3 strand polyester for a Jordan Series Drogue?

[Neeves]

Daydreamer

A very valid question.

Biscay is one of those locations with a 'reputation' - I wonder how many have deployed drogues there.

Jonathan

 

[RobbieW]

....Thinwater conducted some tests on drogues, he actually used a cross section of devices, his summary is in Practical Sailor - I'll see if I can find the link. I think drogues etc have been topics of discussion in Cruiers Forum a number of times, they have a good search engine...

Heres a single item from CF where thinwater seems to believe different on stretch and JSDs... Acera vs Dyneema & Jordan Series Drogues - Page 5 - Cruisers & Sailing Forums. There are numerous articles on the AAC site about the use and design of JSDs though I couldn't find one that discussed nylon vs dyneema

...Does the Bay of Biscay get that busy- i do not know? I assume one would be well outside & on a line that ships would use.

Given the availability and general accuracy of forecasting today, and that Biscay is about a 3 day crossing, I dont think a JSD is required for crossing. In the open ocean where you need to be able to handle whatever you get its a different matter. Traffic in Bisacy tends to follow very specific routes, off the shelf and in the centre you are unlikely to find much about

 

[Neeves]

I think one of the problems of drogues et al is that few have been used in anger and, I suspect, when you are using one - the last thing on your mind is recording accurate quantitative information. I recall Thinwater suggesting that Morgan's Cloud were monitoring two actual uses, The GGR being one (and I don't recall the other) - last year??

I think anyone considering one needs to read as much as possible and take a balanced view themselves - there are conflicting ideas.

I have never used one, nor do we carry one - as Robbie says - forecast are, usually, adequate and we don't cross oceans

I do think, I hate to say this, there are similarities between the drogue and an anchor rode - both need some ability to absorb energy - which is why I'm not keen on dyneema (unless you 'add' something to manage the energy) which may be the cones themselves or a nylon bridle to hold the drogue

Its a difficult issue to test realistically.

Jonathan

 

[Daydream believer]

Presumably one has to take into account the rudder. With the growth of spade rudders with a large unsupported blade the force on it if the boat is stopped & a huge wave hits it could be catastrophic. The same for a sea anchor off the bow with the boat suddenly lurching backwards.
If there is a lot of elasticity & give in the system one would assume ( & I have absolutely no experience of this) the boat could go forward fairly quickly & ease the pressure on the rudder. Is that what the idea of a drogue is? Apart from allowing the boat too much forward motion allowing it to broach.
If it is, then it must be difficult getting the balance right & a gale is not the best place to experiment.

 

[differentroads]

I asked because one chap I spoke to expected to sail in the southern N sea. The thought of a ship coming ( which would be quite possible in a very busy area) when he had a drogue out had me wondering if he had thought through how long it would.

I wondered too. When fitting out in East Anglia for my own big adventure I had used AIS to identify a 20 by 5 mile stretch off the Suffolk coast which never seemed to clock any ships tracks. I planned to use it to test my drogue and Aries steering, bearing in mind exactly what you said.
2 years later in the Med I still have not got round to it. It's still on my to do list. But from that bit of AIS study I learned the value of studying AIS patterns on my planned routes over a few days to work out where shipping routes will be. Mostly obvious (draw a line between distant TSSs or from them to commercial ports.) This even worked for me crossing Biscay. My route kept me about 10 miles west of a line drawn between Ushant and Finesterre TSSs for most of the trip, easily in VHF radio range if needed. I could also pick the best time to cross to get on route to A Coruna within a 24 hour window. It happened to be during a night of crystal clear visibility.

Good luck Gitane. The trip down here was great for me and I hope it will be for you. Make sure to allow tons of time for the Galician Rias. We had to skip most of the Portugese west coast to make up time dawdling in the Rias (a 48 hour and a 24 hour passage from Vigo to Lisbon to the Algarve) and I'd do the same again. ?

 

[noelex]

The advice I had from oceanbrake was that you wanted some stretch as the loads could be considerable. Also Don Jordan recommended it.

