JEM Watercraft

When would be the best time to apply a coat of epoxy to "saturate" the boat? Would it be before assembly or after assembly? Or should I apply the fiberglass without a previous base coat of epoxy?

Paint,

I'm surprised there are no answers to your question! Here's my experience.

AFTER you have constructed the boat, you have set it square and it is all in line, the seams are all epoxied, the wires are removed, THEN you can do a saturation coat. It is best if you do it in a time when the temperature of the surrounding air will be decreasing. As the wood cools, it will help to suck epoxy into the wood. Probably, you want to do the outside of the boat first.

Another parameter is, that you should start your glassing within 2-3 days. This has your fill coat for the glass chemically bonding to the saturation coat. Lightly sand the dried (set, really) saturation coat before you try to apply glass over it. A smoother surface is easier to work with.

So, after construction, saturate outside of the boat. In 2-3 days, lightly sand and glass the outside. Saturate the inside 2-3 days before you start to glass that. Inside can trail the outside a couple of days, or more. But time between the saturation coat and application of glass should be within that 2-3 day time window.

If you miss the time window of 2-3 days, rough sand the saturation coat so the new epoxy will have something to get a grip on. It's call "tooth" in the boat building circle. (One of those odd terms you have to be able to say to be cool around here. Snapping fingers jauntily here, spitting in the dirt, squinting knowingly.)

I didn't see this one.

I'd say after you rounded off the seams ad are within 24 hours of applying the fiberglass.

If something unforseen happens between the saturation coat and getting the fiberglass on, take heart!
You can wipe off any blush from the saturation coat with an acetone soaked rag.
This will keep the subsequent coat(s) of epoxy from "fish-eying" or beading up.

Lee

Thanks guys that helped clear things up. I just want to be very prepared way before I get to any step in the building process.

Hey Paint,
A word of "hey I did this, so you don't have to"............ The "saturation coat" DOESN'T have to be a 1/4" thick! I used WAY TOO MUCH epoxy on my first build, and most of it was not realizing how much was "enough".

My next build will involve using only a bondo spreader or squeegee to spread the epoxy on the boat. The saturation coat is mainly a seal to keep air bubbles from forming in your subsequent coats of epoxy.
Lee