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The WW1 Coastal Motor Boat 

CMB9 was built as a motor torpedo boat for the Royal Navy in 1916

by John Thornycroft at his Hampton Launch Works.


CMBs (Coastal Motor Boats) were experimental torpedo launch vessels, and CMB 9 was one of twelve such vessels ordered by the Admiralty. They were lightweight petrol-driven craft designed to skim across the water, creep up on German destroyers, fire their missiles with deadly accuracy and then race away. On her re-designation as a Distance Control Boat, DCB1 as she became was used to carry out top secret experiments to discover whether unmanned fast patrol boats armed with torpedoes could be controlled remotely from the air and directed towards enemy targets. To this end the vessel was refitted with twin screws, bilge keels, radio masts and a small bridge with wireless controls.

CMB9’s physical strength is due to a large number of ribs placed very close together. She has a stepped hydroplane hull and is of double diagonal mahogany construction. She was originally propelled by a single screw, capable of 40 knots and carried one 18 inch torpedo. Although an attempt was made at some point to convert her into a cabin cruiser, her present owner Robert Morley believes the hull to be some 95 per cent original. Recent work has involved strapping up part of the hull that had sagged to get it back in place, and repairs to the step. The boat’s twin engines which had replaced those fitted when she became a DCB were Leyland 400 diesels dating from the 1950s. New shafts were acquired and new rudders made.

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