Drogue attachment to cleats or chainplates?

[hpeer]

Orange

The info you seek, the basic strength of metals, can be found at online metals.com.

https://www.onlinemetals.com/product....cfm?alloy=316

You can buy just about any size you could possibly want for this application, cheap.

Your backing and bolt pattern and the material you are mounting to all come into play just as much as the actual chain plates.

It strikes my you are over thinking one piece of the “system” while ignoring others.

Frankly, while what you want to do is a great idea, I kind of doubt this is the weakest link in your boat. If you think about all the various ways you can be injured or die in a boat, make a list, put a probability and severity against each one and then put a cost against each one. Then you come up with “bang for the buck” roadmap.

Let me assume you will be sailing as a couple, just for illustration. Things you might want to consider are:
Inflatable life jackets so you wear them always
Helmut’s
Crotch straps for life jackets
PLB sat and/or AIS type
Automatic defibrillator if you’ve a creaky heart
Lifesling
Jacklines
Etc

My guess is that any one of these above items is more likely to save a life than the chain plates. And your list may be way different than mine because our sailing is different. May be wrong, it’s all a crap shoot anyway.

Just something to mull over.

Good luck

[thinwater]

Originally Posted by 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

The problem with inboard is that instead of the bolts being in shear, sharing the load, the last bolt is forced to carry the entire force as a pull-out vector. I would really need to see the engineering to believe it.

Outside, the problem is generally chafe, depending on the sugar scoops. Outside also gives better leverage.

[kmacdonald]

I'm doubt that many people will opt for multiple types of drogues and/or sea anchors. These devices are costly, take up space, and can be heavy. I also doubt that few if any will be used in survival conditions and if they are will only prolong the inevitable. If you are caught out in a hurricane the chances of survival are very slim. Having a JSD system designed for lesser conditions to make it more affordable is far better than not having one at all.

[hpeer]

Or maybe just a Gale Rider, that would be used more frequently.

[a64pilot]

I have an 18’ parachute anchor, that is a large thing that does take up a lot of room.
I also now have a Galerider, by comparison it’s light and takes up very little room. They are both stored in the anchor locker
I see them as different devices, with different uses

[OrangeCrush]

Originally Posted by hpeer

Orange
It strikes my you are over thinking one piece of the “system” while ignoring others.

I think that impression is more a result of how I use this forum rather than how I prepare my boat. I spend a lot of time thinking about the weakest link, as you say, and if there is an unresolved safety issue in my mind it keeps me up at night. This forum is extremely useful when I get to a technical impasse or tough decision, when I really need to figure something out before placing an order or moving to the next stage. I almost put the words "assuming all other safety measures are in place" in my first post but I figured that was going to provoke people even more...

Thanks for the list, though; it's good to have a variety of suggestions. I usually sail with a crew of friends and we're all in our thirties with no heart conditions so far I've got an epirb, liferaft, throwable dan-buoy, lifesling, strobe lights on our inflatable PFDs, more. We practice man overboard drills and we're extremely strict about clipping in to the jacklines at night and in any kind of bad weather. There's always room for improvement, of course, so I appreciate the help. The AIS-PLBs are an interesting idea, for example. Also do you mean helmets? I don't have those...

And thanks for the link. If the yield strength of 316 stainless is 60,000psi, and the cross section of the chainplate I was considering is .65 square inches, that would mean an overall yield strength of about 40,000lbs, making the rode or the shackle pin the weakest part of the system as it should be (again assuming that the backing plate and bolts are done right).

Jack

[hpeer]

Yeah, helmits. You know you need ‘em when your spelling geos.

[thinwater]

Multi-purpose is something of a problem. The problem is speed. Drogues have a speed limit.

A common storm / drogue story goes something like this; "We were bombing a long with the drogue, the storm grew more severe, and suddenly it was thrown forward by a wave, and all was lost." Only they did not understand what they were watching. The drogue was too small and possibly on too little rope of the wrong kind.

A drogue is a little bit like a ground anchor that requires nearly infinite scope to work. Obviously it cannot provide uplift resistance; it is symmetrical, how could it? The chain holds it down, to a point. The rode must be very long to keep the pull low. This is NOT for shock absorption, it is for scope.

By the time the storm is strong, all drogues run just below the surface. When the waves become steep, the steep face acts like short scope, and the drogue pulls out, just like an anchor breaking out. Because the rode was nylon (it should be polyester) it recoils and the drogue appears to have been thrown forward. Maybe the wind catches it. But the wave did not push it.

The lessons. The JSD resists this by having many elements. Only a few are on any wave face at a given time. This can also be accomplished by running 2 drogues in series with at least 100' of rope between them. This works very well, since they stabilize each other and slow the boat farther.

A JSD works better because it slows the boat more. This is why a JSD should NEVER be shortened. First, the cones will be torn apart (they are not designed for more speed). Second, they will become unstable above 4-5 knots, just like any other drogue. Drag drops, instead of increasing. I have tested JSD cones in series at higher speeds and the stink.

The bottom line is that if a drogue is small enough to allow high speeds, it becomes unstable. The Galerider is a little better, because it is a net, but any undersized drogue will come to the surface and pop out of waves.

----

In this video I am pulling 1/3 scale models at 6-7 knots, which is above sable speed for all designs. The rode looks short, but it is anchored at the waterline, so it is low.

There are two drogues in series; a Seabrake replica in front and a Gale Rider replica 50 feet farther back. Instead of the drogues being ripped from the water, they stabilize each other. You can see how the Gale Rider pulls the Sea Brake right back into the wave.

https://www.youtube.com/watch?v=KCR21yh_O9w

[hpeer]

Interesting. Gale rider recommends 350’ of line with 250 - 300 being deployed with NO chain.

I bought an additional 600’ of rode.

Another thought. Elsewhere a gentleman suggested an “Adams drogue” which is a length of rode let out off the quarters and looping back to the boat. Then you use heavy hose to attach drogue elements, on a retractable line. The idea being you can add or remove resistance as necessary. If the assembly threatens to come out of the water you can add weight.

A final thought, I sometimes wonder how a Fortress anchor on a swivel would work.

Final, final thought. Morgan’s Cloud discusses using a gale rider off the bow to assist in being hive to, keeps the bow from losing off.

[OrangeCrush]

Hello all,

I've been making progress on this project and I could use some more of your collective insight on one issue...

I'm having chainplates made and my transom is 5 feet across where the attachment points will be, which according to the Coast Guard/Sailrite plans would dictate a bridle length of 14 feet on each leg (or 12 feet from the transom to the middle of the bridle "triangle").

However, the sides of my hull near the transom angle inwards a bit. If the chainplates extend straight back, overhang by a few inches, and the bridle legs continue in the same direction, then the lines will converge only 7 feet behind the transom. On the other hand, if I make the bridle long enough as per the guidelines, then the forces on it will not be pulling on the chainplates in a straight line, but rather they will want to pull them away from the hull. (See pics) I fear the lateral forces will cause the plates to bend or crack near the after-most bolts. I could have the plates made with an 8 degree outward bend, just after the last bolt, to reduce the lateral leverage, but it would still mean the forces are not quite in line with the orientation of the chainplates.

So what would the consequences be of having a shorter bridle relative to the transom width? Would it cause increased yawing, or maybe too much strain on the bridle-to-drogue connection? I imagine this issue must also come up with canoe-stern installations.

Any insight you can offer is greatly appreciated!

Jack