Diadem-class cruiser
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| Class overview | |
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| Name: | Diadem class |
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| Preceded by: | Powerful class |
| Succeeded by: | Cressy class |
| Completed: | 8 |
| General characteristics | |
| Type: | Protected cruiser |
| Displacement: | 11,000 tons |
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| Beam: | 69 ft (21.0 m) |
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| Complement: | 677 |
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The Diadem-class cruiser was a class of "first class" protected cruiser built for the Royal Navy during the 1890s that served in the First World War. The class consisted of eight ships, built at a cost of around £600,000 each.
They were considered "good sea boats" but criticised for their lack of a heavy calibre main armament, bulky unprotected sides, average speed and lack of manoeuvrability despite being considered large ships when completed. They were the last British first class protected cruisers; the armoured cruiser taking the large cruiser role in future."
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 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 the hulls were wood sheathed and coppered. and "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 psi (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."
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 indicated horsepower (19,000 kW) (22 knots (41 km/h; 25 mph)) to 16,500 ihp (12,300 kW) (about 20 kn (37 km/h; 23 mph)), the thickness of the protective deck reduced from 6 inches (150 mm) to 4 inches (100 mm), and the armament simplified by replacing the single 9.2-inch (234 mm) guns fore and aft with pairs of 6-inch (152 mm) guns, mounted side by side. These changes saved about £100,000 per ship (approximately 15%) relative to the Powerful design.
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Wikipedia