Torpedo gunboats were designed to keep the sea and cruise with the fleet in home waters and the Mediterranean. Their function in wartime was to fight the smaller craft of a hostile fleet, or to pop in and pick off the cripples when the chance arose during the progress of an engagement. They were also valuable as scouts and despatch boats. The Rattlesnake (length 200 feet, beam 23 feet, draught 8 feet, displacement 550 tons; contracted speed 18.5 knots) armament; one 4-inch gun, six three pounder quick-firing guns, two fixed torpedo tubes, and two launching carriages, was the first of this class of six vessels. The experience gained from this vessel was used by those responsible for the newer Sharpshooter class of twenty-five vessels. The Sharpshooters (length 230 feet, beam 27 feet, draught 8 feet to 8 feet 6 inches; displacement 735 tons) were armed with; two 4.7-inch guns, four 3-pounder guns, and four torpedo tubes.