HMS Rattler as an experimental screw sloop

HMS Rattler began as an order for a four-gun paddle vessel before the Royal Navy changed the design into a nine-gun screw sloop and called on Surveyor of the Navy William Symonds to rework it. The ship paired a 200 nominal-horsepower vertical single-expansion engine with a screw propeller while retaining a mixed pivot and broadside armament. The machinery and fitting-out cost roughly £27,000, making the propulsion choice a concrete procurement commitment rather than a laboratory demonstration. Rattler subsequently served on the west coast of Africa and the East Indies station, where the experimental arrangement entered active overseas service. Her comparatively short career also illustrates the speed of marine-engine development in the thirteen years between launch and breaking up.