Author Topic: Bend: Square Knot with Secured Working Ends  (Read 16442 times)

DDK

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Re: Bend: Square Knot with Secured Working Ends
« Reply #15 on: November 08, 2010, 03:12:37 PM »
... Knot4U said that it was a Square knot and made no mention of 'Reef' ...

... Many webpages on the Internet quote Ashley who said, "There have probably been more lives lost as a result of using a square knot as a bend (to tie two ropes together) than from the failure of any other half dozen knots combined."  That's where I believe the bad reputation of this bend originates. ...

I believe this reference in the starting comment of the thread is what led me to believe that knot4u was specifically discussing the Reef Knot and not the Thief Knot.  My recollection is that Ashley's comment was specifically targeting the Reef Knot.  Unfortunately, I do not have a copy of ABOK handy at the moment.

DDK

DerekSmith

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Re: Bend: Square Knot with Secured Working Ends
« Reply #16 on: November 08, 2010, 03:49:42 PM »
I think that we both jumped to the same conclusion - indeed, the quote from ABoK #75 is as follows --

Quote
    75. But employed as a bend (to tie two rope ends together), the
REEF KNOT is probably responsible for more deaths and injuries than
have been caused by the failure of all other knots combined.

Derek

DDK

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Re: Bend: Square Knot with Secured Working Ends
« Reply #17 on: November 08, 2010, 03:55:49 PM »
"  Anyway, it may be advantageous for the middle structure to act like a Thief Knot if it could.  That way, I think the tension would tend to be naturally balanced on each leg of each loop.  What I'm saying is that it may be good for the middle structure NOT to hold super securely.  "

Yes, I was wondering the same thing about the natural balancing of each leg of the loop and that it might actually be a good thing.  This does make one wonder about the Square/Reef Knot configuration.

" The securing knots are where most of the security is and should be. "

Yes, I think this is possible and part of the reason I tend to view this construction as a modified Zeppelin Loop Bend.  Of course, having a handle on where the security is coming from is much more interesting than what we call it.

" the tension in the loop is already half of the total load. "
" The tension at the point of contact with the other loop is the full load, but the tension on each leg of loop would be half the load.  In other words, half plus half equals full tension at point of contact (and full tension at each Zeppelin Knot). "

I think I agree with you but might say it somewhat differently.  The perpendicular compression on the rope at the point of contact is the full load while the tangential tension in the rope is half the load.  For example, the tangential tension in a rope (cross-sectional average) as it wraps around a pulley (frictionless) is the same as the rope on either side of the pulley.

" As an aside, one could replace the Thief Knot middle structure with a Figure Eight Bend and maintain the central inversion symmetry. "
" That's a different concept. .. "

Oops, I probably should have not digressed with that statement. I was not suggesting it as an alternative but was merely talking about knotting structure.  In my defense, I did say "As an aside ..."

DDK
« Last Edit: November 08, 2010, 04:00:28 PM by DDK »

DerekSmith

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Re: Bend: Square Knot with Secured Working Ends
« Reply #18 on: November 08, 2010, 04:15:24 PM »

I did not mean my "why bother" in a disrespectful way, by the way.

Don't worry - the words Rhino - hide - thick - spring to mind.

As for "would I abseil from a burning building with this configuration?> probably not   :'(  "  --  If I had lengths of 6mm poly rope and 3mm polyester cord which together reached the ground, and it was a case of use them - - or play an up front and personal game of 'Pot-Kettle(Derek)-Black', then I would go for it - but I would use an OH on the bight loop knot on the poly rope (or several to give me some extra 'bounce' if I could afford the length) - and I would fix the 3mm polyester braid to the loop using a Beckettesque multi wrap 'sheet bend' style bend, and tether the end to the SP with a double strangle.  The reason for that choice is that the long lazy wraps around the thick rope would be the gentlest way of transferring the load from the 3mm cord into the rope and yielding the greatest strength for the bend.

However, having fashioned my safety rope, I still haven't fathomed out how I might descend it without cutting / burning through whatever I am to hold onto it with...

Apologies to Knot4U for the diversion...

Derek

Dan_Lehman

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Re: Bend: Square Knot with Secured Working Ends
« Reply #19 on: November 08, 2010, 08:43:20 PM »
 - remarks on various points -

1) Yes, astute forensic surmise by DDK re "Thief", but not necessary
(as it assumes that one cannot use both ends of at least one line --note, e.g.,
that the anglers' "Surgeon's knot" of joining a (short) leader to line requires this).
Morever, esp. as Knot4U envisions a main use --i.e., dissimilar-sized lines-- , one is
more naturally going to tie one line to an already tied eye-knot in the other,
and so in that way bypass this question (and see #3, e.g.).

