GRP lay-ups vary wildly from make to make and generally speaking,
older offshore boats have thicker hulls utilising low tech materials, many
of which I suspect will outlive more modern lighter build, high tech ones.

I was interested to see the wreck of a Joint Services Victoria 34 (Ensis) in
Cherbourg last year. I own one of the Halcyon 27s that were replaced by the
Victorias in 1990.

I was amazed how thick our Halcyon's hull is when I had to cut into it once.
The topsides are half an inch thick and it gets progressively thicker as you
go down; when I installed the log I was cutting through well over an inch of
dense GRP.

Ensis on the other hand had a sizeable hole and she wasn't half as think at
any point, the thickness also seemed to be uniform. Much more what I would
have expected actually.

David