I've built three S&G's in the last three years and have glassed the hull/deck eges on all three SOLEY for abrasion and ding resistance it provides to the plywood deck edge. It is not a hull integrity issue, it is a maintenance reduction issue.

Years ago, I built a plywood boat where I did not glass the hull/deck edge, BIG MISTAKE. The edge became a high maintenance area because it dinged easily and had to be fixed promptly lest rot start. The Okoume (or worse, Luaun) plywood commonly used for S&G project is not very rot resistant. Glassing the edge seems to protect against all but the most vicious attacks.

On the last kayak, built this summer, I glassed the hull sides and bottom exteriors first and let cure before I installed the deck. After the deck was installed to wooden shear clamps and the edges rounded, I gave the exterior deck a coat of resin and let it cure. If you use ring nails to attached the deck edge to the sheer clamp, set the nails flush or SLIGHTLY below the surface with a punch ground to the diameter of the nail head. I then masked with "fine line" 3/4" masking tape about 1" either side of the deck edge. I cut my own 3" glass tapes out of scrapes from the hull glassing and resined them to the deck edge. (PAY ATTENTION NOW, this is the BIG TRICK!) After the resin had started to set but before it was rock hard, I trimmed the edges of the glass with a razor blade at the edge of the masking tape. This goes very fast and makes a quick, neat job with less edge to work down than with true fiberglass tapes and no masking.

I have not been glassing the decks and the boats do not seem to suffer for it. I have been painting the hulls and one inch in on the deck to cover the glass work and varnishing the decks. The last one I did, the glass work was good enough to have been varnished all around if desired (which I don't, too much (ply) wood showing for my taste). Point is, done well, the added taping of the hull deck joint need not detract from the appearance AT ALL!

I recommend you take the extra time to glass the edges.

Craig