Alarm-class torpedo gunboat

HMS Jason
Class overview
Name	Alarm class
Builders	Naval Construction & Armament, Barrow Laird Brothers, Birkenhead Devonport Dockyard Sheerness Dockyard Thornycroft, Chiswick
Operators	Royal Navy
Preceded by	Sharpshooter class
Succeeded by	Dryad class
Built	1892–1893
In commission	1893–1924
Completed	11
Lost	3
Scrapped	8
General characteristics
Type	Torpedo gunboat
Displacement	810 long tons (820 t)
Length	242 ft (74 m)
Beam	27 ft (8.2 m)
Draught	12 ft 6 in (3.81 m) maximum
Installed power	3,500 ihp (2,600 kW) except Speedy - 5,000 ihp (3,700 kW)
Propulsion	Twin 3-cylinder vertical triple-expansion steam engines Locomotive boilers Twin screws (except Speedy - water-tube boilers)
Speed	18.7 knots (34.6 km/h; 21.5 mph)
Complement	91
Armament	Jason, Hebe, Circe, Onyx, Leda: 1 × fixed bow 14 in (360 mm) torpedo tube 2 × revolving 14 in torpedo tubes 2 × fixed 14 in torpedo tubes 2 × QF 4.7 in (120 mm) guns 4 × 3-pounder guns 1 × Gardner machine gun Alarm, Jaseur, Niger, Reynard, Speedy, Antelope: 1 × fixed bow 18 in (450 mm) torpedo tube 2 × revolving 18 in torpedo tubes 2 × QF 4.7 in guns 4 × 3-pounder guns 1 × Gardner machine gun

The Alarm-class torpedo gunboat was the penultimate class of torpedo gunboat built for the Royal Navy. The class was contemporary with the early torpedo boat destroyers, which were faster and thus better suited to pursue of enemy torpedo boats. By the First World War, ships of the class had either been sold, converted to submarine depot ships or minesweepers, or reduced to harbour service. Three of the 11 completed torpedo gunboats of the Alarm class were lost during the war while serving in the minesweeping role.

The Alarm class was designed by Sir William White in 1889 as an enlarged version of his previous Sharpshooter class. They had a length overall of 242 feet (74 m), a beam of 27 ft (8.2 m) and a displacement of 810 long tons (820 t). They mounted two sets of vertical triple-expansion steam engines, two locomotive boilers, and twin screws. This layout produced 3,500 indicated horsepower (2,600 kW), giving them a speed of 18.7 knots (34.6 km/h; 21.5 mph) with forced draught. They carried between 100 and 160 tons of coal and were crewed by 91 sailors and officers.

While officially classed with the Alarm class, Speedy was actually a separate design. The Naval Defence Act of 1889 authorised the purchase of an Alarm-class torpedo gunboat built to a design by John I. Thornycroft & Company and built in their yard at Chiswick. Speedy was a three-funnelled vessel (compared to the two-funnelled Admiralty design), but the key difference was the use of water-tube boilers instead of locomotive-type boilers; she produced at least 5,000 indicated horsepower (3,700 kW) and could make 20.5 knots (38.0 km/h; 23.6 mph). The use of water-tube boilers was a key feature of the new torpedo boat destroyers that would make torpedo gunboats (including the Alarm class) obsolete.

At build the class was fitted with two QF 4.7-inch (120 mm)/45-pounder guns, four 3-pounder guns and one Gardner machine gun. Five 14-inch (360 mm) torpedo tubes were fitted in the first five vessels, but this was changed to three 18-inch (450 mm) torpedo tubes in the rest of the class. They were arranged as a pair of revolving deck mounts, a pair of fixed deck mounts (deleted in the later vessels) and a single bow-mounted tube; three reloads were provided.

Wikimedia Commons has media related to Alarm class torpedo gunboat.

• Brown, Les (2023). Royal Navy Torpedo Vessels. Barnsley, UK: Seaforth Publishing. ISBN 978-1-3990-2285-9.
• Colledge, J. J.; Warlow, Ben (2006) [1969]. Ships of the Royal Navy: The Complete Record of all Fighting Ships of the Royal Navy (Rev. ed.). London: Chatham Publishing. ISBN 978-1-86176-281-8.
• 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.