Since you are working in the garage, you can heat a realtively small area rather simply. When you finish yor gluing for the day, drape the boat with a plastic tarp or drop cloth. Underneath it, and at least 2 feet from the boat or the tarp, you can set out a few ordinary light bulbs. Wire us a string of sockets and use 100 watts or smaller bulbs. Stretch a line of them along the length of the boat if you wish. 300 to 500 watts of light bulbs put out enough heat to warm things under that "tent" by 10 to 15 degrees. You'll get some radiant heat actually warming the wood, and you'll get some warm air rising off the bulbs and circulating by convection. This doesn't work as well when you have a lot of drafts. And don't get the bulbs too close.

A lamp timer should handle 300 watts rather easily, so you can set the bulbs to go off after 3 or 4 hours, saving on electricity. You can also set this to turn on the bulbs a few hours before you plan to work on the boat.

Hope this helps

PGJ