Author Topic: Very tight hitch around circular object - best load distribution  (Read 2521 times)

Knutern

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Hi.

I'm planning to use rope to fasten two plastic pipes. The ends of one pipe just fits the end of the other one, but they're not stuck and the joints are not water resistant.

So my idea is simply to tie a rope around the muff, and pull it very hard (using tool).

I would like to use a Constrictor knot or TackleClamp hitch (4 wraps I figured keep a good grip).

However, I do have a concern. As far I know, most (if not all) of the constrictor-like hitches will make more pressure at the pipe just beyond the hitch, compared to the rest of the rope around.
I've tested on the paper pipe from an empty toilet roll, and based on that my concern seems to be rightfull. The thin paper pipe always collapses right beyond the hitch.

Question: Does it exist a hithc working the same way of an constrictor hitch, but distribute the inward forces more evenly?

jpg attachment: Sorry for bad drawing, it's supposed to depict a constrictor hitch on a collapsed paper roll.
I'm aiming for knots that is secure, AND that is easy to untie.

SS369

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Re: Very tight hitch around circular object - best load distribution
« Reply #1 on: August 13, 2015, 09:36:36 PM »
High Knutern.

The way I see it is, with this type of application and knots, the nub will always produce an area of highest pressure directly beneath it. If the material is deformable, then it bend or deflect there.
Multiple wraps around the object(s) before tying the nub should help to spread the load around, but the cause for deflection will still be there trying to influence the material.

The TackleClamp (multi wrap) hitch might be the better because it pulls tightly from both direction and you will have two nubs hopefully in balancing positions, though that may be fiddly to dress.

SS

roo

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Re: Very tight hitch around circular object - best load distribution
« Reply #2 on: August 14, 2015, 05:15:57 AM »

Question: Does it exist a hithc working the same way of an constrictor hitch, but distribute the inward forces more evenly?

You'll have to tell what you're doing with these plastic pipes.  They must not be very substantial.

To avoid the capstan effect, you could employ shrink tubing and use a heat gun to evenly shrink things all around.  I'm not sure what you're using, so I can't be sure it'll have the desired effect.
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xarax

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Re: Very tight hitch around circular object - best load distribution
« Reply #3 on: August 14, 2015, 06:36:27 AM »
   I believe you made the right choice - to come and discuss about tight hitches in this Forum ! :) It is the Mother-of-All-tight-hitches  ! :)
   Try to anticipate how much the consuming of the slack will take, and dress the TackleClamp hitch as shown in the pictures - i.e., whit the two linked U s pairs at diametrically opposite sides.
 ( Or, wait a few hours, because I had fried some new fishes for you. :)
   
« Last Edit: August 14, 2015, 06:37:45 AM by xarax »
This is not a knot.

Dan_Lehman

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Re: Very tight hitch around circular object - best load distribution
« Reply #4 on: August 14, 2015, 07:46:32 PM »
Perhaps one can use two constrictors and
tighten them together, at first, and then iteratively
further tighten one then the other!?  (Perhaps there
is a clever way to *intermingle* their wraps vs. just
having them adjacent?  --or maybe this would be
too clever by half!)


--dl*
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xarax

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Re: Very tight hitch around circular object - best load distribution
« Reply #5 on: August 14, 2015, 08:05:05 PM »
maybe this would be too clever by half!)

   Right ! The Constrictor is one of the hyper-hyped knots - it is NOT so tight, and, most importantly, it can not be tensioned by pulling its ends against the pole : big, huge disadvantage ! ( The humble Strangle is much better in this ).
   Of course, the TackleClamp hitch which is twice as tight, should not be mentioned at all : ssss... It is one of those "random" knots I had tied, entangling, like an ape, strands of ropes purposely, somehwhat they would had been entangled in the drum of a dL s washing machine :) - so it better be buried under tons of silence . :) ( How naive people are, when they try to convince themselves about something, still surprizes me... )
« Last Edit: August 14, 2015, 08:06:14 PM by xarax »
This is not a knot.

Dan_Lehman

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Re: Very tight hitch around circular object - best load distribution
« Reply #6 on: August 17, 2015, 10:46:24 PM »
maybe this would be too clever by half!)

