Hello and welcome usrnm, It sounds like your a boat builder any interesting projects going on in you area.
I am not a professional boatbuilder. I have a wooden boat that I have restored together with a professional, hence the experience. Though I have been using epoxy in a lot of other woodworking and non woodworking projects.
Outside of the obvious, that is gluing, I have, for example, replaced silicone caulking in bathrooms with industrial elastic epoxy. The elastic epoxy won't stain or collect mold ever, whereas silicone is pretty prone for that. The only downside is that it is a real pita to apply and you have to get it from a specialist vendor and have a custom color made for you. I have also used epoxy with very fine grain silicate filler instead of a traditional grout in fine (1 mm) grout lines. It hones nicely down to a completely smooth and lippage free surface when setting floors with natural stone. Laticrete has a wide range of epoxy grouts and I have used Laticrete products as well, though they are quite expensive compared to industrial vendors.
There are a few things in addition to epoxy being toxic that you should be aware of. The chemical reaction that cures epoxy is heat generating. Even a fairly small batch can cure out of control if left into a narrow and tall pot. The thicker or larger the epoxy mass is, the more heat is generated. Just 100g of mixed epoxy can reach 200C or 400F when curing out of control. With some fillers, the heat can lead to spontaneous combustion. Uncontrolled curing generates, in addition to dangerous heat, a lot of toxic vapors.
It is always better to mix a too small a batch instead of a larger one. It is always better to have a shallow and wide container for the mixed epoxy. Also, when filling cavities with epoxy, it is better to do it in multiple thinner layers rather than in one thick patch of epoxy.
There are water soluble epoxies as well, though I would avoid these. The size of the water soluble epoxy molecules is such that they penetrate skin if (and when) they get in contact with your skin. The traditional epoxies have different molecular size and do not penetrate the skin the same way - so I have been told by an industrial vendor.
As epoxy cures chemically, you do not have to wait for a full cure between the coats. Not waiting for a full cure gives a better bond between the layers. If you let the epoxy cure fully, you should sand before applying a new layer for better bonding.
Epoxy is a lot of fun to work with, but I advise reading the safety instructions from the vendor before digging in. All stains should be removed before the epoxy cures. Xylene, acetone or even white spirits work. Xylene is my favourite, but more toxic and flammamble. Always wear protection when handling Xylene and remember that it melts most plastics if it is in contact with them for too long.
