CA-68 Baltimore Class
usnc-bostonsmall.jpg
(some parts and underwater details taken from Shipbucket.com)

Ship Characteristics

Dimensions Length 673.5 ft
Beam 71 ft
Draft 26 ft
Displacement (Standard) 13,700 tons
Displacement (Full Load) 17,200 tons
Performance Speed (max) 34 knots
Speed (Cruising) 15 knots
Endurance 9,000 nm. at 15 knots
Armament Heavy Guns 9 8 inch L55
Medium Guns 12 5 inch L38
Light guns 52 40mm, 20 20mm
Armor Belt 6 inches
Deck 3 inches

Background

Studies for a new heavy cruiser began in September 1939 similar to Wichita (CA-45), which would form the basis for this class, though her stability problem would have to be remedied. Machinery arrangement would be similar to that of the Cleveland (CL-55) class with the armored belt extending further foreward to protect against magnetic mines. Four ships were authorized on 1 July 1940; their construction was delayed due to the emphasis on light cruiser construction during the pre-war period. Sixteen more (CA-122 to 138) were ordered on 7 August 1942. Shortly prior to christening, it was decided to change the name of CA-70 from the planned Pittsburgh to Canberra, a very rare case of a U.S. ship being named after a non-U.S. city although the name was actually selected in honor of the Australian cruiser HMAS Canberra. The decision to make the change was taken as a result of an incident in which an American troopship, the USS Lafayette with the better part of an infantry division on board was sailing to the Philippines when she hit a mine off Mindanao. She was drifting helplessly in what was believed to be a mined area and there was the prospect of a major disaster. The Australian cruiser, HMAS Canberra was on the scene. Although the Captain of the Lafayette sent a message to her, warning her of the mines and advising her to keep clear, the Australian cruiser replied by signalling "Blood is thicker than water". Then, she sailed into the minefield, prepared a very hasty salvage line arrangement and towed the troopship clear of danger. Once the two ships were clear of mines, the tow was rearranged to more conventional standards and the Canberra then towed the Lafayette to Cavite in Luzon. The incident made major headlines in a United States that was gearing up for a war against Nazi Germany more or less by itself and the Navy responded to this public pressure by renaming CA-70.

Of the original class, Baltimore (CA-68) was the first to commission, in April 1943; Toledo (CA-133) was the last, in July 1946. CA-122 to 129 and 137-138 were re-ordered in late 1942 with design changes including boiler uptakes trunked into a single funnel, shortened superstructure, repositioned directors, and smaller hangar. This became the Modified Baltimore (CA-122) class. Fourteen Baltimore class heavy cruisers were ulitimately built, and 10 of the Modified Baltimore class.

Resembling the Cleveland class, the Baltimores carried three triple 8-inch/55 gun turrets (Mk12 or 15) with an elevation of 41 degrees. They were the first heavy cruisers built with the twin 5-inch L38 DP secondary armament. Their anti-aircraft battery was only surpassed by battleships in the US fleet. This resulted in the almost sole role of these ships, being the escort of the heavy and light carriers. They proved the most successful of the U.S. cruiser designs under the demanding conditions of the North Atlantic, the CL-55 Cleveland class being regarded as too limited in stability while the Atlanta class were seen as being too small for fleet operations in the heavy seas that characterized the North Atlantic Environment. Although the Baltimore class was originally planned to have four quad 1.1-inch AA guns; this was changed to four quad 40mm AA guns during construction and this was supplemented with 20mm AA guns. The 20mm guns were found to be a major liability during operations in the North Atlantic and were largely removed from 1945-46 onwards, some being replaced by additional 40mm quads. From the end of 1945 onwards, the 40mm quads started being replaced by 3 inch L50 twin mounts (a total of 11 such mounts being carried) and many of the Modified Baltimore class were completed with these guns.

Of the 14 ships of the class, only Canberra suffered damage, being hit by a torpedo from a German submarine off Churchill in Nova Scotia. Oregon City suffered severe weather damage in December 1945, just prior to the Battle of the Orkneys and returned to New York Navy Yard for repairs. A survey showed she was structurally defective, her keel being more than 6 inches out of true while serious welding faults were discovered in her bows and superstructure. As a result, she was withdrawn from active service in January 1946 (her place in the fast carrier fleet being taken by Wichita) and assigned to Norfolk as an alongside test and experimental ship. She remained in this unglamorous role until 1960 when she was towed away and scrapped.

Postwar, the Baltimore and Modified Baltimore classes remained in service, providing the screen for the new carrier groups. Following the initial, experimental conversions of Boston and Canberra, a standardized conversion scheme was devised that relied largely on prefabricated assemblies. This was applied to all the Modified Baltimore class other than Oregon City and three of the original Baltimore class to give a total of 12 missile cruisers that were regarded as a separate class, the CG-123 Albany Class. At that point, the flood of new-construction missile ships entering the Navy was such that further conversions were deemed unnecessary. Of the nine surviving Baltimore class gun cruisers, six were sold to other navies while the last three were scrapped in 1965.

