The Effects of Some Surface Irregularities on Wing Drag
A 1939 NACA technical report from the NASA Technical Reports Server on how surface irregularities such as rivets, lapped joints, and roughness raise wing drag, written for aeronautical engineers and researchers. The pictures are engineering graphs of drag increase against chord position and rivet pitch, with a wing section profile and small diagrams of rivet heads. A designer could take from them the spare, measured line style of technical plots, with thin grid lines, dashed and solid curves, and labelled axes.
