Complex sentence: By then glass fibre reinforced polyester resin was available and so it was redesigned using a balsa wood/glass fibre'sandwich', with the load-bearing points and the edge of the cockpit canopy strengthened with plywood.
Split into simpler sentences: By then glass fibre reinforced polyester resin was available and so it was redesigned using a balsa wood/glass fibre'sandwich'. The load-bearing points and the edge of the cockpit canopy were strengthened with plywood.