Author Topic: An adjustable loop : the tarpist knot  (Read 7726 times)

Bipbip

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An adjustable loop : the tarpist knot
« on: July 17, 2014, 06:05:26 PM »
Hello, a few years ago I invented a new knot (or so I'm allowed to think as long as nobody recognize an already existing knot). It's an original adjustable loop and I call it the tarpist knot.

Being able to easily adjust the length of the guylines is crucial when using a non-freestanding (english is not my main language, excuse-me if my sentences are a bit awkward or if I don't use the proper words) shelter on an uneven ground. When I began to camp, I used for this a loop made with the working end passed through a double overhand knot, but it had a lot of drawbacks : it can be hard to untie, tend to wrist the rope and may slip under relatively low loads. As soon as I learnt the classic loop made with a rolling hitch, I used it instead. Thought it was better, it didn't work perfectly.
One interesting property of my former knot was that the length of the loop was adjusted at the expense of working end, while the running knot being tied around the standing end, the loop vary at the expense of it. Using the running hitch, I missed that property an looked for an efficient adjustable loop that would have it. I found the one I'm presenting know.



Here is a post I made two years ago on a French hiking forum, showing it an discussing it against other adjustable loops. I translate and copy the part that concern specifically this new knot :

It is based upon the well known cow hitch/lark's head. It is simple, yet surprisingly efficient. It became my favourite tautening knot. I tested it with various rope and strings without it failing. It hold on the most slippery string I possess - I found it on the ground in a ski station, I don't know what it is made of, but the classic rolling hitch and other variants don't work on it.

How to do it :


First a cow hitch


Then we make a bight with the working end and pass it through the two loops of the cow hitch


We just have to draw the bight, the knot tighten


But it's still possible to make the working end slide through it when it's not loaded

It can be made mid-rope.
It is easier to tautens strongly, but will then became hard to untie if still loaded.
When unloaded, it will however remain easy to untie, especially if the loop is free, then you just have to pull the working end.
It will hold as long as the running side of the loop is not pulled more strongly than the other.
It can be secured with a half-hitch.


Here, made around the loop.


Here around the standing end, with a bight.

With a stopper knot as extra security, I'm considering using it in order to make an adjustable climbing lanyard.
« Last Edit: July 17, 2014, 06:15:25 PM by Bipbip »

Sweeney

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Re: An adjustable loop : the tarpist knot
« Reply #1 on: July 17, 2014, 06:53:33 PM »
Welcome to the forum Bipbip.

An interesting idea which I have not seen before and tried just now in paracord where it held well against a straight pull. However it does have a potentially serious drawback:
 
Quote
It will hold as long as the running side of the loop is not pulled more strongly than the other.

In fact any pull at all on the running side will cause slippage. That said what you were looking for is an adjustable loop where the end is pulled as opposed to sliding the knot. That being so this may be a useable solution. But looking at your French posting you did not try Blake's Hitch to make an adjustable loop. I have found that considerable force can be applied to the leg attached to this knot without any slippage at all (similar material tied with a rolling hitch does slide a lot more easily when the corresponding part is pulled).

I would be very wary of using the knot you describe in any situation where injury could result from a pull on the wrong part no matter how unlikely but for a tent guyline or similar situation where there is no risk to life and limb it's worth a try. Thanks for bringing it to our attention.

Barry

xarax

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Re: An adjustable loop : the tarpist knot
« Reply #2 on: July 17, 2014, 08:44:49 PM »
   What you demand from your knot is to succeed in a really difficult mission : in fact, you are searching for an adjustable (= not-fixed ) eyeknot (= a noose ), which would be able to immobilize the "returning" eye leg without severely deforming it ( = "locking" it ) - and without the help of a collar, of course. I know few places in KnotLand more harsh and deserted than this ...  :)
   If we suppose that the nub of the eyeknot will be ( and will remain so, all the time ) in contact with the encircled object, we may take refuge into the oasis of some hitches - the Buntline hitch been the most well-known of them. The adjacent solid surface of the object offers some additional support, as it helps the nub retain a compact form, and squeezes it from "below". By the help of this support, the nub can grip the returning eye leg more tightly ( = more efficiently ). However, without this, we have to rely only on the nipping power of the nub itself. It turns out that this is difficult, because it is like a double edge sword  :
   1. The nub may be too convoluted, in which case its many internal "turns" may absorb and consume ( = waste, for that matter ) a great portion of the tensile forces running along the Standing Part, leaving the penetrating eye leg almost free to slip unobstructed through it.
   2. The nub may be too simple, in which case it may shrink, close and "fold" around itself, and jam, jeopardizing the "adjustability" of the knot. The Clove hitch is such a very simple, but also very tight nipping structure, which is prone to jamming. To address this problem, we should better utilize the Girth hitch- although in a way different from the way you use it in your loop : the returning eye leg enters into the nub from the "opposite" side, which makes this eyeknot look like an "Eskimo" bowline (1).
   Have a look at the two "shape 8"- looking nooses, shown at the attached pictures, and try to compare them to your knot.
   For the most tight and well-balanced such loop I know, see (2).
   
