Stealth mode - New Generation Ropes

[Juho]

Originally Posted by Seaworthy Lass

My knitting needle set up is only very crude, but playing with it is interesting. It really brings home the message that the load is likely to be taken up very rapidly by the loose bridle, with sudden subsequent deceleration. Not ideal for non stretchy line.

Maybe you should hang models of all the interesting knots on the deck and in the wind somewhere, with some weights that capture the wind appropriately. If you have sufficient time to wait, you may see which knots start wearing out because of yawing and other movements.

[Seaworthy Lass]

Originally Posted by Juho

I made a knot with double loops (extra round) in all three lines. And those double loops are interlocked. I might also add some lashing close to the knot. I hope you can imagine the knot although I didn't include a picture of it.

Yes, if we need to try and stop the apex of the bridle eyes flopping then I think giving this extra turn to all three eyes instead of just one is an excellent idea. We might as well be hanged for a sheep as for a lamb .

It does secure the three legs very well and increase the bend ratio.

Originally Posted by Juho

That knot seems quite stable, and the extra rounds make the radius of the bends larger (might make the knot stronger). The two sides of the loop of each line are a bit further apart from each others than in a smaller knot, which may be a small problem (more chafe?), but maybe appropriate lashing would solve also this problem.

I think it would be extremely stable, as the full load is acting on the turn in the eye of the leader, clamping down on the bridle eye turns. UHMWPE is slippery, but I find it difficult to imagine the bridle eye under load shifting to the central location when the bridle eyes are being clamped like this. It is not the same situation as a couple of cow hitches simply attached to the leader.

I think the main potential problem is the 360° compression under full load. It still looks better to me though than cow hitches or other knots at this junction.

I know it has been said several times that no problems have been reported at this junction due to 3 eye splices and the bridle cow hitched on, but we have very little data with UHMWPE. None that I know of in the bad conditions encountered in the Southern Ocean, let alone multiple usage such as Trevor Robertson reported he has needed two seasons running.

I would like to get this junction in the drogue I am making as bullet proof as possible in the simplest, easiest way.

SWL

[Seaworthy Lass]

I have just woven this around using the ratty ends of the last trial without bothering with any eye splices. Looks like a rat’s nest .

The configuration is a very interesting one.

If the extra turn in the bridle eyes is made outward not inward, then the bridle eye legs end up right next to each other, so if they were able to centre under load despite the clamping, it is only half a bridle line diameter they need to shift.

I will mock it up properly shortly. It the compression is not considered a major issue and it is considered important to lock the apex of the eyes, this “Triple Clayton’s” looks like the best option yet to me.

SWL

This is my rat’s nest :

[Juho]

Originally Posted by Seaworthy Lass

I know it has been said several times that no problems have been reported at this junction due to 3 eye splices and the bridle cow hitched on, ...

I'd like to see tested knot patterns where the knot is guaranteed to be at least a bit stronger than the line itself. That is enough. It is much better to make a special knot in a long series drogue line of specified strength, than to make a knot that is the first place to break, and compensate that by using a heavier than required line.

We would thus need rope specific tests in different conditions on which knots have >100% strength.

[Seaworthy Lass]

Originally Posted by Juho

I'd like to see tested knot patterns where the knot is guaranteed to be at least a bit stronger than the line itself. That is enough. It is much better to make a special knot in a long series drogue line of specified strength, than to make a knot that is the first place to break, and compensate that by using a heavier than required line.

We would thus need rope specific tests in different conditions on which knots have >100% strength.

Although % losses knotting UHMWPE are higher than with polyester, as the knot is being tied in the eye that is only seeing half the load of the line, something may be achievable. The bend ratio with the Triple Clayton (for want of a better name ) interestingly does not seem to be less than 2:1 anywhere in the structure. A D/d of 2 gives loss of around 36% of potential eye strength (which is twice line strength) so that is helpful. The loss with compression I have no idea about, but it is a less complicated knot than the cow hitch, so maybe a bit better than 50% loss for the eye is achievable.

