Stealth mode - New Generation Ropes

[Seaworthy Lass]

Thinwater, what do you think about ditching the concept of any knot and just having a soft loop tripled over with three eye splices with chafe protection looped through it?

It seems to eliminate most of the issues. The amount of sliding the legs need to do at the junction is small with a 2.5:1 bridle length (much smaller than I thought before seeing it mocked up). I tend to think chafe protection and oversizing the line would solve any issues with any sliding that will occur.

It is a pretty simple solution.

SWL

[Seaworthy Lass]

I picked up the simulation itself this morning to put it away. It has sat with no load in the pilothouse overnight. It is set like concrete. I will try soaking it to see if it softens and and I can get it apart with a marlin spike, otherwise I have wrecked three 8mm loops. An expensive trial, but very worthwhile for me.

The junction looks horribly stressed in compression and this is after not a particularly high load. Despite the cow hitch passing over two strands (two eyes of the bridle) in parts it is still bending over just one strand. I have attached a photo. Note at how the upper bits are splayed out with the compression.

Combined with all the information Thinwater has presented with bending and fatigue issues that may occur as load shifts, I don’t like a knot here at all. It just looks very nasty for want of a more technical term. Even if load testing results are good, that static condition clearly does not even vaguely simulate what will occur when the drogue is in use.

Personally, I think two cow hitches (which seems to be what is most commonly done currently except by the manufacturer of the Shark drogue who said they are using thimbles at this junction!!!) are even worse here. If I had to go with a cow hitch then Jedi’s idea of making this with the leader looks best for now.

Unless someone thinks it is a really stupid idea, I am going to go with a loop of 12 mm Acera twirled to create a triple loop (I will now have lots of 12 mm leftover). I will make the bridle and a short section of the leader overspecified at 14 mm substituting the 12 mm I have. I will add UHMWPE chafe protection on all three eyes, connected with the technique Breaking Waves showed (fraying the ends a long way and tucking the strands into the leg below the base of the eye).

This is a similar thing that would be done with a solid low friction ring, but I am substituting the ring with super strong soft loop (MBS roughly 80,000 kp if I use 12 mm Acera).

I will add chafe protection too to the portion of the bridle that will touch the boat.

Ping pong game is over for me .

SWL

[conachair]

One good bit of news is that Jeanne Socrates cones seem to be lasting well despite a lot of southern ocean deployment



https://svnereida.com/blog/5088-day-...oes-very-light

With the "all load on one leg" thing, tricky to guess what would happen there, might be better to listen to what people down there actually see. As the loads are so large I would guess the boat would get pushed back in line with the drogue before the load on a single line gets too massive. Quick sketch with bridle legs of 2.5 * the beam looks like a torque of 98% leg load * 1/2 the beam would be exerted along the centre line of the boat twisting it back in line plus maybe a lot of water. But guessing really.. still, even with Susie's awful experience JSD's hardly ever seem to break so a good dollop of over engineering should see you out the other side safe

[Dockhead]

Originally Posted by Seaworthy Lass

. . . I miss lots in other areas that is obvious to others. What is instinctive to one person, may take ages to sink in for someone else. Maybe to some people a short eye looks neat and snug. Maybe they think an eye that looks a bit like an eye going around a thimble is ideal. Hopefully no one has made up the very short eye I showed, but there may be ones sitting in lockers that are short enough to cause problems with tearing forces at extreme loads.

You're speaking for all of us there. This is what makes CF so great.

[Dockhead]

Originally Posted by Seaworthy Lass

I picked up the simulation itself this morning to put it away. It has sat with no load in the pilothouse overnight. It is set like concrete. I will try soaking it to see if it softens and and I can get it apart with a marlin spike, otherwise I have wrecked three 8mm loops. An expensive trial, but very worthwhile for me.

The junction looks horribly stressed in compression and this is after not a particularly high load. Despite the cow hitch passing over two strands (two eyes of the bridle) in parts it is still bending over just one strand. I have attached a photo. Note at how the upper bits are splayed out with the compression.

Combined with all the information Thinwater has presented with bending and fatigue issues that may occur as load shifts, I don’t like a knot here at all. It just looks very nasty for want of a more technical term. Even if load testing results are good, that static condition clearly does not even vaguely simulate what will occur when the drogue is in use.

Personally, I think two cow hitches (which seems to be what is most commonly done currently except by the manufacturer of the Shark drogue who said they are using thimbles at this junction!!!) are even worse here. If I had to go with a cow hitch then Jedi’s idea of making this with the leader looks best for now.