1. http://igkt.net/sm/index.php?topic=4347.0
2. http://igkt.net/sm/index.php?topic=4464.msg32659#msg32659
   
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Bipbip

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Re: An adjustable loop : the tarpist knot
« Reply #3 on: July 18, 2014, 09:50:55 PM »
Thanks for sharing your opinions about this.

I would be very wary of using the knot you describe in any situation where injury could result from a pull on the wrong part no matter how unlikely but for a tent guyline or similar situation where there is no risk to life and limb it's worth a try.
I would in no way use it in a life safety situation without the half-hitch I shown and an additional stopper knot, as you mentioned it, there is a risk of accidentally pulling the wrong part. Even with those precautions I wouldn't use it before having consistently tested it.

I didn't knew the Blake's knot. I tried it with the thin cord I use with my shelter (I don't know what it is, maybe dyneema). It seems to work a lot better than the rolling hitch. A good addition to my set of knots.

I also tried the two knots Xarax indicates. I found the constrictor noose to either slip or become uneasy to adjust. The serpent noose works well with the fuzzy 10mm climbing rope I used for the photos, but slips on the cord I use with my shelter.

None of those rope work with that super-slippery string I aforementioned.

I tied the girth hitch-based adjustable loop shown here with this string and it performed well. However, with other strings or ropes, I found it to too easily change its configuration and jam.

My "tarpist knot" remains also easier and faster to tie and untie than any of those knots - at least when made "in the air", and not directly around an anchor point. I tried it with the thinnest string I have, a kite line. With such a thin string, though still easier to untie than the other knots it can jam and damage the string, a thing that don't seem to happen with thicker ones.

xarax

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Re: An adjustable loop : the tarpist knot
« Reply #4 on: July 19, 2014, 12:54:59 AM »
   I found the constrictor noose to either slip or become uneasy to adjust.

   You mean, you found it too loose or too tight, depending upon the amount of the initial dressing ?
   This is a disadvantage for any "adjustable lop", indeed, because, if that happens, in order to be sure the knot will hold, we would be forced to pre-tighten it as much as we can - to the point we should then need to almost untie it completely to release it ( provided it would not jam, and we would be able to do this...) before we will be able to adjust it again...
   In that sense, the search for an "adjustable" loop ( = easily adjustable loop ) becomes even more difficult, if not impossible !

None of those knots work with that super-slippery string I aforementioned.

  I do not believe that any eyeknot, where the continuation of the returning eye leg is not forced, by the surrounding / gripping nub, to bent, would be able to hold on a super-slippery material under a super-heavy loading - your knot included !  :)

 
  < the girth hitch-based adjustable loop >
  I found it to too easily change its configuration

  It is not a very well balanced knot ( as the Pretzel-based one ), that is for sure, and it can be deformed "easily" - but it does not "open up" "easily" - and, as far as I know, it does not jam, ever ! My theory is that a Girth hitch can never jam - because its two nipping turns do not have the same handedness, as the Clove hitch, so it can not work as a rope-made ratchet, and accumulate the tensile forces induced into it from its two ends. I had not been able to make any of the many Girth hitch - based "Eskimo" loops I had tried to jam, but I had not loaded any of them REALLY hard. 

  My "tarpist knot" remains also easier and faster to tie ... than any of those knots - at least when made "in the air"

  As it is more complex than the simple Girth hitch-based "Eskimo" loop you had tried, this can not be true !  :) However, if you have tied your knot many times, you may be able to tie it more quickly, and find it easier and faster to tie it, even from a much simpler knot, indeed - but only because of your experience, not because of the knot ! Anyway, the time required to tie all those knots is not a problem - and, certainly, it is not their main problem ! Will they be able to hold without been jammed, and, if they will be, will they also be able to be adjusted without first been completely released and then tightened again ? THAT is the problem !   

