The final fifth turret from Callisto was to be used to create a new class of ship for the Algarvian Navy. Algarve had seen the use of spare turrets by the British to create several classes of Monitor type vessels. These vessels had proved very useful in anchoring the seaward end of the Army on the Continent, and at the Gallipoli Peninsular. Being able to project their power out 15 miles inland was a useful attribute. But the British Monitors were slow and often had to be towed into battle as their engines were unreliable or too small to propel the ship against a tide.
The Algarvian Navy laid down the Sledgehammer in 1937 with completion set for 1940. However the steel shortage created in 1940 by the change from one shift to two shift working rates and the use of double the amount of steel meant that steel production had had to be prioritised with some jobs being slowed considerably till steel production caught up.
Finally completed in 1941, the Sledgehammer was an advance on what a Monitor had been like. The main advance was in speed. Algarve was thousands of miles away from the proposed area of operations. To get to these operational areas required more speed than had been previously given to monitors. The Sledgehammer was capable of 22 knots, a speed that gave the ship much more operational radius than the earlier vessels.
Displacement: 10,850 tons normal, 13,450 tons full load.
Dimensions: 459 x 82 x 14 feet.
Machinery: 2 shaft, geared turbines, 22,000shp
Speed: 22 knots
Endurance: 7,000 miles at 12 knots
Armour: 4.5” belt, 2.5” deck, 15/9/6” turret.
Armament:
2 x 15” (1x2)
8 x 4.5” (4x2)
20 x 40mm (10x2)
Aircraft: 1
Crew: 625