International Guild of Knot Tyers Forum

General => Practical Knots => Topic started by: Sweeney on March 17, 2012, 05:12:08 PM

Title: A fixed loop for springy polypropylene rope
Post by: Sweeney on March 17, 2012, 05:12:08 PM
I have a problem and although I have a possible solution it may not be the best.  I am tying a fixed loop in 6mm split film polyprop. This loop must be fairly quick and esy to tie and - here's the unusual bit - I want it to be as difficult to undo as possible. The bowline and variations tend not to hold well in this stuff as it's so springy and in any event they are, by their nature, relatively easy to undo. Splicing takes too long and I am not a fan of splicing this stuff anyway. I have access to the working end and the standing part but not the end of the standing part.

What I came up with was this: tie a loose overhand knot in the standing part at the point where the loop knot is required. Now tie double overhand (ie a scaffold knot) through the overhand over the crossing part so that instead of a noose when tightened the initial overhand knot stops the double overhand from sliding. The load on the rope is likely to be less than 5% of its breaking strength so knot strength is largely irrelevant. And it certainly jams tight! Anybody got a better idea?

Barry
Title: Re: A fixed loop for springy polypropylene rope
Post by: SS369 on March 17, 2012, 06:31:26 PM
Hello Barry.

There are a few modified bowlines, secured, that could work, see  http://igkt.net/sm/index.php?topic=19.15 (http://igkt.net/sm/index.php?topic=19.15) thread #19. Just pull all the legs tight while hold the knot body, the tail last.

But what comes to mind is that many fishing loops would work like magic. I like the Double for slick cord. http://www.fishing-khaolak.com/knots/plaiting_a_double_steps.html (http://www.fishing-khaolak.com/knots/plaiting_a_double_steps.html) . You will knot need to braid as much as shown for it to be a strong loop.

Hope this helped.

SS
Title: Re: A fixed loop for springy polypropylene rope
Post by: Sweeney on March 17, 2012, 06:48:04 PM
Thanks Scott. I have a copy of Geoff Wilson's fishing kots book and I've tied double braid in monofilament but never in something this thick - I'll give it a go. Your lock for the bowline interests me as well but I'm not sure how much it resists untying (not lack of security - I'm tying a loop that a child aged say 12 - 14 cannot untie easily for safety reasons). Again I'll give it a go. The fact the end points back along the standing part is handy.

Barry
Title: Re: A fixed loop for springy polypropylene rope
Post by: SS369 on March 17, 2012, 07:51:51 PM
I'm glad the mental nudge was handy, some of us (me) could use a few time and again. ;-)

As for the untying, as you must know, any industrious individual can probably make work of it and do it, but I think you'll be pleased with the difficulty. That stuff you're working with is slippery and once crushed in the knot should deter long enough for a un-dared/not motivated child to lose interest.

Could use a dollop of adhesive too, though I doubt that will be necessary.

SS
Title: Re: A fixed loop for springy polypropylene rope
Post by: knot4u on March 17, 2012, 09:15:15 PM
Since you want it to jam, why not use an adhesive (per SS369 above) or a flame to burn things together?
Title: Re: A fixed loop for springy polypropylene rope
Post by: Sweeney on March 17, 2012, 10:22:28 PM
Thanks again Scott and Knot4U - I have now tried the bowline lock and it does indeed tighten well with no sign of loosening in poly rope.  Adhesive is a good idea and I had thought about using a hot melt gun but as polyprop has a low melting point I dropped that idea - as with applying a flame etc it is very difficult to control. However thinking along those lines it struck me that as the WE runs parallel to the SP a cable tie pulled tight enough to clamp the SP and WE would deter all but the most determined. Any knot can be undone given enough effort (and maybe a rusty nail!) - in the case in point I think the cable tie and a tightly drawn up knot will suffice to deter most kids.

Although not what this is about I have noticed lifebelts along the local beach where the rope is not actually attached to the lifebelt (polyprop again) because some idiot has undone a splice or knot. Those I've seen I've retied with a scaffold knot (triple overhand) pulled up tight around the edge of the lifebelt. You do wonder at the mentality of some people.

