America Class Battlecruiser

## Backround

### Armor or Speed

As early as 1903, questions arose in the Naval War College (NWC) about the overall effectiveness of large armored cruisers such as the *Pennsylvania*- and *Tennessee*-class vessels just then coming into service. The NWC's 1903 annual summer conference report, which included a staff memorandum on all-big-gun capital ships, also suggested a new type of cruiser that would be armed and armored much like a battleship. The following year, the summer conference considered tactics for a ship armed with four 12-inch (305 mm), twenty-two 3-inch (76 mm) guns, four submerged torpedo tubes and battleship-type protection. Ships such as these were essentially *Tennessee*-class ships in which the 6-inch (150 mm) intermediate battery had been traded for heavier main guns and protection. These ships figured in the college's studies for several years, and its 1906 summer conference report on a US building program strongly advocated the ships' construction for use in scouting and as fast wings in a fleet action, and for their resistance to 12-inch gunfire (much greater than the *Tennessee* class). Although the General Board and the Secretary of the Navy refused to adopt the proposed new armored cruiser, perhaps because the Navy already had 10 new armored cruisers on hand, the college continued to test the design against a variety of foreign vessels, including the British *Invincible*-class battlecruiser.

By 1908, the summer conference had come to favor battlecruisers over armored cruisers. The increasing range of torpedoes and the distances at which future gun battles were expected to be fought seemed to favor speed over armor. Gunnery officers "laid great stress upon the value of getting the range first and then smothering, or beating down, the enemy's fire before he gets the range." The conference concluded that battlecruisers would be worth building, with the caveat that they be considered in the same category as armored cruisers, in support of the battle fleet but not to fight in the line with fully armored battleships. A majority report recommended a top speed of at least 20 percent above that of battleships. As U.S. battleships then being built were expected to steam at 21 knots (39 km/h; 24 mph), this meant a minimum speed for battlecruisers of 25.4 knots (47.0 km/h; 29.2 mph). The Bureau of Construction and Repair (C&R) sketched out such ships the following year, at the request of the Secretary of the Navy, as fast equivalents of the *Wyoming*-class ships being considered. By adopting a 670-foot (204 m) hull on a displacement of 26,000 long tons (26,417 t), it could produce a vessel that could travel at 25.5 knots (47.2 km/h; 29.3 mph) and carry eight 50-caliber 12-inch guns in four twin turrets and equivalent armor; the savings in weight from eliminating two of the *Wyoming*s' six turrets more than balanced the added length and height of the armor belt. An enlarged belt was required by a deeper hull, as all American battlecruiser studies required deep hulls to retain their girder strength because those hulls had to be abnormally long to attain their speed. If the armor belt were reduced by an average of three inches, a fifth turret could be added. Four intermediate proposals included one with intermediate armor and eight 12-inch guns and one with *Wyoming* armor and six 14-inch guns. Most of these designs did not include superfiring turrets with the execption of Design H. The General Board retained these sketches with Design H eventually turning into the John Paul Jones Class.

### Pacific Developments

As the NWC continued its studies, the Imperial Japanese Navy (IJN) annihilated the Russian Baltic Fleet at the Battle of Tsushima in 1905. Japan had already been a concern of the U.S. Navy. Strategist and Admiral Alfred Thayer Mahan had warned then-Assistant Secretary of the Navy Theodore Roosevelt in 1897 of a much greater likelihood of conflict in the Pacific than in the Atlantic. Roosevelt himself, as President of the United States, had written before Tsushima to British diplomat Cecil Spring Rice, "The Japs interest me and I like them. I am perfectly well aware that if they win out it may possibly mean a struggle between them and us in the future." Tsushima sealed the outcome of the Russo-Japanese War in Japan's favor, signaled its emergence as a world power and began a period of rivalry with the United States over intentions in the Pacific theater, as the two now became the dominant military powers there. An immediate consequence was the four *Tsukuba*-class armored cruisers, laid down between 1905 and 1908. These ships were designed to carry four 12-inch (305 mm) guns, a size generally allocated to capital ships and unprecedented for armored cruisers. They would be protected with 8 inches (203 mm) of belt and turret armour and 3 inches (76 mm) of deck armour and be capable of a speed of 20.5 knots. The *Tsukuba*s were intended to take the place of aging battleships and thus showed Japan's intention of continuing to use armored cruisers in fleet engagements. They were also exactly the type of ships for which the college had argued unsuccessfully to add to the U.S. Navy before switching to battlecruisers.

