You're using MAS 2:1 epoxy, right?

If you stick with the slow hardener exclusively, be aware they don't recommend temps much below 60°F for proper curing. Moving to medium or fast hardener removes this caveat.

Try to keep your components in your conditioned living space, or make arrangements to get them conditioned to at or near 70-75°F prior to mixing and application. This makes it much easier to ensure proper mixing and application as the mixed components will be their most fluid.

Be aware too that if your workspace and project components are warming up after the mixed resin's been applied you may see outgassing of trapped air and water vapor, leading to bubbles. So if you can schedule your sessions to begin once the space and your project are as warm as you expect them to get this can be avoided.

Cold materials, when subjected to a rapid rise in temperature for the workspace, may invite condensation onto your project's parts before they become acclimatized to ambient temp.

Keeping your space no cooler than 55° with slow hardener ought to be a big help in keeping your project's assembly advancing.

   Thanks, yeah I'm using the 2:1 epoxy that came with the class kit.  I generally work in the evening so it will only cool off over night.  I'll have to check garage temps, one end of the boat under the second floor and the other end is by the garage door which I assume is much cooler.

Would a space heater to warm the boat up before applying be a good idea?  It's flipped right now so I think if I ran it under the boat it would trap the heat and warm the boat fairly well.  I think it's around 55-60 in there right now.

Space heater - the kind with metal filaments that turn red when you turn it on - more likely overkill for boatbuilding needs. Lots of wasted energy going off into the air, not so much into warming your project. There’s also some fire risk with those, particularly in a garage, on the floor, where dust & fumes settle.

More efficient might be a 100 watt incandescent light bulb with one of those bell-shaped aluminum reflectors around it so the big, open end is above the gunwales while your hull’s bottoms-up. Add a second fixture similarly equipped if you have a mind to get really ambitious, cover a lot of surface area in one session.

Some fire risk if you drop a fixture whiie it’s lit up but overall a more cost-effective localized heat approach.

If your garage door’s anything like mine you’re probably right thinking that end’s gonna be the cooler one. Sometimes it’s worthwhile simply hanging a sheet of plastic ceiling-to-floor between your work area and doors like those. The barrier cuts down air circulation. Trick here is hanging that sheet so you can stow it easily between sessions and still get the door up as necessary.

I built my Shearwater over last winter in Seattle in an attached garage.  I ran a space heater (the electric oil-filled kind that looks like a radiator) 24/7, and was able to keep the temp in the mid 60s all winter.  I never had a single issue with epoxy curing nor outgassing.

Mr Herbert I think you made a good choice given your climate. The radiator-like oil-filled heaters are a safer alternative to the often similarly-priced, open-element kind.

Out of curiosity did you bother with evaluating how running that heater 24/7 affected your electric bill? Those heaters are pretty efficient but where I am winter temps can hit - 20°F in winter. Winds commonly 20+ mph only make it worse trying to moderate temps in even well-insulated ground-level structures.

I have a 1500W oil-filled in my basement for times like those when I work down there. Rarely drops to 50° though. Running it @ 65° for 12 hrs adds ~ $3 to my electric bill.

   Awesome tips, thanks so much everyone!

I'm not sure what it added to my bill, as that was my first winter heating the house with a new heat pump and I had no baseline.  Overall it was considerably cheaper then the ancient furnace that was in there prior.