Breaking Strength and the 'Camps' of Knotters

[jcsampson]

There seem to be two camps of knotters:

Camp 1: Those who feel that a knot's breaking strength is more important than its set of properties

Camp 2: Those who feel that a knot's set of properties is more important than its breaking strength

Those in camp 1 perhaps argue that breaking strength matters most mainly because the type of cordage to be used by a knotter and a knot COULD be "an unknown"; therefore, it behooves a knotter to be prepared to get the most from ANY possible cordage by favoring only those knots that have the highest breaking strength. This perspective favors efficiency.

Those in camp 2 perhaps argue that breaking strength matters least mainly because a knotter will USUALLY be able to manipulate how stress is placed on a knot, in a variety of ways. One possible way, for example, could be by "doubling up," i.e., by simply using more of whatever cordage is available.

I confess that I am in camp 2, though I do of course respect perspectives that come from camp 1.

It is precisely a knot's set of properties that determines HOW the knot can be used and what satisfying CONSTRUCTS can be built using that knot. Sometimes, a knot may have a great breaking strength, but may have a set of properties that unfavorably limits how the knot can be used.

Not only do I like knots, but I like the constructs that can be built using knots--constructs that can then meet the demands of various applications. Each application has unique and subtle demands that need to be met: Sometimes only a knot with a less-than-high breaking strength will have the unique and subtle properties that can meet the demands. . . .

Now that my "camp 2" affiliation has been firmly established, I'd like to pose a couple of questions that concern breaking strength:

Which is stronger? A Double Butterfly Loop or a Double-Knotted, French And Dutch-Marine Bowline Combination with Flush Figure-Eight Stopper?

Yes, I'm also a proponent of Left-Handed (Dutch) Bowlines--but only when they're tight and secured using flush Figure-Eight Stoppers!

Which is stronger? A Zeppelin Bend or an Overhand Loop (which was rethreaded and is) going through a Double Overhand Loop?

Note that, for maximum strength, the standing parts in overhand loops should be dressed nearest the loop.

JCS

[Sweeney]

Do you mean breaking strength (which is the lower breaking strength of cord or rope caused by tying a knot in it) or knot security (the resistance to slippage or collapse under strain)? The former can be dealt with by using stronger cordage as man made materials are usually far stronger than actually required but the latter is arguably more important especially in more slippery modern materials.

Barry

[Dan_Lehman]

There seem to be two camps of knotters:
Camp 1: Those who feel that a knot's breaking strength is more important than its set of properties
Camp 2: Those who feel that a knot's set of properties is more important than its breaking strength
Those in ...

... both camps usually miss the point that such attributes (they are ALL
among a set of properties) don't apply so cleanly to a "knot" independent
of particular material.

because the type of cordage to be used by a knotter and a knot COULD be "an unknown";
 therefore, it behooves a knotter to be prepared to get the most from ANY possible cordage ...

Rather, therefore the knot tyer might not know how to proceed.
But, frankly, strength is a dubious attribute, typically poorly specified
and understood, not at all easily determinable and known, and seldom
all that important to cordage use.

Which is stronger? A Double Butterfly Loop or a Double-Knotted, French And Dutch-Marine Bowline Combination with Flush Figure-Eight Stopper?

Which is ... what??!  Two scoops butter-pecan w/sprinkles of pistachio in a sugar cone ...
(And a nice attribute of the Overhand stopper is that it can be tied snug to something.)

--dl*
====

[jcsampson]

"Do you mean breaking strength . . . or knot security . . . ?"

For this topic, I mean breaking strength, but knot security is an excellent issue to address in future topics. I'm glad you mentioned it.

JCS

[jcsampson]

". . . they are ALL among a set of properties . . ."

Yes! Breaking strength is just ONE of the properties of a knot's set of properties.

". . . such attributes . . . don't apply so cleanly to a 'knot' independent of particular material."

Yes! Each rope will have its own properties, too. . . .

". . . therefore the knot tyer might not know how to proceed."

Yes! "Each application has unique and subtle demands. . . ."

". . . strength is a dubious attribute, typically poorly specified and understood, not at all easily determinable and known, and seldom all that important to cordage use."

Yes! I especially like the part that says, ". . . not at all easily determinable and known . . ."

"Two scoops butter-pecan w/sprinkles of pistachio in a sugar cone . . ."

I don't know how to make that one. Is it in the ABOK?

". . . a nice attribute of the Overhand stopper is that it can be tied snug to something."

