:. . . Can a vinyl decal be placed
: on bare wood and then fiberglassed, epoxied and varnished over
: it without ill effects?

CAN it be done? Sure. SHOULD it be done? No. Epoxy doesn't stick well to vinyl. Come to think of it, it doesn't stick at all.

Your best bet is to glass the boat normally, then put on the decal before varnishing. If you want a layer of something over the decal to give it some protection against dings and dents, then put a patch of glass over it, extending the glass about 2 inches on either side of the decal. A little gentle sanding will remove the edges of that patch and blend it into the base material. You'll want to put on three coats of resin to fill the weave on this patch, but the batches are going to be measured in drops, or maybe a teaspoon of resin at most, so this will be quick work.

Layering the decal between your structural fiberglass and the cosmetic cover completely solves the problems associated with putting the decal under the structural glass.

Umm, Why a vinyl decal in the first place?

There are decal materials available in standard letter-sized sheets which you can feed through a laser or inkjet printers. I used one by a British company (I think the product was called Lasertech). It was applied to baere wood with water, then when it had dried you went over it with pure turpentine and the base dissolved, leaving the inks in the wood, as if you have printed directly on the wood surface. I probaably have the wrong name for this stuff as when I searched for it I found, instead, DecalPaper.com www.decalpaper.com/category-s/4.htm

The illustration below is from their site. I haven't tried the variety of decal paper they offer for use on wood. Their process calls for spraying the decal with Krylon clear acrylic spray before applying. You should be able to glass over that better than over vinyl, but I still wouldn't advise it directly on the bare wood.

With a decal method where there is no decal base left, and the pigments are already soaking into the wood, you shouldn't have any problems with glassing over it. Just make sure that you give it a coat of shellac if you've used any oil-based solvents in the decal process. That will provide a barrier between any oily residue and your epoxy, ensuring a good bond.

Hope this helps

PGJ