 The 35 cm guns were of course heavier than the 30 @.@ 5 cm guns , but there were problems with enlarging the new ships to accommodate the heavier armament . The Imperial dry docks were deep enough only for ships with a draft of 9 m ( 30 ft ) , and simply accepting an increased displacement on the same hull as the Derfflinger class would entail a reduction in speed . This meant that an increase in displacement would necessitate a longer and wider hull to keep any increases in draft minimal and avoid reducing the speed . The constraints on enlarging the hull were compounded by restrictions on width imposed by the locks of the canal in Wilhelmshaven . As a result , Großadmiral ( Grand Admiral ) Alfred von Tirpitz , the head of the RMA , prohibited a design displacement greater than 30 @,@ 000 metric tons ( 29 @,@ 526 long tons ) . 
