The BN-1 Spinner Kit is made of 6061 aluminum. The nominal thickness of the dome and bulkheads is .063. The dome can be supplied with a satin or polished finish. The kit is FAA approved for installation on many certificated aircraft such as Aeronca, Cessna, Luscombe, Piper, Stinson, and Swift.
Concentricity of the rear bulkhead is established by a snug fit on the bushings protruding from the prop flange. The center hole is sized large enough to clear the radius at the prop flange/pilot dia intersection. This radius can vary from zero to 3/16″ depending on manufacturer.
Concentricity of the front bulkhead is established by the prop mounting bolts. Spinner kits should never be installed without the front bulkhead.