Author Topic: New hitch?  (Read 30047 times)

richardpeterson

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Re: New hitch?
« Reply #15 on: February 28, 2012, 04:06:15 PM »
Just to be clear - the "surgical tubing" I'm referring to is latex tubing about 3/8" outside diameter.

Picture:
http://www.lpimg.info/Image/Product/Large/DIV2012.JPG

Brief overview:
http://www.ehow.com/list_6406549_uses-surgical-tubing.html

It is apparently popular among divers, although I have no experience with this. I suspect that most applications either use pure binding knots (for instance, for a tourniquet) or pull up knots by wetting them, which I very much want to avoid.

SS369

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Re: New hitch?
« Reply #16 on: February 28, 2012, 04:11:36 PM »
For you xarax and anyone else who has a challenge viewing the Google books page. A screen capture.

xarax

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Re: New hitch?
« Reply #17 on: February 28, 2012, 04:21:27 PM »
   So, this material is not only elastic lengthwise, but also tubular , AND, as I learn now, other times it slips badly and other times it tends to stick to itself !  :) :) I wonder how much more peculiar a material can be... to make the life of a knot tyer difficult ! I guess it can also fold inside out, as a glove... and one segment of it can be inserted inside the other, ( i.e., be coaxial to another), so we end up having a double-skin tube. I believe that the knots made by this material belong to an altogether different world than the knots made by common material, and we should not try to solve problems originated in the one with solutions given in the other.
« Last Edit: February 28, 2012, 04:42:03 PM by xarax »
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richardpeterson

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Re: New hitch?
« Reply #18 on: February 28, 2012, 04:25:45 PM »
Regarding the Ossel Knot SS369 suggested.

Xarax - maybe the following link will work?  http://www.scribd.com/doc/7227304/Handbook-of-Knots-Splices   Scroll to page 34 in the actual text, which is shown as page 32 in the program - or search for "ossel knot".

I don't have my tubing with me - I'll try this when I get home.  Making tucks can be somewhat cumbersome in some configurations with surgical tubing. Depending on the length and tension of the section you need to lift up, it may be hard to lift it to make the tuck. That, and it tends to stick to itself. So I'm not sure if making the three tucks in the ossel knot will be cumbersome, or will just serve to improve security.

The properties of the tubing are a bit baffling to me. It sticks to itself fiercely at times, making it difficult to work with. At other times, it slips badly, making trustworthy knots fail. I haven't quite figured it out, but I think its grippiness and slipperyness may be factors of the tension on the line.

Sweeney

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Re: New hitch?
« Reply #19 on: February 28, 2012, 04:26:56 PM »
   Thanks, SS369, but all I see here is a nice brown front cover...The link does not work in my computer... Is there anywhere else I can see those figures/pictures, or they are top-secret ?  :)

Here is a picture of the Ossel Hitch http://en.wikipedia.org/wiki/Ossel_hitch and a video showing the Ossel Knot (the commentary about this being used to tow a net may be right but it was not the main purpose). http://www.youtube.com/watch?v=sqCC9okfzd4

Barry
« Last Edit: February 28, 2012, 04:29:59 PM by Sweeney »

richardpeterson

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Re: New hitch?
« Reply #20 on: February 28, 2012, 04:32:20 PM »
Roo:
Thanks for the suggestions.

A stopper knot will stay in this tubing if the knot is wet. Perhaps I could prep the tube with a tight stopper knot on either end, pulled up when wet, and just leave those knots in permanently. Then any hitch made in the field would be more likely to stay fast.

The rope bent in the ends is also a great idea. I can't wait to try these when I get home.

Sweeney

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Re: New hitch?
« Reply #21 on: February 28, 2012, 04:38:45 PM »
For you xarax and anyone else who has a challenge viewing the Google books page. A screen capture.

The picture of an Ossel Knot is wrong (and doesn't agree with the narrative on the page anyway!). The final tuck goes under one part only not the whole set of wraps.

