Author Topic: Sheepshank alternative that remains tied while slack  (Read 124 times)

jmlucassen

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Sheepshank alternative that remains tied while slack
« on: September 06, 2019, 12:21:45 AM »
APPLICATION/PROBLEM
I have a tree pruner on an extendable shaft, and it comes with a pull cord with a nice handle on it.
Unfortunately, when the shaft is not fully extended, the cord is too long to use the handle, so I need a way to shorten the cord.
I would like it to be easy to tie, remain tied while slack, be secure under load, and easy to untie.

SOLUTIONS USING STANDARD KNOTS
- Overhand loop ABOK#1046. 
Con: hard to untie after it has been loaded.

- Sheepshank ABOK #1152 - #1154. 
Cons: does not remain tied while slack; not very secure

- Butterfly loop ABOK #331, #532,[1] #1053. 
Meets stated requirements.  Probably the best standard solution. 
Cons: this is not a well-known basic knot, so novices may have trouble tying it.  Also, untying requires prying the knot open.

- PROPOSED NEW SOLUTION: two interlocking overhand loops
Choose two spots on the cord so that the distance between them is the amount by which the cord needs to be shortened
Tie a slip knot (ABOK#529) at each spot. Tie the two knots in the same way, i.e. in the same orientation.
Adjust each knot so that its loop is big enough so that the other knot can pass through it.
Identify which of the two slip knots tightens when its free end is pulled and call it knot A.  Call the other one knot B.
Push knot B and its loop through the loop of knot A and tighten knot A by pulling its free end.
(You can confirm the knot is secure by pulling on both free ends.)
(The result is a knot with two free ends, a small loop on one side (that of knot B) and a larger loop on the opposite side (the slack that needed to be eliminated)
TO UNTIE:
Tug on the ends of the large loop to find out which one tightens the loop of knot B, and pull that one to collapse knot B and pull it out of the loop of knot A.
The rope is now back to its original length with knot A left, which can be collapsed by pulling.

I would welcome any feedback on this "new" knot.
« Last Edit: September 06, 2019, 12:23:18 AM by jmlucassen »

SS369

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Re: Sheepshank alternative that remains tied while slack
« Reply #1 on: September 06, 2019, 01:19:43 AM »
Good day.

First, I would like to see a picture of what you?re offering.

Second, in regards to the cord length challenge on your pole pruner. What I have done with mine is slide the handle to where I want it and tie a slip knot below the handle and let the surplus just dangle

SS

Dan_Lehman

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Re: Sheepshank alternative that remains tied while slack
« Reply #2 on: September 06, 2019, 01:23:04 AM »
APPLICATION/PROBLEM
I have a tree pruner on an extendable shaft, and it comes with a pull cord with a nice handle on it.
Unfortunately, when the shaft is not fully extended, the cord is too long to use the handle, so I need a way to shorten the cord.
I would like it to be easy to tie, remain tied while slack, be secure under load, and easy to untie.
How is the cord secured to the device's handle?
I'm wondering if it were secured with a stopper knot,
you could simply pull cord out and put in new stoppers
(slip knots) as you needed them.
[Which has been the first responder's solution, I see.]

You could also just tie off the line by taking two bights
of it --leaving the slack needed drooping-- and tying,
say, a sheet bend / square knot.

Quote
- PROPOSED NEW SOLUTION: two interlocking overhand loops
Choose two spots on the cord so that the distance between them is the amount by which the cord needs to be shortened
Tie a slip knot (ABOK#529) at each spot. Tie the two knots in the same way, i.e. in the same orientation.
"Same orientation" allows both to be one way or other;
I'm thinking that you might need them to be in particular
orientations to you pulling handle --which you need to say.

Quote
Adjust each knot so that its loop is big enough so that the other knot can pass through it.
But when I continue in your instructions,
I don't see a need for BOTH ... --only for one (one & done)!?

Quote
Identify which of the two slip knots tightens when its free end is pulled and call it knot A.  Call the other one knot B.
?!  They are in same orientation, same knots,
so they should both tighten.  You're doing something
that you've not described, to make this make sense.

Quote
Push knot B and its loop through the loop of knot A and tighten knot A by pulling its free end.
(You can confirm the knot is secure by pulling on both free ends.)
It should be the case the knot B's free end can pull
out its slip-bight/loop, no?!  (A's is toggled by B being
put through it.)

The sheepshank btw can be made more secure by
tying bowlines for its knots.  I.e., form the version
with marlinespike hitches as its knots and then
collapse those knots into the bowlinesque/sheet-bendesque
form --something I'm amazed has not been put into the
literature LONG ago!  (But, then, I'm still puzzled about
how these knots ever worked in Real Life!!)


--dl*
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alpineer

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Re: Sheepshank alternative that remains tied while slack
« Reply #3 on: September 06, 2019, 03:17:19 AM »
If you need your cord to be continuously and quickly adjustable, try a Purcell Prusik Loop.

roo

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Re: Sheepshank alternative that remains tied while slack
« Reply #4 on: September 06, 2019, 03:06:34 PM »
APPLICATION/PROBLEM
I have a tree pruner on an extendable shaft, and it comes with a pull cord with a nice handle on it.
Unfortunately, when the shaft is not fully extended, the cord is too long to use the handle, so I need a way to shorten the cord.
I would like it to be easy to tie, remain tied while slack, be secure under load, and easy to untie.

