"castor" was built at chatham dockyard and launched on 2 may 1832. she was one of a two ship class of frigates, built to an 1828 design by sir robert seppings, and derived from the earlier "stag" class. the "castor" class had a further of beam to mount the heavier ordnance. "castor" cost a total of £38,292, to be fitted for sea.