Author Topic: Knot advice sought  (Read 3353 times)

murrmac

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Knot advice sought
« on: May 03, 2015, 08:49:12 PM »
Hello all, I would be much obliged if i could be permitted to seek some advice from the knot experts on this forum.Forgive me if I am using the wrong terminology at any point ...I suspect that what I am asking about is actually a hitch but as I say i am no expert.

The application I have in mind is that I want to tie a 2mm diameter leather thong around the stem of a PVC suction cup in such a fashion that the leather will tighten under tension.There will be two tails coming off the stem of the cup, each about 250mm long and they will both be tightened simultaneously, pulled side by side.

I have done one of these using a clove hitch in the centre of a 500mm long leather thong, tightening it and then tying what I would describe as a simple "locking knot" to prevent the hitch from coming loose.

This works, but I suspect that there is a cleverer and more effective way of doing it, and would welcome all suggestions.

FWIW the diameter of the stem on the suction cup is 10mm, and the distance between the top of the cup and the underside of the "cap" is 3mm.

Pictured below is a suction cup similar though not identical to what I am using.



SS369

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Re: Knot advice sought
« Reply #1 on: May 03, 2015, 09:03:23 PM »
Hello all, I would be much obliged if i could be permitted to seek some advice from the knot experts on this forum.Forgive me if I am using the wrong terminology at any point ...I suspect that what I am asking about is actually a hitch but as I say i am no expert.

The application I have in mind is that I want to tie a 2mm diameter leather thong around the stem of a PVC suction cup in such a fashion that the leather will tighten under tension.There will be two tails coming off the stem of the cup, each about 250mm long and they will both be tightened simultaneously, pulled side by side.

I have done one of these using a clove hitch in the centre of a 500mm long leather thong, tightening it and then tying what I would describe as a simple "locking knot" to prevent the hitch from coming loose.

This works, but I suspect that there is a cleverer and more effective way of doing it, and would welcome all suggestions.

FWIW the diameter of the stem on the suction cup is 10mm, and the distance between the top of the cup and the underside of the "cap" is 3mm.

Pictured below is a suction cup similar though not identical to what I am using.

Good day murrmac and welcome.

Knowing the proper terminology, etc. is not a prerequisite for asking a question here. Should you want to learn or contribute could be.   ;)

Two suggestions come to mind quickly and they are the Strangle hitch or the Constrictor Hitch. Both will "lock" sufficiently without additional tangling. http://igkt-solent.co.uk/constrictor-knot-tie/
http://grumpyoldgits.org/GitKnots.html

Neither of these will be easy to untie, if that is necessary.

Some good knots to learn at both sites as well as here in the Forum.

SS

« Last Edit: May 03, 2015, 09:04:43 PM by SS369 »

murrmac

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Re: Knot advice sought
« Reply #2 on: May 03, 2015, 09:46:16 PM »
Thanks SS,  I will have a crack at both of these ... yes, it is kind of important that they don't come loose  unexpectedly, and for the application I have, they should never need to be untied.

xarax

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Re: Knot advice sought
« Reply #3 on: May 03, 2015, 09:52:08 PM »
for the application I have, they should never need to be untied.

Then, and if you have room around the stem for four wraps, "have a crack" :) at this, too :
http://igkt.net/sm/index.php?topic=5212.msg34098#msg34098

However, if you can not put much tension into your material, one of the two Double Constrictors shown in the attached pictures would be fine, I believe:
« Last Edit: May 03, 2015, 10:02:41 PM by xarax »
This is not a knot.

roo

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Re: Knot advice sought
« Reply #4 on: May 03, 2015, 11:09:07 PM »
Thanks SS,  I will have a crack at both of these ... yes, it is kind of important that they don't come loose  unexpectedly, and for the application I have, they should never need to be untied.
I expect that tightening leather will be tricky.  If you have a lot of them to tie, it'd be good to be familiar with the coil-twist fold method that applies to both the Constrictor Knot and the Boa Knot, although in your case, a Constrictor (starting with a single coil) will probably do fine:

http://notableknotindex.webs.com/boaconstrictor.html

If you wish to add a troll to your ignore list, click "Profile" then "Buddies/Ignore List".


Dan_Lehman

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Re: Knot advice sought
« Reply #5 on: May 04, 2015, 11:09:36 PM »
I suspect that what I am asking about is actually a hitch but as I say i am no expert.
Yes, though a particular, unusual one,
with both ends loaded together (adjacent),
not merely one loaded and a free end (tail).

Quote
The application I have in mind is that I want to tie a 2mm diameter leather thong
around the stem of a PVC suction cup
//
... and the distance between the top of the cup and the underside of the "cap" is 3mm.
And X. wonders at using FOUR wraps of 2mm to fit into 3mm space !!
But you've at least done the obvious, with the clove hitch
--although, tell us, where was the center of this hitch :
at the away (top, if pulling downwards) side of the stem,
or with the ends?  In the first case, the ends would pull
into the stem at near tangents (encountering wrapped
material squeezed in those scant 3mm),
wheres in the other way, the ends would bear into
the crossing part of the clove to swing in opposite
directions to then turn around the stem --an inferior
orientation, IMO.

