International Guild of Knot Tyers Forum

General => New Knot Investigations => Topic started by: Tim on June 23, 2018, 12:50:25 AM

Title: Research Project using a possible new knot
Post by: Tim on June 23, 2018, 12:50:25 AM
Hi
I am a mature student doing an engineering degree. I am just starting my research project into a hitch that can give a splice a 'good run for its money' regarding its strength (to be used in extempore construction tensioning situations).

The tests so far have been hitch v hitch to determine the strongest hitch. I think I have found one that is new as I can't find it in ABOK, and it beats all other hitches I have tested it against.

Can anybody tell me if it has appeared in any books etc or has been referenced before?

It is two round turns followed by one half of a double fisherman's knot.

(I am guessing it can also be described as two round turns followed by a double overhand knot [I think]).

If it is found to already be in use or documented then I will use its given name in my research project. If there is no record or reference to it anywhere then I will call it 'The Stewart Hitch' (here's hoping).

I look forward to any replies.

(http://)

Title: Re: Research Project using a possible new knot
Post by: SS369 on June 23, 2018, 03:42:00 AM
Hello Tim and welcome.

If you would show us a loosened photo and the tying method, preferably step by step pictures, we can go forward.
The picture you have shared does not reveal enough details.

Thank you.

SS
Title: Re: Research Project using a possible new knot
Post by: Dan_Lehman on June 23, 2018, 08:21:01 PM
If you would show us a loosened photo and the tying method,
preferably step by step pictures, we can go forward.
??
The words
 "It is two round turns followed
  by one half of a double fisherman's knot."
should be perfectly perspicuous!
And "scaffold knot" be the indicated family.   ;)

--though as often with e.g. angling knots I'm puzzled
at how there could be (much of) any difference in strengths,
when so much force should be taken by the round turn(s),
and then pretty much anything I'd think would be ample
to do the job beyond that!?


--dl*
====
Title: Re: Research Project using a possible new knot
Post by: Dan_Lehman on June 23, 2018, 08:26:13 PM
The tests so far have been hitch v hitch to determine the strongest hitch.
Can you present your results of this A-vs-B testing?
What have you tried, and how have the candidates
ranked?
Quote
I think I have found one that is new as I can't find it in ABOK,
and it beats all other hitches I have tested it against.
I think you've found the scaffold hitch, aka "poacher's
hitch"
, with an extra round turn or two --which
difference should be understood as trivial.

Let me ask you to try this, er tie this, "double overhand"
in the form of an anchor bend/fisherman's bend;
the thought is that the line is brought into the knot
more kindly to the noose's SPart than is done with
the strangle-knot form of dbl.oh..


--dl*
====
Title: Re: Research Project using a possible new knot
Post by: Tom_Zal on June 25, 2018, 01:09:44 AM
Would this be considered a tensionless hitch? It seems to meet the definition at http://www.animatedknots.com/tensionless/ if we can infer that the method of securing the free end is irrelevant (several alternatives are suggested).

I know the tensionless hitch is generally used with an anchor object much larger in diameter than the rope (and that in this case it theoretically maintains 100% of the strength of the rope). I don't know if tying it around a smaller anchor makes it a different knot...
Title: Re: Research Project using a possible new knot
Post by: agent_smith on June 25, 2018, 03:24:38 AM
Hello Tim,

There is absolutely nothing 'new' in this hitch that you have presented.

Looks like 'Tom_Zal' beat me to the punch and I concur with his view that all you have done is tied a 'tensionless hitch' (#2047).
Your depicted tensionless hitch is then secured with a strangled double overhand knot.

There are numerous ways to secure a tensionless hitch. The simplest method is as you have depicted - which is to tie a strangled double overhand knot around the SPart (standing part).
Link: http://www.animatedknots.com/tensionless/

A tenionless hitch operates in accordance with the capstan equation.
Link: https://ipfs.io/ipfs/QmXoypizjW3WknFiJnKLwHCnL72vedxjQkDDP1mXWo6uco/wiki/Capstan_equation.html

This structure actually functions as a noose.

And Dan Lehman is correct that the noose is based on the Poachers noose (#409) and scaffold noose (#1120).

Mark G
Title: Re: Research Project using a possible new knot
Post by: Groundline on June 25, 2018, 03:19:58 PM
After inspecting and tying the knot in 5.JPG I see, get, a constrictor knot tied around its own standing part.
Title: Re: Research Project using a possible new knot
Post by: knotsaver on June 25, 2018, 04:20:12 PM
After inspecting and tying the knot in 5.JPG I see, get, a constrictor knot tied around its own standing part.

no Groundline, not a Constrictor, but a Transom (or a Strangle) that is to say a Double Overhand... ;)

have a look at
http://igkt.net/sm/index.php?topic=1462.0
and
http://igkt.net/sm/index.php?topic=5258.0

Ciao,
s.


Title: Re: Research Project using a possible new knot
Post by: alanleeknots on June 25, 2018, 05:29:50 PM
       Hi All,
                Climbing with a pair of slipper ?
                 謝謝 alan lee.

                 http://www.yachtingmonthly.com/sailing-skills/strongest-sailing-knot-30247
Title: Re: Research Project using a possible new knot
Post by: Dan_Lehman on June 26, 2018, 12:44:36 AM

       Hi All,
                Climbing with a pair of slipper ?
                 謝謝 alan lee.

                 http://www.yachtingmonthly.com/sailing-skills/strongest-sailing-knot-30247
MANY THANKS, ALAN, FOR
 [edit : helping ME to...] FINDING THIS TEST REPORT!

(And, yes, climbing in sandals is worth a remark.   ;)  )

Now, who has read the report, and what
observations can you give about it?!

--dl*
====
Title: Re: Research Project using a possible new knot
Post by: Dan_Lehman on June 26, 2018, 01:40:44 AM
The hitch I have mentioned does include some of the scaffold knot,
but because of the inclusion of the two round turns [i.e., just one more...],
I believe it is a new hitch,
 unless exactly the same hitch can be found in literature or reference elsewhere.
Tim, with respect, this is simply silly : adding one
more round turn (i.e., repeating what exists already)
does NOT win you (m)any points for inventiveness!
(You might gain something for presumably realizing
--though possibly in retrospect to trial&error-izing  ::) --
that the "tensionless hitch-ing" aspect needs this further
wrap against so smooth an object (vs. cavers e.g., tying
around the rough bark of a tree).)

Quote
My reasoning for the above paragraph is as follows:

The single overhand knot is known as 'The Thumb Knot'.
Add another overhand knot, it becomes a double overhand knot
known as a 'Blood Knot' (ABOK p84. Knots 515 & 516).

''The round turn and two half hitches is named by steel in 1794''.
A totally separate knot mentioned shortly after the first knot states
''Two round turns and two half hitches, so called by Dana in 1841''.
(ABOK p296. Knots 1720 & 1721).
Now you're definitely getting silly!
Firstly, you don't "add another overhand knot" to get a dbl.Oh
but add a 2nd tuck (in pretzel form) or --more insightfully/significantly--
a (first!) *wrap* in the strangle knot form, to do that.
(Doing what you say would be stoppering the initial overhand.)

Quote
I expect I could find more examples of different knot/bends/hitches
which> [that] are made up of parts of some other configuration.
Oh, heck, why go "different" : you can find the SAME knot
getting different names, if name-glory is what is wanted!   ;D
(... noting that e.g. "blood knot" attaches to other things, as well)

Quote
But my point is I still think my hitch may be new as I can't find anything exactly like it.

