Bluebird K4 (Replica)
Blubird K4 was a powerboat commissioned in 1939 by Sir Malcolm Campbell, to rival the Americans' efforts in the fight for the world water speed record. Designed as a three-point hydroplane unlike its predecessor Bluebird K3 which had a single keel. The difference in performance being that at speed a conventional single keel powerboat has a keel with a indent or "step" projecting from the bottom of the hull. At speed, the force on this step is enough to lift the bow upward, reducing the wetted surface area of the hull and thus also the frictional drag. A "three pointer" has a two distinctly separate floats fitted to the front, and a third point at the rear of the hull. When the boat increases in speed, most of the hull lifts out of the water and planes on these three contact points alone. These points being even smaller in area than the planing hull of a monohull hydroplane, have even less drag. Having a broad spacing between the front planing points, the three-pointer is less susceptible to instability caused by small disturbances than is a monohull. However, if the bow lifts beyond its safety margin, the aerodynamic forces on the broad forward area of the hull will cause it to "kite" upwards, leading to a somersault and crash. The craft was built by Vosper & Company as a replacement to Blue Bird K3, which had set three other water speed records for Malcolm Campbell before the K4 was built. It also used the same Rolls-Royce R engine.
On the 19th August 1939 Sir Malcom Campbell sucessfully broke the World Water Speed in K4 on Coniston Water, in the Lake District attained a new record of 141.740 mph (228.108 km/h or 123.168 kn). After the war Malcom Campbell replaced the Rolls-Royce R engine with a de Havilland Goblin turbojet engine but had not make the craft any faster. Sir Malcom Campbell died at his home on New Years Day 1948 Under the terms of his will, Sir Malcolm's possessions, including the record breakers, were auctioned off and Donald was forced to buy them back. K4 was then re-engined with a propellor and one of the previous Rolls-Royce R engines. Donald tried the boat but deemed it too slow, so after another superstructure rebuild and finally structural failure in 1951
It was replaced by the jet-powered K7, in which Donald set several records, then died during a final record attempt in 1967
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Shot 13.06.2016 at the Lakeland Motor Museum, Backbarrow, Cumbria REF 122-130
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