Yes! That is a very important property. Unfavorably, however, an Overhand Stopper can "walk" down the line; but, if an application demands that the stopper not walk, then that problem can be solved by using, say, two adjacent Overhand Knots--which can still be tied snug, unlike the Figure-Eight Stopper.

JCS

[jcsampson]

You can easily transform the breaking strength of ANY knot into 85%. Here's how:

(1) Make a long-enough Overhand Loop--which has a breaking strength of about 85%--at the end of your line.

(2) Make whatever knot you want "on the loop."

Example:

If your rope has a safe working load of 200 pounds (90.7184 kilograms), and you make a knot ON THE LOOP that has a breaking strength of 60%, then you will wind up with a safe working load of 200*2*0.60 = 240 pounds (108.8621 kilograms) ON THE LOOP.

The safe working load of the rope's standing part BEYOND THE LOOP will be 200*0.85 = 170 pounds (77.1107 kilograms), courtesy of the Overhand Loop's knot.

This contrasts to the safe working load of 200*0.60 = 120 pounds (54.4310 kilograms) that you would have if you didn't use the Overhand Loop at the end of your line.

In this example, the technique gives you an extra 50 pounds (22.6796 kilograms) of safe working load, which is significant--and you can use any knot that has a breaking strength of AS LOW AS 42.5%, on the loop, and still get a safe working load, on the line, of 170 pounds (77.1107 kilograms).

In this example, if you tie a Left-Handed Bowline on the Overhand Loop, you will wind up with (1) a breaking strength on the line of 85%, (2) no security issues, because you can wrap the loop at the Bowline's working end AROUND the Bowline, (3) a Double-Loop Left-Handed Bowline that is suitable for safety-critical situations, which is nice because you'll have no working end sticking into the middle of the Bowline's loop, and (4) no potential variations in the sizes of the Bowline's two loops, which is the main criticism of the French Bowline.

Several problems all solved at once--thanks just to the use of a simple Overhand Knot.

Note that, for maximum strength, the standing part in the Overhand Loop should be dressed nearest the loop.

JCS

[roo]

You can easily transform the breaking strength of ANY knot into 85%. Here's how:

(1) Make a long-enough Overhand Loop--which has a breaking strength of about 85%--at the end of your line.

Stop. Just stop.  Where are you getting 85%?  One source lists, in their limited tests, a range of 58-68%:

http://www.c2safety.com/Download-document/45-Test-av-olika-knopars-styrka.htm

I'm not going to try to decipher the rest of your post.   There's no need for YELLING, by the way.

[jcsampson]

"One source lists, in their limited tests, a range of 58-68% . . ."

That's what I like: spirited replies that urge the uncovering of the truth.

I once found a respectable site that showed the Overhand Loop (not to be confused with the Overhand Knot) to have the highest breaking strength, which was "85%," in contrast to other generally strong loops, which were "80%" or lower, so the Overhand Loop was chosen for my post. Certainly, the site could have been wrong. The site is current, but this particular information is no longer accessible via that site; perhaps the information was removed for its being incorrect. If the information is incorrect, then I would rather not reveal the site, because it is a very respectable site upon which I would not want to bring any discredit.

However, debating the accuracies of sources is not the point of my post; the point is that--if you can find yourself a very strong single loop, say, one with a breaking strength of 85%--you can manipulate the breaking strengths of other knots to a satisfactory degree.

That brings us to the Figure-Eight Loop . . . at 80%, which is still useful. Any complaints?

Or, you could try the Adjustable Grip Hitch.

By the way, I'm NOT shouting; I'm EMPHASIZING. It's quicker and easier than using italics.

JCS

[Dan_Lehman]

You can easily transform the breaking strength of ANY knot into 85%. Here's how:

This is both sneaky and begs the question Why ... ?! .

It's "sneaky" to claim to have changed the strength of some knot
when in fact you're actually using a different knot -- the definition
including the loading of parts (and having two not one SPart is
a significant change).

But why would one do this, rather than use the Overhand eyeknot
giving the strength to begin with?  (It's like explaining creation with
God, and begging off on explaining God.  Or getting "any bicycle"
to go NNmph by affixing it to the front of a motor vehicle; so why
not just use that vehicle?)
There is one answer, of sorts:  there are some anglers connections
that begin with a strong eye knot --typically a Bimini Twist-- and
then join the eyes for getting strength in the line-2-line joint
(surprisingly I just read that an extended "Cat's Paw" structure
resulted in something under the 100% often cited for the Bimini
Twist (which itself leads to some mysteries, including grossly
under-rated fish lines and more interestingly some peculiar results
in excess of 100% (!) of tested line strength)).

