: In "The New Kayak Shop" it says "Apply fiberglass
: tape to the fillets while they are still wet; if the fillets are
: allowed to harden, they must be sanded smooth prior to applying
: the tape." My question is, why do you have to sand them?
: Epoxy will adhere to epoxy in either case, won't it? If your
: fillets are fairly smooth to begin with, then why would sanding
: them help? Why can't you just wet them with a little epoxy then
: lay the tape over that?
: I'm not being lazy, it just seems like there's less chance of me
: messing up my nice clean fillets by letting them harden when
: they are perfect, and then doing the tape later.

This is how it was explained to me.
The first procedure is known as "wet on wet". The resultant bond is chemical. If the fillets are hard the bond will be mechanical and a roughenened surface is needed for the fresh resin to get a grip.
The "wet on wet" technique can save a lot of time, too, and is worth considering.