International Guild of Knot Tyers Forum

General => Practical Knots => Topic started by: Seaworthy on June 29, 2014, 01:16:03 PM

Title: Water Zeppelin
Post by: Seaworthy on June 29, 2014, 01:16:03 PM
From what I have read so far, the Zeppelin with the thinner line given one more final tuck (no one has come up with a name yet, do we call it the 'Asymmetric Zeppelin' or '1.5 Zeppelin' or 'Semi Double Tucked Zeppelin'?) seems the best relatively easy way known to join line of different diameter used when sailing (all but slippery stuff like unsheathed Dyneema).

(BTW, I vote for 'Semi Tucked Zeppelin', making the version with both tails double tucked the 'Tucked Zeppelin'. This leaves the terms 'Semi Double Zeppelin' and 'Double Zeppelin' free for doubling the initial loops rather than the final tucks - we need 4 new names for these 4 'new' versions that were discussed here in 2010.)

I think an initial double loop of the thinner line may be even better (ie a Semi Double Zeppelin), or perhaps both a double loop a double tuck of the thinner line, but only load tests can confirm or deny that.

Now leading on from this (my thoughts keep returning to Dyneema), what do you think of making the doubling of the initial loops of the 6 and 9 clove hitches rather than simple doubles? Imagine the difference between a Double Bowline and a Water Bowline. That is what I propose trying for the Zeppelin. 'Water Zeppelin' seems an appropriate name.

This is how the Water Zeppelin looks from the two sides when loose and dressed (line is old stiff stuff so it does not tighten easily):
Title: Re: Water Zeppelin
Post by: Seaworthy on June 29, 2014, 01:17:39 PM
And this is how the Water Zeppelin looks in Dyneema. The two lines are slightly different in diameter, so it is a little uneven, but I think this bend is quite elegant and more importantly, promising:

Any comments?
Title: Re: Water Zeppelin
Post by: xarax on June 29, 2014, 03:47:20 PM
   The Zeppelin bend looks "simple", but it is not - and that may explain why it was tied only "recently" ( taking into account the fact that knots were one of the first inventions of our ancestors ) - and why the almost unique, among the bends, way it works, is not understood, even by knot tyers who claim they are "familiar" :) with it, and promote/advertize its use. 
   One of the most subtle things is the way it achieves its "balance" : even after heavy loading, the pair of the Tail Ends ( the "pivot" of this rope-made hinge ), remains  perpendicular to the axis of the knot, so the forces that are applied on them are sheer forces mostly, not friction forces. The first curves of the Standing parts, although they are not "hooked" within each other ( as it happens in most other bends, and in the deceivingly "similar" Hunter s bend, for example ), they are adjacent and parallel to each other, and aligned to the axis of the knot in an almost perfect way. This does not happen in the case of the falsely tied Zeppelin bend, which, although it is more symmetric, it is a very poor bend.
   One can find many things about the true Zeppelin knot, the Zeppelin bend, and its evil imposters in this Forum - but knotting myths are not extinguished overnight, and because knots, fortunately, seldom kill their users, they will continue to be around us for a looong time.

   When I see a knot that is supposed to be some variation or implementation of the Zeppelin bend, the first thing I look is the angle between the Standing and the Tail Ends : if this angle is not the right angle, it is not a right angle  :), so the supposedly Zeppelin-like knot is determined to work differently than the genuine Zeppelin knot, the Zeppelin bend - and, most probably, it works much worse.
   There have been some attempts ( some very successful, and some not so ) to other, Zeppelin-like bends and loops.(1)(2)(3)(4)( I do not consider this evil imposter of the Zeppelin-like family of knots, the fake, so-called "Zeppelin loop", as a Zeppelin-like knot, of course ! )( For some comments on why some such bends work better than some others, see (2). The possible variations of a "Double" Zeppelin bend, have also been exploited (5)(6).

1. http://igkt.net/sm/index.php?topic=4090
2. http://igkt.net/sm/index.php?topic=4090.msg30245#msg30245
3. http://igkt.net/sm/index.php?topic=4095.msg24546#msg24546
4. http://igkt.net/sm/index.php?topic=4095.msg24590#msg24590
5. http://igkt.net/sm/index.php?topic=1980
6. http://igkt.net/sm/index.php?topic=4777.msg31022#msg31022

   The bend shown here may perhaps be improved a little bid, if the two "Clove hitches" ( which, in fact, are not "Clove hitches" any more, but just pairs of half hitches ) are placed in a way that would enable, 1 : the continuations of the Standing Ends to be better aligned and closer to each other, and, 2 : the axis of "tube" surrounding the pair of the Tails to remain, in relation to the axis of the knot, in an angle closer to the right angle ( i.e., closer to the perpendicular to this axis ). Let us call as A1 and A2 the two nipping loops of the one "Clove hitch", and B1 and B2 the two nipping loops of the other. If their order along the axis of the "tube" is not A1, A2, B2, B1, as it is now, but A1, B2, A2, B1 instead, or even A2, A1, B1, B2,  the situation improves - because the A1 and the B1, and the continuations of the corresponding Standing Ends, will come closer to each other, and so they will be better aligned along the axis of the knot. 
Title: Re: Water Zeppelin
Post by: Seaworthy on June 29, 2014, 08:38:18 PM
   One of the most subtle things is the way it achieves its "balance" : even after heavy loading, the pair of the Tail Ends ( the "pivot" of this rope-made hinge ), remains  perpendicular to the axis of the knot, so the forces that are applied on them are sheer forces mostly, not friction forces.
..........
   When I see a knot that is supposed to be some variation or implementation of the Zeppelin bend, the first thing I look is the angle between the Standing and the Tail Ends : if this angle is not the right angle, it is not a right angle  :), so the supposedly Zeppelin-like knot is determined to work differently than the genuine Zeppelin knot, the Zeppelin bend - and, most probably, it works much worse.
   There have been some attempts ( some very successful, and some not so ) to other, Zeppelin-like bends and loops.(1)(2)(3)(4)( I do not consider this evil imposter of the Zeppelin-like family of knots, the fake, so-called "Zeppelin loop", as a Zeppelin-like knot, of course ! )( For some comments on why some such bends work better than some others, see (2). The possible variations of a "Double" Zeppelin bend, have also been exploited (5)(6).