These are only the minimum breaking strength percentages for constant load applied slowly, which is what is generally tested. The actual situation with repeated bending at the junction and shock loads is difficult to reproduce and hard (impossible?) to estimate.

Those who are testing rope, such as Thinwater, would have a much better idea of what may occur and how it could be tested for.

I would personally be much more comfortable increasing the line diameter. This also helps with any chafe issues at the boat end. Even chafe covers get chewn through.

SWL

[thinwater]

This should get you thinking:


https://www.blackdiamondequipment.co...-together.html


MAMMUT'S RESPONSE TO SLING FAILURE - Alpinist.com


I've seen pull-testing of Amsteel that did much better than this. Like most knots, the results are material-specific. Just look at the range for 3 different (54-70%) Dynex materials.


One thought is that climbers could request stronger slings; they would still be more compact than the nylon we started with in the 70s. But they don't for the same reasons sailors don't want to go up in Amsteel size for JSds.



The idea that there is a knot that is stronger than the line is, well, not likely. People have been looking.

[Seaworthy Lass]

Originally Posted by thinwater

This should get you thinking:


https://www.blackdiamondequipment.co...-together.html


MAMMUT'S RESPONSE TO SLING FAILURE - Alpinist.com


I've seen pull-testing of Amsteel that did much better than this. Like most knots, the results are material-specific. Just look at the range for 3 different (54-70%) Dynex materials.


One thought is that climbers could request stronger slings; they would still be more compact than the nylon we started with in the 70s. But they don't for the same reasons sailors don't want to go up in Amsteel size for JSds.



The idea that there is a knot that is stronger than the line is, well, not likely. People have been looking.

I had to look up what a girth hitch was. Wow! It’s a cow hitch!

This comment from the second article is very relevant to the drogue. I think eyes function much like slings, but they are worse due to tearing forces at the base of the throat:

“....slings, whether skinny or fat, Dyneema/Spectra or Nylon, are susceptible to significant strength loss due to a girth hitch, and should use any connecting knots with extreme caution. The safest way to obtain a longer sling is to carry and use a longer sling in the first place, rather than connecting them at all”.

It would be good to know how much the movement of the bridle leg not under load is of concern to know to know if it needs to to clamped with a knot. I would really prefer just to have the Y junction knot free. Just splicing the eyes around the leader achieves this. Doing anything fancier at this junction just looks like asking for trouble.

SWL

[thinwater]

Originally Posted by Seaworthy Lass

I had to look up what a girth hitch was. Wow! It’s a cow hitch!

This comment from the second article is very relevant to the drogue. I think eyes function much like slings, but they are worse due to tearing forces at the base of the throat:

“....slings, whether skinny or fat, Dyneema/Spectra or Nylon, are susceptible to significant strength loss due to a girth hitch, and should use any connecting knots with extreme caution. The safest way to obtain a longer sling is to carry and use a longer sling in the first place, rather than connecting them at all”.

It would be good to know how much the movement of the bridle leg not under load is of concern to know to know if it needs to to clamped with a knot. I would really prefer just to have the Y junction knot free. Just splicing the eyes around the leader achieves this. Doing anything fancier at this junction just looks like asking for trouble.

SWL

BUT, the cow hitch eliminates motion, and thus chafe. This is why we need to KNOW if there is ANY history of chafe at this join. Surely someone knows whether it chafes at all, or not. My understanding that that experience says it does not. Is this true... or not? It doesn't need to be a failure. Just chafe. I have not heard of this reported.


As for tearing of the splice throat, the effect seems to be less than the weakening in the girth hitch, so it does not matter so long as the eye is long and the bridle apex angle is less than 90 degrees.



"Is a puzzlement...."

[Seaworthy Lass]

Originally Posted by thinwater

"Is a puzzlement...."

Thinwater, if you were making a drogue using UHMWPE today, what would you do? I guess you would not want to recommend what someone else should do, but what would you do personally?

You have lots of experience with climbing and with load testing rope. Combined with sailing and having an engineering background it probably makes you one of a handful of people worldwide best qualified to come up with the most reasonable thing to do. We have negligible data on UHMWPE drogues used in earnest to help with the decision making process.

