Author Topic: self locking reef knot?  (Read 9859 times)

kieranbarnard

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self locking reef knot?
« on: September 23, 2013, 09:00:44 PM »
This is my first post so I hope this is not a daft question... 

I'm involved in a project and am not a knotting expert so I hope someone will be able to help... Is it possible to tie a reef knot and a locking knot (to lock the reef) at the same time i.e. with one pull simultaneously at either end?

I want to be able to tighten a knot around a central object by pulling at both ends but i don't want the knot to come loose - perhaps a reef is not the best knot for this purpose? perhaps this isn't possible at all without at least a half hitch.  I just want the application of the knot to be as simple as possible.

I'd be grateful for any advice.

Thanks
Kieran 
« Last Edit: September 23, 2013, 09:01:37 PM by kieranbarnard »

Sweeney

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Re: self locking reef knot?
« Reply #1 on: September 23, 2013, 09:36:15 PM »
Welcome to the forum Kieran - don't worry about asking daft questions (which incidentally yours isn't) just try and give as much detail as you can - a photo or simple diagram or drawing will make it easier to give you specific advice. For example if the knot is bearing down on a convex surface then a constrictor knot may be ideal but this won't work against a flat surface or across a gap - there are other knots for this (you may find the discussion at http://igkt.net/sm/index.php?topic=4609.0 helpful).

Barry

kieranbarnard

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Re: self locking reef knot?
« Reply #2 on: September 23, 2013, 10:18:24 PM »
Thanks so much for your reply Barry,

The reason I was drawn to the reef knot is that you can have a central loop, the diameter of which is adjustable ie. gets smaller as you pull at either end. I want to be able to put a loop over a central object and pull at either end until it is tight around the object. My concern is that a reef may unravel.  The constrictor knot looks much better but I'm not sure it will be as adjustable. The knot would indeed bear down on a convex surface. 

I hope that makes sense. If not I will take some photos tomorrow.

Kieran


WebAdmin

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Re: self locking reef knot?
« Reply #3 on: September 24, 2013, 05:54:58 AM »
Hi Kieran, welcome to the Forum.


There was also a set of posts from some months ago that drew attention to medical knots posted in copyrighted material on another website.  I need to be sifting through on my laptop to find the relevant information for you, but there may be something helpful in some of that information: as medical knots are out of my experience, I can't say for sure.


Because the material was copyright we weren't able to retain it here, but we can refer you on to the original sources :)


I hope to post again within 24 hours with the links.


Regards
Glenys
Lesley
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Luca

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Re: self locking reef knot?
« Reply #4 on: September 24, 2013, 11:00:12 AM »
Hi Glenys and Kieran,

Glenys, maybe you're referring to this thread:

http://igkt.net/sm/index.php?topic=4107.0

Kieran,I would not miss to mention to you also the Gleipnir/Gleipner knot ( http://daveroot.atspace.cc/knots/Knots_Miscellaneous.htm#Gleipner ), you can find a lot of information and images relating to it and to other variations also with the search function of the forum.

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Sweeney

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Re: self locking reef knot?
« Reply #5 on: September 24, 2013, 11:35:45 AM »
The reason I was drawn to the reef knot is that you can have a central loop, the diameter of which is adjustable ie. gets smaller as you pull at either end. I want to be able to put a loop over a central object and pull at either end until it is tight around the object. My concern is that a reef may unravel.  The constrictor knot looks much better but I'm not sure it will be as adjustable. The knot would indeed bear down on a convex surface. 
Kieran

The constrictor will tighten and remain locked but tightens like a ratchet - only one way - so it is adjustable from a large loose loop to an extremely tight loop around the object simply by pulling both ends (you can use pile hitches around say a couple of screwdrivers to get it really tight but at the risk of damaging the object around which it is tied) but it is very difficult to loosen unless the end is tucked to slip it (which won't affect it's ability to grip). It all depends on what you mean by "adjustable" - you can only adjust the first overhand knot in a reef knot the second locks the first in place and the constrictor is mechanically similar. However depending on your application the various arthroscopic knots and the Gleipnir (and its variations) may offer a better solution as Glenys and Luca have suggested.

Barry

Barry

kieranbarnard

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Re: self locking reef knot?
« Reply #6 on: September 24, 2013, 12:51:48 PM »
Hi Barry, Glenys and Luca,

Thank you so much for you advice and expertise which has been really very helpful.

I've been practising with the constrictor knot and it's definitely the best option as it is simple and the hold is very tight. I only need the knot to adjust one way, ie. from large diameter to small and I would not need to loosen.  The only issue now is that the constrictor does not hold it's shape: the two loops come apart when you let them go.  What I really need is a constrictor type knot that will hold it's shape and will tighten as the two ends are drawn apart simultaneously in opposite directions. does this exist?

Kieran

knot4u

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Re: self locking reef knot?
« Reply #7 on: September 24, 2013, 01:04:03 PM »

Gleipnir X

knot4u

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Re: self locking reef knot?
« Reply #8 on: September 24, 2013, 01:11:37 PM »
Strangle Knot
Blake's Hitch Reversed
ABOK #1674

WebAdmin

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Re: self locking reef knot?
« Reply #9 on: September 24, 2013, 01:33:56 PM »
Hi Luca,


Yes, that's one of the posts.  I thought they'd all been removed.  It's not the links, or the discussions, but the copying of the images that was the reason for the copyright-owner's request. 


