Time between epoxy coats

[digger]

I will be fiberglassing my kayak hull this weekend. This is my second build using the West 105/207 products. My question is to better understand the proper timing between coats. I have read posts that talk about completing everything in one long day. On my first build, I believe I waited 3 to 4 hours between coats. That doesn't add up to a very long day so I'm wondering if I'm allowing enough time.

What is the best test to determine if proceeding with the next coat is appropriate. The predicted weather will be a high of 86 degrees with 80% humidity (Northern California). I plan on starting the first coat at 7:00 in the morning so the temp will be around 60 degrees to start.

My mistake on the first build was being to aggressive with the squeegee after the first coat and taking off too much epoxy.

I appreciate any feedback.

Thanks

[Patricks Dad]

A good test is checking to see if the surface is no longer tacky but you are still able to dent it with a thumbnail. Some people drag a cotton ball across the surface to see if it's still tacky.

I've always done it in one long day. I take nearly 3 hours to put on the first coat. A few hours of rest before the next coat goes on. Four coats in a day. I start early (6AM or so) and end early (the next morning ~2AM).

[Jim Dodd]

Rare that I disagree with Randy ! And Maybe we're not disagreeing but.
After I put the first wet out coat, I let it cure until it is no longer tacky. With your temperatures now, usually over night. The cloth will be set and still be rough enough to hold the next coat. You don't want your cloth to lift or move !
I prefer rolling all my coats.
Apply second coat, and while it is still tacky, apply the third. The tackiness of coat #2 will help keep coat #3 from running. Runs are a pain to scrape, and this method nearly eliminates it.

Depending on the resins you use, some hulls need as many as 6 coats to completely fill the weave. I much prefer to add an extra coat, than to end up sanding into the weave.

Another point, especially when applying your first wet out coat, is to do it when temperatures are FALLING ! This helps greatly in reducing bubbles in the resin ! IF not warm the hull with a hair drier, and as it cools, brush the bubbles with a foam brush.
Sorry if this is too much info !

Good Luck !

Jim

[Patricks Dad]

With West System 105/207 depending on temp, you won't have to wait long before you hit the not tacky state and ready for the 2nd coat. Just a few hours (check for "not tacky" on the end you started with). As for putting on the 3rd coat before the 2nd coat is no longer tacky, I'm good with that. I generally start on one end (the same end I started the first coat) just after it goes non-tacky (the other end is still quite tacky) and go from there.

[Jim Dodd]

I have only worked with the West System once, it does have a much faster cure time than the System Three Clear Coat that I used for years.
The RAKA I use now is more like the West as far as cure times, and coats required to fill the weave.

JIm