Author Topic: Double Torus Stopper  (Read 3834 times)

SS369

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Double Torus Stopper
« on: February 23, 2014, 04:53:22 PM »
In the spirit of interesting exchanges, I have been encouraged to offer this modification of the Whale Bend.

Considering that the Ashley (#526)/Oysterman's stopper knot presents one of the best faces as a stopper, with three lobes to disperse the load against the surface through which the rope passes, it drove my mind to use the interesting and convoluted configuration of the Whale stopper presented by Xarax, except with trefoils instead of overhands.

And though the Whale stopper perhaps does an better action of locking the part going through the first overhand (Standing part side), the Double Torus stopper presents (a trefoil) more load bearing contact.
Both draw up nicely as described in http://igkt.net/sm/index.php?topic=4802.msg31210#new with the Whale being a bit more compact.
Tied in 3mm Dyneema, both look to be able to resist slippage failure.

A quatrefoil - cinquefoil may be taking this a bit far.  :)

SS
« Last Edit: February 23, 2014, 11:47:02 PM by SS369 »

xarax

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Re: Double Torus Stopper
« Reply #1 on: February 23, 2014, 06:54:56 PM »
  There are three variations on ( the same ) theme : The Double Torus stopper - in a way, the simpler one of the three -,  the Whaler s stopper, and yet another stopper, to be named.
  If you take a short piece of string, and you tie one overhand knot and one underhand knot on it, the one after the other, and then you place those two over/under-hand knots, in their flat, Pretzel-like form, belly-to-belly to each other, with the piece of the string in between them making this nice S-shaped path, and if then you tuck the two free ends of the string through the openings of those two Pretzel-shaped knots, you get one of those three stoppers. If you tuck the ends through the central opening, you get the Double Torus stopper. If you tuck them through the openings which are nipped directly by the Standing Parts first curves, you get the Whaler s stopper. If you tuck them through the third opening of the Pretzel-shape knots, you get a third stopper.
  Starting from this third stopper, I had not preferred it because the Standing part s first curve is too sharp, a U-turn around one, only, rope diameter - and this is due to the fact that the tail does not pass through this opening, so, without enough core material to be encircled there, it can not but remain very narrow. I thought that it would be too risky, re. strength, to have so sharp a first curve, in a place of the Standing Part where the local loads are still at the 100% of the total.
   Now, regarding the Double Torus stopper, I think that any line that penetrates the central opening of a Pretzel-like overhand knot is not nipped as hard as if it would had been, had it penetrated any of the other two openings. This opinion is based on observations in the case of the "Link" bowlines, where I have seen that the central opening, although it might seem the most "natural" way to make the tail dive in, it is not the optimum. Especially with stiff ropes, the surrounding material tends to "protect" the penetrating line, rather than choke it, because it plays the role of a shield : the friction between the inter-weaved lines swirling around absorbs a substantial amount of the nipping forces that otherwise would reach and nip the penetrating line. As I said in other similar occasions, the central opening is not such a bad black hole we think it is : it is more like the eye of the cyclone, a relatively calm place in the centre of the surrounding mess.
   So, I had preferred, as the last location where the Tail would be nipped, to drive it through the other opening, and tie the Whaler s stopper, instead of the Double Torus stopper. There, in direct contact to the Standing Part s first curve - in fact, right under it -, it is immobilized as much as it could be. And I prefer the "last line of defence" against slippage be the stronger one, as every middle-ages military engineer worth its salt would have done, when he was building a medieval castle !  :)
   Tail end inside /under the Standing Part s first curve, and not though the central opening of the overhand knot, that is what separates the Whaler s from the Double Torus stopper ! Let the best stopper win ! Prepare for the fight !  :) Dyneema lines and rope pulling devises, and enough comfortable chairs for the betting spectators. If we built it, they will come.
   
« Last Edit: February 23, 2014, 07:35:40 PM by xarax »
This is not a knot.

SS369

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Re: Double Torus Stopper
« Reply #2 on: February 24, 2014, 12:02:31 AM »
Thanks for your input xarax.

I agree in part, with your idea of first defense/last defense, but I don't necessarily agree that it is the only way to address a stopper using the slippery Dyneema. The first nip with the overhand is going to do little by way of guarding against or restricting slippage with this material. You can not even pinch it between your fingers or wrap it around your hand and hold it from slipping even with modest tension, as you can do with other cords and ropes.
And so the first contact area of the stopper against the hole's surround has a better and/or additional purpose.

