The boat building method, the resins and fiberglass are much more important than the plywood. You can use cheap plywood and still get a good boat with the proper resins, not the other way around.
The two major components used to build a "fiberglass" boat or to build the seams on a stitch and glue boat are:
Fiberglass and Resin
The resin is a thick liquid, of a viscosity similar to paint. Here, the resin containers are fitted with plunger pumps for easy handling and mixing. The tape is a standard 4" woven fiberglass tape used in small boats. The fillers (micro balloons and silica) are mixed with the resin to make putty.
Fiberglassing or laminating means to impregnate the fiberglass fabric with the resin in order to produce a hard, strong finished product. Each applies resin on the fiberglass, with a roller or a brush.
The resin will cure (harden) and the result, seam or panel, will be a strong, hard fiberglass part. That is all!
Epoxy & Fiberglass basics
Let's look step by step at the building of a fiberglass-epoxy seam: coat with resin build putty fillets apply fiberglass and resin.
The first step is to mix the resin. It is very simple, just mix the two parts in a small container. The resin is then applied on the plywood with a brush or roller. (just like painting) We need some putty to fill the corner first. The putty is made very easily from resin mixed with a filler: micro-balloons, wood flour etc. It can be applied with a spatula. Note that all surfaces are pre-coated before the application of putty or fiberglass.
Lay the fiberglass tape on the wet putty.
Wet the fiberglass with the resin. It will become transparent while absorbing the resin.
Use a squeegee to remove the excess resin and eliminate air bubbles.
Apply Pileply to the epoxy and fiberglass and us a roller to really work all the air out and smoothen final texture of the fiberglass.
My supplier for Epoxy in Greece is Fibermax
Another really cool tool for epoxy is this.
A sort video explaining the mixing procedure
