Author Topic: Best lashing knot for three perpendicular poles.  (Read 25184 times)

xarax

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Best lashing knot for three perpendicular poles.
« on: October 28, 2010, 07:08:53 AM »
Best lashing knot for three perpendicular poles.
  
« Last Edit: January 30, 2011, 12:05:07 PM by xarax »
This is not a knot.

knot4u

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Re: Best lashing knot for three perpendicular poles.
« Reply #1 on: October 28, 2010, 09:42:07 PM »
I'm no expert, but this tripod lashing (racking turns) works and is easy for me to remember:
http://www.ropeworks.biz/archive/tripod.html
« Last Edit: October 28, 2010, 10:06:36 PM by knot4u »

SS369

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Re: Best lashing knot for three perpendicular poles.
« Reply #2 on: October 28, 2010, 11:58:33 PM »
"Bind three poles, in touch and perpendicular to one other, with one piece of rope, as tightly as possible."
This above statement is what you are trying to accomplish?
Perpendicular:  noun:   a straight line at right angles to another line
                adjective:   intersecting at or forming right angles
They are the same size I assume, touching each other (no rope between them) and perpendicular to each other?

What will be the abstract purpose of these three poles?
Do they have to support themselves in this configuration or bear additional weight?
Or is this decorative?

Scott

SS369

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Re: Best lashing knot for three perpendicular poles.
« Reply #3 on: October 29, 2010, 03:15:34 AM »
The sticking point here for me is the need for the poles to be oriented Perpendicular to each other.
To me that means they are to be at right angles, 90 degrees to each other.
And if only the ends are to be joined the I see the need to "waste" cord with frapping turns.
Otherwise a knot is to be tied and then the parts of the affair rotated to induce a tightening twist.
The knot must have sufficient round turns to reduce the load(s) on the cord alleviating the strain on one small area.
If the knot is overtightened before the twist/reorienting is done then all bets are off.
The attached is a fairly simple tripod style lashing that to me reduces the frapping turns.

S

knot4u

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Re: Best lashing knot for three perpendicular poles.
« Reply #4 on: October 29, 2010, 04:01:44 AM »
SS, I don't understand what's going in step 3.  Is there a better diagram?

SS369

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Re: Best lashing knot for three perpendicular poles.
« Reply #5 on: October 29, 2010, 04:17:02 AM »
Hi knot4u,
what is happening is the same as in doing the sail-makers whipping.
The cord is being roved between the poles to fill and tighten.
It is just an alternative to "standard" sheer lashing.
No I don't have a better diagram at present, sorry.

oldpete

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Re: Best lashing knot for three perpendicular poles.
« Reply #6 on: October 29, 2010, 06:12:46 AM »
i think people are getting confused by the perpendicular part. think of the corner of a table, one pole is one side, one is the other and the third is the leg . i e repeat 4 times to make your table frame. hope this helps

knot4u

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Re: Best lashing knot for three perpendicular poles.
« Reply #7 on: October 29, 2010, 06:29:51 PM »
Exactlly ! The poles are put as to be oriented perpendicular from each other right from the begining, before they are bound together, and they stay so till the end...  

While we're looking for a knot solution, I'm also interested in a solution for holding the poles in that position before the rope is applied.

If the practical application is heavy logs, which you mentioned above, then having the poles in the final position before tying the rope is already a difficult thing to do.  For this pre-problem, I'm imagining some kind of support on each leg to hold each leg up at the appropriate angle.  Based on your criteria that I quoted, you may have eliminated the option of tying two legs and then attaching the third.  Or did you not mean to eliminate that option?
« Last Edit: October 29, 2010, 06:35:35 PM by knot4u »

knot4u

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Re: Best lashing knot for three perpendicular poles.
« Reply #8 on: October 29, 2010, 08:01:44 PM »
You have a nearly impossible problem.  With heavy logs, the rope will have to overcome an extremely high moment of inertia on each leg.  The tripod lashing may consume a lot of rope, but this contraption would consume way more rope to keep the legs stable.

Unless... You first carve out pegs and recipient holes in each leg.  Fit the legs together so that they form the right angles as described.  Then, apply the rope around the vertex such that the rope provides support to the pegs and holes.  The pre-fitting will take strain off the rope.  Even then, I think you'll need additional support beams to support the three legs, like the cross beams at the top of this structure:



By the way, rope is not the best solution to this problem, but we're all playing along because that's the parameters.
« Last Edit: October 29, 2010, 08:46:31 PM by knot4u »

knot4u

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Re: Best lashing knot for three perpendicular poles.
« Reply #9 on: October 29, 2010, 10:47:34 PM »
You have a nearly impossible problem.  With heavy logs, the rope will have to overcome an extremely high moment of inertia on each leg.  The tripod lashing may consume a lot of rope, but this contraption would consume way more rope to keep the legs stable.

No!  :) The weather beaten, standard solution of engineers, when they have an orthogonal frame with joints of beams and it is hard to keep them together at right angles, is to put diagonals that keep the corners at a constant distance, so that the whole frame is stabilized. The diagonal cables/ropes connecting the opposite corners do what is called "triangulation", and take off most, or even all, the strain of the joints, so the angles do not become oblique - i.e, the shape of the frame remains an orthogonal parallelogram, it is not transfigured to an oblique one. Bind the three poles at each corner for me as tightly as you can, so that they do not slip, and I will manage to prevent our parallelogram decay into a rhomboid.  :)

Well, yeah, but you just added more material.  I thought the only material we had were the three legs and rope.

