Complex sentence: Behind a sloping firewall the fuselage was all-metal and of rectangular section, its duralumin tube frame covered with long, narrow dural strips placed horizontally, edge-to-edge.
Split into simpler sentences: Behind a sloping firewall the fuselage was all-metal and of rectangular section. Its duralumin tube frame was covered with long, narrow dural strips placed horizontally, edge-to-edge.