Stealth mode - New Generation Ropes

[Dockhead]

Originally Posted by BigBeakie

I have seen thimble edge chafe on rope with regular open thimbles, but what about these Hampidjan closed & welded gussett ones. I can't see how Acera would chafe if using these.

Wire Thimble Stainless Steel With Gusset

Does anyone have any experience using these & any feedback on chafe or lack of?

The connection of the JSD bridle arms to the JSD leader line loop has been bothering me re chafe & the cow hitch. During a multi day storm, somehow it just seems reassuring to have beefy thimbles like these rubbing on beefy Crosby 209A shackles all moused up.

Shame we don't have a "like" button on CF.


I have never seen thimbles like this, and they look the dog's danglies to me.


Made in Denmark and sold into the fishing industry as a "tube thimble"; available here: http://www.greenlinefishinggear.com/...le-with-gusset



I think we have several good ways to do this now -- it's been a great discussion, and kudos especially to SWL for pointing out the challenge.


Thimbles like that would have a lot of uses on board -- I'm going to look for a supplier here. Those plus a beefy shackle or a lifting master link look very good to me.


However, one reason to continue considering soft solutions is WEIGHT. We don't talk about this much, but the weight of this whole system is very important for deployment in what might be a stressful, difficult situation. The soft solutions will be lighter.

[thinwater]

Originally Posted by Fi2010

...We feel the published information suggesting longer bridles will likely lead to shock loading and bridle twisting. Fiorentino recommends the use of shorter bridles to reduce this issue. It contradicts what's suggested by the entire industry, but it does perform better regardless of angle of pull. Only something to consider....

I'm going to side with Firoentino on this one, or at least point out that this issue is important.


If the legs are too long and the boat is yawing crazily as they sometimes do in confused waves, one leg can go slack. This is a bad thing, as chafe is increased, and more importantly, all cordage types dislike being slack and then loaded hard. They last much longer if at least a small load is maintained. You can Google this, or merely accept experience.


The best compromise in length? I'm sure it depends on many factors, but I doubt you want the apex angle less than 45 degrees. This is only 22 degrees to each side. I'll leave this to others.

[Dockhead]

Originally Posted by thinwater

I'm going to side with Firoentino on this one, or at least point out that this issue is important.


If the legs are too long and the boat is yawing crazily as they sometimes do in confused waves, one leg can go slack. This is a bad thing, as chafe is increased, and more importantly, all cordage types dislike being slack and then loaded hard. They last much longer if at least a small load is maintained. You can Google this, or merely accept experience.


The best compromise in length? I'm sure it depends on many factors, but I doubt you want the apex angle less than 45 degrees. This is only 22 degrees to each side. I'll leave this to others.

If the legs are too long, the boat WILL yaw more, because reducing this angle reduces the force from the drogue correcting the yaw. One of the main purposes of a drogue is to stabilize the boat from yawing, and you reduce this effect with longer bridles.


Can you shorten the bridle and increase the yaw damping effect of the drogue? I say again, I don't think we can just fantasize -- this is a serious design question. It's not just the static, but dynamic behavior -- there is also tuning involved. I think obviously there will be an increase in resistance to yawing, but will it be beneficial? Is there such thing as too much? Will this affect tuning?



Shortening the bridle legs and increasing the angle will also increase forces on the connection, and on the bridle legs. At what point does this eat into the strength reserve of the system? I have no idea, but it should be calculated before willy-nilly messing with the bridle length.



I would not do this without design work and testing being done. 2.5:1 for me, thanks, as per the original designer's work, as verified by decades of experience.

[Fi2010]

Originally Posted by Dockhead

There have been a couple of comments in this thread suggesting varying the length of the bridles.



This sounds dangerous to me. The geometry of the bridle determines the yaw angle at which the drogue will start to correct the yaw. I think the bridle length is critical, and shortening or lengthening it compared to the design will change how the drogue works. I carefully and strictly followed Jordan's design, myself.


If someone wants to try longer or shorter bridles, I think a lot of testing would need to be done to verify what effect it has on performance. I'll stick to the design, myself.

Go with what you feel is best. Keep in mind, what's on paper doesn't necessarily play out the way you think it will in real-life.

You definitely should test out the equipment to see how your boat reacts to differing lengths. Boat design does factor into it. Current YouTube videos (not published by our company) demonstrate bridle problems. Unfortunately, issues with the bridle tend to be downplayed by the video producers. So pay attention to the bridle in any video.

If the rode is slackening you have an issue, because loading is placed on one side of the boat. This can cause a boat to round up in heavy weather giving oncoming waves an opportunity to knock down your boat. It also generates shock loading that can break rodes or fittings rather quickly.

The equipment we manufacture has been well tested. We're confident our rigging setups are sound. It does help to have worked with a commercial fisherman with deployment experience dating back to 1947.

