Steve Firth wrote:

Most GRP is styrene,


Polyster.

Nit picking - styrene monomer which polymerises to polyester. Plenty of
free styrene left over.


No, that's not true. Polyester resin doesn't adhere as well as epoxy to
cured polyester. Epoxy will always provide a good bond, *provided* that
you clean away the moul release agents from the surface. Roughen and
swab with acetone before attempting a repair.

Hmm, gotta say that has not been my experience, but I've only dabbled,
so I'm prepared to take your word for it.


--
Grunff