' at a park, in someones garage, or at someones workplace?).

I was not intending to nitpick your proposal. I have experience in home trialling knots and that might have been helpful.

Dan_Lehman

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ALL my statements were about testing methodology and statistical significance,
not about what tests were being performed, nor about what tests should be performed.
I simply said that although the IGKT is skilled at knot tying, it is not skilled at
designing consistent, repeatable, and statistically significant tests,
and could learn from the examples of others.

And I'd like to see some description of what these
tests would be.  As you've stated, it matters to understand
what you want to test, and I think that we can come
to some agreement about what seems to be but actually
isn't (so well) tested, in a number of cases.

We might come to see that extensive testing as some
urge on the basis of adequate test cases for statistical
sanity sadly simply doesn't really give us great information
for understanding knots.  --to which my How Many Samples
to Test Milk... example was meant to suggest.

And that a better, surer step forwards is articulating
the data aspects --i.e., things to be noted (probably
less temp./humidity and more rate-of-loading ...)
by testers.  I'm always wanting to SEE what the actual
--not presumed well-enough specified in literature--
knot looked like when push came to shove!


--dl*
====

agent_smith

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This is in reference to my previous post (Knot Test).

Images of test equipment...

EDIT: The load cell I would really like to own is the rock exotica 'enforcer'.
It is the best in its class. But, very expensive to purchase here in Australia (AUD $1200.00).
Link: https://www.rockexotica.com/enforcer-load-cell
Brilliant engineering - made in USA.

Maybe one day a kind IGKT member living in the USA might be able to do a deal with me (I transfer private payment and we organize cheap shipping to Australia).
« Last Edit: July 27, 2018, 02:01:56 PM by agent_smith »

Mobius

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This is in reference to my previous post (Knot Test).

Images of test equipment...

EDIT: The load cell I would really like to own is the rock exotica 'enforcer'.
It is the best in its class. But, very expensive to purchase here in Australia (AUD $1200.00).
Link: https://www.rockexotica.com/enforcer-load-cell
Brilliant engineering - made in USA.

Maybe one day a kind IGKT member living in the USA might be able to do a deal with me (I transfer private payment and we organize cheap shipping to Australia).

Thank you for sharing agent_smith.

BTW, there is a significant difference between the equipment you use to 'test' with and what a 'knot trialler' like myself, with my own modest measuring equipment, can achieve at home. I might be asking you for tests from now on ;D

agent_smith

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per Mobius:
Quote
BTW, there is a significant difference between the equipment you use to 'test' with and what a 'knot trialler' like myself, with my own modest measuring equipment, can achieve at home

Hardly (not in a derogatory sense, rather - that I myself identify as a 'backyard tester' - with limited resources).

I find this word play on trial versus test amusing (not in a derogatory sense, but simply in terms of such close dictionary definitions)
Trial definition: https://dictionary.cambridge.org/dictionary/english/trial
Test definition: https://dictionary.cambridge.org/dictionary/english/test

As a 'backyard tester' like me, there is little real-world difference between us.
I have a load cell (and this is likely a key difference - but see below...any force measurement device could be used).
You could also purchase a load cell - or at least some type of device that is capable of measuring force.

The following is simply examples of different options...it is not an inventory of what you may or may not possess!
I have a 2 ton lever hoist - which cost me less than AUD $100.00 (although you could rig your own system by just using some pulleys). If you have a small boat - you could use the winch that pulls your boat back on to the trailer.
If you have a 4WD vehicle with a winch on the bull bar, you could use that...
If you have a 'high lift' jack, you could use that.

My camera is an el cheapo compact pocket digital which cost me about AUD $100.00 (although these days, the camera on a typical mobile/cell phone produces very high image quality (better than my little pocket camera).
« Last Edit: August 01, 2018, 05:20:40 PM by agent_smith »

Mobius

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per Mobius:
Quote
BTW, there is a significant difference between the equipment you use to 'test' with and what a 'knot trialler' like myself, with my own modest measuring equipment, can achieve at home

Hardly.

I find this word play on trial versus test amusing.
Trial definition: https://dictionary.cambridge.org/dictionary/english/trial
Test definition: https://dictionary.cambridge.org/dictionary/english/test

As a 'backyard tester' like me, there is little real-world difference between us.
I have a load cell.
You could also purchase a load cell - or at least some type of device that is capable of measuring force.
I have a 2 ton lever hoist - which cost me less than AUD $100.00 (although you could rig your own system by just using some pulleys). If you have a small boat - you could use the winch that pulls your boat back on to the trailer.
If you have a 4WD vehicle with a winch on the bull bar, you could use that...
If you have a 'high lift' jack, you could use that.

My camera is an el cheapo compact pocket digital which cost me about AUD $100.00 (although these days, the camera on a typical mobile/cell phone produces very high image quality (better than my little pocket camera).

