I believe it's all epoxy.
My understanding is that you can use epoxy resin with polyester parts, but not polyester resin with epoxy parts. I could be wrong about that, but my friend, who's a fiberglass guru, told me to use an epoxy based system, so I did. I've used the West Systems epoxy resin for all my fiberglass work so far. If you get the slow hardener (but not the super slow), it has a great working time.
Polyester resin layups over epoxy is a no no. Adhesion is poor. However, polyester fillers will adhere just fine to fully cured epoxy layups.
+1
Polyester resin layups over epoxy is a no no. Adhesion is poor. However, polyester fillers will adhere just fine to fully cured epoxy layups.
Larry
Apparently . ...Alchemy?
..Alchemy?
Apparently . .
West testing.
West: "Because of the difference in curing chemistry, it is not possible to achieve a chemical bond between epoxy and polyester gelcoat."
They go on to say the adhesion is mechanical. The final conclusion is that the bonding is fine for gelcoat (I assume not as a structural bond).
Pretty much covers polyester fillers too.
Not sure I understand your meaning by that.
If I remember correctly, polyesters chemical bonding window never closes, which is why polyesters resins can be so successfully applied over cured polyester; In this case, it is not rely upon it's poor mechanical adhesion, but forming a strong chemical bond. As West mentions, polyester cannot even chemically bond with epoxy, even if the epoxies window was open, due to different chhemistries.
Larry
This relates to epoxies ability to bond to polyester which isn't really relevant to polyesters ability to bond with epoxy. The cured epoxy or gel coat on the OP's cowl has reached a full cured state and therefore cannot chemically bond with anything (epoxies can only chemically bond prior to reaching a full cured state). Epoxy is known to have a much stronger mechanical bond than polyester resin. Epoxy is much more flexible in what it will form a relatively strong mechanical bond with. This is one of it's main advantages. Polyester is not as flexible in this regard and doesn't grip very strong, mechanically, as epoxy even in its most favorable environment.
If I remember correctly, polyesters chemical bonding window never closes, which is why polyesters resins can be so successfully applied over cured polyester; In this case, it is not rely upon it's poor mechanical adhesion, but forming a strong chemical bond. As West mentions, polyester cannot even chemically bond with epoxy, even if the epoxies window was open, due to different chhemistries.
Larry