stressed skin

Fuselage
The first planes were built around a wooden frame (later made of metal tubes) covered by fabrics. The whole was strengthened by cables (initially piano wire). The frame had to sustain all the flight constraints. The idea of the "stressed skin" dated back to the years before World War I, but it began to find applications only in the thirties. The flight constraints rested now not only with the frame but with all the skin of the plane. The frame could be lightened or be left out altogether, resulting in weight reduction and volume savings.
Although metal won the day in the thirties, wood remained the main component of several planes during World War II. The most famous is the Mosquito. Actually, it was made of plywood: three hulls were molded (two in plywood, one in balsa) and glued together. None of the hulls was strong enough by itself but the three together resulted in a strong airframe. The Russians too were great user of wood in their planes. Almost all their fighters (Ya...