As for this 85%, I can find it in the CMC Rope Rescue Manual,
claimed for a particular type of rope -- low-elongation nylon
kernmantle.  I tried once to get Jim Frank to dig up his notes
about that testing, as it just could be some typo for '58'
(transpose some of the absolute force and see what you get!),
but he didn't do that and I didn't pursue it (you could say we
both drifted off the topic).  AMGA have asserted equal strength
between Fig.8 & Overhand eyeknots.  But here one can wonder
at materials and actual geometry -- the name doesn't give
a definite specification.

But, why, why, keep your source a secret?  That is SMACK against
the scientific quest for truth!

Note that, for maximum strength, the standing part in the Overhand Loop should be dressed nearest the loop.

I note "nearest" => "nearer".  As for this assertion --which I've made
myself, with varrying degrees of assurance-- , it too begs the question
for justification.  (And it might be that some "improper" dressing gets
the highest strength.)

--dl*
====

[Erickson]

Sorry js,

Not only do I have a hard time accepting your value for the OH loop but I have a really hard time accepting your math/engineering. Doubling a line of a given strength is going to give you a significantly diferent knot (as Dan said) than using a single line of twice the initial strength. Assuming you can simply apply a factor of 2 to your strength equation is overly simplistic. The dynamics of your new two-line knot would be difficult to extrapolate from a single-line version of the same knot.

Differences:
1. The shape of the cord will be somewhat elliptical even at the compressed nip for the doubled line.
2. The OH Loop does not create a single cord the way twisted or braided line does (differential tension.)

Damn, I'm having fun with this one. I'm making it all up, but I'm having fun

K-

[jcsampson]

"You can easily transform the breaking strength of ANY knot into 85%."

". . . begs the question Why . . . ?"

(Notice how my selecting, copying, and pasting failed to copy your italicized "Why" correctly. THAT'S why I prefer to emphasize words using the Caps Lock key instead of using italics: Uppercase letters will always copy correctly.)

"It's 'sneaky' to claim to have changed the strength of some knot . . ."

". . . why would one do this . . . ?"

Perhaps I should have used a different wording:

"You can easily enjoy the benefits of one knot while simultaneously enjoying the benefits of the high breaking strength of another."

If you've got more than one knot making up a line, the line will suffer the breaking strength of the weakest knot. Right? Certainly--regardless of the ACTUAL breaking strength of the knot on the loop--that knot ON the loop couldn't possibly be WEAKER than the knot between the standing part and the loop (i.e., at the base of the loop), now, could it? Yes, the shape of the fibers has changed, but to suggest that something is VERY different is to suggest that we should immediately summon research to determine whether using hollow braid (because it tends to flatten) is very different from using solid braid.

". . . it too begs the question for justification. (And it might be that some 'improper' dressing gets the highest strength.)"

I admit that this assertion of mine is based entirely on my ideas about what it is that is responsible for the tendency of a rope to break often just above a knot--which have resulted from my observations and recognition of patterns over the years, and some deductions about how some items are able to break in general. It has something to do with the technique of tearing a phone book into two. While I'm not in a position to prove anything scientifically, I certainly am in the position to put ideas into the heads of others, who may very well be in the position, so that they can finally figure it all out for us, so that I will have made a valuable contribution, and so that we can all know once and for all what the truth is. For this, I shall not apologize.

I applaud those who attempt to inject science into knotting, but one of the wonderful things about knotting is how unscientific it can be. Knotting is a wonderful world in which intuition and gut instinct have their place. Intelligence comprises more than just science--whether the proponents of science would ever care to agree.

"That is SMACK against the scientific quest for truth!"

Nah, . . . it's just being polite.

JCS

[jcsampson]

". . . overly simplistic . . ."

OK. Great replies.

Yes, I'm probably guilty of oversimplifying (or gross oversimplification, if you prefer), but the great replies that have been spawned by this possible guilt of mine are doing their jobs: They are making us all think more about what it is that we'd like to know more about, which is the whole point of our having joined the forum (or at least of my having joined it).

While it is likely that my arithmetic manipulation is . . . inadequate to describe the complexities of what really goes on with rope and knots, my statement that "you can manipulate the breaking strengths of other knots to a satisfactory degree" holds some truth.

"The OH Loop does not create a single cord the way twisted or braided line does . . ."

I agree, but see my reply to Dan.