Therefore, while the Navy did not react as Germany and Britain built increasing numbers of battlecruisers, it took a very different tack when Japan laid down its first ship of this class, *Kongō*, in Britain on 17 January 1911. On 13 June, U.S. Naval Intelligence confirmed she was to be the first of four ships, the other three to be built in Japan, which would form a fast division for the IJN. The following day, the Secretary of the Navy asked the General Board to consider the construction of American battlecruisers for Pacific service, as the *Pennsylvania*s and *Tennessee*s would no longer be viable units in the face of such opposition. The General Board, not willing to forego battleship construction in favor of auxiliary types such as battlecruisers, balked. On 29 August, it suggested that C&R research a ship under 30,000 tons that could steam at 29 knots (54 km/h), carry eight 14-inch (356 mm) and twenty-four 5-inch (127 mm) guns and have a protective system comparable to the *Nevada*-class battleships. In other words, the board requested an American version of the *Kongō*.

In view of the board's lack of urgency, C&R took nearly a year to research this project. The proposed main battery of eight 14-inch guns was kept constant while other factors were calculated—speeds of 26, 29 and 32 knots; operating ranges of 5000, 7000 and 8000 miles; and belt armor of 8, 11 and 14 inches. On 12 July 1912, Naval Constructor R.H. Robinson presented these studies at a lecture he gave at the Naval War College with the General Board in attendance. There, he emphasized 8 inches as an absolute minimum for armor protection and recommended a radius of 8000 miles, the same as in U.S. battleships. The General Board's reaction was to request four battlecruisers for the 1914 Naval Building Program.

## Design

### General characteristics

In their original 1916 configuration, the battlecruisers were to carry ten 14"/50 caliber guns in four turrets, with two triple superfiring over two dual because there was not enough beam to accommodate the larger barbettes of the triple turrets slight further forward and aft. They would have a secondary armament of eighteen 5"/51 caliber guns on a displacement of 34,300 long tons (34,900 t) and steam at 35 knots. All of these specifications were tempered by their sparse armor compared with contemporary battleships. C&R estimated 180,000 shaft horsepower would be needed to obtain this planned speed. This would require 24 boilers, which became problematic, as there was not enough room for the boilers under the armored deck in such a long, comparatively narrow hull. The solution decided upon was to place half of the boilers above the deck on the centerline with armored boxes fitted around each one. There was also the challenge of the many exhaust uptakes needed. The *Americas* were given "no less than" seven funnels, four of them side by side. Also, with such a long, narrow hull came a consequent penchant for bending, which led to the challenge of adequate hull strength, especially longitudinal strength. This challenge was complicated in a capital ship by the heavy weight of main turrets and guns. This was an area in which British battlecruisers were notably deficient. Structural members on HMS *Invincible* were so weak that her double-bottom frames distorted. HMS *Renown* had to go into drydock immediately following her preliminary gunnery tests because the hull structure could not withstand the bending stresses from firing her forward main guns. When the "large light cruiser" HMS *Courageous* weathered a heavy gale during her initial trial run, a number of her outer hull plates were so distorted that they had to be removed, sent back to the foundry and renewed.

