When I glass on wood birch fins, The RR epoxy seems to not cure all the way, kinda gummy. Did research and thought the problem was that I wasn’t using additive F. So, the next time using Additive F, I am having the same problem, just not as bad.
check, double check, triple check your mix ratio. If you go by volume, it has to be very close to 2:1.
What is the temperature like? If it is cold, epoxy can take quite a while to kick. Zapping your resin in the microwave (just part A, the 2 parts volume) to get it bathtub warm will also help you get a faster kick and lessens the bubbles. Additive F will make it easier to sand and helps thin the resin.
When I glass on wood fins the fins have already been glassed by the person that made the fins. The wood is sealed. Did you glass the fins first or try to glass on a RAW wood fin?
I agree with c-slug. Microwave your resin only 2 seconds per ounce in an appropriated container. then take out of the microwave, add hardener and stir add additive f and stir and do your thing.