JCS

[Dan_Lehman]

". . . begs the question Why . . . ?"

(Notice how my selecting, copying, and pasting failed to copy your italicized "Why" correctly.

Yes, indeed, and I'm deeply hurt by this, my meaning grossly misconstrued!

THAT'S why I prefer to emphasize words using the Caps Lock key instead...

That's why I restored the italics, and donated some extra to you.

Perhaps I should have used a different wording:

"You can easily enjoy the benefits of one knot while simultaneously enjoying the benefits of the high breaking strength of another."

Or you could use stronger rope and not have another knot
and doubled rope knotted.  Your example didn't convince
me (others?) of any advantage; my example might have.

that knot ON the loop couldn't possibly be WEAKER than the knot between the standing part and the loop (i.e., at the base of the loop), now, could it?

In the example I cited, the author seemed to imply some slight weakening from
even the multiply reeved Cat's Paw -- and certainly (as he claimed the number
of such reevings made a difference) of less involved CPs!  I recall this being the
case for some more mundane stuff than angling line:  that in testing reeved
bowlines (for joining hawsers (stuff one can actually grip!)), simple reeving
was weaker than Reef-knot-like reeving -- and that implies that the break of
the weaker came at the joint and not the bowline.  (I would favor Granny
knot reeving, to have a joint that could be untied easily.)

And where your eye knot instead an eye splice and the material HMPE,
then you knot-on-the-loop would be weaker.

I admit that this assertion {about which end to load of an Overhand eyeknot} of mine is based entirely on my ideas about what it is that is responsible for the tendency of a rope to break often just above a knot--which have resulted from my observations and recognition of patterns over the years, and some deductions about how some items are able to break in general. It has something to do with the technique of tearing a phone book into two. While I'm not in a position to prove anything scientifically, I certainly am in the position to put ideas into the heads of others, ...

But what you put was an unqualified assertion; if you want to generate
ideas & thinking you should give your rationale, tell us how phone-book
breaking comes to play in the distinction you're making.

As for observations, I've done some observing, too, and find breaks
to occur inside of the knot, usually at/near the entry point on the
initial bend & compression.  And sometimes there is a break well
outside, but this can be seen as coming in line that was tortured
en route to being outside (it started well inside).

"That is SMACK against the scientific quest for truth!"

Nah, . . . it's just being polite.

No, it's just not sharing this great site you found but referring
to it for ... kicks?  I put the meat on my find of "85%"; I don't
see at all helpful to play coy on yours (and whatever else might
be at that site).

--dl*
====

ps:  "overly simplistic" ::    No, simply "simplistic" is the pejorative,
wanting no enhancer.  (In common parlance, e.g, "very" is much overused,
essentially sapping the clout from the words modified, which should be
left to stand on their own.)

[jcsampson]

Oooh, nesting.

". . . begs the question Why . . . ?"

No, I mean when copying large amounts of text in general, say, to text files.

Yes, but then I'd have to spend more time inserting all those little tags, instead of doing other nice things. It adds up, you know.

"Or you could use stronger rope and not have another knot and doubled rope knotted. Your example didn't convince me (others?) of any advantage . . ."

This tells me that my purpose in presenting what I have presented is being misunderstood, but it's being misunderstood only because I haven't yet had the chance to say the following, since my replies need to wait for yours to find out what you're thinking, so that I can know what needs to be said next, and which I'll finally say, now, at this time:

Of course we can just use stronger rope. That's what I would do. By what I have presented, I simply meant and mean to point out how wonderfully flexible this activity of knotting is and how many OPTIONS we have. This is consistent with my "camp 2" idea that breaking strength is less important than a knot's set of properties. What was presented is designed to show one of the reasons why. Whether you like it, your statement helps to reinforce what appears to be our "camp 2 affiliation."

I wasn't trying to claim or show an "advantage" over the better option of using stronger rope. There certainly is no advantage to making knots on loops when we can just use stronger rope. If stronger rope were unavailable, well, then we could be creative by using some option such as the one presented. Keep in mind also that there are those with less experience than you who may find themselves reading this and be inspired by some perspective that I have presented. Every perspective is useful in nurturing intelligence. If I already know something, I'll still tend to read all about it, because I know that a new perspective might open up a whole new set of beneficial ideas for me.

Understand that I intend to present useful perspectives in the hope that someone, somewhere will spot them and recognize them as useful and be able to benefit from their usefulness. I'm alive, so I might as well. Do understand that you need not be the one to recognize them as useful.