Please desist in quoting the dictionary at me, it is not the first time you have done it, and it is easily construed as being an act that attempts to demean me. I have ignored this in the past, along with usually (at best) dismissive comments from you that are inappropriate.

Secondly, there is nothing wrong with using the word 'trial' as opposed to the word 'test'. Used in the way I am using it is the more appropriate word. Some more research on your part is required, though I can play it your way and guide you to a reference if I must. However, you might find my doing so a slight.

That you presume to know my knot rig well, along with its strengths/limitations simply astounds me. The technical specifications for my knot rig are significantly less accommodating for doing the level of knot testing you can achieve. I have evidence for this assertion, you have nothing it seems.

If you want to apologise to me then I assure you, I can move on and we can both (hopefully) be careful to treat each other with respect in our comments. If not an apology from you, then please find some self-restraint and leave me alone. For my part, I won't respond to your posts in the future.







« Last Edit: July 30, 2018, 10:46:46 AM by Mobius »

agent_smith

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Previous comment from me:
Quote
I find this word play on trial versus test amusing.

I find many things in life amusing.
I am allowed to find the insistence of use of one word over another similar word amusing. Amusement by itself is not an act of demeaning anyone.

Quoting dictionary references also isn't an act of demeaning anyone - its simply referring to external authorities for definitions.

Quote
That you presume to know my knot rig well, along with its strengths/limitations simply astounds me.
I think you place your own interpretation on a perceived construction of my words. You did it before in relation to the Riggers X bend where you thought that I stated that Xarax 'discovered it' - when I never stated anything of the sort. Remember that? You never responded to that...

And now you are doing it again. If you read my words very carefully, there is no presuming anything about knowing your "knot rig" (presumably you mean some sort of 'test' rig?). All I was doing was pointing out various ways that you might be able generate force (ie various options).
Can you point to the exact words where I stated that I presumed to know your "knot rig"?

Quote
The technical specifications for my knot rig are significantly less accommodating for doing the level of knot testing you can achieve.

Okay... I was simply stating that you can use anything to generate force. It doesn't have to be a lever hoist! The force generating 'machine' is actually irrelevant. The knot doesn't know what is pulling on it - it merely responds to a force. Does it really matter how you generate a force?
I had previously used my 'Hi-lift' 4WD jack to generate a force on some knot tests. And, I once used my electric winch mounted on the bull bar of my 4WD. I have also used my next door neighbour's boat winch on his boat trailer.

I did state that I have a load cell. Obviously, for the sake of accuracy, you need to have some means to measure force - right?
You could use fish scales (hook-to-hook)?

Quote
If you want to apologise to me then I assure you, I can move on and we can both (hopefully) be careful to treat each other with respect in our comments.
???
What exactly am I apologizing for?
I already treat you with respect. In science, others need to confirm or refute a persons theory of hypothesis - thats how science is done. If someone refutes your theory or hypothesis, does this make them 'a bad person' -  should a person apologize for being in disagreement?

Quote
If not an apology from you, then please find some self-restraint and leave me alone. For my part, I won't respond to your posts in the future.
Does that mean no one is permitted to refute any of your findings? And that it is only permitted to agree with and confirm your position?
I guess you'll just have to not respond to my posts in the future.
Is anyone permitted to disagree with you?

By the way, nothing I have written is intended to defame, demean or slander you. I am simply responding to your allegations.
« Last Edit: July 30, 2018, 11:46:16 AM by agent_smith »

Dan_Lehman

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Ahhhh, loverly to see actual-factual knots images ! ! !
 :D

This is an addition to my test report in relation to #1425A Riggers X bend.

I increased the load to 10.0kN.

Result: Jammed

My original test report has been updated to reflect this new finding.
I have also advanced a theory which needs to be confirmed or refuted.
But this looks like you changed ropes between those
BWII worn ropes of the earlier trio of loadings and
here comes a white rope (which is the jamming half)!?

Also, in the trio of BWII (3 loadings) knots above,
it looks to me that the 2nd & 3rd images are in
opposite orientations --i.e., the tails have changed
sides, insofar as one can ID the tail from blue-fibre
tracer & burned marking; AND in the amount of
each tail that has been pressed into the bight
of the respective collars (note in the jammed
white rope, there is no tail part keeping open
its collar --one of the points of the Xing!) ?!

IMO, for the jamming pair --and like cordage--,
one might anticipate behavior (incl. compression
flattening of parts) by setting the knot tighter
than one might in less deformable (and less
able to take such loads!) material!?  --thinking
that in the nylon the knot achieves but then
moves past an ideal geometry?!

One can contrast the special, careful dressing
and setting of SmitHunterMan's bend with that
of #1452 --attention to orientation needed, but
hardly so carefully-- & #1408 & the zeppelin
& #1425 ... .

One should also pause and consider likely behavior
in cases of unequal ropes --possibly like diameters
but low-elongation joined to dynamic, old to new!?


--dl*
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