We've done quite a lot of carbon chain plates.
Its a snap .....infact easier than metal fittings.
Im not going to try and guess the engineering but the process is as follows:
a heavy plywood web is glassed into the hull aligned to the eventual direction the shroud will lie in .
A small tab of the wood extends above the finished level of the deck.
When you know where it will be, use filled epoxy to glue in place a stainless tube large enough to take the bolt or pin that will have to pass through it [was that too obvious? LOL].
If you need the tube to be say 30mm long then make it atleast 40 mm.
50mm might be better.
Before the glue holding has set lay unidirectional carbon over the top, down the plywood web and onto the hull skins.
We try and spread the carbon over a large an area as practical so there is a bigger bonding surface.
Peel ply can help a lot to hold the fibre down and give a clean surface later on.
Next day use a hacksaw to trim to size.
When the deck goes on you just cut a hole for the chainplate to project.
Because Im a cynic I'd double the taping used for the hull to deck join about 300 either side of the ply web and extend that taping all the way around the web too.
Now you have an intensely strong structure that ties hull, deck and chainplate.
Then fair as normal.
PS. Theres no real reason to use carbon.
Quality glass fibre has similar enough tensile strength that carbon is strictly for bragging rights.
In my 8.8m catamaran I did without chainplates.
Instead I made a "chain area".
This is how I did it:
1. Carefully wet out a bundle of carbon uni fibre with epoxy.
2. Make a loop at the halway point of the bundle.
3. Offer the loop through a hole in the hull side.
4. Insert a nylon thimble in the loop.
5. Pull the ends from the inside of the hull to press the thimble against the hole.
Remember to align the thimble according to the stay angle!!!
6. Fan out the fibers and roll them carefully against the inside of the hull using an aluminium roller.
Better still - use vacuum bagging.
7. A heater lamp will be a great help in post curing the area.
I used 80x40 cm of carbon fibre for each.
The laminate does not have to be as thick as for regular chain plates, but better be safe than sorry.
(Still I can't imagine how strong the laminate would have to be to withstand the tremendous point loads from the bolts in regular chain plates!)
This arrangement could also save both weight and money:
Instead of heavy and expensive bottle screws, I use lashings between the ends of the stays and the nylon thimbles.
When I fit the mast in spring, I start with an almost fully unscrewed forestay bottle screw.
I then lash the stays, align the mast and tighten up.
At last I tighten the forestay bottle screw, and the whole thing takes shape with pre bend and everything.
Two or three persons does this without problems.
I should add that this setup is based on an idea from the web site multihullboatbuilder.com.
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