Stealth mode - New Generation Ropes

[Seaworthy Lass]

Originally Posted by Breaking Waves

With SWL's loop connection idea there are no theoretical engineering concerns and there are probably no significant hidden "got-ya's" because quite similar constructions are used in commercial high load/safety applications (high load slings and loops and quite common).

The Bullseye is certainly very attractive and quite creative, and also can be made very strong by picking the line size. However SWL correctly say there is no data/calculation on how strong or reliable it actually is. There, in fact, are theoretical engineering concerns, where the strands bear on each other - that is likely a 1:1 bend (a bend with 10 degrees or more of deflection) with the associated (50%ish) significant strength reduction and there could also be some rubbing (which might create heat or chafe) between the strands if the load is not steady on the ring. Empirically I am not aware of a construction like this used in the 'serious commercial' applications - that may be because it is flawed or it may be because no-one thought of it - IDK. From a practical standpoint, in the vast majority of yachting applications, it is almost certainly just fine because the base case (using normal size cordage) will be quite strong no matter the above concerns. But the fact we don't know how strong it, we have no calculation, makes it difficult to properly size for a real super high load safety/survival type applications like the drogue.

Thanks for the compliments .

I do think this is a game changer when it comes to securing low friction rings so they cannot pop out. Every single other technique currently being used involves clenching the throat in some way. To hold a ring securely when clenched, the tearing forces at the throat can be close to 40% of the load applied.

Regarding chafe, so far I have seen zero problems with the weave. All the chafe seen has been at the connection point of the strop (melting also at this point). The weave still appears pristine to the naked eye at the stage it needs replacing due to chafe or melting issues elsewhere.

We need a volunteer to do some load testing of the Bullseye.

SWL

[Seaworthy Lass]

Originally Posted by Breaking Waves

I also generally like Samson's recommendations, and 3:1 is often achievable, but the 5:1 recommendation is odd because (as you comment) it is not followed with any of Samson's own thimbles and by very few spliced loop commercial applications. I guess either it is an 'aspirational' recommendation or somehow got mangled/taken out of context in editing.

I guess the reason Samson’s recommendation stands is that the tearing force at the throat is 10% of the total load applied when the proportion as shown in their diagram is 3:1.

At 5:1 that is at least down to 5.6%.

Originally Posted by Breaking Waves

BTW, if you want to know what the throat angle will be with a specific bridle geometry, it is dead easy to just make a small scale version and measure. Use say 3 or 6mm dyneema (it does not matter) and tie the loops rather than splice (just for easy/speed). You just need to get the ratio of bridle length to distance between base of bridles (transom width) correct. you can do in 5 minutes pretty much anywhere. The geometry will scale exactly.

Excellent suggestion!
Thanks.

SWL

[fxykty]

Originally Posted by Dockhead

...
How will you dress the cow hitches, and does it make a difference? I'm guessing that it does -- what do you think?

Since the segments of the JSD rode taper, wouldn’t the best way is to use the larger diameter for the eye and the smaller diameter for the dressed cow hitch? That way you get the largest possible diameter for the cow hitch to wrap around.

Regarding the bridle to leader connection, given 12mm bridle and leader, or 14mm bridle, is it reasonable to use 4 passes of 6mm UHMWPE through the 3 eyes? What’s the way to secure the two ends of that 6mm line? Or just a regular soft shackle?

[Seaworthy Lass]

Originally Posted by fxykty

Since the segments of the JSD rode taper, wouldn’t the best way is to use the larger diameter for the eye and the smaller diameter for the dressed cow hitch? That way you get the largest possible diameter for the cow hitch to wrap around.

Yes, definitely. There is not a lot of difference in diameter though (eg 12 mm will connect to 14 mm) and so the configuration may not be the same as when a line is cow hitched to an object. As a matter of interest I will have a play at some stage with putting load on via a winch and seeing what shape it takes on as load is slowly applied.

With a cow hitch that has load put on both legs I also guess that the dressing is not critical. It is a very simple knot that can’t take on a defective shape easily in slippery UHMWPE. With it being used on an eye it also can’t slip - this is the failure mode of lots of knots if left undressed and high load is applied quickly.

Originally Posted by fxykty

Regarding the bridle to leader connection, given 12mm bridle and leader, or 14mm bridle, is it reasonable to use 4 passes of 6mm UHMWPE through the 3 eyes? What’s the way to secure the two ends of that 6mm line? Or just a regular soft shackle?

You would not lash the junction. You would simply make a loop and twirl it around a few times (Breaking Wave suggests no more than three for good load distribution). The loop is super firmly secured with long bury splicing and lock stitching. See post #106 for instructions.

