The Alecto-class steam vessels (SV3) later reclassed as Third Class Sloops, were designed by Sir William Symonds, the Surveyor of the Navy. The design was approved on 12 April 1839. Initially four vessels were ordered and completed. A fifth unit was ordered (Rattler), but was reordered as a screw propelled vessel. And a sixth unit had been ordered but was requested to be reordered to a different design. The screw driven Rattler participated in the first of three 'tug o- wars with the Alecto. The vessels all participated during the Russian War. All had gone to the breakers by the mid-1860s.