1. http://igkt.net/sm/index.php?topic=4090
2. http://igkt.net/sm/index.php?topic=4090.msg30245#msg30245
3. http://igkt.net/sm/index.php?topic=4095.msg24546#msg24546
4. http://igkt.net/sm/index.php?topic=4095.msg24590#msg24590
5. http://igkt.net/sm/index.php?topic=1980.msg13796#msg13796
6. http://igkt.net/sm/index.php?topic=4777.msg31022#msg31022

Many thanks for the feedback and links. A huge amount of interesting reading there.

Not sure if I agree entirely with all the comments, but I admit I have little experience and have an awful lot to learn. In these early stages of learning, it seems to me that it is important for the knot not being stressed by having any of the components pulled apart when load is applied that is very important, rather than where the angle the tail ends end up.

   The bend shown here may perhaps be improved a little bid, if the two "Clove hitches" ( which, in fact, are not "Clove hitches" any more, but just pairs of half hitches ) are placed in a way that would enable, 1 : the continuations of the Standing Ends to be better aligned and closer to each other, and, 2 : the axis of "tube" surrounding the pair of the Tails to remain, in relation to the axis of the knot, in an angle closer to the right angle ( i.e., closer to the perpendicular to this axis ). Let us call as A1 and A2 the two nipping loops of the one "Clove hitch", and B1 and B2 the two nipping loops of the other. If their order along the axis of the "tube" is not A1, A2, B2, B1, as it is now, but A1, B2, A2, B1 instead, or even A2, A1, B1, B2,  the situation improves - because the A1 and the B1, and the continuations of the corresponding Standing Ends, will come closer to each other, and so they will be better aligned along the axis of the knot. 

I will have a play in the next few days.
Title: Re: Water Zeppelin
Post by: roo on June 29, 2014, 09:35:18 PM
Now leading on from this (my thoughts keep returning to Dyneema), what do you think of making the doubling of the initial loops of the 6 and 9 clove hitches rather than simple doubles? Imagine the difference between a Double Bowline and a Water Bowline. That is what I propose trying for the Zeppelin. 'Water Zeppelin' seems an appropriate name.

This is how the Water Zeppelin looks from the two sides when loose and dressed (line is old stiff stuff so it does not tighten easily):
Aside from the difficulty in tying things correctly, I find that I'm having a difficult time trying to draw things up into a compact form.  I feel like I'm trying to snug up a Turk's Head.

As an aside, xarax's favorite word is "fake", yet he fails to see the irony in his fake analysis based on looks (as if he were reading tea leaves) rather than reproducible tests of relevant knot properties.
Title: Re: Water Zeppelin
Post by: xarax on June 30, 2014, 03:21:56 AM
it is important for the knot not being stressed by having any of the components pulled apart when load is applied that is very important, rather than where the angle the tail ends end up.

  In a 2-knuckle / 1-pin hinge, if you pull the 2 knuckles towards opposite directions, in order to keep the hinge in one piece, you want the axis of the pin to be ( and to remain ! ) at a right angle ( = perpendicular ) to the axis of the pull - otherwise the knuckles will slide on the cylindrical surface of the pin, they will move apart from each other, and the hinge will be separated / tore apart, in three pieces !  :). Even if there are some considerable friction forces in between the knuckles and the pin, if the pull is strong enough, they will not be able to prevent this sliding.
   Now, in the genuine Zeppelin knot, the Zeppelin bend, we have a two-part pin ( made by the pair of the two adjacent Tail Ends ), and each of those parts is "welded"/connected, at its one end, to the corresponding knuckles ( made by the pair of the two adjacent first curves of the two Standing Parts ). So, if the axes of the pins ( Tail Ends ) are not perpendicular to the axis of the pull, the knuckles (  first curves of the Standing parts ) will be free to move apart from each other, dragging the corresponding "welded"/connected to them half-pins along them - and no nipping/gripping of those pins by the knuckles, however tight, will be able to prevent this.
   What does the pin of a hinge "feels", when the two knuckles are pulled towards different directions, perpendicular to its axis ? It "feels" mostly sheer forces(1), which try to tear it in two pieces. What does a pin of hinge "feels", when the direction of the pull of the knuckles is oblique, in relation to its axis, and not perpendicular ? It "feels" mostly friction forces, which, to be able to prevent the slippage of the knuckles on its surface, they need to be very strong .Nipping/gripping loops very tightly wrapped around penetrating lines may be an advantage regarding security, but it is a disadvantage regarding easiness of untying.
   So, in a Zeppelin-like knot, the angle between the Tail Ends and the direction of the pull of the first curves of the Standing Parts is very important, indeed : in fact, it determines the ability of those not-hooked-to-each-other curves to remain close to each other, or not. A Zeppelin-like knot, where the angle between the axes of the Tail Ends and the axis of the pull of the Standing Part is right, can remain in one piece, even if those ends remain rather loose ( as shown in the attached picture ). In short, in a Zeppelin-like knot the pair of Tail Ends works not as a glue, but as a toggle.

1.  http://en.wikipedia.org/wiki/Shear_force
Title: Re: Water Zeppelin
Post by: [Inkanyezi] gone on June 30, 2014, 10:58:44 AM
I think we should not get befuddled by what things look like or what we might compare them to visually, but more straightly checking the properties, wanted and unwanted, that a knot may provide.

There is also an important feature to consider here, friction, more precisely the friction between different parts of the rope that is knotted. Friction may be one of the most important features to consider in a rope, apart from breaking strength, elongation, water uptake and other. Now Dyneema, HMPE, is a very special case when it comes to friction.

So regardless of whether the ends come out perpendicular to the standing parts or not, friction is what holds things together in a knot, and HMPE is a very poor companion when we want friction. In any knot, there is always a force component along the rope axis at any point within, and this force tries to slip the free end into the knot to undo it. If friction is sufficient to withstand said force, and if friction builds up more than the length-wise force when applying load, the knot will hold, it will not slip back and undo itself. The most important property for this is friction, and HMPE does not provide much of that property.

So discussing whether the ends come out at right angles or not is not fruitful, as the important question is: Will friction within the knot prevent that it pulls the ends back into it and undo the knot? This question is crucial, whether the ends are aligned with the standing part or at other angles to them. Only testing will confirm or falsify any claims. Many here might have seen how a doubled bowline in HMPE will undo itself at a much lower force than the breaking force of the rope.

It is interesting to find knots that work in HMPE, and I think that factors that must be addressed also are ease of tying, and ease of undoing. Would these not be important, splicing is the answer. We know that splices can provide enough friction - also without any right angles.