It is also of importance to be recognised as a separate entity
because of the fact it is not a fancy decorative knot,
it is a practical hitch that may have the potential to be used
in constructional tensioning applications in the future.
NO.  Rather, it is more important to have an understanding
of knots & their purposes and effects/workings such that one
can readily adjust to particular circumstances by such simple
means as furthering a structure (such as wraps) or adding
a stopper knot or ... .  E.g., when Heinz Prohaska presented
his --my name, here--> ProhGrip friction hitch (aka "Blake's h."),
he added the commentary that if the hitch can still not hold
so surely in stiff rope, then add a further wrap with the tucked
tail (i.e., a further 2-dia. wrapping); or if the slippage seemed
attributable not to inflexibility buy slickness, add wraps of
the single-diameter end of the structure.  I.e., he did NOT
merely introduce the JUST-THIS-#-OF-TURNS knot; he gave
us a good idea of a structure that could be manifest in various
forms!
Given an overhand, adding a wrap to it to get the
strangle is a significant gain, as the first knot has no
such press-against-the-crossing part; adding further wraps
is just furthering what the first addtion presented, but is not
additionally creative.
(And as far as hitching to something, one must beware
that not all objects will accommodate multiple turns!)

Quote
My decision to test which knot/hitch against which knot/hitch came about from
over 35 years of working with ropes at sea both professionally and leisure,
and from rock climbing for leisure. I was also drawn to an online article in
Yachting Monthly (May 2015) which was conducted by Marlow Ropes.
http://www.yachtingmonthly.com/sailing-skills/strongest-sailing-knot-30247
 
OH, and I just boldly and colorfully thanked Alan for this
--so much for quick scanning ... .  <sigh> :P  I'll go do an edit ... .

And did you read this report carefully, attentively,
eyes open and not kneeling to this apparent *authority*?!
Because there are some eye-opening assertions in this!
(I'll refrain for time and for giving others I hope the chance
to do some critical reading/thinking themselves.)

Quote
My pilot tests were as follows.

Bowline v Round turn and two half hitches
- The round turn and two half hitches won outright 4 times out of 4 (as expected, based on work and climbing experience, and also Marlow Rope's online testing).

Looped double fisherman's (Scaffold hitch) v Round turn and two half hitches
- The round turn and two half hitches won outright 4 times out of 4 (as expected, base on work experience and based on Marlow Ropes online testing).
[?? Expected based on Marlow?  Why, their (dbl.) scaffold --no RT-- beats RT+2hh]

Round turn and one half of a double fisherman's (Scaffold hitch with a round turn) v Round turn and two half hitches
- The Round turn and one half of a double fisherman's (Scaffold hitch with a round turn) won outright 4 times out of 4 (I did not know what the outcome would be here).

Round turn and one half of a double fisherman's (Scaffold hitch with a round turn) v My hitch Two round turns and one half of a double fisherman's (Scaffold hitch with two round turns)
- My hitch won outright 4 times out of 4 (I definitely was not expecting this outcome).
[Why not : the extra turn can only help, one might think.
(Possibly by enabling more slippage through the tightened knot
--i.e, an extra-turn-of-material's stretch to draw tight out through
the noose's knot-- could make it worse, but ... )]


'English Braids' have very kindly provided me with 200 metres of 4mm 12 stranded polyester dinghy control line to continue my testing.

... The next stage is to test my hitch against the splice under different environmental conditions.
[Again, I urge you test the re-casting of the dbl.oh knot's shape
into that of the anchor bend, its turns going AWAY from the object.]

Based on Marlow Ropes online knot test which the round turn and two half hitches is rated very highly against a splice, I have high hopes for my hitch as it outperformed the round turn and two half hitches by far.
[?? Directly, based on Marlow's finding a like noose so strong, getting their hightest break.]


Tim, consider this, with care :: What is the difference
between the RT&clove noose and your dbl.scaffold h. ?!!
THINK, l00k; further think.
Where do the test-reported breaks come?!
(Hint : what knot did I recommend you try --you didn't reply to that?!
Quote
Let me ask you to try this, er tie this, "double overhand"
in the form of an anchor bend/fisherman's bend;
)

Quote
I look forward to any replies

Tim :)
Now, this one's in your rear-view mirror.

--dl*
====
Title: Re: Research Project using a possible new knot
Post by: NautiKnots on June 26, 2018, 03:32:19 PM
Now, who has read the report, and what
observations can you give about it?!
Startlingly poor testing methodology (revealing fundamental misconceptions of knots and cordage) that is used to draw unsupported conclusions which mislead unsuspecting readers. 

Can you tell that I'm unimpressed?

Shame on Marlow Ropes for participating in such a sham of pseudo-science just to get their name in print.

Regards,
Eric
Title: Re: Research Project using a possible new knot
Post by: Dan_Lehman on June 26, 2018, 09:01:10 PM
Now, who has read the report, and what
observations can you give about it?!
Startlingly poor testing methodology
 (revealing fundamental misconceptions of knots and cordage) ...
Regards,
Eric
But we should be specific & comprehensive, so to enable a correct
and helpful result be obtained.  And I think that it's not merely
a right-or-wrong citing, but maybe just an quite unexpected one,
too (along with right-or-wrong things)!
(Going from "testing methodology" to "test method" is a start!   :D  )


--dl*
====
Title: Re: Research Project using a possible new knot
Post by: Dan_Lehman on June 26, 2018, 09:14:07 PM
Looks like 'Tom_Zal' beat me to the punch
and I concur with his view that all you have done is tied
a 'tensionless hitch' (#2047).
Your depicted tensionless hitch is then secured with a strangled double overhand knot.

Goodness, how amazing it is for the knot of this
noose to have so much tension in it, for to be a
"tensionless hitch" !!

(One should be noting behavior** more
than counting turns and likening the structure,
for the above assertion.
.:. The point of the tensionless h. is high strength
via the relatively mildly curved wraps & friction taking off
all of the load,
and thereby enabling release while loaded by
simply unclipping the trad. 'biner on the noose's SPart.
But in cases we're seeing in Marlow's test and presumably
w/Tim's, the >>knot<< is getting much tension --enough
to so constrict the >>noose's<< SPart (not the knot's)
that the break occurs there !

**Though, I'm usually against deciding knot type/class
by behavior vs. structure --as the former will differ so
much over circunstances, and we don't want to have
shifting categories/classes to match!)

!?

--dl*
====
Title: Re: Research Project using a possible new knot
Post by: NautiKnots on June 26, 2018, 10:47:28 PM
But we should be specific & comprehensive, so to enable a correct
and helpful result be obtained.  And I think that it's not merely
a right-or-wrong citing, but maybe just an quite unexpected one,
too (along with right-or-wrong things)!

Ok here are some of the problems that caught my attention:Given the number and severity of these issues, I think its wrong to draw any conclusions about "best knots" from these tests.

Marlow Ropes provided the test lab and presumably knows how to use it properly.  They should have given the author guidance on devising and performing tests that would yield meaningful results.

Such an obviousy flawed article makes me doubt the veracity of everything else published in Yachting Monthy.

Regards,
Eric
Title: Re: Research Project using a possible new knot
Post by: Dan_Lehman on June 27, 2018, 07:40:22 PM
Great, thanks!
I'll first just insert/add comments; it will take some time
to put together my list (but I might make some mention here).

But we should be specific & comprehensive, so to enable a correct
and helpful result be obtained.  And I think that it's not merely
a right-or-wrong citing, but maybe just an quite unexpected one,
too (along with right-or-wrong things)!