[thinwater]

Originally Posted by Fi2010

....We believe a true drogue comparison is when you deploy only manufactured drogues. Drogues actually designed for heavy weather use. It’s how Practical Sailor conducted past tests....

Lamentably, articles are often trimmed viciously for space. My report was about 6 times the printed length.



Testing of all drogues was conducted in up to 35 knots in crummy weather. No particular weakness were revealed, other than the global tendency to pull out of steep wave faces. This is how I learned of that effect--field testing in unpleasant conditions, but short of dangerous. Testing continued under power in clam weather, because you cannot get consistent speed-drag data when waves are pushing you around.



To get maximum shock loads you actually deploy the drogues under light tension (10-20 pounds), so that they are open and properly aligned when the load comes on.



I think many are concerned that the shock load on opening will be "massive," but in fact he showed and I have observed, that it really isn't that much. Certainly nothing compared to waves strikes and surfing, and so as long as the system is well engineered (no knots!), the opening shock is a non-issue.

[Dockhead]

Originally Posted by Fi2010

Go with what you feel is best. Keep in mind, what's on paper doesn't necessarily play out the way you think it will in real-life.

What do you mean by this? That we shouldn't consider the design work ("what's on paper") to be valid? So what is more valid than this, then?

Originally Posted by Fi2010

You definitely should test out the equipment to see how your boat reacts to differing lengths. Boat design does factor into it. . . .

So how do I "test out the equipment"? Go out into the North Sea intentionally in a Force 9, and toss it out? Having actually been in the North Sea in 24 hours of a Force 9, I don't think so.



I might play with it in more benign conditions, but unless there is something dramatically wrong with the way the boat handles, I don't think this is going to provide much useful information, as opposed to useful practice in using it.


I think the most useful information we have, by far, is the accumulated experience of people using these devices in real life storms. So if you have some links to people telling about real life problems they had with JSD's due to bridle length, that would be really useful.


Otherwise, without any actual design work, without any actual testing of different lengths in real storms (and not in benign conditions), I think this is all just mental masturbation.

[Fi2010]

Originally Posted by Dockhead

Shame we don't have a "like" button on CF.


I have never seen thimbles like this, and they look the dog's danglies to me.


Thimbles like that would have a lot of uses on board -- I'm going to look for a supplier here. Those plus a beefy shackle or a lifting master link look very good to me.

We have approximately 17 of these stainless tube thimbles sitting on our shelf. We used them for a military project some 18 years ago. The thimbles are designed for 5/8 in. rode. Just send us an e-mail. We're sure you'll like what we have to say, since we want to dump the thimbles. We have no use for them.

[Dockhead]

Originally Posted by thinwater

. . . other than the global tendency to pull out of steep wave faces. . . .

Universal among single element drogues, right? Can you elaborate?


I used a parachute drogue once, from the bow, as per the Pardeys' ideas, years ago. In bad but not survival weather. I hated it, and hated the idea of being held bows into the waves. The boat yawed like at anchor (didn't help that the rode was nylon I guess), and it felt dangerous and unstable.



I do heave to sometimes in bad weather, but only for rest or repair. I am comfortable running off up to much worse conditions, than I am comfortable hove to. Being hove to (unlike lying to a parachute drogue) IS an inherently stable posture, but you are still vulnerable to having the head knocked down by a wave which catches you the wrong way; plus you can be becalmed in the troughs and wallow, if the waves are big enough to blanket the sails. This is also dangerous.



So I run off, and have trailed warps on occasion, which works really well on my boat, which has a very large, powerful rudder and is very stable when going downwind. Other boats like different things; being hove to works better and up to bigger conditions in full keel boats which leave a bigger slick, than on my boat with her bulb keel.

[Seaworthy Lass]

Originally Posted by Breaking Waves

The general rule is “the throat of a splice when it is loaded should be 30 degrees or less”. For safety margin, particularly with high modulus fibers, some people half this to 15 degrees.

In the drogue bridle application, assuming the bridle legs can slide on the rode loop, this angle will be determined by the length of the bridle arms and the width of the transom (the three sides of the triangle).

For a transom which is 10ft wide, you need 19.3 ft bridle lengths to create a 30 degree angle and 38.3 ft bridle lengths to create a 15 degree angle.

That would seem to be the simplest way to keep the throat angle issue under control. However, there are other solutions. You could design it so the brindle arms cannot slide apart on the loop – for example instead of two separate bridle arms you could just have one continuous one with only one cow (or prussic) hitch to the rode loop. There are also hardware solutions – a delta plate with thimbles would be the standard commercial solution – but that would add weight and ‘hard bits’ to what is a nice light and soft textile solution.

