I do a lot of bondo/fiberglass work of late, and though I'm a newbie at it I made a discovery that might help someone.
Whenever I
fiberglass, I put in the MEK and depending on the temperature, it could take 36 hours to 36 minutes to set up. Just before it gets useless and thick it'll heat up, then too late.
Whenever I bondo, I put in the MEK paste and it usually sets up while I'm delicately artfully spackling it on, even if it's a bit cold outside.
So I found that if I add some
fiberglass resin to the bondo and then the MEK paste, not the drops, it stays silky smooth and lasts longer before hardening than just bondo. Anyone who frosts cakes will appreciate this consistency. It's nicer for spackling. And if you want
fiberglass that sets up fast even in cold weather, just do the bondo-resin mix with mostly resin and use the paste, not the drops...for some reason this will definitely set up even when you "shouldn't" be fiberglassing due to cold.
Also if you want a really flat outcome just put a piece of overhead projector plastic film over your bondo, flatten out bubbles with a flat stick and leave it until set, don't remove it early. It will just pull right off and leave a mirror-flat finish.
I am going to be replacing my
windows with flat glass/aluminum frame
windows and so I'll have to build out my curved fiberglass for this purpose, and this is going to take some patient creativity. I don't see the point of replacing the plexiglass only to re-crack/get all scratched up/leak again. Apparently these are leak-prone
windows over time, and with aluminum windows set on rim built outside the main plane of the shell, this should avert that, or that's the plan.