The Manahan class were a major advance over the previous Mikkelson class. It was a pity they had not been designed and built two years later as they would have been built with battleship sized guns instead of cruiser weapons. The idea for the Manahan class was to double the firepower of the ships and get rid of the intermediate 6" sized weapons. Four turrets (of a new model) were fitted, two fore and two aft. Smaller 4" weapons were fitted for anti-torpedo boat duties. For their time, these were seriously big ships. Cruisers over 500 feet long were unheard of. The biggest change was unseen. The change from triple expansion engines to turbines.



What to do with four 15 year old cruisers that did not fit within the Treaty limits? They were not modern enough to be put into the 'save' list. The ships would be demilitarised and used as trials ships and training ships. It was the advent of the 'Area Defence Vessel' that saved these ships. 20 odd years old and the ships were converted. Antarctica had many ports and bays around the coastlines and the surrounding islands that needed some form of protection and early warning capability.



As ADV's these ships were probably more valuable than they ever were as full cruisers. It was their ability to be able to act as mother ships to the big flying boat squadrons. Providing local support with their own seaplanes took pressure off having to build airfields in areas that would not be conducive to construction. Beside the original main armament for longer range combat, the ships had heavy and light AA weapons for port protection.

Early in the war, when escort carriers were not yet available, these four ships were used as convoy escorts, where their aircraft could be used for ASW protection, but only for valuable convoys. One of these ships was torpedoed and sunk during these duties, and shortly thereafter the other three were withdrawn from Escort Command.

 

Displacement	16,500 tons standard, 18,400 tons full load
Length	555 ft
Breadth	70 ft
Draught	24 ft
Machinery	2 shaft, steam turbines, 44,000ihp
Speed	26 knots
Range	9,000 miles at 10 knots
Armour	7" side, 3" deck, 5" turrets (Some belt armour removed as ADV)
Armament	As completed 8 x 9.5" (4x2) 6 x 4" (6x1) replaced with AA guns 1917	As ADV from 1936 4 x 9.5" (2x2) 8 x 4" (4x2) 8 x 2pd AA (2x4) 10 x 20mm (10x1)
Aircraft	Nil	6-8 depending on size and type
Torpedoes	12 x 18" (4x3)	Nil
Complement	750-780 as Flagship
Notes

AAC Nemesis in its mid-1930's seaplane mode.