MODEL 206L COMPOSITE VERTICAL FIN

This paper describes a program to design and manufacture a composite vertical fin for the Model 206L helicopter. The composite vertical fin is of sandwich construction with precured facesheets of graphite/epoxy unidirectional tape adhesively bonded to Fibertruss core of varying density. A layer of aluminum wire screen is adhesively bonded to the outer surface of each facesheet for lightning protection. A separate precured leading edge of Kevlar 49 is bonded to the main fin structure. A filament-wound, tapered S-glass tail skid is mounted by two injection-molded fittings bonded into a graphite/epoxy closure at the base of the fin. A two-part closed cavity tool is used with each facesheet being laid up and cured on its half of the tool. The leading edge and lower closure are cured on separate tools. The entire assembly is bonded together in the cavity tool. This paper discusses in detail the design requirements, manufacturing process development, tooling approach, structural tests and follow-on production for the NASA/Army/BHT Flight Service Evaluation Program.