Stealth mode - New Generation Ropes

[Breaking Waves]

been at 'work', testing ocean drop of two prototype 'quad parachutes' systems. Both failed. Fortunately for me, the parachutes failed and not the rope work. But that also means the rigging did not really get loaded/application tested, so I don't know, my piece may be the next link to fail.

If you flatter Thinwater enough, he might rig up a dynamic testing setup which could identify any chafe concerns (for a PS article). You just need something like an eccentric wheel motor drive. You could also measure the dynamic loading on the bridle arms under yaw - they never seemed to me to be too 'snatchy', but that will be a function of vessel tracking capability and I may also just have been distracted by other things and not noticed it.

<fxykty>
>>F8 ... seems to be stable ...keeps things on track.
>>Of course, in survival conditions all bets are off. A JSD will certainly help >>keep things on track.

I personally am quite interested in the 'best drogue for the conditions' question. The primary purpose and probably best configuration is likely different for a lowish fetch F8 than for a southern survival storm. I prefer to use a single element for situations where keeping the boat tracking & not-surfing (or slowing down for a daylight approach in bad weather), and just to reduce stress and fatigue on the crew, are the primary requirements. They are easier to retrieve, which both makes the more likely to be used and less work/fatigue to clean up afterward. But they have known problems when the waves get both bigger/steeper when you want to switch to series drogues.

The Jordan has had pretty good success. but I have never been convinced that it is for sure the be all end all Series design. I personally see it more as a quite good starting point than the ultimate possible expression.

Survival wavelength and size and steepness can be quite different say near the Azores vs deep in the Pacific vs approaching say the horn shelf vs the gold stream. I know with a single element the rode length is optimally different in some of these situations. I presume the same is true with a series, but have never seen anything on it nor played around myself (usually when you get out the series you are not very interested in testing unproven things).

[Juho]

Here's one more possible knot. Also this knot is symmetric in all three dimensions. The main idea is to keep the two incoming lines in each direction strictly next to each other. Also this knot seems quite stable when the loads in the lines change. This knot can be undone by hand, at least if tightened by hand . Start undoing the knot from the outer loops of second picture and bend them over. The third picture shows the reverse side of the knot.

[thinwater]

Lots of great discussion. Really. I'm going to off topic just a few inches to answer a question that came up a few pages back.


Yes, I've seen single leg loading and really, really slack legs in testing. I was using a bridle with legs about 2x beam. I was in a gale with really nasty waves from two directions, nearly 90 degrees apart. Occasionally a wave would yaw the boat enough to cause one bridle leg not just to go slack, but to fall right down in the water. With waves coming up from behind, ANYTHING protruding from the transom could snag a bridle line.


After I finished my tests, I took the drogues in (I tried several) and ran off with just a 1/2 jib at angle that split that of the two wave trains and better matched there speed, and the ride was MUCH better. Unusual, but true on that one occasion.



My point is that making certain you have nothing protruding is really, really important.

[Breaking Waves]

Originally Posted by thinwater

making certain you have nothing protruding is really, really important.

there have been multiple cases of bridles caught under wind vanes. So that is definitely a real-world failure mode.

However . . . . there have been plenty of people (including myself) who have used vanes and drogues w/bridles with no problem at all.

I'm not sure what cause or prevent the problem. I used long bridle arms, which you believe should exacerbate the problem, but I never experienced it.

I've had drogues out in cross seas - usually tried to split them, or favor the side which would put the next wind shift more behind us.

We did usually try to keep some pressure & speed on the boat and not let it wallow at all. I would guess that helped keep the bridle lines from big slack.

Not statistical, but my guess is that a majority of 'incidents' are after the worst of a storm has happened a cross sea has developped and the wind has dropped, and the boat does not have as much pressure on it.

different vessels probably track/yaw differently, but I would have guessed your cat would balance and track well and not yaw hugely. It may be because of the beam that yaw creates more slack on a multihull ?

I guess I don't really understand the dynamics of the whole yawing thing. I just always tried to sail the boat so that it felt happy - not much into the 'chuck the drogue out the back and sit below until it is all over' school of thought.

[thinwater]

Originally Posted by Breaking Waves

there have been multiple cases of bridles caught under wind vanes. So that is definitely a real-world failure mode.

However . . . . there have been plenty of people (including myself) who have used vanes and drogues w/bridles with no problem at all.

I'm not sure what cause or prevent the problem. I used long bridle arms, which you believe should exacerbate the problem, but I never experienced it.

I've had drogues out in cross seas - usually tried to split them, or favor the side which would put the next wind shift more behind us.

We did usually try to keep some pressure & speed on the boat and not let it wallow at all. I would guess that helped keep the bridle lines from big slack.

Not statistical, but my guess is that a majority of 'incidents' are after the worst of a storm has happened a cross sea has developped and the wind has dropped, and the boat does not have as much pressure on it.

different vessels probably track/yaw differently, but I would have guessed your cat would balance and track well and not yaw hugely. It may be because of the beam that yaw creates more slack on a multihull ?

I guess I don't really understand the dynamics of the whole yawing thing. I just always tried to sail the boat so that it felt happy - not much into the 'chuck the drogue out the back and sit below until it is all over' school of thought.

It was a firm warning. I think it is more a matter of taking a good close eye to any potential snag points or sharp edges and doing something about them.



Remember that during testing I was often TRYING to make it worse. That is kind of the point; can I break something or find a failure mode? In the case I explained, had it been a little stronger, probably some combination of asymmetrical legs and a scrap of jib would have been best. In truth, the sailing was not so bad on some courses.


