Admiralty Floating Dock No. 8 – From Kiel to Corradino
From time immemorial, marine craft requiring painting, repair, careening and demolition have been pulled ashore on sandy beaches. As ships got larger, they were keeled over to port and starboard by shifting ballast to one side. Later, the Chinese invented the first graving dock (grave: from old French greve, shore, the process of cleaning a ship’s bottom by burning off accretions and then tarring). The term ‘graving dock’ continues to be used, albeit superseded by the modern ‘dry dock’.
In the construction of harbour facilities a choice has to be made between graving docks or floating docks. There are compelling arguments for either choice. Floating docks, basically pontoons with sidewalls for stability, are quicker and cheaper to build, and can be sent to foreign naval stations where it is difficult or too costly to build graving docks. However, they are expensive to operate, require a great depth of water for sinking, and are difficult to tow in open seas.
Graving docks take years to build, are more expensive, take up large tracts of land, but require less maintenance, last longer and can easily be augmented by adjacent shore facilities. In Malta, the Admiralty opted for graving docks but there was also a floating pontoon: the Anglo-Maltese Hydraulic Dock inaugurated at Pietà on January 23, 1873.
At the start of World War I, the Admiralty had seven floating docks, six in home waters and one at Bermuda. Officially classed as AFDs (Admiralty Floating Docks) and designated 1 to 7, they were outnumbered by graving docks, and were unkindly considered cumbersome floating furniture that took up valuable harbour waters. Admiralty floating docks were strongly built, often in sections, subsequently joined; whereas merchant ships are docked in light condition, this is not possible with warships.
During World War I, Germany had more floating docks than Britain, including large ones for battleships at the naval bases at Wilhelmshaven and Kiel. In January 1919, the Paris Peace Conference, also known as the Treaty of Versailles, imposed reparations on Germany, to be extracted in cash and kind. On November 21, 1918, 10 days after the armistice, the German High Seas Fleet surrendered and was sailed, under escort, to internment at Scapa Flow, Scotland. Faced with an uncertain future and the likelihood of the once proud fleet being taken over by the victors, Admiral von Reuter scuttled the ships on June 21, sending two-thirds of them to the bottom. At Kiel and Wilhelmshaven there were graving docks and floating docks but the ships they serviced were gone; the German High Seas Fleet had ceased to exist.
The new 65,000-ton dock was 982 feet long; it was the largest in the world, and could take HMS Hood, at 860 feet the longest and largest warship in the Royal Navy
The reduction in number and size of major warships agreed at the 1922 Washington Naval Conference lessened the need for additional dockyard facilities, but the Admiralty urgently required to upgrade its naval bases in Singapore and Malta. A new graving dock was being built at Singapore. In Malta a new dock was needed for battleships with a wider beam, and aircraft carriers. However, there was neither the space nor the appetite for a graving dock in Grand Harbour, which would also take years to complete.
With war reparations in mind, three large German Navy floating docks were examined at Wilhelmshaven and Kiel. No. 23 at Wilhelmshaven, built in 1914, was in poor condition. No. VII at Kiel was built in 1911, and was earmarked for Singapore. The remaining dock, No. VIII, was built by Howaldtswerke at Kiel in 1917. It was allocated to Malta.
The Malta dock, designated AFD8, arrived at Sheerness, England, under tow from Kiel in April 1921. Construction on a new mid-section began at Chatham Dockyard on April 2, 1923; it was completed in May 1925. The original dock, made up of two sections, left Sheerness for Malta on June 1, 1925, towed by six Admiralty tugs: Retort, Resolve, Roysterer, St Day, St Clears and St Mellons.
The huge structure was towed at an average speed of 3.8 knots, and arrived in Grand Harbour on June 27. The manoeuvre was witnessed by thousands who had never before seen a floating dock. Both Barriera Wharf and Bighi Bay were cleared of ships during the operation. The tugs then returned to England for the new, Chatham-built mid-section. This left Sheerness on August 1, towed by Retort, Resolve, St Clears, St Mellons and St Kitts, arriving at Malta on August 22.
The Kiel dock was separated and the new mid-section was inserted in between at the Dockyard. The work was completed by October 17. The new 65,000-ton dock was now 982 feet long; it was the largest in the world, and could take HMS Hood, at 860 feet the longest and largest warship in the Royal Navy.
It was then berthed off Magazine and Laboratory wharves, below Kordin (Corradino Heights). Here was the required depth of water for sinking the dock during lifting operations. Months of sinking tests followed.
The several compartments of a floating dock have separate pump rooms; docking and undocking require skilful planning and expertise to avoid serious incidents, such as occurred on August 8, 1944, when HMS Valiant entered AFD 23 for docking at Trincomalee, Ceylon.
The battleship displaced 39,040 tons, her 71.8 tons exceeding the allowable 62.5 tons per foot run on the keel blocks. This fact, coupled with improper pumping sequences, led to buckling between sections 5 and 6; the dock sank at moorings, the ship was damaged, and salvage proved to be extremely difficult and lengthy.
(To be concluded)