P.S. Have a look at the "slipped" versions of the Clove- and the Girth/Cow-hitch based loops, at the attached pictures.
« Last Edit: July 19, 2014, 01:19:11 AM by xarax »
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Bipbip

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Re: An adjustable loop : the tarpist knot
« Reply #5 on: July 20, 2014, 10:23:45 PM »
   I found the constrictor noose to either slip or become uneasy to adjust.

   You mean, you found it too loose or too tight, depending upon the amount of the initial dressing ?
Yes, it's what I meant.

This is a disadvantage for any "adjustable lop", indeed, because, if that happens, in order to be sure the knot will hold, we would be forced to pre-tighten it as much as we can
Mine don't have this disadvantage. You don't need to pre-tighten it.

I do not believe that any eyeknot, where the continuation of the returning eye leg is not forced, by the surrounding / gripping nub, to bent, would be able to hold on a super-slippery material under a super-heavy loading - your knot included !  :)
You may be right on this one. I have not tested this knot with what could be called a "super-heavy load" and it may exist some even more slippery materials. But the fact that it works when other adjustable loops don't is interesting.

It is not a very well balanced knot ( as the Pretzel-based one ), that is for sure, and it can be deformed "easily" - but it does not "open up" "easily" - and, as far as I know, it does not jam, ever !
Actually, we agree about this, I only meant that it can be deformed into a configuration where it can't be adjusted any more. As far as I can tell, it remains easy to untie. What you're saying about Girth hitch based knots never jamming is really interesting.

P.S. Have a look at the "slipped" versions of the Clove- and the Girth/Cow-hitch based loops, at the attached pictures.
I did. Are they not just "slipped" versions of the following knots (from here) ? Both seem to lack stability.

xarax

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Re: An adjustable loop : the tarpist knot
« Reply #6 on: July 21, 2014, 11:32:11 AM »
   I found the constrictor noose to either slip or become uneasy to adjust.

   You mean, you found it too loose or too tight, depending upon the amount of the initial dressing ?
Yes, it's what I meant.

   You may be right on this - although it depends on the material. Anyway, even if it depends on the material, a knot that has to be tightened carefully, not more or less than a certain amount, otherwise it will not function properly, should be avoided.

Mine don't have this disadvantage. You don't need to pre-tighten it.

I have not seen this. On the contrary, to make your knot able to hold, I had to pre-tighten it very much !

  Are they not just "slipped" versions of the following knots Both seem to lack stability.

  Yes, but this 'just" is not the right word. When we have the nipping loop(s) encircling two, rather than only one, rope diameters, many thing change more than anticipated. The curve(s) gets wider, and the stiffness of the "toggle-like" Tail is enhanced, so the knot becomes much more stable.
   I have loaded them almost to the limit of their strength - I have not seen them "open up", never.
   Now, if by this "unstable" you mean that, as they are loaded more and more, their initial geometry changes, I agree. However, the changing in geometry may be beneficial, not detrimental, regarding their ability to hold - and I have seen that this is happening in the case of the Clove hitch-based loop more than in the case of the Girth/Cow hitch-based one. In the Clove hitch, the knot jams, and it will not release the penetrating Tail before it will break. In the Cow/Girth hitch, the knot does not jam, but it runs the danger to be deformed badly, to the point it becomes unrecognizable - although I have never been able to make it "open up".
   The subject of adjustable loops is very interesting, and I do not believe it is explored as much as it deserves. Trying to figure out tight nubs, I had used double overhand knots, and other more complex "collared" knots, with mixed results. See (1). However, recently I have started to appreciate, and enjoy, the PET and TIB knots much more than a few years ago, so I had concentrated my efforts on PET and TIB loops. That is why I came to the conclusion that it will be very difficult / improbable to find anything better than the Pretzel loop - but that does not mean we should not try !  :) Go on !

1. http://igkt.net/sm/index.php?topic=2996.msg17841#msg17841
    http://igkt.net/sm/index.php?topic=2996.msg17842#msg17842
    http://igkt.net/sm/index.php?topic=2996.msg17843#msg17843
« Last Edit: July 21, 2014, 11:36:30 AM by xarax »
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Bipbip

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Re: An adjustable loop : the tarpist knot
« Reply #7 on: July 21, 2014, 03:54:42 PM »
Mine don't have this disadvantage. You don't need to pre-tighten it.

