Drogue attachment to cleats or chainplates?

[OrangeCrush]

Thanks for all the replies.

I don't intend to get caught out in survival conditions anytime soon, and if I used the drogue at all in the next few years it would probably be to get some rest in lousy weather or in case of steering failure. Then again, I might as well do things right. (sigh)

So, thinking about chainplates... I'm not an engineer and not quite sure how to work all this out, so any guidance you can offer here would be great while I think "out loud".

The production displacement of my boat is 18,500 lbs. No idea what the true displacement is fully loaded, but CG documentation lists the gross displacement as 18 tons. So let's say my boat could theoretically weigh as much as 36,000 lbs, that would mean a design load of a little more than 22,000lbs, and each chainplate should be strong enough to hold 70% of the design load, or 15,400 lbs.

According to Jordan's site: "For a load of 14,000 lbs, a strap ¼ x 2.25 x 18 inches attached with six 3/8 bolts would provide a conservative design." For aesthetic purposes I would rather have narrower but thicker plates if possible. It also seems that I would benefit from a bend in each plate to match the angle of the bridle and prevent fatigue at the edge of the transom.

Here is a chainplate that could fit the bill:
Schaefer Chainplate 3/8" x 1-1/2" x 16". They are 50% thicker than the example Jordan gave, but 3/4" narrower and 2" shorter. I emailed them for the maximum working load. It seems to me that if they say any number above 15,000lbs those would be acceptable. Am I thinking about this the right way?

I guess I could then probably find reliable but affordable metal shop to make something with the same dimensions for a bit cheaper. Any recommendations would be awesome.

[hpeer]

Well you could just go to onlinemetals.com and order the stuff. They sell 316 grade stainless. 3’ cost $25 plus shipping.

https://www.onlinemetals.com/merchan...d=27&top_cat=1

[danielamartindm]

If you are anticipating sailing in conditions that might mean deploying a drogue, chainplates are the way to go. We're talking survival conditions here. A drogue is to slow you down and keep you within the period of following seas. That's not a measure taken to get some rest, like heaving to; it's to prevent surfing down the waves into a trough with high boat speed, breaking deep, and pitchpoling. I commend you for planning for the worst; go with chainplates.

[kmacdonald]

You might want to look at titanium chainplates. They would be smaller than SS to get the same strength.

[hpeer]

From Jordan’s web site

“Drogue Design Load
The design load for each drogue configuration is adjusted for the displacement of the yacht.
The design load is the ultimate, once in a lifetime, peak transient load that would be imposed on the drogue in a “worst case” breaking wave strike. The working load during a severe storm is about 10 % of this value.”

That’s about 3/4” double braid

[OrangeCrush]

Originally Posted by danielamartindm

That's not a measure taken to get some rest, like heaving to...

Fair enough, and I agree that there is no point installing a drogue if it's not going to be up to the task in a worst case scenario.

As for the choice of metal, is there any way to estimate strength based on the dimensions of 316 bar stock (or titanium, silicon bronze, etc.)? I'm looking around online and I don't see any working loads listed in any of the specs.

Any opinions on the utility of a bend in the chainplate to angle it around the transom edge? This seems like it would be helpful to me but most examples I've found online just extend straight out. Can a steel fabricator bend SS bar to a specific & oblique angle (to match my transom edge and bridle design) without significantly reducing strength?

Southern Star, could you perhaps share more about how you went about getting them fabricated and what you specified?

[Boatguy30]

As Evans will attest, Shannons are built "ok" with lots of teak tacked on.

Those merrimam "marinium" cleats are not all that strong. I would think the coamings are strong enough but you need bigger cleats secured with like 4 x 3/8" or 1/2" bolts

[thinwater]

Originally Posted by OrangeCrush

Thanks for all the replies.

I don't intend to get caught out in survival conditions anytime soon, and if I used the drogue at all in the next few years it would probably be to get some rest in lousy weather or in case of steering failure. Then again, I might as well do things right. (sigh)....

If the intention is for moderately bad weather and steering failure, you don't want a JSD and will not use it for that (if you intend to do things right). It won't work. I've done a fair amount of testing of emergency steering, including faking a rudder jammed over, and you need much less drag. Additionally, the bridle must be adjustable, and that means winches to turning blocks.

https://www.practical-sailor.com/iss...r_12221-1.html

(If it's blowing hard, over 30 knots sustained, the secondary rode, shown as 1-20 feet of chain, will gain 50-200 feet of rope. This is for steering in moderate weather. And you can use the engine, of course.)





Additionally, a cut-down JSD for steering has been tested. It does not really work very well and is less stable than single drogues. This is counter intuitive, I know, but true. Basically, a JDS misbehaves when undersized and towed too fast. That is why Jordan was adamant that the number of cones never be reduced.

https://www.practical-sailor.com/iss...g_12246-1.html

Sail Delmarva: Playing with Drogues

The articles were cut down a bunch. But the bottom line is that bad weather/emergency steering and survival conditions are completely different things.