Barry

richardpeterson

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Re: New hitch?
« Reply #22 on: February 28, 2012, 05:02:25 PM »
Quote
So, this material is not only elastic lengthwise, but also tubular , AND, as I learn now, other times it slips badly and other times it tends to stick to itself !  :) :) I wonder how much more peculiar a material can be... to make the life of a knot tyer difficult ! I guess it can also fold inside out, as a glove... and one segment of it can be inserted inside the other, ( i.e., be coaxial to another), so we end up having a double-skin tube. I believe that the knots made by this material belong to an altogether different world than the knots made by common material, and we should not try to solve problems originated in the one with solutions given in the other.
Yes, it is quite peculiar and contrary stuff. I think knots are an appropriate tool to help make use of it - especially if the behavior of knots in tubing is well understood. I find it quite interesting to probe at the boundaries of the utility of knots in various materials, if anything to avoid overconfidence.

I'm looking forward to trying a few more of the suggestions put forth in this thread. I don't know any more scientific method of testing their security than my informal battery of twisting, swinging, bouncing, yanking and otherwise vigorously loading the standing end. However, I would be happy to post the results of my informal testing as I try all your suggestions. I should probably begin taking notes.

So far, I have not been able to make the modified ossel hitch - the original hitch I posted - fail in surgical tubing. I have been able to get every other simpler knot I've tried to fail.


xarax

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Re: New hitch?
« Reply #23 on: February 28, 2012, 05:52:42 PM »
I find it quite interesting to probe at the boundaries of the utility of knots in various materials, if anything to avoid overconfidence.

 Another client of the "material matters" product !   :)
 While, of course, this is true, it should not drive us to the wild side, where anything goes, there are no knots but only "knotted materials", there are no natural laws but only constructs of the human intellect, and we can not speak about anything - but we have to remain silent...There are many more things in knots that remain the same, that do not depend upon the specific circumstances and materials - and we can speak about knots, in general, because those things exist.
  Having said that, I have to admit that if something is on the borders of the knotting world, this is a knot tied with/on this material. So, if you really wish to kill a knot tyer, to make him commit suicide, all you nedd is to present him a problem that should be solved with this material !  :)
  There was a thread where we tried to define what a rope and a knot is (1). I have to say that I, for one, have deliberately left knots tied on/with such materials outside the realm of definition - because I knew what strange animal is such an object... Imagine that the latex is replaced by a more elastic substance, and then by an even more elastic one...Where do we stop ? Will the objects constructed with the help of tangles made by this super-elastic tubular material bear any resemblance with a knot ? Are tangled elastic 2D toroidal membranes, following convoluted paths in 3D space, "knots"? 
 
I have been able to get every other simpler knot I've tried to fail.

Why am I not surprised ?  :) You would have had more success with boiled spaghetti, I guess.  :)

( I am too old to start learning new tricks, with this material. I have decided to limit my involvement in the few brief moments the nurse ties my arm with this thing, to find the vein... :)

1)  http://igkt.net/sm/index.php?topic=3610.msg20611#msg20611
This is not a knot.

knot4u

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Re: New hitch?
« Reply #24 on: February 28, 2012, 07:07:14 PM »
Fundamental questions...

Is OK to jam the knot?
Does surgical tubing jam well?

I think you mentioned the contraption is sometimes sent home with the customer with the knot in place. In that case, I'd want the knot to jam.

richardpeterson

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Re: New hitch?
« Reply #25 on: February 28, 2012, 07:09:13 PM »
Xarax:
I certainly don't want to burden this "Practical Knots" forum with tangential or inappropriate topics

The way I figure, this surgical tubing is in somewhat popular use, and people insist on bending it to various items in the course of their work.  I'm interested in finding out how safely, easily and reliably they can accomplish their goals. Or, as the case may be, that they can't make a reliable knot.

I want to know regarding this tubing - can it be knotted or otherwise made fast to something? If so, how?

After a bit of experimentation and thought, I found that the proposed hitch - the modified ossel - seems to hold quite securely (I'm still anxious to test it in bungee and watch it fail). Several of the other knots, put forth in this thread - the slipped modified buntline and gnat hitch and I'm sure others that I haven't had the chance to test - have proven secure, although they were a bit awkward for me to tie.

