Author Topic: Reever and Vice Versa bends  (Read 13342 times)

Groundline

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Re: Reever and Vice Versa bends
« Reply #15 on: December 20, 2020, 06:15:09 PM »
If I were to do this sort of thing often, I would permanently mount the farm jack on something unmovable.

I would do that sooner than later if you plan on pursuing this testing method. Farm jacks are notorious for accidents to person and property when used inappropriately.
Don't look at the Sun.

DerekSmith

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Re: Reever and Vice Versa bends
« Reply #16 on: May 03, 2021, 11:01:39 PM »
Nice work RADNOR, particularly the attention to detail of anchoring the cords by multiple turns around a round bar.

My own test rig used a ten ton hydraulic jack and two 1" round bars. It allowd me to test two knots one against the other and build a ranked table of knot strength.  However, Dan quickly disillusioned me over the absolute strength of a knot as an important factor.  Of much greater concern was knot stability of which slippage in modern cordage is becoming an increasingly important factor in knot design.

You are quite correct in your assertion that the more load a cord can shed on its passage into the knot before it reached a weakening hard turn, the stronger the knot in terms of MBS.  However, there is a contradiction to this position with regards to knot stability of fastness.  To make a knot grip, it must have maximum positive feedback and this is generally achieved by applying the full load directly to the tail end in some form of clamp of nipping loop.  The VV sheds a lot of its input load before it comes to bear upon the opposing (or its own) tail end, so its positive feedback is limited - hence it is prone to slip.

Another aspect of knot stability is cogging.  See the Thief Knot for an example of a structure which in one configuration locks up with negative cogging, yet in its 'trick' configuration, positive cogging has the knot roll itself to nothing.

Derek

NYtarzan

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Re: Reever and Vice Versa bends
« Reply #17 on: August 30, 2021, 03:48:25 AM »
I have a question about one of the variations of the Reever bend.  There is a Wikipedia discussion of the bend: https://en.wikipedia.org/wiki/Reever_Knot

One of the "combinations" is not discussed.  As they say, choosing the standing parts as A-B (or equivalently, B-A) results in the Vice Versa bend.  Choosing A-A results in the Reever bend.

But what about choosing B-B?  On page 54 of Harry Asher's book "The Alternative Knot Book" he says of the Simple Simon under bend "At the intersection, the light end (the tail; my comment) passes beneath the standing part; the nip thereby imparted to it considerably increases security..."

Examining the difference between the A-A choice and the B-B choice in the Wikipedia article, it seems to me that the same comment applies to the B-B choice.  When B-B are chosen to be the standing parts, the tails pass beneath the standing parts in the nips.  Wouldn't this be the preferred configuration?

I haven't found any discussion of this difference between the standard Reever bend (the A-A choice) and the B-B configuration on the forums, but I haven't read every post yet.  Can anyone tell me if there has been discussion of this on the forums, and if the B-B configuration has a name of its own?  If it hasn't been named yet, I propose that a name should be invented.

Here are a couple of images of the front and back of the B-B configuration (unnamed top bend in the images) and the A-A (Reever) configuration (bottom in the images).




How do you tie Quadnip knot? Could you upload some pictures, it looks sick and strong!!

agent_smith

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Re: Reever and Vice Versa bends
« Reply #18 on: August 30, 2021, 04:16:01 PM »
Hello 'NYtarzan' (nice name by the way),

'Radnor' does not appear to have been active in recent times...
But he did post an image in reply #3 and the basic concept is derived from his reply #5.

Some commentary: (not directed at 'NYtarzan')
The discussion re the various loading profiles came at a time when some concepts were still evolving and a work-in-progress.
Harry Asher broke some new ground with his discussions on loop chirality and also the fact that all 'bends' have corresponding eye knots (4 in fact - within a chiral domain).
However, Asher did not fully explore and flesh out his ideas... but he steered the ship on the right heading.