Ok here are some of the problems that caught my attention:
  • It appears that the author tested only one sample of each knot in each type of cordage. ... .
      Here I'll want to depart, for the implied cost of testing
      quickly becomes prohibitive --as there are many factors to cover,
      and the need-so-many-test-cases sends the total skywards!
      .:.  There needs to be some way to make limited testing work.
      (Perhaps by testing multiply knotted specimens, which would in
       less material and one running of device produce "at least this much"
       force measures for the lot, though only one knot might fail (some
       others might show beginnings of failure.  That would be giving a
       "least force" break, which in any case is what users want! )
  • The author did not identify the Dyneema and twisted cordage used, ...
      Yes, and from a place that must have just that information.
      Well, one can try to match appearances in the product catalogue ... .
  • The author compared measured breaking load to rated breaking strength (average or minimum?  - didn't say). ...
       Was this in fact explicitly stated (vs. to my quick reading, just ignored)?
       I believe that the Cordage Institute, which has some say in how things
       are marketed --but which (also IIRC) differed from some other standards
       bodies' procedures--, had ruled that spliced strength would be quoted line
       strength (i.e., there would be no sophisticated estimation of tensile strength,
       but rather the practical measure (and maybe of 5 samples?).
  • The author admits that he was supposed to preload cordage to 50% before testing but did not.
      Again, was the absence of such pre-loading explicitly admitted?
      IMO, I found it surprising.  Granted, usage should do something
      in terms of conditioning lines; but common usage (a) shouldn't
      be reaching 50% (!!) and (b) such usage, well, is just that, and so
      should one be guarding line use (like break-in driving of a vehicle)
      on the risk that as new line it is somehow weaker?  --never heard
      this before (and most testing seems to be done with new rope
      which has been provided by manufacturer or ... for the test.
  • The author does not differentiate between knot strength and knot security.  Anybody who has attempted to tie knots in HMPE cordage knows that all the knots tested will slip.  The author, however, reported them as "breaking".
      Well, here we have an issue in the compound structures of
      high-strength (esp. HMPE, it seems) core and protective mantle:
      that loading can be uneven, and esp. that the core does slip within
      the sheath and thus leave the latter to bear force and ... break.
      (Interesting :  I recall some fishline testing in which HMPE line
      was made strong by putting it in some kind of sheath, and even
      then in an overhand knot (!! !?).)
  • The author confuses core with cover in Dyneema line.  He repeatedly refers to "Dyneema cover" breaking.
      Eh, I'll see this not a resulting from so much misunderstanding
      --though I do fault the report from not expressly addressing
      the slippage-of-core issue!--
      but just quick shorthand rope ID --"Dyneema" is the name for
      that particular cordage (and, as you note, one that leaves us
      wondering ... , versus a product ID with specifics.
  • The author assumes that breaking strength is the primary consideration for selecting a knot.
    ... Even when knotted, they will rip the clew out of the sail before the line breaks.
       Agreed, that seems to be the implication.  (And I recall in some
       boating forum someone remarking that after a hurricane had
       ravaged some port/marina, there were no breaks of bowlines
       in mooring lines (to compare vs. splices) --breaks in any rope
       came from hard edges, if ... .
  • In the text, the author notes that it is important to properly taper a splice, but (in the photo provided) it appears that he did not.  Now, I admit that the photo isn't perfectly clear, and I might be mistaken, but if he didn't taper the bury then that would explain why his splice broke where it did, and why it broke at a lower-than-expected load.
      Oh, yes, I was amazed at the splice forces, which as I remark
      above are for some users to be what IS a rope's strength (so,
      by definition, 100%).  And at the end of the stuffing?  --makes
      me wonder what sort of splice, and likely lack of taper, and ... .
      (I don't have much familiarity with splices, but it seems odd,
      and esp. the break forces low.)
  • What about other knots?  The author said he tested the Carrick Bend, but did not report the results.  The Angler's / Perfection Loop would have been an excellent candidate to test, especially in stripped cover Dyneema.
      I noted that, too --re "carrick bend" (which, I'll remark, gets
      rather LOW breaks in some old, natural-fibre climbing rope
      testing, I've recently seen!).
      Also, note that it's a double strangle knot used, per image.
      AND that sometimes the pre-tested tied knot is shown
      in a different orientation to the broken specimen!
      (And I'm having trouble e.g. figuring out the broken
       sheet bend, as NEITHER side seems limited enough
       in high-load abrasion to have been the U-part --but certainly
       not the implied side.
       (In some seen samples, it has been the U-PART THAT BROKE,
       where the *loop* part turns around and constricts it.)
  • Oh, and Get your knots right!  The author admits that he mis-tied the bowline in the twisted rope, but includes it in his test data anyway.  You can't test knots If you can't tie them correctly!
      Yeahhh, but one can dispose of the myth that the bowline
      was all so "mis-" tied!!  The tail-outside version is the one
      less vulnerable to slippage on ring-loading.  AND one can
      dress the knot such that the tail lies neither so
      in the plane left/right of the returning eye leg,
      but *above/below* it --e.g., to anticipate the SPart's draw
      (so that only upon considerable loading does the tail
       then assume the shown-in-book-images position!).
Given the number and severity of these issues, I think its wrong to draw any conclusions about "best knots" from these tests.
  AH, and we're still awaiting MY citations!

Marlow Ropes provided the test lab and presumably knows how to use it properly.
  Should we really presume this?  --might be more of a leap of faith!

  They should have given the author guidance on devising and performing tests that would yield meaningful results.

Such an obviously flawed article makes me doubt the veracity of everything else published in Yachting Monthy.
  You'd be even more appalled at Practical Sailor's 2001-09? testing!
  Cf. www.practical-sailor.com/issues/27_17/features/4578-1.html (http://www.practical-sailor.com/issues/27_17/features/4578-1.html)
   & i.p. www.practical-sailor.com/newspics/charts/27-17-Bench.pdf (http://www.practical-sailor.com/newspics/charts/27-17-Bench.pdf)
    --look at top line comment re the bowline in Yale Light (rightmost col.) !!!

Regards,
Eric
Thanks.
Others?!

--dl*
====
Title: Re: Research Project using a possible new knot
Post by: NautiKnots on June 27, 2018, 09:13:42 PM
Well, according to a couple of sample size vs. confidence calculators I just used, your chances of getting the "right" answer with a single sample is about 2%.  That is, any given knot breaking strength test yields the "wrong" value 98% of the time.

I use the terms "right" and "wrong" very loosely here, as population sampling is much more complex than that.  A better way of putting it is that the knot test strengths listed in this "study" have a margin of error of 98%.

Which is to say, that the absolute numbers given, and therefore the percentages calculated are meaningless.  Conclusions drawn from those percentages are more likely to be wrong than right.

Yes, it is prohibitively expensive to test multiple knots in different brands/types/sizes of cordage to 95% confidence within a 3% margin of error, but that doesn't make single-sample testing valid.

An anecdotal test is just that - anecdotal.  One cannot draw meaningful conclusions about a population based on a single sample.
Title: Re: Research Project using a possible new knot
Post by: Dan_Lehman on June 28, 2018, 01:50:41 AM
I've taken everything onboard and agree it is the tensionless hitch (thanks Tom_Zal)
I still object to this, as that name is rightly indicative
of the criterion for inclusion --i.e., no tension on the
knot of the noose structure--, and in the case at hand,
we see such tension on that knot that it significantly
(?!  well, do we know the % break?) weakens the
>>noose's<< SPart via constriction.
(It would be like calling the tautline h. or midshipman's h.
--those noose structures that are supposed to be effectively
   adjustable (fixed) eye knots--
"non-slipping adjustable eye knots" even though in many
circumstances they unfortunately slip.)