The ABoK 526/Oysterman's stopper assembly, as presented, provides a little bigger surface area patch with its three lobes against the contact area around the hole that the rope goes through. It acts as a washer (nut and bolt variety) per se. I feel that in this configuration the second stopper of the combo will be adequately secure to resist the slippery rope. The central position in the nub looks to balance the force a bit more.

SS

P.S. Thank you for the KM graphic!  ;)
« Last Edit: February 24, 2014, 12:04:21 AM by SS369 »

xarax

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Re: Double Torus Stopper
« Reply #3 on: February 24, 2014, 02:11:08 AM »
...provides a little bigger surface area patch with its three lobes against the contact area around the hole that the rope goes through. It acts as a washer (nut and bolt variety) per se.

   The Double Torus has a flatter bottom, and sits better on it, that is true. Moreover, if we examine them as pure stoppers ( not as a "halves" of a Fisherman s -like sliding / interpenetrating bend ), the Standing part of the Double Torus stopper is less offset than the Standing part of the Whaler s stopper, and that is an advantage.   
   I believe the difference between the two knots is due to the conditions they were met in the first place.
   I stumbled on the Whaler s stopper, when I tried to enhance the central hook-to-hook arrangement of the ex-tails in Dan Lehmans enhanced, hooked and blooded Fisherman s knot, and I realized that a more convoluted entanglement of those ex-tails would nt be much different, regarding complexity, from two separate overhand knots, placed in the same row with the parent ones. After all, Dan Lehman hooked the ex-tails in the middle of the two halves of a Fisherman s knot, for no other reason than to convolute the parent Fisherman s knot more, by adding U turns in the paths of the Standing parts - those hooks are squeezing, they are not pulling each other. So, I imagined Dan Lehmans two-and-two halves overhand knots in a raw, i.e., almost three knots in a raw, become four knots in a raw, i.e., two pairs of two overhand knots in a raw. All this time, I was thinking of knots that can be used as the halves of an enhanced Fisherman s like sliding / interpenetrating knot, not of knots that can be used as pure stoppers. I tried to use the openings of the overhand knots that seemed to me be most efficient in nipping the Tail ends, those that offered a direct contact with the other link s fist curves, and I reserved the central openings  ( which, as I had explained, are not very effective in choking any line that penetrates them ), for the passage of the other link s Standing Parts. I had not paid any attention to the form of the "base" of the two halves, because I though that, by siting on each other s bottom ( and NOT on a flat surface ), they will have as ample a support as they will need. 
  You met the Double Torus by spotting the possible disadvantages of the Whaler s stopper, as a stopper, not as a half of an enhanced hooked and blooded Fisherman s knot. So, you compared it, right from the start, to other stoppers, and you thought of ways to improve its "base" and eliminate any problems it might present with its offset Standing End. In other words, you had searched for a better stopper, not a better half of a Fisherman s-like sliding / interpenetrating knot, so you chose the central openings of the overhand knots for the Standing and Tail ends. You imagined that, this way, the first overhand knot would present a more stable and better balanced "base" for the stopper to sit on.
   It may be the case that a better stopper makes a better half of a Fisherman s -like knot - but it also may be not ! The overhand knots in a properly tied Fisherman s knot do not have "bases' perpendicular to the axis of the knot. They kiss each other almost perfectly, and they benefit from the wide and balanced area of mutual contact, although they do not sit on each other s bottom the way they would sit on a flat surface.
   If those stoppers are used as halves of Fisherman s like bends, they may behave differently, than if they are used as pure stoppers. KnotGod knows what will happen between four overhand knots in a row, squeezed upon each other by the huge forces a Dyneema line can withstand ! Only tests can tell if those stoppers will hold ( I hope they will...), and, if they do, which will break latter, in a higher percentage of MBS of the unknotted line, than the other.
     
« Last Edit: February 24, 2014, 02:15:06 AM by xarax »
This is not a knot.

SS369

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Re: Double Torus Stopper
« Reply #4 on: February 24, 2014, 03:36:52 AM »
Yes, the premise was for a stopper, then a secured tail. I got the idea furthered along by the Whale stopper.
I like the idea of a knot component that cinches down on the respective parts better than what the DblTorus does.

So that makes me wonder about a "marriage" of the two. Where the stopper face is an ABok 526 and the tail side (last defense) is an overhand, configured as these have been.

