HMS Sentinel (BM-1929)


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One class of vessel that had proved useful during WW1 had been the Monitor, gunnery support vessels. At the end of the war the ones that had proved not so good were hastily scrapped. This left only the two Erebus class ships as effective units of the type (real timeline). The conversion of the two Lion class battlecruisers to hybrid seaplane carriers left four twin 13.5" turrets that could be used to build a new class of monitors. They were to be 7,000 ton vessels, and with a maximum speed of 16 knots. Armour equivalent to a light cruiser was fitted. It was the armoured deck that was given full measure with a 3" deck being fitted. Because of their speed, the four vessels were to be spread around the Empire to provide support where necessary. The first unit HMS Skirmisher was completed in 1928, the second HMS Sentinel in 1929, the third HMS Saracen in 1931 and lastly HMS Scourge in 1932. One was to be based at Malta and Singapore with the last two kept in home waters.

One of the main aims was to increase the range of the 13.5" guns from 23,000 yards at 20 degrees elevation, to 34,000 yards at 40 degrees elevation. This was achieved by cutting enlarged holes in the hoods and dropping the floor of the turret into the barbette which allowed the greater elevation and range. The guns themselves were upgraded from the 1250 pound 'light' shell to the 1400 pound 'heavy' shell ammunition type. Shell stowage was increased to 150 rounds per gun as it was considered that the monitors were likely to be in action longer per day giving fire support to land units.


Displacement 7,200 tons std, 10,600 tons full load
Length 355 feet
Breadth 88 ft
Draught 14 ft
Machinery 2 shaft Steam turbines, 10,000shp
Speed 16 knots
Range 5,000 miles at 10 knots
Armour 3" side 3" deck, 9" to 4" turret
Armament As completed

2 x 13.5" (1x2)
4 x 4" AA (4x1)
8 x 2pd (2x4)
World War Two

2 x 13.5" (1x2)
4 x 4" DP (4x1)
8 x 2pd (2x4)
12 x 20mm (12x1)
Complement 240 256
Notes All four were lost during WW2:
Skirmisher sunk 1940 off the Dunkirk beaches, by Stuka dive bombers.
Sentinel sunk 1942 in support of the Dieppe landings by JU-88 bombers
Saracen sunk 1943 in support of the Anzio landings by glider bomb.
Scourge sunk 1942 trying to reach Australia through the Lombok Strait, torpedoed by Japanese destroyers.

By 1941 all the remaining ships had received the set of upgrades intended for the class. Radar adorned the mast heads, while the 4" HACS unit and 2 pounder pom poms had also received radar assistance.


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