The Doodlebug mounted in the full-scale windtunnel at NACA’s Langley establishment in 1934. As predicted, the large wing fillets seen here reduced buffeting considerably. The improvement in the aircraft’s drag was considered almost incidental.

With a wing and fuselage geometry similar to the Junkers-F 13, the one-off McDonnell Doodlebug, the wing/fuselage junction of which is seen here with no modification, was selected by NACA to explore the effect of various interference-reducing measures.