HMS B4

HMS B4 was one of 11 B-class submarines built for the Royal Navy in the first decade of the 20th century. The boat survived the First World War and was sold for scrap in 1919.

Design and description
The B class was an enlarged and improved version of the preceding A class. The submarines had a length of 142 ft overall, a beam of 12 ft and a mean draft of 11 ft. They displaced 287 LT on the surface and 316 LT submerged. The B-class submarines had a crew of two officers and thirteen ratings.

For surface running, the boats were powered by a single 16-cylinder 600 bhp Vickers petrol engine that drove one propeller shaft. When submerged the propeller was driven by a 180 hp electric motor. They could reach 12 kn on the surface and 6.5 kn underwater. On the surface, the B class had a range of 1000 nmi at 8.7 kn.

The boats were armed with two 18-inch (450 mm) torpedo tubes in the bow. They could carry a pair of reload torpedoes, but generally did not as they would have to remove an equal weight of fuel in compensation.

Construction and career
B4 was built by Vickers at their Barrow-in-Furness shipyard, launched on 14 November 1905 and completed on 28 January 1906.

B4 collided with a dredger when entering Portsmouth harbour on 21 July 1906 and was badly damaged as a result, having to be beached before being taken into dry dock for repair. When the war began in 1914, the boat was assigned to defend the Straits of Dover. B4 was sold for breaking up on 1 April 1919 to the Ardrossan Dry Dock Co.