An unprotected cruiser was a type of naval warship in use during the late Victorian or pre-dreadnought era. The name was meant to distinguish these ships from “protected cruisers” which had become accepted in the 1880s. A protected cruiser did not have side armor on its hull like a battleship or “armored cruiser” but had only a curved armored deck built inside the ship – like an internal turtle shell – which prevented enemy fire penetrating through the ship down into the most critical areas such as machinery, boilers, and ammunition storage. An unprotected cruiser lacked even this level of internal protection. The definitions had some gray areas because individual ships could be built with a protective deck that did not cover more than a small area of the ship, or was so thin as to be of little value. An unprotected cruiser was generally cheaper and less effective than a protected cruiser, while a protected cruiser was generally cheaper and less effective than an armored cruiser.
Examples
Unprotected cruisers included medium-sized ships such as the Spanish and Chinese Kai Che down to smaller ships of about 1,000 tons. A small unprotected cruiser was little different from a large gunboat Such ships could be known by alternate names depending on the preference of each navy. For instance, the British Royal Navy tended to refer to larger gunboats/small cruisers as “sloops”. The designation “unprotected” made sense only after the development of protected cruisers in the 1880s. Many ships designed earlier had essentially the same features and size range; for instance, the Spanish, the French and the Dutch ships were also to be called unprotected cruisers. Steel-hulled cruisers had been preceded by iron-hulled ships and composite -hulled ships, which were originally termed cruisers, frigates, or corvettes. Most of these ships retained sailing rig and were useful for colonial duties, where dockyards and coal supplies were often inadequate. Some of these older ships were fairly large, for instance. The cruisers meant for colonial duty, like gunboats, were not built for high speed. The French unprotected cruiser Milan was distinct in appearance and role, with the recognition that cruisers were more useful as scouts and commerce raiders if they were faster than ironclad battleships. In the 1880s and 1890s fast, small unarmored cruisers could also be listed as “avisos”, “dispatch boats”, or “torpedo cruisers”. Different contemporary reference works may use more than one of these terms for the same ship.
Decline
All of these terms faded from use because the design of these ships became obsolete. By World War I, there was no need to produce unprotected cruisers since fast “light” cruisers could be given not only protective decks but side armor. The speed and firepower difference between even a small light cruiser and a gunboat had made these categories permanently distinct. Wireless technology had eliminated message-carrying roles, and specialized torpedo craft were made much lighter and faster. When discarded terms such as “sloop”, “frigate” and “corvette” were used again, it was for small anti-submarine convoy escort craft.