Unfortunately, it has been a rather difficult year for me, and I have not been able to set aside devoted time to be able to cut and paste and repost without the images but with an explanation of what's been omitted and why, and where to go and how to see the images (you can look, but they'd like you to pay for the privilege of using them).  So, Kieran, this post may give you an idea of the sort of thing I was looking to direct you to, and a search for arthroscopic knots on the net will lead you to source literature :)  If not useful now, then maybe sometime in your future career :)


Regards
Glenys
Lesley
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kieranbarnard

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Re: self locking reef knot?
« Reply #10 on: September 25, 2013, 07:16:53 AM »
Knot4U - thanks so much for you suggestions.  I've had a try of each but I'm not convinced that any of them will hold their shape.  What I'm after is a contrictor type knot that will hold it's shape (without biting onto anything) and will go from large diameter to small diameter as you pull the opposing ends. I'm beginning the think that such a knot doesn't exist...  >:(

Glenys - thank you for your suggestions but I can't find any arthroscopy knots that fulfil the purpose above.

Kieran

Sweeney

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Re: self locking reef knot?
« Reply #11 on: September 25, 2013, 12:18:25 PM »
Knot4U - thanks so much for you suggestions.  I've had a try of each but I'm not convinced that any of them will hold their shape.  What I'm after is a contrictor type knot that will hold it's shape (without biting onto anything) and will go from large diameter to small diameter as you pull the opposing ends. I'm beginning the think that such a knot doesn't exist...  >:(

I think I can now see what you want - in effect a bend which forms a sling rather than a binder, but you want a bend which tightens from both ends so the cord is not required to slide around the object (as would be the case with an adjustable loop). Have you tried the Surgeon's knot (aka Ligature knot)? This is in effect a Reef knot with an extra over-and-under in forming the first half knot. The only slight drawback is that you would need to make the loop slightly smaller than its final size because to tighten the knot properly you pull both of tne ends then the 2 legs of the loop (n opposite directions) to set the knot - which is a lot more secure than a Reef knot. When set properly the knot rolls into its characteristic shape. The amount of slack in the loop created by tightening is not great - a couple of experiments with your cord should give you a good indication of how much.

There is a simple way to lock a Reef knot but I don't think it would be easy in the situation I assume you have. Take the 2 ends and holding the knot flat tuck them through the centre of the knot with 2 parts above and 2 parts below (have a look at the third picture in this http://www.igkt.net/beginners/solomon-man.php and imagine ends A and B tucked in the way shown).

Barry

Dan_Lehman

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Re: self locking reef knot?
« Reply #12 on: September 25, 2013, 03:58:51 PM »
... I'm not convinced that any of them will hold their shape.
What I'm after is a contrictor type knot that will hold it's shape
(without biting onto anything)
and will go from large diameter to small diameter as you pull the opposing ends.
I'm beginning the think that such a knot doesn't exist...  >:(

Kieran, then we will have to invent it!   ;)

It's not clear what you mean by "hold its shape":
with the constrictor e.g., (or clove), one cannot
simply hold the ends and remove the object and
retain the knot --true.  But what exactly is the sort
of changing-of-object(&dia.) that you expect to do?

Here's another idea : form a Prusik hitch (around air,
or a small hollow cylinder); send its ends apart from
each other around an object,
and pass them through the hitch (if a small hollow
cylinder is holding the Prusik's form, pass one end
through and then remove the cylinder, then pass
the other end through in the opposite direction
(of course)).  You'll need to work the knot tight
around the ends --really work it : the resistance
or any expansion of the bound object will pull
the coil-halves of the knot apart (and tighten
them to grip), but the pulling on ends to set
the structure newly tight to a smaller object
will pull knot-halves together,
so there is this sort of *looseness/give* to deal
with, best done by tightly setting original.

Now, you end up with two wraps around your
"central object" (as you have with the above),
but these "loops" shouldn't so readily fall apart,
and the knot will hold shape around the ends.
(I should say that you end up with something
akin to the Gleipnir variation that Knot4U showed,
but with a full knot nipping parts in the center
vice the simple turn; it is this full knot that will
hold its form, but I'm not sure whether that
fully meets your concerns.)

There could be added cleverness to the Prusik
to make it so that the loops don't cross each other
in surrounding the central object.  (The P. can
be seen as an extended cow hitch and you can
use instead a clove hitch orientation of those binding
coils which might facilitate keeping each loop/wrap
on one side of the other.)


--dl*
====
« Last Edit: September 25, 2013, 04:17:31 PM by Dan_Lehman »

knot4u

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Re: self locking reef knot?
« Reply #13 on: September 25, 2013, 06:37:54 PM »
I think we need more explanation, or you're going to have to deal with people guessing. Your requirements don't seem difficult. Provide a diagram if you can. Based on your description, it seems like I could solve the problem with most of the knots presented here.
« Last Edit: September 25, 2013, 06:40:43 PM by knot4u »

Luca

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Re: self locking reef knot?
« Reply #14 on: September 25, 2013, 10:56:50 PM »
Hi Dan and knot4u,

It may be that this is so?(There is also the handle for easy transportation of the object!)

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