The vector ruling protractor
A 1924 technical report from the NASA Technical Reports Server, a scanned aeronautical document describing a vector ruling protractor for drawing airfoil force vectors, aimed at aircraft engineers and draftsmen. The pictures are line drawings of a large graduated circular protractor with radiating lines, straightedge clamps and drafting-table fittings, and a diagram of an airfoil with wind, lift, drag and moment vectors; a designer might take from them the clean diagrammatic style of precise angular measurement and labelled force-vector schematics.
