Humber-class monitor

HMS Severn off East Africa, 1917
Class overview
Name:	Humber class
Builders:	Vickers, Barrow in Furness
Operators:	Royal Navy  Brazilian Navy (intended)
Cost:	£155,000 (equivalent to £12.5MM in 2008)
In service:	1914-1920
Completed:	3
Retired:	3
General characteristics
Type:	Monitor
Displacement:	1,260 long tons (1,280 t) standard 1,520 long tons (1,540 t) full load
Length:	266.75 ft (81.3 m)
Beam:	49 ft (14.9 m)
Draught:	5.6 ft (1.7 m)
Propulsion:	2 shaft triple expansion engines 2 Yarrow boilers 1,450 ihp (1,080 kW)
Speed:	12 knots (22 km/h) designed, 9.5 knots (18 km/h) in practice
Range:	1,650 nautical miles (3,060 km) at 8 knots (15 km/h)
Armament:	2 × 6-inch (152 mm) guns in one twin turret 2 × 4.7-inch (119 mm) howitzers 4 × 3-pounder (47mm) guns 1 × 3-pounder (47mm) AA gun 6 × machine guns
Armour:	Belt: 3–1.5 in (76–38 mm) Bulkheads: 1.5 in (38 mm) Barbette: 3.5 in (89 mm) Turret face: 4 in (100 mm)
Notes:	Mersey and Severn had a turret replaced by two single 6-inch guns in open shielded mountings, Humber had an extra 6-inch gun fitted aft retaining turret

The Humber-class monitors were three large gunboats under construction for the Brazilian Navy in Britain in 1913. Designed for service on the Amazon River, the ships were of shallow draft and heavy armament and were ideally suited to inshore, riverine and coastal work but unsuitable for service at sea, where their weight and light draft reduced their speed from a projected twelve knots to under four. The class comprised Humber, Mersey and Severn. All three were taken over by the Royal Navy shortly before the outbreak of the First World War and were commissioned as small monitors. All three saw extensive service during the war and were sold in 1919.

The three Humber-class monitors were originally ordered for the Brazilian Navy as the Javary-class gunboats intended for inshore work on the River Amazon and its tributaries. Ordered from the Vickers Limited shipyard at Barrow -in - Furness, the three ships were launched by 1913 and were undergoing sea trials when the Brazilian government informed Vickers that they would not be able to pay for the warships. Vickers attempted to find a foreign buyer for the boats and the British government stepped in to purchase the gunboats on 4 August 1914 for ₤155,000 each in order to prevent them being bought by a neutral navy and then sold on to Germany.

The ships were stationed at Dover for service in the English Channel, attached to the Dover Monitor Squadron. During the Battle of the Frontiers and subsequent operations in 1914, the Humber-class monitors were all employed in bombarding German batteries and positions, under the command of Rear-Admiral Horace Hood.

Severn and Mersey's guns soon wore out, and they were each re-armed with a single 6-inch Mk VII gun stripped from the wreck of Montagu, a battleship which had been wrecked on the Isle of Lundy in 1906. Humber retained her twin gun turret throughout the war, with guns being replaced by refurbished guns removed from the other two ships as needed.