Author Topic: Knot wanted  (Read 13097 times)

redbug444

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Knot wanted
« on: April 25, 2010, 08:22:37 PM »
I've a specific project I am going to need to tie hundreds of knots for it, so I need to find the best one, and I'm hoping you might help me out.

I am making a series of trellises for the walls of a yurt. They are made of approx. 3/4" dia roundwood poles which cross at 90 degrees. The poles are to be joined at each intersection by threading a short length of 4mm diameter cord through 4.5mm holes in the poles. The cord is fairly soft, it has a cotton core and a woven polyester outer layer. It takes knots well, but does have a limited amount of stretch. The softness of the cord means that small knots, like a thumb knot, may pull through the holes.

My problem is that the cord needs to be fairly tight through the holes. I've tried tying a simple figure-of-eight knot at each end but can't get cord taut enough. Any ideas?

(I know almost nothing about knots so please don't hesitate to point out the blindingly obvious, thanks)

Osita505

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Re: Knot wanted
« Reply #1 on: April 26, 2010, 12:01:45 AM »
There's a good article by Dan Lehman called "various binders tasks" or something similar wherein he addresses applications like you're describing and offers some suggested knots.

SS369

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Re: Knot wanted
« Reply #2 on: April 26, 2010, 01:37:17 AM »
If a small loop can be used then any number of slide and grip knots will be suitable. Just go around the "X" of the poles and tie a draw loop. It will be a whole lot easier on the hands.  ;)
Also a variety of temporary lashings come to mind.
I presume that this structure will be disassembled in the future?

Hope this was food for thought.

SS

Fairlead

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Re: Knot wanted
« Reply #3 on: April 26, 2010, 09:55:11 AM »
I take it the knot has to be a 'stopper' knot - if so I would be inclined to use the "Double Overhand Knot" (Thumb knot with two tucks) - it looks nice too.

Fairlead

DerekSmith

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Re: Knot wanted
« Reply #4 on: April 26, 2010, 03:04:02 PM »
Hi Redbug, welcome to the IGKT - You bring to the forum a really interesting project.

Because this trellis is for a Yurt, three aspects need to be considered in selecting a binding.

First, unless your Yurt is intended to be permanent, then the trellis is intended to be collapsible for packing and shipping, so conventional trellis cross strapping systems become meaningless.

Second, because all of the downward force from the roof (including wind force) is attempting to force the crossed stays apart, the connecting cord is under considerable shear rather than tension.  This means your cord should be good at resisting shear, but it also means that there is not much tension trying to pull the cords through the lattice poles.

Third, Because of the round nature of the Yurt, the alignment of the holes rotates in opposite directions at the top from the bottom, this means that rigid pins more ideal to take the shear would not be suitable because they would twist the spars, and consequently some slack is necessary in the connection cord to allow for this alignment change.

This comes down to using a nice fat (thick) cord, not tied too tightly and only requiring a thumb knot to stop it from pulling through.  You can 'roll' the thumb knot up to the face of the spar hole before setting it, and this will be plenty tight enough for the desired use.  Just make sure that the cord you choose has some body to it and that it does not deform to any great extent under tension, and then it should not show any signs of pulling through the hole.



Remember, no single knot or spar takes the whole load, a Yurt is an entity comprising the sum of its component parts, each taking a share of the load, and each contributing to the overall strength and stability (except perhaps for the tension rope - if that fails, the whole thing can come down).

Derek

Dan_Lehman

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Re: Knot wanted
« Reply #5 on: April 27, 2010, 04:41:08 AM »
That is one tactic.

Another would be to essentially tie a ring,
which happens to run through the holes
-- and which conceivably could be rotated
a little, to share the wear across the cord.

I see a yurt under assembly via Wikipedia -- to wit:
en.wikipedia.org/wiki/File:Yurt-construction-2.JPG

Except that the pictured one has (I think) square vs. round
slats being bound by cord through holes.  For my suggestion
to tie a ring, round slats might work better.  One quick idea
for this is to tie the one Overhand stopper around the working
end (this would be the end with lots of rope, which you're
using over & over as you move from hole to hole (like the
"bitter end" is the end/part/"half" at the bitts)) and then
pull to desired tightness, and then tie off the long/working
end around the end of the first Overhand; and cut away.

It depends when you do this:  for with the structure collapsed
(as for transport), the ring has a shorter run to make than when
the joined slats assume their near-right-angle disposition.  Perhaps
this upon-opening tensioning might even be helpful -- or that the
closed rings would be helpful in arresting/resisting the opening
going too far?!

And it means that you're using more cord.
The above-sketched knot-joint isn't the greatest bend, for sure;
but it might not need to be (no matter how many you're tying)
-- just good enough to do the job, and quickly enough tied:
that is what you need, for starters.

--dl*
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Dan_Lehman

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Re: Knot wanted
« Reply #6 on: April 27, 2010, 05:12:31 AM »
I take it the knot has to be a 'stopper' knot - if so I would be inclined to use the "Double Overhand Knot" (Thumb knot with two tucks) - it looks nice too.

But the problem is at both ends -- which may be named
pointedly "the first-tied" & "the in-tension-tied" :  it is in making
the finishing knot that one finds that, aside from the simple Overhand,
most stoppers can't be tied snug to the stopping *frame*!  (And I
even struggle getting the Overhand up tight against whipping when
putting one in as the last element of that.)

