Yup, Brian is right.. A lot of epoxy will "activate" (get pretty hard)
down to the high 30's (F), but will never really finish off until it
gets a good 24 hours at above 70-75 degrees F. Because epoxy is itself
overkill for most of what we do with it, for practical purposes, we can
call it "cured" even before that heat period and final cure, the
overkill is also what makes it possible for almost anyone to build a
boat.
To the origional poster, build a small tent, in a garage or something
if you can, and put a couple of incadecent light bulbs in there
overnight, you will probably be pleaseantly surprised. Don't go
overboard, 75F is plenty and in this case, higher temps are not
necessarily "better". Be cautious of fire hazard of course. I crank up
a 65,000BTU furnace in the 12 x 20 shed, more overkill, try the light
bulbs
Good luck.