Jordan Series Drogue in Dyneema

[conachair]

Originally Posted by HBrew

3. Recovery of the dyneema part was really hard because it slips in the winch. I was trying to tie rolling hitches to the line but they slipped too. So afterwards I tied knots in the dyneema at regular intervals so that the dyneema can be hauled in with lines attached.

Hope this helps.

Hamish

I had a play around on land with some dyneema , chocking a short length around the main part then feeding it in into the core created enough of a bulge for another piece to get a grip, would cause less weakening than a knot probably. Pics sort of show it --

[fxykty]

Originally Posted by Tillsbury

Re: hauling a jsd back in. Would there be any point in having a thin line and float on the end of it, such that you could circle round and pick it up then retrieve the jsd from the far end?

That kind of solution has been discussed at length at Morgan's Cloud site. Basically, given the very dynamic nature of breaking waves and the movement of the rode in the water, there is too much risk of tangling with and fouling the JSD.

Sure, Dyneema line is slippery. But it's not that slippery that you can't put turns on a winch and wind it in under load. And once you get to the cones you have lots of handholds.

I have 8mm Dyneema for my mainsail reefing lines and we have no problems using them - just use 6 turns on the winch instead of 3 or 4.

[Snore]

Originally Posted by Snore

I would suggest you ponder the loads placed on the attachment points to the boat.


Dyneema has almost zero stretch and could shock load the attachment points. Whereas a line with more stretch would ease the load onto the attachment points.

My post made valid irrefutable statements. You responded authoritatively that it was “absolutely not true.”

Originally Posted by fxykty

This is absolutely NOT true. Refer to the USCG data about the JSD and the Morgan’s Cloud site for correct information.

To paraphrase, the whole point of a JSD is to progressively involve more cones to increase the load; there is no shock loading in the system. The only exception is if the boat yaws and then the loading and unloading of the individual bridle legs can cause shock loads; but even these shock loads are a fraction of the total load.

Arguably, non-stretch line is better due to not storing any energy in the rode.

Perhaps my best reference point is the inventor of the device Mr. Jordan, see below.

Originally Posted by thinwater

… Don Jordan was asked about using Dyneema, and as I recall he replied that he would have like to have investigated it, and that if it made the drogues more practical, it was probably a good thing....

I will add one more thing. Dyneema does not tolerate chafe at all. Every storm related deployment of a Jordan discussed the need to deal with chafe, an uncovered dyneema line would require more protection.


Would I make or suggest a dyneema system? Nope. I would wait for some testing. The a big difference between me and many others, is that I am an never early adopter of DIY or untested safety gear.

[conachair]

Originally Posted by Snore

My post made valid irrefutable statements. You responded authoritatively that it was “absolutely not true.”

If that's the case then you have to say where the force comes from. A JSD system is completely different from an anchoring system, with an anchor it will produce an 'equal and opposite reaction' all the way until something gives, with a JSD system the force is a function of cone velocity. So where is this large shock loading coming from?

Perhaps my best reference point is the inventor of the device Mr. Jordan, see below.

Again, where is the force coming from? It may go from zero to the force on the rode quite quickly but it can't be more than that.

There's no source for these large dynamic loads you are thinking are there.

I will add one more thing. Dyneema does not tolerate chafe at all.

No more so than any rope under large tension, dyneema is used as cut proof gloves as it is cvery chafe resistant for it's size. Morlow D12 is very tough, I tested some 5mm short strops over a vicious winter in a SW UK marina running over rough edges and it fared very well. Fluffy but still lots of material undamaged.

[dougweibel]

Originally Posted by fxykty

Here’s how each section is connected to the next, using a modified strop bend (I think that’s the correct name for an undressed cow hitch). An alternative would be to end to end splice. Each eye is Brummel lock spliced.

I noted from your other post that you are using soft shackles in your system. I'm curious why you don't use one to attach sections? I used one on mine to make it easy to disconnect the tail end - in case of a steering failure the shorter front section could be deployed as a steering aid.

[mikereed100]

Originally Posted by HBrew

3. Recovery of the dyneema part was really hard because it slips in the winch. I was trying to tie rolling hitches to the line but they slipped too. So afterwards I tied knots in the dyneema at regular intervals so that the dyneema can be hauled in with lines attached.

Hamish

You may want to reconsider putting knots in the rode as that will weaken it. As far as recovery after deployment, we found that simply leading the the drogue to the bow and recovering by hand without winches was quite easy. The only time I have done this was in approximately 15 knots of wind and 1-2 meter seas with 3/4" polyester line, so somewhat different from your conditions, but something that you may want to try.

[StoneCrab]

Any comments on Attainable Adventure Cruising / Morgan's Cloud concerns about Susie Goodall's Series Drogue Failure?

They do an analysis of the strength of splicing loops and the underestimated load - actual - displacement of a cruising boat.

Take-away is that we should all add at least 30% to the designer's displacement number when specifying a Jordan Series Drogue.

A JSD should never be attached with knots. No figure eight or flemish loops...soft eye splices are ok.

[fxykty]

Originally Posted by dougweibel

I noted from your other post that you are using soft shackles in your system. I'm curious why you don't use one to attach sections? I used one on mine to make it easy to disconnect the tail end - in case of a steering failure the shorter front section could be deployed as a steering aid.

My understanding is that shorter lengths of JSD do not behave in a standard way - beyond a certain point it’s not a case of linear decrease in drag as you drastically reduce cones and length.

