How the Southampton, Gloucester, and Edinburgh batches grew

The Southampton group displaced 9,100 tons standard and 11,350 tons full load. The Gloucesters rose to 9,400 and 11,650 tons, while the Edinburghs reached 10,550 and 13,175 tons. HMS Birmingham is noted as a Southampton with different hull and bow construction, with its operational consequences left for later in the series. The Edinburghs added roughly 1,150 standard tons and about 22 feet over the earlier hull, well beyond treaty limits. All three groups retained four Admiralty three-drum boilers and broadly similar shaft horsepower, so hull form helped them reach comparable speeds. A longer, narrower hull could run more efficiently but make a less steady gun platform; the Arleigh Burke and Type 45 Daring hulls illustrate the same tradeoff in a modern comparison. Fuel capacity increased with each batch, and the Edinburghs managed about 8,000 nautical miles at 14 knots, compared with roughly 7,700 nautical miles at 13 knots for the Southamptons. The Edinburghs also used some of their extra displacement for armour and a somewhat heavier light anti-aircraft fit, and every batch received much more anti-aircraft armament during the war.