Penguin
Class overview
Name	Osprey-class sloop
Operators	Royal Navy
Cost	Between £49,217 (Cormorant) and £56,221 (Pelican)
Built	1874–1877
In commission	1874–1949
Completed	5
Scrapped	5
General characteristics [1]
Type	Screw composite sloop
Displacement	1,130 long tons (1,150 t)
Length	170 ft (51.8 m) (p/p)
Beam	36 ft (11.0 m)
Draught	15 ft 9 in (4.8 m)
Depth	19 ft 6 in (5.9 m)
Installed power	666–1,056 ihp (497–787 kW)
Propulsion	1 shaft 1 × 2-cylinder horizontal compound expansion steam engine 3 × cylindrical boilers
Sail plan	Barque rig
Speed	9–12 knots (17–22 km/h; 10–14 mph)
Range	1,480 nmi (2,740 km; 1,700 mi) at 10 knots (19 km/h; 12 mph)
Complement	140
Armament	2 × 7-inch rifled muzzle-loading guns 4 × 6.3-inch 64-pounder rifled muzzle-loading guns

The Osprey class was a Royal Navy class of screw-driven sloops built between 1874 and 1877. Nine additional ships were built to a revised design, the Doterel-class sloop. They were the first class of ship in the Royal Navy to use glass scuttles.

They were of composite construction, with wooden hulls over an iron frame. Five ships of the class were built, which had been designed in 1874 by the Royal Navy's Chief Constructor, William Henry White.^[1] They were the first ships in the Royal Navy to have glass scuttles instead of solid plug scuttles.^[1]

The original design, as fitted to the first two ships of the class, was a single-expansion returning-rod steam engine, but the power was insufficient, and they failed to meet the contracted speed. Wild Swan and Penguin were re-engined after their first commission to match the better engines in the rest of the class.^[1] In the final installation, power was provided by three cylindrical boilers, which supplied steam at 60 pounds per square inch (410 kPa) to a two-cylinder horizontal compound-expansion steam engine driving a single 13-foot-1-inch (3.99 m) screw. The power varied wildly from ship to ship, with Penguin generating only 666 indicated horsepower (497 kW) and Pelican managing nearly twice as much, at 1,056 indicated horsepower (787 kW). Because of this, top speeds ranged between 10 and 12 knots.^{[1][Note 1]}

They were armed with two 7-inch (90cwt) muzzle-loading rifled guns on pivoting mounts, and four 64-pounder muzzle-loading rifled guns (two on pivoting mounts, and two broadside). Four machine guns and one light gun completed the weaponry. Wild Swan and Pelican later had the muzzle-loading guns replaced with two 6-inch (81cwt) breech-loaders and six 5-inch (31cwt) breech-loaders.^[1]

All the ships of the class were provided with a barque rig,^[1] that is, square-rigged foremast and mainmast, and fore-and-aft sails only on the mizzen mast.

They had a complement of approximately 140 men.^[1]

The design was revised in 1877 and nine ships were ordered to a modified version, the Doterel-class sloop. Identical in many respects, the Doterels lacked the graceful clipper bow of the Ospreys, although they benefited from more power.^[1]

• Ballard, G. A. (1939). "British Sloops of 1875: The Larger Ram-Bowed Type". Mariner's Mirror. 25 (January). Cambridge, UK: Society for Nautical Research: 35–49.
• Preston, Antony; Major, John (2007). Send a Gunboat: The Victorian Navy and Supremacy at Sea, 1854–1904 (2nd ed.). London: Conway. ISBN 978-0-85177-923-2.
• Roberts, John (1979). "Great Britain and Empire Forces". In Chesneau, Roger & Kolesnik, Eugene M. (eds.). Conway's All the World's Fighting Ships 1860-1905. Greenwich, UK: Conway Maritime Press. ISBN 0-8317-0302-4.
• Winfield, R.; Lyon, D. (2004). The Sail and Steam Navy List: All the Ships of the Royal Navy 1815–1889. London: Chatham Publishing. ISBN 978-1-86176-032-6. OCLC 52620555.