Diadem class cruiser encyclopedia topics

Design

The Diadems were designed by Sir William White, and are typical of British design practice of the period, with high freeboard (by the standards of the time) and the use of 'double-decker' casemates, with the hull forward and aft cut away to allow fore and aft fire from the casemate guns. Casemates provided good protection for the guns and allowed a large number of guns to bear on the broadside; however, the lower (main deck) guns were almost unusable in heavy seas.

According to a contemporary (1900) edition of Jane's Fighting Ships:

Hulls were wood sheathed and coppered.
"There are coal bunkers on the lower deck, and above and below the armour deck. The pair of 6 in guns forward and aft are served by one hoist to the pair, each casemate has its own hoist: those to the double casemates being double. The machinery weighs 1630 tons: the boilers occupy a space of about 132 feet (40 m). Working pressure is [300 to 250 lbf/in² (2.1 to 1.7 MPa)].

"The ships are almost absolutely identical in appearance. The Diadem and Andromeda have no steam pipes abaft the first two funnels, while all the others have steam pipes before and abaft each funnel."

History

The Diadem class was intended, like the preceding Powerful class, for trade protection, and were intended to be "capable of dealing with any cruiser existing or building". The Powerfuls had proved costly and demanding in manpower, and the new class had to represent a more economical solution, that could be built and operated in greater numbers. To achieve this, the specification was reduced relative to the Powerfuls: power and speed were reduced from 25,000 ihp (22 knots) to 16,500 ihp (about 20 knots), the thickness of the protective deck reduced from 6 to , and the armament simplified by replacing the single guns fore and aft with pairs of guns, mounted side by side. These changes saved about £100,000 per ship (approximately 15%) relative to the Powerful design.

With eight ships, each of 11,000 tons and costing £600,000, the Diadems were an important class. However, they proved controversial. The naval journalist Fred Jane characterised them as "much-discussed" and complained that "all the weak points of the Powerfuls were exaggerated in them". In particular, contemporary critics raised objections to their indifferent speed, poor manoeuvrability, and lack of heavy guns, and the fact that, while most of the armament was well protected in casemates, the fore and aft pairs of guns, which commanded the greatest fields of fire, were protected only by gunshields.

Although the powerplant used Belleville boilers, which were of the then-new water tube type, most of the ships enjoyed the reputation of good steamers; the exception was Niobe, whose engines gave persistent trouble. The first four ships were troubled by vibration; to remedy this, the engine rooms of the last four was rearranged; the new configuration also provided a increase in power. . All eight ships exceeded their design power on trials (for details, see below); the first four averaged in service, the later four .

In general the Diadems served most of their careers in home waters, although there were some deployments to China Station, the Mediterranean and the Caribbean. Niobe was sold to Canada in 1910. After 1906, they were only occasionally in commission, and by 1914 the class had for the most part been relegated to training ship and depot ship duties. However, with the outbreak of the First World War, several of them were reactivated, initially for patrol duties with the 9th Cruiser Squadron in the Eastern Atlantic. In 1917 Amphitrite and Ariadne were converted into minelayers, for service with the Dover Patrol. Ariadne was the only war loss, being torpedoed by the German submarine UC-65 on 26 July 1917. By the end of the war the survivors had again been withdrawn from active service, and all of them had been sold for scrap by 1932, with the exception of Andromeda, which served as a boys’ training ship until 1956.

Building Programme

Standard British practice at that time was for building costs to exclude armament and stores.

Ship	Builder	Date of			Cost according to
Ship	Builder	Laid Down	Launch	Completion	( BNA 1904 & 1905)	(BNA 1906)
Diadem	Fairfield, Govan	23 Jan 1896	21 Oct 1896	19 July 1898	£582,662	£554,863
Amphitrite	Vickers, Barrow	8 Dec 1896	5 Jan 1898	17 Sep 1901	£575,300	£552,795
Andromeda	Pembroke Dockyard	2 Dec 1895	30 April 1897	5 Sep 1899	£601,356	£574,916
Argonaut	Fairfield, Govan	23 Nov 1896]]	24 Jan align=right \| [[19 April 1900	£573,704	£545,756
Ariadne	J&G Thompson, Clydebank	29 Oct 1896	22 April 1898	5 June 1902	£565,464	£541,927
Europa	J&G Thompson, Clydebank	10 Jan 1896	20 Mar 1897	23 Nov 1899	£589,835	£564,690
Niobe	Vickers, Barrow	16 Dec 1895	20 Feb 1897	6 Dec 1898	£574,878	£548,283
Spartiate	Pembroke Dockyard	10 May 1897	27 Oct 1898	17 Mar 1903	£680,188	£654,661

Trials

Ship	Date	Source
Diadem	1897	Janes 1900
Amphitrite	1900	Janes 1900
Andromeda	1898	Janes 1900
Argonaut	1899	Janes 1900
Ariadne	1899	Janes 1900
Europa	1898	Janes 1900
Niobe	1898	Janes 1900
Spartiate

The Diadem (Dec 1898) did a mean of in a 69 hour run from Gibraltar to the Nore with 14,268 horsepower (10.64 MW). For 60 hours with 24 boilers with 12,791 ihp (9.538 MW), she made on trial. Andromeda did a sea trip at = .

References

Brown, David K. Warrior to Dreadnought: Warship Development 1860-1905. Caxton Editions 2003. ISBN 1-84067-529-2
Chesnau, Roger and Kolesnik, Eugene (Ed.) Conway's All the World's Fighting Ships, 1860-1905. Conway Maritime Press, 1979. ISBN 0-83170-302-4
Robert Gardiner (Ed.). Conway’s All the World’s Fighting Ships, 1906-1921. Conway Maritime Press, 1985. ISBN 0-85177-245-5
worldwar1.co.uk
Jane, Fred T (Ed.) Jane's Fighting Ships 1900
Jane, Fred T (Ed. Preston, Anthony). The British Battle-Fleet: Its Inception and Growth throughout the Centuries. Republished by Conway Maritime Press, 1997. ISBN 0-85177-723-6.
Brassey, T.A. (ed) The Naval Annual 1904
Brassey, T.A. (ed) The Naval Annual 1905
Leyland, J. and Brassey, T.A. (ed) The Naval Annual 1906
Hythe, Viscount and Leyland, J. (ed) The Naval Annual 1914