Armored Cruiser - 1880s: Rise of The Protected Cruiser

1880s: Rise of The Protected Cruiser

During the 1870s, the rapid increase in the size and power of armor-piercing guns caused problems for the designers of battleships and cruisers alike. Even a ship designed with adequate armor protection from the current generation of guns might technically be vulnerable to new guns powerful enough to penetrate its armor. Consequently, naval designers tried a novel method of armoring their ships. The vital parts—engines, boilers, magazines and enough hull structure to keep the ship stable in the event of damage—could be positioned underneath an armored deck just below the waterline. This deck, which would only be struck very obliquely by shells, could be thinner and lighter than belt armor. The sides of the ship would be entirely unarmored but would be as effective as an armored belt which would not stop shellfire. Cruisers designed along these guidelines, known as protected cruisers, superseded armored cruisers in the 1880s and early 1890s.

As mentioned earlier, the armored cruiser Shannon was the first ship to make use of an armored deck. However, by the end of the 1870s, ships could be found with full–length armored decks and little or no side armor. The Italian Italia class of very fast battleships had armored decks and guns but no side armor. The British used a full-length armored deck in their Comus class of corvettes started in 1878; however the Comus class were designed for colonial service and were only capable of 13 knots speed, not fast enough for commerce protection or fleet duties.

The breakthrough for the protected cruiser design came with the Chilean Esmeralda, designed and built by the British firm Armstrong at their Elswick yard. Esmeralda, with a high speed of 18 knots, dispensed entirely with sails and carried an armament of two 10in and six 6in guns, considered very powerful for a ship her size. Her protection scheme, inspired by the Italia class, included a full–length protected deck up to 2in thick, and a cork-filled cofferdam along her sides. Esmeralda set the tone for cruiser construction for the years to come, with "Elswick cruisers" on a similar design being constructed for Italy, China, Japan, Argentina, Austria and the United States. Protected cruisers became attractive for two reasons. First, the concept of the armored cruiser was not embraced wholeheartedly in naval circles. Second, several navies were caught in a race between armor thickness and the size of main guns and did not have the money to spend on battleships and armored cruisers. The use of smaller, lighter cruisers was an affordable alternative.

The French navy adopted the protected cruiser wholeheartedly in the 1880s. The Jeune Ecole school of thought, which proposed a navy composed of fast cruisers for commerce raiding and torpedo-boats for coast defense, was particularly influential in France. The first French protected cruiser was the Sfax, laid down in 1882, and followed by six classes of protected cruiser – and no armored cruisers until the Dupuy de Lôme, laid down in 1888 but not finished until 1895. Dupuy de Lôme was a revolutionary ship, being the first French armored cruiser to dispose entirely of masts, and sheathed in steel armor. However, she and two other were not sufficiently seaworthy, and their armor could be penetrated by modern quick-firing guns. Thus from 1891–7 the French reverted to the construction of protected cruisers.

The British Royal Navy was equivocal about which protection scheme to use until 1887. The large Imperieuse class, begun in 1881 and finished in 1886, were built as armored cruisers but were often referred to as protected cruisers. While they carried an armored belt some 10 in thick, the belt only covered a 140 ft of the 315 ft length of the ship, and was submerged below the waterline at full load. The real protection of the class came from the armored deck 4 in thick, and the arrangement of coal bunkers to prevent flooding. These ships were also the last armored cruisers to be designed with sails. However, on trials it became clear that the masts and sails did more harm than good; they were removed and replaced by a single military mast with machine guns.

The next class of small cruisers in the Royal Navy, the Mersey class, were protected cruisers, but the Royal Navy then returned to the armored cruiser with the Orlando class, begun in 1885 and completed in 1889. The navy judged the Orlandos inferior to protected cruisers and built exclusively protected cruisers immediately afterwards, including some very large, fast ships like the 14,000-ton Powerful class. However, the Orlandos were the first class of cruiser to use the triple expansion engine. Because this type of reciprocating engine produced steam in three stages, it was more fuel-efficient than earlier compound engines. It also produced steam at higher pressure, 60 pounds per square inch, as compared to the 25 to 30 pounds in earlier engines. With these engineering developments, warships could now dispense with sails and be entirely steam-driven.

The only major naval power to retain a preference for armored cruisers during the 1880s was Russia. The Russian Navy laid down four armored cruisers and one protected cruiser during the decade, all being large ships with sails.