Since surgical tubing seems to be a knottable (if a bit contrary) material, I think this is all a useful pursuit.

I intend to do some more testing with the knots proposed, and report back.

richardpeterson

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Re: New hitch?
« Reply #26 on: February 28, 2012, 07:22:13 PM »
Quote
Is OK to jam the knot?
Does surgical tubing jam well?

I think you mentioned the contraption is sometimes sent home with the customer with the knot in place. In that case, I'd want the knot to jam.

It should not jam. A plain length of tubing about two meters long is sent home with the patient, and they are left to fend for themselves as they bend it to handrails, posts, and other household items as they set up their own space to do their exercises. Physical therapists also may tie the tubing in a patient's home and leave it.

It shouldn't jam, because sometimes it is only left for one exercise session, and then removed.

Surgical tubing may be difficult to untie at times, but the only way I've seen it actually jam is when it is wet and pulled up tight. Then it behaves a bit like monofilament. That's one reason I'm trying to avoid knots that only work when pulled up wet. Almost any usually reliable knot will behave quite well in surgical tubing when you wet the tubing and pull it up tight. They just tend to jam.

If jamming is not a concern for someone knotting surgical tubing, wetting the knot and pulling it up quite tight seems to yield very reliable and secure knots.

knot4u

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Re: New hitch?
« Reply #27 on: February 28, 2012, 07:36:26 PM »
Different application probably...

My memory is coming back to me now. I've had to use surgical tubing for physical therapy before.

I guess the knot here depends greatly on the exercise.  Common exercises in tubing involve pulling a band with a foot or hand. In my physical therapy I had to do reverse calf raises to strengthen the muscles in front or my legs, like in the pic below.

In that case, I would jam a sling in the tubing for the patient, and then show them how to tie a Cow Hitch (and maybe even a Prusik) around an anchor. The Cow Hitch would obviously not jam for this application. I mention this because I often find myself overlooking simpler, more elegant solutions. Again, your applications are probably different (?).

« Last Edit: March 03, 2012, 02:58:25 AM by knot4u »

roo

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Re: New hitch?
« Reply #28 on: February 28, 2012, 07:41:59 PM »
In that case, I would jam a sling in the tubing for the patient, and then show them how to tie a Cow Hitch (or maybe even a Bull) around an anchor. The Cow Hitch would not jam for this application. I mention this because I often find myself overlooking simpler, more elegant solutions. Again, your applications are probably different (?).
I was considering this until he mentioned the issue of some hitches stretching away from the bar and allowing lengthwise rolling.  Perhaps a Prusik or Klemheist would help reduce this tendency.  The latter would be easier to make.

This approach would obviously halve the elasticity of the system, though.
« Last Edit: February 29, 2012, 01:03:49 AM by roo »
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Hrungnir

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Re: New hitch?
« Reply #29 on: February 29, 2012, 12:27:34 AM »
Quote from: richardpeterson link=topic=3805.msg22435#msg22435
It should not jam. A plain length of tubing about two meters long is sent home with the patient, and they are left to fend for themselves as they bend it to handrails, posts, and other household items as they set up their own space to do their exercises. Physical therapists also may tie the tubing in a patient's home and leave it.

It shouldn't jam, because sometimes it is only left for one exercise session, and then removed.
As I've mentioned before, I've done and do strength training with rubber bands. I assume these rubber bands can take a lot heavier loading than medical tubing, and I've successfully used the Slipped Sheetbend for this task. Sheetbend is a very easy not to learn, easy to tie simple to tie, is easy to untie and has the slipped version for being untied even more easily, which is important when dealing with elastic materials.

I would also give a thumb up for Knot4us suggestion about the cow hitch. Easy to learn, hard to do wrong, quick and simple to tie and easy to untie.

The Fist Hitch as suggested in the original post, outperforms many of the suggested knots  in the mentioned criteria, so it wouldn't be a bad alternative at all. Tripling it around the object, would perhaps be a bad alternative if the patient was going to hitch it around a large object such as a tree trunk.