Author Topic: Knot testing - Life support knots - procedures and results  (Read 38507 times)

beau

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Re: Knot testing - Life support knots - procedures and results
« Reply #60 on: January 31, 2011, 12:17:14 PM »
*bump*
Any progress on these tests? There seems to be a lot of conflicting information on which bowline variant or which life support knot is the best.
Hardly any sites includes some real sources/test data. ie the yosemite finish is supposed to make the normal (claimed to be rather weak) bowline strong but I can't find any source.

Wouldn't the YF just lock the normal bowline? How does it make it stronger besides locking it?

The same goes for the double(-knotted) bowline. Is it actually proven to be stronger (and why?) or is it just harder to capsize?

Beau

Dan_Lehman

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Re: Knot testing - Life support knots - procedures and results
« Reply #61 on: February 01, 2011, 05:38:41 PM »
Hi, Beau.  Agent_Smith has been silent & inactive for some time,
and I suppose that is answer enough to your question insofar as
his testing is concerned.

For may part, I have not yet sought testing of this particular focus,
but did include a sort of *Fig.8/false bowline* among 5 eyeknots I had
tested in 8mm(5/16") 12-strand urethane-coated HMPE (Dyneema
SK-75); it did not slip, but was unremarkable re strength (somewhere
in the range of results from 33-42% (37%) for the five, each test
specimen having the same knot on each end (so, one survivor).

As for the bowline with Yosemite finish (which exact finish one can
see differing between various references, as to which side of the
S.Part it lies --tighter vs. less tight final turn), I concur in your
questioning of how that could influence strength --though it is
an assertion made by Craig Connally, author of The Mountaineering
Handbook
, there and in posts to RC.com (www.rockclimbing.com).

Quote
The same goes for the double(-knotted) bowline. Is it actually proven to be stronger (and why?) or is it just harder to capsize?

By which name I assume you mean what is also named "Round turn" &
"Double" bowline --an extra (round) turn for the central nipping part,
same end-forms-bight finish.  Tests have shown this to be stronger, I
believe, and about the same strength --so, YMMV.  What you almost
NEVER see in test reports is a clear indication of the exact geometry
of the tested item : no, you have a name --e.g., "Fig.8 on a bight"--
and that can denote all sorts of dressings of some general knot.
Capsizing I don't think is much an issue with bowlines, though for
some reason, many in the mooring hawsers of trawlers within my
periodic inspection seem to have them(!?).  What the extra turn
in the Dbl.Bwl. does is provide a better grip (for security) and
the extra turn helps impede loosening, in that any slack feeding
into the knot had 2 vs. 1 loop to loosen --the slack is *amortized*
over twice the looping --so, some small benefit.

Quote
which bowline variant or which life support knot is the best

Define "best" --there's the rub.  Or, for that matter, how much better
one knot should be over others in order to gain such acclaim?  Often
there are trade-offs between
  • ease of understanding vs.
  • tying vs. "strength" vs.
  • security (when slack, most often) vs.
  • ease of untying vs.
  • material consumption vs.
  • ease of inspecting vs.
  • being in common knowledge/use
!!!

E.g., the Fig.8 eyeknot is often promoted over the bowline because
--in part-- it is supposedly easier to inspect (for correct tying)
(even though precise geometries of this common knot are seldom
presented for instruction --anything is correct enuff!), but MUCH
of the problem with the bowline, IMO, is the way it is presented,
showing it from a side in which the crossing of the central
nipping loop is beneath the easily understood/perceived paths
of the legs of the end bight!  --geeesh, just flip that knot around!
But presentation after presentation show the bowline from the
wrong perspective, and ... people have difficulty understanding
the knot.  Then, with the result of a sort of corollary, non-practice
makes imperfect --self-fulfilling prophesy.  (Concerns about Bwl.
security are valid, but many solutions are available; but then it's
the "many" aspect that frustrates learning and common understanding.)