Quote
Dan, I will also include your recommended hitch within my testing.
What I aim to do is try to improve on the given knot's
constriction of the noose-SPart by having the >>knot's<<
SPart taken farther around the object (more nearly 360deg)
and connecting to the noose SPart away from where some
contact is initially made, considered from the perspective
of that SPart coming into the knot --at which point there
will be the further wraps of the anchor hitch / Blake's h.
which of course will have less tension than the initial
turn which is close to the object.  And with the latter
knot aforementioned here (B.h.), one additionally *pads*
the noose SPart with the tail of the knot.

So, this should remove rupture --at least until a really high
load-- from the entry of the noose SPart into the knot.
. . . in (my) theory.

(Another such attempted amelioration of this constriction
would be to make the few round turns and then tie off
with a timber h. that has a full/round turn or two
around the noose's SPart, and dressing that wrapping
so that both legs of it come at the near-object end of
the coil (so, sort of *"cascading"* what would be the
away end from the pure helix.
(Friction hitches that have many turns can do this
naturally, the away turn being pulled so that it sort
of *un*wraps at the away end and does some broad
wrap up to there.)


--dl*
====
Title: Re: Research Project using a possible new knot
Post by: Dan_Lehman on June 28, 2018, 01:55:29 AM
My short answer is that one looks to ranges of values,
not some "right" one --I guess you're thinking of the
mean of many many samples.  One might do some
full testing of a few things so to get an idea of whether
e.g. cordage has much variance,
and then do scattered testing taking the above as an
assumption and not caring for many samples so long
as the few are within an expected range.

There's got to be a way forward.
And for much of a benefit, not so much particular values
but more for seeing how/where/why things are breaking,
so to build theories to explain (and iteratively seek knots
that would via their particular geometry be good tests
of these) knot failure.

(-;
Title: Re: Research Project using a possible new knot
Post by: agent_smith on June 28, 2018, 03:21:27 AM
Quote
Quote from: Tim on June 26, 2018, 12:40:47 PM

    I've taken everything onboard and agree it is the tensionless hitch (thanks Tom_Zal)

I still object to this, as that name is rightly indicative
of the criterion for inclusion --i.e., no tension on the
knot of the noose structure--

Okay...

There is some difficulty in attempting to define what Tim has tied.
It is not new - that is 100% certain.

The knot is actually a 'composite' structure.
It consists of turns around a pipe/rod/post followed by a strangle around its own SPart (standing part).

As a complete entity - it is a noose. It is not a fixed eye knot.

The first segment of the structure is the turns around a pipe/rod/post - and this is making use of the 'capstan effect'. Tim could just have easily tied his knot around a tree or a bollard on a wharf.

I agree that the common name 'tensionless hitch' is a misnomer.
There is tension in a tensionless hitch! Force enters the 'core' via the SPart. That force is quickly dissipated in accordance with the capstan equation. Note that in the capstan equation, friction plays an important role. Obviously, making turns around a tree in comparison to turns around a carabiner has a different coefficient of friction.

Tim could have kept increasing the number of turns around the carabiner.

As with any so-called 'tensionless hitch', the tail must be secured in some way.
Tim chose to secure the tail via a 'strangle' (ie a strangled double overhand knot). There are other ways to secure the tail...using a strangled type method is economical.

Fundamentally, Tim's knot closely matches #409 Poachers noose.
There is no doubt that fundamentally, it functions as a noose.

One can easily modify #409 Poachers noose by adding an extra turn.

So you could argue that Tim has simply tied #409 Poachers noose with an extra turn.
You can just keep adding more turns to modify #409.

I sometimes use the phrase; "Cant see the forest for the trees".

Some people see #409 Poachers noose.
Some people might see a round turn followed by a strangled double overhand knot.

I think ultimately, Tim has tied a 'composite structure' consisting of:
[ ] A round turn or several turns
[ ] A strangled double overhand knot

As a completed structure, it functions as a noose.

The addition of the extra turns makes use of the 'capstan effect'.

A tensionless hitch makes use of the capstan effect.

One could build a strong argument that Tim's creation consists of a tensionless hitch that is secured by a strangled double overhand knot.

Mark G

Title: Re: Research Project using a possible new knot
Post by: NautiKnots on June 28, 2018, 02:10:23 PM
My short answer is that one looks to ranges of values,
not some "right" one --I guess you're thinking of the
mean of many many samples.
It all comes down to:If a knot always broke under the exact same load, then you would need only one sample to find out what that load was.  If, on the other hand, different instances of the knot break at different loads, then you need more samples to understand what to expect of that knot in the future.  That is, if our goal is to understand and make predictions about the behavior of the population at large, then our sample set needs to be large enough to have the same distribution of values as the whole population.   As the size of the sample set increases, our confidence in the result increases, and the risk of error decreases.

A sample size of one yields a result (in practical terms) in which we have no confidence, and a high risk of error - regardless of what one is trying to measure (average, minimum, or maximum strength).  All you learn is that the overall population contains that value - not what one can expect from other members in that population.  Tests such as those performed by Yachting Monthly and Practical Sailor, which use a single result to extrapolate the behavior of the general population are worse than useless.  They reveal incompetence that borders on negligence.  The results mislead more than they inform.

Quote
One might do some full testing of a few things so to get an idea of whether
e.g. cordage has much variance,...
Depending on what you are trying to determine, and what the distribution of the population looks like, you might be able to get the desired confidence with a smaller sample set, but that size will always be significantly greater than one.  Let's say, for example, you want to know what the probability is of a given knot in a particular rope slipping before it breaks.  So, you start tying samples, and pulling on them until they fail (one way or the other).  If, after reaching 11 samples, you found that 10 slipped and 1 broke, you can conclude that the knot has a 90% chance of slipping, with a 95% confidence in your result, and an 18% margin of error.  If, however, as you test, you find that half of the time the knot slips and half of the time it breaks, you need to take 30 samples to conclude that the chance of slipping is 50% with the same confidence and margin of error.

Quote
There's got to be a way forward.
Wishing for something doesn't make it true.  If you want to model the general population, then your sample set needs to be big enough to accurately reflect the distribution of the whole population. 

I hope that helps,
Eric
Title: Re: Research Project using a possible new knot
Post by: Dan_Lehman on June 28, 2018, 04:07:22 PM
Here are some further comments on the above-cited
Yachting Monthly knots article.

1) "... the strongest knot sailing knot ..."
As noted above already, this "strongest" characteristic
is both not-so-easily-firgured and not really the key quality.

2) To
Quote
the RYA recommends a round turn and two half-hitches
for fastening a mooring line to a pontoon cleat because
it can be tied and untied with load in the line. I?ve always
used a pre-tied bowline dropped over the cleat,
I wonder what happened to the cleat hitch, which also
can be un/tied under load, and was of course intended for cleats!?

3a) In the embedded how-to-tie-some-knots video,
the fig.8 eye knot is supposedly dressed to the dubious
rule of putting some end on the outside; the resulting
knot is a poor excuse for something that has been dressed,
whatever the goal!

3b) The fisherman's knot is tied w/discordant (i.e.,
different-handed) overhand compoents.  There is no
discussion about this aspect, and IMO this is likely the
inferior variation.

3c) The grapevine/dbl.fisherman's knot is deemed the strongest
--and it probably was--, but the guy in the video only shows
his ineptness at knot tying by struggling to make the
component strangle knots,
putting them also in a discordant/opp-handed version,
BUT for the final image it seems that someone (else?!)
stepped in and tied the knot concordantly and with
sufficiently long tails for the camera !!  (I wonder if
this mystery tyer can be rented?)

