: do you have to put fibreglass sheet on the hull (inside and out) or
: can you just tape the seams and use a paint to seal the hull ...
: how thin can the plywood be if you can build a kayak like this (if
: it's possible). cheers

: do you have to put fibreglass sheet on the hull (inside and out) or
: can you just tape the seams and use a paint to seal the hull ...
: how thin can the plywood be if you can build a kayak like this (if
: it's possible). cheers

I’ve worked a lot with 3 mm ply that wasn’t glassed. I did not use S&G with ply that thin: On a 5-plank ply canoe I glued chine logs to the sheer and bottom planks while flat and planed bevels for the bilge planks. Chine logs give more support than tape IMHO. Finish was ordinary latex paint (2 top, 3 primer) over sanding sealer. It’s stored indoors and used gently. Worked great, boat is still as new after 4 years. This method is much cheaper than glassing, not much epoxy required, but for a really long and skinny kayak I would consider glassing.

On a WRC composite strip canoe with a ply bottom I am building I do not intend glassing, but It has ribs - I wanted the antique look. It’s glued with no fasteners, I don’t expect much if any additional build hours or weight compared to normal methods, but it is slower on a calendar basis.