Hello, I’m sorry if this is answered fully in another post but I’m struggling to find an answer to this question. My shop is way too cold, I don’t want to wait, so I’m moving forward with my Passagemake build and beginning fillets and glass. I’d estimate the shop is in the low-mid 40s. Working the epoxy has been awful, as everyone says it should be when it’s too cold. However, I spent many frantic hours fussing over the layup and managed to somehow get it looking pretty good dispite my epoxy being the literal consistency of tree sap. The glass plus first layer of epoxy is hardened to the touch and looks clear with very few bubbles and no blisters.
My question is, have I compromised the strength of the final build by curing the structural epoxy in suboptimum temps? Or will it eventually fully cure in a couple weeks when things warm back to the 50’s?
And I guess my question really is, how crucial is good adhesion for this kind of thing? Should I worry about my hull breaking up under use if I kind of half ass stuff like this? This is my first build and first time working with wood, glass or epoxy
Could you build a small tent over your build out of plastic and heat the area with a space heater? I have done this in the past. Also, you can warm your epoxy either premixing by submerging the bottles in a pail of hot water or post mixing in the microwave. Go slowly at first as you don’t want to accelerate the reaction too much
Thanks David, those are good tips and I will definitely be tenting and heating more intentionally moving forward. I am just worried that the frigid epoxy I already forced onto the hull will have poor adhesion to the wood, even though it looks visually okay. Do you think that’s a risk, or is fiberglassing wood kind of a “if it looks okay it is” sort of thing?
I’m not sure how things will progress now that you’ve completed the fillets and epoxy work, but I wanted to share what has worked for me in a very similar environment. I’ve been building in a garage that stays around 40°F and have had good results so far.
I keep my epoxy stored inside the house and only bring it into the garage when I’m ready to mix and apply it. I also built a temporary tent, as mentioned earlier in the thread. I’ve found that heating the tent for approximately 5–6 hours is sufficient for the epoxy to kick off and cure fully within 24 hours. I typically shut the heat off after that initial period.
Everything has cured solidly and appears to be holding up well. If you’re looking to keep moving forward, this approach may be worth considering. When it comes time to fiberglass the boat, I plan to wait for warmer weather, but I’m hoping to have all other construction completed and ready by then.
First, 40’s is definitely too cold for epoxy work. All the manufacturers’ data sheets agree on this. The good news is that even though you had 40’s as the air temperature, the epoxy temperature was warm enough for a cure to start. And because the reaction gives off heat, once it managed to start it seemed to keep itself warm enough to keep going.
But, even at normal temperatures it takes anywhere from 3 days to a month for epoxy to fully cure. Until it is cured, you should not unduly stress the structure or sand it. You can test the cure by pushing the edge of your thumbnail against the surface. If it leaves a mark, your epoxy is definitely still curing and should be left to continue. Once you can’t dent it, you can try sanding it with #220 paper. If you get dry fine dust, it’s cured. If you get gummy balls, you need to keep waiting.
Once the cure completes, the boat should be fine. Until then, I’d follow the advice the other guys gave here and get some gentle heat on that boat to speed up the cure. A full cure in the 50’s could easily take 3 weeks without outside help.
Thanks Laszlo, that answers my question. I think I will mothball this whole thing until the temps come up, and hopefully by then my initial epoxy work will be fully cured.
My understanding is that epoxy will just stop its reaction when it gets cold and will resume when it warms up (but I could be wrong!) So hopefully it will be ok.
I bought a cheap electric blanket that I use to prewarm the area I’ll be working on and then cover the wetted area with plastic and put the blanket back on top. Or I tent with a tarp and a chick warmer light (bulb in a large reflector) inside. I’ve also added heat from below, so if the boat is upside down and you are doing the outside hull, place heat lamps inside the hull. Just be careful you don’t create a fire hazard.