4) Their stated lack of "proof-loading" to 50% of tensile
strength is a surprising remark, IMO.  I've heard of some
cyclic loading done pre-testing, or otherwise no indication
of such conditioning, and of course of testing non-new
cordage, but ... 50% ?!  That seems high.
And
Quote
Dyneema and Marlowbraid to see how it affected their known strength,
and found that the break load of both lines was reduced to a startling 35 per cent of their ISO specification.
"Startling" indeed. IIRC, pure Dyneema 12-strand (NERopes)
was said to have broken --don't know about any pre-loading--
at about 33% (for some few knots NER broke for me via
Brion Toss's invitation), but that seems low for conventional
cordage.  (One can wonder what "break" means, here, for
as noted elsewhere the "Dyneema" line often broke in the
sheath only.  With this mid-line stopper knot, though, the
"pulled through" potential didn't exist.)

4) "Then we looked at loop knots" :: yes, how surprising
to read that they included these --RT + 2HHitches, anchor bend?!

5) Although there are two mentions/occurrences of
"carrick bend", there is nothing further --no report of
actually testing it (as stated it would be) or showing
a result for it.  (I guess that along with knotting
editing is a lacked skill at Yachting Monthly!)

 - - - - - T B Continued - - - - - -
(Goodness, there is so MUCH to cite.)

--dl*
====
Title: Re: Research Project using a possible new knot
Post by: Dan_Lehman on June 28, 2018, 04:13:36 PM
It's interesting to see that for the dbl. sheet bend
the "Dyneema" & Marlowbraid lines broke at opposite
ends.  I figure this :: there was more slippage of the core
in the *hitching* part than the U-part/bight, so the
former taxed its sheath more (in the yellow hitching
end) and broke there; whereas the Marlowbriad's
like greater constriction by the hitching part around
the bight/U-part's ends led to the break coming in
that U-part's SPart.
In other words, greater constriction was the same,
and the difference resulted from core slippage or not.

IN THEORY ...   ::)

--dl*
====
Title: Re: Research Project using a possible new knot
Post by: agent_smith on June 29, 2018, 12:30:00 AM
Hello Dan and 'NautiKnots'

You guys are drifting way off topic here... but, I definitely like, and am very interested in setting up proper parameters for knot testing and future knot testers in general.

This discussion should be in a new thread.

I find it ironic that the issue of poor knot testing and poor reporting keeps raising its ugly head.
I think the IGKT must accept at least part of the blame/fault that knot testers are continuously getting things wrong.

The IGKT should set up a knot testers page - which could act as a one stop shop for all future knot testers. They can browse to the IGKT forum and review the "Knot testing guidelines'.

Currently, virtually all knot testers act in isolation - with little to no peer reviewing of their work before it is published. They just test and publish = and the same old tired mistakes are repeated endlessly.

I know some members of the IGKT have tried to address this issue in the past but, it has bogged down or run out-of-steam.

Surely we have enough 'experts' in the IGKT to address the issue of knot testing?
Is there any reason in principal why we can't setup a knot testing page to provide a useful set of guidelines and principles for all future knot testers?

I challenge interested members of the IGKT to take this on as an issue to resolve before the end of 2018!

JFK once said... "We choose to go to the moon not because it is easy, but because it is hard"

Surely if we can put boot prints on the moon, we can establish a set of Knot testing guidelines and principles?

Mark Gommers

EDIT / PS

I think a new category needs to be added to this forum - titled:  KNOT TESTING GUIDELINES AND PRINCIPLES

This will make it easier for the general public and interested future knot testers to search and find this site.
Title: Re: Research Project using a possible new knot
Post by: Sweeney on June 29, 2018, 02:00:51 PM

I think a new category needs to be added to this forum - titled:  KNOT TESTING GUIDELINES AND PRINCIPLES

This will make it easier for the general public and interested future knot testers to search and find this site.

I think it would be more accessible if we put agreed guidelines and principles on the main website, perhaps based on a discussion here about what these guidelines and principles might be. Actual results and ensuing discussions would continue to be posted here perhaps with a link from the main website. In theory this shouldn't take too long or create any great disagreement - that comes from results rather than methodology one would hope.........

Sweeney
Title: Re: Research Project using a possible new knot
Post by: Dan_Lehman on June 29, 2018, 03:57:46 PM
Further comments on the Yachting Monthly testing.

6) The RT + 2HH will have different behavior on
smaller vs. larger-diameter objects; with relatively large
ones, the clove h. (the *knot* of this *structure*)
grabs onto the (noose) SPart more than it will on a ring.
(I recall test data where this knot rated higher on a ring
but lower on a pile than the anchor bend --which
I presume did so well on the latter by having its
collar yielding enough to leave the SPart more straight
and arriving tangential to the object (my guess)!?)

One can try to ameliorate the noose's effects by settting
it firmly in an iterative manner of pulling hard on the
(noose) SPart and pushing the knot back snug to the
object --of trying to work tight the round turn.   From
such a setting, the draw of the SPart ought be a little
less on the knot and thus the angle of contact better
and ... .   (need that comprehensive testing to see if ...)

7) Marlowbraid tied in a bowline breaking at just 47%
really surprises me.  One can wonder at why --at whether
the assessed tensile strength, e.g., is too high?  (In
some testing of rockclimbing rope the bowline gets
up in the 70%.  Dave Richards's testing of 12.5mm low=
elongation ("static"), 10mm dynamic, & 7mm "accessory"
cordage got (per 5 test specimens each), resp., 63.3-63.1-67.1%.

8.) The fig.8 eyeknots are hard to figure out from the
report's images, as they are shown in lousy dressings
--which apparently was the case with the broken knots.

I find it most peculiar that for the "Dyneema" rope the
break occurs at one of the eye legs --not in the
SPart ?!?!?  Huh?  --and at only "35%" of some supposed
tensile strength, which should mean only 17% in the
broken part (!!) ?!
Were there some slippage of core, that should pull
core from the eye (as seen with the bowline, e.g.)
and LESSEN (remove!) load from the sheath,
not break it!


--dl*
====
Title: Re: Research Project using a possible new knot
Post by: Dan_Lehman on July 03, 2018, 12:36:41 AM
Quote
There's got to be a way forward.
Wishing for something doesn't make it true.  If you want to model the general population, then your sample set needs to be big enough to accurately reflect the distribution of the whole population. 
If you wanted to know the quality/composition
of a gallon of milk, how many samples would
you take for analysis?  I'm thinking that cordage
is for the most part reasonably assumed to be
pretty consistent, and this could be one factor
in knotted-rope strength (to step away from
attributing strength to *knot* en vacuo!) that
can be reduced in number.

And given some experience in test results with
some knots, one might come to believe that
skilled tyers can replicate at least some knots
well enough to not need as big a number as
might be wanted for more complex knots!?

But we surely aren't going to do all the multiples
of sampling per all the multiples of probable
factors that influence strength --a number that
is huge.

Meanwhile, there needs to be a great tightening
of knot-tying skill and reporting detail, irrespective
of test-specimen count.  (An extra dozen or two
tests of fig.8 eye knots (mis)tied as done in Yachting
Monthly
would not be a help!)

There is this irony :: Dave Richards remarked in his
report on testing 7mm & 12.5mm low-elongation &
10.5mm dynamic kermantle ropes that he was who
tied all of the knots --the implication being that in
this way he ensured some uniformity to their formation
(it actually doesn't necessarily mean even this, were
his tying skill not great and his discrimination among
possible versions lacking!).
Well, even assuming it was so,
the implication must be that HIS results cannot be
so meaningful/applicable to all the rest of us, who
will be tying our own knots (in different ropes)!


