Semi-monocoque

The term semi-monocoque or semimonocoque refers to a stressed shell structure that is similar to a true monocoque, but which derives at least some of its strength from conventional reinforcement.

Semi-monocoque aircraft fuselages differ from true monocoque construction through being reinforced with longitudinal stringers.

[1][2] The Mooney range of four seat aircraft, for instance, use a steel tube truss frame around the passenger compartment with monocoque behind.

[3] The British ARV Super2 light aircraft has a fuselage constructed mainly of aluminium alloy, but with some fibreglass elements.

[4] Peter Williams' 1973 Formula 750 TT-winning John Player Norton racer was an early example of a semi-monocoque motorcycle.

Semi-monocoque structure inside an aircraft's rear fuselage
ARV Super2 with semi-monocoque fuselage
Peter Williams' 1973 John Player Norton 750 with sheet stainless steel semi-monocoque frame, exhibited at Castletown, Isle of Man in 1999