HMAS Van Diemen (BB-1914) CV-1928

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HMAS Van Diemen (ex Agincourt, ex Sultan Osman I, ex Rio de Janeiro) had probably one of the most chequered careers of any battleship even before she was built. Ordered by Brazil, bought by Turkey and seized by Great Britain on the outbreak of war to stop the ship being completed for Turkey. The only ship with 7 main turrets they were named after the days of the week rather than the usual A, B, Q, X, etc. It was felt that the ship may have problems firing full 14 guns broadsides as it may overstress the hull. The ship confounded the pundits by firing full broadsides at Jutland, even though the flash from the 14 guns looked like another battlecruiser exploding... Surviving the war the ship was placed in reserve and was to be discarded under the terms of the Washington Treaty. She was saved by the Australis Navy wanting a ship of approximately 700 feet for converting to an aircraft carrier.



The ship was transferred to the Australis Navy in 1923 and renamed Van Diemen on arrival in Australis. The ship went to the Adelaide dock yards where the ship was stripped of its battleship fittings (to be used in other ships rebuilding later). Work proceeded slowly as news reached Australis of the conversions of the ships in Britain, the Furious types, and the newly built  Hermes, while the US Navy was converting the giant Lexington and Saratoga.

Taking the best parts from all of them the rebuild designers went with the US enclosed bow with the Furious type stern mounting for the flight deck. Only one hangar deck was provided for and aircraft carrying capacity was a maximum of 40, which while only half that of the US and Japanese giants it was enough for the Australis Navies first aircraft carrier trials. Like most early aircraft carriers a lot of 'warship' fitting were kept to the detriment of aircraft carrying capacity. The biggest change was the replacement of the original engines with a completely oil fired propulsion system of 75,000shp which increased the speed from 23 to 26 knots and allowed the ship to operate with the Australis built Queen Elizabeth class battleships. The hull had required bulges to aid stability after the addition of the aircraft handling equipment (flight deck and hangar).

 

The side view shows the long hull required for mounting 7 turrets also made it a good possibility for conversion to an aircraft carrier.
 

1937 and the Van Diemen was taken in hand to remove and plate over the casemate 6" guns that the ship had had for 10 years since completion. All of the navies that had had bigger guns than AA types (5" and below) finally came to the conclusion that they were a waste of time, resources, space and most of all, crew. Nothing further was done to enhance the ship as it had been decided that the Van Diemen would be a training carrier from 1940 onwards.

HMAS Van Diemen at Adelaide dockyards in 1924 undergoing the removal of the weapons and superstructure.

Original drawing, looks better with new parts.

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