SWL

[SailRedemption]

Good thread here, thanks. My thoughts are that this is getting over thought. I don't see why thimbles(be it the heavy duty Samson or Colligo) won't work for the bridle leader connection with rated shackles connecting them. If the case for Colligo bridle thimbles, you could just put and eye through both bridle ends. If one is worried about the heavy connection sinking to the rudder or prop, a simple fishing line float or a small fishing buoy clipped on with a double action carabiner or something similar to attach it to the bridle connection would keep it afloat, without adding much complexity or, in my mind no detriment to the JSD.

One thought about the Colligo thimbles, they aren't fully captive, but could be if you whipped the dyneema to the thimble sides, like the open version below. You would essentially be securing the bottom of the eye closest to the throat which would be where you could get some deflection of the thimble in the eye.

[fxykty]

Originally Posted by Seaworthy Lass

Yes, definitely. There is not a lot of difference in diameter though (eg 12 mm will connect to 14 mm) and so the configuration may not be the same as when a line is cow hitched to an object. As a matter of interest I will have a play at some stage with putting load on via a winch and seeing what shape it takes on as load is slowly applied.

With a cow hitch that has load put on both legs I also guess that the dressing is not critical. It is a very simple knot that can’t take on a defective shape easily in slippery UHMWPE. With it being used on an eye it also can’t slip - this is the failure mode of lots of knots if left undressed and high load is applied quickly.



You would not lash the junction. You would simply make a loop and twirl it around a few times (Breaking Wave suggests no more than three for good load distribution). The loop is super firmly secured with long bury splicing and lock stitching. See post #106 for instructions.

SWL

Thanks, reread that post. I’m still not sure how that works. Is the loop made first, then threaded through the three eyes, then what? Or is it instead that you pass a line through the three eyes, then splice the two ends into each other to create the loop? But if so, that’s only a single line so would need to be the same diameter.

Would you be able to sketch what you mean?

[Seaworthy Lass]

Originally Posted by SailRedemption

Good thread here, thanks. My thoughts are that this is getting over thought. I don't see why thimbles(be it the heavy duty Samson or Colligo) won't work for the bridle leader connection with rated shackles connecting them. If the case for Colligo bridle thimbles, you could just put and eye through both bridle ends. If one is worried about the heavy connection sinking to the rudder or prop, a simple fishing line float or a small fishing buoy clipped on with a double action carabiner or something similar to attach it to the bridle connection would keep it afloat, without adding much complexity or, in my mind no detriment to the JSD.

One thought about the Colligo thimbles, they aren't fully captive, but could be if you whipped the dyneema to the thimble sides, like the open version below. You would essentially be securing the bottom of the eye closest to the throat which would be where you could get some deflection of the thimble in the eye.

Hi SailRedemption

They look like beautiful items to replace conventional thimbles. The largest “open” one takes line of 11-13 mm and has a MBL of 13,608 kg-f. The SWL is listed as half of that.

I like the idea of lashing around the sides of the connector. Throat issues could be minimised doing this. If you had to rely purely on a clench at the base (eg Brummel lock before the long bury splice, as they seem to use, or whipping plus bury), unlike static systems it would have to be secured right next to the rim so the thimble could not flip out.

Securing the thimble completely so it could not flip out still introduces tearing forces at the throat of the leader though, something the soft loop avoids altogether. I think any thimble wouldn’t be ideal with the loads that this drogue junction could be subject to (but with essentially a very small diameter down at the base with Colligo’s thimble it would be much better than trying to do the same with a LF ring), but that is just my point of view.

One thing to note is that if the thimble did flip out or fail, unlike a solid LF ring failing, the entire drogue is not lost. You still have the bridle legs connected to the leader. For a “belt and britches” type of person this appeals tremendously.

This is also the beauty of the Bullseye weave if load testing results were successful. The system does not fail if the hardware fails, as the bridle legs are still connected to the leader. No reason I can see why the weave could not also be used with thimbles like this, which would essentially eliminate tearing forces at the throat.

SWL

[Seaworthy Lass]

Originally Posted by fxykty

Thanks, reread that post. I’m still not sure how that works. Is the loop made first, then threaded through the three eyes, then what? Or is it instead that you pass a line through the three eyes, then splice the two ends into each other to create the loop? But if so, that’s only a single line so would need to be the same diameter.

Would you be able to sketch what you mean?

Make the loop first with long buries of the tails plus lock stitching. Twirl it around so you have a smaller loop consisting of three rounds. Then secure the leader and two legs of the bridle either by cow hitching the eye splices (or better still, as Breaking Waves suggested, possibly using Prusik hitches instead) or splicing the eye splices directly on.

I will draw a diagram in a sec to illustrate this.