The attempts to assign different names to the 'Reever' based on choice of SParts reminds me of #1411 F8 bend (refer image below).
The same concept applies - in that there is a choice of loading profiles.
But does that choice disturb the title of the 'bend'?
Topologically, they are all the same knot.

In my view, regardless of which combination of SParts are chosen - it is still a #1411 F8 bend (the title of the knot does not change).
Does that analogy also apply to the 'Reever bend'? That is, do we set aside the Reever as being 'special' in some way - and that choice of SParts does disturb the title?
In my view, this line of thinking has historical roots - where Asher was likely first to bring it to peoples attention - and in more recent times, knot tyers may still be influenced by past thinking?

All knots have mirror versions - should we assign different names to the mirror versions?
That is, take any knot and hold it adjacent to a plane mirror.
The reflected image will be the inverse - but it is still the same knot.

I would also comment that there is no peer reviewed testing using the scientific method (with a 'control') of the various loading profiles of either the 'Reever' or #1411 F8 bend.
And the discussion re 'dyneema' always appears to invoke cord of an extremely slippery nature.
And yet, I can go into my local boating hardware and purchase 'dyneema' cord - which has a core + sheath design and does not slip.
Probably need to properly specify exactly what type/model of 'dyneema' is being imagined - instead of just saying 'dyneema'.

I would also comment that testing a knots MBS yield strength is mostly irrelevant.
Unless the t4ester is specifically investigating a geometric change in a knot relative to a 'control'.
In life critical applications, the properties of security, stability and jam resistance are of greater importance.
« Last Edit: September 01, 2021, 04:41:54 AM by agent_smith »

NYtarzan

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Re: Reever and Vice Versa bends
« Reply #19 on: August 30, 2021, 07:32:51 PM »
Hello 'NYtarzan' (nice name by the way),

'Radnor' does not appear to have been active in recent times...
But he did post an image in reply #3 and the basic concept is derived from his reply #5.

Some commentary: (not directed at 'NYtarzan')
The discussion re the various loading profiles came at a time when some concepts were still evolving and a work-in-progress.
Harry Asher broke some new ground with his discussions on loop chirality and also the fact that all 'bends' have corresponding eye knots (4 in fact - within a chiral domain).
However, Asher did not fully explore and flesh out his ideas... but he steered the ship on the right heading.

The attempts to assign different names to the 'Reever' based on choice of SParts reminds me of #1411 F8 bend (refer image below).
The same concept applies - in that there is a choice of loading profiles.
But does that choice disturb the title of the 'bend'?
Topologically, they are all the same knot.

In my view, regardless of which combination of SParts are chosen - it is still a #1411 F8 bend (the title of the knot does not change).
Does that analogy also apply to the 'Reever bend'? That is, do we set aside the Reever as being 'special' in some way - and that choice of SParts does disturb the title?
In my view, this line of thinking has historical roots - where Asher was likely first to bring it to peoples attention - and in more recent times, knot tyers may still be influenced by past thinking?

All knots have mirror versions - should we assign different names to the mirror versions?
That is, take any knot and hold it adjacent to a plane mirror.
The reflected image will be the inverse - but it is still the same knot.

I would also comment that there is no peer reviewed testing using the scientific method (with a 'control') of the various loading profiles of either the 'Reever' or #1411 F8 bend.
And the discussion re 'dyneema' always appears to invoke cord of an extremely slippery nature.
And yet, I can go into my local boating hardware and purchase 'dyneema' cord - which has a core + sheath design and does not slip.
Probably need to properly specify exactly what type/model of 'dyneema' is being imagined - instead of just saying 'dyneema'.

I would also comment that testing a knots MBS yield strength is mostly irrelevant.
Unless the t4ester is specifically investigating a geometric change in a knot relative to a 'control'.
In life critical applications, the properties of security, stability and jam resistance are of greater importance.
That's why i'm concerned, i know there's nothing better than splicing dyneema/technora/aramid cord
but still the last version of this specific knot looks promising!!

 

anything