We may also sometimes accept a "second best" solution. One property we look for when using HMPE, mostly is little elongation, while ultimate breaking strength might not be overly important, as the load will mostly be much less than the SWL of the rope. So if the knot will not slip at 1/10 of the SWL, it might still serve its purpose, if it will never be loaded beyond that point.

HMPE in boating is used, among other purposes, for halyards, where it is often spliced. It can also be used for sheets, although less frequently. The main important feature in halyard use is low elongation, and low weight comes second.

Neither halyards nor sheets are frequently knotted, but spliced to a hook of some kind, which is attached to the clew. Only in an emergency would sailors use knots, and very seldom would a bend be required. True that I use the bowline for attaching my sheets, but they are not HMPE. Also, if using HMPE, mostly it would have a braided polyester sleeve, and as the SWL is not even closely approached in normal use, but it is used mostly for the short elongation, it can be knotted with normal knots in normal use.

Nevertheless, it is interesting to find knots that work in straight HMPE, and the zeppelin formation might be a viable starting point. When I tried different sizes, I found that in lines with more friction than HMPE, doubling the first round turn does not achieve anything more than complicating things. It is the final turn that should be doubled for lines with more ordinary friction. Whether this holds true for HMPE should be tried before anyone puts anything important at stake by knotting unsheathed HMPE.

I think that simplicity is also an important feature with knots. If the knot is easy to tie, simple to inspect and thus "minimalistic" in appearance, those are features that might also be of great importance, as one wrong tuck will make a totally different knot, or perhaps no knot at all.

So for HMPE, i never tried bending it other than stuff with a PE sheathing, which I used for short slings, bent with double fisherman's (grapevine) knots. I have tried such a sling with my hydraulic jack, and I failed to break it or pull the core back.

I haven't tried to attach such a sheet or halyard to a sail, but if so, I would favour the #1843 anchor bend form, preferably with a snapshackle. This knot may also be less prone to slip back with an extra turn if needed. I think it should be tried, but it might behave much like the doubled bowline.
http://web.comhem.se/~u77479609/anchor_bend.html

Two of those hooked into each other would be reminiscent of a doubled zeppelin. Whether this would be a viable knot or not, is something to try out for anyone interested. I would prefer something else than HMPE, but in an emergency, a bend that really works could be a boon.
Title: Re: Water Zeppelin
Post by: xarax on June 30, 2014, 02:05:11 PM
   The Zeppelin bend looks "simple", but it is not - and that may explain why it was tied only "recently" ( taking into account the fact that knots were one of the first inventions of our ancestors ) - and why the almost unique, among the bends, way it works, is not understood, even by knot tyers who claim they are "familiar" :) with it, and promote/advertize its use. 

   In my previous posts, at Reply#2 and Reply#5, I was talking about the particular class of Zeppelin-like knots and bends, NOT about knots and bends, in general.     
   And, of course, I had never and nowhere said that a simple knot, any simple knot, can remain tangled without friction !
   To tie "Gordian" knots that can not be untangled, even in the absence of any friction ( = "ideal" Gordian knots ), we have to multiply their complexity, as shown at (0),(1),(2). There are no practical knots ( knots that, among other things, should be quite simple ), that do not need friction. And I have to repeat ( because II have seen that people, even competent knot tyers, often tend to be confused with this ), that a "Gordian" knot is meant to be a knot made from two topologically untangled links - if the two links of a knot are topologically tangled = "linked" right from the start ( two interlinked, "hooked" bights, where all four ends are loaded, for example ), they can not, by definition, become untangled/unlinked - without the use of a sharp enough cutting tool !  :) 
   What I said about the Tail Ends of the Zeppelin-like knots was that "the forces that are applied on them are sheer forces mostly, not friction forces"(sic). "What does the pin of a hinge "feels", when the two knuckles are pulled towards different directions, perpendicular to its axis ? It "feels" mostly sheer forces(1), which try to tear it in two pieces."(sic).)

   Of course, few people even notice, and even fewer understand the difference - tying a knot by just copying what is already stored in our visual or haptic memory, does not implant the understanding of its mechanism into our brains ! When we come to understand the mechanism of the Zeppelin-like knots, then it seems that it also becomes easy to us to find new such knots, "similar" to the Zeppelin bend, which utilize it. I believe that there are ( a few, at least ) people in this Forum, who understand what I am trying to paint in every possible way, including this "rope-made hinge" mental picture - and some of them had even proven their comprehension, by tying new, genuinely Zeppelin-like knots. However, I think that perhaps the majority of knot tyers had not "got it" yet - and that is the reason they continue to talk about, and consider the fake, so called "Zeppelin" loop as a Zeppelin-like knot. I only hope that we will NOT need some thousands of years ( i.e., as many as they had passed before the discovery of the Zeppelin bend... ), before this realization of the unique mechanism of the Zeppelin-like knots ( which does NOT require any rocket science !  :)), finally makes its way into the knotting litterature... In any case, I believe that, most probably, I will not be here, on this Land, for so many years, so to repeat the same things over and over again is not only boring to everybody ( including me...), but also pointless.
   
0. http://arxiv.org/abs/physics/0103080
1. http://igkt.net/sm/index.php?topic=3610.0
2. http://igkt.net/sm/index.php?topic=3610.msg20712#msg20712
Title: Re: Water Zeppelin
Post by: Seaworthy on June 30, 2014, 03:58:27 PM
I think we should not get befuddled by what things look like or what we might compare them to visually, but more straightly checking the properties, wanted and unwanted, that a knot may provide.

There is also an important feature to consider here, friction, more precisely the friction between different parts of the rope that is knotted. Friction may be one of the most important features to consider in a rope, apart from breaking strength, elongation, water uptake and other. Now Dyneema, HMPE, is a very special case when it comes to friction.

So regardless of whether the ends come out perpendicular to the standing parts or not, friction is what holds things together in a knot, and HMPE is a very poor companion when we want friction. In any knot, there is always a force component along the rope axis at any point within, and this force tries to slip the free end into the knot to undo it. If friction is sufficient to withstand said force, and if friction builds up more than the length-wise force when applying load, the knot will hold, it will not slip back and undo itself. The most important property for this is friction, and HMPE does not provide much of that property.

So discussing whether the ends come out at right angles or not is not fruitful, as the important question is: Will friction within the knot prevent that it pulls the ends back into it and undo the knot? This question is crucial, whether the ends are aligned with the standing part or at other angles to them. Only testing will confirm or falsify any claims. Many here might have seen how a doubled bowline in HMPE will undo itself at a much lower force than the breaking force of the rope.

