"The Royal Navy had taken its first steps into the steam age in the previous decade, but the associated method of propulsion – the paddle wheel – had major drawbacks for a man-of-war, not least in that they provided a large and vulnerable target. Use of steam propulsion was therefore limited to vessels – such as mail-packets, or gunboats for colonial service – which would be unlikely to engage in combat with other ships. The screw-propeller however, located as it was below the waterline, would remove this vulnerability. The success of the Archimedes – a civilian vessel – therefore encouraged the Royal Navy to build a vessel of its own, directly comparable in power and armament to typical paddle-gunboats already in service, so as to allow directly comparative testing.
The resulting design was to be HMS Rattler, an 894-ton, 185-ft long wooden sloop powered by a 440-hp steam engine, with an auxiliary sailing rig. The latter was to remain a standard feature of practically all warship types for the next half-century since it allowed a degree of independence from coaling locations as well as economy of operation. HMS Rattler was designed to carry a powerful armament – a single 8-inch pivot gun which could bear over a wide arc, and eight 32-pounders as broadside weapons. This armament was typical of gunboats of the period, which were more likely to be involved in shore-bombardments in remote locations than in ship-to-ship combat.
HMS Rattler was completed in 1843 and spent the next two years in trials, a variety of propeller shapes being tried out and relative efficiencies established. Later tests involved races with the generally similar, but paddle-driven, HMS Alecto. These culminated in the "tug-of-war" of March 1845 for which HMS Rattler is best remembered, when she was linked by a tow-cable stern to stern with the Alecto. Both vessels applied full power – a sight that must have been magnificent to see, waters swirling in Rattler's wake as her propeller churned, and foam thrashing from Alecto's twin paddle-wheels. In the event it proved no contest – HMS Rattler dragged Alecto behind her at a speed of two knots. The screw-propeller had proved itself…"
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