Attaching My Jordan series drogue Chaninplates??

[YPSILANTI]

I will soon be attaching my chain plates attachment for my Jordan series drogue. Ideally, I would attached them to exterior of my sugar scoops. However, my sugar scoops have been extended on the outside by 2 feet and I don't trust the joint given that excessive forces that a drogue can potentially exert. I am thus opting to have them mounted on the lower left inner side of the sugar scoop as depicted on the pic. I am also raising the plates to above the first step so that I can construct a slightly longer plate. I plan to have a backing plate on the opposite side of the inside to the hull so my bolts will extend right through the sugar scoop. I appreciate that a wider and lower attachment is fist prize. Is my attachment not a good option, considering my constraints as mentioned above? What comments, suggestions or criticism do any more experienced and informed members have. Thanks so much.

[YPSILANTI]

see accompanying pic.

[mikereed100]

I might be tempted to move them forward a bit and outboard so that the steps provide some support. A bulkhead would be even better. Just curious, do you have access to the inside of the hull in that location so that you can put in backing plates and bolts? It not, another option would be to make composite chainplates out of glass or carbon fiber with epoxy.

[thinwater]

I would have a knowledgeable person take a look. Unlike the traditional locations, near the deck of a monohull, the area you indicated may be quite weak, since it has very low structural demands in ordinary sailing.

Also remember that when mounted inboard, the last bolt takes 100% of the pealing load, rather than wrapping the plate around the edge so that all bolts can share the load in shear. This will also increase the stress on the plate, since peaks stress will be at one bolt, right where it bends. This is not how chain plates are done.

What about 7 inches lower, so they are inline with the swim platform last step? There might be a way to reinforce. But I don't know about access, since in all locations some work will be done from inside.

Too many uncertainties to offer any suggestion. Those scoops make it into a real head scratcher. So many good locations risk chafe.

[Nobody]

By no means am I am an expert but could you not run a chain plate on the inside to the original hull to take the load

[jdaltonpe]

Why not just use the existing cleats? They should be well backed up and it does not appear they will produce a chafe point.

[S/V Alchemy]

Originally Posted by mikereed100

I might be tempted to move them forward a bit and outboard so that the steps provide some support. A bulkhead would be even better. Just curious, do you have access to the inside of the hull in that location so that you can put in backing plates and bolts? It not, another option would be to make composite chainplates out of glass or carbon fiber with epoxy.

This is good advice. I would also ask the manufacturer about their layup schedule for the glass in that part of the hulls. They may have some information that either confirms or rejects your choices.

I also have considered this problem, and I wonder if a strap shaped like the letter "Y" would spread the load better. I would be tempted to go all out on this with stepped thicknesses of biaxial cloth glassed into the hull to spread the loads and with "drill and fill" to isolate any core material fully before putting on a backing plate that matches the chain plate intended for the JSD. It's an interesting and worthy project; considering its intended purpose, you want to do it better than adequately as it will also certainly, at least at particular points in the drogue's cycling, be the most stressed part of your boat.

[YPSILANTI]

I initially wanted to use the existing cleats but there was an opinion expressed on a previous thread that the cleats will not be as strong as dedicated backing plates. I do want to ensure that these are super strong for that once in a lifetime disaster storm that I might get caught in. Another option might be to mount them below the cleats on the outside, in line with the bottom chain plate that one can see which supports my running backstays, in other words, below the cleats just above and parallel the blue painted line? Any comments?

[Don C L]

Just curious, are you planning on running two drogues or one? Ok, I'm no engineer and I have not sailed a big cat, but structurally, is there a reason why it is better to run the bridle off chainplates on the the hulls instead of off the aft crossmember or deck?

[thinwater]

Originally Posted by YPSILANTI

I initially wanted to use the existing cleats but there was an opinion expressed on a previous thread that the cleats will not be as strong as dedicated backing plates. I do want to ensure that these are super strong for that once in a lifetime disaster storm that I might get caught in. Another option might be to mount them below the cleats on the outside, in line with the bottom chain plate that one can see which supports my running backstays, in other words, below the cleats just above and parallel the blue painted line? Any comments?

The problem is chafe. The JSD rode will cut through waves and will remain basically on the true horizontal to downwards about 5 degrees. This is true of any drogue. The boat may be considerably bow-down when a steep wave picks up the back. So the question is, with a 25 degree down angle on the boat and a 5 degree down angle on the drogue, does the rode rub on anything? hard to tell. Additionally, when the wind goes a little lighter, the down angle on the rode will be much greater, since the drogue will run deep.

Watch some videos and ponder.

[thinwater]

Have you ever pulled a drogue? I suggest going out in a good wind (over 20 knots with waves) and deploying it while motoring hard down wind. Put it on the cleats and play with it. Good education anyway. If you don't have the JSD yet, borrow a Delta Drogue or something similar.

[Cadence]

Just as a guess, I think you may be over thinking it.

[NevisDog]

Originally Posted by thinwater

... the area you indicated may be quite weak, ...
Also remember that when mounted inboard, the last bolt takes 100% of the pealing load, ...
This will also increase the stress on the plate, since peaks stress will be at one bolt, right where it bends...
Too many uncertainties to offer any suggestion. Those scoops make it into a real head scratcher. ...

Excellent advice. This may answer Don's question also (mounted on a crossbeam, the attachment is in pure tension rather than shear, so would require massive internal back-up, like any deck-mounted chainplate).

I would be very afraid to mount chainplate anywhere on those long sugarscoops, and that brings in chafe as the biggest headache. The only location that looks any way suitable is close to (i.e. below) those aft deck cleats, but remembering what Thinwater says about the last bolt being subjected to a massive 'peeling' load (since you cannot mount anywhere on the outside of the hulls).

Too many uncertainties, this was never designed to run a drogue - get a trusted surveyor (who understands drogues) to take a look maybe? No, you are not over-thinking it.

[Cadence]

That cross member is probably your best bet.

[YPSILANTI]

I really appreciate the informed comments and that my dilemma is clearly understood. I need to do this absolutely correctly. Considering the valid comments, I will abandoned my original suggestion of mounting on the light blue line as drawn on the pic. The cross member option worries me a bit due to the forces at 90 degrees to the beam, given that one would mount them as close to the outer edge for increased strength. My tender will also get in the way. Deploying would be more difficult too. I only have access to the inside of the mounting point into my engine room to the end stair upright where my logo pic is mounted. Given the valid opinions expressed, 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. Again, this could interfere with my tender, which I will check out. I do have access inside the chain plate there. The other option, which I prefer, is directly below the outer cleat, above the blue painted line and aft of the existing running backstay chain plate. Given that the cleat and backstay is mounted in that vicinity, it should be a stronger location. Id assumed, possibly incorrectly so, that extending my bolts right through to another plate on the outside, right through the top of the stairs wall, is stronger than reinforcing inside and placing the plate on the inner side of the hull in the engine room. It seems I might be incorrect. I value the opinion of the many experts on this forum far more than any other source. However, the suggestions to contact my manufacturer as well as my rigging guys is a good one which I will do. Any comments regarding these latest suggestions will be much appreciated. Again, thanks so much for the very informed opinions. This forum is amazing. Mike