Barry
Title: Re: A fixed loop for springy polypropylene rope
Post by: SS369 on March 17, 2012, 10:44:32 PM
Glad that worked for you Barry, but now you have my curiosity peaked. What may I ask is the loop to be used for?
Inquiring minds and all that..  ;-)

SS
Title: Re: A fixed loop for springy polypropylene rope
Post by: Dan_Lehman on March 18, 2012, 05:13:51 AM
Rather surprised at the responses.

Quote
But what comes to mind is that many fishing loops would work like magic. I like the Double for slick cord

Somewhere the criterion for quick-tying was lost,
and, frankly, I doubt this is all so secure in lesser
lacing (and quite expensive in material)!

Quote
Any knot can be undone given enough effort ...

Good luck w/those rosy glasses, mate!  Apparently, the term
"welded" hasn't come your way w/knots; it has, for many.

My first thought ran to a double overhand eyeknot
(i.e., like the overhand loop but w/a strangle (or more));
that's quickly tied and firmly set.  Your idea is along these
lines for a component, and should suffice.

Looking to fishing knots for inspiration, I take the
old favorite, the blood knot, and work an eyeknot
out of it, as follows (with orientation of SPart running
away leftwards, eye to-be-formed at right, horizontally
disposed working) :

1. make an ample 270deg anti-clockwise loop, and form
a bight --the size of desired eye-- at the closure of this
loop (i.e., where it crosses the SPart) and have bight
cross OVER SPart; a bit of tail stays above SPart, and
to left of other bight leg;

2. Wrap tail back around SPart to up now on right of
bight-crossing.

3. Now, this big loop (not the eye bight, but the first-formed
ample loop) will be material you can easily increase/decrease
with which to essentially make a common whipping
wrapping of the SPart & eye bight with, turning it
back-downUNDER-forward-up ... a few times;

4. Then haul the SPart to set this whipping wrapping
tight against the eye-bight's single turn.

(The general idea came to me from seeing in Barnes
the joining of a short bight's tails to a line using the
blood knot working --2 strands vs. 1.  It occurred
to me that were one to fuse the single-line's (SPart's)
tail to one of the bight's tails, you'd have a normal
eyeknot (with one tail), TIB (Tiable Inthe Bight), too!)

The same knot could be tied beginning at though to
tie a double strangle knot and just modifying the
finish to be with the one-turn-secured end bight.

Then, again, a simple, overhand loop is considered
pretty jamming --the tying is simple, you just need
to give it a hard setting, well beyond what kids will
have means to untie.


--dl*
====
Title: Re: A fixed loop for springy polypropylene rope
Post by: Sweeney on March 18, 2012, 02:11:31 PM
Thanks Dan - I will try experimenting with some local Scouts and see how they get on attempting to undo various knots. Makes a change from trying to teach them to tie them!

Barry
Title: Re: A fixed loop for springy polypropylene rope
Post by: Sweeney on March 20, 2012, 07:00:33 PM
What may I ask is the loop to be used for?
Inquiring minds and all that..  ;-)
SS
Sorry, I forgot to reply to this. The loop is at the seaward end of a means to anchor a kids inflatable to the beach. There will be relatively little force on the loop but I don't want bored kids playing with it and trying to undo it (stupid as that would be, it'll happen). Some of the winds and tides here can have toy boats etc floating out to sea before adults, who should be supervising, notice and it's another job for the inshore lifeboat at best. At the moment I'm experimenting with loads etc. including any danger to swimmers and other beach users (though this is designed to be used in very shallow water close inshore).

Barry
Title: Re: A fixed loop for springy polypropylene rope
Post by: SS369 on November 25, 2012, 04:39:06 PM
Good day Barry.
Reading through posts I find some that just are left hanging, for one reason or another. I am wondering if you settled on a solution to your challenge.
Or did summer come and go with time lost?

SS
Title: Re: A fixed loop for springy polypropylene rope
Post by: X1 on November 25, 2012, 09:33:24 PM
This loop must be fairly quick and easy to tie and - here's the unusual bit - I want it to be as difficult to undo as possible.

