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Class overview
Name	Hermes-class 20-gun ships
Operators	Royal Navy
Preceded by	Laurel class
Succeeded by	Cyrus class
Completed	4
Lost	1
Scrapped	3
General characteristics
Type	Post ship
Tons burthen	507 76⁄94 (as designed)
Length	119 ft (36.3 m) (gundeck) 99 ft 10.625 in (30.4 m) (keel)
Beam	30 ft 11 in (9.4 m)
Sail plan	Full-rigged ship
Complement	135
Armament	Hermes & Myrmidon (20-guns) Upperdeck: 18 × 32-pounder carronades + 2 × 9-pounder guns Ariadne & Valorous (26-guns) Upperdeck: 18 × 32-pounder carronades QD: 6 × 18-pounder carronades Fc: 2 × 9-pounder bow chasers

The Hermes class were a series of four 20-gun ships, launched between 1811 and 1816. Two pairs of ships were produced, to slightly different designs – the first two had 20 guns and were unrated flush-decked ship-sloops, whilst the latter two were converted to 26-gun sixth-rates. The design was based on the ex-French 20-gun corvette Bonne Citoyenne, which the British had captured in 1796.

The first pair was built at Milford Dockyard on the north side of Milford Haven. Hermes was launched in 1811 and Myrmidon in 1813. Milford Dockyard was closed following their construction, and the second pair were built at the new Pater (later Pembroke Dock) Dockyard on the south side of Milford Haven.

The second pair – Valorous and Ariadne – were launched on the same date in 1816. They were modified at Plymouth Dockyard in 1820 and 1821 respectively, before their first commission, by the addition of quarterdecks and forecastle to what had originally been flush-deck vessels, and they were at that time re-classed as 26-gun sixth rate post ships.

The Cyrus class was based on the design of the Myrmidon of the Hermes class.

• HMS Hermes
  • Builder: Milford Dockyard
  • Ordered: 18 January 1810
  • Laid down: May 1810
  • Launched: 22 July 1811
  • Completed: 7 September 1811
  • Fate: Grounded and burnt in action at Mobile in 1814.
• HMS Myrmidon
  • Builder: Milford Dockyard
  • Ordered: 2 August 1811
  • Laid down: July 1812
  • Launched: 18 June 1813
  • Completed: 6 February 1814 at Plymouth Dockyard
  • Fate: Broken up at Portsmouth in 1823.
• HMS Ariadne
  • Builder: Pater Dockyard
  • Ordered: 28 November 1812
  • Laid down: April 1815
  • Launched: 10 February 1816
  • Completed: 21 March 1816
  • Fate: Sold to break up at Alexandria in 1841.
• HMS Valorous
  • Builder: Pater Dockyard
  • Ordered: 28 November 1812
  • Laid down: March 1815
  • Launched: 10 February 1816
  • Completed: 26 March 1816 at Plymouth Dockyard
  • Fate: Broken up at Chatham in 1829.

• Rif Winfield, British Warships in the Age of Sail, 1793–1817, Chatham Publishing, London 2005.
• Davy Lyon, The Sailing Navy List – all the Ships of the Royal Navy 1688-1860, Conway Maritime Press, London 1993.