Osprey-class sloop

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.

Design
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. They were the first ships in the Royal Navy to have glass scuttles instead of solid plug scuttles.

Propulsion
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. In the final installation, power was provided by three cylindrical boilers, which supplied steam at 60 psi to a two-cylinder horizontal compound-expansion steam engine driving a single 13 ft screw. The power varied wildly from ship to ship, with Penguin generating only 666 ihp and Pelican managing nearly twice as much, at 1056 ihp. Because of this, top speeds ranged between 10 and 12 knots.

Armament
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.

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

Crew
They had a complement of approximately 140 men.

Development
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.