Law of similitude for the surface resistance of lacquered planes moving in a straight line through water
This is a 1925 NACA technical memorandum, issued by the National Advisory Committee for Aeronautics, reporting towing-tank tests of resistance for flat lacquered plates and end sections moving through water. Its audience was aeronautical and naval engineers. The four pictures are line graphs plotting resistance in kilograms against speed in metres per second, with tabulated test data above the curves and fitted curves through scattered data points; a designer might take from them the clean grid, labelled curve numbers, and rising parabolic lines.
