Test models 'Swan' and 'Raven', 1867.
© Science Museum / Science & Society Picture Library
Models (6 ft). These two models of ship's hulls were built by William Froude who was the ship designer most asociated with fundamental advances in hydrodynamics in the 19th century. Froude used a steam launch to tow variously sized models of the 'Swan' and 'Raven' to test resistance and used a dynamometer to record the results. The models were built from his observations of water birds. The sharp-ended Raven experienced more resistance than the bulbous Swan. He deduced the scaling law that related the different resistances to each other by means of a quantity now known as Froude's number and demonstrated that experiments carried out on scale models could be used to predict the behaviour and characteristics of their full-sized counterparts.