 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).
