Author Topic: A noose-like hitch that can be untied after hard strain  (Read 35518 times)

roo

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A noose-like hitch that can be untied after hard strain
« on: February 10, 2012, 05:56:12 PM »
I was searching for a non-slipped noose-like hitch (only one pass around the object) that collapses and squeezes the object, but can be untied after heavy load while having good to excellent security.  So, I've been testing this simple hitch shown in the link, which starts out with a half hitch, and the chases the standing part back through the half hitch.

I'm still evaluating it (and its variations), but I'd thought I'd show it  to get comments. 

Update:  http://notableknotindex.webs.com/gnathitch.html
« Last Edit: March 27, 2012, 05:25:09 PM by roo »
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knot4u

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Re: A noose-like hitch that can be untied after hard strain
« Reply #1 on: February 10, 2012, 07:30:23 PM »
It's a Marlinspike Hitch in which the standing end operates as the spike. That's nifty.
« Last Edit: February 10, 2012, 07:33:50 PM by knot4u »

xarax

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Re: A noose-like hitch that can be untied after hard strain
« Reply #2 on: February 10, 2012, 07:43:42 PM »
   The hitch presented does not have an "excellent" security (of course !), but I am afraid that it does not has even a "good" security ... :) However, when pressed upon the surface of the object, we may say that it is not bad...
   The most simple noose-hitch with a "good" security indeed I know is the  Constrictor-around-the-standing-part noose-hitch, that I have also called the "Buntline extinguisher" (1) :) . It requires no more tying steps and tucks than the well-known Buntline hitch, but it is much better.
    However, when I was investigating  how a hitch based on the Pretzel 1 mi line bend (2) would capsize if/when the tail would be untucked once, I have met a most simple hitch, based upon a simple overhand knot ( shown at the attached picture.) I saw that this hitch had a satisfactory security, given its most simple form...As it reminds the hitch presented in this thread, I thought it would be interesting to compare them here...
   (If we allow the line to make two  turns around the object, the hitch presented at (3) is also very interesting, and quite secure.)

1) http://igkt.net/sm/index.php?topic=3133
2) http://igkt.net/sm/index.php?topic=3020.msg22053#msg22053
3) http://igkt.net/sm/index.php?topic=3197.msg19074#msg19074
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roo

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Re: A noose-like hitch that can be untied after hard strain
« Reply #3 on: February 10, 2012, 07:54:30 PM »
   The hitch presented does not have an "excellent" security (of course !), but I am afraid that it does not has even a "good" security ... :) However, when pressed upon the surface of the object, we may say that it is not bad...
The hitch is intended to collapse against the object (hence the "squeezes" comment).  If you have some issue with the security of this hitch in its intended configuration, please let me know with a specific, concrete description of the problem.
« Last Edit: February 10, 2012, 08:04:12 PM by roo »
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xarax

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Re: A noose-like hitch that can be untied after hard strain
« Reply #4 on: February 10, 2012, 08:11:01 PM »
The hitch is intended to collapse against the object (hence the "squeezing" comment). 

   Then it is not bad...but I am not sure it is "good" either ! I believe the security of all the other hitches I have mentioned is noticeably higher . When I want to compare the security of two knots, I often tie them both with/on a monofilament fishing line, and watch how easily they slip there, and which slips first or more than the other...( One can enhance or deteriorate the security of a knot tied on a monofilament nylon fishing line, by some powder or greasy substance, so that the relative effects would be more pronounced.)

P.S. The Constrictor-based hitch mentioned in my previous post has yet another form, reported at (1) and shown as a picture at  (2).
1)  http://igkt.net/sm/index.php?topic=3020.msg21718#msg21718
2)  http://igkt.net/sm/index.php?topic=3020.msg21738#msg21738

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roo

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Re: A noose-like hitch that can be untied after hard strain
« Reply #5 on: February 10, 2012, 08:14:39 PM »
   Then it is not bad...but I am not sure it is "good" either ! I believe the security of all the other hitches I have mentioned is noticeably higher . When I want to compare the security of two knots, I often tie them both with/on a monofilament fishing line, and watch how easily they slip there, and which slips first or more than the other...( One can enhance or deteriorate the security of a knot tied on a monofilament nylon fishing line, by some powder or greasy substance, so that the relative effects would be more pronounced.)
This hitch is intended for rope.  A more relevant test would be slack shaking, flogging or repetitive bouncing with different rope types after setting the hitch.

« Last Edit: February 10, 2012, 08:17:14 PM by roo »
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knot4u

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Re: A noose-like hitch that can be untied after hard strain
« Reply #6 on: February 10, 2012, 08:21:32 PM »
It behaves like a Marlinspike Hitch, which doesn't slip if dressed correctly. So, I'm curious to know, Xarax, how exactly did this hitch slip on you?

When I want to compare the security of two knots, I often tie them both with/on a monofilament fishing line, and watch how easily they slip there, and which slips first or more than the other...

That seems awkward to me, given the physics of monofilament are substantially different. How does a Round Turn and Two Half Hitches work out for you in monofilament? There we have a boringly reliable hitch in rope, that's questionable at best in monofilament.
« Last Edit: February 10, 2012, 08:24:37 PM by knot4u »

xarax

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Re: A noose-like hitch that can be untied after hard strain
« Reply #7 on: February 10, 2012, 08:42:52 PM »
This hitch is intended for rope. 
That seems awkward to me, given the physics of monofilament are substantially different.

   The structure of a knot is the same when the knot is tied on a rope or a monofilament line...Two knots that will not slip very easily on rope - so we can not compare them when tied on rope -, will often slip when tied on a monofilament line. If that happens, we can compare those knots there, and we can suppose that what is revealed, the better or worse security of the one or the other, will be due to the knot structure, and not to the specific material ("physics"). It had never happened to me, when a knot slip less and it is more secure than another, when those two knots are tied on a certain rope material, to slip more and be less secure, when those two ropes would be tied on another material !
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Dan_Lehman

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Re: A noose-like hitch that can be untied after hard strain
« Reply #8 on: February 10, 2012, 08:51:57 PM »
I was searching for a non-slipped noose-like hitch (one rope around the object)
that
 collapses and squeezes the object,
 but can be untied after heavy load
 while having good to excellent security.

The shown hitch can be jammed a bit, but is a pretty neat
and simple one.

The stated conditions aren't specific on the type of security,
but your citing "shaking" implies what I call "slack-security".
It's also not clear that the structure should have decent
**noose-like** functioning --i.e., be able to slide snug upon
loading, as opposed to be set that way.  My suggestions
will not meet this 2nd condition.

A general tactic is to hitch (line to itself; *noose* is to object)
with a rolling, Blake's, anchor hitch, which will provide
good *noosing* for *spar* & larger objects, and maybe less
good for *rings*.  The knot components of these nooses
should provide adequate slack-security, and enable loosening
after a load (one can make a full /round turn before knotting,
too, where heavy loading is expected).

And, for a *spar*/*pile* noose (i.e., around relatively medium
or large objects), a clove hitch feeding a timber hitch
noose structure should work pretty well, too.


--dl*
====

knot4u

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Re: A noose-like hitch that can be untied after hard strain
« Reply #9 on: February 10, 2012, 08:56:22 PM »
   The structure of a knot is the same when the knot is tied on a rope or a monofilament line...Two knots that will not slip very easily on rope - so we can not compare them when tied on rope -, will often slip when tied on a monofilament line. If that happens, we can compare those knots there, and we can suppose that what is revealed, the better or worse security of the one or the other, will be due to the knot structure, and not to the specific material ("physics"). It had never happened to me, when a knot slip less and it is more secure than another, when those two knots are tied on a certain rope material, to slip more and be less secure, when those two ropes would be tied on another material !

Once security reaches 100% in rope (i.e., rope breaks before it slips), any additional data about security doesn't matter much. Here are some rope knots that are 100% secure for many rope applications, but are questionable at best in monofilament:

Round Turn & Two Half Hitches
Marlinspike Hitch
Sailor's Hitch
Timber Hitch
Fisherman's Knot
etc.

So, you tie one of these knots in monofilament, find out it slips in monofilament, lose confidence in the knot, and then end up tying some ridiculously large and unnecessary knot in rope. Is that how it works? I don't get the point.
« Last Edit: February 10, 2012, 08:58:02 PM by knot4u »

roo

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Re: A noose-like hitch that can be untied after hard strain
« Reply #10 on: February 10, 2012, 08:56:43 PM »
This hitch is intended for rope. 
That seems awkward to me, given the physics of monofilament are substantially different.

   The structure of a knot is the same when the knot is tied on a rope or a monofilament line...Two knots that will not slip very easily on rope - so we can not compare them when tied on rope -, will often slip when tied on a monofilament line. If that happens, we can compare those knots there, and we can suppose that what is revealed, the better or worse security of the one or the other, will be due to the knot structure, and not to the specific material ("physics"). It had never happened to me, when a knot slip less and it is more secure than another, when those two knots are tied on a certain rope material, to slip more and be less secure, when those two ropes would be tied on another material !
Some insights may be had, but it seems like there are more relevant tests and observations that can help select a specific hitch for a specific job.   For example, a hard pull in small nylon rope reveals that the hitch presented in this thread has better jam resistance than hitch shown in the image you attached.
« Last Edit: February 10, 2012, 10:11:04 PM by roo »
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roo

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Re: A noose-like hitch that can be untied after hard strain
« Reply #11 on: February 10, 2012, 09:56:16 PM »
The stated conditions aren't specific on the type of security,
All relevant types for rope.

Quote
It's also not clear ... --i.e., be able to slide snug upon
loading, as opposed to be set that way. 
I was envisioning that the squeezing of the object by the single line (no additional passes are allowed) would be due to any force on the standing part, regardless of when it was applied, but knots that refuse to hold any tension (in the manner of a running loop) should be excluded from consideration.

It's just that the lack of untyability of the Scaffold Knot was disappointing for this application.
« Last Edit: February 10, 2012, 10:34:36 PM by roo »
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xarax

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Re: A noose-like hitch that can be untied after hard strain
« Reply #12 on: February 11, 2012, 12:07:23 AM »
Once security reaches 100% in rope (i.e., rope breaks before it slips), any additional data about security doesn't matter much.

Do not say this again !  :) It is a sooo false a statement ! If that was so, our life would be much easier, that is true -but unfortunately or fortunately, it is not.

So, you tie one of these knots in monofilament, find out it slips in monofilament, lose confidence in the knot, and then end up tying some ridiculously large and unnecessary knot in rope. Is that how it works? I don't get the point.

Obviously  :) :)
Is that what I said ? Better, is that something I could have said ? And would you discuss  it with a person that had said such a nonsense ?

I will repeat it another time, in as plain a language as I can use ;
You tie two knots with/on a certain rope. They do not slip.  You tie them with a more slippery rope . They still do not slip . Are they equally secure ? If that was so, you do not need the most complex knot, because the security of the simpler one is as great as it can be, and anything more is redundant. History of the secure knots stops in the first century A.D. You are left with one knot : one hitch, one loop and one bend.  :)
Two knots tied on the same rope material do not slip. Are they equally secure ?  Of course not. Security of knots is a complex issue. The single most important factor is the structure, the geometry of the knot. This geometry remains (almost) the same, when the knots are tied with any of the usual ( not elastic ) materials. So, when we tie a knot with a very slippery material, like a non-coated spectra/dyneema, a monofilament fishing line, a dental floss thread, its structure remains the same. However, while the structure remains the same, the specific friction characteristics of the rope surface are different. A knot that will not slip when tied on a common rope material, may slip when tied on a more slippery material. ( Of course, all the other parameters are supposed to be the same, as the form and the initial force with which the knot is dressed in the first place, the type of the pull, etc )
What we like to test, when we compare two different knots, is their security related to their structure. If we can not do it on a non slippery material, because both knots do not slip there, we try to test it on a more slippery material. If we are lucky, we can find a slippery enough material where both knots do slip, but the one slips less than the other. If that is so, we can say that, tied on this X material, knot A slips more than knot B, so knot A is less secure than knot B. And this relation is going to be reversed with any other material Z, because it is the structure of the knot that is the single most important factor that dictates security, and this structure will not change significantly when the knot will be tied with this Z material. So, the relation will not be reversed. As I said in the previous post ;

   It had never happened to me, when a knot slip less and it is more secure than another, when those two knots are tied on a certain rope material, to slip more and be less secure, when those two ropes would be tied on another material !

The not-knot-tyer will jump and be eager to shout : But I am not interested in the security of my knot when tied on your slippery material ! I will always use this specific material in which my knot does not slip...so why I bother for any other condition ?
...and I will be eating the same breakfast each day, so I will dress and tie this same knot in exactly the same way each time, I have a ton of this rope material kept inside a completely controlled environment, so even if the manufacturer changes the chemical composition of the material or declares bankruptcy, this will not affect my ropes, it will never rain or snow in the place where I will always tie my ropes, my ropes will never suffer from fatigue, chemical degradation, sunlight, air or liquid acids, vibrations, accidental cuts on the surface, UV exposure, heat, curse from my wife...
   The only thing that remains almost the same, is the structure, the geometry of the rope - which is also the most important factor that determines its security. If you can compare different knot structures under the same circumstances, and find out that a knot is more secure than an other under those circumstances, this is not going to change under any other circumstances. When I say that a knot is more secure than another, I describe a relation that is independent of the specific circumstances, and only reveals a characteristic of the structures, the "geometry" of those knots, not their "physics".
« Last Edit: February 11, 2012, 12:20:26 AM by xarax »
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xarax

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Re: A noose-like hitch that can be untied after hard strain
« Reply #13 on: February 11, 2012, 12:12:01 AM »
there are more relevant tests and observations that can help select a specific hitch for a specific job.   For example, a hard pull in small nylon rope reveals that the hitch presented in this thread has better jam resistance than hitch shown in the image you attached .

I do not doubt this...I have not tested the jamming characteristics of this knot, or indeed of any other knot - because I do not know how I can do it, in a controlled, quantitative way. I have tested only its security, i.e,. if it slips more than the knot presented in this thread, or not.
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roo

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Re: A noose-like hitch that can be untied after hard strain
« Reply #14 on: February 11, 2012, 12:40:26 AM »
[...]
Is that what I said ? Better, is that something I could have said ? And would you discuss  it with a person that had said such a nonsense ?

I will repeat it another time, [snipped a lot]
Yikes.  Maybe we can save this for another topic or a new topic.  Let's try to curb the tangents.
« Last Edit: February 11, 2012, 12:41:14 AM by roo »
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