SWL

[Seaworthy Lass]

Originally Posted by fxykty

Would you be able to sketch what you mean?

Trying to accurately sketch a loop twirled around three times defeated me, so I took off my dyneema “necklace” , secured it to form a loop, twirled it around, whited out the stopper and locket and drew on cow hitches for the leader and bridle legs that have eye splices at the ends of each.

This is the result. Zero issues with tearing forces at the base of the eye splice of the leader, as you would get if you cow hitched the bridle legs directly to the eye of the leader or if you used any kind of thimble.

For now I am sticking with this option, as I think it is the best solution.
I like BW’s idea of making the hitches Prusik ones, not Cow hitches though:

[conachair]

Originally Posted by Seaworthy Lass

Trying to accurately sketch a loop twirled around three times defeated me, so I took off my dyneema “necklace” , secured it to form a loop, twirled it around, whited out the stopper and locket and drew on cow hitches for the leader and bridle legs that have eye splices at the ends of each.

This is the result. Zero issues with tearing forces at the base of the eye splice of the leader, as you would get if you cow hitched the bridle legs directly to the eye of the leader.

For now I am sticking with this option, as I think it is the best solution.
I like BW’s idea of making the hitches Prusik ones, not Cow hitches though:

What about doing away with the cow hitches altogether and splicing the loop straight into the eyes? Or the worlds fattest longest soft shackle if you want to take it apart? You could have hard eyes then if you wanted. Loops chocked like that round such a small radius never feel quite right imho.

[Seaworthy Lass]

Originally Posted by conachair

What about doing away with the cow hitches altogether and splicing the loop straight into the eyes? Or the worlds fattest longest soft shackle if you want to take it apart? You could have hard eyes then if you wanted. Loops chocked like that round such a small radius never feel quite right imho.

The hitches will “lock” on under load. This is probably beneficial as it avoids the eyes moving around as the load transfers from one leg to the other (the alteration of geometry alters when load is on two legs or just one).

I thought at first the amount the eye of the bridle legs would need to move as load was transferred was larger than it actually is, making cow hitches that would inevitably slide around, not very favourable. BW’s photos a few pages back show this is not the case. The triangle made at the connection point is not equilateral, as I first thought.

The advantage I think with a Prusik hitch is that it is wide enough the there may be no need for the hitch to slide around at all as the load is transferred (or at least the sliding will be less).

What do you think?

This is all speculative for me at the moment.

SWL

Edited to add: I am not a big fan of cow hitching at all in general. If the bridle legs are made thicker than needed for chafe protection then they will be way overspecified and the loss in strength with cow hitching will be unimportant though. I think the clamping on effect will occur as they are going around a loop with a significantly thicker diameter (if 14 mm line is used for both the bridle and the loop then the effective diameter of the tripled loop is around 24 mm).

[Seaworthy Lass]

Conachair, would you suggest attaching the eye splices between the other sections of the drogue with cow hitches or just looping one eye through the other before splicing?

My thoughts are going back and forth like a ping pong ball at the moment .

A cow hitch may not “glue on” here are the diameters are fairly similar and the normal configuration of a cow hitch may not occur, rather the join may stay looking like the “interconnecting loops” that Dockhead illustrated. If the interconnecting loops structure remains, then the tight bends are not occuring and so the loss of strength may not be as great as expected.

In the scheme of things it may make no practical difference, but it would be nice to know anyway.

SWL

[s/v Jedi]

Originally Posted by Seaworthy Lass

Zero issues with tearing forces at the base of the eye splice of the leader, as you would get if you cow hitched the bridle legs directly to the eye of the leader or if you used any kind of thimble.

How about eliminating the weak link altogether. In this diagram, take out the loop, form the blue “empty” cow hitch in the leader, then cow hitch the red bridle legs onto the loop formed by the empty blue cow hitch

I’m really bad with diagrams and using just an ipad so I hope my description makes sense

[Seaworthy Lass]

Originally Posted by s/v Jedi

How about eliminating the weak link altogether. In this diagram, take out the loop, form the blue “empty” cow hitch in the leader, then cow hitch the red bridle legs onto the loop formed by the empty blue cow hitch

I’m really bad with diagrams and using just an ipad so I hope my description makes sense

Oh, yes, it makes perfect sense!

What a lovely way to simplify this. Brilliant suggestion!
I would in this case not cow hitch the red loops (bridle) on the other cow hitch though, I would simply cow hitch the leader onto the eyes of the bridle (what everyone was doing before was cowhitching the bridle onto the leader). I think this would work wouldn’t it?

SWL

[Seaworthy Lass]

Jedi, when I am back on board later today I will mock it up to scale like BW suggested.

I think this is the easiest way to look for flaws.

SWL