OK Here's another question: I just finished taping the inside and outside of the seams together, to join the hull and deck. After an initial coat of epoxy to wet the tape I applied a second coat to fill the weave. Now this filled tape stands slightly proud of the surrounding surface. If I sand the edges of the tape to gradually blend them into the surrounding surface, that will, by definition expose a small amount of the cloth, at those edges. Can I just rely on the varnish to cover this or do I need to re-apply more epoxy after sanding?

If you wish to have ALL exterior glass, this includes exterior taped seams, to be totally and consistently transparent it is best to wet-out the fiberglass in the way I outline on my page - http://www.laughingloon.com/epoxy.html

Other methods may be good enough for some, if you don't care how fantastic it can look, but you are putting so much work into the boat, why not have it be the best it can. If you've made a few boats already you can aim higher.

I used to wet-out my glass as outlined on my "Epoxy" page and then glass the exterior seam using regular hardener at 70˚.

I could see "silver fleck" in the seams, a silvery sheen to the glass when viewed at certain angles. I saw this for years on other people's kayaks, and I realized it was telling me the glass was not TOTALLY wet-out.

My lay-ups need to be perfect every time so I can sleep the night before. you can do as you choose.

Back to answering your question.

I ran into this, "running into the glass" sanding issue many years ago. It drove me nuts. Always wondering if I put on enough fill coats and if I kept sanding would I hit the glass!

When I started strip building, the recommended method was wet-out, fill coats, sand with 80 grit, 120 grit, and varnish.

As a furniture builder I realized I'd probably get a deeper luster if I sanded to 220 grit before varnish and the varnish would smooth out better. But sanding with 80 grit, then 120 grit and finally 220 grit got me closer and closer to the glass and I'd never know if I'd be able to sand that far without hitting it.

I needed to sleep again, the night before sanding, so I came up with a method for consistent results.

I now glass the whole boat, plus seam tape, stem reinforcement and add three to four fill coats. Then I rough sand the exterior glass with 60 grit on a ROS and feather seam and stem reinforcement glass edges. If I see any glass weave showing I quickly move on in the sanding process. THEN, I apply two new coats of epoxy.

Epoxy is weird stuff. It follows the underlaying surface to which it is applied. People try to use a squeegee to make it lay flat over the glass weave with limited success. The fill coats applied over the weave with a roller will remain the texture of the fiberglass cloth. Rough sanding with 60 grit is fast and levels the surface. The new coats of epoxy can be as smooth as varnish, requiring much less sanding.

So, no, I wouldn't leave exposed glass and varnish over it. But others might.

Your choice as always.

All the best,
Rob