I can see the attraction of HMWPE for weight, size and chafe resistance.

Any references for using HMWPE?

There have been many sailing threads on this subject with responses from people much more knowledgeable than myself. This is just one example:

Acera vs Dyneema & Jordan Series Drogues - Page 4 - Cruisers & Sailing Forums

This is what the Jordan series drogue designer Donald Jordan said about stretch in the line:

“The increased stretch will not reduce the load, in a breaking wave strike. In fact it will increase it a bit. The drogue must pick up the load quickly before the boat broaches and must turn the boat into the wave. The cones near the boat perform this function and the less stretch the better.”

 

[Neeves]

I have not read the provided links but

Has anyone used a dyneema drogue - I would not want to be the first to try one.

One reason offered for the dyneema drogue is that its light - it also floats and I'm not sure a floating drogue is going to work too well. You can, of course add weight, chain is commonly used - but you would need to add chain down the length of the drogue or at intervals along the length - negating the weight savings and making is very difficult to retrieve.

Until all the questions are answered and a few other people have had the courage to try dyneema - I'd prefer to stick to something that has a little bit of user experience.

Why do I suspect that quite a number of people carry them - but they have never been used, even in practice.

Noelex, do you have a drogue, have you used it (in practice) is yours dyneema.

Jonathan

 

[gregcope]

Thanks @nolex interesting thread.

 

[HunterWanderer]

I have used a builders bag as a drogue with four 12mm polyester lines off the stern. It is amazingly effective. Slows the boat down to about 1 kt. and keeps it straight . In a big wind waves crest all around but the turbulence of the bag seems to stop the crests behind you. Provides great respite as the worst blows through.
Recovery is simple. Just put engine in reverse and take in the slack .
I would also recommend taking the main and genoa off before the wind gets up too much . Dont rely on just rolling it up. The wind gets into it and Ive had it shred the sail.
Also have the washboards attached to the boat with cord so that you cant lose them and they need to be pretty water tight.

 

[pandos]

I am making a Jordan Series Drogue for my Westerly Griffon which has a displacement of about 6000 lbs.

Most drogue I have read about use braid on braid polyester rope to hold the cones, but 3 strand polyester rope is cheaper.

Would attaching the cones onto appropriately sized 3 strand polyester be adequate? Is there a reason why 3 stranded rope should not be used?

Hi what material are you using for the cones..have you found a good source for the tapes/ribbon/webbing

FYI I am making one using 16mm double braid. It will be really heavy so much to be said for the dyneema.

I saw a post from Jordan himself where he explains why stretch in the line is bad and also one where a JSD was used which had stretch and the cones nearer the boat were frayed.

 

[Gitane]

Hi what material are you using for the cones..have you found a good source for the tapes/ribbon/webbing

FYI I am making one using 16mm double braid. It will be really heavy so much to be said for the dyneema.

I saw a post from Jordan himself where he explains why stretch in the line is bad and also one where a JSD was used which had stretch and the cones nearer the boat were frayed.

I am using 6oz RipStop kite nylon cloth and 25mm polypropylene webbing rated at 450kg breaking strength. Both of these are for sale on EBay.

I am using 100% polyester thread as its strength will not be affected by water.

 

[Neeves]

I find it slightly bizarre that after decades since the JSD was introduced there are no definitive answers to the simple question - which cordage is recommended.

Saying a cordage with a lot of stretch, presumably nylon, is not recommended leaves a a number of other option. If dyneema was the ideal, effectively no stretch - I'd expect a definitive comment. The absence of definition leaves me puzzled.

The quote in Noelex post No 26 ' the less stretch the better' - implies Dyneema - so why not say so - or does he mean - a little stretch is necessary. Dyneema has been around for over 30 years now - its not as if its new.

There is a suggestion that the first cones take a lot of the load - beefing them up sounds like a good idea.

Jonathan

 

[Roberto]

I find it slightly bizarre that after decades since the JSD was introduced there are no definitive answers to the simple question - which cordage is recommended.

