Author Topic: Scott's lock Bowline (3D) VS #1010 (2D)  (Read 2477 times)

agent_smith

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Re: Scott's lock Bowline (3D) VS #1010 (2D)
« Reply #15 on: February 28, 2018, 06:38:27 AM »
Thanks for these tests Alan.
I particular enjoyed the music The good the bad and the ugly in the Scotts locked Bowline v Scotts locked Bowline.

I concur with Scott in his general observations.

Knot failure (in broad general terms) usually involves a combination of:
[ ] localized heating caused by friction
[ ] localized compression/squeezing
[ ] unequal loading across the cross-section area of the rope (compression on one side versus shearing on the opposite side)

The injection of force into the knot core is the trigger for these effects.

Dan and I have been discussing the terms 'ratcheting-out' and 'drawing-out' of rope material from the core of a knot under increasing load.
Dan Lehman's strict definition of 'ratcheting-out' of rope material imputes a one-way effect - with no rope retracting back into the core.

In Scotts locked Bowline test video (dual Scotts locks), when Alan removed load to stop and examine the knot (at 4:08 elapsed time) - rope material recoiled back inside the core/nub.
This is likely due to the fact that Bowlines are jam resistant.

With regard to the puff of white powder/particulates - Alan isn't using an expensive 'high-speed' camera.
But, given that the puff was commensurate with the yield point being reached - this is a smoking gun in support of Scotts observations (pun intended).
As for notions sniff tests and being able to smell anything, the small quantity and transient rapid dispersal of particulate residue would make it unlikely that Alan smelled anything.
Being able to smell or not smell is not a deal-breaker in my view. One of my colleagues here in Australia has no sens of smell - so if he were present, he wouldn't smell anything.
High-speed cameras are a fantastic tool but they can be prohibitively expensive for home-brew testers.

Mark G


« Last Edit: February 28, 2018, 06:50:13 AM by agent_smith »

alanleeknots

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Re: Scott's lock Bowline (3D) VS #1010 (2D)
« Reply #16 on: February 28, 2018, 06:09:30 PM »
Hi All,
         I saw little puffs of smoke mix with fine pieces of fibers flying out, and heavy odor smell, it is very unusual.
         usually after the knot broken and when I get hold of the knot very close to me,  then I can smell a very light odor smell,
         maybe the rope had been contaminated with oil or grease along the line, seem like some how the hot melting gas was trapped
         in a small pocket inside the nub. when the knot break, it releases and shooting it out.
         
        Mark, I am working on your Offset knots, Will post it the next few day.

        siriuso, I find not all 3 rope diameters inside the nipping loop would boost the MBS yield of the knot.
                   We have discussed a little bit before about 3 rope diameters inside the nipping loop may or may not raise
                   the knots MBS yield?
                   see this link   https://igkt.net/sm/index.php?topic=5383.msg35987#msg35987
                   謝謝 alan lee.

agent_smith

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Re: Scott's lock Bowline (3D) VS #1010 (2D)
« Reply #17 on: March 01, 2018, 12:47:52 AM »
Quote
maybe the rope had been contaminated with oil or grease along the line
Hi Eric, this concerns me.
Contaminants would skew your test results.
Do you think this may have been an isolated (one-off) event or could this have also occurred in other tests?

With all the discussion on puffs of white powder, sniff testing and contamination risks - it reminds me of just how difficult it is to setup a test and carry it out.
It can be a thankless job.

...

I think with all the testing that you have done to date - what some people are looking for is a summary or conclusion from you.
Every test series needs to wrap up with a final conclusion based on results/observations.
I think that the issue of 3 rope diameters inside the nipping loop of a Bowline is still a 'cold case' - and needs to be wrapped up with a concise conclusion/summary.
This will also open the way for other testers to verify or refute your results (that's how science moves forward...others need to do follow up tests).

Mark G