Drogue Chainplates / Attachments

[Tim Good]

As a follow on from this thread: http://www.ybw.com/forums/showthread.php?413504-Pardey-Bridle-Sea-Anchor-Method-Opinions


I thought I would begin a discussion on attachment methods and strengths for using a Jordan Series Drouge. In doing so I thought I would use my own boat which does not have drogue chain-plates and the possible options i have as a starter.

Boat: SeaStream43
Disp: 15t
Hull: Semi Full

From my reading I should make any fittings capable of taking the weight of the boat in the worst case breaking wave scenario. So in this case I should be trying look at approx 8T on each fitting with a bridle distributing the load at 30 degrees or less. So I look at what others have done:

Now lets take my example and maybe some can advise. Look at my transom below. You'll see in the red circles are two very heavy duty anchor rollers made from 3mm stainless. they extend aft and overhand by about 150mm. I have figured that a bridle from these would not touch any other gear. Ignore my kedge and outboard ... Directly foreword of them are two large cleats.

I was thinking of some system whereby I install a large block of ply and a stainless plate inside the hull as a backing plate to reinforce the existing roller. I would then use a chain attached directly to the stainless rollers and then backed up to the cleats tightly, should there be any give at a critical moment. They would be fitted tightly so any give at all would take onto the cleat.

In this instance what problems do you envisage? Is it strong enough? Any other points of discussion / best practice advice.

 

[Deleted member 36384]

I would favour an eyelet for attaching a shackle to, rather than running through a fairlead or cheek plate where chafe may be an issue. I would also be inclined to have them bolted through the quarter instead of on the gunwale. Some gunwales will be hiding a deck/hull join and I would not want to apply stress to that joint. My thoughts, hope this helps.

 

[oldvarnish]

I'm a Jordan owner.

If you read erstarzinger's posts ion the previous thread, he suggests (based of wide experience) that for the drogue to be loaded to the full weight of the boat would only happen in conditions so extreme that they come under the heading of 'once in a lifetime'.

Chafe is far more likely to be an issue, and those cheek plates seem to me to be as sharp a chafing point as you could get.

You could, of course wrap something round the warps, but that wouldn't be easy once the load was on.

If it were my boat, I'd put some massive closed fairleads on the stern and some well backed-up cleats forward of them.

 

[oldbilbo]

If it were my boat, I'd put some massive closed fairleads on the stern and some well backed-up cleats forward of them.

That sounds like sound sense.

Don't forget - as many do - the facilty to use 'dogs' to spread the loads across/around the boat.

 

[Seajet]

Of the chainplates shown earlier on other boats, the in-line ones look like they have a good chance, the one athwartships on the transom doesn't !

I don't fancy using the gunwhales either, much rather the closed fairlead* and a massively backed cleat in front of it.

* In a perfect world, how about those closed fairleads with an opening bridge on top like the RNLI use ? Keeps a few more options open..

 

[Tim Good]

the facilty to use 'dogs' to spread the loads across/around the boat.

Can you elaborate on that please?

 

[estarzinger]

Chafe is far more likely to be an issue

I generally agree with your comments, but note: If you use a Dacron bridle it will be much less chafe prone than nylon (because it will be stretching back and forth much less), and the strain is steadier. So chafe on drogue rodes/bridles tends to be much less of a problem in "the real works" than in nylon anchor/Para-anchor rodes. Chafe may be the number 1 failure mode of para anchors but I rarely hear about it in drogue reports.

 

[Fascadale]

Always nice to see a photo of my boat on Scuttlebutt, even if its a tiny part of it.

Having set up the drogue's chainplates and constructed the drogue itself the problem still remained as to how it was to be deployed, if required.

We decided that the bridle should be permanently in place. Shackling it on in a big sea was very unappealing. I see that the bridle on Morgan's Cloud seems permanently fixed. We ended up tying the bridle round the vane with wool.

As you will see from the photos the after deck of a small boat is a congested place: I thought the biggest problem would be how the drogue would be deployed cleanly to be certain it would not foul or snag on anything, or go out the "wrong" way.

The third photo shows how we "stored" the bridle when it was not attached to the rest of the drogue

And this is before we even start discussing retrieval.

[

 

[oldbilbo]

Can you elaborate on that please?

OK. Consider, first, the original use.

An anchor cable, massively thick, is brought aboard through a forward fairlead and the considerable load is secured into the bitts. Several lighter lines - or 'dog stoppers' - are 'clapped' onto this loaded anchor cable using rolling hitches, half-hitches and seizings, or similar. The inboard ends are secured to cleats, to ringbolts, or other strongpoints in the decks. Once loaded up, they spread the load into the vessel, reducing the likelihood of the bitts ( foredeck cleat ) being torn out of the vessel.

Now:

Much the same effect can be achieved in a modern yacht, by seizing/bending several lines onto a loaded anchor cable ( chain or warp ) and taking those lines aft to cleats or to primary cockpit winches, where they are loaded up. That takes some of the load off the foredeck samson post/bitts - or even the windlass - spreading load among other parts of the vessel. Cheap and easy....

Do sort out something similar if/when under tow. It saves expensive damage....