". . . breaks to occur . . . usually at/near the entry point on the initial bend & compression."

Yes, "the initial bend & compression" matches my observations exactly. So, what else can we do but to attempt to manipulate how, and minimize the ways by which, a knot will treat the initial bend & compression when we dress and set it. What else? I'll tell you what else! We can just use stronger rope and forget all about this nonsense of breaking strength!

". . . 'simplistic' is the pejorative [not 'overly simplistic'] . . ."

You are correct--though not overly so.

JCS

[Dan_Lehman]

Oooh, nesting.
...
Yes, but then I'd have to spend more time inserting all those little tags, instead of doing other nice things. It adds up, you know.

For nesting, Rockclimbing.com has the worst abusers (gratuitous full-text
copying in reply, too -- something seen in rec.climbing with some boasting
of automating a reply process),
and DPReview.com the prettiest -- diff.colored bars ('|') well beyond a
mere rainbow assortment.
As for "inserting ...", you should be able to click-select/highlight and
then select the appropriate button for the effect.  It used to be the
case that when I (my system, whatever) did this, the format effectors
would be put unhelpfully at the end(?) of the highlighted text,
and, so, I got used to the right pinky seeking out brackets; but now
it works for me.
In any case, the more time we slow you up doing that, the less advance
into further trouble you might get, eh?!
 

Your example didn't convince me (others?) of any advantage . . .

I simply didn't see how using some presumed strong but otherwise
undesirable knot in order to strengthen the desired one got you
anywhere free of the undesirable characteristics of the strong knot.
In your Overhand eyeknot to strengthen a bowline,
you still have a perhaps jammed Oh EK to deal with,
so how is it of benefit to stick a bowline (for ease of untying?)
onto the end of that?

Now, in the case of using a Bimini Twist's presumed 100% strength
in order to join (maybe dissimilar) lines where there is no single-strand
joint of that strength, it makes sense (if one can suffer the greater
extent of this joint -- the two EKs and their knotted eyes).

Understand that I intend to present useful perspectives in the hope that someone, somewhere will spot them and recognize them as useful and be able to benefit from their usefulness. I'm alive, so I might as well. Do understand that you need not be the one to recognize them as useful.

Oh, dear, I'd lose sleep thinking that some gem of Usefulness escaped
my mining!  Do understand that by the haggling of different perspectives
of engaged Other Minds considering some proposal, what survives
ought to be Pretty Good Stuff(tm).  The usefulness should be able to
be justified; Occam's Razor trimming of things can do away with some
proposals, but some should survive on the basis of not worshipping
maximum efficiency as the Ultimate End.  --different strokes for different
folks (better: different circumstances (perhaps materials, perhaps tying
conditions)); "more than one way to skin a cat".

"

. . . breaks to occur . . . usually at/near the entry point on the initial bend & compression."

Yes, "the initial bend & compression" matches my observations exactly. So, what else can we do but to attempt to manipulate how, and minimize the ways by which, a knot will treat the initial bend & compression when we dress and set it. What else?

One needs to be guided by some evidence of the mechanics at work,
and maybe the situation expected.  Of the latter, I'm recalling the words
of Life on a Line (e-book available...) author Dave Merchant that he
found greater weakening of esp. Fig.9 eyeknots vs. Overhand ones
in dynamic loading -- the latter was fairly consistent with slow-pull,
the Fig.9 (and I think to a lesser degree the Fig.8 (of some loading!)
was more weakened by presumed rope movement & frictional heat.

One can see in some knots where the initial "deflection" (my term)
is mild that there will be much movement as the SPart can flow
around such things before reaching some farther-along u-turn.
So, having thought that such a design bettered the knot vis-a-vis
the "hard bend" worry, one finds oneself facing the "rope-movement"
problem!  -- which maybe can be sorted out by the expected use
(dynamically arresting a fall, or more steadily supporting something)?!

One can load knots in braided rope and see:
 - torsion in the rope, one direction of strands being pulled taut,
   the opposite direction's strands arched in non-tension (!)

 - *snowplowing* of material on the inside (i.e., away from pull
   side; the more-interior-of-knot side) of some point of bending
  ("deflection"), such as the collar of Ashley's bend.
   (I loaded a Bowline variant heavily in the PP kernmantle rope
   just described in "Knots in the Wild" post and saw neither condition,
   or little of either.  But I don't know what a test device will prove of
   this.  And I have often seen the first condition in the Fig.8 eye
   knots, but they test well.)

--dl*
====