Unless someone thinks it is a really stupid idea, I am going to go with a loop of 12 mm Acera twirled to create a triple loop (I will now have lots of 12 mm leftover). I will make the bridle and a short section of the leader overspecified at 14 mm substituting the 12 mm I have. I will add UHMWPE chafe protection on all three eyes, connected with the technique Breaking Waves showed (fraying the ends a long way and tucking the strands into the leg below the base of the eye).

This is a similar thing that would be done with a solid low friction ring, but I am substituting the ring with super strong soft loop (MBS roughly 80,000 kp if I use 12 mm Acera).

I will add chafe protection too to the portion of the bridle that will touch the boat.

Ping pong game is over for me .

SWL

Did I miss something? Why did you ditch the low friction ring? That seemed like a solution without any downside provided you could find a strong enough ring.

[Seaworthy Lass]

Originally Posted by Dockhead

Did I miss something? Why did you ditch the low friction ring? That seemed like a solution without any downside provided you could find a strong enough ring.

Several reasons:
- I am comfortable with a soft loop. If I use 12 mm Acera it will be overspecified four fold.
- Hardware at this junction is an unknown entity.
- I haven’t found a solid alumium ring yet that is strong enough. The Crosby ones felt like they weighed a ton, so I don’t want to use steel.
- Having mocked the system up like Breaking Waves suggested I don’t think eyes of 14 mm Acera will be moving much as load transfers. The bridle eyes will be pretty much jammed against each other when the load is evenly distributed, so when load transfers they will need to shift very little (much less than I expected). Chafe is therefore less of a concern than I initially thought.
- Shortly we will be cruising again and at anchor so I won’t be able to have anything delivered until our next haul out and I need to make an executive decision so I can get this drogue sorted out.

Mocking up the system really brought home to me how horrid any knot is at this junction, so a soft loop seems the best option to me.
If the experts ultimately decide that this is not the case, it will be super easy to undo the eye splices and redo the junction.

SWL

[s/v Jedi]

Also, when considering possible failure, you will see evidence of an upcoming failure when using a Dyneema loop (broken strands, fraying etc.) while with any metal ring/shackle you need X-ray or (possibly) dye tests to search for initial damage. This is one of the BIG reasons to change from metal to fibers like soft shackles etc.

[thinwater]

Originally Posted by Seaworthy Lass

Thinwater, what do you think about ditching the concept of any knot and just having a soft loop tripled over with three eye splices with chafe protection looped through it?

It seems to eliminate most of the issues. The amount of sliding the legs need to do at the junction is small with a 2.5:1 bridle length (much smaller than I thought before seeing it mocked up). I tend to think chafe protection and oversizing the line would solve any issues with any sliding that will occur.

It is a pretty simple solution.

SWL

Honestly, all of these solutions are probably very safe. No knots, no sharp edges, no thimbles, no nylon. These are the problems that have contributed to losses. Weak cones are an issue, but from what I understand, have not caused losses.


If I thought there was any significant chance I would use it more than once (and I wouldn't sail those places!) I bet I would consider going up one size, or at least making sure I was in the top of the applicability range. In part, this is so I could replace the cones without risk. This does not apply to the number of cones, I think, but that might depend on the boat (more give in the drogue vs. less).


Great work!

[Seaworthy Lass]

Originally Posted by conachair

One good bit of news is that Jeanne Socrates cones seem to be lasting well despite a lot of southern ocean deployment

Originally Posted by thinwater

If I thought there was any significant chance I would use it more than once (and I wouldn't sail those places!) I bet I would consider going up one size, or at least making sure I was in the top of the applicability range. In part, this is so I could replace the cones without risk. This does not apply to the number of cones, I think, but that might depend on the boat (more give in the drogue vs. less).

Thanks for all the feedback
I do realise there are lots of unknowns here and any advice is given with hesitation, but it is nice to have my decision reinforced.

Those cones Conachair showed still look in good shape from what I can see.

Although I have a Sailrite sewing machine and my sewing skills are OK, I opted to purchase the cones from Ocean Brake in the UK. I was impressed with the construction of the cones that were delivered. Dacron was heavy duty (I can look up the weight if anyone wants to know). The raw edges were finished on both openings with Dacron “bias tape”. This has no raw edges. The cost was not much more than purchasing all the fabric and webbing and doing the job myself.

I did a lot of research before deciding on these. There have been issues with lightweight cones with raw edges disintegrating after one use.