Using a textile loop at the join solves the throat angle issue, but adds a 'hoop loading' discussion, which is perhaps a topic for another day.

Originally Posted by Dockhead

This is really useful.

The Jordan design calls for bridle legs 2.5x the distance between the attachment points, which gives a throat angle of 23 degrees.


I guess that is probably reasonably ok with a long bury splice, isn't it?

But a simple solution to this would be to simple create the splices in all three parts, so that they are looped together. Then there will be purely straight pull on every eye and zero throat angle, no? The eyes of the two bridle legs can't slide apart, if they are looped through each other.

The only thing I can't quite visualize here is the half-turn of twisting which you would get -- would that be harmful? I wouldn't think so, but I can't quite visualize it.

Hi guys
Sorry for the delay replying. I have been offline most of the day.

The angle I am talking about is not the angle the bridle makes with the leader.

It is not just a case of looping the three legs together. The same problem would exist. It is an issue with the throat angle of the eye of the leader.

Below is a diagram of what I think will occur when the load is distributed equally between the legs of the bridle. The eye of the leader will form an equilateral triangle. It matters not if the eyes of the legs of the bridle are cow hitched or spliced on. There will be a tearing force at the throat of the eye of the leader. Unlike the usual tearing forces at this point when load is applied to the peak of the loop, it does not matter how big the eye of the loop is (the 60° geometry will always exist).

With a 60° throat the tearing force is 29% of the total load. I think this will fairly easily rip the base of the throat of the leader apart and the entire drogue will be lost.

SWL

PS If someone could please check the formula it would be good. My trig skills are OK, but physics is not my forte .

[Fi2010]

Dockhead,


All the information you're asking for has already been posted in the forum and online. We don't want to get caught up in a back and forth finger pointing session. We get it. You feel strongly about your product. So do we. However, we're still open minded into accepting that different sailors want to approach storm management differently. Hence, our mention that we accept trade-ins and purchase used JSD equipment for resale. Not just para-anchors and speed-limiting drogues.

Likely everyone already knows to practice using drag device equipment in calmer conditions to find out if there's any issues. To take the mystery out deployment. Kind of the same concept as anchoring overnight for the first time. You're all nervous, waking up every hour only to figure out by morning you were worrying about nothing.

[Dockhead]

Originally Posted by Seaworthy Lass

Hi guys
Sorry for the delay replying. I have been offline most of the day.

The angle I am talking about is not the angle the bridle makes with the leader.

It is not just a case of looping the three legs together. The same problem would exist. It is an issue with the throat angle of the eye of the leader.

Below is a diagram of what I think will occur when the load is distributed equally between the legs of the bridle. The eye of the leader will form an equilateral triangle. It matters not if the eyes of the legs of the bridle are cow hitched or spliced on. There will be a tearing force at the throat of the eye of the leader. Unlike the usual tearing forces at this point when load is applied to the peak of the loop, it does not matter how big the eye of the loop is (the 60° geometry will always exist).

With a 60° throat the tearing force is 29% of the total load. I think this will fairly easily rip the base of the throat of the leader apart and the entire drogue will be lost.

SWL

PS If someone could please check the formula it would be good. My trig skills are OK, but physics is not my forte .

But there won't be any tearing force, if the bridle leg eyes are looped together. They won't slide apart then.


Downside is you would have to splice all three parts together, and you couldn't take them apart easily. But that's probably not a big deal.


Did you get what I meant? Probably I didn't explain it well:


Two bridle legs -- make one long eye splice, then make the one in the other bridle leg after looping the end through the other eye splice.







Then loop the unspliced end of the first drogue section through BOTH eye of the bridle legs, and splice.





There would be no tearing force at all, since the bridle legs are joined together.

[thinwater]

Originally Posted by Dockhead

Universal among single element drogues, right? Can you elaborate?...

I'm talking about slowing drogues, like the Delta Drogue, Galerader, Seabrake, Shark, or similar. Parachutes and JDSs are different.


If the wind is really strong, the drogues run very close to the surface, held down primarily by the water flowing over them. Weight becomes a reduced factor. The rope rode becomes tightly stretched. If the waves are steep enough to be breaking dangerously,then when a steep wave face catches up to the drogue (the waves are moving much faster than the drogue) the drogue the rode will be pulling slightly up from the water, like an anchor at short scope. The drogue can then pull out of the face. Instantly, tension drops to nil and the nylon (this is why nylon is bad) rode recoils, flinging the drogue forward. Sometimes this will happen cyclically, every few minutes.


The theory is to place the drogue out of phase with the boat, but that does not always work. A very long rode helps.


A JSD has many cones and it rides deeper in the water. A chute is so large that it can resist this.


