Treaty Heavy Cruisers (Pensacola, Northampton, and Portland Classes)
Interim Heavy Cruisers (New Orleans and Wichita Classes)
- Post-Treaty Heavy Cruisers (Baltimore, Oregon City, and Des Moines Classes)
United States Heavy Cruiser Development (Part 1: The Treaty Designs)
Interestingly Enough, the United States didn't gradually change from previous cruiser designs to more modern variants like other nations. Rather, the United States saw a massive leap in Cruiser design from the 1905 St. Louis Class to the Pensacola Class in the last 1920s. However, they appeared to hit the nail squarely on the head as the modern Pensacola Class set the base design for all future Cruisers. As a result, the Heavy Cruisers in the US Navy did not change from class to class as much as the cruisers did in other nations.
First entering service in 1929, the two ships of the Pensacola Class served as the prototype for all future heavy cruiser design. Though changes were of course made, the general design of the Pensacola Class could still be seen in the Des Moines class nearly twenty years later.
The trademark feature of the Pensacola Class was its unusual gunnery arrangement. Not all the turrets were the same size or carried the same number of cannons. This makes the Pensacola class cruisers one of the few warship designs to have such a feature. (Other ships include the Nevada Class BB and the King George V Class BB) The reason for placing the guns like this was to improve the lines as well as place the heavier turrets closer to the ship's center. However, the drawback of this arrangement was that the ships were notoriously top heavy. The low freeboard of the ships also caused them to be extremely poor sea boats. Extensive work in the shipyard was required to correct this problem.
(The Pensacola Class compared to the newer New Orleans class)
Interestingly enough, the Pensacola Class was similar to Japanese cruiser design in a few aspects. Notably an attempt to maximize the amount of Firepower for a given displacement and at the cost of other traits. Hence why the class squeezed in 10 guns as opposed to the standard 9 on all later vessels. Armor was also sacrificed in favor of heavy firepower. However, due to the similar design philosophies, the Pensacola class has highly unstable just like the Japanese vessels.
The one area that the Pensacola class got right was the power plant. The US design board had long envisioned that cruisers needed to be capable of high speeds, whether of escort, commerce raiding, or chasing down combatants. Not only should the ship be quick, it also needed to be able to steam for long distances. The Pensacola class could both steam at 32.5 knots and cross the vast Pacific easily. These features would be important as the ship served throughout the Second World War.
Overall, the Pensacola Class Cruiser design was promising in regards to forming a basis for future advancement. Compared to other heavy cruisers of the time, it was neither fantastic or particularly poor. However, the US Navy still viewed the design as flawed and began developing the next series of Cruiser even as the Pensacola class was under development.
Entering service only a year after the Pensacola class, the Northampton class proved to be an even better design than its predecessors. While no great design departure, the Northampton incorporated several subtle changes over the Pensacola class that went a long way in improving the ship's capabilities.
On the subject of Firepower, the Northampton dropped the four turret design for 3 triple turrets with 2 turrets fore and one aft. This saved a lot of weight compared to the Pensacola design and made the ships less top heavy. The standard triple turrets were also cheaper to produce and easier to service. This in turn made the turrets and the ship more reliable. One less turret ring also had the benefit of enhancing the ship's structural strength, allowing it to take more damage.
Armor was the most notable advancement over previous designs. While the belt of the Pensacola class could be as thin as 2", the Northampton class had 3" armor at its thinnest sections. Deck, turret, and barbette armor was also improved.
Another welcome advancement was the inclusion of a higher forecastle which increased freeboard. The final three ships of the class had the forecastle further extended aft and the feature was also copied into all future designs. The Northampton class also had the distinction of being the first warships to have bunks for crew members instead of the traditional hammocks and a dedicated hanger for aircraft.
Interestingly enough, while US Navy designers considered the Northampton a step in the right direction, they still viewed the design as flawed. Amazingly, despite the large increase in armor, the Northampton class was actually lighter than the Pensacola class at 9,050 tons. The ship was only using 90% of its allowed tonnage and its light weight caused them to roll in heavy seas. Better use of weight was needed. Once again, an improved version was ordered and in less than two years, the Portland Class cruisers entered the scene.
Entering the scene in 1932, the Portland class was another subtle advancement in Cruiser design. Basically a modified Northampton class cruiser, the Portland class was designed to be heavier, better armored, and better protected. They were also to include the required facilities to act as flagships, a feature that required larger super structures compared to older designs.
While the Portland Class carried the same triple turret configuration and Mark 9 8"/55 guns as the preceding cruisers, the Portland class used improved ammunition that greatly increased the range of the cannons. The locations of the 5"/25 AA guns was also adjusted to provide better firing arcs. The Portland Class was also the first of the heavy cruisers to remove the torpedo tubes from the initial design as it became evident that gunnery would be the primary weapon for most engagements.
Armor was further improved in the class. Deck armor was increased to 2.5" and the belt was increased to a minimum of 3.5" and 5" over the magazines. Bulkheads were thickened to between 2" and 5.5" depending on the location. Turret armor was improved as was the armoring of the conning tower.
Despite being nearly 900 tons heavier than the Northampton Class and carrying the same amount of horsepower, the Portland class was slightly faster. A longer length and redesigned bow improved speed and range, allowing the ship to reach 32.7 knots or steam for 10,000 nautical miles at 15 knots. The improved forecastle of the later ships of the Northampton class was also carried over, making the Portland class a better sea boat compared to older cruisers.
Overall, the Portland class continued the heavy cruiser trend. Slightly better armored, slightly more firepower, and slightly more agile. However, a major problem still existed due to the Portland class still displacing less weight then intended. Though designed to be over 12,000 tons at full load, the ships never displaced more than 9,950 tons. Because of this, the ships also rolled excessively like older designs.
Because of these design problems, the Navy designers once again opted for a new design. 8 vessels were designed to be modified Northampton class vessels, however because of faults, the ships were then redesigned again. 2 Became the Portland Class vessels, while the remaining 6 were modified into the much improved New Orleans class. It was the New Orleans class that would herald in the next generation of heavy cruiser designs that put the US at the top of cruiser designs worldwide.
Overview of the Treaty Cruisers
From the introduction of the Pensacola cruisers, it became obvious to US naval designers that they had discovered a basic design with enormous potential. Following the Pensacola class, the US navy had settled on a design with a good balance of armor, firepower, and speed. This design was advanced over 8 generations into the most formidable vessels found worldwide. Even with the problems of the earlier designs, the ships still proved to be capable vessels and served throughout the Second World War with distinction.
*Notes* This article is shorter than my typical ones, but among my knowledge of cruisers, I know the least on these vessels. Part 2 and Part 3 will both be a great deal longer. Let me know what you think and as always I hope you enjoyed the article.