As for
Quote
... claimed to be rather weak [bowline, i.e.]

no, the bowline is not all so weak, maybe esp. in the cordage used
(perhaps esp. in dynamic rope).  But the figures do have a range,
enough again to make you want to know the unreported details
of knot geometry and so on.

--dl*
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agent_smith

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Re: Knot testing - Life support knots - procedures and results
« Reply #62 on: February 10, 2011, 02:06:44 AM »
Silent and inactive - I'm afraid Dan is correct.

Reasons: Work load too high, global financial crisis hit me, have been in hospital 3 times in 2010 with blood clots in my lungs, cost and time given to this project became too high...etc etc.

I am slowly getting back on track and will return with more test data soon.

Random comments:

[ ] I have developed what might be a new joining knot (ie bend) - but I haven't really looked too hard to check if it already exists or has already been discovered (eg by xarax or someone else) - if it is 'new', I'd like to put it through its paces...
[ ] I had some issues with violent recoil of my load cell during knot break tests - and I was concerned about risk of damage (it cost over $2000.00 AUD to buy).
[ ] I hate threading tracer cotton threads through the test specimen knots - its time consuming and damn tedious, not to mention eye strain for a 49 yr old! (but yes, Dan Lehman is correct that it is a cheap and effective marker system)
[ ] Quality photos of knots has always been an issue - but i solved that problem last year and figured out how to achieve good resolution images with neutral white background - check my 'knot study guide' out at my www.paci.com.au website (under public downloads) to see the image quality I am now achieving.
[ ] I agree with Dan Lehman in that most so-called 'knot testers' publish ambiguous or inaccurate results - or results that cannot be reproduced (after all, any scientist will want to be able reproduce another testers results in order to 'validate' or disprove it). I have taken all of his comments on board so that i do not make the same mistakes others before me have made. For example, I consider pure knot strength to be almost irrelevant - of greater importance is security and stability (my theory only). Tests must capture the elements of stability and security - rather than simple breaking loads
[ ] All my testing to date has been with 'thin' 5.0mm or 6.0mm diameter kernmantel construction synthetic cord (yes Dan, I spell it the German way since it is a German word). I have a feeling (not very scientific) that results obtained with larger diameter rope - eg 11.0mm - may be different. My theory is that larger rope diameters will produce larger radius bends/turns/wraps when compared to thinner diameter cords - which in turn should reduce compression/tension (ie outer radius stretching) of rope fibres. I would expect to see variations in results with knots that employ 3 rope diameters inside nipping loops/turns. Testing will either prove or disprove this theory.
[ ] I am self-funded - and sometimes money is tight.

Mark Gommers
« Last Edit: February 10, 2011, 02:09:21 AM by agent_smith »

Dan_Lehman

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Re: Knot testing - Life support knots - procedures and results
« Reply #63 on: February 10, 2011, 04:54:50 AM »
[ ] I hate threading tracer cotton threads through the test specimen knots - its time consuming and damn tedious, not to mention eye strain for a 49 yr old! (but yes, Dan Lehman is correct that it is a cheap and effective marker system)
[ ] Quality photos of knots has always been an issue - but i solved that problem last year and figured out how to achieve good resolution images with neutral white background - check my 'knot study guide' out at my www.paci.com.au website (under public downloads) to see the image quality I am now achieving.

Firstly, very sorry to hear of your health problems; may they forever
be behind you.

As for threading, well, I got to taste my own medicine,
"to feel your pain" --had some knots tested and of course
wanted to know something more than numbers associated
with them.  I'm attaching a photo taken pre-testing.
AND you'll note that there are also --all eyeknots-- two
knots per specimen : one will break, the other will help
answer the question of Where & thus Why.
(8mm 12-strand Dyneema SK-75)

Good to hear from you, Mark!


 :)

Dan_Lehman

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Re: Knot testing - Life support knots - procedures and results
« Reply #64 on: February 18, 2011, 06:37:54 PM »
Random comments:

[1 ] I have developed what might be a new joining knot (ie bend)
 - but I haven't really looked too hard to check if it already exists
...
[2 ] Quality photos of knots has always been an issue - but i solved that problem last year

Putting 1 & 2 together, I think that we should be seeing
an image of this potential *new* knot, then!  Where is it?