If we can add other materials, then your problem becomes trivial.  You bind two legs on the ground at a right angle by using a cross beam and nails/bolts.  Then, bind the third leg by using two more cross beams.  You can add the rope, but it would be unnecessary.  I have made this type of construction before.  If you remove the crossbeams and have just rope at the vertex, then the structure becomes unstable.  I wouldn't use if for anything other than art.
« Last Edit: October 29, 2010, 10:59:52 PM by knot4u »

DerekSmith

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Re: Best lashing knot for three perpendicular poles.
« Reply #10 on: October 30, 2010, 01:17:52 PM »
Have you considered the Chinese bamboo scaffold solution?



Derek

DDK

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Re: Best lashing knot for three perpendicular poles.
« Reply #11 on: October 30, 2010, 07:48:30 PM »
Many "tripod" junctions by knots are known, but I think they are not satisfactory, ... Notice also that the first and the third of the poles are not tied to each other, ...

A cloverleaf lashing (slightly adapted for non-parallel poles) would connect each pole to the other and maintain the symmetry of the joint.  Tightening will need to be addressed for any method where the poles are to remain stationary during the entire process.  Tourniquet methods may be of use for tightening?  This topic falls under the category of "Pioneering" for those of us that are/have been involved in scouting.

DDK

DDK

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Re: Best lashing knot for three perpendicular poles.
« Reply #12 on: October 31, 2010, 02:15:46 AM »
This topic falls under the category of "Pioneering" for those of us that are/have been involved in scouting.
... Yes, it could be useful in scouting, and, in fact, it is , but its general character makes it an interesting knot problem for all of us, I believe.  

You may have read more into my comment than I had intended.  I certainly was not implying that this was only of interest to scouts nor was I suggesting that this knot problem would only arise for those engaged in Pioneering.  As it happens, this problem has been addressed by several involved in Pioneering and their solution may be worth a look.

The cloverleaf lashing was developed to address the multiple attachment of poles at (or near) a single point.  I have seen examples of 4, 5 and 8 pole attachments.  For 3 poles, the attachment would be at a single joint (that is, each pole is intimately connected to the other two with the use of in total a single lashing).

DDK
« Last Edit: October 31, 2010, 02:25:46 AM by DDK »

DDK

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Re: Best lashing knot for three perpendicular poles.
« Reply #13 on: October 31, 2010, 07:25:49 AM »
...  For 3 poles, the attachment would be at a single joint (that is, each pole is intimately connected to the other two with the use of in total a single lashing).
   So you would have three two-poles lashings, not a one three poles binding knot ! :)

No.  You would have one (single) three pole binding knot (lashing).  If one googles cloverleaf lashing, the first link to be listed has a description of this lashing

http://ropesandpoles.blogspot.com/2007/06/clover-leaf-lashing.html

DDK
« Last Edit: October 31, 2010, 03:29:32 PM by DDK »

DDK

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Re: Best lashing knot for three perpendicular poles.
« Reply #14 on: October 31, 2010, 08:51:44 PM »
... The fact that the same piece of rope can go around the 4 or n number of poles, the one after the other, does not makes such lashings one integrated knot, I believe -  but exactly a compound knot made by the addition of more and more lashings, that I  have talked about in my previous post. ...

Indeed, when the number of poles is 4 or more, I would also describe the cloverleaf lashing as a compound knot or multiple joint as it is clear that each pole is not directly connected to all the others.  When the number of poles is 2 or 3, however, this is not the case and it is clearly not a compound knot, but a single binding.  For the problem you posed, the number of poles is 3.

...  Moreover, trying to tighten this type of lashings without the use of other tools and tricks is impossible, because the poles are not in touch with each other in the first place. ...
A cloverleaf lashing (slightly adapted for non-parallel poles) would connect each pole to the other and maintain the symmetry of the joint.

As I have mentioned in a previous post, the cloverleaf lashing would need adapted to non-parallel poles.  One of these adaptations could be to have the poles in contact.  To point out what may be obvious, one way to reverse-engineer the lashing for non-parallel poles would be to:

(1) Apply the round turns but not the fraps to 3 parallel poles.
(2) Spread the tripod to the orthogonal condition desired (there is a clockwise spread and an anti-clockwise spread - one will tend to tighten the lashing and the other will tend to loosen the lashing).  I would speculate that the spread that loosens the lashing will be preferred in that the applications of fraps will be more effective at tightening the lashing.
(3) Observe the wrapping of the round turns.
(4) Develop a method for the application of the fraps and the tightening of the lashing.

I would assume that all of this has been accomplished a number of times by those that commonly use the cloverleaf lashing, however, I have not seen it reported.

To summarize what I believe to be true about the use of the cloverleaf lashing on 3 poles is this:

(1) The poles can be in contact, orthogonal and stationary prior to their binding.
(2) It will be a single binding.
(3) The lashing will have the same three-fold axial symmetry as the arrangement of the poles. This "cube-corner" symmetry is the same as found in the Monkey Fist, for example.
(4) The application of fraps for the purpose of tightening will be as effective as in most lashings.

DDK
« Last Edit: October 31, 2010, 08:53:59 PM by DDK »