Sounds as if there was some kind of contamination when the wood was glassed. Did you wipe it down with an oil-based thinner (like lacquer thinner) or use a tack rag to clean it before you applied the glass? Or build it in a space near a clothes dryer exhaust? Or heat the shop with a kerosene heater? Was the glass sealed in plastic until it was ready to be applied to the boat?

The other possibility is that there was only enough epoxy to wet out the glass, but not enough to soak into the wood.

However it happened, it's fixable. The boat needs to be stripped of all loose glass, sanded clean and have new glass applied. At least it happened when you were rehabbing it anyway.

Good luck,

Laszlo

I wiped it with a tack cloth and alcohol. I don't think contamination was the problem.

Interestingly, the problem was only on the bottom two chines (four chine hull).  Sides, deck and interior are fine. I thought UV might be the problem except for the limited extent of this problem. 

This actually works in my favor!

Uh-oh. When you say "tack cloth," do you mean the kind of tack cloth you buy at the paint store, which is impregnated with a sticky mixture to help it pick up dust? If so, that might be part of your problem. If you mean a clean piece of cheese cloth with denatured alcohol, that's OK.

I never use tack clothe or cheesecloth w/alcohol on bare wood. It is not needed. I sand the wood one last time, brush dust off with a cheap paintbrush, vacuum, and then ... wipe the wood with my bare hands. Herroshoff did it that way, so can I.

You need generous epoxy on the cloth to saturate the cloth AND wood below. If you did it right, after letting epoxy settle in for 10-15 minutes you will actually remove epoxy by screeding the surface  lightly w/plastic squeegee thingy held at about a low 15 degree angle. Dispose of excess epoxy in any old container and set aforementioned container on concerte away from flammables in case the wad of googe decides to overheat and go flamo on you.

glass should appear transparent with no silvery speckles =  to dry.

Most likely you will need to tack off air bubbles with a light sweep using a short stiff bristle paint brush - I trim the bristles of cheap brush down about halfway.   And then, after epoxy greens up = gelled but not cured hard - roll on fill coats of epoxy.

Bare hands are fine, as long as they don't have skin oils or other contaminants on them. If they do,the bond could be messed up. So as long as builders haven't sweated, eaten a hamburger, pet the dog, rubbed their nose, picked up a greasy tool, etc. since the last time they thoroughly cleaned their hands, it'll be OK.

Laszlo