--dl*
====
Title: Re: Research Project using a possible new knot
Post by: NautiKnots on July 03, 2018, 01:38:35 AM
If you wanted to know the quality/composition of a gallon of milk, how many samples would you take for analysis? 
Well, that depends on what you want to know about milk.  If you only want to know about that particular gallon at that particular time, you might only need one sample.  Don't, however, expect to make useful generalizations about other gallons of milk.  What if the gallon you had tested had spoiled?  Would you conclude that all milk is spoiled?  If you tested 2% milk, would you conclude that whole milk has 2% fat content?

Quote
I'm thinking that cordage is for the most part reasonably assumed to be pretty consistent
I think that's a faulty assumption.  Would you assume that knots tied in 12mm double-braid spun polyester would hold the same as those tied in 6mm twisted nylon?  How about 3mm single-braid Dyneema?  In terms of the milk test above, would you assume that all breeds of cattle produce the same quality milk?  If so, you'd be sadly mistaken.

Quote
And given some experience in test results with some knots, one might come to believe that skilled tyers can replicate at least some knots well enough to not need as big a number as might be wanted for more complex knots!?

Although unskilled knot tyers might produce knots with greater variability (leading to an increase of samples needed), skilled tyers producing identically dressed knots does not reduce the needed sample size.

Quote
But we surely aren't going to do all the multiples of sampling per all the multiples of probable factors that influence strength --a number that is huge.
True.  That's why it is so important to construct your test carefully in order to actually find out what you'd like to know about a particular knot and/or cordage.

Quote
Meanwhile, there needs to be a great tightening of knot-tying skill and reporting detail, irrespective of test-specimen count.  (An extra dozen or two tests of fig.8 eye knots (mis)tied as done in Yachting Monthly would not be a help!)
True.  A disconcerting proportion of knot tests are performed by people who are either unskilled at tying knots, or unskilled at testing.  Either one can easily render the test results meaningless.  In the Yachting Monthly test (for example) the test was evidently performed by a reporter who didn't know how to do either.  His only qualification was the ability to write an article.

If you want knot tests you can extrapolate from, they need to be constructed and performed by people who know both how to tie knots, and how to test.

-Eric
Title: Re: Research Project using a possible new knot
Post by: agent_smith on July 03, 2018, 05:39:25 AM
From NautiKnots:
Quote
If you want knot tests you can extrapolate from, they need to be constructed and performed by people who know both how to tie knots, and how to test.

And, what to test.

Its the 'what to test' that is often the key problem.

Correctly tying knots and knowing how to set up your test machinery (including presumably statistically valid sampling) is still nothing compared to knowing 'what' to test.

And this has drifted waaaayyyyyyy off topic from the original poster's points.
Title: Re: Research Project using a possible new knot
Post by: Dan_Lehman on July 05, 2018, 11:29:30 PM
If you wanted to know the quality/composition of a gallon of milk, how many samples would you take for analysis? 
Well, that depends on what you want to know about milk.  If you only want to know about that particular gallon at that particular time, you might only need one sample.  Don't, however, expect to make useful generalizations about other gallons of milk.  What if the gallon you had tested had spoiled?  Would you conclude that all milk is spoiled?  If you tested 2% milk, would you conclude that whole milk has 2% fat content?
Though, re underscored part, the gallon might itself
be seen as a sample of the greater-batch-of-that milk
I'm pointing to *evenness* of a thing; your supposed
challenges to this miss that point --of course one wouldn't
think this 2% milk gallon implied all milk was so.
And I don't expect this climbing rope to imply things
for THAT one, or yachting ropes, or ... ; and I will
urge the "KNOT strength" is better conceived as
"this-material-so-knotted" strength.

SO, given our gift spool of rope for testing --the milk gallon--,
why test 30 specimens --THAT is my question!

Quote
Quote
I'm thinking that cordage is for the most part reasonably assumed to be pretty consistent
I think that's a faulty assumption.  Would you assume that knots tied in 12mm double-braid spun polyester would hold the same as those tied in 6mm twisted nylon?  How about 3mm single-braid Dyneema?
Whoa, then I'm poorly stated :: goodness, no,
I meant that a given spool of rope is consistent
with itself,
not that any rope is ... any other.  (See my point
re restating "knot strength" to "this-material-so-knotted strength".)

Quote
Quote
And given some experience in test results with some knots, one might come to believe that skilled tyers can replicate at least some knots well enough to not need as big a number as might be wanted for more complex knots!?

Although unskilled knot tyers might produce knots with greater variability (leading to an increase of samples needed), skilled tyers producing identically dressed knots does not reduce the needed sample size.
Why not?  Given our milk gallon, what is to gain?
(At least, I think that after some analysis of tests,
one should come to a conclusion that multiple-knots
testing doesn't show much new, unexpected.

(How interesting to see in one of Dave Richards's
tests that it was the grapevine bend that had LEAST
stnd. deviation, even over pure-rope testing!
Similarly, how puzzling to see that both he and also
CMC Rope Rescue thought to test "fig.8 re-woven
AND fig.8 on a bight", as though the knot should
care how it came to be!  NOW, yes, it would be quite
informative to see from field examination if indeed
users came up with different geometries per tying
method --I rather expect that they might,
even to the point of which end is loaded.  BUT,
do that and be explicit about it; just giving the
different names and having same tyers, one would
hope that per "dress & set" action the knots came
out the *same*; in fact, diff.s (5 cases each) were
quite close.)

Quote
Quote
But we surely aren't going to do all the multiples of sampling per all the multiples of probable factors that influence strength --a number that is huge.
True.  That's why it is so important to construct your test carefully in order to actually find out what you'd like to know about a particular knot and/or cordage.
I'm thinking of moving through the multifactored
*knot* space as an exploratory expedition, and
hoping to travel efficiently so far as test-results
fall in expected ranges,
some of which ranges will become established by
more thorough testing,
but some of that easy movement will come by
doing with less.
.:.  Throw the many-sampled cases out where
a stout pillar looks to be needed.

AND I have argued for --where possible-- the
single *test* of multiple-tokens of a knot,
stringing a line say with 5-10 identical knots
in it, to get a break, which is reasonably argued
to better indicate minimum strength, and then
have all those near-rupture (presumably) knots
to examine --maybe to further load and see ... .

At least :: like eye knots on the ends of single specimen,
and round slings with TWO of end-2-end knots (hoping
to avoid the knot-compression-imbalance that such
a structure with one-knot-only can yield (the knotted
side i.e. lengthening per knot compression and that
not being fully transferred/balanced to unknotted side
by friction at pins --maybe a pulley would do, but ... ).

--dl*
====
Title: Re: Research Project using a possible new knot
Post by: NautiKnots on July 06, 2018, 12:48:55 AM
the gallon might itself be seen as a sample of the greater-batch-of-that milk I'm pointing to *evenness* of a thing; your supposed challenges to this miss that point --of course one wouldn't think this 2% milk gallon implied all milk was so. And I don't expect this climbing rope to imply things for THAT one, or yachting ropes, or ... ; and I will urge the "KNOT strength" is better conceived as "this-material-so-knotted" strength.

SO, given our gift spool of rope for testing --the milk gallon--,
why test 30 specimens --THAT is my question!
Ok, let's back up a bit.  What exactly are you trying to learn about milk in your 1 gallon test thought experiment?  What exactly are you trying to learn about knots in your analogous spool of rope test? 