   The most difficult to undo knot I had ever come across , is the "Oyster" bend ( M. B 5 ). When tightened, it becomes a rigid sphere, that is awfully difficult to untie ! Try it as a loop knot, it might suit to your purpose. ( See the attached pictures ).
Title: Re: A fixed loop for springy polypropylene rope
Post by: Benboncan on November 26, 2012, 12:09:07 PM
The most tamperproof solution in my opinion would be to splice followed by heatshrink tubing over the splice. You don't have to use a flame for the tubing, a soldering iron or similar presented near the tubing does the job in a controlled manner. Simple and elegant.
Title: Re: A fixed loop for springy polypropylene rope
Post by: X1 on November 26, 2012, 12:17:38 PM
Simple and elegant.

  Simple, in a looose sense of the word, it might be, indeed. However, it is not elegant ! I have never thought that the word "elegant" would be used for a melted thing !  :)
Title: Re: A fixed loop for springy polypropylene rope
Post by: Benboncan on November 26, 2012, 01:02:42 PM
Heatshrink should not be melted, it is heated so that it shrinks back to it's original diameter. Melting is not an option, there is a clue in the name.

Edit
An example of heatshrink used extensively on arborists equipment these days, this one is sewn first.

http://outdoorxscape.co.uk/store/arboriculture-rope/rope-marlow-split-tails-13-5mm-dia-x3.html
Title: Re: A fixed loop for springy polypropylene rope
Post by: X1 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.   
Title: Re: A fixed loop for springy polypropylene rope
Post by: Sweeney 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 (http://en.wikipedia.org/wiki/Heat-shrink_tubing)

Barry
Title: Re: A fixed loop for springy polypropylene rope
Post by: Dan_Lehman 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*
====
Title: Re: A fixed loop for springy polypropylene rope
Post by: X1 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 !  :)
Title: Re: A fixed loop for springy polypropylene rope
Post by: X1 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 ). 
Title: Re: A fixed loop for springy polypropylene rope
Post by: Luca 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!
Title: Re: A fixed loop for springy polypropylene rope
Post by: X1 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
Title: Re: A fixed loop for springy polypropylene rope
Post by: Luca 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! :()
Title: Re: A fixed loop for springy polypropylene rope
Post by: X1 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.
Title: Re: A fixed loop for springy polypropylene rope
Post by: knot4u 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.
Title: Re: A fixed loop for springy polypropylene rope
Post by: X1 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. )
Title: Re: A fixed loop for springy polypropylene rope
Post by: Luca 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!
Title: Re: A fixed loop for springy polypropylene rope
Post by: TMCD 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.
Title: Re: A fixed loop for springy polypropylene rope
Post by: X1 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" .
Title: Re: A fixed loop for springy polypropylene rope
Post by: Luca 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!
Title: Re: A fixed loop for springy polypropylene rope
Post by: X1 on November 28, 2012, 07:43:46 PM
  Sometimes I write ( inadvertently) "figure" 8 instead of "shape" 8, and vice versa... I believe I do this because, regarding bends made from symmetric interlocked knots, the general behaviour of the 8-shaped overhand-knot-based bends depends more on their geometry, than on their topology - and their geometry is similar to that of a fig 8 knot.

http://igkt.net/sm/index.php?topic=3148.msg18869#msg18869
http://igkt.net/sm/index.php?topic=3148.msg19946#msg19946
http://igkt.net/sm/index.php?topic=3148.msg19948#msg19948
Title: Re: A fixed loop for springy polypropylene rope
Post by: Mike on November 29, 2012, 12:30:14 AM
This loop must be fairly quick and easy to tie and - here's the unusual bit - I want it to be as difficult to undo as possible.

   The most difficult to undo knot I had ever come across , is the "Oyster" bend ( M. B 5 ). When tightened, it becomes a rigid sphere, that is awfully difficult to untie ! Try it as a loop knot, it might suit to your purpose. ( See the attached pictures ).

I just tied a loop knot with the oyster bend.    I like it.    Very secure and good looking too.   This might even make a good lanyard knot.