Unprotected cruiser An unprotected cruiser was a type of naval warship in use during the late Victorian or pre - dreadnought era ( about 1880 to 1905 ) . The name was meant to distinguish these ships from “ protected cruiser s ” 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 from penetrating through the ship down into the most critical areas such as machinery , boilers , or ammunition storage . An unprotected cruiser of course 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 ( the same was true of the side armor on some armored cruisers ) . 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 ( with some exceptions in each case ) . Examples . Unprotected cruisers included medium - sized ships such as the Spanish " Reina Cristina " and Chinese " Kai Che " down to smaller ships of about 1000 tons . A small unprotected cruiser was little different from a large gunboat ( for instance , at the Battle of Manila in 1898 the American " Concord " was larger than the Spanish unprotected cruisers of the " Velasco " class , and was equivalent to a small British protected cruiser , however the US navy classified the " Concord " as only a gunboat . ) Such ships could be known by alternate names depending on the preference of each navy , for instance the British navy tended to refer to larger gunboats / small cruisers as “ sloops ” . Although the designation “ unprotected ” only made sense 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 " Castilla " , French " Laperouse " and Dutch " Atjeh " class ships were also to be called unprotected cruisers . Steel - hulled cruisers had been preceded by iron - hulled ( but not armored ) ships and composite ( iron and wood ) - 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 . The cruisers meant for colonial duty , like gunboats , were not built for high speed . The French unprotected cruiser " Milan " ( 1885 ) 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 “ aviso s ” , “ dispatch boat s ” ( if the ship was fast enough to be useful for carrying messages , in the era before wireless ) , or “ torpedo cruisers ” ( a term derived from “ torpedo gunboat s ” , again the distinction being mainly of larger size ) . 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 ( over the pre - dreadnought era , effective armor could be made thinner with less weight due to advances in steelworking technology ) . 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 ( destroyer s ) . When discarded terms such as “ sloop ” , “ frigate ” and “ corvette ” were used again , it was for small anti - submarine convoy escort craft .