If you know that the milk is homogenous and want to determine fat content, then you need test only one sample to be confident that further tests would yield the same result.  That's analogous to testing your rope to see that it is polyester.  If one test reveals that it is polyester, and you know that all the rope on the spool is the same, you don't have to do further tests to be confident that they would also reveal polyester.

That doesn't, however, tell you anything about knots.  If you wanted to know if, let's say, how likely a particular knot tied in line from that spool is to jam, a single test won't tell you that.  Knot jamming probability does not have zero variance.  Not all tests will yield the exact same result.  All a single test tells you is that it's possible for that knot in that line to jam (or not).  It doesn't tell you (with any confidence whatsoever) what the likelihood is of the next knot jamming.

And you know that, or else you wouldn't have said:
Quote
I have argued for --where possible-- the single *test* of multiple-tokens of a knot, stringing a line say with 5-10 identical knots in it, to get a break
Here you've constructed a way of conducting 5-10 tests on separate knots with a single pull.  A compound test like that might yield more confidence in the minimum strength value, but it still doesn't tell you anything about the distribution of those values.

If you still think you can determine the mean/median/mode/min/max breaking strength of a knot in given cordage with a single test, then we're never going to agree.  If you think you need more than one test, then how many you need depends on distribution of the test results (which you probably don't know in advance), the amount of confidence you want, and margin of error you're willing to accept.

It's very tempting to skimp on the number of samples because it's inconvenient to take them.  Just realize that you're going to sacrifice confidence or error rate.  Do you want to be 95% confident in your results, or 50%?  Do you want a 15% margin of error, or a 30% margin of error?  At what point do you no longer learn what you set out to discover? 

One last time, conventional wisdom in statistics is that if you don't know the population distribution in advance, you need a minimum of 30 random samples (and quite possibly more) to determine that distribution with meaningful confidence (and even then, it's possible to be wrong).  Don't take my word for it - ask a statistician or play with the numbers yourself (there are a number of sample size calculators available online).  If you choose to take fewer samples, then be prepared for people to dismiss your results as insignificant.

I agree with the others that we have taken this conversation too far off topic already, so I'll leave it at that.

Regards,
Eric


Title: Re: Research Project using a possible new knot
Post by: Dan_Lehman on July 07, 2018, 04:25:39 PM

That doesn't, however, tell you anything about knots.  If you wanted to know if, let's say, how likely a particular knot tied in line from that spool is to jam, a single test won't tell you that.  Knot jamming probability does not have zero variance.  Not all tests will yield the exact same result.  All a single test tells you is that it's possible for that knot in that line to jam (or not).  It doesn't tell you (with any confidence whatsoever) what the likelihood is of the next knot jamming.
I think we'll find comfort that the variation just
isn't so great to worry about, "at least in some
knots", as I offered might be reasonably repeatedly
tied alike; some others of more complexity might
not behave so predictably.


Quote
And you know that, or else you wouldn't have said:
Quote
I have argued for --where possible-- the single *test* of multiple-tokens of a knot, stringing a line say with 5-10 identical knots in it, to get a break
Here you've constructed a way of conducting 5-10 tests on separate knots with a single pull.  A compound test like that might yield more confidence in the minimum strength value, but it still doesn't tell you anything about the distribution of those values.\
Though, per above..., we might come to some
comfortable & reasonable belief that the range
is not going to surprise us.


Quote
then how many you need depends on distribution of the test results (which you probably don't know in advance), the amount of confidence you want, and margin of error you're willing to accept.
Given vagaries of tying & various materials
--and this means same brand but different
histories of usage--, I think that getting the
sort of statistical level of confidence that is
defined in the pure math is ... well distant
from meaningful/useful information.

Some thorough testings esp. to focus on some
particular factors (e.g., having pretty evenly
made & scaled from smaller-to-thicker like ropes
in checking if **size** has whatever effects,
and so on) might be the basis for later taking
few tests w/some confidence if results are where
expected.

Assuming that TestPerfect did some statistically impressive
oooodles of test cases and ...,
just what confidence does that give ?
Given that someonElse did whatever tying,
that the load was applied in just some manner
(unlikely to be like actual use), and the rope
was just that rope in just that condition.


(-;
Title: Re: Research Project using a possible new knot
Post by: NautiKnots on July 08, 2018, 01:00:26 AM
I think we'll find comfort that the variation just isn't so great to worry about,
.
.
.
Though, per above..., we might come to some comfortable & reasonable belief that the range is not going to surprise us.
How do you know that, until you test it?  And, how do you know that until you perform enough tests to have confidence in the results (statistically speaking)?

Quote
Assuming that TestPerfect did some statistically impressive oooodles of test cases and ..., just what confidence does that give ?
Go to one of many sample size calculators online (such as https://www.surveysystem.com/sscalc.htm), plug in the numbers, and it will tell you exactly how confident you can be (again, statistically speaking).

Quote
Given that someonElse did whatever tying, that the load was applied in just some manner (unlikely to be like actual use), and the rope was just that rope in just that condition.
What are you trying to find out?  Haphazard testing will yield haphazard results.  If you don't construct your test meaningfully, you won't get meaningful data. 

I'm not saying that any test has to be performed X times in order to be useful -- I've done informal knot testing myself with statistically insignificant sample sizes, but that was just to get an idea of what might be interesting to investigate further.  I don't even remotely assume that those results predict the probability distribution of future outcomes.   

I am saying that if you want results that accurately reflect the general population, and are useful for predicting future results, then you're going to need sample sizes that are statistically significant.  No amount of optimistic assumption or wishful thinking is going to change the math.

Regards,
Eric
Title: Re: Research Project using a possible new knot
Post by: agent_smith on July 09, 2018, 02:13:20 AM
Tim,

You have vanished from this thread but perhaps you are still reading with interest?
At some point, this topic has drifted into testing methodologies and statistically valid sampling methods...maybe the first divergence occurred roughly at reply #17 and then escalated rapidly.

I think most of the replies from #17 onwards could be an entire new topic just discussing repeatable testing methodologies and statistically valid sampling methodology.

...

Nevertheless, my responses to your specific text is as follows:

Quote
My decision to test which knot/hitch against which knot/hitch came about from over 35 years of working with ropes at sea both professionally and leisure, and from rock climbing for leisure. I was also drawn to an online article in Yachting Monthly (May 2015) which was conducted by Marlow Ropes.
http://www.yachtingmonthly.com/sailing-skills/strongest-sailing-knot-30247

By now, you should be aware that the 'yachting monthly' test report is just another example of poorly conceived and poorly conducted testing. NautiKnots and Dan Lehman have already voiced their opinions herein - hopefully you wont make the same mistakes?

 
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My pilot tests were as follows.

Bowline v Round turn and two half hitches
- The round turn and two half hitches won outright 4 times out of 4 (as expected, based on work and climbing experience, and also Marlow Rope's online testing).

When you mention 'Bowline' - exactly which type of 'Bowline' are you referring to? There are many different forms of a 'Bowline' (note that I wrote 'a Bowline' and not 'the Bowline').
I am going to take a wild guess and 'assume' you meant the common #1010 Bowline which is based on a single right-hand nipping loop? This seams to be the default 'Bowline' that knot testers appear to be fixated on.
Its a pity that other 'Bowlines' are ignored (or in ignorance, simply not known). I would be most interested if you could test Scott's locked Bowline.
However, I would like to examine properties other than the default 'pull-it-till it breaks' mindset. A significant proportion of knot testers are fixated on the idea of probing MBS yield point of a knot (ie pull till it breaks). This mindset permeates nearly all of humanity. It would be nice to see a different approach...such as probing the following aspects:
[ ] jamming threshold
[ ] instability threshold
[ ] geometry at various load milestones (ie at certain loads, stop and photograph the knot structure - and compare to 'control' of no load)
[ ] If you are in the majority mindset of pull-to-failure type thinking, could you at least test 'Bowlines against Bowlines'. For example, test #1010 against Scotts locked Bowline and #1010 against a 'slipped' #1010 (adds 3 rope diameters inside the nipping loop).