It is interesting to find knots that work in HMPE, and I think that factors that must be addressed also are ease of tying, and ease of undoing. Would these not be important, splicing is the answer. We know that splices can provide enough friction - also without any right angles.

We may also sometimes accept a "second best" solution. One property we look for when using HMPE, mostly are little elongation, while ultimate breaking strength might not be overly important, as the load will mostly be much less than the SWL of the rope. So if the knot will not slip at 1/10 of the SWL, it might still serve its purpose, if it will never be loaded beyond that point.

HMPE in boating is used, among other purposes, for halyards, where it is often spliced. It can also be used for sheets, although less frequently. The main imporant feature in halyard use is low elongation, and low weight comes second.

Neither halyards nor sheets are frequently knotted, but spliced to a hook of some kind, which is attached to the clew. Only in an emergency would sailors use knots, and very seldom would a bend be required. True that I use the bowline for attaching my sheets, but they are not HMPE. Also, if using HMPE, mostly it would have a braided polyester sleeve, and as the SWL is not even closely approached in normal use, but it is used mostly for the short elongation, it can be knotted with normal knots in normal use.

Nevertheless, it is interesting to find knots that work in straight HMPE, and the zeppelin formation might be a viable starting point. When I tried different sizes, I found that in lines with more friction than HMPE, doubling the first round turn does not achieve anything more than complicating things. It is the final turn that should be doubled for lines with more ordinary friction. Whether this holds true for HMPE should be tried before anyone puts anything important at stake by knotting unsheathed HMPE.

I think that simplicity is also an important feature with knots. If the knot is easy to tie, simple to inspect and thus "minimalistic" in appearance, those are features that might also be of great importance, as one wrong tuck will make a totally different knot, or perhaps no knot at all.

So for HMPE, i never tried bending it other than stuff with a PE sheathing, which I used for short slings, bent with double fisherman's (grapevine) knots. I have tried such a sling with my hydraulic jack, and I failed to break it or pull the core back.

I haven't tried to attach such a sheet or halyard to a sail, but if so, I would favour the #1843 anchor bend form, preferably with a snapshackle. This knot may also be less prone to slip back with an extra turn if needed. I think it should be tried, but it might behave much like the doubled bowline.
http://web.comhem.se/~u77479609/anchor_bend.html

Two of those hooked into each other would be reminiscent of a doubled zeppelin. Whether this would be a viable knot or not, is something to try out for anyone interested. I would prefer something else than HMPE, but in an emergency, a bend that really works could be a boon.

All you have said makes a HUGE amount of sense to me.

I too agreed about the relevance of the angle of exit of the tails:

In these early stages of learning, it seems to me that it is important for the knot not being stressed by having any of the components pulled apart when load is applied that is very important, rather than where the angle the tail ends end up.

I have had a look at the Anchor Bend. I am not familiar with it. I currently have all chain currently (100m), and the end is connected to line that is just long enough to emerge from the anchor locker, so that it can be easily cut in an emergency. Force is never applied on this line. I tied it with a water bowline with a Yosemite finish. When we had only 50m of chain and 50 m of 28mm unsheathed nylon rode attached, I spliced the nylon onto the chain. Hence no need for a bend here.

This comment in your link is interesting:
"This knot is safe in the most slippery material existing, HMPE."
Does this refer to sheathed or unsheathed Dyneema?

The reason I ask is the next paragraph says:
"HMPE is an excellent material for halyards, and with this knot you may attach a snaphook just as securely as with a splice, but more compactly. There are several advantages with using a knot instead of a splice for attaching a snaphook to a halyard."

For halyards only sheathed Dyneema is used. The sheathing is usually polyester. Tying knots in this is not a big issue.
Title: Re: Water Zeppelin
Post by: Seaworthy on June 30, 2014, 04:13:43 PM
.......Nevertheless, it is interesting to find knots that work in straight HMPE, and the zeppelin formation might be a viable starting point. When I tried different sizes, I found that in lines with more friction than HMPE, doubling the first round turn does not achieve anything more than complicating things. It is the final turn that should be doubled for lines with more ordinary friction. Whether this holds true for HMPE should be tried before anyone puts anything important at stake by knotting unsheathed HMPE.

I agree. Tying a bend in unsheathed Dyneema would not be a commonly required thing, but it would be so nice to know what would work best. Dyneema is being used more and more on sailing vessels.

The reason why I am experimenting with a Water Zeppelin is that Evan Starzinger found there was no slip at all for a Water Bowline with a tucked finish in unsheathed Dyneema (in my opinion the tuck he used was inferior, it was not a Yosemite finish). Instead the knot broke at about 50% of line strength.
Title: Re: Water Zeppelin
Post by: xarax on June 30, 2014, 05:40:50 PM
   The reason why I am experimenting with a Water Zeppelin is that Evan Starzinger found there was no slip at all for a Water Bowline with a tucked finish

   So, Evan Startziger found that all the other double nipping loop / double collar bowlines do lip  - and that is the reason you have concluded that are seaworthless ... :)
   Being an imaginary / virtual / fictious knot tyer ( who, nevertheless, does not try to sell any rotten merchandise to anybody, like the real "enthousiasts"... :)), I would be GLAD if I were so fast in my reasoning... :). It would had saved me a lot of time, indeed - you know, TIME !
Title: Re: Water Zeppelin
Post by: [Inkanyezi] gone on June 30, 2014, 09:02:16 PM
Having seen the video Brion Toss made, I am a bit wary of the HMPE for knotting, but there is a trick that might make some knots ultimately secure.

Braided line can very easily be back-spliced, and a back-splice will make the end thicker. When tension is applied to a knot, it will not open, when the wedge-like back-splice is pressed into it, but it will be stopped right there. I think a zeppelin, maybe better a doubled one, will hold, if both of the ends are back-spliced to create bulge. Thus combining a knot with back-splices will probably prevent the ends from working themselves into the knot to undo it.

The HMPE I have used for halyards was always sheathed with polyester and never used close to breaking strength, so it wouldn't have put the knots to serious trial.
Title: Re: Water Zeppelin
Post by: Seaworthy on June 30, 2014, 09:07:09 PM
   The reason why I am experimenting with a Water Zeppelin is that Evan Starzinger found there was no slip at all for a Water Bowline with a tucked finish

   So, Evan Startziger found that all the other double nipping loop / double collar bowlines do lip  - and that is the reason you have concluded that are seaworthless ... :)
   Being an imaginary / virtual / fictious knot tyer ( who, nevertheless, does not try to sell any rotten merchandise to anybody, like the real "enthousiasts"... :)), I would be GLAD if I were so fast in my reasoning... :). It would had saved me a lot of time, indeed - you know, TIME !