Given the frictive nature of the material (as Roo remarks),
I'd think that the clove h. sufficed.  Still, though
one has the issue of each end coming into two turns
around the stem which are alreay squeezed tight; perhaps
that end-entry & squeeze just hastens the rise of turns
into the crossing part, no real problem --so long as
tension is equal on the ends and there's no rotation
around the stem.

Quote
in such a fashion that the leather will tighten under tension.
I believe I echo Roo's thought that leather thongs will be
frictive and take special attention to set tight --such as
pushing against the knot while pulling (maybe individually)
each end.  In other words, I don't see a hitch here, with
expected moderate loading (how much can it be?), doing
much "tightening under tension" : you will have whatever
tightness you set the knot at, and forever hold your peace!
(And this should be fine.)

 
Quote
tightening [the clove hitch and then tying what I would describe
as a simple "locking knot" to prevent the hitch from coming loose.
Do you really have an issue with loosening (given my
remarks above, re "frictive" material --leather) ?!!
I'm surprised, if so.

Quote
This works, but I suspect that there is a cleverer and more effective way of doing it, and would welcome all suggestions.
I was expecting Xarax to suggest something that
incorporates a nipping turn (with "Gleipnir" mechanics)
along the lines of a bull hitch; let me verbally describe
an implementation/instantiation of this notion.
.:.  The goal is to minimize turns in the precious space
of the stem --we'll have two--, and to lock a tensioned
knot --we'll invoke a turNip (and as many funny terms
as we can  ;D  ).

1) Take the line around the stem,
2) turn around the end (you're working with
other end) and tuck UNDER this turn to complete
a full (round) turn (just as one would to begin
tying two half-hitches); now, take
3) the (working) end around again, *atop*
(i.e., nearer the top of the stem, aka away from
suction side) the first turn, and
4) bring out the working end through the
"turNip" formed in steo (2) --and thus, both
ends are now surrouned/nipped by this turNip.
  ((So, the ends run in opposite directions, tangent
    to the stem on opposite sides.))
5) Tighten by careful pushing on the turNip and
pulling on one or both ends (as you feel works best).

Pulling on both ends will tend to press against the
constricting of the turNip, so pulling on just
one end should work best at getting tension into
this nipping turn; maybe alternating pulling on ends
and pressing the turn against the stem, working it
tighter.

I don't know leather well, but possibly(?) it would
work best to use wet leather, gain enhanced slipping,
and then when dry it will be all the tighter?!  (And
maybe it's possible to overdo this bit, even, if the
effects are dramatic?  Again, I'm unsure about this.)


--dl*
====

xarax

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Re: Knot advice sought
« Reply #6 on: May 05, 2015, 02:03:16 AM »
... and the distance between the top of the cup and the underside of the "cap" is 3mm.
   And X. wonders at using FOUR wraps of 2mm to fit into 3mm space !!

  Because, to my eyes, it looks more likc 3cm, and a typo.
This is not a knot.

Sweeney

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Re: Knot advice sought
« Reply #7 on: May 05, 2015, 09:21:46 AM »
Assuming that the neck is actually 3mm (I doubt it is over an inch long - I have a similar one in the shower) then perhaps a Poacher's Noose might fit the bill. Tied in the middle of the leather starting with a loose knot and adjusting carefully this will tighten from one side but given the frictive nature of leather the actual movement once snugged up close should be minimal if at all. Whether this is a viable option depends very much on what is going to be suspended.

Barry

xarax

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Re: Knot advice sought
« Reply #8 on: May 05, 2015, 12:35:23 PM »
  Assuming that the neck is actually 3mm

  If it is, and the plant at the background is so microscopic, then it is a matter of fishing lines and knots  :)  - and  I do not believe that fishermen were using that material ( leather ! ! ), EVER !  :)
This is not a knot.

Sweeney

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Re: Knot advice sought
« Reply #9 on: May 05, 2015, 01:01:04 PM »
  Assuming that the neck is actually 3mm

  If it is, and the plant at the background is so microscopic, then it is a matter of fishing lines and knots  :)  - and  I do not believe that fishermen were using that material ( leather ! ! ), EVER !  :)

Perhaps the OP would clarify this? The picture is only similar to the actual cup so may well be a different size though the same design (the picture says that it is 63mm - diameter presumably - which would be about right for a 3mm collar within about a 20mm knob on top).

Barry

Barry

xarax

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Re: Knot advice sought
« Reply #10 on: May 05, 2015, 01:18:56 PM »
  the picture says that it is 63mm - diameter presumably - which would bebout right for a 3mm collar

  Diameter or radius ? And of what ? There are two circular things here, the upper/smaller and the lower/larger rim.
  ( And the even smaller hole on top of the cover... )
   
« Last Edit: May 05, 2015, 01:21:05 PM by xarax »
This is not a knot.