Author Topic: Constriction cam-action knot for sleeping bags, compression, camping  (Read 23830 times)

xarax

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Re: Constriction cam-action knot for sleeping bags, compression, camping
« Reply #15 on: March 06, 2014, 06:41:20 AM »
   Hi Luca,
   I had never thought to use the Locked Cow hitch as a mid-air binder !   :)  When I saw your knot, I grasped the first rope that was near me and ran to my laboratory ( the two central heating pipes in my living room, where I test the binders... :)). I am sorry to report that it was a great disappointment - compared to the rock-solid hitch on a pole, the same hitch around two rope diameters was... soft, to say the least !  :)  The mechanical advantage does not seem to work, and the Tail End, without the support of a solid surface underneath it, can not be squeezed enough, so, in its turn, can not push and block the slippage of the Standing End - which blockage of the Standing End, I should stress, in this case it is not even required most of the times - because binders are supposed to always remain under some minimum tension. Noope, definitely this hitch, marvellous when tied around poles, is just mediocre when tied around a pair of ropes segments.
   The golden standard remains the Gleipnir - nowadays I use the Gleipnir with a Clove hitch instead of a single or a double nipping loop, because, once tensioned enough, the Clove hitch accumulates the induced tension and remains tight - so it provides a more stable basis for the Gleipnir arrangement, even during a possible temporary release of the loading. In other words, I have learned to use the jamming characteristics of the Clove hitch, and I have implemented this trick in the Gleipnir just as in the recently presented Bull / Clove hitch. (1)
  it is very difficult to nip a tensioned straight rope segment - the only thing we can do is to insert the Tail end into the nipping structure only after it has just made an L-shaped deflexion, a "hook" that can more easily be attached to a corresponding "handle" provided by the Standing Part.
  The most effective nipping structure I have met is the double/crossed nipping loop of the Pretzel adjustable loop (2) - because it is very tight AND very well balanced, in relation to the axis of the loading. It will not rotate, so the L-shaped deflexion of the Tail End before it enters into the nipping structure will not run the danger to be straightened out. However, I have not yet figured out how to combine, and merge two such nipping structures into one, as a possible alternative to the Gleipnir / Clove. 

1. http://igkt.net/sm/index.php?topic=4748.0
2. http://igkt.net/sm/index.php?topic=4464.msg28357#msg28357
« Last Edit: March 06, 2014, 06:43:54 AM by xarax »
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Luca

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Re: Constriction cam-action knot for sleeping bags, compression, camping
« Reply #16 on: March 07, 2014, 04:57:50 PM »
Hi xarax,

  ...compared to the rock-solid hitch on a pole, the same hitch around two rope diameters was... soft, to say the least !  :)  The mechanical advantage does not seem to work, and the Tail End, without the support of a solid surface underneath it, can not be squeezed enough, so, in its turn, can not push and block the slippage of the Standing End - which blockage of the Standing End, I should stress, in this case it is not even required most of the times...

Surely there are mid-air binders better than this, and just as surely  you have in mind quality standards better than what I have in mind(in other words: beware my little gifts ;D!), but, given the very nearly absolute faultiness of good results described by you,I have led to the hypothesis that there is some misunderstanding regarding the direction in which you pull  on the standing end in order to tighten the binder, because to me it happens exactly the opposite of what you describe! If you pull on the standing end in the direction suggested (perhaps not so clearly) in the diagram, so that form a U-turn passing through the Cow hitch component, you will notice the effectiveness of the mechanical advantage (which of course also depends on the shape and the surface type of the wrapped object .) You will also notice that, especially with strings of small diameter, the risk that the Cow hitch component jams squeezing rock solid against the two diameters of rope that wraps around, is quite high: if one does not want to run a slipped version (which however will increase to three the diameters of rope wrapped), I suggest to leave slack the U-turn that  the tail end forms before finally returning through the Cow hitch component...
Pulling the standing end in the opposite direction (ie to the left in my diagram)instead I see that it is exactly what you describe!(:))

                                                                                                             Bye!

xarax

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Re: Constriction cam-action knot for sleeping bags, compression, camping
« Reply #17 on: March 07, 2014, 06:35:02 PM »
  Soft ! :) :) :)

  First, see the binders ( and read the, fortunately, not-long texts !  :) ), shown at :
  http://igkt.net/sm/index.php?topic=2996.msg17831#msg17831
  http://igkt.net/sm/index.php?topic=2996.msg17841#msg17841
  and the next posts. You could possibly test them, and report your results to us.
   Second : The angle between the axis of the knot / loading, and the Tail End, should be close to the right angle, or even a little bid less ( more acute ) - not obtuse. If it is very obtuse, the L-shaped deflexion we need will not be adequate, so the Tail End will tend to be aligned to the Stranding End, and it will slis through the nub - any nub, however tight it is... If it is very acute, we would not be able to pull the end and re-adjust / tighten the binder.
   In a correctly balanced nipping / constricting nub ( as nub of the Pretzel adjustable loop ), which does not rotate to the wrong direction, ready to release its grip, the Tail End forms this right angle "hook", corresponding to the nub s "handle", so the nipping / constricting action becomes enough to secure it.
   Third : See those two parallel and adjacent segments into the nub s core ? They tend to slide on each other, like the skis on the surface of the snow !  :) In order to block the slippage of a tensioned segment, you have to bite it hard and deep, with segments at a right angle to it.

