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