Adjustable Loops

[alanleeknots]

Xarax, Thanks you very much.

 謝謝  alan lee

[alanleeknots]

Hi All,
       So far I see most of the simple adjustable loop, either hard to deal with or just can't handed heavy load.
       I may be wrong, unless someone show me if there is a simple adjustable loop can support heavy load. and easy to adjust the loop.

       Here I modifly the Double overhand knot-based adjustable loop little bit, and now it can support heavy load.
       eventhough is a PET loop and little more complicate to tie, but it can support heavy load and easy to adjust the loop.

       Here are some of my simple test, just a rough idea what the knot can do.
       First test, I loaded it heavy untill the Double overhand knot-based adjustable loop just start to jam.
       after the loading, the Double overhand knot-based adjustable loop,I have hard time to untie it,
       but the other one just supper easy  to untie.
       Second test, do the thing as above, have the same result.
       Third test, same loop both end, pull till it broken. and it is supper easy to untie.
       Forth test, I apply load untill I notice it just jam hard.after the loading, this loop need tool to untie it. 

       謝謝  alan lee

[xarax]

    So far I see most of the simple adjustable loop are either hard to deal with, or just can't hand heavy load.
    I may be wrong, unless someone shows me if there is a simple adjustable loop which can support heavy load and it is easy to adjust the loop.

    That would had been expected. In easily adjustable loop the continuation of the returning eyeleg has to follow a not-very-convoluted path, otherwise we would not be able to pull it, and re-adjust its length. To immobilize a line like this, you need a very strong nip / grip, so you run the danger of a jamming nub...
    THAT is what we are searching ! A simple adjustable loop ( which, BECAUSE it would be simple, it would also be tight - no tension wasted between many internal turns...) which can support an as heavy load as possible, and also would not jam.

    I ask you only one thing : With those nubs which you find hard or impossible to untie, have you used the trick, to PUSH an end INWARDS, to feed the nub with more material, and so loosen it ? Of course, this is possible only with stiff, in the lengthwise sense, ropes. The ropes I use are climbing ropes, and so they are stiff : you can push one end, and they tend to be translated lengthwise like they were solid rods.

   Continue your FINE work ! There may be many non-jamming yet secure adjustable loops out there !

[xarax]

   On solid braided nylon rope ( which can be elongated a lot, and which is not stiff at all, so it can not be pushed by an end...), the loops I had tied are very difficult to untie, indeed. On climbing ropes, and especially on some very slippery yet stiff(lengthwise) cannyoning ones, they are much easier.
   The very important thing I want to tell you, is something I told you already, but perhaps you have not noticed :
   You have to use a FREE REVOLVING rigid element, around which you will wrap the eye of the loop, to simulate the most common situations, where the encircled object is free to rotate around itself into the loop. This way, the tension on the eyelegs is almost equal, 50% of the load. When you do this, you will see that the nubs of some loops settle to another orientation, and the angle between the L-shaped "handle" and the axis of the loop becomes different.
   Wrap the eyelegs around a free rotating pulley, or a simple bearing.

[xarax]

   There is a trade-off between, on the one hand, the number of turns of the nipping / gripping knot ( double, triple, quadruple loop ) and the angle of the L-shaped "handle" ( with more turns, the angle gets smaller than 90 degrees ), and, on the other,  the easiness with which the loop can be adjusted. I had tried the triple overhand knot, and the quadruple overhand knot, but in them this angle seemed to me to become too small, much smaller than I would had wished - so the loop becomes difficult to adjust. I have to repeat that we wish to be able to adjust the loop even under some light loading - a completely unloaded loop can be adjusted even if the continuation of the returning eyeleg follows a much more convoluted path, but then to adjust the ( length of the ) eyeleg, we will need to pull it twice, the first time from the tip of the curve the "handle" makes, and the second time from its end.
   Now, it was expected that a triple-overhand knot based gripping / nipping nub would be more easy to untie - because it is more convoluted, and, because of this, it is less tight. We have to choose between a more tight nub ( based on the double overhand knot ), and a less tight, but easier to untie one ( based on the triple or on the quadruple overhand knot ). And, as I said before, this decision by us should take into account the material we use ( a softer, more compressible, easier to be "flattened" material leads to more difficult to untie nubs ), the existence or not of some load during the adjusting stage, and what risk of jamming we are prepared to accept, in order to have an easily adjustable, yet most secure nub.
   Alan, if you want to use the triple overhand knot, pass the Tail End the way I show. Doing this, the knot becomes self-dressing, and the two segments of the rope inside the "nipping tube" can not swap positions. If you find that even this nub is not so secure as you wish, do the same thing with a quadruple overhand knot.

   P.S.
   All those loops are implementations of the idea described at :
   http://igkt.net/sm/index.php?topic=2996.msg17836#msg17836

[alanleeknots]

Hi All,
        Xarax, Thanks you very much for your comments,
        Here are few simple test on you loop, It is very nice , very easy to untie too.

         謝謝  alan lee

[alanleeknots]

Hi All,
        Mr. roo have present the HFP Slippery 8 Loop earlier, 
        see here reply #1  http://igkt.net/sm/index.php?topic=5322.0
        beside this one, I found another one here can support heavy load.

        Never mind whether it can be an adjustable loop or not. just come here for  knot Explorations.

        Beside this, I have few more loops posted it where it belong to.
        see reply #87  http://igkt.net/sm/index.php?topic=5383.75

             謝謝  alan lee

[xarax]

   Never mind whether it can be an adjustable loop or not.

