Author Topic: Adjustable Loops  (Read 51120 times)

alanleeknots

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Re: Load testing of various Bowline structures
« Reply #135 on: August 08, 2015, 08:27:22 AM »
 Hi All,
        Xarax Thanks for your reply, I have the load test here, it is a rock solid well secure loop, and very easy to untie.
        Part of top coil will slowly jam into the bottom coil as the load increase, there is nothing loose in the nob.
        In order to have a nicer main collar, When we load the loop, we may have to hold some tension on the tail till the
        nipping force get hold of the tail.(because this nipping force are little slow to reach to the tail).

           謝謝  alan lee

alanleeknots

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Re: Load testing of various Bowline structures
« Reply #136 on: August 08, 2015, 08:31:45 AM »
load test photo.

xarax

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Re: Load testing of various Bowline structures
« Reply #137 on: August 08, 2015, 09:02:47 AM »
   Indeed, I see in your pictures that the diameters of the two coils are equal, which means that there remains no slack in the nub. I had not loaded your loop so much, and that is why the second / higher collar remained more loose.
   However, I still believe this second collar is an overkill. We use two collars when we want the friction between their parallel and adjacent wraps to keep them "locked" - but here you have the nipping loop itself to do this. I do not believe that two collars grip / nip / immobilize a penetrating line more than a single one ( and, in any case, such an effect, if it exists, it has not been demonstrated by any test, ever ) - because one single collar "bites" harder into the surface of the line, but two, although they provide a more extended area of contact, they also provide a more extended area on which a line can slide, because they can not penetrate into its surface so deep.
   I think that if you tie the much simpler knot I had shown in my previous post ( with the vertically oriented coil, which is loaded more directly by the returning/second eyeleg ) you will see that it is no less tight and secure, although it uses one, only, collar. 
« Last Edit: August 08, 2015, 09:06:02 AM by xarax »
This is not a knot.

xarax

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Re: Load testing of various Bowline structures
« Reply #138 on: August 10, 2015, 01:06:26 PM »
   On the other hand, anything hanging from the rim of the nipping loop ( like this/those turns on the returning/second eyeleg, before the collar ) tends to pull the nipping loop wide open - so, perhaps, what this eyeleg gains, regarding friction, in its way "up, it loses it in its way "down" - because the "loaded" nipping loop may not be able to nip it as tightly as when it was left undisturbed...
This is not a knot.

Mobius

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Re: Load testing of various Bowline structures
« Reply #139 on: September 23, 2015, 01:24:02 PM »
This thread started life as a fun 'knot wars' idea.

Later it metamorphosed into a thread about adjustable loops :)

For several weeks I was not around here so that didn't help much either. At some stage I will try and pull the bones out of it and do something along the lines of what I intended. My new test rig is both good and bad, I can test much bigger loads, however the finer detail of when a knot breaks (i.e. what %mbs) disappears in the press of a button.

Where a knot breaks is more interesting anyway perhaps, and is not so much to do with the 2 diam vs 3 diam debate from what I have seen.

Cheers,

mobius

alanleeknots

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Re: Load testing of various Bowline structures
« Reply #140 on: September 25, 2015, 02:18:56 AM »
唯恐天下不亂嗎?
« Last Edit: September 25, 2015, 02:24:20 AM by eric22 »

Mobius

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Re: Load testing of various Bowline structures
« Reply #141 on: September 26, 2015, 08:21:37 AM »
唯恐天下不亂嗎?

Hi Alan,

If that was a question for me, in Chinese doesn't help me much answering it ;D

Cheers,

mobius

Mobius

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Re: Adjustable Loops
« Reply #142 on: September 27, 2015, 09:31:20 AM »
From another thread:

Hi all,
        Mobius, when I present the Triple overhand knot-based adjustable loop
        at Reply #92   http://igkt.net/sm/index.php?topic=5383.90.
        I have tie another version of Double overhand knot-based adjustable loop, I didn't post it because it will jam on heavy load.
        I have the load test here to show the difference between your version and my version.

        Picture #3 and #4, I loaded it till your SP-Tail Reversed loop just start to jam and I release the load to check on both loop,
        your  SP-Tail Reversed loop just kind of hard but manage to untie, but my loop is very easy to untie.

        謝謝  alan lee

Thanks, I was almost sure the knot I came up with was one I had seen before.... one of yours :)

Is the 'Triple overhand knot-based adjustable loop' the best one you found? If not, what was better?

I played some more with the Double overhand style loop you first showed us and added a second collar. The collar is more about introducing a 3rd diam through the turNip to see if that lessened the double overhands jamming potential while still allowing enough nip. Here is what I found happened:

Image 1 left: A simple double overhand double collar which slips, so reject this one. The 3rd diam did not look promising

Image 1 right: The tail is tucked in one of several possible ways. The knot tails loads to an 'L' shape at 500kg and didn't jam. However the collar closest the eye was too loose for my liking so I reject this one too. The 3rd diam. idea seems to work better this time

Image 2: Another try at re-tucking the tail. The tail becomes an 'L' under load

Image 3: Under load at 500kg. It untied easily in my rope (messed up the focus a bit, sorry). There are no loose bits in the nub, the collars and other loops are doing something load wise and nub form looks good to me. The 3rd diam through the turNip need not be dismissed it seems.

Seen any of these double overhand adjustable loops before Alan? The last one looks ok, what do you think?