"Faster Cruising for the Coastal Sailor" covers the topic at full length, about 50 pages worth.
http://sail-delmarva.blogspot.com/20...ook-store.html

I jammed a rudder once, and knowing how to rig something saved me a tow; I sailed home, singlehanded, in the direction I wanted to go. It wasn't bad, more of a learning opportunity than an adventure. I've had worse trips when everything was working. This is basic seamanship. Survival conditions, on the other hand, are about keeping the mast pointed up and the water out.

[OrangeCrush]

Thanks, thinwater; that's very informative. I really meant my comments about probably not using it in survival conditions as a counter to those people that are saying, in this thread and elsewhere, that using existing cleats will be "good enough" for most scenarios short of a hurricane. I don't plan on getting caught in a hurricane, but I do want to install the JSD just in case I do find myself in large breaking seas.

But your points are well taken, and I see that the reasons to deploy a Jordan series drogue are a bit narrower than I had envisioned.

[a64pilot]

Originally Posted by kmacdonald

You might want to look at titanium chainplates. They would be smaller than SS to get the same strength.

Yes, but is the strength of the “system” limited by the chainplates usually, or the fiberglass it’s attached to?
I would assume it’s usually the hull, I’d expect that if I applied an irresistibly force to my deck cleats for instance that it would pull a chunk out of the deck?

[transmitterdan]

Yes, the attachment could be the weak link. The chain plates need to be wide enough to "grip" the hull laminate. Too narrow and the plates tend to crush the hull when bolts are tightened. You want the plates to be rigid and not wallow around under load. That's when they tear up the boat. So pay attention to Jordan's design guidelines carefully. There is more at work than just the breaking strength of the steel. It's an engineered system including bolts, backing plates and the hull laminate.

[kmacdonald]

Originally Posted by a64pilot

Yes, but is the strength of the “system” limited by the chainplates usually, or the fiberglass it’s attached to?
I would assume it’s usually the hull, I’d expect that if I applied an irresistibly force to my deck cleats for instance that it would pull a chunk out of the deck?

I agree. The hull will often be the weak link.

Thinwater, almost all accounts of using the JSD were not in survival conditions and all reports were favorable to it's use. Jordan Series Drogue | Drag Device Type | Victor Shane's Drag Device Data Base
There are other reports as well, google them.

[thinwater]

Originally Posted by a64pilot

Yes, but is the strength of the “system” limited by the chainplates usually, or the fiberglass it’s attached to?
I would assume it’s usually the hull, I’d expect that if I applied an irresistibly force to my deck cleats for instance that it would pull a chunk out of the deck?

In the case of cleats, it is simple enough to engineer the backing plate so the the fasteners are the weak link.

In the case of a chain plate, you should be able to make the chain plate stronger than the rope.

So no, there should never be a hole.

[thinwater]

Originally Posted by kmacdonald

I agree. The hull will often be the weak link.

Thinwater, almost all accounts of using the JSD were not in survival conditions and all reports were favorable to it's use. Jordan Series Drogue | Drag Device Type | Victor Shane's Drag Device Data Base
There are other reports as well, google them.

Absolutely. It will do a great job of slowing you down in lesser conditions. A great invention.

It is not for emergency steering unless the only direction you want to go is very slowly nearly down wind. That is simply physics, not opinion. Try it.

As for gale conditions, for just slowing down, it is probably overkill. Second, you are much more likely to actually use a drogue such as a Seabrake or Gale Rider, because they are much, much easier to recover. I've done this dozens and dozens of times in testing, so I am sure of that.

The JSD is a great invention and I am not taking anything away from that. Don called it "an air bag for sailors," and he was not far off. But few tools are for all situations.

----

The most important thing with all of these is to go out in 20 knots, and then 30 knots, and play with it. Every boat is different and you will learn more about the rigging and use each time. Like reefing, when you need to, it must be routine, with no surprises.

NEVER take an untested weapon into battle.

[b_rodwell]

I am thinking about getting a Jordan Series Drogue for my Lagoon 400. It seems sensible to first think about how it will be attached to the boat before getting the drogue. Has anyone sorted out the attachment on a Lagoon 400?

I have seen some additional chain plates attached to the back of a catamaran on the inboard side of the hulls. They look awful and it is not the strongest part of the hull. The best place to attach a chain plate appears to me to be where the hull/deck join is. It is a lot thicker here. This is exactly where the aft outside supplied mooring cleats are. The Lagoon cleats are substantial and have backing but probably they are not strong enough for a worst case JSD situation.

Any thoughts on where and how to attach chainplates in this situation? Or have you relied on the supplied cleats?

Brian