Those just aren't cracks in the gelcoat
in the second image. In some spots the cracks go all the way through and the overlapping GRP can be removed by simply flicking it with your fingers.
After removing the port lights as well as the thru hulls I can tell you that the layup
is definitely not 1/2 thick. More like 1/4 or 3/8 . This would also explain the flexing on the deck
(not cored) - especially on the port side parallel to the head
I'm still mulling over ideas for the deck
joint repair. The one that appears to be winning is applying epoxy
to the entire length of the joint. As you've mentioned, the top portion overlaps the hull
which required the "step" in the rail you speak of. I hadn't considered that Conyplex would fashion and send me rails on a boat built 44 years ago. I imagine that will cost me a pretty penny. One idea I'm tossing around is to temporarily mount a thin (perhaps 1/8 inch thick) slat of wood horizontally along the entire hull (about 1 inch below the joint) and then apply epoxy
, feathering in the top while building up below the joint to the thickness of the slat. Then, once the slat is removed, this would give me the "step", or a flat surface to mount new rails without having to worry about milling them.
Whatever way I choose to go with, I won't make the mistake the previous owner(s) did by applying caulk/sealant to the bottom edge of the rail. I'm convinced that this is what led to water
getting trapped behind the rail (no where to escape once the water
penetrated from the top of the rail) and caused the damage to the GRP and deck to hull joint.