: Is it advised to fiberglass the interior of plywood hulls?

I built the first two S&G kayaks in 1985. Kayaks built now number 6 (7) if you count my partner's. None have had glass in or out, just on the seams. Of kayak number 3 (Seaward), 4 were built at the same time and a fifth soon after - no glass. The Encore double was bounced off Fiji's reefs during the circumnavigation. All of my kayaks have a hard life, all survive. The latest two use 3 mm ply and weigh 18 kg with everything fitted (deck fittings, hatch covers, rudder, pedals etc.). The bare stripped hull of the latest before cockpit and hatch rims etc. came to 13 kg.

I figure 2 to 3 times as much epoxy per area with glass vs no glass. That is 2 to 3 times the weight. Possibly each kayak uses 4 litres without glass vs 12 litres of epoxy with glass, with each litre weighing about a kg.

Alex