« Last Edit: March 07, 2014, 06:46:35 PM by xarax »
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Luca

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Re: Constriction cam-action knot for sleeping bags, compression, camping
« Reply #18 on: March 07, 2014, 11:55:02 PM »
OK, but then we have to throw in the sea the whole concept of this type of zip-tie-knots behavior, as it seem to me that in essence are the binders  shown by bushrag and Bjoern_Hee?You have recommended to bushrag  the use of a hitch,and well,OK,now I wonder which is that, in the case of this type of binder, permanently bends the standing part to 90 degrees...
I believe that this 90 degrees bending aids, and the Pretzel loop it is a sure proof of this, but it is not only this that keeps the tension: I saw that building the binder with the Locked Cow hitch positioned in the opposite direction with respect to the standing end,in this way the standing end is a little more bent, but the compression of the two diameters of rope wrapped by the Cow hitch component and the general tension of the binder seem inferior.
At the end, to keep a sleeping bag rolled up and similar tasks, this binder still does not seem to me a so bad solution...and anyway ...  now I go to play my mid-air/single string and note lyre,aware that you will think that I have just a very poor thing to amuse me...and maybe you are right!

                                                                                                       Bye!

xarax

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Re: Constriction cam-action knot for sleeping bags, compression, camping
« Reply #19 on: March 08, 2014, 02:27:27 AM »
I wonder which is that, in the case of this type of binder, permanently bends the standing part to 90 degrees...

  Me too !  :)
  I only imagine something similar to the two nubs of the Pretzel adjustable loops I have been referred to, combined and merged into one, where the one, now, nipping / constricting knot tied on the middle of the Stranding part can swallow, and keep firmly it its dents, two Tail Ends, coming from two eyes, at the end of the line.

the compression... seem inferior.

  Compression does not matter so much ! It is what is how one line is compressed on another. If the two lines are at a right angle, they bite each other, so each one is more able to inhibit the movement of the other. If they are at an acute angle, or parallel to each other, they tend to slide on each other - even a greater force and surface friction can not make the one line to sink deep in the other, and generate those saddle-like surfaces on the area of mutual contact which play the role of obstacles to any translational relative motion.

   Tie the one-returning-eye-leg binders I haver shown in this old post, and compare them.
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Dan_Lehman

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Re: Constriction cam-action knot for sleeping bags, compression, camping
« Reply #20 on: March 08, 2014, 08:53:28 AM »
Quote
I will tell it right from the beginning, and I will tell it once more at the end of my post :
  Do NOT use a fixed loop ! Replace the fixed loop with some other structure - simplify the mechanism !
With such an absolute, strong assertion such as this, ::)
one must consider the source, and it can be a good
guide : .:. a fixed eyeknot is just the simple answer
(or part of it) !!    ;)

An overhand eyeknot is one that pretty reliably
stays (simply) tied in common materials.  Make its
eye long enough to tie a 2nd, short-eye'd such knot
or perhaps the bulkier Ashley's stopper --for it will
be qua stopper that this knot will serve, to secure
some simply formed gripping hitch around the
binding tail.

One might, e.g., bring the tail around the object,
then turn the stopper-tipped eyeknot's eye around
this tail with a turn or two and then tuck the
stopper up through the eye legs, to lock it
!
Draw the tail through this gripping hitch, as desired.
One might then turn the tail around the stopper,
jamming it between knot and pinching eye legs.
[#20140308a00:11 series]

QED

(Sorta similar, mid-line-stopper-mechanics thinking
had me implementing a cleat in cordage w/two
stoppers --and this got "too clever by half" quickly,
but it was fun!   ;D )


--dl*
====

Bjoern_Hee

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Re: Constriction cam-action knot for sleeping bags, compression, camping
« Reply #21 on: March 12, 2014, 08:54:59 PM »
DerekSmith, that larks foot version is very nice indeed, and a lot stronger. On the other hand the nipping loop has that satisfying pop-open gimmick, so I'm not prepared to give it up.