Not sure elasticity is of big concern with JSDs: the whole system is designed to be permanently under tension (contrary to single drogues whose rode could be affected by the relative position on the wave system of drogue and boat).
The differences in boat speed caused by wave dynamics would create an additional load on the line. The working additional elongation would be given by the difference between the constant load and this additional temporary load.
Say 14mm rope breaking load around 4k daN, suppose an additional load given by the wave impacted boat to be 400 daN, this is 10% or rope BS. Probably much higher but as a start.
An increase of 10% BS load gives maybe 2-3% additional elongation in nylon double braid distributed over the whole rode length, on average JSD rodes lengths this would be what, 1-2meters at the boat?
Double/treble the impact force, additional elongation of a few metres?
Rough and inaccurate figures of course, but if the elongation magnitude is of this order, I doubt it is of any concern.

 

[Neeves]

It must be a concern as 'too much stretch' might allow the yacht to broach - apparently. Your figures suggest a 1-2m elongation which seems unlikely to cause a broach - but then, along with most others, I've never used one.

Noting you figures - I remain puzzled.

Jonathan

 

[Wansworth]

Hoping to cross the Bay of Biscay this summer. Weather and my nerve permitting.

Go via La Rochelle.....Gijon........A Couruna

 

[Roberto]

It must be a concern as 'too much stretch' might allow the yacht to broach - apparently. Your figures suggest a 1-2m elongation which seems unlikely to cause a broach - but then, along with most others, I've never used one.

Noting you figures - I remain puzzled.

Jonathan

Mine are really ballpark figures: if the rope is loaded at say 20-30% BS by the constant pull of the line, how much additional % of BS caused by wave dynamics might it be able to tolerate? 10-20-30% more? These figures will give a few metres additional elongation with polyamide. Take polyester and they are nearly halved.
Should the temporary load be +50-60% (meaning reaching a total 80% of BS) I think the rope would break in a very short time.


edit referring to this chart.

 

[GHA]

.....
Double/treble the impact force, additional elongation of a few metres?
Rough and inaccurate figures of course, but if the elongation magnitude is of this order, I doubt it is of any concern.

Could well mean the boat has accelerated a bit further down the face of a breaking wave though, energy proportional to velocity squared so much more force required to slow the boat down when the stretch is gone than with less stretch, chance of the stern getting skewed round by the braking wave? .... One for the engineers

 

[Roberto]

Mine are really ballpark figures:

Thinking it over
In conditions where I might use a drogue, my boat under bare poles would drift at hull speed limit say 7-8kt; this gives a very rough figure for hull resistance of a few hundred daN, difficult to estimate as the resistance curve becomes steep so it might actually be higher.
Take the worst case (for elongation) say only 400daN, 10% of BS. Additional load is triple that, +30% BS.
Polyester rope loaded from 10% BS to 40% BS goes from 2% to 5% elongation, that is 3% difference, meaning just a few additional metres.

 

[RobbieW]

...Has anyone used a dyneema drogue - I would not want to be the first to try one...

They are an option, apparently, from those that make them commercially. The comments on AAC come from real world use of a dyneema JSD

Could well mean the boat has accelerated a bit further down the face of a breaking wave though, energy proportional to velocity squared so much more force required to slow the boat down when the stretch is gone than with less stretch, chance of the stern getting skewed round by the braking wave? .... One for the engineers

Thats consistent with thinwaters comments on CF referenced earlier. iirc you took part in that discussion as your alter ego

 

[HunterWanderer]

The load on the lines is quite high. I would suggest using something like 20,000 N (2,000 daN) because there is some snatching as the waves pass through. Basically the boat is hanging off the drogue when the boat trying to surf down the wave, You're pulling about a ton (10,000 N) through water at about 1 Kt.
If the lines are stretchy then the cones nearest the boat will see the load first which could lead to damage.
If you use a single drogue then stretchy is good as it reduces any shock loadings,
A builders bag is rated at about 25,000 N SWL