Quote
check my 'knot study guide' out at my
 www.paci.com.au website (under public downloads)

I tried --four times--, but each time, as the downloading small
indicator with a filling-up-left-to-right bar moves to near completion,
it POOPH abruptly stops and quits, almost finished.  I don't know if
my system is bumping into some 4mb (or less) cache-ing limit or
what; I'm just not seeing this file
Anybody else able to view this "knots" (Oct'10) PACI Dowload (top item)?

--dl*
====
« Last Edit: February 19, 2011, 12:49:44 AM by Dan_Lehman »

SS369

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Re: Knot testing - Life support knots - procedures and results
« Reply #65 on: February 18, 2011, 07:18:12 PM »
Hello Dan,

I am able to view the pdf file.
I could save it and email it to you if you wish.
It is only 4.16MB

SS

Sweeney

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Re: Knot testing - Life support knots - procedures and results
« Reply #66 on: February 18, 2011, 07:32:28 PM »
The pdf on this web page may be of interest. http://www.hse.gov.uk/research/crr_htm/2001/crr01364.htm. The HSE is the Health and Safety Executive in the UK (a government body who enforce health & safety legislation but who also sponsor research). The paper was done in 2001 but has some data about knot testing which may be of interest.

Barry

Dan_Lehman

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Re: Knot testing - Life support knots - procedures and results
« Reply #67 on: February 19, 2011, 06:11:38 AM »
I am able to view the pdf file.
I could save it and email it to you if you wish.
It is only 4.16MB

SS

Thanks, I might have to try that.

Agent_Smith, I see that bloody "password" now, but nothing
in my course of trying to download the file asked for any
password.  I do seem to have landed a file but Preview cannot
read it, and ... .  Got the Bowlines one w/o trouble.  Is the
Knots one a different PDF version?


 ???

SS369

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Re: Knot testing - Life support knots - procedures and results
« Reply #68 on: February 19, 2011, 02:22:43 PM »
Hello Dan,

the password for the 01 knots pdf file is            thank you.
The file is safe by very updated virus scan.

I suspect since it is password protected, your preview pane will just show the Acrobat icon.
Let me know if I can help.

SS

Dan_Lehman

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Re: Knot testing - Life support knots - procedures and results
« Reply #69 on: February 20, 2011, 02:57:56 AM »
I saw the password ; but I never have a point in which to USE it
(tried tacking '?=password=thankyou' onto the URLink --it made
no difference (which itself is interesting!)).

I've heard from another that this seems to be an issue of different
versions of Adobe PDF --this requiring 8.0 maybe, as it reportedly
doesn't work on 6.0.  (I have viewed the file in the library, btw.)
(And that upgrading Adobe requires updating an OS --PITA just for
incompatible PDF  >:(   (this for a windows user; I don't know that
from Apple's Leopard it's not possible)

--dl*
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SS369

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Re: Knot testing - Life support knots - procedures and results
« Reply #70 on: February 20, 2011, 03:05:13 AM »
For me, all I had to do was double click the file, a small password requesting window opens,  typed in the password and voila.

I don't know what version of Acrobat you're using, but I would update it soon. The newer versions of the reader plug up some of the vulnerabilities that nogoodnicks can exploit.

If you need this literature, we can think of some way to get it to you.

SS

Bob Thrun

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Re: Knot testing - Life support knots - procedures and results
« Reply #71 on: February 22, 2011, 05:07:38 AM »
For me, all I had to do was double click the file, a small password requesting window opens,  typed in the password and voila.

I don't know what version of Acrobat you're using, but I would update it soon. The newer versions of the reader plug up some of the vulnerabilities that nogoodnicks can exploit.
The vulnerabilities are of concern mainly for PDFs of unknown origin that may be malicious.  Acrobat can make password-protected PDFs that are compatible with earlier versions of the Reader.  I note that none of the other PDFs on the PACI site are password protected.