SWL

[Seaworthy Lass]

Originally Posted by Juho

I made a knot with double loops (extra round) in all three lines. And those double loops are interlocked. I might also add some lashing close to the knot. I hope you can imagine the knot although I didn't include a picture of it.

That knot seems quite stable, and the extra rounds make the radius of the bends larger (might make the knot stronger). The two sides of the loop of each line are a bit further apart from each others than in a smaller knot, which may be a small problem (more chafe?), but maybe appropriate lashing would solve also this problem.

The interlocking idea may be good in eliminating the risk that two of the lines rip the end loop of the third line apart when they pull in different directions. The double loops do the same thing to some extent, but maybe it does not harm to use both tricks.

By the way, below is how I interpreted your description of doubling the loop on all three eyes. The bridle legs are not interlocked with each other, but both are locked by the leader. It is based on WSmurdoch’s single version, modified to delete the cow hitches, that I called a Claytons. So it seemed logical to call the tripled version a Triple Claytons .

I find it an intriguing option for the junction if a knot has to be incorporated to stop the apex of the bridle eyes from moving when not under load. I can’t see one single portion that has the bend ratio D/d less than 2. I haven’t seen another knot like that.

SWL

These is how the top and bottom looks. It appears to be “kinder” on the line than a cow hitch:

[thinwater]

Originally Posted by Seaworthy Lass

Thinwater, if you were making a drogue using UHMWPE today, what would you do? I guess you would not want to recommend what someone else should do, but what would you do personally?

You have lots of experience with climbing and with load testing rope. Combined with sailing and having an engineering background it probably makes you one of a handful of people worldwide best qualified to come up with the most reasonable thing to do. We have negligible data on UHMWPE drogues used in earnest to help with the decision making process.

SWL

With so little field data, it's tough. I would go with the number of cones recommended for the boat size (not more) and reinforce them as some have (but perhaps one weak "wear indicator" cone), but on the bridle and first cone section, I would make sure I was at the upper end of the strength range (including cruising load). With polyester and nylon, that would mean a lot of bulk, but with Dyneema, not so much. But I would not go up a size in general. I would go with the cow hitch construction because there is more experience with it, not because I love it. It seems like there should be a better connection, but nothing is jumping out at me yet.

[s/v Jedi]

Originally Posted by Seaworthy Lass

With the load transferred to the right leg, the loose left one immediately slid towards the throat of the leader.

I did not nudge the line to achieve this. I did not have a hand or foot free to do it even if I wanted to (load had to be applied to two ends and I needed to get a light under the iPad and still be able to take the photo):

No, you can not bring the slack bridle leg to the throat of the leader splice. You can clearly see that the other bridle leg will prevent that from happening.

What you do here is the other way around: you bring the throat of the bridle leg to where the other parts meet. But when you transfer load back to that bridle leg, it will never pull at the throat of the leader but instead shift back to it's original position before taking up the load.

The throat of the leader is the weak point. Any pull there must be avoided. Same goes for the throat of the leaders but I believe both interlocked loops and the extra round turn achieve that. The problem with the extra round turn is that it can move/roll when load shifts from one bridle leg to the other. This happens under strain, which means a lot of heat will be generated and that is a failure mode for rope. It's how the guy in that video can break the line with his bare hands.

If it's for me (I don't have any drag device) I would use the interlocked loops

[wsmurdoch]

Sailing along this morning watching the dinghy bridle pull on the painter as the following waves yanked it about, I wondered... How about just a simple square knot tied in the three eye splices?

The knot only needs 50% strength to match that of the single line. All the loads are nearly on the stress axis decreasing the fatigue causing twisting as the load shifts from one bridle leg to the other. The knot is symmetrical unlike a real square knot, so it should be a bit stronger. The bends are, for a knot, gradual, in fact more gradual than linked eye splices. The knot sets up stopping any wear causing sliding about. The splice throats are pressed shut.
Loss of one bridle leg is not a loss of the drogue. The junction can be assembled and disassembled without remaking a splice.