In fact, I intentionally chose courses that resulted in the worst yawing, just for fun. Once I started sailing again, I could leave a glass of water on the table! But cats can be really bad in a steep beam sea. In this case, one rudder would come out of the water, reducing yaw stability for a few moments. Not for beginners and not something I would ordinarily allow. I did not stay like that longer than need be!

[Breaking Waves]

Originally Posted by thinwater

It was a firm warning. I think it is more a matter of taking a good close eye to any potential snag points or sharp edges and doing something about them.

yes, and a very good one, when relying on a textile safety device!

The whole 'attachment to the boat' question is an important one.... has not been discussed much in this thread. It's not an issue with a thoughtfully custom built aluminum boat, but it is for most - both strength and a fairlead are essential and can be difficult.

I'm interested in the dynamic behavior of these devices. I don't really know that much about it. I'm guessing that usage (or not) procedure (pilot error) causes more 'failures' than technical errors (like putting knots in the system).

But it is all so hard to sort out because the actual really difficult situations are so rare. The vast majority of deployments are really in pretty simple strong gale conditions with some unpleasant shaped waves (although the crew at the time often think it is an extreme survival situation).

It was astonishing to me how poorly prepared the GGR fleet was, especially given they had signed up for a southern ocean off-season run! Friends in the longue route showed how it 'should be done'.

[Juho]

One more knot, in case someone is interested in using only one piece of rope, with only one working end to be tied, spliced, whipped or stitched somewhere somehow.

[Seaworthy Lass]

Originally Posted by Juho

One more knot, in case someone is interested in using only one piece of rope, with only one working end to be tied, spliced, whipped or stitched somewhere somehow.

It looks like a mini work of art .

[Dockhead]

Originally Posted by Seaworthy Lass

It looks like a mini work of art .

It's beautiful indeed, and beautiful knots are usually good knots, like other beautiful structures. Like.

[weavis]

Knots instill a line with weakness. I took a look at the strongest knot~and it surprised me that the figure eight knot gave @ 80% strength to the overall value of the line.

https://www.youtube.com/watch?v=GFlwrvggas0

[Dockhead]

Originally Posted by weavis

Knots instill a line with weakness. I took a look at the strongest knot~and it surprised me that the figure eight knot gave @ 80% strength to the overall value of the line.

I think those posting in this thread know that . That's pretty basic rope-knowledge.


Knots are even much worse with slippery cordage like UHMWPE, because most knots work on the basis of friction. That's why we splice almost everything when we're using UHMWPE.


Nevertheless, some knot or another might be worth the loss of strength if it solves a problem which is otherwise hard to solve, like chafe. We are all using cow hitches in our drogues at least when joining the tail sections, and we don't worry about that because we make them in the spliced loops where there is double the amount of cordage. So a cow hitch in a spliced UHMWPE loop around a reasonable bend radius should be pretty close to the basic strength of the cordage.


Some good basic reading:



https://www.marlowropes.com/rope-str...-how-retain-it


https://www.marlowropes.com/sites/de...ographic_0.pdf

[weavis]

LOL............. I didn't know that and hence I don't post coz I is iggerant regarding knot..s.. (Want to talk about body weight ratio to sedatives or anesthesia?)

However.. as a rope/knot virgin, and as an observer, I ask the questions that are outside of the exclusive knot paradigms of the solo rope user, ie the potential purchaser of a product.

Its a fascinating subject, yet I have to ask, given the findings of all you guys doing tests if a better/stronger/easier solution is not in a joint made of metal bracket to attach to? If chafe is an issue, does that not overide the value of even the best knot?

Jes askin'..........

I go back to drilling out my broken anchor pin.

[Juho]

Does anyone know what is the strength of spliced loops when compared to loops that are made with knots like figure-eight loop? In drogues also guaranteed reliability and reliability under cyclic loads are important. If knots are strong enough when compared to the strength of the rope and the other knots on the line, then using knots for making the required loops could be a good approach.

Edit: I note that weavis already gave the answer to the question of the strength of the figure-eight knot few messages back.

[conachair]

Originally Posted by Juho

Does anyone know what is the strength of spliced loops when compared to loops that are made with knots like figure-eight loop? In drogues also guaranteed reliability and reliability under cyclic loads are important. If knots are strong enough when compared to the strength of the rope and the other knots on the line, then using knots for making the required loops could be a good approach.

Edit: I note that weavis already gave the answer to the question of the strength of the figure-eight knot few messages back.

Some test data here >
https://web.archive.org/web/20160715...s.com/load.htm

Knots are a REALLY bad idea in dyneema, they slip slowly under load.

[fxykty]

Originally Posted by Juho

Does anyone know what is the strength of spliced loops when compared to loops that are made with knots like figure-eight loop? In drogues also guaranteed reliability and reliability under cyclic loads are important. If knots are strong enough when compared to the strength of the rope and the other knots on the line, then using knots for making the required loops could be a good approach.

Edit: I note that weavis already gave the answer to the question of the strength of the figure-eight knot few messages back.

As we’re speaking of UHMWPE line, which is very slippery, most knots end up at 50-70% of line strength (including the figure-8 referenced above, again due to the slipperiness and heat sensitivity of UHMWPE due to friction of slipping rope in a knot). Class 2 splices (as defined by Samson Ropes for use with Dyneema and other UHMWPE ropes) are between 90-100% of line strength (again, according to Sampson Ropes).

You give up a lot when knotting, hence this long thread and all the experiments to find reasonable no-knot solutions to the problems of connecting the rode segments (relatively straight forward with dressed or undressed cow hitches - though could be long spliced if that’s feasible with different diameter ropes) and the thornier problem of connecting the bridles to the leader.

Of course, you could use hard elements such as rings, shackles and/or bridle plates, but adding big hunks of metal to the system is anathema to some and plus has the issue of size and lack of availability due to the high working strength required to match the UHMWPE rope.