One issue that has been brought up is that the drogue should not be a “once only” item. I disagree with this. I think given the fatigue issues Thinwater has raised, maybe we should consider the bridle and the first part of the leader (make it in two parts, one short, one long) as disposable. Climbers who need to use their safety line discard the nylon without any qualms. We should perhaps not hesitate to replace the first section of the series drogue after use.

SWL

[wsmurdoch]

Would simply putting a twisted loop in the eye of the drogue line before cow hitching the two bridle lines onto the loop cure two of the mentioned problems - the radius of the cow hitches is increased and the eye of the drogue line is not spread apart ?


Bill

[thinwater]

Originally Posted by Seaworthy Lass

...Climbers who need to use their safety line discard the nylon without any qualms. We should perhaps not hesitate to replace the first section of the series drogue after use.

SWL

I started to choke on this. Climbers retire lines, but not quickly (yeah, I was out cragging this morning). They consider both the number of very hard falls (very few are), look for damage, and consider general wear. Which leads to a crazy thought:


Maybe a few light-duty cones in the middle of the string (underwater section) would be a good wear indicator; when they are torn to ribbons, they are replaced, along with the bridle, leader, and possibly the first section. But this tells us about general wear, not peak loads.



It would also be interesting to have some manner of peak load indicator. In nylon rope, for example, you can bury a thread that will pull inside the rope when it stretches more than X%. I'm not sure how you could monitor peak load with Dyneema--clever ideas are welcome. It would be really nice to know if you hit, even once, say 50% BS.

[Seaworthy Lass]

Originally Posted by wsmurdoch

Would simply putting a twisted loop in the eye of the drogue line before cow hitching the two bridle lines onto the loop cure two of the mentioned problems - the radius of the cow hitches is increased and the eye of the drogue line is not spread apart ?


Bill

Hi Bill
Good to hear of options.

I think the eye of the leader (drogue line) line would still be spread apart by the two cow hitches under load.

Primarily though, it is still a knot. I think any knot here will suffer.

SWL

[wsmurdoch]

I tried it in the slick 1/4" blue rope that litters the beaches. This is with a 200 lb load on the drogue line with an impossibly wide angle between the bridle lines. The bridle lines migrated to the center of the once looped drogue line. I could not make it do otherwise.


And, you are right, it is still a knot although multiple loops in the drogue line might cover some of those faults.

Bill

[oldbilbo]

The above 'brainstorming' had me looking to emulate some of the ideas. I'm sold on the decision to use a multipart 'softy loop' to join bridle and leader and also interested in using rated lifting strops for the bridle legs, so dug out a couple I have, rated at 4T SWL with a stated SF of 7. I made up an overlong 'softy loop' in 5mm Amsteel I had, but chose not to cut it down, so wound several 'passes' through the three components. There's a length of 12mm Dynice Dux I had handy, which I've used to simulate the loop-splice of a leader, and some chafe-guard tubing.


I made up 4 configurations, largely to see what they looked like. The pics below are posted for interest, and the eagle-eyed will spot that a 'proper' button knot is emulated by something lesser.... and quicker.




IMG_5518 by oldbilbo, on Flickr






IMG_5519 by oldbilbo, on Flickr






IMG_5520 by oldbilbo, on Flickr






IMG_5521 by oldbilbo, on Flickr

[Seaworthy Lass]

Originally Posted by oldbilbo

The above 'brainstorming' had me looking to emulate some of the ideas. I'm sold on the decision to use a multipart 'softy loop' to join bridle and leader and also interested in using rated lifting strops for the bridle legs, so dug out a couple I have, rated at 4T SWL with a stated SF of 7. I made up an overlong 'softy loop' in 5mm Amsteel I had, but chose not to cut it down, so wound several 'passes' through the three components. There's a length of 12mm Dynice Dux I had handy, which I've used to simulate the loop-splice of a leader, and some chafe-guard tubing.


I made up 4 configurations, largely to see what they looked like. The pics below are posted for interest, and the eagle-eyed will spot that a 'proper' button knot is emulated by something lesser.... and quicker.

Hi Bilbo
It is good to have people thinking about options for the bridle.

I personally would prefer to keep the set up as simple as possible with the least stress and chafe potential and good load distribution.

I hate to sound negative, but I think the edges of the sling are a chafe point. The number of turns in your loop would mean good load distribution would be difficult. The bridle connected in this manner is one continuous line over a fair length (the edges of the sling are the stop points). The knots bother me for the same reason I am not happy using a cow hitch. But I do like your lateral thinking.

I think I will leave negative comments for others to voice from now on, as it doesn’t make me feel good continually shooting down other people’s ideas. There are plenty of members contributing here with more expertise than I do who could provide better constructive criticism.

SWL