|Operators:|| Royal Navy|
|Preceded by:||Danae class|
|Succeeded by:||Leander class|
|In commission:||1926 - 1948|
|Displacement:||7,580 tons standard
9,435 tons full
|Length:||570 ft (173.7 m)|
|Beam:||54.5 ft (16.6 m)|
|Draught:||16.5 ft (5.0 m)|
|Installed power:||80,000 shp (59.6 MW)|
|Propulsion:||Eight Yarrow-type water-tube boilersFour shaft Brown-Curtis single-reduction geared turbines6 boilers|
|Speed:||33 knots (61 km/h)|
|Range:||1,350 nautical miles at 32 knots (59 km/h)
8,000 nautical miles at 15 knots (15,000 km at 28 km/h); 1,746 tons fuel oil
|Aircraft carried:||1 × aircraft (later removed)|
|Aviation facilities:||1 × catapult (later removed)|
The Emerald class or E class was a class of two light cruisers built for the Royal Navy. Following the Cavendish class, three ships of a new class were ordered in March 1918, towards the end of World War I, designed to emphasise high speed at the cost of other qualities, for use against rumoured new high speed German cruisers - like the Brummer class - and particularly minelayers, in the North Sea. However, the third ship was cancelled in November 1918.
The E class were based on the preceding Danae class, but had a very high ratio of length to beam, and only one more gun despite being much bigger and more expensive. Much was sacrificed to achieve 33 knots (61 km/h), the horsepower was doubled and the hull increased by 100 ft (30 m) in length, and a 50% increase in displacement. Only two ships were actually built, and completed in 1926. Four propellers were necessary for the increased power, and were driven from two engine rooms. There were four boiler rooms, nos. 2 and 3 being arranged side-by-side with the exhausts trunked into a common funnel. The magazines were between boiler rooms nos. 2 and 3 and the forward engine room, and between boiler room no. 4 and the after engine room. This led to a bizarre funnel arrangement, accentuated further when in 1935 a longer catapult required the mainmast to be stepped forward of the after funnel, and the funnels were heightened by 5 ft (1.5 m).
In the early 1930s Enterprise was fitted with a prototype twin 6" turret in place of her two forward single mounts; and with trials of the turret proving successful it was retained on Enterprise for the rest of her career. The turret design was later installed in the Leander, Amphion and Arethusa classes. The turret installation occupied less space than the superimposed 'A' and 'B' guns of Emerald, therefore the bridge was placed further forward. The bridge was of a new design, being a single block topped by a director tower, rather than the traditional platforms built around the foremast and wheelhouse topped with a spotting top. This design of bridge would appear in the County-class cruisers.
Nothwithstanding their age and outlandish appearance these two ships were still the fastest cruisers in the Royal Navy at the outbreak of World War II, Emerald exceeding 32 knots (59 km/h) in a full-power trial at full load in 1939.
Hawker Osprey K5749 on Enterprise's catapult in May 1936In the mid-1930s both ships were fitted with a catapult which replaced the out-moded flying-off platform and had HACS Mk.I added for the 4 in guns, which was fitted amidships between the searchlight platform and the after funnel. The funnels were raised 5 ft (1.5 m) at this time. Later proposals to increase the AA outfit by the addition of twin 4 in and multiple 2 pdrs were thwarted by the outbreak of war. Emerald had received two quadruple .5 machine guns before the war, then during refit between August 1942 and April 1943 she landed the after 6 in, two 2 pdr singles and the .5 machine guns to receive instead six power-operated twin 20 mm, two quadruple 2 pdr and radars Type 273 (centimetric target indication), 281 (air warning), 282 (pom-pom ranging) and 285 (HACS ranging). In April 1944 six 20 mm singles were added and the catapult was removed.
Enterprise landed two 6 in singles in 1941 and had one quadruple 2 pdr fitted. She later had four single 20 mm fitted and then, in the course of a long refit between the end of December 1942 and October 1943, she lost the single 2 pdr and 20 mm weapons, receiving six twin power-operated mountings in lieu. The two 6 in were reinstated and a second quadruple 2 pdr fitted. She was fitted with radars Type 272 (centimetric target indication), 281, 282, 284 (6 inch gun ranging), and 285. In February she had an additional four single 20 mm fitted and the catapult was removed.
- Emerald, built by Sir W. G. Armstrong, Whitworth and Company, Elswick, laid down 23 September 1918, launched 19 May 1920, and completed at Chatham Royal Dockyard in January 1926. Sold for breaking up 23 June 1948.
- Enterprise, built by John Brown and Company, Clydebank, laid down 28 June 1918, launched 23 December 1919, and completed at Devonport Royal Dockyard in April 1926. Sold for breaking up 11 April 1946.
- Euphrates, ordered from Fairfield Shipbuilding and Engineering Company, Govan, laid down 1918, but cancelled 26 November 1918.
- British and Empire Warships of the Second World War, H T Lenton, Greenhill Books, ISBN 1-85367-277-7
- Conway's All the World's Fighting Ships, 1922-1946, Ed. Robert Gardiner, Naval Institute Press, ISBN 0-87021-913-8
- Colledge, J. J.; Warlow, Ben (2006) . 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. OCLC 67375475.
- Jane's Fighting Ships of World War One (1919), Jane's Publishing Company
- Emerald class at U-boat.net