But this problem moved me to invention:  #20100426m23:49
I'll ID-time-stamp it.
Tie a Slip-knot, with ample bight/loop;
bring the bight back around over the working end
(so the bight might need to be quite large if you're
with a good bit of material);
and pull it then taut around the throat of the Slip-knot!?
-- which should both add a bit of bulk, and take up some of the
slack in the joining cord (i.e., this choke at the throat will be
between Overhand and slat).

How's that work for you?
Oh, well, yes, that is just one end --the finishing one--
getting added material (in part though for tension);
for the initial knot, you might employ Ashley's Stopper
(aka "Oysterman's Stopper").  Voici:   en.wikipedia.org/wiki/Ashley's_stopper_knot
NB:  Between Steps 1 & 2 here, one must haul the Overhand component TIGHT
-- it won't be tightened in use, and it must resist having the loaded
part pull through it.

--dl*
====
« Last Edit: April 27, 2010, 05:24:09 AM by Dan_Lehman »

redbug444

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Re: Knot wanted
« Reply #7 on: April 27, 2010, 10:28:44 AM »
Wow, lots of good ideas, thank you.  :)

 I'll try them out and let you know how I get on.

DerekSmith

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Re: Knot wanted
« Reply #8 on: April 27, 2010, 04:01:46 PM »
@redbug444 - I look forward to hearing how your project goes, especially bits that don't work and why.  Any chance of some pictures please?

@Dan - the "Oysterman's Stopper" makes it harder to roll the thumbknot up to the spar, and although it is a larger knot, it has not increased the diameter of the knot at all, so it should be just as easy to pull through as the thumb knot (I haven't tried it).

Derek

roo

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Re: Knot wanted
« Reply #9 on: April 27, 2010, 04:24:16 PM »
I've a specific project I am going to need to tie hundreds of knots for it, so I need to find the best one, and I'm hoping you might help me out.

I am making a series of trellises for the walls of a yurt. They are made of approx. 3/4" dia roundwood poles which cross at 90 degrees. The poles are to be joined at each intersection by threading a short length of 4mm diameter cord through 4.5mm holes in the poles. The cord is fairly soft, it has a cotton core and a woven polyester outer layer. It takes knots well, but does have a limited amount of stretch. The softness of the cord means that small knots, like a thumb knot, may pull through the holes.

My problem is that the cord needs to be fairly tight through the holes. I've tried tying a simple figure-of-eight knot at each end but can't get cord taut enough. Any ideas?

(I know almost nothing about knots so please don't hesitate to point out the blindingly obvious, thanks)

Sounds like the perfect job for small bolts & nuts (washers optional).  
« Last Edit: April 27, 2010, 04:25:49 PM by roo »
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Dan_Lehman

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Re: Knot wanted
« Reply #10 on: April 27, 2010, 05:39:31 PM »
@Dan - the "Oysterman's Stopper" makes it harder to roll the thumbknot up to the spar, and although it is a larger knot, it has not increased the diameter of the knot at all, so it should be just as easy to pull through as the thumb knot (I haven't tried it).

This stopper is the 1st tied -- there is no rolling-up-the... required/expected.
And it is indeed much larger in stopper face than an Overhand -- it is, after
all, an Overhand around a strand; and it orients the Overhand fully as the face.
(This should be easily seen?!)

--dl*
====

Justin

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Re: Knot wanted
« Reply #11 on: April 27, 2010, 07:51:04 PM »
Sounds like the perfect job for small bolts & nuts (washers optional).  

My thoughts exactly or if you wanted to go with a non comercial option you could use wood dowels with a small hole for another pice of wood (sort of loke a cotter pin)
Justin

Rrok007

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Re: Knot wanted
« Reply #12 on: April 28, 2010, 02:12:21 AM »
Sounds like the perfect job for small bolts & nuts (washers optional).  

My thoughts exactly or if you wanted to go with a non comercial option you could use wood dowels with a small hole for another pice of wood (sort of loke a cotter pin)


Except that I'm thinking Derek was trying to point out the structure, due to it's nature is going to have some flex and bend to it naturally, more so under various environmental forces. In such a case, a flexing connector is going to be more desirable since it can essentially take most, if not all of the tidal nature of the forces at play, with little effect on the the more rigid members.

DerekSmith

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Re: Knot wanted
« Reply #13 on: April 28, 2010, 11:05:34 AM »
@Dan - the "Oysterman's Stopper" makes it harder to roll the thumbknot up to the spar, and although it is a larger knot, it has not increased the diameter of the knot at all, so it should be just as easy to pull through as the thumb knot (I haven't tried it).

This stopper is the 1st tied -- there is no rolling-up-the... required/expected.
And it is indeed much larger in stopper face than an Overhand -- it is, after
all, an Overhand around a strand; and it orients the Overhand fully as the face.
(This should be easily seen?!)

--dl*
====

Well corrected Dan - my mistake.

Derek

redbug444

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Re: Knot wanted
« Reply #14 on: April 28, 2010, 11:56:17 AM »
Sounds like the perfect job for small bolts & nuts (washers optional).  

My thoughts exactly or if you wanted to go with a non comercial option you could use wood dowels with a small hole for another pice of wood (sort of loke a cotter pin)


These are sometimes used, but there are a number of problems:

1  Not flexible, I'm using roundwood poles ie. tree branches. There needs to be some give to accomodate irregularities in the wood.
2 The structure is to be covered in cotton canvas. Metal fixings could cause wear to the cover.
3 Rust staining to the cover
4 Cost of stainless fixings

The dowel option is interesting but there is no flex and I think it would stick out a lot and potentially wear the cover.

Thanks for your input tho.