The class was a group of six coastal defense ships built by the German ("Imperial Navy") in the late 19th century. The ships were intended to protect the German coastline from naval attacks. The class comprised the lead ship , along with her sisters , , , , and . All six ships were named after Norse mythological figures. Two further vessels, the , were built to a similar design but were not identical.
The -class ships were obsolete by the outbreak of World War I, and saw only limited service in their intended role before they were withdrawn from active duty. The ships then served in a variety of secondary duties, including barracks ships, target ships, and in the case of , an icebreaker in the Baltic Sea. All six ships were struck from the naval register on 17 June 1919, days before the Treaty of Versailles was signed. Five of the ships were sold for scrapping immediately after they were struck from the register (with being lost in transit), but was purchased by a shipping company, and converted into a freighter. She served in this capacity until she too was scrapped in 1930.
Design
In the late 1880s, the German grappled with the problem of what type of capital ship to build in the face of limited naval budgets (owing to parliamentary objections to naval spending and the cost of dredging the Kaiser Wilhelm Canal). General Leo von Caprivi, the new (Chief of the Admiralty), requested a series of design proposals, which ranged in size from small coastal defense ships armed with a battery of two guns to heavily armed ocean-going battleships equipped with seven guns. Caprivi ordered ten coastal defense ships to guard the entrances to the canal, since even opponents of the navy in the (Imperial Diet) agreed that such vessels were necessary.
The first six of these, the class, were based on the smallest proposal, though they were scaled up to add a third main battery gun, the caliber of which was increased from 21 cm to . Two of these guns were carried in open barbettes side-by-side forward, as German naval theorists still favored ramming attacks that required a capability for end-on fire. The ships were to carry a secondary battery of six Hotchkiss revolver cannon for defense against torpedo boats, but tests conducted at the firing range at Meppen revealed that the guns were insufficient against modern vessels. As a result, the battery was increased to eight guns.
General characteristics
The ships of the class were long at the waterline and long overall. The ships had a beam of and a draft of between forward and aft. All six ships were heavily rebuilt, each undergoing refits at various times between 1898 and 1904. During the rebuilding, the ships were lengthened, to at the waterline and overall. The ships' beams remained the same, but their draft was slightly decreased, to forward and aft. The ships had a designed displacement of , and a maximum displacement of . After the reconstruction, the displacement was increased to between , depending on the ship.
The ships used transverse and longitudinal steel frames in the hull. They had eight watertight compartments and a double bottom that ran for 60% of the hull. After the refits, one more watertight compartment was added. The ships were described as good sea boats; they had gentle motion and were very responsive to commands from the helm. The ships lost significant speed in heavy seas, however. The ships had a crew of 20 officers and 256 enlisted men, with an additional 6 officers and 22 men when serving as a flagship. The refit increased crew requirements, to an additional 31 sailors normally, and the extra flagship crew increased to 9 officers and 34 men. The ships carried a number of smaller boats, including one picket boat, one pinnace, two cutters, one yawl, and one dinghy.
Propulsion
The ships were powered by two sets of 3-cylinder triple-expansion engines, each in its own engine room. This was the first use of triple-expansion machinery in a major German warship. These engines drove a pair of three-bladed screws that were in diameter. The ships had eight marine type boilers, with the exception of , which was equipped with eight Thornycroft boilers. The ships had similar maximum speeds, with the fastest at and the slowest at . Each ship had three electric generators that provided between 29–26 kilowatts at 67 volts.