The early steamships
Paddling into history
Steam goes to sea
There were a number of experimental vessels driven by pioneering steam engines in the eighteenth century, but the first practical steam-driven craft was probably the Charlotte Dundas of 1801 which was built to tow barges on the Forth-Clyde Canal in Scotland. By 1812, the steam boat was carrying passengers on the River Clyde. The decade to 1820 saw steamer services on rivers and estuaries well established. The first services across open waters began when a service from the Clyde to Belfast opened in 1818. During the 1820s steamships grew in both power and size, and became capable of voyaging almost anywhere in the world, although most of the time the vessel would be under sail. These were often delivery voyages: many early steamships were built in the UK for service elsewhere in the world. It was some time before regular long-distance steamer services were established.
Early steamships were driven by paddle wheels. Although some river craft had the paddles placed right at the stern, the paddles were usually placed on either side of the ship about the centre point of the hull. Among the developments that made the paddle steamer more efficient was the invention of feathering gear. This kept each paddle blade almost vertical when entering and leaving the water, making it push the ship along more effectively and minimising splashing which wasted energy.
Iron replaces wood
Early hulls were made of wood. The length of planks and frames was limited by the size of trees, and all had to be fastened together and the gaps between them filled to keep the hull watertight. Connecting together a large number of pieces of wood made for inherent weaknesses, and this limited the size of vessel which could be built. Additionally, the stresses and vibrations which arose from a working steam engine were often too much for a wooden hull. Iron plates could be joined together so firmly that there was almost no limit to the size of hull, and iron had the strength to withstand the strains imposed by a steam engine. However, at first iron was very expensive to produce, of uneven quality, and available only in relatively small plates. It also had to be laboriously drilled by hand before plates could be riveted together. Although small vessels with iron hulls were built in the eighteenth century (disappointing the cynics who predicted that they would not float!) it was not until the 1840s that iron hulls became widespread. Brunelís Great Britain of 1845 did much to establish the iron ship.
Limitations of paddling
The design of the Great Britain was altered during her construction so that she could be driven by a screw propellor rather than paddle wheels. The recently-developed screw had a number of advantages. Being submerged continually a screw was better in heavy weather, when a rolling paddle steamer would find first one and then the other of its paddles out of the water. The amount of cargo a paddle steamer could carry was limited, as too much weight of cargo would so submerge its paddles that they would not work efficiently, if at all. Hence paddle steamers were best suited for carrying passengers and light goods such as mails, and performed best in sheltered waters.
With these limitations, the paddle steamer was a dead end, although it had proved the practicality of using steam to drive a ship. It was incapable of further development, and the future of steam lay with the screw-driven vessel.