I am not really sure what you are getting at here. As far as I am aware, Evans is not commercial. All his data and conclusions have been freely shared. His website is not a commercial one. He has done some wonderful work (eg I am currently using a soft shackle I have made from unsheathed Dyneema to hold my snubber to my chain at his suggestion, a huge improvement to the Prussik loop and Klemheist I previously used).
I am certainly not in any way commercial either, just a sailor with an interest in knots.

The Water Zeppelin I have described and photographed above, is simply one bend I think is worth trying in unsheathed Dyneema. Although we have a loop and hitch that is known to break at 50% of line strength (the best so far achieved with bare Dyneema), we have as yet have no bend that approaches this, let alone exceeds it.

By the way, the following statement of yours is incorrect. Try tying the Zeppelin bend in thicker line (eg 10 mm). It immediately become obvious that when the line is dressed (and even more obvious when any load is put on) that the tails emerge from the bend at closer to a 45 degree angle to the bend, not at 90 degrees as you state:

.....One of the most subtle things is the way it achieves its "balance" : even after heavy loading, the pair of the Tail Ends ( the "pivot" of this rope-made hinge ), remains  perpendicular to the axis of the knot, so the forces that are applied on them are sheer forces mostly, not friction forces.

So your basis for judging variations of the Zeppelin is highly flawed:

   When I see a knot that is supposed to be some variation or implementation of the Zeppelin bend, the first thing I look is the angle between the Standing and the Tail Ends : if this angle is not the right angle, it is not a right angle  :), so the supposedly Zeppelin-like knot is determined to work differently than the genuine Zeppelin knot, the Zeppelin bend - and, most probably, it works much worse.
Title: Re: Water Zeppelin
Post by: xarax on June 30, 2014, 10:05:52 PM
Evans is not commercial. All his data and conclusions have been freely shared. His website is not a commercial one. He has done some wonderful work..

I agree. I was not talking about Evans, of course, but about the infamous travelling salesman who made this sooo clever comment about the "real" knot enthousiasts - in contrast to me, of course...

 

Try tying the Zeppelin bend in thicker line (eg 10 mm). It immediately become obvious that when the line is dressed (and even more obvious when any load is put on) that the tails emerge from the bend at closer to a 45 degree angle to the bend, not at 90 degrees as you state:
So your basis for judging variations of the Zeppelin is highly flawed:

   Try to imagine a knot tyer who has tied thousands of Zeppelin bends and other Zeppelin-like knots, in hundreds of different materials - mostly in climbing ropes, 9-12.5 mm. Then, try to imagine how something that, to you, is "immediately obvious", to him, miraculously, was not. Then, read some of my posts again ( I had wrote dozens of posts on the same subject...), tie some of the genuine Zeppelin-like knots shown in this Forum, and try to understand what I say, rather than be sooo fast, as you are, to conclude that my "basis for judging variations of the Zeppelin is highly flawed" ( not only flawed, but highly flawed !  :) :)). Last but not least, tie some Zeppelin bends, try to "see" them, and think for a while, for KnotGod s sake !

Title: Re: Water Zeppelin
Post by: Seaworthy on June 30, 2014, 10:51:35 PM

Try tying the Zeppelin bend in thicker line (eg 10 mm). It immediately become obvious that when the line is dressed (and even more obvious when any load is put on) that the tails emerge from the bend at closer to a 45 degree angle to the bend, not at 90 degrees as you state:
So your basis for judging variations of the Zeppelin is highly flawed:

   Try to imagine a knot tyer who has tied thousands of Zeppelin bends and other Zeppelin-like knots, in hundreds of different materials - mostly in climbing ropes, 9-12.5 mm. Then, try to imagine how something that, to you, is "immediately obvious", to him, miraculously, was not. Then, read some of my posts again ( I had wrote dozens of posts on the same subject...), tie some of the genuine Zeppelin-like knots shown in this Forum, and try to understand what I say, rather than be sooo fast, as you are, to conclude that my "basis for judging variations of the Zeppelin is highly flawed" ( not only flawed, but highly flawed !  :) :)). Last but not least, tie some Zeppelin bends, try to "see" them, and think for a while, for KnotGod s sake !

LOL. Don't be so inflexible regarding your inability to make an error in observation. Tie a Zepp in 10 mm double braid polyester, leaving long tails. Dress it neatly. Give it a good shake to let it fall into place how it wants to.  Hold it up in the air by hanging onto the standing ends and observe how the tails drape.

They do NOT drape perpendicularly to the standing line. Not even close.
Title: Re: Water Zeppelin
Post by: xarax on June 30, 2014, 11:36:08 PM
   I got it ! That is why you call them "Water Zeppelins"! After you immerse them in the water, you drape them in mid air, under the hot sun of the Caribbean ( ? ), to dry them up, while you are taking a mid day nap, and you Zzzz...Zzzz...Zzzz. :) :) :)
   I suggest you leave "tails" about one meter long, so they will become completely parallel to each other, and the angle between them and the Standing parts will become 0 or 360 degrees. "Not even close" to 90 degrees, indeed...  :)
   ( However, I have to mention that I was not talking about the free-hanging segments of the rope outside the knot s nub, of course... I was talking about the angle between the pin of the rope-made hinge, and the knuckles / first curves of the Standing parts - the tip of which was inside the knot s nub, the last time I looked... And I was not talking about loose knots, of course, draped under the hot sun - I was talking about loaded knots, where the two adjacent pins are confronting the sheer forces applied on them by the first curves of the Standing Parts, which tend to tear them apart. )
Title: Re: Water Zeppelin
Post by: xarax on July 01, 2014, 03:13:47 AM
Watch this :
http://www.youtube.com/watch?v=Givv9cBB_Hw
This angle looks as "right" as it could possibly be ...
Title: Re: Water Zeppelin
Post by: Dan_Lehman on July 01, 2014, 06:14:11 AM
From what I have read so far, the Zeppelin with the thinner line given one more final tuck (no one has come up with a name yet, do we call it the 'Asymmetric Zeppelin' or '1.5 Zeppelin' or 'Semi Double Tucked Zeppelin'?) seems the best relatively easy way known to join line of different diameter used when sailing (all but slippery stuff like unsheathed Dyneema).
I would've hoped that this was not the conclusion
you'd reach.  Frankly, I think that in a great many
circumstances, most folks would look at Inkanyezi's
red_cord-2-real_rope knot with horror/disgust : okay,
if one is just hoisting something in temporary, attentive
use; unacceptable as a knot to be left *on its own* for
any time.  (But, if you like it, why would you not prefer
a similar variation of Ashley's bend #1452, which nicely
looks less out grossly disproportionate!)   ;)

