L 20 α - class battleship L 20 α was a design plan for a class of battleship s to be built in 1918 for the Kaiserliche Marine during World War I . The design was selected on 2 October 1917 , and construction was to have started 11 September 1918 . The ships would have been significantly larger than the preceding s , at 238 m ( 781 ft ) long , compared to 180 m ( 590 ft ) for the preceding ships . The ships would have been the first German warship to have mounted guns larger than 40 . 6 cm ( 16 in ) . However , Germany ' s declining war situation and the transfer of emphasis within the Navy from capital ships to submarines meant that the ships would never be constructed . Design . In January 1916 , Vice Admiral Reinhard Scheer became commander in chief of the High Seas Fleet . Following the Battle of Jutland on 31 May – 1 June 1916 , Scheer pushed for new , more powerful battleships . He demanded the new ships have guns of 42 cm ( 16 . 5 in ) caliber , an armored belt thick , and be capable of speeds of up to , all on a displacement of up to . The new 42 cm gun was designed by 29 December 1916 , and was approved on 11 September 1918 , though none were actually built . After the outbreak of unrestricted submarine warfare in February 1917 , Admiral von Capelle argued that capital ship construction should not be halted in favor of U - boat construction . On 21 August 1917 , the construction department submitted two design proposals for the new battleship class , L 20 and L 24 . The primary difference was the placement of the ships ' torpedo armament . The L 20 design placed them in the hull below the waterline , while the L 24 proposal used above - water launchers . Displacement for the designs was fixed at . Both ships also had a top speed of only , which was unacceptable to Scheer . During the design process , it was decided that the utmost concern was that the ships could be built quickly and placed into service . The ships were to discard the use of broadside belt armor below the waterline , the attachment of which was an extremely long process . It was believed that the higher speed of the class — — would make up for the vulnerability to torpedo attack and make the armor unnecessary . The initial designs called for three main battery turrets , each mounting a pair of new 42 cm ( 16 . 5 inch ) guns , though this was later increased to four twin turrets . However , the work that would have been necessary to design and test the new turret clashed with U - boat construction , which had become the priority of the Navy . Krupp , the firm that had been awarded the contract to conduct the testing , informed the " Reichsmarineamt " ( RMA — the Imperial Navy Office ) that design work on the new turret would have to wait . Capelle accepted the news without much objection . The RMA filed a report dated 1 February 1918 , which stated that capital ship construction had ground to a halt , primarily due to the shifting priorities to the U - boat war . Armament . The main battery was arranged in four twin turrets , as in the preceding , in a superfiring arrangement on the centerline . The aft pair of turrets were separated by engine rooms . The four turrets mounted two 42 cm ( 16 . 5 in ) SK L / 45 guns , for a total of eight guns on the broadside . The 42 cm gun fired a shell out to at the maximum elevation of 30 degrees . The estimated muzzle velocity was The ships were to have been armed with a secondary battery of twelve 15 cm ( 5 . 9 in ) guns mounted in casemate s . The anti - aircraft battery was to have consisted of either eight 8 . 8 cm ( 3 . 45 in ) Flak L / 45 guns or eight 10 . 5 cm ( 4 . 1 in ) Flak L / 45 guns . The design was to have been equipped with three submerged torpedo tubes , either 60 cm ( 23 . 6 cm ) or 70 cm ( 27 . 6 in ) in diameter . One tube was placed in the bow , the other two on either beam to the rear of the engine rooms . Armor . The ships had a armored belt , and ran from slightly forward of the fore barbette to slightly aft of the fourth barbette . The belt began 35 cm below the waterline to above it . Directly above the main belt was a strake of armor plating that was thick . This section of side armor extended up to the upper deck . The ships ' armored deck was to have been thick forward , increased to amidships , and aft . The ships were also to have had a forecastle deck that was thick . The ships were also protected by a torpedo bulkhead that was 50 – 60 mm thick . A sloped thick splinter bulkhead , designed to protect against shell fragments , extended from the top of the torpedo bulkhead up to the upper deck . The barbettes were also 350 mm thick on the front and sides , but decreased to 250 mm on the rear . The main gun turrets had 350 mm faces , 250 mm sides , rears , and roofs . The secondary guns were protected with of armor plate . Machinery and other characteristics . The ships were to have been powered by either 2 or 4 sets of steam turbines driving 4 shafts . The steam plant consisted of 6 oil - fired and 16 coal - fired boilers trunked into a single funnel . Bunkerage was of coal and of fuel oil . The ships were intended to have a single tripod foremast , as was typical for German battleships of the period . Externally , the ships were very similar to the s .