Looking back over the thread, I think there is a whole set of fine knots. And they have now gone into my "knotting toolbox".

xarax, that ABoK 1669 was a nice find. It is interesting that knots, that are there in plain sight, can be so hard to find. The knotting world needs a set of systematic naming rules in the vein of the naming of molecules.

xarax

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Re: Constriction cam-action knot for sleeping bags, compression, camping
« Reply #22 on: March 12, 2014, 09:44:59 PM »
The knotting world needs a set of systematic naming rules in the vein of the naming of molecules.

+1 !
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DerekSmith

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Re: Constriction cam-action knot for sleeping bags, compression, camping
« Reply #23 on: March 12, 2014, 11:58:36 PM »
The knotting world needs a set of systematic naming rules in the vein of the naming of molecules.

+1 !

+2 !

Bjoern_Hee

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Re: Constriction cam-action knot for sleeping bags, compression, camping
« Reply #24 on: March 15, 2014, 05:48:35 PM »
Still another variant. This one has in my opinion a nice combination of strength and simplicity. It is still a cam-action bender, but not so readily untied. The knot will hold in mid-air.

This is what you do: Prepare the doubled string nipping loop. Let the two working ends enter the loop from each side, and tie them into a half knot. Tighten.

This is a knot I wouldn't teach to children.

The half knot part is essential for high strength. The mechanism is not so much nipping, but more like that of the lazy dog knot. Turns that immobilize a component of the knot, that would otherwise be weak or unstable.

In twisted rope it can be tied in four different ways. In non-twisted rope it can be tied in essentially two ways. I have just started experimenting, so I am still undecided about the best way. Though for twisted rope the half knot should probably follow the twisting. It seems that going against the twists introduces some roughness that interferes with tightening and loosening. The "nipping loop" turns should probably go against the half knot twists.

Adding an extra turn in the "nipping loop" makes the knot even stronger. The larks foot can be used instead of the "nipping loop". But in my testing it didn't improve strength in this knot, which I think is due to the change in the mechanism.

xarax

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Re: Constriction cam-action knot for sleeping bags, compression, camping
« Reply #25 on: March 15, 2014, 08:21:18 PM »
   Evidently, you do not read the posts suggested to you as references, neither you just spear a quick glance at the pictures shown there. To abstain from too much reading of what has already be done may be beneficial for a novice knot tyer, indeed, because our imagination needs freedom to make its first steps - this novice knot tyer, for one, has read a handful only of books on knots, and he was even postponing the reading of Ashley s BoK for as long as he could. However, in this Forum, when one member presents a particular knot, I believe that it is always useful to read what other people have said about it, or about other, "similar" knots, because, even in the vast KnotLand, around a particular point / knot, and within the limited, by the requirement of "similarity", range, there is always a limited area...

   Now, this knot you have tied is a two-coil Gleipnir binder, with crossed tails - a common trick we use to increase the entanglement of the Tail Ends before they exit the knot s nub. We do not know the optimum number of coils the nipping tube of this knot should have : two coils seem better than one, because, although the total nipping force is spread over a larger area ( so the two rims of the double nipping loop can not 'bite" the Tail ends as hard and deep as in the case of the one rim of a single nipping loop ), the segment of the double helix those Tail Ends form, as they are twisted around each other, clearly needs this longer nipping tube. However, a very long nipping tube may be unstable, and, if it is pulled from the "wrong" end a little more, it can rotate, and release its grip. I have tried the two- and the three- coils, but I have not been able to decide which is the better solution... The recently tied Gleipnir-like hitch and binder with a Prussic knot as its nipping tube, go as far as to use four coils - it becomes rock-solid as a hitch, but it may be too unstable as a binder.

    http://igkt.net/sm/index.php?topic=2981.msg17791#msg17791   
   
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Tex

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Re: Constriction cam-action knot for sleeping bags, compression, camping
« Reply #26 on: April 19, 2015, 03:19:53 PM »
Hi Bushrag,

Thanks for bringing us this lovely sliding grip hitch and starting off this thread of further innovation.  I so enjoy it when open minded knotters pick up on an idea and expand the theme from their different perspectives.  The Timber hitch variant for example is a lovely enhancement.

I don't know whether you realise it or not, but the twist you are using is in effect a single turn KC hitch (or if you prefer, the KC hitch is a multi turn nipping loop), which although it grips well, is not the most stable of gripping structures for rope or cordage.  By contrast, the other principle gripping structure, the Prussik is far more stable on rope, and you might consider using the 'Single turn Prussik' in this application.  Of course, the single turn Prussik also goes by the more common name of Larks Foot or Cow hitch



Instead of in your diagram putting the rhs loop over the lhs loop, simply fold the rhs loop under the lhs loop.  This single turn Prussik or Larks foot, is a much more stable gripping component, yet just as easy to make.  In fact, you can make the Timber hitch / Larks foot combo with one hand and just a few rotational wrist movements.

