The following was excerpted from https://en.wikipedia.org/wiki/Maximum_battleship
The "maximum battleships"
, also known as the "Tillman Battleships"
were a series of World War I-era design studies for extremely large battleships, prepared in late 1916 and early 1917 to the order of Senator "Pitchfork"
Benjamin Tillman by the Bureau of Construction and Repair (C&R) of the United States Navy. The navy was not interested in the designs and drew them up to win support from the Committee on Naval Affairs, on which Tillman sat. Nevertheless, they helped influence design work on the Pennsylvania
and first South Dakota classes
of battleships. The plans prepared for the senator were preserved by C&R in the first of its "Spring Styles"
books, where it kept various warship designs conceptualized between 1911 and 1925.
Senator Tillman had grown impatient with the navy's requests for larger battleships every year as well as the navy's habit of building battleships significantly larger than Congress authorized. He accordingly instructed the navy to design "maximum battleships"
, the largest battleships that they could use.
The only limits on the potential size of an American battleship were the dimensions of the locks of the Panama Canal. The locks measure roughly 1,000 by 110 feet (305 m × 34 m), and so the "maximum battleships"
were 975 by 108 feet (297 m × 33 m). Draft was limited to 39 feet 6 inches (12.04 m).
Tillman's first request, in 1912–1913, was never completed, and though the studies it involved had some influence on the design of the Pennsylvania class
of battleships, that class was essentially just an enlargement of the preceding Nevada class. In 1916, he repeated his request, and this time the Bureau of Construction and Repair produced a series of design studies, which again had some influence on the design of the next class of battleships, in this case the South Dakotas
, an enlargement of the previous Colorado class
After the first four design studies were complete, Design IV was chosen for further development and three additional studies, IV-1, IV-2, and IV-3, were prepared. At the request of Secretary of the Navy Josephus Daniels, these designs used 18-inch (460 mm) guns instead of the 16-inch (410 mm) 50-caliber guns used in the earlier studies. The navy decided that design IV-2 was the most practical (or perhaps the least impractical) and presented it to Congress early in 1917.
These designs differed from the battleships being built in two significant ways beyond just their size. Firstly, unlike preceding classes, the "maximum battleships"
were designed with a continuous flush main deck. Most battleships in this era had a long forecastle deck. Secondly, the Tillman designs all included five casemate guns mounted aft, two on each side and one at the tip of the stern. Similar "stern chasers"
had been previously mounted in Nevadas
, but were omitted from the Pennsylvania class
. These casemates were a return to an older design idea; American battleship designers had abandoned hull-mounted casemates after the New Mexico class. They had transpired to be too "wet" – heavy seas rendered them unusable—and they had been removed from all earlier classes. However, the casemates on the "maximum battleships" would have been higher above the waterline than they had been on earlier designs, so it is possible that their huge size and flush decks would have provided enough freeboard astern to keep the casemates dry.
The Washington Naval Treaty of 1922
limited naval armaments, causing the cancellation of the South Dakotas
and halting all consideration of the "maximum battleships."
Here is the Design Study IV-2 of the Tillman Maximum Battleship
Here is the same drawing sans 6" pedestal mounts on the 0-1 deck: