Author Topic: A fixed loop for springy polypropylene rope  (Read 19654 times)

X1

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Re: A fixed loop for springy polypropylene rope
« Reply #15 on: November 26, 2012, 03:48:03 PM »
Heatshrink should not be melted, it is heated so that it shrinks back to it's original diameter.

  I do not understand this technique... If something is heated it does not shrink - quite the opposite. Only if there is a local permanent deformation of the material, it can occupy less volume than before its heating, and this is what I describe by "melting". Could you, please, explain it to me once more ? I see that the finished result is sleak, indeed, but, if we could magnify it at a smaller scale, I am afraid we would see that the individual fibres would be "melted", deformed.   

Sweeney

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Re: A fixed loop for springy polypropylene rope
« Reply #16 on: November 26, 2012, 04:32:00 PM »
  I do not understand this technique... If something is heated it does not shrink - quite the opposite. Only if there is a local permanent deformation of the material, it can occupy less volume than before its heating, and this is what I describe by "melting". Could you, please, explain it to me once more ? I see that the finished result is sleak, indeed, but, if we could magnify it at a smaller scale, I am afraid we would see that the individual fibres would be "melted", deformed.   

Heat shrink tubing (used extensively for electrical work) is a plastic tubing which in this case is slipped over the rope and then heated - a hairdryer will suffice - causing the tubing to shrink significantly, gripping the rope around which it has been placed (but having no effect on the fibres of the rope itself). In the picture of Marlow rope the tubing is transparent though I generally use black for whippings. A more expensive version of heat shrink tubing has glue inside which melts at relatively low temperature though a drop of glue applied before the tubing is a lot cheaper. Although the tubing softens (and hardens when cool) it does not "melt" to the extent that it liquefies.For more info see http://en.wikipedia.org/wiki/Heat-shrink_tubing

Barry

Dan_Lehman

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Re: A fixed loop for springy polypropylene rope
« Reply #17 on: November 26, 2012, 06:17:33 PM »
Above, I suggested using a double overhand eyeknot ;
here, let me point out that this can be slightly reduced
in bulk by making it not *double* but *1-&-a-half* :
the SPart's part can make the doubling turn, while
the tail's path is merely a (single) overhand.
(And, yes, also *vice versa* : tail making the double half.)


--dl*
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X1

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Re: A fixed loop for springy polypropylene rope
« Reply #18 on: November 26, 2012, 06:59:45 PM »
   Thank you Banbocan, Sweeney,
   
   The mentioned article of Wikipedia is not very informative, I am afraid.
   
  Depending on the material used, there are two ways that heat shrink may work.

   1.   If the material contains many monomers, the monomers polymerise when the tubing is heated. This increases the density of the material as the monomers become bonded together, therefore taking up less space. Accordingly, the volume of the material shrinks.[citation needed]
 
   2.   Heat shrink can also be expansion-based. This process involves producing normal tubing, then heating it to just above the polymer's crystalline melting point and mechanically stretching the tubing (often by inflating it with a gas); finally, it is rapidly cooled. Later, when heated, the tubing relaxes back to its un-expanded size.


   The second process is what I had in mind :  It involves melting, mechanical expansion, rapid cooling that stabilizes the molecular structure of the material at the expanded size / stage, and then heating to "revitalize" the stress "memory" of the material, and so allow it to retain to its original size. It works like a one-piece hose clamp.
   The first process is also a kind of melting, at a molecular scale. Heat is used to induce a chemical transformation of the molecular structure of the material, the polymerization, which changes the shape of the molecules, and thus their size. I believe this is a one-off process, because I do not see how those polymerized polymers can possibly return to their initial form. Citation needed !  :)

   With all respect, I think that both procedures are not very different from gluing !
   I belong to an other era, where when one needed to join two pieces of material together, he used nuts and bolts, dovetails, mortices and tenons, and all that. So, I guess I will never characterize the method of joining two things together by using glue, as "elegant ". 
   Most knots, if not all of them, will become permanent and super-strong, if we immerse them in a contemporary strong glue... I am not ready to propose this to a knot tyer ! Also, if the cost of rope becomes more negligible, one would possibly prefer to glue the ropes together, and then just to cut-off the joined segments, or buy new ropes. "Gluing and cutting-off" would become the method of choice, and the word "knot" will be forgotten. Fortunately, I will not live to see this day !  :)
« Last Edit: November 26, 2012, 07:05:10 PM by X1 »

X1

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Re: A fixed loop for springy polypropylene rope
« Reply #19 on: November 26, 2012, 07:35:13 PM »
I suggested using a double overhand eyeknot ;
 this can be slightly reduced in bulk by making it not *double* but *1-&-a-half* :

   This reminds me of another type of "double overhand" , that of the "1 plus 1" overhand.
   A "1 plus 1" overhand knot/stopper can be tied in two ways. The first one can be cobsidered as a " 1 plus a half " overhand, while the second looks more like a genuine " 1 plus 1 " overhand. The retraced (R) knots are very tight, very secure knots, that may even be used instead of the triple fisherman knot, as bends joining very slippery ropes. ( See the attached pictures ). 

Luca

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Re: A fixed loop for springy polypropylene rope
« Reply #20 on: November 27, 2012, 09:53:59 PM »
Hi X1,

   A "1 plus 1" overhand knot/stopper can be tied in two ways. The first one can be cobsidered as a " 1 plus a half " overhand, while the second looks more like a genuine " 1 plus 1 " overhand. The retraced (R) knots are very tight, very secure knots, that may even be used instead of the triple fisherman knot, as bends joining very slippery ropes.

A third way to obtain another knot(always symmetric)of this type,can be by imagining a Shakehands bend(without the tails crossed),the whose tails are"merged"together,a little as well as the two stopper knot that you show above can be seen as the result of the "merged tails" of the Zeppelin and the Hunter's.
I too have tried the retraced bends that can be obtained from these stopper knots,in the days when we were talking about the Water bend in your"Interlinked and interwoven overhand knot bends" thread.
I also tried a retraced bend obtained from the shape of Abok # 1192,a hitch which can be regarded as the same of a "falsely tied Hunter's bend"with merged tails, obtaining in this way a form similar to a sort of doubled Trefoil knot.

Regarding the topic of this thread,I think maybe the solution that could discourage a kid from trying to untying the loop,if we want to stick to true knot tyer's solutions,is to get some old style twisted rope and bring the matter directly to an eye-splice (actually I'l ve never done one in my life!).(even if, after trying the Oyster loop, I have to say that is just as beautiful as it is difficult to melt!)

                                                                                                          Bye!

X1

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Re: A fixed loop for springy polypropylene rope
« Reply #21 on: November 27, 2012, 10:16:29 PM »
[retracing] a Shakehands bend [where the tails] are "merged" together

Which Shakehands bend ? (1)
 ( I do not understand why you insist using verbal descriptions, and verbal descriptions only, and do not accompany them with a few telling pictures... Presenting pictures of knots is not a sin !

1. http://igkt.net/sm/index.php?topic=3278

Luca

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Re: A fixed loop for springy polypropylene rope
« Reply #22 on: November 27, 2012, 10:46:56 PM »
The"-X"Shakehands(without the tails crossed).
I do not have a digital camera,and do not have a scanner(and do not have money! :()

X1

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Re: A fixed loop for springy polypropylene rope
« Reply #23 on: November 28, 2012, 12:43:45 AM »
I do not have a digital camera

   The great majority of people on planet Earth, have a mobile phone, and the great majority of mobile phones incorporate a digital camera. Given that the great majority of people have one or more friends that will have a phone that will incorporate a digital camera, I reckon that you should be a very unlucky man, indeed !  :) At least, I hope you have some rope left ...
   The retraced Shakehands ( crossed-tails or not, it does not matter, sinse you merge them...) you mention should be the knot at the attached pictures. I would describe it as a retraced 1 + 1 overhand knot. Those "double" knots, where the one overhand knot is interlinked with the other, are less jamming than the genuine double overhand knots, because of the effect I had tried to explain in a previous post : the shrinking of the one overhand knot does not force the shrinking of the other, so their combined jamming effect is a result of addition rather than a multiplication. On the contrary, the combined effect of the two fig.8 knots - links the Oyster bend makes this knot almost impossible to untie.
« Last Edit: November 28, 2012, 12:47:14 AM by X1 »

knot4u

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Re: A fixed loop for springy polypropylene rope
« Reply #24 on: November 28, 2012, 02:36:33 AM »
I like the Oyster Bend/Loop plus melting things together with a flame for the win.  This setup will be permanent whether you like it or not.  If you don't want to melt the knot with a flame, then I like the idea of heat shrink tubing.  By the way, Xarax, I am unfamiliar with your explanation of how heat shrink tubing works.

