Sphinx-class post ship

Class overview
NameSphinx-class post ships
Operators Royal Navy
Completed10
General characteristics
TypeSixth-rate post ship
Tons burthen431 37/94 (as designed)
Length
  • 108 ft (33 m) (gundeck)
  • 89 ft 7.375 in (27.31453 m) (keel)
Beam30 ft 1 in (9.17 m)
Depth of hold9 ft 8 in (2.95 m)
PropulsionSail
Sail planFull-rigged ship
Complement140 (reduced to 134 in 1794).
Armament
  • UD: 20 × 9-pounder guns
  • QD (added 1794): 4 × 12-pounder carronades
  • FC (added 1794): 2 × 12-pounder carronades

The Sphinx-class sailing sixth rates were a series of ten post ships built to a 1773 design by John Williams. Although smaller than true frigates, post ships were often referred to incorrectly as frigates by sea officers, but not by the Admiralty or Navy Board.

The first vessel in the class was launched in 1775, six more in 1776, two in 1777 and the last in 1781. The vessels of the class served in the Royal Navy during the American Revolutionary War. Three of them - Sphinx and Ariel in September 1779, and Unicorn in September 1780 - were captured by the French Navy, but Sphinx was recovered in December 1779 and Unicorn in April 1781. Some survived to see service in the French Revolutionary and Napoleonic Wars.