In the *Americas* longitudinal strength was challenged further by the large amount of freeboard required at the forward section of the hull to keep the ships dry and maintain a high speed in various types of weather. Also, while the 8 inches (203 mm) of belt armor being considered was not an impressive amount in itself, the belt's running potentially along 80 percent of the waterline and covering the entire side amidships made the amount of armor protection impressive by European standards. Because of the difference in ultimate tensile strength between armor steel and hull steel, severe stresses on the hull were expected. These factors plus the ships' unusual length prompted Naval Constructor R. H. Robinson, who led the design group for the *Americas*, to make careful analyses of strength, buoyancy and stresses expected in service. For instance, designers assumed customarily that a ship needed to withstand stresses caused by a wave of the ship's length with a ratio of height to length of 1:20. Robinson found a more reasonable ratio at 1:26 for the *Americas*, which also promised considerable savings in weight.

One suggestion from C&R was to make the belt armor a load-bearing member by connecting plates end to end. This was found inordinately difficult to be practical and, while it would have added girder strength where most badly needed, was considered too radical a proposition to be truly safe. Another idea, subsequently adopted, was to design the forecastle to break abaft the turrets. The challenge then became to continue the longitudinal strength contributed by the armored deck past this point to the end of the stern. This became a difficult design problem, especially with the need to save weight wherever possible and the fact that light structural members combined with heavy armament weight had become a source of grief for the British. One proposed solution was to use a combination of three decks—a strength deck at the top of the hull, a protective deck which would rest atop the belt armor, 10 feet (3 m) above the waterline, and a splinter deck below that, just above the waterline. A third idea, also adopted, was to continue the longitudinal bulkhead between the protective and splinter decks down to the bottom of the ship to add strength. The severity of the strength and weight challenges necessitated a larger displacement of 33,000 tons and a hull of 850 feet (259.1 m) instead of 800 feet (243.8 m) to give enough internal volume to accommodate all the needed machinery. Even so, the size of the power plant meant pushing the main turrets further toward the ends of the ships, which increased hull stress. This was why the idea was adopted to place half the boilers above the armored deck leading to their famous 7 funnels

The ships were notable at the time for their 7 funnels being known colloquially in the fleet as "Camel Packs" due to their abundance of funnels. The nickname did not last for long as the boilers were trunked into two funnels amid ships during a mid 1920s refit. After the refit the ships were similar to the Lexington Class in appearance with the exeption of the main armament.

### Propulsion

Turbo-electric propulsion was selected for the battlecruisers despite the fact it needed more room than geared turbines to allow for better underwater protection that wartime experience showed was essential. First used in the *New Mexico*-class battleships, it also had several other advantages. The turbines could run at their optimum speed, without regard to propeller speed, which was economical on fuel and the machinery could be easily sub-divided which increased the ships' ability to withstand torpedo hits. The substitution of flexible electric cables for bulky steam-lines meant that the motors could be mounted further to the rear of the ship, which reduced both vibration and weight by shortening the propeller shafts. Also, the ship could go astern at full power simply by reversing the electrical polarity of the motors. Despite these factors and the fact that American companies would have struggled to produce the very large geared steam turbines needed for such big ships, the Curtis Company tried unsuccessfully to convince the Navy to reverse this decision. The Navy countered that doing so would mean a complete rearrangement of machinery spaces and a reduction in underwater protection.

### Armament

#### Main guns

Designed and built with 10 14 Inch/50 Caliber Guns. When the class underwent modernization during the late 1930s they were rearmed with the 14 Inch/50 Caliber Mark B guns originally intended for the North Carolina Class.

#### Secondary

Originally built with 18 5 Inch/51 Caliber in casemates. These were removed during the mid 1930s modernization. They were replaced by 20 5 Inch/38 Caliber dual purpose guns in 10 twin mounts amidships.

#### Anti Aircraft

Originally completed without AA guns this was rectified in the mid 1930s when they were fitted with 30 Browning M2 50 Caliber Machine guns to complement the 5 Inch/38s in their role of AA defense