Missile Conversion.

usnc-boston02small.jpg
(some parts and underwater details taken from Shipbucket.com)

Ship Characteristics

Dimensions Length 673.5 ft
Beam 71 ft
Draft 26 ft
Displacement (Standard) 13,300 tons
Displacement (Full Load) 17,500 tons
Performance Speed (max) 34 knots
Speed (Cruising) 15 knots
Endurance 9,000 nm. at 25 knots
Armament Heavy Guns 6 8 inch L55
Medium Guns 10 5 inch L38
Missiles 144 Terrier
Armor Belt 6 inches
Deck 3 inches

Originally, it was planned that each carrier task group would eventually have four eight inch and four six inch cruisers as part of its screen. With the splitting of the six wartiime task groups to twelve peace-time task groups post-war, this was also halved to give two eight inch and two six inch cruisers per group. During the 1950s, it was intended to replace these ships with missile cruisers and an initial start was made by means of an experimental conversion of the cruisers Boston and Canberra to carry two twin Terrier missile launchers aft. The six forward eight inch guns were retained, resulting in the two ships carrying the hybrid designation CAG. The ships were designed to carry vertical-load magazines but the early conversion work showed this to have been a bad mistake since the depth of the magazines effectively meant the whole rear of the ship had to be gutted. Horizontal-load magazines would be preferred from this point onwards and were used in the definitive "Tall Lady" conversions. Also, it was found that inadequate numbers of missile guidance radars had been provided and there was a gross missmatch between the ship's engagement capability and the number of rounds carried. Boston and Canberra were never regarded as being anything more than experimental ships and, when adequate numbers of better missile cruisers were available, they were stripped of their missile equipment and sold to Argentina.

Class Members

Baltimore Class

Number Name Ordered Laid Down Launched Commissioned Fate
CA-68 Baltimore 1940 1941 1942 1943 Sold to Argentina 1958
CA-69 Boston 1940 1941 1942 1943 Converted to missile cruiser CAG-69 1952 - 1954
CA-70 Canberra 1940 1941 1943 1943 Converted to missile cruiser CAG-70 1952 - 1954
CA-71 Saint Paul 1940 1941 1943 1943 Sold to Argentina 1958
CA-72 Pittsburgh 1942 1943 1944 1944 Sold to Brazil 1958
CA-73 Rochester 1942 1943 1944 1945 Sold to Brazil 1958
CA-74 Columbus 1942 1943 1944 1945 Sold to Spain 1960
CA-75 Danbury 1942 1943 1945 1945 Sold to Spain 1960
CA-130 Bremerton 1942 1943 1944 1945 Decommissioned and scrapped 1965
CA-131 Fall River 1942 1943 1944 1945 Decommissioned and scrapped 1965
CA-132 Macon 1942 1943 1944 1945 Decommissioned and scrapped 1965
CA-133 Toledo 1942 1943 1945 1946 Converted to missile cruiser CG-133 1954 - 1956
CA-135 Los Angeles 1942 1943 1944 1945 Converted to missile cruiser CG-135 1956 - 1958
CA-136 Chicago 1942 1943 1944 1945 Converted to missile cruiser CG-136 1955 - 1957

Modified Baltimore Class

Number Name Ordered Laid Down Launched Commissioned Fate
CA-122 Oregon City 1943 1944 1945 1945 Decommissioned 1946 and scrapped 1960
CA-123 Albany 1943 1944 1945 1946 Converted to missile cruiser CG-123 1954 - 1956
CA-124 Litchfield 1943 1944 1945 1946 Converted to missile cruiser CG-124 1956 - 1959
CA-125 Rockville 1943 1944 1945 1946 Converted to missile cruiser CG-125 1955 - 1958
CA-126 Cambridge 1943 1944 1946 1946 Converted to missile cruiser CG-126 1956 - 1959
CA-127 Bridgewater 1943 1944 1946 1946 Converted to missile cruiser CG-127 1956 - 1959
CA-128 Kansas City 1943 1944 1946 1946 Converted to missile cruiser CG-128 1955 - 1958
CA-129 Tulsa 1943 1944 1946 1946 Converted to missile cruiser CG-129 1955 - 1958
CA-137 Norfolk 1943 1945 1946 1947 Converted to missile cruiser CG-137 1954 - 1957
CA-138 Scranton 1943 1945 1946 1947 Converted to missile cruiser CG-138 1954 - 1957

Boston Class CAG

Number Name Ordered Conversion started Conversion completed Recommissioned Fate
CAG-69 Boston 1951 1952 1954 1955 Sold to Argentina 1964
CAG-70 Canberra 1951 1952 1954 1955 Sold to Argentina 1964
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