Pensacola class heavy Cruisers (1928)

USA (1928-30)

USS Pensacola, Salt lake City

The top heavy cruisers

When the treaty of Washington was ratified by the great naval powers in 1922, the nomenclature of types was modified and, in a sense, concepts consecrated. Among these changes, the most notable was the appearance of a new class in its own right, the “Washington Cruiser” which in fact was the typical form of the heavy cruiser, a new category with almost intangible, 10,000 tons – eight 8 inches (203 mm).

The British, the French and the Italians chose the configuration in double turrets. However the Americans from the beginning, confident in the design of triple turrets initiated for their dreadnought during the war, chose to adapt it for their cruisers, while maintaining a configuration in four turrets. The Admiralty had thus chosen a compromise with the most powerful artillery possible (ten pieces) on a strictly limited tonnage. Like other navies, we also choose the welding assembly technique to save tons of steel rivets.

Warning: This post is a placeholder allowing the construction of a semantic funnel, in relation to a good old single expansion SEO steam engine. Later in the year, this post will be properly expanded and the machinery upgraded with a steam turbine and many more boilers. Thanks for your comprehension.

Comparison between the Pensacola sister ships and USS New orleans at pearl Harbor October 1943.
Comparison between the Pensacola sister ships and USS New orleans at pearl Harbor October 1943.

But these choices were paid later in practice and throughout their career. Indeed, triple turrets – the most powerful – were mounted in superfiring position, rather than the contrary. In addition the tripod military masts were high and heavy, the aiming bridge, the conning tower.

With a limited width and a slightly built hull, this caused a dangerous overweight in the heights and the Pensacolas were quickly deemed big “rollers”. Their lodging was so excessive that their rapid evolutions and turns were deliberately limited in operation. In addition their pitch was high due to a “flush deck” too short, narrow and overloaded at the front, which caused that these ships “nose down” and plow excessively and disturbingly, in heavy weather.


Refit blueprint of the Pensacola class 1941

Refit for service

In the end this Pensacola class appeared as quasi-experimental. Pensacola’s sister-ship, USS Salt Lake City was launched in 1930 and completed in 1931. Both ships received additional keels in 1939 to improve their stability, then in 1942 their superstructures were lightened, while the massive tripod masts were removed. They received a radar, new fire control systems, and a powerful AA artillery complement.

This solved some of their deficiencies and they participated in this new distinction in major pacific operations before being removed from active service in 1947. They were essentially repulsors that defined the next class, the Northampton. It must be said that the last class of “heavy” cruisers dated back to the armoured cruisers Saint Louis of 1908. This explains many theoretical deficiencies that led to the plans of these ships of a new and unprecedented kind in the US Navy.

USS Pensacola alongside USS Vestal after the battle of Tassafaronga, 17 December 1942
USS Pensacola alongside USS Vestal after the battle of Tassafaronga, 17 December 1942

Career of the USS Pensacola

(Work in Progress…)

USS salt Lake City at the battle of Komandorski islands 26 march 1943
USS salt Lake City at the battle of Komandorski islands 26 march 1943

USS Salt lake City in action

(to come)

The end of Salt lake City as a target 25 may 1943
The end of Salt lake City as a target 25 may 1943

Characteristics (1941):
Displacement 9,100 t standard, 11,500 tonnes fully loaded
Dimensions: 178,5 x 19,9 x 5,9 m
Propulsion: 4 propellers, 4 Parsons turbines, 4 WF boilers, 107,000 hp. 32.5 knots.
Weaponry: 2×2, 2×3 x 203 mm (8 in), 4 x127 mm (5 in), 8 MG cal 0.5, 2×3 533 mm TTs, 4 seaplanes.
Protection: Turrets 165, belt 63, CT, casemate 105-50 mm, deck 51 mm.
Crew: 631 officers and sailors

USS Salt lake City 1932
The USS Salt Lake City in 1939. These over-armed sailors were so severely weighted in the highs that they were rebuilt in 1942.

USS Pensacola
The USS Pensacola in March 1945, in support of Okinawa. Note the evolutions with the original design

Sources
https://en.wikipedia.org/wiki/USS_Pensacola_(CA-24)
https://en.wikipedia.org/wiki/USS_Salt_Lake_City_(CA-25)

Portland class heavy cruisers (1931)
Northampton class heavy cruisers (1929)

4 Replies to “Pensacola class heavy Cruisers (1928)”

  1. Generally a good article but it doesn’t answer the question of why the triple turrets were placed above the twins. Did someone have a theory that this was better or was it just a mental lapse (stupidity)?

    1. Hello Doug
      All i know as states Wikipedia (no more info from conways on this) “Placing heavier turrets above lighter ones allows for finer lines for a given length”. I’ll dig deeper into the subject when the post (still going some changes) will be published on facebook.
      Best,

  2. Doug & Dreadnaughtz

    The super-imposition of the triple turrets over the twins in the Pensacola class cruisers was down to the fact that both – in order to ensure they complied with Washington Treaty-driven individual ship tonnage quota for the ‘heavy cruiser class’ (10,000 tons maximum, standard load) – had very narrow (‘fine’) lines toward both stem and stern. A larger, triple gun turret would require a larger barbette and turret substructure than could be fitted within such narrowly confined hull spaces fore and aft, so the decision was taken to put the triple mounts in a ‘super-firing’ (ie : above) position over the twins. Highly unusual (possibly not replicated in any other class of ship – ever !) but expedient in the circumstances, especially when there were so many ‘unknown quantities’ at this time of warship building. The subsequently-discovered drawback was that the triple-superfires-twin-gun-mount arrangement – along with the tall tripod masts fore-&-aft (and other topside needs) – created excessive ‘meta-centric height’, meaning these ships were somewhat prone to rolling in even normal Pacific Ocean swells, thus running a risk of capsizing in heavy seas. Fortunately this didn’t happen and later in the Pacific War during WWII, the 2 Pensacola class cruisers were given an overhaul that simultaneously increased their fighting efficiency, by augmenting the radar suite and increasing the anti-aircraft defence battery, and decreased their meta-centric height, principally by drastically cutting-down the height of their fore-&-aft masts, thus reducing ‘top-weight’.

    You probably already know this … Whatever – I just do it cos I love it …

    1. Excellent point Mark !
      The true reason behind this unusual choice could have been averted with the use of computer-assisted design. But… Others times, and treaties self-imposed by good will from top (no doubt the admiralties in general were not happy with these). Sometimes challenges are good for innovation though. I think too the design was never repeated anywhere else, but it needs to be verified for sure.
      -David B, alias Dreadnaughtz

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