I have a tree pruner and the old cord handle mechanism never worked right (always slipping halfway through a thick cut), so I removed the handle and replaced it with a short and thick wooden dowel and then tie the quick Pile Hitch for instant attachment wherever I need it:

https://notableknotindex.webs.com/pilehitch.html

It is now a dream to use.  Much simpler.  It also grips the dowel so it doesn't get lost.

If you want to introduce another rope, an ascender knot could be used on the pull cord to allow variable positioning of the handle.  With all the extra short sections of rope I have laying around, I might just do that with my pruner for extra ease of adjustment.
« Last Edit: September 06, 2019, 08:32:33 PM by roo »
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jmlucassen

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Re: Sheepshank alternative that remains tied while slack
« Reply #5 on: September 06, 2019, 07:54:34 PM »
Thanks to you all for your prompt and to the point replies!
And the winner is:
- SS369: slide the handle to where I want it and tie a slip knot below the handle and let the surplus just dangle
Runner up:
- Inspired by Roo: slide the handle to where I want it, form a bight from the surplus, and bring it over the handle, around the standing end and around the end of the handle into a simplified pile hitch.  Advantage: can be done with one hand.

That being said, here is an updated description, along with 4 pictures:

So here's the updated description with pictures:
1. Tie two overhand loops in the cord, in the same orientation*, separated by the distance by which you need to shorten the cord.
2. Identify the loop & knot (A) that can be tightened by pulling the free end, and bring the other knot & loop (B) through it, acting as a toggle.
3. Pull the free end of A to tighten loop A, trapping knot B.  The knot is now ready for use.  Both free ends are equivalent.
4. To untie, try to pull on each end of the middle section: one of these ends will collapse loop & knot B and pull it out of loop A, which can  then be collapsed by pulling its ends.

*Because they are in the same orientation, one free end is "dead" (non-slipping), and the other free end is slipped but will be blocked by a toggle.


I hope this description with pictures is more clear.

I think this knot may be a good choice for my original application if the handle is fixed to the cord and does not slide.
It would compete with the Prusik knot, and I think it may be easier to teach and it is definitely easier to untie.

Feedback & comments welcome.

Dan_Lehman

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Re: Sheepshank alternative that remains tied while slack
« Reply #6 on: September 06, 2019, 09:25:01 PM »
Thanks to you all for your prompt and to the point replies!
And the winner is:
- SS369: slide the handle to where I want it and tie a slip knot below the handle and let the surplus just dangle
I think I deserve an Honorable Mention for coming
up with this idea right behind him --his post coming
as I was typing mine!   ::)

Quote
3. Pull the free end of A to tighten loop A, trapping knot B.
The knot is now ready for use.  Both free ends are equivalent.
Loaded end-2-end, one has a noose nipping a stoppered
line, and all's well.

--dl*
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jmlucassen

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Re: Sheepshank alternative that remains tied while slack
« Reply #7 on: September 06, 2019, 10:46:55 PM »
@Dan_Lehman: Honorable Mention eagerly and humbly granted.

I also liked your suggestion
>> "You could also just tie off the line by taking two bights of it --leaving the slack needed drooping-- and tying, say, a sheet bend / square knot."

I tried it out (pictures 1 and 2), but I found the resulting knots rather bulky, and also (unless properly dressed) prone to coming undone when pulling on the ends, as the bights pulled themselves through.

I then realized the two bights could be used asymmetrically, and I wonder if this is what you had in mind?  (pictures 3 and 4)
- one bight would be used as a single strand, as the bight that starts a a sheet bend or one bight of a square not
- the other bight would be as a double strand, to form the sheet bend or square knot.

Now, for situations where the handle cannot slide on the cord and therefore the cord must be shortened, I find three knots appealing:
- one noose (overhand loop) fed through another as a toggle -- relatively easy to explain to somone who can tie a noose (overhand loop), and easiest to untie
- a sheet bend formed by a bight fed through, around, and over the other bight and tucked under itself -- easy to explain to someone who can tie a sheet bend, and quickest to tie
- a butterfly knot -- secure and compact, and if it needs to be taught, an added bonus is that this is a multi-purpose knot with many benefits

It's nice to have so many options and so many trade-offs  :)

roo

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Re: Sheepshank alternative that remains tied while slack
« Reply #8 on: September 06, 2019, 11:30:36 PM »
Now, for situations where the handle cannot slide on the cord and therefore the cord must be shortened, I find three knots appealing:
- one noose (overhand loop) fed through another as a toggle -- relatively easy to explain to somone who can tie a noose (overhand loop), and easiest to untie
- a sheet bend formed by a bight fed through, around, and over the other bight and tucked under itself -- easy to explain to someone who can tie a sheet bend, and quickest to tie
- a butterfly knot -- secure and compact, and if it needs to be taught, an added bonus is that this is a multi-purpose knot with many benefits

It's nice to have so many options and so many trade-offs  :)
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