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Looped double fisherman's (Scaffold hitch) v Round turn and two half hitches
- The round turn and two half hitches won outright 4 times out of 4 (as expected, base on work experience and based on Marlow Ropes online testing).

Please use 'ABoK' numbers where they exist to aid in positive identification. Also, realize that these knot structures act as 'nooses'. You should characterize them as such. In fact, they are 'composite' structures consisting of:
1. A tensionless hitch; and
2. A securing mechanism (ie a strangled double overhand knot versus 2 half-hitches which likely form a clove hitch).
The difference between the 2 structures being the type of securing mechanism.


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'English Braids' have very kindly provided me with 200 metres of 4mm 12 stranded polyester dinghy control line to continue my testing.
I wish you could obtain human-rated ropes (eg EN1891 abseil rope and EN892 dynamic climbing rope. Is this an impossibility?

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I have tested to failure (three times), short lengths of their control line with a splice in each end using known static weights. So I now know what load the splices part at. The next stage is to test my hitch against the splice under different environmental conditions.
Is there any reason why you couldn't terminate each end using a 'tensionless hitch' where the remaining tail is then clamped (instead of a 'splice'?

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Based on Marlow Ropes online knot test which the round turn and two half hitches is rated very highly against a splice, I have high hopes for my hitch as it outperformed the round turn and two half hitches by far.
By now, you realize that it isn't 'your' hitch.
ie it isn't 'new'.

...

Tim, I believe that there are 3 different types of testers as follows:

1. Hobbyist/Enthusiast testers:
(aka Backyard testers) who largely act in isolation:
(usually an individual who isn't well funded and doesn't have sophisticated forced generating equipment that is regularly calibrated. The individual is usually an enthusiast and may seek assistance from a friend of acquaintance). Reporting is generally not bound to scientific rigor.

2. Pseudo lab testers:
(usually individuals but sometimes 2 or more persons who are roping/rescue/rope access enthusiasts. They are not a certified test lab but do have force generating equipment and the means to capture data. They have freedom to test in any way they desire and their testing isn't accountable to third party accrediting agencies. Scientific rigor falls upon the individuals experience and knowledge (eg whether they have background education from a college/university or access to expertise in repeatable methodology).

3. Certified, nationally accredited test labs:
(who use calibrated force generating equipment and test strictly in accordance with their accredited status (these entities are normally a business enterprise - and they routinely test things to destruction. The personnel at these labs are generally not knotting enthusiasts and knot tying skills isn't part of their day-to-day employment. All reporting is bound to rules of scientific rigor and statistical sampling methodology).

Which category do you fit within Tim?
Title: Re: Research Project using a possible new knot
Post by: Dan_Lehman on July 10, 2018, 10:32:59 PM
I think we'll find comfort that the variation just isn't so great to worry about,
How do you know that, until you test it?  And, how do you know that until you perform enough tests to have confidence in the results (statistically speaking)?
WEll, seeing lack of variation in some tested
cases could lead to expecting that in others
that had nothing to make one suspect otherwise
(and then what few test cases fell into range).

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Assuming that TestPerfect did some statistically impressive oooodles of test cases and ..., just what confidence does that give ?
Go to one of many sample size calculators online (such as https://www.surveysystem.com/sscalc.htm), plug in the numbers, and it will tell you exactly how confident you can be (again, statistically speaking).
My point here is that the precision of factors
leaves all variations still in question.  Yes, a
calculator can tell about X at Y & Z repeated,
but not of X2 at Y & Z2.  So, you narrow the
testing in a sense --i.e., concentrate your test
cases-- and gain that statistical confidence,
but at the cost of breadth of applicability.

Quickly :: I don't want to seem hostile to the
use of these maths,
but one needs knowledge of much broader reaches
than will be got if concentration of test cases is all
that one does.

And we now work in absence of much of any such
tested knowledge.


--dl*
====

Title: Re: Research Project using a possible new knot
Post by: DerekSmith on August 01, 2018, 08:04:26 PM
Hi Tim,

By definition, you do not need to test this knot because no knot can be stronger than the cord it is made from, and cord MBS is measured by winding the cord around a round anchor - i.e. essentially a knotless fixing.

Provided the number of turns you use is sufficient for the cord/ anchor combination to shed all the force before the cord leaves to make the final strangle tie off, then the cord will rupture at its MBS at wherever its weakest point happens to be.

The only exception to this situation would be if you have insufficient turns and residual force exits the last turn, finishing up as a lateral  force against the SP at the Strangle attachment.  The slight angular deflection at that point will act as a weak point, the weakness being proportional to the angular displacement.

So, please ignore all the shedload of 'protocols' and statistically significant sample numbers cited above, use your Engineers eyesight and look at how cord is anchored in the MBS test rig, then make sure your knot has sufficient turns to match this and by definition it must be as strong as the cord itself.

Welcome to the wonderful world of Nodeolgists and please keep on knotting and stirring up the dust on this Forum.

Derek
Title: Re: Research Project using a possible new knot
Post by: Dan_Lehman on August 02, 2018, 01:18:01 AM
By definition, you do not need to test this knot because
 no knot can be stronger than the cord it is made from,
and cord MBS is measured by winding the cord around
a round anchor - i.e. essentially a knotless fixing.
...
What happens where testing gives contrary evidence?!
"By definition," the testing is wrong?!!

I remark this in recalling one fellow who IIRC was the
editor of an angling magazine (USA) getting just such
puzzling results --and explicitly recognizing and re-testing
them (in contrast to some reports that ignore them!)--
and, well, ... he had no explanation.  I think it was a
particular-#-of-wraps Bimini twist that didn't break,
but the line did, and did so at higher load(s) than did
the line when he tested it --yes, another goood point :
he got his own tensile and contrasted it w/the nominal
one from maker (his were way higher)! -- !!

[Oh, I think that this is the guy & site & more recent
than what I recalled, but a point to begin your own
explorations.  DOUG OLANDER
[/url]www.sportfishingmag.com/best-fishing-knots-main-line-to-terminal-gear#page-19[/url]
]

Some manufacturers (per Cordage Institute standard?)
use a tested splice strength as material tensile; some
other standard (Eruopean vs. USA-ian) allows if not
specifies some other sort of figuring.

One can beware the claims of evidence of "stronger than
the rope" from testing a round sling with one so-called
knot in it, which don't consider that knot compression
can feed slack into the knotted side and thus reduce
tension there and ... the break can occur at the pin
and not the knot.

(And then there is this elsewhere-examined Yachting
Magazine test-result image showing a break in the
>>>eye leg<<< of a knot !!   :o   Huh?!


--dl*
====
Title: Re: Research Project using a possible new knot
Post by: DerekSmith on August 02, 2018, 05:53:48 PM
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What happens where testing gives contrary evidence?!
"By definition," the testing is wrong?!!

When testing gives contrary evidence then your understanding of the limitations of the testing or the interpretation of the Statistics is likely wrong...

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yes, another goood point :
he got his own tensile and contrasted it w/the nominal
one from maker (his were way higher)! -- !!

1. was his tensile testing calibrated?
2. makers quote MBS which is typically 3 sd's below highest figure, and for added security, some manufacturers quote MBS at 2 or 3 sd's below the mean so that 99.9% of their cord will perform within the quoted MBS.