But it’s worth experimenting with - please go ahead and test your system let us know. Or have you already tested your system? If it works, I certainly could replace one of my bends with a soft shackle.

Which section? Our tail as 75 cones, the first has 57 and the leader 24. I’m not sure the leader would provide any appreciable and consistent drag.

[thinwater]

Originally Posted by fxykty

My understanding is that shorter lengths of JSD do not behave ... {in the same way as full length JSDs}.

^^ Very true (amended slightly, only for clarification).

I have tested this, thinking a JSD for steering would be cool, but it doesn't really work very well.

• The droop of the JSD is vital to its operation. It keeps the cones below the surface. A shortened drogue runs on the surface, often skipping. The number of cones engaged varies with surfing, making control erratic.
• At higher speeds the cones are not stable. That is why drogues are no longer made using cones.
• They are too close together to be efficient. The spacing works at 2 knots, but at 4-6 knot turbulence makes them unstable and inefficient.

Not sayin' it isn't better than nothing, but it won't be nearly as good as a commercial speed limiting drogue, like a Shark, Seabrake, or Galerider. In my tests, it performed about the same as a string of fenders and anchors. More importantly, a shortened JSD should NEVER be used as a substitute for a speed limiting drogue. It will misbehave dangerously at high load.

This is really counter intuitive until you work through the logic and try it. It seems like such a good idea. It seems like it would be very stable. But it is not. The JSD was a brilliant invention, but it depends on the correct number of cones and a enough tail weight. Reduce either, and you have a completely different animal. Note that Jordan never suggested multi-function use, and he was asked about this.


Or as Fxykty suggested, try it. This is true of any storm device; test it in calm and then near gale conditions. Reach your own conclusions.

[Boatguy30]

Overall, I agree there needs to be at least a nylon bridle to absorb loads. Also if polyester that absorbs water and sinks needs that much weight, you need far more.

I think you really need to calculate the difference in buoyancy and work off of that. By the time you're pulling this out you're obviously really missed the weather window and my we'll need that sea anchor, shortly

[fxykty]

Originally Posted by Boatguy30

Overall, I agree there needs to be at least a nylon bridle to absorb loads. Also if polyester that absorbs water and sinks needs that much weight, you need far more.



I think you really need to calculate the difference in buoyancy and work off of that. By the time you're pulling this out you're obviously really missed the weather window and my we'll need that sea anchor, shortly

According to the designer and various user accounts of storm use the JSD rode itself should not absorb energy only to later release the drag load. The designer specified heavy polyester lines due to less stretch than the nylon equivalents. He had nothing against Dyneema, but at that time it was relatively exotic and certainly not in common use by cruisers.

It’s the catenary of the JSD that provides load absorption and the weight at the end that allows the load to dissipate without acting on the boat. Most of the accounts using either conventional double braid polyester and others using Dyneema describe the ride to the JSD as being very gentle, without shocks. There’s nothing there to suggest that the use of Dyneema would cause shocks.

A stretchy rode or even just bridles could lead to the boat accelerating into the trough as the rode stretches, then pulling the cones out of the water as the boat slows and the cones are accelerated towards the boat. Then the spring expends itself, the boat yaws, and trouble with the following wave.

[Breaking Waves]

Originally Posted by Snore

Dyneema has almost zero stretch and could shock load the attachment points.

As someone who has actually used a dyneema jsd 'in anger' . . . . I can tell you that there is no significant shock loading.
The drogue is not fixed to the bottom - when higher loads come on the cones drag thru the water faster. There is no sudden snatch load because there is nothing fixed to snatch against. It is a quite 'smooth' action.


Dyneema does not tolerate chafe at all.

hmmm . . . . dyneema is one of the most chafe resistant fibers. The filements themselves are more cut resistant than polyester or nylon . . . . and the lack of stretch means that the filiments are not sawing back and forth on hardware, further reducing chafing. In fact dyneema is specifically recommended for leading storm mooring pennants out over the edge of boats and it is proven to greatly reduce chafe risk.

..............

[Breaking Waves]

Originally Posted by StoneCrab

Any comments on ..... Susie Goodall's Series Drogue Failure?

pretty simple . . . . don't use knots. Just stupid bad practice, which the manufacturer already knew and had already stopped doing. They just did not recall or notify prior customers.

She would (most likely) have been ok without that knot, even with a bit of actual displacement underestimating.

Overall, these are safety devices, to be used in the worst imaginable conditions. They need to be built correctly, with decent safety factors.

Morgan's cloud's analysis does not take account of the bridle geometry, which is a significant error - it changes the load analysis - but it does not change the conclusions that knots are dumb.

[Breaking Waves]

Originally Posted by Tillsbury

Re: hauling a jsd back in.

Drag device retrieval is simply hard work - there is just no way around that. Even a single element drogue is hard work to get back in. It used to take us 2 hours to get ours in from the southern ocean (we did use 600' rides down there) - do some winching, take a rest and do a bit more.

We burned out an electric winch on Dashews boat when we tested series drogue retrieval - using the winch continuously (300'). It overheated. You either need to wait until the boat speed drops way way down, or just do it in like a 25% duty cycle to let the winch cool off. BTW - this was a dyneema rode jsd and yes it did winch in, you just needed more wraps. The cones even ran around the winch drum pretty smoothly.

These devices work wonders in storms and you just have to accept that in return you are going to have to put some effort into recovering them.

[fxykty]

I’m wondering whether an electric right angle drill with a winch bit would do better - can a drill better handle a continuous duty cycle like that?