Drogue Failures

[thinwater]

The loss of Suzie Goodall's boat in the Golden Globe Race due, in part, to drogue failure, has generated a few threads. Some time ago a fella ran a data base (I'll leave the name out) based on real world experiences, but it has become a bit dated.


I'm not going to theorize about Goodall's failure yet. I'm hoping more information will arise, though perhaps it sunk with the boat and Goodall surely had her hands full.



What actual failures do we know of? I've been really brief, and I know that, so don't nit pick. Just add usable info. Some will say they are useless, which they probably are for bigger boats. This is NOT one size fits all.

• Chafe. Probably the most common. Can happen anywhere; attachment points, over the rail, steering gear (numerous cases), thimbles, etc. Easy to under estimate, since we don't get much practice rigging gear under such strain. Seems to be more of a problem with sea anchors and JSDs (more stress).
• JSD cone fraying and failure. During long, extreme storms, or multiple storms, light weight cones can disintegrate. However, the failures are gradual and I don't recall any leading to actual trouble.
• Gale Rider cable ring failure. Several cases. Only a minor effect on performance.
• Sea anchor rode overload. Whether heating or simply overloaded, I think these are sometimes under-speced (they should logically be larger than anchor rodes, but often are not).
• Sea anchor, ride problems. Not all boats can ride to a sea anchor, and sizing/rigging can be tricky.
• Single element drogues snapping forward due to steep waves and nylon rode recoil.
• Too much rode stretch. While required with chutes, it can allow the boat to go backwards. With drogues, it sometimes allowed a little surfing to start. Should JSD and single element rodes by reduced stretch?

Fire away!

[Dockhead]

Good quality cones, a really meticulously checked chafe-free, fair lead, and dyneema cordage, would seem to me to be the elements of success.

[Kenomac]

Did you complete your drogue construction project last summer?

[Dockhead]

Originally Posted by Kenomac

Did you complete your drogue construction project last summer?

Almost. Just a few cones left to attach.

We experienced no bad weather at all despite the fearsome latitudes. Nothing over F6. It was a great trip with a lot of excellent sailing including several 200+ mile days.

[George DuBose]

I would like to hear more about cone failures of Jordan Series drogues. This thread is the first I have heard of that possibility. Were the JSDs self-made or made by professional sailmakers?

...and where would one use Dyneema in the costruction? The bridle? The long "tail"?

[wrwakefield]

Originally Posted by George DuBose

I would like to hear more about cone failures of Jordan Series drogues. This thread is the first I have heard of that possibility. Were the JSDs self-made or made by professional sailmakers?
...

George, John Harries at Attainable Adventure Cruising wrote an detailed article specific to your question- including how the issue was resolved and many references... [The modest membership fee is well worth it to us...]

Other articles in that series address the question of lower streching lines in the JSD.

There are likely other resources answering your question as well.

Cheers! Bill

[oldbilbo]

There are examples reported here and there of drogues parting. The OP is probably right in that 'chafe' is a significant issue. There are reports also of some cones fraying to the point of seeming ineffective - usually close to the bridle - but that the general effect of the assembly remains positive.

I'm just as concerned with the MATERIALS from which many assemblies are constructed. It is reported in the publications of several marine rope makers that 3-strand rope tends to unlay under repeated cyclic loads, therefore multiplait or braided constructions are recommended.

It is also indicated that nylon, when wet, not only is significantly weaker than when dry, but that it loses Ultimate Load Strength rapidly when subjected to cyclic 'stretching' stresses - 'rapidly' when compared with e.g. braided polyester/wet.

....polyester has a much greater fatigue life than nylon, perhaps 100-1000 times greater.....

Consider the chart....




Rope manufacturers and riggers alike counsel us to utilise end-loops and splices of appropriate minimum bend radius and to be very wary of inappropriate knots; otherwise, significant portions of the rated Ultimate Load Strength is lost.

Don Jordan's notes, and others, suggest that drogue-rodes be spec'd to cope with something of the order of 80% ~ 60% of displacement ( the 'design load' ), and the bridle legs some 70% of that. But what about the knots and fastenings which secure one section to the next? Many drogue-rodes are multipart - and of different construction and diameters....





Could there be rather more to this than chafe...? Could there be a cumulative effect of, say, 20% loss due to being wet nylon plus 20% loss due to poor choice of joining knots ( bend radius ) plus 20% loss due to cyclic load weakening....

If not, why not?

[JPA Cate]

Our friend, Suzanne Curphey-Huber, part of the Longue Route sail, has reported that many of her JSD cones have frayed on their leading edges, and (by private communication) said she was going to devote some time to re-sewing them.

Ann

[Ambler]

Originally Posted by JPA Cate

Our friend, Suzanne Curphey-Huber, part of the Longue Route sail, has reported that many of her JSD cones have frayed on their leading edges, and (by private communication) said she was going to devote some time to re-sewing them.

