The Distribution of Loads Between the Wings of a Biplane Having Decalage
This is a 1927 NACA technical note from the National Advisory Committee for Aeronautics, a government aeronautical research report on how lift divides between the upper and lower wings of a biplane with decalage. Its pictures are plain black-and-white engineering charts with fine grid lines, labelled curves, and small typeset captions, showing measured lift coefficients plotted against angle of attack and wing offset. A designer could take from them a sense of technical graph layouts, dense hairline grids, and sparse monochrome typography for diagrams.