   I do ! Fixed loops belong to another class of loops - when I want a fixed loop, I start from the king of knots, the bowline... because it is great that this loop is PET, too, and so the knot tied on the Standing Part before the eye is not an overhand knot or a fig.8 knot, and so it can be easily untied. No end-of-line loop is as simple, as secure and as easily untied ( and in on, only, step ) as a bowline.
   It is only with the (easily) adjustable loops that we are ready to accept some difficulty in untying, or even some danger of jamming. The David Poston s loop is very secure, but can not be untied after a heavy loading as easily as the bowline ! And it can not be adjusted much easier than a common bowline - so I am not sure we can say it is an "adjustable loop" at all. The continuation of the returning / second eyeleg makes an almost 180 degree U-turn, so we can say that it follows a turn similar to the turn of the bowline s collar, and the fig.8 knot  tied on the Standing Part before the eye plays the role of a nipping structure, similar to the nipping structure of the secure bowlines ( yet not as easily untied ).
   I believe that the key to the concept of the "adjustable" loops is the angle of the "handle", the angle between the direction of the returning eyeleg and the direction of the Tail End. If it is near 90 degrees, the size of the loop s eye can be adjusted easily, even under some tension. If it is much less, the loop is not very secure, and can not withstand heavy loading. If it is much more, the loop becomes very secure, but can not be adjusted easily any more - and it can not be adjusted at all even under light, only, loading : a 180 degrees angle, a 180 degrees turn of the "handle", works like the bowline s collar : with the help of a nipping structure ( whatever nipping structure ...) , it immobilizes the returning eyeleg completely, and does not allow any easy and quick adjustment, and no adjustment at all under some load.
   To design a loop where the angle of the "handle" remains at around 90 degrees is not easy : the balance between an insecure adjustable loop and a fixed loop is delicate. The Dave Poston s loop should be compared to the common ( or the double bowline, because the fig.8-knot-based nipping structure is a "double" one ), not to the really (easily, and even some tension ) adjustable loops. 

[xarax]

   We may ask : is the L-shaped "handle" the only form the continuation of the returning eyelrg can have as it enters into and exits from the nipping structure, in order to enable an easy adjustibility of the loop ?
   I have also tried the solution offered by the "Helical loops", where the returning eyeleg traces a helical path around a knot tied on the Standing Part before the eye. If the helix formed this way is not too long, it can be easiy adjusted ( but not under any load... ). Therefore the most simple "Helical loops" can be considered as a kind of "adjustable loops", indeed.
    We can also envison a loop where the continuation of the returning eyeleg can follow an S-shaped path : from straight "below" and parallel to the exis of the knot, when it goes "upwards", it turns left, then turns right, then turns left, then turns right again (or the other way around ), and then exits from the nub again parallel, or almost parallel, to the axis of the knot. In other words, where the continuation of the eyeleg is immobilized in a way similar to the way it is immobilized in the mechanical belay devices known by climbers as "racks" (1). I do not know any reliable and easily adjustable loop based on this principle.

1. http://storrick.cnc.net/VerticalDevicesPage/Rappel/JRacks.html
2. http://storrick.cnc.net/VerticalDevicesPage/Rappel/URacks.html

[Mobius]

This thread turned into a thread about "adjustable loops".

Those who posted about the original "knot wars" or later the suggested name change to  "Load testing of various Bowline structures" theme need not worry. I will post something in a new thread that verifies that I have acknowledged your input. I still have it mind to do the trials (as modified by reader input) I suggested in the first place.

Holidays and time to do all this (hopefully) is not far away for me

Cheers,

mobius

[xarax]

   Perhaps the Moderators can remove the posts about various "adjustable loops", into another proper thread ? ?

[Mobius]

   Perhaps the Moderators can remove the posts about various "adjustable loops", into another proper thread ? ?

Yes indeed, that would be nice. I would like to add input to a dedicated "adjustable loops" thread that I have held off adding here.

Cheers,

mobius.

[alanleeknots]

Hi All,
        Xarax, Mobius, yes it turn into adjustable loop, I felt the same way, we should do something about it.
        I suggest may be Mobius you can start a new tread just for "knots war" and left this thread alone.
        If we take away some of the reply, may make it very confuse to the reader, because all the reply is connected to one or another.
        we can change the name of this thread to what ever.
        Let  me start a new thread just for "adjustable loop"  we can gather all the adjustable loops put in one spots first, and then we test
        all of them, see if we can find any adjustable loop can be practical.

        謝謝  alan lee
               

[alanleeknots]

Hi All,
        I have another loop here, it is difference kind knot, You have to dress the loop in a very odd way
        and the nipping loop have a difference way to secure the loop.

        謝謝  alan lee.

[xarax]

   You utilize the fig.8 knot just as SS369 utilized the fig.9 knots :
   http://igkt.net/sm/index.php?topic=4965.0
   The problem with those knots is that they should be dressed carefully, otherwise the continuation of the returning eyeleg will follow a slightly different path, where it would be less well nipped, and more straightened ( so, the angle of the "handle" will be even smaller ).
   If you decide to tie a fig.8 knot on the Standing Part before the eye, I believe you have no reason not to tie the David Poston s very secure loop - or even the fig.8-based less-easily-adjustable but TIB loop, shown at :
   http://igkt.net/sm/index.php?topic=5357.msg36146#msg36146