The Hb class was a class of six 40-gun frigates of the French Navy, designed in 1781 by Jacques-Nol San. Captured by the British Navy on 4 September 1782, the ship became the model for the British Leda class frigates. These ships were armed with 26 long 18-pounder guns (later increased to 28), 12 long 8-pounder guns and 4 36-pounder obusiers, and had a designated crew of 300. HMS Sybille was originally the 38-gun frigate Sybille of the French Navy, launched in 1791 in Toulon. She was captured by the 50-guns HMS Romney in 1794, and commissioned into service in the Royal Navy, where it served until 1833. HMS Sybille participated in several notable ship actions, capturing two French frigates and several privateers and brigs; and she participated in the Battle of Copenhagen, where it bombarded the city. After the Napoleonic Wars, on anti-slavery duties off West Africa from 1827 to 1830, Sybille captured numerous slavers and freed some 3,500 slaves.