2) Thief/Reef is beside the point in the final structure : it is neither, being loaded
on all ends.

3) I think you'll find this jamming in many materials (of roughly equal diameter).
(I have found one connection of com.fish. longlines with a SquaREef knot with
ends tucked back through the lay --very slender profile, hardly bulking beyond
the twin-line size (helped it seemed by some compression of perhaps a pot hauler
on the knot!)

4) Yes, rockclimbers have used a structure somtimes called "the Square Fisherman's"
in which the SquaREef's ends are tied off in Strangle knots --hardly making a Grapevine,
but such distinctions are lost on climbers, alas.  This structure is needlessly bulky and
sub-optimal for the purpose, IMO --better to use a Thief so that (a) it is easier to untie
and (b) the Strangles --set snug to the center knot-- are pulled tighter into the center
knot and thus better secured themselves by loading (though now, admittedly, they
are critical to security rather than supplemental).

5) To Knot4U's desire to enable balanced loading w/less tightness in the center knot,
I urge used not of the SquaREef but the GRANNY --looks to make a great eye-joining
structure, with gentler curves and surer ease of untying ; now, chafe on taking up load?

6) I recall some old testing showing that the eye-2-eye bend using the SquaREef was
stronger a bit over just simply reeved eyes of two bowlines (which is interesting if so,
as the rope in eye-2-eye is bearing half the tension of the eye-knots' SParts).  --this
testing was done in rather heavy (1.5" diameter?) rope, IIRC.

7) For greatly dissimilar diameters, just reeve one line through the other's eye --the
thinner will turn adequately gently around the thick, and nothing's to be gained
by knotting them.

8.) There is no "cow hitch" present --so let's stop calling anything here that.

9) I found one 3/8" black PP longline with Overhand mid-line eyes in which
roughly 1/4" braided nylon snoods has been tied using what I'll call a "Square
Hitch"
--i.e., the structure here but with one end (of the four) unloaded (it was
in all or most cases (a) long and (b) knotted w/an Overhand stopper --which begs
the question If it's thought a stopper might be needed to arrest slippage, why
put it soooo removed from the eye against which it will abut ?
!)

10)  Frankly, as sizes get greatly dissimilar, I'd move to hitching the thinner to
the thicker by means of a Clove/Cow/Rev.Groundline hitch with the tail run up
to a stoppered Rolling Hitch ; maybe even a Fixed Gripper hitch would volunteer!
... or ...

11) The general "rope problem" of joining a thin to a much thicker line can be
called that of making a "Messenger-line bend (hitch)".  One likely wouldn't
go to the bulky bother of making even a Bowline (let alone Z.eyeknot) in the hawser,
but would just form a bight to be "bight-hitched" to with the messenger line.  Or, one
would be tying to a spliced eye (maybe most likely?).  (In some cases, there is a series
of increasingly larger lines in the transmission of the towing cable to the other ship;
HMPE cordage might have reduced this, though.)  Harry Asher got an idea he named
the "Seizing Bend" (in that the hitching did mimic seizing), which can be improved
upon; there are many briefer structures that look good, too, IMO.

--dl*
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knot4u

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Re: Bend: Square Knot with Secured Working Ends
« Reply #20 on: November 08, 2010, 09:05:48 PM »
Below are the "same" knots as in the original post.  I put "same" in quotation marks because the difference in dressings may make different knots.  I prefer the dressing in the first pic below.  When loaded, the strains on the ropes seem to be gentler.  By the way, the first pic does NOT become the cow hitch in the second pic when the ropes are loaded.  Rather, when applying a load in the first pic, the bootlace squeezes the red rope together and there is no further capsizing.





Again, in my testing, it's plainly obvious that the beloved Zeppelin, Carrick, etc., would not work well in this situation.  I'm NOT saying the original post is the best solution, but traditional bends certainly are NOT.  Perhaps a gripping hitch, like the Rolling Hitch for rope, may be better for bending a thin rope with a much thicker rope.  That's another thread...
« Last Edit: November 09, 2010, 12:41:44 AM by knot4u »

SS369

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Re: Bend: Square Knot with Secured Working Ends
« Reply #21 on: November 09, 2010, 12:33:39 AM »
Looking at the pictures, and thank you knot4u, it looks way overly complicated and not so pretty considering that this contraption might have to slide through a sheave or a abseiling device. (Might have to launch out of a fiery condition with ropes at hand.)

