Attaching My Jordan series drogue Chaninplates??

[NevisDog]

Originally Posted by YPSILANTI

... I see two options, one being below the inner cleat onto which my aft crossing mooring lines are attached. However, this wasn't suggested by anyone, perhaps for good reason. ...

Sorry if I was not clear, but that is the position I was speaking of - below those deck cleats with aft (crossing inboard) mooring lines attached. Needs careful inspection of structure and appropriate reinforcing (as with any other position you choose).

I don't see how any part of the outboard hull is feasible, given the long overhang of the scoops?

A more complex mounting plate may be appropriate for inboard hull mounting - perhaps with heavy welded attachment point for bridle shackles fixed forward of the aftmost plate-to-hull attachment bolts, if you see what I mean.

[YPSILANTI]

Some feedback: Thanks Nevisdog for your recent reply and to all the respondents. You were all most helpful and stimulated much needed thought for the project. I contacted the manufacturer who also had valuable input and I met with the contractor who will do the installation. We will locate it on the outside just aft of the of the running back stay chain plate. Its the strongest option by far. We will layer an additional 6 layers of quad biaxial glass on the inside and will mount an enlarged backing plate as large as the limited space will allow. On the exterior, the plate will extend beyond the sugar scoop and will be angled to match the bridle angle and will also be beefed up. I'm happy that the attachment will be super strong and that I can hang my cat from it. However, I wont try that just yet. Thanks again for the valued input. Regards Mike

[blueazimuth]

The downwind speeds of a cat will be at least double that of an equivalent monohull, in the same conditions.
Double the speed does not mean double the load: double the speed means the load will be SQUARED.

You'll get lots of good ideas from this forum but IMHO you will be best served by contacting both the designer and builder - they are the folks who know the boat. And make sure they know that the sugar scoops have been extended.
They will not only advise you on the attachment point(s) they should also be able to advise on drogue size. Too small a drogue won't get the job done - too large risks damaging your rudders.
You have a beautiful boat: this is a safety issue - do it right.

[NevisDog]

Originally Posted by YPSILANTI

... We will locate it on the outside just aft of the of the running back stay chain plate. ...On the exterior, the plate will extend beyond the sugar scoop and will be angled to match the bridle angle ...

Glad you found a good solution. For those who have shown interest/concern, can you give a little more detail?
1. How far beyond the sugar scoop will the attachment plate extend?
2. I can picture the plate being angled inboard to match the bridle angle inwards from the fore-and-aft direction (a relatively fixed angle) but I can't quite see how the downward angle of this extended plate can be matched to the pull of the bridle; can you explain? (I'm assuming this angle can vary from horizontal to near 45 degrees below horizontal, as your stern lifts to a very large following sea, so I'm wondering how the bridle will clear the extended sugarscoop while this downward angle constantly changes. The cyclical, vertical twisting loads on the bolts from the extended leverage beyond the last bolt hole on the sugarscoop will increase linearly with the leverage: a few mm will be small, a few inches will be large, a few feet will be utterly horrendous.)

[NevisDog]

Originally Posted by blueazimuth

... this is a safety issue - do it right.

Well, nothing's simple with attaching a JSD, especially with a sugarscoop. Before attaching mine to the (wait for it!) TOERAIL, I reviewed every imaginable other option, and then some.

I read on another forum about someone asking whether he should attach to the toerail on his Swan 41: all advice was negative - 'not strong enough', 'I attach to cockpit winches', 'I use my stern cleats', etc, etc... none of which seem satisfactory on most boats. My toerail happens to be massively oversize for a 33' sailboat, is through-bolted, and is (as with most monos) attached to the strongest part of the hull (definitely no coring i.w.o. deck-to-hull joint).

But how to attach it? There are no shackles long enough to go through the last slot in the rail, and drilling a hole closer to the end would be much weaker than using the full length of extrusion from that last slot. Another option would be bolting a s/s chainplate to the outside of the rail but this raises some corrosion issues with the alloy rail. I looked at one other person's solution, which was to weld an alloy plate with shackle hole raised above the existing toerail - too much leverage there for my liking. (Best advice seems to be - if you can't raise the boat on those two attachment points then they are not strong enough.) So, in case anyone else has this toerail option dilemma, here is a photo of 'the final solution' -

Just a short length of permanently-attached heavy rope each side equal to the length of the sugarscoop, chafe protected (and will be protected from UV damage while not in use). No shackle large enough, so directly attaching thimble to slot in toerail seemed next best option. The JSD bridle then shackles to a hard eye in the end of this short, chafe-protected rope, just clear of the end of the scoop.

I've tried to understand the reason why the bridle ropes should be exactly 2.5 times the width of the transom but I can't think of a good reason to worry about shortening it by the length of these short ropes: have I missed something important here?