Experiences are not universal. Mutihulls generally hang well from chutes and do not yaw, but heaving to is very bad. My last boat was center cockpit, and taking waves from the back was fine and comfortable. My current boat has an open transom, and sometimes the cockpit gets wet in 12 knots, if I slow down suddenly; a slowing drogue would be idiocy.


It's a really tough topic to research. Testing is tough and everybody comes at it from a different background. Personally, my interest has always been coastal storms and emergency steering; those topics are more relevant to 95% of us. But as a result I have few opinions on survival storms, since I've never been in anything stronger than a gale. And I'm happy about that!

[Seaworthy Lass]

Originally Posted by Breaking Waves

On SWL's loop idea of a loop - thinking about it, I would just make it super super strong and then you can forget the hoop loading engineering. Easiest way would be use large diameter line, to make really big loop (which you would need to do anyway to get the proper bury), then fold it back on itself so you have three loops (not more because if more the legs will not self-equalize in length) That would then never ever be the weakest link. You could then either cow hitch to this loop (would minimize chafe), or spice loops into it (slightly stronger excluding chafe))

DH, there would be many different ways to join the three pieces together so you don't have any throat issue. You could for instance, really easily just lash the two cow hitches together so they can't slide apart on the loop. or as I suggested above, just use one continuous bridle line. Or as you suggest interlock the loops. I do not know what is the preferred solution. The engineering analysis is doable but a bit more complex than normal because of all the pieces and load directions. I will have to ask around - I am sure it is an already solved problem, just not very commonly used.

On bridle length - personally (my opinion), not for strength issues but for cone placement in the water, is that more like 50-60' long bridle arms is preferable. But thats based just from observation of JSD in action, not any particular analysis or engineering.

I have spent the day visiting a couple of fishing chandleries in the Netherlands. Gear is available that is not seen in yachting chandleries. Stainless steel or steel Crosby loop options do not look good.

Regarding soft loop options, Dockhead’s 14 mm line needs a loop >2 m in circumference (the legs need to be buried a bit over a metre). Our bridle is 12 mm Acera, so a bit less, but still big. I think twirling this around once or twice to decrease diameter and decrease the amount the eye spice of the bridle legs would slide would be good. It would also mean thinner diameter rope could be used,

By the way, cow hitching the legs of the bridle would not actially minimise chafe, as they would usually given that that “clamp” on. The cow hitch would slide on the slippery UHMWPE when under load. When the load is on one leg of the bridle, they will slide to be 180° from the leader. When the load is equal between the two bridles the cow hitches will slide 60° away not matter how firmly clamped on they are. Not goid for chafe!

SWL

[Fi2010]

Originally Posted by Dockhead

Universal among single element drogues, right? Can you elaborate?


I used a parachute drogue once, from the bow, as per the Pardeys' ideas, years ago. In bad but not survival weather. I hated it, and hated the idea of being held bows into the waves. The boat yawed like at anchor (didn't help that the rode was nylon I guess), and it felt dangerous and unstable.

I do heave to sometimes in bad weather, but only for rest or repair. I am comfortable running off up to much worse conditions, than I am comfortable hove to. Being hove to (unlike lying to a parachute drogue) IS an inherently stable posture, but you are still vulnerable to having the head knocked down by a wave which catches you the wrong way; plus you can be becalmed in the troughs and wallow, if the waves are big enough to blanket the sails. This is also dangerous.

So I run off, and have trailed warps on occasion, which works really well on my boat, which has a very large, powerful rudder and is very stable when going downwind. Other boats like different things; being hove to works better and up to bigger conditions in full keel boats which leave a bigger slick, than on my boat with her bulb keel.

Actually, the JSD has the same issue as the single element drogues as written in Jordon’s 1987 CG report.

We’ll have to take you on your word about your drag device experiences. Sounds like you failed to remove the slack in the rode setup. We’ve already mentioned the solutions so we won’t repeat.

From our experience, as well as the Pardeys, a boat that heaves-to easily tends to ride to a para-anchor rather easily.

Whatever storm tactic you choose you want to be comfortable. Boat design will factor into the equation.

[Seaworthy Lass]

Originally Posted by Dockhead

But there won't be any tearing force, if the bridle leg eyes are looped together. They won't slide apart then.


Downside is you would have to splice all three parts together, and you couldn't take them apart easily. But that's probably not a big deal.


Did you get what I meant? Probably I didn't explain it well:


Two bridle legs -- make one long eye splice, then make the one in the other bridle leg after looping the end through the other eye splice.



Attachment 190771



Then loop the unspliced end of the first drogue section through BOTH eye of the bridle legs, and splice.


Attachment 190772


There would be no tearing force at all, since the bridle legs are joined together.

Let me think about that. Looks good at first glance.
Dinner calls though. We have been on the road all day without breakfast or lunch and we are STARVING .

SWL