I have not seen this. On the contrary, to make your knot able to hold, I had to pre-tighten it very much !
What you're saying is quite surprising to me ! Making the knot as in the picture below, so loose that it's hardly recognisable (the carabiner shows where is the loop), I just had to pull the standing end for it to tighten by itself. Are we talking about the same thing ?

   Now, if by this "unstable" you mean that, as they are loaded more and more, their initial geometry changes, I agree. However, the changing in geometry may be beneficial, not detrimental, regarding their ability to hold]
That geometry change is not a problem as long as the loop remains easy to adjust. It seems that the girth-hitch based loop (I haven't tested the clove hitch-based one) can quite easily change in a way that it cannot be adjusted any more, even with the more stable slipped version.

xarax

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Re: An adjustable loop : the tarpist knot
« Reply #8 on: July 21, 2014, 06:27:37 PM »
That geometry change is not a problem as long as the loop remains easy to adjust.
It seems that the girth-hitch based loop can quite easily change in a way that it cannot be adjusted any more.

  The moment the nub of knot "closes" tightly around the penetrating eye leg and starts to grip it, we do NOT wish it to be adjustable any more ! Otherwise, it is not an adjustable loop ( that is, a fixed loop, a loop in which the size of its eye remains fixed while it is loaded, but it can be easily adjusted while it is not ), it is a slipping noose, for KnotGod s sake !  :) I was speaking about an adjustable loop in this sense all the time, evidently...

 
  Are we talking about the same thing ?

  We are talking about the same knot, but you seem to be satisfied if it serves as a noose ( there are dozens of simpler nooses out there...), while I am trying to transform it to an adjustable loop. So, I am telling you to pass the returning eye leg through the nub the other way, and see what happens. This way your knot is transformed into a decent "Eskimo"-like adjustable loop, which can hold quite well. However, the additional complexity ( in relation to the common/simple Girth hitch-based loop you have tried ) is perhaps redundant, and it may absorb a portion of the tensile-force-turned-into-gripping-power we need to reach the penetrating eye leg.
  The quality of your picture is great, but you do not need to show knots sooo loose : they do not remind knots any more !  :) The idea is to show the knots exactly as they are when they are tight and compact, and then "exploded" : that is, the size of all the openings OR of the rope itself is reduced. Also, I have seen that it is very hard to show a black rope : it requires a very careful control of the light, and I do not believe the outcome is worth the trouble.

   
Mine don't have this disadvantage. You don't need to pre-tighten it.

  I have not seen this. On the contrary, to make your knot able to hold, I had to pre-tighten it very much !
  What you're saying is quite surprising to me !

  I do not say that the knot dies not hold at all if it is not pre-tightened ! If you measure the angle between the returning eye leg and the axis of the knot when it is loaded, you will see that it is about 45 degrees - so there is much more friction than in the case it is 0 degrees !  :) However, I have seen that the holding power becomes really adequate for an adjustable loop, only when this angle is close to 90 degrees - and that is why I have use "Eskimo"-like loops,  and why I tell you to transform your knot into such a loop. 90 degrees, the right angle - that is the right angle !  :)
« Last Edit: July 21, 2014, 06:43:54 PM by xarax »
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xarax

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Re: An adjustable loop : the tarpist knot
« Reply #9 on: July 21, 2014, 07:06:43 PM »
  There is another issue with this knot I had not mentioned yet. It can be dressed in two ( at least ) district ways ( which is not a bad thing per se ), but the one of them holds much better than the other ( which is ! ). See the attached picture, and imagine the axes of the two coloured lines interchanged.
   So, you have to warn the user to dress it the one way, and not the other - and this is always a disadvantage regarding the practicality of a knot. I am always very disappointed when I find a knot that is much better when it is dressed in one way, and much worse when it is dressed in another way... and I can tell you it happens many times !  :)
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Bipbip