   Right ! The Constrictor is one of the hyper-hyped knots - it is NOT so tight, and, most importantly, it can not be tensioned by pulling its ends against the pole : big, huge disadvantage ! ( The humble Strangle is much better in this ).
   Of course, the TackleClamp hitch which is twice as tight, should not be mentioned at all : ssss... It is one of those "random" knots I had tied, entangling, like an ape, strands of ropes purposely, somehwhat they would had been entangled in the drum of a dL s washing machine :) - so it better be buried under tons of silence . :) ( How naive people are, when they try to convince themselves about something, still surprizes me... )
More empty assertions, still from years back when
your "starry eyed" [sic] visions for the binder I'd
presented (yet you make it sound as though it's all
foreign to me, who introduced it!!) (mis)led you to
see it as a knot panacea!

My caveats are well stated in the thread the OP has
referred/linked to, so I will only summarize to say
that working with two constrictors might yield
a better solution --although he IS aiming to apply
the knotting to firm-slick plastic pipe, in which the
opposed nipping bights of the more clever knot
can do their thing.

Now, perhaps the OP can report back his experiences
in trying out various proposed solutions, and chance
getting some edification to balance all the pontification.


--dl*
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Knutern

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stilll testing
« Reply #7 on: August 18, 2015, 12:59:18 AM »
Hi.

Still testing on those paper rolls (and some other solid sylidrical objects) and trying to decide.

What I found is that i do beleive the TackleClamp will be the final choice. However there is some concern I have about the TackleClamp:
  • The upper side (the side of the pole that have 4 "layers" of rope) is exposed to a some greater force than the oposite side. For a simple paper roll, this means that one half of the roll bends inward less than the other half - yet without completely collapsing.
  • Dressing. Espechially in combination with soft rope and pole with large diameter and where the nubs are closing into each other - I experience that one or both of the free ends of the rope won't lock, but rather slide aside to a position that won't lock. Maybe the solution is to make sure the two free ends is located at oposite side of the pole to each other - I haven't tested that yet (need to find some thick pole to test on)

See - I've get in hand just a few pipes and won't destruct those by choosing the wrong solution.
I'm aiming for knots that is secure, AND that is easy to untie.

xarax

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Re: stilll testing
« Reply #8 on: August 18, 2015, 02:08:30 AM »
The upper side (the side of the pole that have 4 "layers" of rope) is exposed to a some greater force than the oposite side. 

   Is it ? We have to measure it. The midde of the three segments of the 3-wrap side is / remains possibly more tensioned than the others, so I believe that the total "push" to the surface of the pipe from the two sides will be almost equal.

the solution is to make sure the two free ends are located at oposite side of the pole to each other

   Yes. Read in the relevant threads and posts what is written about the danger the hitch "closes" prematurely.
The trick is to first tighten each "half" of the hitch somewhat, pulling each end against the pole, but not towards each other, so they will not be transported towards the middle of their distance too early - and only then, when the hitch is already somewhat tight, and most of the slack is consumed, to start pulling them so the bights connected to them start to approach each other.
   Also, do not forget, at the end, to pull the ends one by one, the one after the other, alternately, as we have to do with all tight hitches.

   The important thing to remember, is to pull the two ends and tighten the whole knot in two stages. At the first stage, the two bights should better be at diametrically spaced positions.
  When I say that one should pull the ends "the one after the other", I mean to pull the ends in an alternating way, first the first, then the second, then again the first, and so on...I do not mean literally "pull the first end, then pull the second end, period". So, one should tighten the TackleClamp hitch by pulling the first end a little bid, then the second end this much, then again the first end a little bid more, and so on - until he can not pull any end any more - just as we do when we tighten multiple nuts. Otherwise one can run the danger to pull the first end all the way to the end, and have a hitch where the two opposing bights have "kissed" each other, without the hitch having been tensioned to the maximum degree.
  tie this 3-wrap hitch as tight as you can  ( as I said, first taking out any slack, before the pulling - then pull alternatively, the one end after the other, starting from a proper position of the two opposed bights on the surface which will enable their tensioning right to the end, before they will have the chance to "kiss" each other 
« Last Edit: August 18, 2015, 02:28:46 AM by xarax »
This is not a knot.