The Timber Crisis
Unicorn was built during a period of extraordinary technical change, when, in the space of only a few years, wooden sailing ships were succeeded by ships built of iron and powered by steam.
When Sir Robert Seppings became the Surveyor of the Navy, a timber crisis had reached its peak in Britain. Forests in the south of England had been denuded to provide timber for shipbuilding, and forests in the north of England had been felled to provide charcoal for iron smelting. The invention of the blast furnace provided a dramatic solution to both problems at one stroke. Iron could now be smelted using coal: both coal and iron ore were plentiful in the north of England and the new abundance of cheap, high quality iron allowed its use in shipbuilding.
Seppings developed his system of shipbuilding at the height of this crisis. In particular ‘compass timber’, the great curved pieces of oak needed to suit the complex shapes of a wooden warship, had become almost unobtainable. The fleet which fought at Trafalgar had been patched up with compass timber salvaged from ships captured during earlier wars, and a fresh supply would take many decades to grow.
Seppings’ aim was to build stronger ships, using less timber and more iron, and his construction methods minimised the use of compass timber. A ship of Unicorn’s size would have required the timber from 1,000 oak trees, and it was estimated that the equivalent of 200 trees could be saved using Seppings’ methods.