Newbie Epoxy Question

Hi All,

I'm getting ready to coat the hull of my Skerry and I'm a bit uncertain about the temp requirments for the epoxy.  I'm working in an unheated garage where the temp is pushing 70 during the day, but falling into the 40s at night.  Using the slow hardener, if I apply the epoxy during the day when things are nice and warm, will I eventually get a proper cure with the temp rising and falling over the course of several days? Or does the temp need to remain above 60 continuously for the entire cure time?

Thanks,

Chris


7 replies:

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RE: Newbie Epoxy Question

Chrix,

You'll be fine doing what you said (applying during the warm part of the day, then waiting for the epoxy to cure), What you need is for the epoxy to be warm enough to start the curing process which will then continue on its own. It will slow down when you hit the 40's, but pick up again as the temperatures warm up again. The cure time will be longer than if it was constantly in the 70's, but it will eventually cure.

Have fun,

Laszlo 

RE: Newbie Epoxy Question

Chris,

Sorry about fat-fingering your name. Unfortunately there's no edit capability on this forum.

Laszlo

 

RE: Newbie Epoxy Question

   Laszlo,

Thanks!  I'm glad to know this will work. Also, I think I actually prefer "Chrix"!

RE: Newbie Epoxy Question

   Maybe a few more factoids are worth mentioning, since you've self-identified as a 'newbie'...

Given your low overnight temps, some pitfalls are 1) that epoxy remains viscous until it begins to cure, and 2) that applying the epoxy late in the day is functionally equivalent to applying it the next morning (it's in 'pause' mode all night), and thus under rising-temperature condintions.

So unlike paint, that skins over quickly and is protected from sagging while it cures, epoxy cures (or doesn't cure) equally from surface to substrate across its thickness -there's no early film. It's easy to walk away from a perfectly decent application, only to return hours later to a saggy mess. If you're used to paint, epoxy can be different this way- apply thin coats, or make sure the cure is happening fast enough that there isn't much time for the sagging.

Rising temperatures are especially a problem when coating raw wood- the air in the wood expands as the wood gets warmer, and tries to escape through the fresh epoxy coating, causing pin holes and little bubbles. It's best to arrange your coating schedule to coat while the wood is warm, and with enough warmth left in the day to achieve a decent portion of the cure. After the wood is sealed, if you haven't sanded through the coating, this stops being an issue.

It's also worth mentioning that uncured epoxy and cold temps will make the un-blushiest epoxy blush. This is easily remedied by washing the oily (it's not oil, just feels that way) film off with water and a scotchbrite, followed by a wipe down with a clean rag and denatured alcohol (primarily to make the water evaporate more quickly).

I built half of my first sailboat outdoors, and made many mistakes in adapting epoxy to my schedule, but it all came out fine in the end- there's a solution for every mistake!

 

RE: Newbie Epoxy Question

Hi Chris,

I have been glassing a peeler skiff in my garage this winter in Connecticut, with the temps in the garage going from a high of 60 down to 42 or so.  I used Medium hardner and it worked great.  The low temps allowed for long pot times but the epoxy was hard within 24 hours.  You might want to consider buying the medium hardner (no extra resin required) if you will be applying when the temperature go down in your work space.

 

Scott

RE: Newbie Epoxy Question

   Thanks for all the tips, everyone.  If all else fails I'll move the boat back into the house for the coating.  It's not easy getting it in here, but... doable!

RE: Newbie Epoxy Question

   The temperature range your specified will be fine. The most important step is to properly porportion your resin and harder. I measure by weight vs volume. 

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