A detailed description is presented of the design and fabrication of the Marvel II composite wing. The wing was constructed in a short time using a combination of sailplane and modern prepreg composite structures technologies. The wing design requirements were to minimize the use of metal in the structure, to develop a high performance flap system which would be insensitive to a sand environment, and to explore composite production structural concepts.
The desired high lift capability was achieved through the use of a double slotted flap with a fixed slat. A unique flap support mechanism was developed to give excellent flap positioning over the flap angle range.
The wing was constructed in three major assemblies, the spars, the wing skins, and the flap and ailerons. The wing spar was constructed applying conventional sailplane techniques which uses a wet layup of S-glass rovings.
The fabrication of the wing skins was made in three steps. The original XV-11A wing was extended and used as the male mold. A heat resistant female mold was fabricated using an epoxy-graphite paste with a honeycomb backing. The mold had excellent dimensional stability and was light (300 lbs.). The wing skins were fabricated using Kevlar 250 deg. prepreg, Nomex honeycomb, and some high density foam. The wing skins were cured using a vacuum bag process.
The Marvel II wings were designed and fabricated along with major modifications to the fuselage in an eight month period. The aerodynamic performance was outstanding with an airplane lift coefficient in excess of 3.0. There were no structural problems encountered in the flight test program. The structural weight was much higher than expected. It was found that the weight of secondary structure was difficult to control.
From this development program, a methodology to produce excellent dimensional fidelity, and high structural efficiency wings has evolved. From the lessons learned on this prototype development program it is now possible to produce composite wing and fuselage structures for limited production aircraft at a modest cost and in a relatively short time frame.
