George Rennie and the engineering behind Calypso's machinery

George Rennie, one half of J. and G. Rennie, designed machinery for the Royal Navy while the firm also built locomotives and contributed to boiler development. His tail-fin-inspired screw propeller was an efficient idea that proved difficult to cast accurately. Rennie's papers on friction and the movement of water past hulls show how theoretical investigation fed practical marine engineering. His election to the Royal Society and the Institution of Civil Engineers also places warship machinery within a broader professional engineering culture. The class's horsepower figure therefore belongs to a larger industrial and intellectual history.