After hearing Evans report that Ashley's bend #1452 modified
by (1) making full rather than "U" turns in the SParts
AND THEN
(2) tucking the tails twice slipped (holding up
to some force, then slipping ... until a low force!?),
...
I consider "all bets are off" on the skinny slick HMPE
that he was using.  (I did have NERopes break-test
some (5) eyeknots in their 5/16" urethane-coated (blue)
12-strand Dyneema, and those held to break.  And among
these was a modified, bowlinesque eyeknot (it's a fig.8,
topologically but rather bowline-like geometrically).
(I'm wondering if Evans's thin line heated to a state
of near-liquidity!?)

--dl*
====
Title: Re: Water Zeppelin
Post by: xarax on July 01, 2014, 11:25:04 AM
   In fact, a Clove-hitch-based Zeppelin knot, may conceal a contradiction in terms : In a genuine Zeppelin-like knot, we do not need more friction between the pair of Tail Ends ( the pin of the hinge ) and the pair of the first curves of the Standing Parts ( the knuckles of the hinge ), so the former do not slip through the later - we need more balance, a better alignment of all the individual elements of the Zeppelin locking mechanism, so the angle between the axis of the Tail Ends and the axis of the continuations of the Standing Ends will be, and will remain, close to the "right" angle : the right angle. If we achieve this, the forces applied on the pair of Tail Ends would be shear, mostly, forces, not friction forces -  and it is much easier to a segment of any not-too-soft rope to withstand shear forces, than friction forces, because it is much more difficult to the shear forces to cut it in two, than to the friction forces to make it slide and slip.
   Moreover, a Clove hitch may clinch around itself very tightly, and it can even jam - so the greater advantage of all the Zeppelin-like knots, their ability to be released easily even after heavy loading, would be jeopardised. I believe that, if one wants to use a double nipping structure other than the simple double nipping loop used in the known Double Zeppelins, one should better use a Girth hitch, not a Clove hitch. ( I have seen this when I was trying various nipping structures as "nipping/gripping tubes" for Eskimo-like adjustable loops (1), and I do not see much difference between the situation there and the situation here...)
   Of course, we should continue to tie and try the known knots, using nipping/gripping Clove hitches instead of single or double nipping loops - but in the special, and almost unique, case of the Zeppelin-like class of knots, I do not believe this will leads us anywhere. The better of the worst Clove-hitch based Zeppelin bend I have tied and tried is shown in the attached picture - sooo ugly and sooo tight, I had not spared much time to examine it in detail..

1. http://igkt.net/sm/index.php?topic=4347
Title: Re: Water Zeppelin
Post by: Seaworthy on July 02, 2014, 06:47:47 AM
   I got it ! That is why you call them "Water Zeppelins"! After you immerse them in the water, you drape them in mid air, under the hot sun of the Caribbean ( ? ), to dry them up, while you are taking a mid day nap, and you Zzzz...Zzzz...Zzzz. :) :) :)
   I suggest you leave "tails" about one meter long, so they will become completely parallel to each other, and the angle between them and the Standing parts will become 0 or 360 degrees. "Not even close" to 90 degrees, indeed...  :)

No need for sarcastic replies. We should be able to discuss differences of opinion in a straightforward, but civil manner.

Watch this :
http://www.youtube.com/watch?v=Givv9cBB_Hw
This angle looks as "right" as it could possibly be ...

It depends entirely how you dress this knot. I see no warnings anywhere not to touch the tails while dressing it. If you give the tails a light yank at any stage (part of the dressing procedure for me for any knot) the tails end up close to 45 degrees to the standing part. Try it. In any thickness, any material, leaving any tail length.

It is only if you don't touch the tails that they can end up jammed in the 90 degree position.

You have stated:

......
  One of the most subtle things is the way it achieves its "balance" : even after heavy loading, the pair of the Tail Ends ( the "pivot" of this rope-made hinge ), remains  perpendicular to the axis of the knot, so the forces that are applied on them are sheer forces mostly, not friction forces.
......
   When I see a knot that is supposed to be some variation or implementation of the Zeppelin bend, the first thing I look is the angle between the Standing and the Tail Ends : if this angle is not the right angle, it is not a right angle  :), so the supposedly Zeppelin-like knot is determined to work differently than the genuine Zeppelin knot, the Zeppelin bend - and, most probably, it works much worse.

The photo below shows the Zeppelin under maximum load I can apply on our winches. The appearance was near identical before load was applied. The bend was dressed normally. This angle certainly does not look 90 degrees to me. It is pretty close to 45 degrees.

I can't see how you can possibly judge the effectiveness of variations of the Zeppelin by looking at the "angle between the Standing and the Tail Ends":
Title: Re: Water Zeppelin
Post by: xarax on July 02, 2014, 10:58:26 AM
It depends entirely how you dress this knot. I see no warnings anywhere not to touch the tails while dressing it. If you give the tails a light yank at any stage (part of the dressing procedure for me for any knot) the tails end up close to 45 degrees to the standing part. Try it. In any thickness, any material, leaving any tail length.

It is only if you don't touch the tails that they can end up jammed in the 90 degree position.

   Noope...
   First, the tails of the Zeppelin bend do not need to be "touched" at all, at any stage - this knot is self-dressing, and it always settles in the same final compact form. A very useful thing is that this bend, while it shrinks, it does not "eat" its tails - as it happens in almost all the numerous other bends based on interlocked, interweaved or interpenetrating overhand knots we have. ( Another such bend, which also does not consume any portion of its tails, is the Ashley s bend ). This is another advantage of the Zeppelin bend, and another reason we do not need to "give the tails a light jank", as we do in most other knots.
   Second, the angle we are talking about does not depend of "how you dress the knot" ( not that you can dress it in many different ways, without trying a lot ! )- after heavy loading, this knot always settles in the same form. Of course, if you deliberately twist the tails around each other, and then manage to "lock" them tightly, before they get the chance to settle in their natural position, you may get some odd-looking forms - but even on those, the angle between the "knuckles" and the "pins" remains closer to 90 than to 45 degrees.
   In order to make any sense, the sentence "It is only if you don't touch the tails that they can end up jammed in the 90 degrees position ", should be changed a lot :
   It is only if you twist the tails around each other, and you keep doing this until a stage when the pulling of the Standing ends makes the knot "locks" around them, that they may end up in a position slightly different from their natural 90 degrees one. ( I believe you know that the Zeppelin bends, in particular, and most of the Zeppelin-like knots, in general, do not "end up jammed"). 
   
