Protected cruiser

A schematic section of a protected cruiser illustrating the protection scheme. Red lines are the armoured deck and gun shield and grey areas are the protective coal bunkers. Note the deck is thickest on the slopes, that the upper coal bunker is divided longitudinally to allow the outer layer of coal to be maintained while the inner bunker is emptied and the watertight double-bottom.

Protected cruisers were a type of naval cruiser of the late 19th century, so known because their deck armour offered protection for vital machine spaces from shrapnel caused by exploding shells above. They were less well protected than armoured cruisers which also had a belt of armour along the sides.[1]

While the armoured cruiser evolved into the battlecruiser (and while pre-dreadnought battleships were replaced by dreadnoughts), the protected cruiser is considered the forerunner of the light cruiser and heavy cruiser types.

Contents

Design features

After the introduction of the explosive shell, warships needed additional protection, and protected cruisers were constructed from about 1880.

In a protected cruiser, the armour was arranged on their decks inside the vessel, protecting the boilers and steam engines.

Typically protected cruisers displaced from 2,500 to 7,000 tons, and were armed with up to a dozen single guns of between 3.9 and 6 inches (100 to 152 mm) in calibre. They were capable of speeds of 18 - 23 knots.

The first protected cruiser was the groundbreaking Chilean ship Esmeralda. Produced by a shipyard at Elswick, in Britain, owned by Armstrong, she inspired a group of protected cruisers produced in the same yard and known as the Elswick cruisers. Her forecastle, poop deck and the wooden board deck had been removed, replaced with an armoured deck. Esmeralda 's armament consisted of fore and aft 10-inch (25.4 cm) guns and 6-inch (15.2 cm) guns in the midships positions. It could reach a speed of 18 knots (33 km/h), and was propelled by steam alone. It also had a displacement of less than 3,000 tons. During the two following decades, this cruiser type came to be the inspiration for combining heavy artillery, high speed and low displacement. (Perhaps surprisingly, the Royal Navy itself did not possess any Elswick cruiser, preferring either very large and heavily-armed "first-class" cruisers, or lightly-armed "second-" or "third-class" cruisers designed for trade protection duties.)

Around 1910, armour plate began to increase in quality and steam turbine engines, lighter and more powerful than previous reciprocating engines. came into use. Existing protected cruisers became obsolescent as they were slower and less well protected than new ships. Oil firing of boilers was introduced, making side bunkers of coal unnecessary and losing the protection they afforded. Protected cruisers were replaced by "light armoured cruisers" with a side armoured belt and armoured decks instead of the single deck, later developed into heavy cruisers.

Protected cruisers in the United States Navy

The first protected cruiser of the United States Navy "New Navy" was the USS Atlanta,[2] launched in October 1884, soon followed by the Boston in December, and Chicago a year later. A numbered series of cruisers began with Newark (Cruiser No. 1), although Charleston (Cruiser No. 2) was the first to be launched, in July 1888, and ending with another Charleston, Cruiser No. 22, launched in 1904. The last survivor of this series is the USS Olympia (C-6), preserved as a museum ship in Philadelphia.

The reclassification of 17 July 1920 put an end to the US usage of the term "protected cruiser", the existing ships designated as plain "cruisers" with new numbers (so that the armored cruisers could retain their numbers unchanged).[2]

Protected cruisers in the Royal Navy

The British Royal Navy rated cruisers as first, second and third class between the late 1880s and 1905, and built large numbers of them for that navy's trade protection requirements. For the majority of this time, such cruisers were built with a "protected," rather than armoured scheme of protection for their hulls. First class protected cruisers were as large and as well-armed as armoured cruisers, and were built as an alternative to the large first class armoured cruiser from the late 1880s till 1898. Second class protected cruisers were smaller, displacing 3,000-5,500 tons and were of value both in trade protection duties and scouting with the fleet. Third class cruisers were smaller, lacked a watertight double bottom, and were intended primarily for trade protection duties, though a few small cruisers were built for fleet scout roles or as "torpedo" cruisers during the "protected" era.

The introduction of Krupp armour in six inch thickness rendered the "armoured" protection scheme more effective for the largest first class cruisers, and no large first class protected cruisers were built after 1898. The smaller cruisers, unable to bear the weight of heavy armoured belts retained the "protected" scheme up to 1905, when the last units of the Challenger and Highflyer class were completed. There was a general hiatus in British cruiser production after this time, apart from a few classes of small, fast scout cruisers for fleet duties. When the Royal Navy began building larger cruisers (+4000 tons) again around 1910, they used a mix of armoured decks and/or armoured belts for protection, depending on class. These modern, turbine powered cruisers are properly classified as light cruisers.

Footnotes

  1. ↑ protected cruiser (warship) from the Encyclopædia Britannica. Protected cruisers had steel armour plating only on their decks, while armoured cruisers also had armour extending down the sides of the hull.
  2. ↑ 2.0 2.1 Early American cruisers from the Naval Historical Center. Excluding the larger armored cruiser type, these warships were "protected cruisers", with a steel armored deck covering machinery and ammunition magazines.

Surviving examples

A few protected cruisers have survived as museum ships:

See also