Reinforcing Deck Penetration For Shroud Eye

[RunAgroundHard]

Masthead rig, single spreader, shrouds, lower forward and aft stays, inner forestay, additional aft shrouds for inner forestay, 10mm stainless wire rigging.

My lower forward shroud eye is an integral forged eyelet, shoulder, 1” threaded part that passes through the deck. Under the deck is the associated nut and 3mm thick washer about 2” OD. The deck at the penetration consists of the deck shelf mounded from the hull, with the deck and coach roof moulding sitting on the shelf. It’s around 1 1/2” thick. The deck is bonded to the shelf with an Epiphanes epoxy.

There is a bulge on the deck, some spider cracks in the gel coat and an associated depression on the underside of the coach roof, good access. There is no core here, just GRP layup.

I am planning on fitting a plate under the deck to butt against the side of the hull, about 200mm long, 100mm wide and 5mm thick. It will be drilled to take the threaded part of the eyelet, obviously, and epoxy used to create a fair surface and bond between the plate and deck.

My initial plan is to use stainless, but there is also G10 Epoxy Glass Laminate

Compressive strength G10 450 MPa
Yield strength A4 Stainless cold worked about 450 MPa. (YS is a reasonable comparison for CS in this case)

The stainless option could be bought as a channel section, the G10 can be easily shaped to conform to the hull.

If going for G10, do you think I should go to 10mm thick, shape and bond to the underside from hull conforming to the hull curve, also easy to add webs onto the hull. Or just go for a section of stainless U as big as I can fit, 100x50x5mm channel section by 200mm long.

 

[William_H]

I take it that this shroud is in centre of deck (inner forestay) and that you feel the GRP is bending upward and not stifff enough for the loads. You could reinforce with more grp however it is the thickness dimension that gives stiffness. So the SS U channel would be best but at the loss of some headroom under the 50mm of channel.
A Grp slab of 10mm would be much more inclined to bend.
You might consider carbon fibre layed up on bench or in place. If you can increase the thickness with foam or wood you could get more strength. Certainly carbon if you want the lowest profile.
Another approach even more intrusive would be to attach a wire and turnscrew to the fitting and take it down to hull to a plate bonded to hull.
I can not tell just how much extra strength you need if any. That will be up to you to decide what will mke you happy. ol'will

 

[Ceirwan]

Not super clear from your description of a shelf.
But I'm guessing you have something like this?



Like Will said, the U-Channel will certainly work if its sized correctly.
But I'm always suspicous of shrouds just bolted to a wide expanse of deck.
The solution above with a tie bar to the hull is tried & tested.

Alternatively, you could glass in a knee or webb to support the deck.
12mm plywood, two layers of 600gsm biaxial on each side of it. (with epoxy). bedded into the hull with thickened epoxy smoothed to make a nice fillet.

And finally 3 layers of tabbing also in 600gsm ought to more than do it.
You could shape it like the 2nd image to make it look nicer.