X1

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Re: A fixed loop for springy polypropylene rope
« Reply #25 on: November 28, 2012, 04:28:36 AM »
I am unfamiliar with your explanation of how heat shrink tubing works.

  I know next to nothing about it ! I have just read the Wikipedia article suggested to me by Banbocan, and I have tried to connect the dots. I think I got the general idea, but I am not very sure about it....
http://en.wikipedia.org/wiki/Heat-shrink_tubing
 
  (The Oyster bend/loop does not need any glue, believe me. Just dress it properly, and pull the ends hard. The only thing you may need afterwards, would be a marlinspike - or a sharp knife. )
« Last Edit: November 28, 2012, 12:48:59 PM by X1 »

Luca

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Re: A fixed loop for springy polypropylene rope
« Reply #26 on: November 28, 2012, 01:17:39 PM »
Hi X1,

[After attempting suicide with my 25 cm of 2.5 mm polyester rope (I tried to see if at least I could join a pair of shoelaces, but unfortunately I only own a pair of loafers, I will ask some friend if lends me a pair of shoes with laces).]

Thanks for the(beautiful as always) photos! Seem to represent exactly the knot and the bend of which I wrote; you're right, if one connects the tails, it does not matter whether they are crossed or not:is a lack of reasoning on my part,you gave me to correct.
I too had  noticed that maybe this type of knots are virtually unjammable; I had deduced (in a way simplistic compared to how you wrote,for me it is always stimulating and instructive to read your words about the knots) that it is because  is the interlink between them,that is acting in a way that one Overhand prevents to tighten the other (and vice versa).

OK, but what about the beautiful and ultra-jammable Oyster loop / bend (when I wrote "difficult to melt," was my mistake (comical, about the context in which it occurred) due to Google translate; I really wanted to write "difficult to untying "),since you were a little sarcastic,above,towards me, I want to revenge, and therefore will not tell you where you made a little mistake writing about this knot :P.

                                                                                                       Bye!

TMCD

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Re: A fixed loop for springy polypropylene rope
« Reply #27 on: November 28, 2012, 02:10:22 PM »
Without reading through this entire thread, may I suggest the quite common, Angler's Loop. It's supposedly hard to untie after being loaded and it's a fixed loop...also can be tied in the bight. I'm sure there's a hundred different reasons why this one won't work but after reading your OP, it's what crossed my mind.

X1

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Re: A fixed loop for springy polypropylene rope
« Reply #28 on: November 28, 2012, 04:01:17 PM »
one Overhand prevents the tightening of the other (and vice versa).

I would rather say that the one Overhand helps the un-tightening of the other...

I want to revenge, and therefore will not tell you where you made a little mistake writing about this knot :

THAT hurts, indeed !  :) Come on, Luca, you know that this is a disproportional action by you against my humorous attempt... Please...???... :)

may I suggest the quite common, Angler's Loop. It's supposedly hard to untie after being loaded and it's a fixed loop...also can be tied in the bight.

   Ashley wtites tha "as it jams, it is not suitable for rope". I have never loaded an Anhler s loop so tightly, perhaps because I use thick ropes and relatively light loadings... Sionce I do not see the "multiplicative", coordinated effect of two shrinking bights the one forcing the other to shring further, I suppose that it will not jam to the poimt the knot could be characterized as "permanent" .

Luca

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Re: A fixed loop for springy polypropylene rope
« Reply #29 on: November 28, 2012, 05:48:45 PM »
On the contrary, the combined effect of the two fig.8 knots - links the Oyster bend makes this knot almost impossible to untie.


I want to revenge, and therefore will not tell you where you made a little mistake writing about this knot :

THAT hurts, indeed !  :) Come on, Luca, you know that this is a disproportional action by you against my humorous attempt... Please...???... :)

Haa ... now I understand! Was another trap! (Because here the things are written more precisely: http://igkt.net/sm/index.php?topic=1919.msg18926#msg18926 )

My tremendous and disproportionate revenge falls into the void!
But it does not end here, we will meet again!(:D)

P.S. How many beautiful bends in that thread!
« Last Edit: November 28, 2012, 05:53:04 PM by Luca »