Ann

I borrowed Snow Petrel's drogue for a Trans Tasman and inspected the cones as he said he had deployed it a few times. The leading cones were rather frayed so Kathy and I decided to build our own and we beefed up the cones by adding a seam on both leading and trailing edges of each cone. We bought a length of 18mm super yacht genoa sheet rope with dyneema core for the first 60% of the drogue length then finished it off with a 16mm double braid tail since the first half of the drogue appears to do all the work. I think the yawing and snatching loads must be huge so I followed the model of attaching chain plates to each side of the transom. I shackle 2 yellow lifting strops to each and then join them together with a huge bow shackle to the drogue.
I haven't had to use it now that I have it ready to deploy anytime but I sure could have used it on my first Tasman Storm 12 years ago.

I do know Susanne has used hers a number of times, 3 GGR boats have come to grief on the same wx systems where she has deployed her JSD. I met her a few years back and we keep in touch.

Although the chainplates are a bit ugly I admire the seamanship they represent in allowing the deployment of a no chafe drogue system.

Welcome back to Tassie by the way Jim n Anne. We met years ago in the Tamar.

Wayne

[kmacdonald]

It may also help to to construct the drogue with half the cones on one section of line and half on another section and no cones on the leader. The sections with cones can then be changed so the trailing cone section is moved to the leading cone section. This will distribute the cone wear better. The downside is that both sections will need to be made of the lager diameter line. That won't matter much if dyneema is used.

[Kolchac]

I’m finishing my JSD and need your advice. I’m using dacron cones and do not expect frayed edges.
The biggest question is the drogue rod.
What is really surprised me - in all designs I found they suggest the rod strength should be dependency of a boat displacement (as for anchoring or docking). Instead it should be function of cone size, cones number and boat speed. Also the attach method to double braid rope looks ridiculous to me: they attach cones to the cover, so all stress holds just cover, and if it works, that means no need for such thick rods. Here is the video.

https://www.youtube.com/watch?v=t4l3CbgUCU8

The drogue is 100 cones. If boat speed with drogue is 10 kts, the resistance would be about 3,800 lbs.
So I’m looking for a right rope. What about Samson or Dyneema? How to attach cones to ones?
Thanks

[samfreeland]

I'm thinking of using a good size road cone with a bridle attached to the base on a swivel. They look indestructible. That left hand lay rope with wire in each strand they use on fishing trawler nets is bullet proof :-)

[Dockhead]

Originally Posted by oldbilbo

There are examples reported here and there of drogues parting. The OP is probably right in that 'chafe' is a significant issue. There are reports also of some cones fraying to the point of seeming ineffective - usually close to the bridle - but that the general effect of the assembly remains positive.

I'm just as concerned with the MATERIALS from which many assemblies are constructed. It is reported in the publications of several marine rope makers that 3-strand rope tends to unlay under repeated cyclic loads, therefore multiplait or braided constructions are recommended.

It is also indicated that nylon, when wet, not only is significantly weaker than when dry, but that it loses Ultimate Load Strength rapidly when subjected to cyclic 'stretching' stresses - 'rapidly' when compared with e.g. braided polyester/wet.


Consider the chart....




Rope manufacturers and riggers alike counsel us to utilise end-loops and splices of appropriate minimum bend radius and to be very wary of inappropriate knots; otherwise, significant portions of the rated Ultimate Load Strength is lost.

Don Jordan's notes, and others, suggest that drogue-rodes be spec'd to cope with something of the order of 80% ~ 60% of displacement ( the 'design load' ), and the bridle legs some 70% of that. But what about the knots and fastenings which secure one section to the next? Many drogue-rodes are multipart - and of different construction and diameters....





Could there be rather more to this than chafe...? Could there be a cumulative effect of, say, 20% loss due to being wet nylon plus 20% loss due to poor choice of joining knots ( bend radius ) plus 20% loss due to cyclic load weakening....

If not, why not?

What you've written here pretty much outlines the case of why I would never, ever use nylon for a drogue.


There are many reported cases of the old fashioned parachute drogues failing because the nylon rode failed, discussed in Dashew's old "The Right Rode" article.


Nylon would be singularly ill suited, in my opinion. Dyneema is not even that expensive, considering the fact that you can downsize it. It also has tremendous advantages in weight, like 1/3 the weight for like strength, making it much more feasible to handle in storm conditions, then on top of that, much easier to splice. For me, Dyneema all the way (actually I used Acera Amundsen, another UHMWP rope).

[thinwater]

I invite readers to make up a pair of splices as shown above and pull test. They will fail either at the base of the splice or in the body of the splice (I have done this). The reason is that each leg carries only 50% of the load. If you check the strength loss around a bend tables from the rope makers, you will find that the loss is 50% when D=d. The eye splice is a very different case than a rope over a pulley.


There is no error in connection method.


Nylon vs. polyester vs. Dyneema is an interesting question. However, Dyneema could not be used on GG boats.

[Adelie]

What are G-G boats?