HM Coastal Motor Boat 4

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HM Coastal Motor Boat 4 was one of a large series of small fast shallow draught vessels used during World War I. She was designed by J I Thornycroft of Hampton, England, ordered in January, 1916, built by them and delivered that summer.

CMB 4 was 45 feet long and 8 ft 6 inches in the beam. She displaced 5 tons drawing 2 ft 9 inches of water. Power was provided by a 1 shaft Thornycroft V-12 petrol engine which developed 275 bhp and achieved a top speed of 24.8 knots. The boat was armed with one 18-inch torpedo tube and four .303 Lewis machine guns. It carried a crew of 3.

The boat, under the command of Lt. Augustus Agar, V.C., was made famous by his daring exploits in the Baltic Sea against the Bolsheviks in 1919 where she operated with her sister ships in activities such as the raid on Kronstadt.[1]

CMB 4 has been preserved at the Imperial War Museum Duxford.