If it is two so very dissimilar lines to be joined then I would think that the working end should/could be left untied as in the Albright knot or Seizing bend as Dan pointed to. If there were the added need for a bit of "fail-safe" then just add a stopper to the working end of the Seizing bend's smaller line.
These will do a good job of connecting the lines, but the disassembling may be difficult after loading.

It draws my attention to the security knot of the smaller line and the idea that this is where failure is most like to occur comes to the front of the class.

knot4u

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Re: Bend: Square Knot with Secured Working Ends
« Reply #22 on: November 09, 2010, 12:55:17 AM »
Yes, this contraption is an ugly monster.  However, I think the pics are also making this contraption look huge and overly complicated.  If you were to see these knots in context in real life, the knots are relatively small compared to the rest of the ropes.  There are probably better solutions for joining a thin rope to a much thicker rope.  (I can think of a few better solutions.)  At the same time, it's good to know that eyes here have looked at this knot and nobody has flat out said the bend will fail, will put too much strain on the ropes, or whatever.

Also, like I said above, this contraption may have a few advantages that I mentioned earlier, one being that the average guy can tie it if he knows a Square Knot and a Bowline.  He probably won't know the Seizing Bend, the Albright Knot, the Rolling Hitch or whatever.  I have roughly 120 knots in my knot vocabulary, and the Seizing Bend is not in there.
« Last Edit: November 09, 2010, 01:38:31 AM by knot4u »

Mike

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Re: Bend: Square Knot with Secured Working Ends
« Reply #23 on: November 09, 2010, 03:31:17 AM »
What about the "Simple Simon" or " Dbl Simple Simon" ?   I have haad good success using them to join ropes of dissimilar sizes.

knot4u

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Re: Bend: Square Knot with Secured Working Ends
« Reply #24 on: November 09, 2010, 04:25:41 AM »
What about the "Simple Simon" or " Dbl Simple Simon" ?   I have haad good success using them to join ropes of dissimilar sizes.

Interesting, from the looks of the Simple Simon, I'd want to secure at least the big rope in a similar manner as in the pics above.  Note that the Simple Simon is more complex than the Square Knot.
« Last Edit: November 09, 2010, 05:14:38 AM by knot4u »

knot4u

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Re: Bend: Square Knot with Secured Working Ends
« Reply #25 on: November 09, 2010, 05:18:53 AM »
   With such huge differences in rope sizes, your solution does not make sense! You use the same type of knots to secure the working ends for both ropes, while the weaker link, the knot on the rope of the smaller diameter, would slip at a fraction of tensile forces than the stronger, the knot on the rope of the greater diameter. So, why bother to use the same type of knot on the later? A much inferior bend would be enough! The solution is greatly unbalanced. You should differentiate the knots you use on the two ropes, even if this will make the thing uglier than it is now ( not an easy task, I am afraid... :))  

What exactly will slip?  According to my testing, the small rope is much more likely to break before anything slips.  Maybe you can provide pics of what you mean and results of your testings.  Otherwise, I don't know that you're talking about.
« Last Edit: November 09, 2010, 05:26:39 AM by knot4u »

knot4u

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Re: Bend: Square Knot with Secured Working Ends
« Reply #26 on: November 09, 2010, 09:25:35 AM »
...the small rope is much more likely to break before anything slips.

  Let us suppose that the small rope will break at tensile force X , and its bend will slip at 10X. Then the bend of the large rope will slip at 1000X, or even higher, I reckon ! Why on earth you bother to use, on the large rope, such a secure bend ? You tie the working ends of the knot on the large rope, so they do not slip, with a secure bend that is hugely redundant there. An overkill, in short, and not a beautiful one. I mean, it is not justified even by its decorative value...