And, while looking for something else, I ran across load rated titanium rings with an offer to make bigger ones in case someone wants metal at the junction. TITAN CLIMBING - Producers of the worlds first certified Titanium climbing bolts, anchors and hardware - Anchor Rings

Bill

[Seaworthy Lass]

Originally Posted by s/v Jedi

No, you can not bring the slack bridle leg to the throat of the leader splice. You can clearly see that the other bridle leg will prevent that from happening.

What you do here is the other way around: you bring the throat of the bridle leg to where the other parts meet. But when you transfer load back to that bridle leg, it will never pull at the throat of the leader but instead shift back to it's original position before taking up the load.

The throat of the leader is the weak point. Any pull there must be avoided. Same goes for the throat of the leaders but I believe both interlocked loops and the extra round turn achieve that. The problem with the extra round turn is that it can move/roll when load shifts from one bridle leg to the other. This happens under strain, which means a lot of heat will be generated and that is a failure mode for rope. It's how the guy in that video can break the line with his bare hands.

If it's for me (I don't have any drag device) I would use the interlocked loops

I can’t grasp why the bridle legs need to be interconnected to stop the loose one from pulling on the throat of the leader. As far as I can see at the instance load is equalised before transfer, the only spot the previously loose bridle can be is right next to the other bridle. Maybe I am missing something?

[Seaworthy Lass]

Originally Posted by wsmurdoch

Sailing along this morning watching the dinghy bridle pull on the painter as the following waves yanked it about, I wondered... How about just a simple square knot tied in the three eye splices?

The knot only needs 50% strength to match that of the single line. All the loads are nearly on the stress axis decreasing the fatigue causing twisting as the load shifts from one bridle leg to the other. The knot is symmetrical unlike a real square knot, so it should be a bit stronger. The bends are, for a knot, gradual, in fact more gradual than linked eye splices. The knot sets up stopping any wear causing sliding about. The splice throats are pressed shut.
Loss of one bridle leg is not a loss of the drogue. The junction can be assembled and disassembled without remaking a splice.

And, while looking for something else, I ran across load rated titanium rings with an offer to make bigger ones in case someone wants metal at the junction. TITAN CLIMBING - Producers of the worlds first certified Titanium climbing bolts, anchors and hardware - Anchor Rings

Bill

Hmmmmmmm.

That is the the sound of me thinking.

I think this is the same as the “cow hitch of the leader onto the bridle legs option” that Jedi suggested a while back, but rather than dressing it as a cow hitch it is left undressed like Dockhead’s “interconnecting loops” at the start of this discussion.

Reading the first paper Thinwater posted a link to a few posts back, I think this is called a Strop hitch when it is done with just two loops.

Of all the cow hitch options this is the one I like best as it is not so convoluted, for want of a better word. The line looks less tortured and what I have referred to as “nasty” looking.

This is a simple option and may in fact work the best.

My mind is truly spinning at the moment. I need to make a decision with what to do at the Y junction. Juho’s triple doubled loop eye splice would need testing before it could be used and despite the good bend ratio the compression would be sky high. I don’t like conventional cow hitches, but I think hitching on the leader is far preferable to hitching on the bridle legs, as is apparently currently done (Breaking Waves and Dockhead). I vastly prefer no knot but don’t know the impact of leaving the bridle leg under load free to move around. I don’t really like the interconnecting loop option as I don’t think it solves much and just complicates the plain eye splice option.

The only thing I am certain of is I don’t like the way the bridle legs are currently cow hitched onto the leader. Also, whatever method is used, the three eye splices need to be long to minimise tearing forces at the throat.

This is giving me a headache. I will mull over this a few days, but your suggestion, which as far as I can see is really a undressed version of a cow hitch of the leader onto the bridle legs, may have the least potential problems of all the above alternatives (for all the reasons you suggest) and is only a modification of the current method rather than going off on a new tangent. That appeals.

To everyone contributing here: thanks for all the thought put into this and the input. Having lots of ideas tossed around is extremely beneficial. It is by far the most effective way of arriving most quickly at the best solution in the absence of any data or additional testing.

SWL

PS The titanium ring is interesting. It has a MBS of 5098 kg-f though, which is unfortunately low.