I haven't the time to tangle it tonight, so perhaps you'll beat me to it.  ;)

Also, one can take the returning tail, before it goes through the tail side overhand and wrap it around the central body a turn or two, then thread it into the opening of the overhand. This I have done already.
Fills the knot out a bit too and may influence breakage reduction with cushioning.

SS

xarax

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Re: Double Torus Stopper
« Reply #5 on: February 24, 2014, 03:50:01 AM »
one can take the returning tail, before it goes through the tail side overhand, and wrap it around the central body a turn or two, then thread it into the opening of the overhand. This I have done already.

  So, you have gone fishing again, already !  :)
  Those stoppers are at the limits of practical knots, regarding how convoluted they are - add one whole turn or two around a segment of them, and you will need no harpoon to catch a whale !  :)
This is not a knot.

SS369

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Re: Double Torus Stopper
« Reply #6 on: February 24, 2014, 03:55:43 AM »
one can take the returning tail, before it goes through the tail side overhand, and wrap it around the central body a turn or two, then thread it into the opening of the overhand. This I have done already.

  So, you have gone fishing again, already !  :)
  Those stoppers are at the limits of practical knots, regarding how convoluted they are - add one whole turn or two around a segment of them, and you will need no harpoon to catch a whale !  :)

We're fishing with Dyneema mind you.  ;)

Maybe Moby will choke on it....

SS

xarax

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Re: Double Torus Stopper
« Reply #7 on: February 24, 2014, 04:29:02 AM »
   I had always hoped that we will find decent knots to do this dirty job, not very different from the knot s we already use on "ordinary" material, based on the same logic, mechanisms and patterns - perhaps only re-tucked once, or enhanced with any of the 4 other simple ways mentioned at (1) and elsewhere. I have not abandoned this hope yet, because the range of knots that have been tested to this day is not enough to persuade me we will need radically new, and much more convoluted knots. We know that many people, including knot tyers, have difficulties to understand and remember even the simple and few practical knots we already have - so I wonder, who is going to learn much more convoluted knots ? There would be some self-appointed "specialists" who will declare that knots are impossible or dangerous on Dyneema, just to relieve themselves from the burden of having to learn any of them - and they will come up with an expensive mechanical devise, a super-super-glue or an automatic splicing machine, then they will write a relevant dumb article on Wikipedia, and the convoluted knots on Dyneema will be forgotten / prohibited for ever...

1. http://igkt.net/sm/index.php?topic=4777.msg31038#msg31038
This is not a knot.

SS369

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Re: Double Torus Stopper
« Reply #8 on: February 24, 2014, 03:12:22 PM »
   I had always hoped that we will find decent knots to do this dirty job, not very different from the knot s we already use on "ordinary" material, based on the same logic, mechanisms and patterns - perhaps only re-tucked once, or enhanced with any of the 4 other simple ways mentioned at (1) and elsewhere. I have not abandoned this hope yet, because the range of knots that have been tested to this day is not enough to persuade me we will need radically new, and much more convoluted knots. We know that many people, including knot tyers, have difficulties to understand and remember even the simple and few practical knots we already have - so I wonder, who is going to learn much more convoluted knots ? There would be some self-appointed "specialists" who will declare that knots are impossible or dangerous on Dyneema, just to relieve themselves from the burden of having to learn any of them - and they will come up with an expensive mechanical devise, a super-super-glue or an automatic splicing machine, then they will write a relevant dumb article on Wikipedia, and the convoluted knots on Dyneema will be forgotten / prohibited for ever...

1. http://igkt.net/sm/index.php?topic=4777.msg31038#msg31038

I believe there are knots for Dyneema ( and what material is eventually coming as well (nano-carbon fibers)) down the line.
By the nature of these slippery materials,  my opinion is the knots will have to be more complex than the simple ones that work for normal ropes. That is knots that don't slip (too much) and are secure (enough), and that don't induce an unacceptable reduction in line strength, and can be untied (if necessary).

By others, it has been claimed that simple fixes to old knots doesn't necessarily work, e.g., an overhand stopper on a tail. I can't dispute this personally and it seems to go against my logic. But, that claim is there.

So if we can design for simplicity (subjective), though it may well be more complicated and convoluted, that is what it will take to survive the acid test of these new materials.

Not everyone will have the opportunity or need to use Dyneema, etc.,  but it is there, challenging.

And some people just like to climb mountains, because they can....
And some won't...

SS