In addition to repairing & replacing the glass that was already there, plus that that got damaged, you're going to need to heavily beef up the laminate in that area in general.
I'd say, by adding at least 10mm - 12mm of epoxy/glass laminate, in a pad FAR larger than the davit's footprint themselves. Like at least by a factor of 4, if not far, far, bigger than that. Using proper laminating practices, & tapering the reinforcing pad to be thinner & thinner, out toward it's edges.
In addition, you can glass in some stiffening ribs as well, up to & including some glassed in framing, to tie in the loadings from the davit's new reinforcement pad, into some of the boat's primary structure... like connecting the
hull sides to the
deck in that area.
And to also possibly include stiffeners glassed into/inside of the new (glass/epoxy) reinforcing pad, in the way of cores. Be they; high density foam, balsa,
plywood, G10, or
aluminum.
The reason for so much of the extra reinforcement being glass, is that it then becomes integral to the structure of the vessel. And everything is working together to help to support your loads. So you get a lot more bang for your buck, than by just adding a backing plate.
Once you've added more primary structure to that area of the vessel, THEN, look at adding under deck backing plates.
Aluminum or G10 might be easiest & best (you can make the latter yourself). As they're machineable without special tools. And both can be easily bonded with
epoxy, right to your boat's laminate (although some fasteners too, wouldn't hurt).
Some of my stressing the points of both; bonding things to the boat's structure, & adding more laminate thickness is 2-fold.
- You're thus adding strength, in the monocoque sense, to the
hull & deck. Where as when just adding backing plates, they only act to spread a load.
- You're adding integral stiffness. And stiffness increaseas with the cube of thickness. Which greatly reduces flexing.
Adding stiffness is key in an application like this, where you have a load which inherently wants to flex things, cyclically. Because cyclical flexing weakens structures over time, in exactly the same manner as bending a piece of wire back & forth.
Hope that that helps, & isn't a case of TMI, or preaching to the choir. And some of my simplifying things, & laying them out in a bit of detail, is for the new guys. Who may not have been exposed to this kind of thing before.
PS: Also make sure to taper the edges of any backing plates, regardless of what material they are. So as to reduce stress concentrations at their edges.
- That, & I forgot to state that adding supportive/stiffening plates to the outside of the deck/area ain't a bad practice either. So as to help balance out the loads (and laminate strength).
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