Pensacola-class cruiser

Class overview
*USS Pensacola* (CA-24)**
Name:	Pensacola-class cruiser
Operators:	United States Navy
Preceded by:	St. Louis class
Succeeded by:	Northampton class
In commission:	1929–47
Completed:	2
Retired:	2
Preserved:	0
General characteristics
Type:	Heavy cruiser
Displacement:	9100 long-tons (standard) 11512 long-tons (full)
Length:	585.5 ft (178.5 m)
Beam:	65.0 ft (19.8 m)
Draft:	19.5 ft (5.9 m)
Propulsion:	Steam turbines 8 boilers 4 Screws 107,000 hp (80,000 kW)
Speed:	32.5 knots (60.2 km/h; 37.4 mph)
Complement:	1,200
Armament:	10 × 8-inch/55 caliber guns (2×2, 2×3) 8 × single 5-inch/25 caliber guns 4 × quad 1.1-inch/75 caliber guns (as built) 24 × 40 mm Bofors guns (6x4) (1943) 28 × 20 mm Oerlikon cannons (1943) 6 × 21-inch torpedo tubes (removed before 1941)
Armor:	2.5-4-inch belt 1-1.75-inch decks .75-2.5-inch turrets .75-inch barbettes 1.25-inch CT
Aircraft carried:	2
Aviation facilities:	2 catapults no hangars

The Pensacola class of United States Navy heavy cruisers were the first "treaty cruisers", designed under the limitations set by the Washington Naval Treaty, which limited cruisers to a maximum of 10,000 tons displacement and a maximum main battery caliber of 8 inches.

In an effort to remain within treaty limits, while still mounting a very heavy main battery of ten 8" guns, the hull was of welded construction, and the armor belt was thin (varying from 2.5 to 4 inches in thickness). This was inadequate to protect her vitals from enemy 8" shells and was no thicker than the armor on 6" gun cruisers. In fact, Pensacola and Salt Lake City were classified as light cruisers due to their minimal armor until re-designated in July 1931 as heavy cruisers in accord with international practice of designating all cruisers with guns larger than 6" as heavy cruisers.

Their main armament consisted of ten 8 in (200 mm) guns, in two twin turrets on the main deck, and two triple turrets two decks above, making it one of the two US Navy ship classes (besides the Nevada-class battleships) to have different-sized turrets for main armament. All guns in each turret were mounted in a single slide, and were unable to elevate independently of each other. Also, unlike the very few other ships with different sized main battery turrets (Nevada-class battleships and King George V-class battleships) the Pensacolas had the larger turrets superfiring over the smaller turrets. (The original design for the Lexington-class battlecruisers would have shared this unique arrangement, as they called for ten 14-inch (360 mm) guns, with the triple turrets superfiring over twin turrets, and would have appeared like scaled up Pensacolas.) Placing heavier turrets above lighter ones allows for finer lines for a given length, however this causes top heaviness and reduces stability.

Unfortunately, because of the rather unusual main battery layout and their heavy tripod fore-masts, they were top-heavy and prone to excessive rolling. This combined with low freeboard forward made them inferior seaboats compared to later designs. Rework in the shipyards modified the hull and superstructure in the 1930s to eliminate the rolling.

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Wikipedia