Epoxy question

I’ve just started my first stitch and glue kayak and have run into my first challenge. Perhaps an experienced builder can offer an obvious solution I’m overlooking. I’m building the boat in my unheated, uninsulated garage, and I ordered the medium hardener with my Arctic Tern (System Three) because I figured that I’d be doing most of the epoxy work in May and June, when the daytime temps at least are 50s-70s But right now, its below freezing at night, and only about 40-50 in the daytime. I did two butt joints last night, just to get the hang of it, warmed the epoxy before, etc., but completely neglected to consider the temp. 24 hours later, it hasn’t cured, and at these temps I’m not sure it will.

Should I just give it more time, or start over? And does anyone have any creative solutions for keeping the epoxy warm while it cures? Would placing a box with a light bulb over the joints be an invitation to burning down the house?

I’ve spent a bunch of money since the kit arrived, so I’d prefer a solution that doesn’t cost more money. Do I need to order a small quantity of fast hardener? Invest in a space heater?

light bulb.
it will cure, give it time. and heat. be patient.

all of the above
yes to all the questions, except starting over.

even in the cold the epoxy will set up. it will just take a while. a small heater will work, lightbulbs too. the faster hardener will also help. Ideally, all will make life good again.

I once rebuilt the deck on a 35’ sailboat with epoxy one winter. we had ALL kinds of weather and just dealing with it on a daily basis worked well

good luck


Easy fix
I built my kayak starting in fall and going through the entire winter in a room that had no built-in heat.

I used the same epoxy and hardener you are using and had no difficulty with curing despite frigid nighttime temps.

What I did was to keep two oil-filled portable radiators in the room. They are electric. You can set temps from low to high, and some have thermostats. Best of all, they are inexpensive. Definitely cheaper than wasting epoxy. Available at department stores, home improvement stores, etc.

Best to work in a falling-temperature environment (but not falling too low). You don’t want rising temps while epoxy is going from wet to green-cured, as they tend to cause air bubbles to form in the epoxy.

If you haven’t been studying the posts at www.kayakforum.com, it’d be a good idea to start doing so. Lots of great tips. I wish I’d read it BEFORE starting to build my boat.

It will cure
I used a small hand held hair dryer to help speed up the cure on a small patch.

Patience is a virtue!



Thanks all
for the advice and reassurance. I’ve got a box with a light in it over the two curing joints now, as well as a digital thermometer. I’ll check the inside temp a few times in the next few hours.

for little things lamps can work
for big things you gotta warm up the room and only do glassing/sealing on steady or falling temps. If you crank up the heat with uncured epoxy on plywood you’ll get a billion little bubbles as the wood outgasses.

For doing butt joints I used red bricks on a 4mm piece of ply and put a clothes iron on top of the second one. When it got too hot to touch I’d turn it over on the cold brick and move on to the next joint. At around 100degrees the epoxy will cure in a few hours,at 50degrees it may take a couple days. The same can be done with a 60watt bulb in an aluminum reflector set on the bricks. You don’t want the wood epoxy to get hot,90degrees is plenty for a 12hr full cure with slow epoxy and maybe 6hrs with medium. Guessing there,only you know when you do it.

Don’t worry,slow curing doesn’t mean it’ll never cure,just that at cold temps it’s very slow. Don’t bother trying to wet-out epoxy on the glass when temps are around 50 degrees, the epoxy is thick and it’ll be awkward to squeegee out the excess. If you can get the room/table up to 60 degrees it’ll make a big difference for the amount of wasted epoxy left on the glass/wood. If you glass at 60degrees and the temps fall over night to 50 it’s not guranteed that cranking the heat back up won’t cause outgassing on the existing partially cured epoxy.

As you can see a steady shop temp helps a lot. Better to have a constant 60 than varying between 50-65.

Those tips are useful. I figure these two inside hull butt joints are not a bad place to learn, as even if I screw them up, they wo’t be visible on the final product.

Here is a first
LeeG I agree with you.

The rate of cure of an epoxy will depend on the ambient temperature. A constant temperature is better than temperature variation as that can lead to inconsistent curing rates within the epoxy.