Jordan series drogue attachement point

[Minerva]

One of the jobs I have to do this winter is make the attachment points for the Jordan Series drogue I’ve bought of a fellow forumite.

I’ve read the internets on the matter and general advice is to affix chain plates on the topsides overlapping the transom.

Looking at my particular setup; if i were to add these chain plates I’d have to remove quite a lot of internal fittings in the aft cabin and they’d end up pretty unsightly where I spend a decent chunk of time.

However I have stout cleats with 4 bolts and a clear run aft. See photo

If I were to replace the existing backing pads with a more stout stainless plate spreading the loads, it feels as if that would be a more elegant solution.

What am I overlooking?

 

[veshengro]

On my Nicholson 32 I rigged a Bridle to which the Series Drogue was attached with a swivel. 3 strand 24mm Nylon rope which was made fast to the two after mooring cleats port and starb'd. I had a commercial crane hoist swivel seized midway so that with the Bridle rigged the Drogue line ran from directly astern, not off the quarter.
A couple of reasons why I rigged it that way, one of which was I had a Hydrovane steering Gear and I thought if the boat yawed badly the Bridle would help to keep the Drogue line clear or at least put less pressure on the Vane gear. With the bridle made fast I also left enough end each side to back up on the cockpit winches if things got really bad.

I have to say that in reasonable conditions about force 4, deploying and recovering the Drogue was fairly easy. I let one end of the Bridle go and just hauled the gear aboard with the other end. On deployment after a bit of jiggling with Bridle adjustment length the Drogue settled down nicely and made a very noticeable difference to both speed and movement. This was only me doing test and adjust as it were at the first opportunity that I had once clear of the land.

I was happy and confident that my system would work if required...BUT..I never had occasion to use it, as ironically when life got difficult one dark night it was the Hydrovane almost falling off that caused my problems, the Nic 32 behaved wonderfully well on that occasion thankfully.
Even in mild conditions the strain on the cleats will be significant, so I agree if you can beef up the cleat under deck pads, then do so and leave enough tail end to back up to a winch or other strong point and I'm sure all will be fine.

 

[dgadee]

I put heavy 12mm U bolts on stern with a lot of plywood, ss, epoxy inside. Never used in anger.

 

[srm]

Reading Jordan's original design notes he recommended chain plates and ruled out using cleats or winches for a very specific reason. Running off in storm conditions only the forward part of the drogue will be holding the boat straight and allow it to run with wind and waves. Most of the drogue will be hanging down wards with the tail weight and provide little drag. In the event of a breaking wave strike the boat will accelerate forwards with the breaking wave crest, pulling the full length of the drogue straight. This will cause a large shock load as all the small drogues fill and stop the boat, effectively dragging it back through the breaking crest. His concern was that the shock load plus leverage on cleat or winch fastenings could cause serious damage.

As to the aesthetics of the stern cabin, perhaps neat trims over the reinforcement and fastenings of chainplates could solve your cosmetic problem and be more reassuring should you ever deploy the drogue in anger. You presumably think the drogue is a safety aid for your boat so why accept a potentially weak link that could negate its effectiveness at the critical shock load moment.

In my one serious storm experience (in 50 years of yacht ownership) the first breaking wave strike was followed by three more and the acceleration shifted everything to the aft of all the lockers. This was before I had a JSD so we did not have the shock load of deceleration but surfed dragging warps. It was in a catamaran and both rudders were sheared off in line with the keels.

 

[fredrussell]

Just out of interest, why are JSD mounting points seemingly never attached to the toe rails? That’s a very strong part of the boat I would have thought.

 

[dgadee]

It was in a catamaran and both rudders were sheared off in line with the keels.

How did that happen? Can't picture the forces slicing rudders off in line.

 

[srm]

A series of breaking wave strikes one after the other, third strike filled cockpit, fourth had us surfing sideways with a ton or more of water in the aft cockpit. Have never trusted unsupported spade rudders since as we lost all directional stability.

 

[srm]

Just out of interest, why are JSD mounting points seemingly never attached to the toe rails? That’s a very strong part of the boat I would have thought.

Its a long time since they were published but you can probably still find Jordan's original design notes on the internet. Worth going to the source if seriously interested.
Your question gave me a mental image of an alloy toe rail being pulled off popping its bolts one after the other from the stern foreward. It would be a serious problem if those bolts also hold the deck and hull mouldings together. Of course this could just be my over vivid imagination having experienced breaking wave strikes in a smallish sailing catamaran and a few winter storms in the North Sea from survey vessels.

 

[zoidberg]

Just out of interest, why are JSD mounting points seemingly never attached to the toe rails? That’s a very strong part of the boat I would have thought.

The Jordan Series Drogue is intended as a 'last ditch' survival device and, like a pilot's parachute, it MUST work when needed. There have been several failures traceable to cobbled-together and inadequate DIY approximations, so a 'belt and braces' approach to materials and fitting is justified.

Don Jordan, an aerospace engineer, was concerned to develop and demonstrate a 'proof of concept' which was validated in 1980 by the US Coastguard.... and by hundreds of users since. Without an R&D budget, he used the materials readily available to him, and affordable, at the time. It was for others to take his idea and improve it by use of e.g. stronger, lighter rope and better fabric cones.

His validated calculations indicate that a Maximum Wave Strike could impart 70% of the boat's LADEN weight into/through the JSD's fittings. Specifically, through the fastenings - and into the hull local to the fastenings used. He suggested 2 strips of stainless steel, held by several bolts, would likely be sufficient..... and left it at that.

