Complex sentence: The fuselage was built around four wooden longerons, though frames and stringers formed a circular cross-section cover in duralumin at the nose and tail, with fabric in the central, cockpit region.
Split into simpler sentences: The fuselage was built around four wooden longerons, though frames and stringers formed a circular cross-section. The covering was in duralumin at the nose and tail, with fabric in the central, cockpit region.