The Interference Between Struts in Various Combinations
This is a 1934 NACA aeronautical technical report, apparently a NASA Technical Reports Server scan, presenting experimental data on interference drag between struts and related shapes in wind-tunnel tests for engineers. The pictures are plain engineering graphs with thin black curves, data point markers, and labelled axes plotting drag coefficients against strut spacing and angle. A designer could take from them only the sparse, hand-drafted chart vocabulary: grid paper, crosshatched axes, small geometric diagrams of paired struts and plane chords.
