The Pacific War Online Encyclopedia

Portland Class, U.S. Heavy Cruisers

Tonnage	10,300 tons standard displacement
Dimensions	610'4" by 66'1" by 21' 186.03m by 20.14m by 6.40m
Maximum speed	32.7 knots
Complement	807
Aircraft	2 catapults 4 seaplanes
Armament	9 8"/55 guns 8 5"/25 AA guns 8 0.50 machine guns
Protection	3" (76mm) belt (machinery) 5.75"(146mm) belt (magazines) 2.5" (64mm) deck 2.125" (54mm) magazine crowns
Machinery	4-shaft Parsons geared turbine (107,000 shp) 8 Yarrow boilers
Bunkerage	2125 tons fuel oil
Range	10,000 nautical miles (19,000 km) at 15 knots
Modifications:	Early 1942: Added 4x4 1.1"/75 AA guns, 12 20mm Oerlikon AA guns. Late 1942: Added FC and FD fire control radars. 1943: Comprehensive radar suite installed, which included SK air search radar. 1.1" guns replaced with 4x4, 4x2 40mm Bofors AA guns. 1944: 20mm armament increased to 17-19 guns. One catapult landed and aircraft complement reduced to 2-3 aircraft.

The Portlands were completed in 1932-1933 and their design reflected the 1930 London Naval Treaty. The first group of ships of the 1929 naval program of 15 heavy cruisers were originally to be repeat Northamptons. However, this design was somewhat underweight relative to the treaty restrictions, and the newly imposed limits on total numbers of cruisers discouraged the building of second-class units. There was also a desire to develop a cruiser with better protection and with the range to counter German-style commerce raiders. Since three of the ships were being built in Navy yards, where major design changes in the midst of construction would not incur a large cash penalty, it was decided to modify two of on the ways with some of the desired improvements. Increasing the side belt was prohibitively expensive, but fairly heavy armor was placed around the magazines. The third ship was completed as Wichita.

The ships ended up rather top heavy, which caused them to roll badly, and Indianapolis capsized after a single torpedo hit.