Cheers,

mobius

Edit: added a 4th Image, much better focus of the same knot as Image 3 at 500kg
« Last Edit: September 27, 2015, 10:48:04 AM by mobius »

alanleeknots

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Re: Adjustable Loops
« Reply #143 on: September 28, 2015, 06:03:59 AM »
Hi All,
         Mobius Thank you very much for fixing the thread problem. Since you ask me about you knot, and I owe you a favour.
        I try my best to answer you. The additional collar will lengthen the collar near the standing part
        and also the three rope diameter on the nipping loop can push the main collar more upward,
        that mean we have a nice main collar and easy to untie.
        Now the main collar is fine, but there is a problem, additional collar will lock on the the nipping loop.
        When you load the loop,for softer rope it will lock on early, for stiffer rope can hold better, but it will jam on heavy load.
        unless you dress the additional collar loosely,then it will not jam on you.
        My own opinion any good knots should dress it as tight as you can before you use.
           謝謝  alan lee.
« Last Edit: September 28, 2015, 06:05:32 AM by eric22 »

Mobius

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Re: Adjustable Loops
« Reply #144 on: September 28, 2015, 06:56:54 AM »
Hi All,
         Mobius Thank you very much for fixing the thread problem. Since you ask me about you knot, and I owe you a favour.
        I try my best to answer you. The additional collar will lengthen the collar near the standing part
        and also the three rope diameter on the nipping loop can push the main collar more upward,
        that mean we have a nice main collar and easy to untie.
        Now the main collar is fine, but there is a problem, additional collar will lock on the the nipping loop.
        When you load the loop,for softer rope it will lock on early, for stiffer rope can hold better, but it will jam on heavy load.
        unless you dress the additional collar loosely,then it will not jam on you.
        My own opinion any good knots should dress it as tight as you can before you use.
           謝謝  alan lee.

Thanks for the feedback. I will try my double collar knot (the last one shown) in both my 3mm poly braid and 6mm marine grade pe/pp blend and see if it jams. The 3mm poly braid I use likes to jam (it's size makes it hard to untie even if it is smooth and stiff) and so does the frictive surface of the 6mm marine 3ply (very stiff). I don't test in soft rope, so lots of knots would jam in softer rope that otherwise would not in stiffer rope I suppose.

We may need different knots for different ropes, especially when it comes to adjustable loops.

Cheers,

mobius.
« Last Edit: September 28, 2015, 08:48:17 AM by mobius »

alanleeknots

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Re: Adjustable Loops
« Reply #145 on: September 28, 2015, 08:22:36 AM »
Hi All,
        Yes or no,  knots would jam in softer rope that otherwise would not in stiffer rope,  knots also would jam in stiffer rope
         that otherwise would not in softer rope.

         謝謝  alan lee.

Mobius

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Re: Adjustable Loops
« Reply #146 on: September 29, 2015, 12:32:16 PM »
Just to follow up on what I said I would do. Below are some 'other material' trial images of the double overhand, double collar adjustable loop I proposed earlier.

It actually works far better than I thought it would when I first started playing with it. That the 3 diams allow the turNip to hold as well as it does was a surprise. Then I was pretty sure Alan would be right and the eye collar would jam once I got it under heavy relative load (50% mbs) rather than the 500kg (20% mbs) load I tried before. However, the knot still looks very good to me: Doesn't slip, doesn't jam, doesn't deform under load.

The 3mm poly I use is shown at >100kg and the 6mm pe/pp is >300kg. Both images 2 & 3 show the knots were tight. I could get both knots apart by hand after these loads with relative ease. The collar closest the eye was the hardest to loose (as Alan said it would be), however I still think the knots were what I consider as being 'easy to untie'.

I have some reasons why this DODC Loop seems to work as well as it does, however those can wait for now.

Cheers,

mobius
« Last Edit: September 29, 2015, 12:37:01 PM by mobius »

alanleeknots

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Re: Adjustable Loops
« Reply #147 on: September 30, 2015, 08:05:02 AM »
Hi All,
         Mobius, let said we have a standard bowline here, we add one or two tuck or may be a second collar to the nub, by doing that,
         we have to gain something, have to be better then the standard bowline, otherwise it don't make sense to have though those unnecessarily
         parts add in to the nub. Any way I like your effort.
         謝謝  alan lee
« Last Edit: October 01, 2015, 08:22:02 PM by eric22 »

alanleeknots

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Re: Adjustable Loops
« Reply #148 on: January 06, 2016, 10:01:12 AM »
Hi All,
       Happy New Year
       Here is another variation of loop that belong to the same class and I didn't post it the last time,
       see here reply #128  http://igkt.net/sm/index.php?topic=5383.120 , because the last three loops their rope flow in to the nub are smooth
       then this one here.
       Now I have more free time to look at it again,I think this loop is not that bad at all. this loop is well secure and easy to untie,
       and the tail of this loop was nipped by the top collar with full force, make it little more secure.
       It is important have the last defend as Xarax alway said.
       
       謝謝  alan lee
« Last Edit: January 06, 2016, 10:02:41 AM by eric22 »

Dan_Lehman

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Re: Adjustable Loops
« Reply #149 on: January 06, 2016, 05:26:09 PM »
Just to follow up on what I said I would do. Below are some 'other material' trial images of the double overhand, double collar adjustable loop I proposed earlier.

Heinz Prohaska proposed using the anchor bend structure
qua eye-knot base some decades back, in response to the
infamous Lynn-Hill accident (where she was distracted from
tying in and simply didn't tie her intended (per her book)
bowline, but which some (mis)took as the case where
a left-in-rope-for-next-tying fig.8 (single-strand, SPart)
awaited the new tyer-in person's "rethreading" to complete).
So <whew>, Heinz thought that this base is one that could
work even if only the first tucking-tail-into-knot was done
and nothing further!
(IMO, that is fine-tuning an error point to a too-small range.)

Perhaps if the additional loop around the SPart is made
away from the eye --so that it will press into the other--,
jamming will not occur (or as much) ?!


--dl*
====