: agree, I was going from the standpoint of if the panels were preglassed with
: 4oz what is necessary after that and where. The chine damages I've seen
: were on the outside.

The strength of the joint is controlled by several factors. The filler in the epoxy the weight of the glass on the inside and the outside, how much you round over the chine before glassing the outside, how much the outside of the seam gets worn off with use and how often the wear is repaired.

My theory is the final thickness of the joint should be at least as thick as the plywood. To determine the thickness of the fillet you first have to determine how much you are going to round over the chine. Rounded chines take more abuse before the outside glass abrades away. If you like a really rounded chine and sand trough two layers and into the inside ply, make the fillets at least 1/8 inch thick.

Do not use lightweight fillers they are not as strong. I use fumed silica with just enough wood dust to match color. Beware silica epoxy does not sand so make the fillets smooth enough that the fill coats on the covering glass will handle the smoothing with sanding. I cover the seams inside and out with 6 ounces of cloth, 6 ounce tape inside the compartments, just the 6 ounce cloth inside the cockpitand outside just 6 ounce cloth.

Pre-glassing the panels before stitching precludes using the cloth to reinforce the seam. The inside glass is not that difficult to install in one piece after stitching if adequate fillets are installed. The only place I see necessary to pre-glass a panel is if you choose to glass the inside of the deck.

Lightening a kayak by reducing glass weigh makes a weaker boat. Unfortunately, you never know if you have too much glass on the seam or panels for your degree of use of the kayak, but you will find out when it is too light.

Be absolutely sure that all inside unglassed surfaces are completely sealed with epoxy before installing the deck. Any cracks or voids will show up as stains through to the outside. I roll on three coats. I scrape between the first and second coats and sand between the second and third coats. More work but totally sealed and the sanding keeps the weight down and makes a nice looking interior. Don’t overlook epoxy coating the shear clamps, deck beams, etc.