A study of static stability of airships
A 1924 NACA technical note on the static stability of airships, issued as a technical report for aeronautical engineers and researchers. The two pages are engineering drawings: a plan-view outline of airship hull shapes at different aspect ratios, and a line graph of pitching moment against angle of pitch for several fin-thickness groups. A designer could take from them the clean, sparse vocabulary of mid-century technical diagrams, with fine black linework, dashed and dotted curves, and labelled axes on plain paper.
