The Minimum Induced Drag of Aerofoils
A 1923 aeronautical report from the NASA Technical Reports Server, a technical paper on the minimum induced drag of aerofoils, written for engineers and aerodynamics researchers. Its pictures are a dense, heavily degraded scan of a page and a line diagram of slanted parallel lines with labelled vortex-like arrows and dashed construction lines, which suggests a designer could borrow its hatched, schematic linework for technical or diagrammatic graphics.
