A Tug-of-War, Naval style – HMS Rattler vs HMS Alecto
The Industrial Revolution that swept through 18th and 19th century Britain was driven by steam. Coal-fired engines were everywhere, pumping out mines, driving steam hammers in forges and powering the machinery in the new factories. Shipbuilding too was part of the revolution, with mechanised sawmills and block-making machines installed in the Royal Dockyards. Every aspect of life was touched by the new technology save one. At the end of the 18th century the ships of the Royal Navy were still driven by the wind, just as they had always been. But change was coming at sea too.
Experimental steam powered vessels began to emerge towards the end of the 18th century. The first was built in 1788 by Patrick Miller and featured a single paddle wheel mounted between twin hulls. This rather clumsy design was improved on in 1802 with the launch of the Charlotte Dundas, a steam launch with a single hull and a paddle wheel mounted in a case on her centre line. Soon larger paddle steamers were being built, generally with a pair of paddle wheels mounted on the sides of the hull, and the new power source began to take off.
The adoption of paddle wheels to transfer power from a steam engine to the sea came from observing watermills, which where a common feature of the early modern landscape. These mills used the push of a stream of water to turn a paddle wheel. Steam ships simply reversed this process, using the wheel to push against water. But marine engineers soon began to suspect that paddle wheels might not be the most efficient way of transferring motive power. For much of the wheel’s cycle the flat paddles were using energy to either push water downwards or lift it up. Only for an instant at the very bottom of the wheel’s cycle, at the “6 o’clock” position, was water being driven directly backwards. Paddle wheels might churn the water in an impressive way, but how much of that thrashing motion was efficient?
Another issue was that paddle steamers performed best in calm water. This made them ideal for lakes and the major river system of North America, but not the open ocean. As a ship rolled in a heavy sea one paddle wheel might be fully submerged while the other was lifted clear of the waves, placing huge strain on the ship’s engines. What was required was an alternative means of propulsion that was permanently under the water.
The solution proposed was the propeller. The idea was derived from Archimedes screw, an ancient Greek method for pumping water uphill. No less than four engineers independently came up with the same idea between 1830 and 1836 – a Frenchman, a Swede and two British inventors. The first propellers had two thin blades, not unlike early aircraft propellers, but was soon modified to the three and four blade versions we are familiar with today.
The Royal Navy was particularly interested in the new technology. When they started to adopt steam power on their warships, they had found the large paddle wheels then in use a considerable nuisance. Not only did they mask much of a ship’s main armament mounted along the side, they would also be very vulnerable to damage from enemy fire in action. Replacing these wheels with a propeller mounted at the stern beneath the waves would solve both problems. The only question left was whether the new technology was indeed more efficient than, as their supporters claimed. Unfortunately it was a question that early Victorian mathematics was incapable of answering. Time for that tug-of-war.
The ships selected to decide the issue were a pair of steam-powered frigates of a similar size. Both were powered by the same engine supplied by a single manufacturer. HMS Rattler was then fitted with one of the new propellers, while HMS Alecto got paddle wheels. In March 1845 the ships were put through their paces. First up was a race over a hundred miles, which the Rattler won comfortably. Next came the famous tug-of-war. The frigates were tied stern to stern and then both sailed off in different directions. With the two ships at full power, the Rattler was able to pull her rival along at a brisk 2.7 knots and so demonstrate her considerable power advantage. The Admiralty was convinced, and the propeller was here to stay.
