By Don Leggett
Few buildings along the famous River Clyde region of Scotland figure as importantly to the history of shipbuilding, naval science and the British maritime empire than the small and innocuous brick structure that holds the Denny test tank: the world’s first commercial tank (or model basin).
The Denny tank, opened in 1884, was only the second of its kind, built on specifications provided by William Froude, an Oxford-trained mathematician and one-time collaborator with Isambard Kingdom Brunel. Froude designed the first private test tank to provide the British Admiralty with an accurate guide to how full-sized ships would perform at sea.
Well into even the twentieth century, shipbuilders continued to rely on the untrained eye, craft practice and a series of fairly arbitrary calculations to work out the optimum hull shape for ships of all varieties. Froude posited, and then demonstrated, that twelve-foot long model hulls propelled by railway carriage in a water tank 300 meters long would more accurately represent the behaviour of the same said design at sea.
The British shipbuilding industry was largely unconvinced of the benefits to be derived from Froude’s work, but he did find an influential supporter in the shipbuilder William Denny (whose firm built such ships as the King Edward, the first commercial vessel driven by Charles Parsons steam turbines). In a competitive business community where shipbuilders bid for contracts, accurately estimating ship speed and performance could provide a significant advantage.
William Denny (1847-1887) led his firm through a series of major shipbuilding reforms based on the use of experiments and rigorous sea trials to develop a working knowledge of efficient hull shapes. He instigated the practice of progressive trials to examine the relationship between engine power, speed and hull resistance in different ships; in the mid-1870s he began to closely work with Froude on the analysis of hull resistance; and in 1884 he finished work overseeing the construction of the test tank. He would later write of his firm’s approach to shipbuilding:
A quick and all-round approximation of any new proposal is the only platform from which a professional man can safely start; and it, again, can only be the outcome of years of laborious investigation, and observation, and experiment. The bulk of our brother-ship-builders, and I suspect pretty nearly all your men, don’t yet understand the meaning of this.
Today model testing remains a key part of shipbuilding practice, complimenting computer modelling. The machinery on display at the Dumbarton test tank (now part of the Scottish Maritime Museum) covers a wide chronology, but the museum displays have been presented as ‘Victorian’, complete with mannequin invisible technicians undertaking detailed study of ship curves and test tank measurements – while also moonlighting as night guards to the tank archives stored within the displays.
Dumbarton is a little over ten miles west of Glasgow. The frequent train service is recommended as it passes alongside the River Clyde, the birthplace of much of Britain’s former maritime empire.
For further details on visiting the tank visit the Scottish Maritime Museum website see http://scottishmaritimemuseum.org/dumbarton.html.