   Is  this "try it" as sarcastic as the previous advice, to "try tying the Zeppelin bend in thicker line (eg 10 mm)"(sic), and not "be so inflexible regarding [my] inability to make an error in observation"? Because, if you really believe that I ( or, for that matter, anybody else in this Forum ) have not "tried" the Zeppelin bend, you should not lose any more of your precious time with me.

I can't see how you can possibly judge the effectiveness of variations of the Zeppelin by looking at the "angle between the Standing and the Tail Ends"

  (Allow me to be just a little bit sarcastic, for the last time ...)
  Evidently !  :)
  However, if you follow my advice as much as I had followed yours, and read my posts again, trying to understand and not just to argue, you may "see" how.
Title: Re: Water Zeppelin
Post by: Seaworthy on July 02, 2014, 12:29:04 PM
   First, the tails of the Zeppelin bend do not need to be "touched" at all, at any stage - this knot is self-dressing, and it always settles in the same final compact form.

There is a big difference between "touching the tails" not being needed and being entirely the wrong thing to do.

   
   It is only if you twist the tails around each other, and you keep doing this until a stage when the pulling of the Standing ends makes the knot "locks" around them, that they may end up in a position slightly different from their natural 90 degrees one.

I have NEVER done the above.

All I have done is held onto the two tails with the standing lines draped down completely loose and given the tails a light tug. They always end up at 45 degrees to the standing lines. I have never read anywhere that giving the tails a light tug will weaken the knot because the tails end up at the wrong orientation. With heavy loading (and I can exert a reasonable amount on my large winch) the tails remain in this spot. They do not move to the 90 degree position.

Second, the angle we are talking about does not depend of "how you dress the knot" ( not that you can dress it in many different ways, without trying a lot ! )- after heavy loading, this knot always settles in the same form. Of course, if you deliberately twist the tails around each other, and then manage to "lock" them tightly, before they get the chance to settle in their natural position, you may get some odd-looking forms - but even on those, the angle between the "knuckles" and the "pins" remains closer to 90 than to 45 degrees.

I maintain the only way you can end up with the tails at 90 degrees is if you do not touch them at all during dressing. And I repeat, I do not mean any weird twisting, just hanging onto the two of them and giving them a tug.

   When I see a knot that is supposed to be some variation or implementation of the Zeppelin bend, the first thing I look is the angle between the Standing and the Tail Ends : if this angle is not the right angle, it is not a right angle  :), so the supposedly Zeppelin-like knot is determined to work differently than the genuine Zeppelin knot, the Zeppelin bend - and, most probably, it works much worse.

Let us agree to disagree on this issue.

BTW There has never been any sarcasm in any if my comments. I may be disagreeing with you completely, but no sarcasm has been employed. It is totally unnecessary in any civil discussion/debate.
Title: Re: Water Zeppelin
Post by: xarax on July 02, 2014, 01:41:46 PM
  As this angle gets more acute or more obtuse than 90 degrees, the pulled knuckles tend to slide on the obliquely oriented pins, so the pins run the danger to be pulled our of the obliquely oriented knuckles  - in order to be able to withstand this, the pins should withstand more friction forces, and less shear forces. I believe that what I keep saying all this time may not be sooo acute, but it is not sooo obtuse either !  :)  :)
   I have not tied your variation on Dyneema, and I have not loaded it heavily - but I think I can "see" that the knuckles will slide on the pins, and will drag them out of their castings. I do not believe that the supposedly tighter grip of the Clove hitches / half hitches, will be able to prevent this. I see that the angle is not so close to the "right" angle, as it should had been, and that the only thing that can help the Tail Ends not be pulled out of the hitches is the one, only, sharp U-turn. However, as it was noticed by allene in this thread :
   http://igkt.net/sm/index.php?topic=4756.0
in this extremely slippery material, one or even two U-turns will not be enough. The double/double Zeppelin bend ( bowled over and twice collared ) is a much better knot, IMHO : the angle is right, the alignment of the continuations of the Standing Ends is almost perfect, and the U-turns the Standing Parts make are sufficiently many.

    When you will buy the hydraulic jack, or the pull-back hydraulic ram, and find a way to attach it on board of your boat, we will see !  :) The proof of the pudding is in the eating...

https://www.google.co.uk/search?q=%22pull+back+hydraulic%22&hl=en&gl=uk&authuser=0&source=lnms&tbm=isch&sa=X&ei=7_uzU8P9Bcva0QWI4YDYDQ&ved=0CAgQ_AUoAQ&biw=1600&bih=763



   

Title: Re: Water Zeppelin
Post by: Dan_Lehman on July 02, 2014, 07:44:06 PM

It depends entirely how you dress this knot. I see no warnings anywhere not to touch the tails while dressing it. If you give the tails a light yank at any stage (part of the dressing procedure for me for any knot) the tails end up close to 45 degrees to the standing part. Try it. In any thickness, any material, leaving any tail length.

It is only if you don't touch the tails that they can end up jammed in the 90 degree position.

There are a couple of ways to dress & set the
knot, and frankly I think that variance in tails
angle is pretty slight among them, and roughly
perpendicular --at least in the sense that they
are clearly NOT so amenable to being secured
against SParts, as commercial fishers are wont to do.

   Noope...
   First, the tails of the Zeppelin bend do not need to be "touched" at all, at any stage - this knot is self-dressing, and it always settles in the same final compact form.
Clearly "noooooope" to this : a loose z. will take
an open form with rather bowlinesque nipping turns
in the SParts.  (A Real KnotTyer(tm) would know this.)

 ;D
Title: Re: Water Zeppelin
Post by: [Inkanyezi] gone on July 02, 2014, 09:36:49 PM
I come back to what I hinted earlier, creating bulk, to avoid that the end slips into the knot.

Contrary to what has been stated somewhere, there is no "pin" in the Zeppelin, and anyone observant enough will see that the ends do not emerge perpendicularly to the standing parts. Just as in any other knot, it is friction that holds when it is tied in ordinary stuff (not HMPE). Friction is helped by deformation within the knot form, so that friction is increased, when the material of the end has to be compressed in order to be pulled into the knot.