Hey look buddy, the contraption is an ugly, clumsy, generic solution that solves a wide range of problems.  It's for the meat heads who don't want to think but still want a catch-all bend for every possible bend problem in the universe as we know it.  When thought of like that, suddenly the contraption doesn't seem too monstrous... just kidding, sorta.  :P

Anyway, I still don't know what you're talking about.  What is the bend on the large loop you keep mentioning?  Are you talking about the Zeppelin Loop in the big rope?  I'm having a mental block here.  How do you propose that contraption should be changed but still remain applicable to bending vastly different ropes?
« Last Edit: November 09, 2010, 07:37:13 PM by knot4u »

knot4u

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Re: Bend: Square Knot with Secured Working Ends
« Reply #27 on: November 09, 2010, 07:43:00 PM »
Xarax, are you not understanding I duplicated the contraption from the original post?  The contraption in the original post needs secure Zeppelin Loops (or Bowlines) on each side because the ropes are similarly sized.  The other pics I posted later are simply a duplicate of that contraption but with different ropes, and I did that mostly for instructional purposes.  I said what I was doing in my post above.  Plus, the concept here is a non-thinking catchall bend for somebody who knows the Square and an end loop.  It was possible for me to display the hundred different variations of this contraption, but I'm not quite as motivated with the camera as you.

You keep mentioning the Zeppelin Bend as if it's so important here.  IT'S NOT.  I mentioned probably more than five times above that someone can tie a similar contraption if they know the Square and the Bowline.  Heck, they can probably even tie two hatches on each side.  What's obvious to me is that you're so deep in the knot world that you forgot, or never knew, what it's like not knowing how to tie the most basic knots.  For that average guy, this contraption gives that person a pretty good bend for a wide variety of situations.  Note that's one of my advantages that I listed.

I read your ideas about unbalance.  I disagree because what you said is inconsistent with my own testing.  Maybe you didn't dress the contraption correctly, or it's more likely that you didn't even test this contraption at all.  Would you consider a Cow Hitch on a loop attached to an object to be unbalanced?  I don't.  That's one of my most favorite hitches for it's strength and security.  What are the differences here?  The main difference is that each rope is "hitched" to a loop of another rope instead of to an object.  Even if one leg of a loop were unbalanced (it's not), the load at that leg would be no more than the load at the standing end.  So, it's a moot point.

Regarding jamming, I probably despise jamming knots more than anyone on this site.  For anything other than fishing knots, I generally hate knots that I fear will jam on me.  By the way, jamming won't happen here if you dress one loop like I did in the later pics above.  Also, in my experience, I have been able to get Square Knots unjammed by pulling diagonal ends.  However, I can see jamming being a problem in huge ropes with lots of stored energy.  

I understand you think it sucks.  So, I skimmed your posts for an improvement to this concept.  I didn't find one. Maybe you can bold your improvements for me if you have one.  I know you posted pics earlier, but those knots don't have some of the advantages that I listed above.  I have to say that if you keep posting the same thing over and over again, then I probably won't read it.  Strangely, I appreciate Dan's criticisms, but your criticisms are so far off in my opinion that it's like you're talking about another contraption.

« Last Edit: November 09, 2010, 09:41:20 PM by knot4u »

Dan_Lehman

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Re: Bend: Square Knot with Secured Working Ends
« Reply #28 on: November 10, 2010, 12:20:51 AM »
  It is a pity you do not have a picture of it...You should buy a very small digital camera - there are some in the size of a credit card- to capture moments like this. 
???

XaraX, where do you think those photos of Knots in the Wild come from?
And "very small" is very hard to use in not-very-small hands, at least;
I have a "compact", more of their larger end, and a dSLR of their smaller end.
--now, not then (but, then, I don't now know whether that bit of rope
might be yet within reach).  But, really, it's an easy structure to replicate
yourself : laid rope, even just a single piece long enough ... .

Quote
Also, in my experience, I have been able to get Square Knots unjammed by pulling diagonal ends.

Knot4U, I suspected the Square eye-2-eye joint as vulnerable to jamming,
and will continue to do so, but testing this loosening method against
the structure joining some of that "Home Depot" rope, indeed I found
that diagonal pulling readily moved it and loosening was simple.
(Maybe I applied some couple hundred pounds force, via pulley.)
I know I've tried the convert-into-straight-line-&-CowHitch capsizing
with tight SquaREefs and found them unwilling to budge!  (For reefing
sails, one simply doesn't get things so tight.)  In a case of expected
large loads, I'd still favor the Granny knot vice the Square, and
would love to see test results for it.

--dl*
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Rrok007

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Re: Bend: Square Knot with Secured Working Ends
« Reply #29 on: November 10, 2010, 07:10:07 PM »
See... I've always thought of the square knot as a double overhand knot with a Hollywood plot hole.

 

anything