HMS Dasher (D37) was a British Royal Navy aircraft carrier, of the Avenger class – converted merchant vessels – and one of the shortest lived escort carriers.
The Avenger-class escort carriers were converted American merchant ships. Their design was based on the U.S. Navy Long Island class (AVG1). To differentiate between the two classes, the Royal Navy ships were prefixed with a 'B' (BAVG). HMS Dasher (BAVG4) was built by the Sun Shipbuilding and Drydock Company. Originally named Rio de Janeiro, she was laid down 11 March 1940, launched on 12 April 1941 and delivered 22 November 1941. She was converted to an escort aircraft carrier in the Tietjen & Long shipyards New Jersey and commissioned into the Royal Navy on 2 July 1942.
Dasher had a complement of 555 men and an overall length of 492.25 feet (150.04 m), a beam of 66.25 feet (20.19 m) and a draught of 23.25 ft (7.09 m). She displaced 8,200 long tons (8,300 t) at normal load and 9,000 long tons (9,100 t) at deep load. Propulsion was provided by four diesel engines connected to one shaft giving 8,500 brake horsepower, which could propel the ship at 16.5 knots (30.6 km/h; 19.0 mph).
Aircraft facilities were a small combined bridge–flight control on the starboard side and above the 410-foot (120 m) long wooden flight deck, one aircraft lift 43 feet (13 m) by 34 feet (10 m), one aircraft catapult and nine arrestor wires. Aircraft could be housed in the 190 feet (58 m) by 47 feet (14 m) half hangar below the flight deck. Armament comprised three single mounted 4 inch dual purpose anti-aircraft guns two forward and one aft and fifteen 20 mm cannon on single or twin mounts. She had the capacity for fifteen aircraft which could be a mixture of Grumman Martlet or Hawker Sea Hurricane fighter aircraft and Fairey Swordfish anti-submarine aircraft.
Dasher started out as the merchantman Rio de Janeiro built by Sun Shipbuilding (Maritime Commission contract (Hull Sun-62)). She was converted at Tietjen & Lang, transferred to the Royal Navy and finally commissioned into RN service as HMS Dasher (D37) on 2 July 1942. She participated in Operation Torch, with her sister HMS Biter, carrying Sea Hurricanes of 804 Naval Air Squadron. After doing some aircraft ferry operations in the Mediterranean, Dasher sailed to the Clyde in March 1943 and, having had her flight-deck lengthened by 42 feet, she embarked Fairey Swordfish aircraft. She escorted one convoy successfully, but shortly after leaving with the second, Dasher suffered engine trouble and turned back. Shortly after getting to the Firth of Clyde on 27 March 1943, she suffered a major internal explosion and sank.
Various possible causes have been suggested, including one of her aircraft crashing onto the flight deck and igniting petrol fumes from leaking tanks. Much of what happened will never be known. Her death toll, 379 out of 528 crewmen, despite rapid response and assistance from ships and rescue craft from Brodick and Lamlash on the Isle of Arran and from Ardrossan and Greenock on the Scottish mainland, was amongst the highest in British home waters. Many escaped from the ship but died of hypothermia or burns suffered when escaped fuel ignited on the water. Most of the dead were buried at Ardrossan or Greenock.
The US blamed it on poor RN petrol handling procedures, the British on bad design of the stowage and handling. There were merits in both arguments but thereafter the stowage on her British operated sister ships was reduced from 75-88,000 gallons down to 36,000 gallons, and the USN reduced theirs also but not as drastically.
The government of the time, eager to avoid damage to morale and anxious to avoid any suggestion of faulty US construction, tried to cover up the sinking. The local media were ordered to make no reference to the tragedy, and the authorities ordered the dead to be buried in a mass unmarked grave. Furious relatives protested and some of the dead were returned to their loved ones for burial. The survivors were ordered not to talk about what happened. This policy subsequently attracted much criticism, and now memorials to those lost exist at both Ardrossan and Brodick. The wreck site lies approximately halfway on the Caledonian MacBrayne ferry route between Ardrossan and Brodick and is a controlled site under the Protection of Military Remains Act.
Teak boards from the flightdeck of HMS Dasher washed up on the beach at Ardrossan in 1999. They were riddled with tubes made by burrowing teredo worms. A section of this wood featured in the "Flotsam and Jetsam" exhibition in the Millennium Dome and another piece is held by the North Ayrshire Heritage Centre in Saltcoats.
There has been speculation that one corpse from the sinking was used during the British deception operation Mincemeat ("The Man Who Never Was"). The case is argued by authors John and Noreen Steele in their book The Secrets of HMS "Dasher".
An archaeological dig was undertaken in October 2012 to ascertain whether there was a mass grave within Ardrossan Cemetery containing bodies from HMS Dasher. This dig showed there was no disturbance to the ground in the area searched.