HMPE is another creature altogether. It does not elongate, and it cannot be compressed, and moreover its friction coefficient is too low for just about any knot formation.

So there is where the wedge I suggested comes in. If some of the material, by back-splicing, is brought back into the braid, there will be bulk, which has to pry the knot a bit more open, in order to slip back into it. In other materials, deformation creates saddle-like shapes, which resist further deformation and help to build up friction, but not HMPE. It may change form a bit, but not volume. It is just as resistant to compression as to elongation.

So the HMPE knot will have to rely on another feature than only friction, or it will pull the end into the knot, ultimately undoing it. My suggestion is bulk. A rather short back-splice might do the trick - I think it is worth trying. If the end is bulkier than the rest of the rope, it might hold like the mushroom head of a rivet, resisting to be pulled back into the knot.
Title: Re: Water Zeppelin
Post by: xarax on July 03, 2014, 01:18:53 AM
   Noope...
   First, the tails of the Zeppelin bend do not need to be "touched" at all, at any stage - this knot is self-dressing, and it always settles in the same final compact form.
Clearly "noooooope" to this : a loose z. will take an open form with rather bowlinesque nipping turns in the SParts.  (A Real KnotTyer(tm) would know this.)

This surreal knot-tyer knows that this is not a pipe, that a rose is a rose is a rose, and that he was not talking about a loozzze zzz.
Now, on a less imaginary world, there is never a "final" form ; as long as the knot shrinks ( and it shrinks until the very moment it breaks and explodes ), it becomes more and more compact, so, strictly speaking, its form changes - on some knots, during the "final" stages, it makes some funny things, indeed. However, in comparison to the changes from the loose to the compact form, these changes are not so pronounced that would allow us to talk about a different geometry. If that would had happened, if there was a continuous change in geometry, we would be talking about a multi-stable knot - or rather about an un-stable knot !
Title: Re: Water Zeppelin
Post by: xarax on July 03, 2014, 01:59:28 AM
   
   It is only if you twist the tails around each other, and you keep doing this until a stage when the pulling of the Standing ends makes the knot "locks" around them, that they may end up in a position slightly different from their natural 90 degrees one.

I have NEVER done the above.

Well, you should do it now, to see what happens.
Do not think of this twist as a "bad" thing ! If it is a genuine twist, it is beneficial to the knot, because it increases the bulk of the central core, and forces the first curves of the Standing Parts ( = nipping/gripping loops, "knuckles" ) be rounder and wider. Rounder and wider nipping loops are supposed to be stronger, and, in any case, they are more fluid, smooth structures, without sharp curves, which are able to distribute the forces acting inside the nub more evenly, along a more extended area.
When you will test the single and double Zeppelins, do not forget to test the Zeppelin X bend as well ( X = crossed tails ) :
http://igkt.net/sm/index.php?topic=2088.0
Title: Re: Water Zeppelin
Post by: xarax on July 06, 2014, 02:48:40 PM
if one wants to use a double nipping structure other than the simple double nipping loop used in the known Double Zeppelins, one should better use a Girth hitch, not a Clove hitch.

   However, a double structure is a double structure - and two of them, the one next to the other, may become too tightly wrapped around themselves ( due to the friction forces between their adjacent wraps ), and around the "pin(s)" of the Zeppelin-like bend ( where we would had needed more balance, to deal with the shear forces, not more friction ). Even at the most simple Zeppelin bend, the percentage of the initial tensile forces able to reach the tails, is very small : after those three successive U-turns they make, until they become Tail Ends, the Standing Part have uploaded already most of them into the knot s nub. What is paramount is the alignment of the adjacent ( but parallel, not "hooked" within each other ) first curves of the Standing Parts, and the angle between them and the penetrating pin(s), so they will be able to confront the shear forces they have to withstand. The result of the more friction within and between those tightly wrapped double structures will be a knot that will not be tied or untied easily any more, and will not be self-dressing - two of the great advantages of the parent Zeppelin bend. See the attached picture, for a not-too-ugly, but still too-tight and not easily tiable and untiable bend, based on parallel, not "hooked" within each other Cow/Girth hitches ( instead of Clove hitches, as in the bend shown at Reply#18 (1).

1. http://igkt.net/sm/index.php?topic=4946.msg32576#msg32576
Title: Re: Water Zeppelin
Post by: Dan_Lehman on July 07, 2014, 09:17:01 PM
Well, you should do it now, to see what happens.
Do not think of this twist as a "bad" thing ! If it is a genuine twist,
it is beneficial to the knot, because it increases the bulk of the central core,
and forces the first curves of the Standing Parts ... to be rounder and wider.
Rounder and wider nipping loops are supposed to be stronger, ...
Which supposition remains to be deeply analyzed by
careful testing.  In any case, one should be suspicious
of this variation on account of its asymmetry
--what might be good for the goose (one side) will not
obtain for the gander (and better see what does!)

(In contrast, there is such a crossing for SmitHunter's bend
that does yield such improvements (in shape, if not
in effects on strength), AND makes it resist jamming.)

There are other careful ways of dressing the knot so as
to try to affect SPart curvature, but that becomes tedious
and ... without a firm basis in testing (and with some
realization that any difference likely would be irrelevant).


--dl*
====
Title: Re: Water Zeppelin
Post by: [Inkanyezi] gone on July 08, 2014, 01:27:05 PM
I think it is worth the while to think about how a rope actually works. It takes a longitudinal load, and all parts within a knot will carry some fraction of this longitudinal load. Hence it is always friction in the "nub" that governs its resistance to slip.

The problem with HMPE in this regard is that the longitudinal force, due to low friction in all the different turns the rope takes, will remain substantially to the last point where the end emerges from the knot, and that the friction that holds the end back can be lower than the power that tries to pull it in. This force is present also in the Zeppelin, and for more normal ropes, there is ample friction to prevent the ends from being pulled into the knot. When tying in HMPE, this cannot be guaranteed, and I would expect it to fail just as the double bowline did.

One has to go beyond looks and think of how the forces work within the knot, to understand it better.

If we create bulk, by back-splicing the very end, this bulk will act as a wedge and try to pry the knot more open, when the end is drawn into it. Testing will show whether this is sufficient to avoid the catastrophic slippage we have seen. Whether the knot is "strong" is entirely another matter. The same approach to prevent slippage can be applied to other knots, as the grapevine, but then of course there is the problem of jamming at high load.