But what dimensions of s/s strip? And how many bolts? In a line or staggered? It swiftly becomes rather complex 'engineering practice', and many peeps just do a 'That Looks About Right' eyeball assessment. That's their privilege, of course, but I asked a highly-experienced consulting structural engineer who sails. Among other points, he emphasised that few give any thought to the strength of the hull moulding around where the bolts go through and the fittings are attached. Certainly, it wasn't designed for such a load.

'That Looks About Right' is blind guesswork.

In the absence of any data on the details of the hull layup locally, and its age, he recommended adding reinforcing material to the INSIDE which in itself is strong enough for the task of carrying the MaxWaveStrike load and spreading it adequately into the rest of the hull. He suggested multiple layers of carbon biaxial weave, saturated with sticky thickened e'resin, stuck on 'like large sticking plasters'.

Hefty lengths of s'steel with multiple through-bolts can do the job on the outside - but how many bolts? And with what spacing? Washers? Pre-load? What about 'tear-out'? The stress analysis task is daunting, I can't afford the computer time for 'finite element analysis', so am relying on a competent pro engineer's judgement of "that'll do nicely".

I'm not using s'steel strips, but instead I'm using a pair of Harken titanium (!) padeyes - which I happen to have. Harken tell me these, with their bolts, are plenty strong enough, capable of 'well more than 20,000lbf' in shear. Each. Their current-stock stainless padeyes are similarly well up to the job.

There are multiple sources of sound guidance about JSDs, their specification and use, just as there are sources of 'duff gen' and bull****.
IMHO the best guide is Angus at OceanBrake, in Portland, Dorset. He knows....

 

[dgadee]

Yes, my epoxy layup ties in the stern ply/ss with the side of the hull. It looks more robust than just bolting to the hull. But who knows.

 

[IanCC]

..... it was the Hydrovane almost falling off that caused my problems.

Gosh. Could you just talk me through that please.

 

[veshengro]

Hello Ian. Not wishing t o bore everyone to tears, it's in a post by Snowgoose in Scuttlebutt dated 12 july '24 . Sorry I'm not sure how to do a proper reference for you, but if you dig around in old Scuttlebutt posts under " What made you think about giving up sailing"
An old thread and spookily post number 13 !!!

 

[Fr J Hackett]

Effectively whatever you use to attach the drogue should be able to support the weight of the boat and that goes past the actual fitting to how it's fitted. It's all very well to have an immensely strong fitting that when put under enormous load will simply pull out and leave a large hole in the back of the boat. Either do it properly or don't waste the time and money. The backing plates are critical and need to be large.

 

[IanCC]

Hello Ian. Not wishing t o bore everyone to tears, it's in a post by Snowgoose in Scuttlebutt dated 12 july '24 . Sorry I'm not sure how to do a proper reference for you, but if you dig around in old Scuttlebutt posts under " What made you think about giving up sailing"
An old thread and spookily post number 13 !!!

Thanks.

 

[zoidberg]

Effectively whatever you use to attach the drogue should be able to support the weight of the boat and that goes past the actual fitting to how it's fitted. It's all very well to have an immensely strong fitting that when put under enormous load will simply pull out and leave a large hole in the back of the boat. Either do it properly or don't waste the time and money. The backing plates are critical and need to be large.

"The backing plates are critical and need to be large."

And very strong.

That's a much more succint way of saying what I was banging on about.

 

[noelex]

Effectively whatever you use to attach the drogue should be able to support the weight of the boat and that goes past the actual fitting to how it's fitted. It's all very well to have an immensely strong fitting that when put under enormous load will simply pull out and leave a large hole in the back of the boat. Either do it properly or don't waste the time and money. The backing plates are critical and need to be large.

+1.

This is a good article on the JSD:

https://cruisingclub.org/sites/default/files/article_files/JORDAN SERIES DROGUE Best Practices 2.0.pdf

We have a JSD but have never used it in anger. My understanding is that the normal load is high, but peak loads can be exceptionally high. Attachment points that will hold (in sheer) close to the value of the displacement of the vessel are recommended.

Unfortunately, the cleat in post #1 does not look adequate in my view even with a strong backing plate.

 

[noelex]

I would install a thick aluminium or stainless steel plate under the cleat but on top of the deck leading aft. This would terminate in the drogue attachment point.

This plate would leave room for several extra bolts through the deck. Underneath this deck plate would be a backing plate.

 

[zoidberg]

....peak loads can be exceptionally high. Attachment points that will hold (in sheer) close to the value of the displacement of the vessel are recommended.

Yup!

 

[zoidberg]

Wee boats are MUCH more vulnerable to being overwhelmed by jetting, breaking seas than bigger boats. The real need for a good, sound JSD is very much higher in a wee boat.

Guys like 'noelex' and his bonny lass, and Skip Novak, in much larger, heavier boats are far, far, less vulnerable.

Do remember that Don Jordan set out to invent a solution to the killer circumstances exposed by the '79 Fastnet disaster. That happened close to our home waters. It could very easily happen here again.

'Do not send to ask for whom the bell tolls. It tolls for thee.'

 

[geem]

Just out of interest, why are JSD mounting points seemingly never attached to the toe rails? That’s a very strong part of the boat I would have thought.

They sometimes are. I have s/s sandwich plates to bolt to my toerail. 150 M8 bolts each side should be enough