Author Topic: Possible new tape knot  (Read 2854 times)

Bjoern_Hee

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Possible new tape knot
« on: February 23, 2014, 06:43:00 PM »
Here is a knot for bending two tapes together (tape, webbing, strap... I am not sure what the right terminology is).

(fishermans_tape_knot.01.jpg)

Note that the brown tape start out by bending away from the grey tape.

(fishermans_tape_knot.02.jpg)

(fishermans_tape_knot.03.jpg)

(fishermans_tape_knot.04.jpg)

What I think is nice about this knot is that the two tapes can lie flat on a surface and be in a straight line. It is also a very easy knot to tie.

It is debatable though whether it is a new knot. You could view it as a fisherman's knot, tied in tape and dressed in a special way. New knot or not? You'll be the judge.

I have searched the internet and knot litterature for this knot/dressing, but couldn't find it. I guess that the "backflip overhand knot", starting by bending away from what it is tied around, is counterintuitive, and the reason my search didn't turn up anything.
« Last Edit: March 12, 2014, 08:50:22 PM by Bjoern_Hee »

Bjoern_Hee

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Re: Possible new tape knot
« Reply #1 on: February 23, 2014, 06:45:25 PM »
Bonus: Stacked Turns

(stacked_turns.01.jpg)

(stacked_turns.02.jpg)

(stacked_turns.03.jpg)

Tying tape tightly around an object can be done with these stacked turns. Be sure that the turns stack all the way around the object. The "backflip overhand knot" is just one possible knot to hold it all together, but it has the advantage of keeping nicely in line with the turns.

Note that this knot has mechanical advantage. Theoretical mechanical advantage is 2 for 2 stacked turns, 3 for 3 stacked turns... n for n stacked turns. In practice though, friction will cancel out the advantage as the number of turns rises.

Often the knot will hold together by itself when it has been tightened. But if you are worried about it loosening, you can tuck the free end under the turns.

(stacked_turns_with_tuck.jpg)

The best way to do this, is to tuck the free end loosely under the turns before they are tightened. After they are tightened, pull the free end tight.

Hope you liked it. Let me hear your comments.

Enjoy.
« Last Edit: March 12, 2014, 08:47:40 PM by Bjoern_Hee »

xarax

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Re: Possible new tape knot
« Reply #2 on: February 23, 2014, 08:00:16 PM »
A Fisherman s knot tied on webbing - probably prettier than tied on rope.
As you know, the over- and under-hand knots tied on flat strips form a regular pentagon ( ABoK#2588). And the pentagon itself is a beautiful shape !
« Last Edit: February 23, 2014, 09:19:48 PM by xarax »
This is not a knot.

Bjoern_Hee

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Re: Possible new tape knot
« Reply #3 on: February 24, 2014, 08:26:29 PM »
Thank you for your comments xarax.

What I think is unique in the specially dressed fisherman's knot is that the two tapes are on the same straight line, and have the same orientation. It looks like it is a single tape with some disruption in the middle. Let us call this for "continuity" (my word, you are welcome to come up with a better one).

None of the other tape knots I have seen has continuity.

My searching even turned up a couple of fisherman's knots tied in tape, but dressed differently, and thus not continuous.

I know that I can devise other continuous tape knots, but I am quite sure that the specially dressed fisherman's knot is the simplest continuous knot there is.

Hmm... Do I make sense? I know that I am not a good communicator. I need more tries to say things.

As for the stacked turns. It's not the overhand knot, but the stacking, that I think is new and interesting.

And I agree, the small pentagons are indeed very nice  :)

xarax

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Re: Possible new tape knot
« Reply #4 on: February 24, 2014, 09:28:45 PM »
...the two tapes... have the same orientation.

  The overhand knots / helices do not have the same orientation. Obviously, the one is an over-hand knot, and the other is an under-hand knot - and they will always be of opposite handedness ( chirality ), no matter how you orient the tape itself. " Handedness (or chirality) is a property of the helix, not of the perspective: a right-handed helix cannot be turned or flipped to look like a left-handed one, and vice versa - unless it is viewed in a mirror. "  Do not bother if somebody does not understands you right from the first time, as it happens to me now. Try to explain it again, and again, and again.  :) At the end, somebody, the teacher or the student, would learn something more - and, in not-so-rare occasions, both would benefit from this repetition.
« Last Edit: February 24, 2014, 09:45:10 PM by xarax »
This is not a knot.

Bjoern_Hee

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Re: Possible new tape knot
« Reply #5 on: February 24, 2014, 10:00:48 PM »
When you say orientation you talk about the overhand knots. When I say orientation I talk about the tape leading up to the knot...

Take a single rectilinear infinite tape. The middle of this tape is a straight line. Keep it fixed. Then the tape can be rotated up to 180 degrees around this axis (it can also be twisted, but let it be for now). That rotation is what I meant by orientation. It would probably have been clearer if I had called it rotation.

So take a tape knot and put a small screen up in front of it, so it just hides the knot. If the knot is "continuous" what you will see will look the same as if it was a single tape. Because the two tapes lie on a straight line and have the same rotation/orientation.

Hope I make more sense now.

xarax

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Re: Possible new tape knot
« Reply #6 on: February 24, 2014, 10:19:29 PM »
   Perhaps you mean "orientability" ?
   http://en.wikipedia.org/wiki/Orientability
   If you are a 2D creature sliding on the one or the other side of a long continuous tape, if this tape happens to be orientable, you will be condemned to remain on the side you were placed or born in the first place. If your tape is non-orientable, like a Moebius strip,
   http://en.wikipedia.org/wiki/M%C3%B6bius_strip
you can slide along the length of the tape, and reach the same point of the tape you were before, but now on the other side of it. For you, the tape has only one side, because you can move from any point of it to any other point, without crossing the border of the tape or jump out of its surface.
   Do you mean something like this ?
« Last Edit: May 06, 2015, 08:21:33 PM by xarax »
This is not a knot.

Dan_Lehman

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Re: Possible new tape knot
« Reply #7 on: February 25, 2014, 01:55:44 AM »
Bjoern_Hee, I tried something similar to this,
looking at perhaps what appeals to you, the
way the tape's entry and first turn seem to be
so *flat*/kind to the tape.  I had whatever it
was I did tested and it didn't do so well; when
push came to shove, transformation of the tape
was less kind.  (It'll take some digging for me
to find the "whatever it was".  The rockclimbing.com
posts that showed it & test results were deleted
by the angry-at-that-site tester, alas.)


--dl*
====

Bjoern_Hee

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Re: Possible new tape knot
« Reply #8 on: February 26, 2014, 09:20:42 PM »
Dan_Lehman, after reading your comment I can see that the tape probably need a minimum of lateral stiffness for the specially dressed fisherman's knot to dress nicely. I have searched around for tape in another material, but for now I only have the one you see in my pictures. When I find some other tape, in a softer material, I will test the knot with it.

Bjoern_Hee

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Re: Possible new tape knot
« Reply #9 on: March 12, 2014, 08:51:57 PM »
I had these orange straps lying around. They are of a thin woven polymer. Nylon is my guess.

In the attached picture you can see the specially dressed fisherman's knot before and after tightening.

So much for continuity in soft tape... There has to be some lateral stiffness.