UNITED STATES NAVY (UNITED STATES OF AMERICA)

Ship project history: Omaha class cruisers were built in limits of the arrogant shipbuilding program of 1916. One of the main requirements to a 7000t cruiser-scout was 35kt speed. This circumstance has predetermined an appreciable out-of-balance of main project particulars. The hull was as much as possible narrow, having given to clear "destroyer" lines. Thus a structural frame for the purpose of economy of weight have probably facilitated, that in a combination with very powerful and, as consequence, heavy-weight machinery has led to vibration on full speed.

The excessive thrust on achievement of high speed has led to that the quantity of displacement, assigned on arms and protection, has appeared notably less, than at foreign contemporaries: so, only 8% of displacement was assigned on protection. Besides, the desire to ensure maximum fire at fore and aft angles has led to introduction of doubtful arrangement of main artillery in two-level casemates fore and aft: they notably made ship ends heavier, thus it is not enough defending guns from fire of the opponent as had only splinterproof protection.

According to the project new cruiser should have 7050t displacement, 35kt speed, armament of 10 152/53mm guns (4 instruments in fore casemates, 4 aft and 2 more guns on open mounts amidships), 2 76/50mm AA guns and 2 twin 533mm TTs.

The building contract was signed 8/7/1916, however first ships have laid down only two years later after the project was significantly redesigned (basically because of critical expressions about insufficient armament). Open 152mm guns were refused, but twin turrets were appeared at ship ends (even more having increased a local overload). Torpedo armament was strengthened, having added to two twin TTs on a main deck two more triple on upper (fwd from a stern casemate). Originally planed catapult on a quarter-deck had refused, having changed by two trainable on an upper deck. Changes in the project have led to displacement growth approximately on 400t, that has lowered speed on 1kt.

For the first time in American practice machinery was arranged on en echelon: engine rooms were placed between fore and stern boiler rooms groups. Turbines and boilers were produced by different companies and that has led to appreciable disorder of running characteristics, and the ships have appeared are shared on group with "high endurance" (CL9-13) and group with "low endurance" (CL4-8). However a planed endurance (10000nm at 10kts) was never possible to achieve.

In 1940 it was planed to convert the Omahas to air defence cruiser armed by 2 twin 152/53mm guns, 7 single 127/38mm DP guns and 6 quadruple 28mm MGs, but their stability in this configuration caused concern and modernisation has been rejected.

Ship protection: Main 5.8m high belt protected only machinery and was closed by 38mm fore and 76mm aft bulkheads. Main deck consisted of 22mm STS armour and 15mm plating. Guns had only 6mm protection.

Modernizations: 1924 - 1925, all: - 2 x 2 - 533 TT

1925 - 1941, Cincinnati, Raleigh, Detroit, Richmond: - 2 x 1 - 152/53

1925 - 1941, Marblehead: - 1 x1 - 152/53

1941, Omaha, Milwaukee, Detroit, Richmond, Trenton, Marblehead, Memphis: + 4 x 1 - 76/50 Mk 10/17/18/20/21, 8 x 1 - 12.7/90

1941, Cincinnati, Raleigh, Concord: + 2 x 4 - 28/75 Mk 1

1942, Omaha, Milwaukee, Trenton, Memphis: - 2 x 1 - 152/53, 1 x 1 - 76/50, 8 x 1 - 12.7/90; + 2 x 4 - 28/75 Mk 1, 8 x 1 - 20/70 Oerlikon, SC, Mk 3 radars

1942, Cincinnati, Raleigh: - 8 x 1 - 12.7/90; + 3 x 1 - 76/50 Mk 10/17/18/20/21, 8 x 1 - 20/70 Oerlikon, SC, Mk 3 radars

1942, Detroit, Richmond, Marblehead: - 1 x 1 - 76/50, 8 x 1 - 12.7/90; + 2 x 4 - 28/75 Mk 1, 8 x 1 - 20/70 Oerlikon, SC, Mk 3 radars

1942, Concord: - 2 x 1 - 152/53, 8 x 1 - 12.7/90; + 3 x 1 - 76/50 Mk 10/17/18/20/21, 8 x 1 - 20/70 Oerlikon, SC, Mk 3 radars

late 1942, Cincinnati, Memphis: - SC radar; + SK radar

1943 - 1944, Omaha, Milwaukee, Detroit, Concord, Trenton, Marblehead: - 1 x 1 - 76/50, 2 x 4 - 28/75, SC radar; + 3 x 2 - 40/56 Bofors, 4 x 1 - 20/70 Oerlikon, SK, 2x SG, Mk 3 (2nd) radars

1943 - 1944, Cincinnati: - 2 x 4 - 28/75, 2 x 3 - 533 TT; + 1 x 1 - 76/50 Mk 10/17/18/20/21, 3 x 2 - 40/56 Bofors, 2 x 1 - 40/56 Bofors, 2x SG, Mk 3 (2nd) radars

1943 - 1944, Raleigh: - 2 x 4 - 28/75, SC radar; + 1 x 1 - 76/50 Mk 10/17/18/20/21, 2x SG, SK, Mk 3 (2nd) radars

1943 - 1944, Richmond: - 1 x 1 - 76/50, 2 x 4 - 28/75; + 3 x 2 - 40/56 Bofors, 4 x 1 - 20/70 Oerlikon, 2x SG, Mk 3 (2nd) radars

1943 - 1944, Memphis: - 2 x 4 - 28/75, SC radar; + 2 x 2 - 40/56 Bofors, 4 x 1 - 20/70 Oerlikon, 2x SG, SK, Mk 3 (2nd) radars

1945, Detroit: - 2 x 1 - 152/53, 2 x 3 - 533 TT; + 2 x 2 - 40/56 Bofors

Naval service: Raleigh was badly damaged in Pearl Harbour 7/12/1941 by Japanese air torpedo and repaired till July, 1942. Marblehead 5/1/1942 has received 2 direct bomb hits and some near-misses, repair was till the end of 1942.