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Re: An adjustable loop : the tarpist knot
« Reply #10 on: July 21, 2014, 09:16:32 PM »
  The moment the nub of knot "closes" tightly around the penetrating eye leg and starts to grip it, we do NOT wish it to be adjustable any more ! Otherwise, it is not an adjustable loop ( that is, a fixed loop, a loop in which the size of its eye remains fixed while it is loaded, but it can be easily adjusted while it is not ), it is a slipping noose, for KnotGod s sake !  :) I was speaking about an adjustable loop in this sense all the time, evidently...
So it was a case of misunderstanding ! All my apologize for the confusion  :-[. Knots naming and vocabulary can already be confusing in one's language, translating it in an other, odds are great to make errors ! Translated literally in French, "slipping noose" refers to something like this (first picture below), or even this (second picture below), an entirely different kind of knot. The kind of knot I'm speaking about, and which the one I submitted is intended to be, is one that won't slip when loaded (in a certain extend of conditions, at least), but that the knot-tyer could still adjust at any time (after having released the load, though). Changing the length of the loop can be made slipping the working part through the knot, as in my knot, or sliding the nub along the standing part, a more common, but in my opinion less effective, option.

xarax

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Re: An adjustable loop : the tarpist knot
« Reply #11 on: July 21, 2014, 09:28:12 PM »
The kind of knot I'm speaking about, and which the one I submitted is intended to be, is one that won't slip when loaded (in a certain extend of conditions, at least), but that the knot-tyer could still adjust at any time (after having released the load, though). Changing the length of the loop can be made slipping the working part through the knot, as in my knot, or sliding the nub along the standing part, a more common, but in my opinion less effective, option.

  Yes, that is the kind of knot I, too, was speaking about all the time, so there is no misunderstanding about that.
  In the "pure" slipping noose you show, the angle I was talking about ( the angle that makes all the difference ! ) is 0 degrees. In your loop it is 45 degrees. If you transform it like I had said ( that is, make it "Eskimo"-like ) it becomes 90 degrees. I claim that we should always try to figure out nipping structures that keep this critical angle closer to 90 degrees, than to 45 degrees.
   
 
« Last Edit: July 21, 2014, 09:29:01 PM by xarax »
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Bipbip

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Re: An adjustable loop : the tarpist knot
« Reply #12 on: July 21, 2014, 11:11:55 PM »
  The quality of your picture is great, but you do not need to show knots sooo loose : they do not remind knots any more !  :)
That's was my very idea, indeed showing the knot in configuration where it don't look like a not any more, but still will tighten "by itself" if we pull the standing part. It wasn't meant to be a clear depiction of it. I made three pictures for this, of better quality than the blurry webcam shots of my first post.

  In the "pure" slipping noose you show, the angle I was talking about ( the angle that makes all the difference ! ) is 0 degrees. In your loop it is 45 degrees. If you transform it like I had said ( that is, make it "Eskimo"-like ) it becomes 90 degrees. I claim that we should always try to figure out nipping structures that keep this critical angle closer to 90 degrees, than to 45 degrees.
I think I get that angle part - finally ! Would the Eskimo-like version be this (4th photo) ? Yes its seems stronger, but it cannot be easily tied in the bight. In such cases when strength would matters the more, I would use this one, whenever speed and ease to tie and untie is critical, I would stay with the other.

xarax

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Re: An adjustable loop : the tarpist knot
« Reply #13 on: July 21, 2014, 11:28:36 PM »
Would the Eskimo-like version be this (4th photo) ?

 Yes.

it cannot be easily tied in the bight.

 It cannot be tied in the bight, period !  :) A knot either can or can not be tied in the bight - it is a matter of topology, not geometry.
  Yes, that may be considered a sort of disadvantage, indeed.   

... when strength would matter the more, I would use this one, whenever speed and ease to tie and untie is critical, I would stay with the other.

  Wise decision !  :)
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Bipbip

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Re: An adjustable loop : the tarpist knot
« Reply #14 on: July 21, 2014, 11:48:56 PM »
The first picture attached to this post show the kind of guyline string I most often use. This is why I put a stress on the ease to tie and untie. Imagine doing this in the cold and in the dark (yes, we can't see clearly the knot with this black string :)).

  There is another issue with this knot I had not mentioned yet. It can be dressed in two ( at least ) district ways ( which is not a bad thing per se ), but the one of them holds much better than the other ( which is ! ). See the attached picture, and imagine the axes of the two coloured lines interchanged.
I've see this happening many time with small strings, and yes, it's quite annoying. I don't know which way is the weaker but I know which one I hate to see. When the positions of those two parts are shifted (see picture below), the loop part of the knot will twist after a few adjustments in its length (last picture). The result, when carelessly undoing the knot by pulling the working end is that the twisted loop can jam.