Eric,

Do not sand now.  You will cut the fiberglass.  You want to add additional thin coats of epoxy to fill the weave.  Two more should pretty well do it.  More epoxy will only add weight with no strength addition.  Once the weave is filled and you have added all the epoxy, then you can sand.  Again:  ONLY enough epoxy to fill the weave.

Good Luck, Paul G.

Thanks Paul.  The Eastport Pram only has fiberglass on the bottom panel and the #1 panels on the interior.  With your advice, I won't sand the fiberglassed panels until the weave is filled.  However, what about on the other plain wood (non-fiberglassed) panels?  Do I sand those in-between coats of epoxy, or wait until the end to sand?

Your first coat of epoxy on bare-wood panels will raise the grain and other tiny wood or insect things.  They can drag your roller or brush on subsequent coats, giving uneven epoxy thicknesses in places and more runs (just more sanding later).  After your first coat on plain wood has cured, run your hand over it.  If it feels like sand paper, sand it - CAREFULLY.  You only want to smooth off the burrs, not make it baby-butt smooth.  What ever you do, don't sand through the one layer of epoxy you just applied.

More experienced builders sometimes sand carefully after their first fill coat of fiberglass.  Some others wait til the second fill coat.  It saves a bit of sanding later, as long as they don't screw up and sand too much.  You pays your money and takes your chances.

If you do sand between coats, and you do want a clear finish, DO vacuum up the dust and wipe down with good denatured (not recycled) alcohol or something compatible with your epoxy.

Be patient & enjoy your build.