I am a total fan of the Gleipner, but this single strand variation has just become my favourite bundle binder with the timber hitch method of making the loop and the Larks Foot nip.

Keep 'em coming.

Derek


I ran into this old post and had to reply to this because I noticed something that's just too funny.  I don't know if DerekSmith is still around, but anyway...

If you put a lark's foot midline, run the working end around a structure and through the lark's foot can anyone guess what you get???

take 5 seconds to think about it..













... and the answer is... a square knot (sort of, well topologically at least it is a square knot).

So if you have a fixed loop and put a larks foot "nip" in it and bring the rope back around "like a trucker's hitch" you have.. a square knot with a backing knot on one side (whatever knot you used for the loop).  Of course tying it this way let's you use two hands to pull and even more importantly to secure the remaining free end, and this is mostly the real advantage that a trucker's hitch buys over a square knot actually.  If you tie it right you can get a similar mechanical advantage on the square knot, but only with one hand (and no feet) and it's hard to lock it in.

I should say though, that it's only sort of a square knot.  Tightened in this manner you will usually end up with something which behaves much more like a taut line hitch than a square knot (well it's a single/half prusik).  As such, even without the backing knot/loop, it can be tightened down well, but even with the backing knot, it is also less secure than a properly dressed square knot. 

So the question is, is a square knot still a square knot when it's a cow hitch tied around the other end of the rope (but still used as a binding knot)?





Tex

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Re: Constriction cam-action knot for sleeping bags, compression, camping
« Reply #27 on: April 19, 2015, 04:30:21 PM »
oh and there's a quick and dirty way to bypass tying the loop, just bring both ends of what would be the loop back around the object together and through the hitch.  Then you have a double ring hitch used as a binder.  You gain back ability to use two hands without tying a loop, but anyway, the cow hitch eats up all the mechanical advantage.  As far I can tell you just get an intentionally insecure binding knot that's pretty easy to tie and doesn't get that tight, which is the same as a shoelace "bow" except the shoelace bow is pretty secure. 



« Last Edit: April 19, 2015, 04:30:59 PM by Tex »

DerekSmith

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Re: Constriction cam-action knot for sleeping bags, compression, camping
« Reply #28 on: April 23, 2015, 06:42:23 PM »

   Now, this knot you have tied is a two-coil Gleipnir binder, with crossed tails - a common trick we use to increase the entanglement of the Tail Ends before they exit the knot s nub.

    http://igkt.net/sm/index.php?topic=2981.msg17791#msg17791   
   

Hi Xarax,

Are you sure that this is a Gleipnir?

It is a bit of a job telling from the top photo, but to me it does not look as though the ends approach from opposite directions as they would in hte Gleipnir.

Rather, they seem to come from the same side.

Have a closer look and see what you think.

Derek

xarax

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Re: Constriction cam-action knot for sleeping bags, compression, camping
« Reply #29 on: April 23, 2015, 11:15:42 PM »
...it does not look as though the ends approach from opposite directions as they would in the Gleipnir.

  Appearances are deceptive !  :) :)
  No, they do - as you point out, in a Gleipnir, we have a mid-air nipping structure ( be it a single, double or even triple nipping turn - as here (*)-, but also a single or double overhand knot (1), or even a Clove or a Constrictor hitch, or a Prusik (2) )(*)
   AND we have two penetrating this structure Tail Ends, entering/exiting to/from it, from opposite directions (0).

   I tend to believe that the most characteristic feature of a Gleipnir-like binder is that the ends ... enter into the nipping nub through opposite openings. This is paramount in achieving a "balance" of the nipping loop, and not allowing it to revolve around itself, and release its content

0. http://igkt.net/sm/index.php?topic=5014.0
1. http://igkt.net/sm/index.php?topic=4818.0   
2. http://igkt.net/sm/index.php?topic=4821.msg31447#msg31447

   numbers, and see which end is connected with which, and where it goes.

  I have marked the ends of the lines shown in the picture of the loose knot with numbers, so it will be easy to follow the
(*) More than three turns make the nipping "tube" too long - and the knot unstable :
    http://igkt.net/sm/index.php?topic=4821.msg31429#msg31429

(*) Perhaps the root of the misunderstanding was this word, "approaching". It does not matter how the ends travel outside the nipping structure ( which in this case, is a three turn coil ), and from which direction they "approach" it. The only thing that matters is how they travel inside it. If they travel pointing towards opposite directions, the binder is Gleipnir-like.
In the picture of the binder you had cited, the Tail ends which penetrate the nipping structure and they are locked, and immobilized, by its gripping, travel inside the nub towards opposite directions.   
« Last Edit: April 27, 2015, 09:03:16 PM by xarax »
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