Composite rotating coupling covers

Rotating Coupling Covers (RCCs) enclose shaft flanges on waterborne shafting. The existing fairings are doubly curved Cu-Ni with tight dimensional tolerances, so are difficult and expensive to fabricate. In addition, they have a history of leaking, as evidenced by extensive corrosion of the flanges. A preservative is pumped into the void enclosed by the RCCs, but shaft rotation and other forces cause the material to separate from the flanges. The objective of the work described herein is both to reduce manufacturing cost and prevent water intrusion. In the composite design, the RCC is predominantly glass-reinforced plastic (GRP) filled with polysulfide. Thus in this concept the MIL-STD-2199A covering for waterborne shaft sections is extended over the shaft coupling, although both GRP and polysulfide components are thickened substantially. Metallic components are limited to hardware for joining the shell halves. In past development work the composite RCC shell halves were fabricated separately. In the current approach they are fabricated with out-of-autoclave prepreg on a one-piece male mold; after cure the two shell halves are machined from the tool. Male molding allows fit-up to the shafting with a high degree of accuracy, and the use of external tooling (cauls) during de-bulk and cure results in a smooth hydrodynamic surface.