British B Class Submarine - Design and Description

Design and Description

The B-class boats were similar in design to the preceding A class and intended for coastal patrol work. The boats had a petrol engine for surface propulsion and batteries for underwater propulsion. The design was intended to overcome the limitations of speed, endurance and seakeeping that affected the boats of the A class, and the boats were substantially larger than the earlier class. The B-class submarines were 142 feet 2.5 inches (43.3 m) long overall. They had a beam of 12 feet 7 inches (3.8 m) and a draught of 11 feet 2 inches (3.4 m). They displaced 287 long tons (292 t) on the surface and 316 long tons (321 t) submerged. The boats were over 40 feet (12.2 m) longer, slightly wider, and displaced more than 120 long tons (120 t) more than the older boats. Their additional size increased their buoyancy and made them far less liable to unexpectedly plunge beneath the surface in bad weather. The addition of a deck casing above the hull also improved their seakeeping abilities.

Diving planes were initially only fitted at the stern, but additional planes were mounted on the conning tower during construction of B1, B2, and B3; B4 was not fitted with them and it is uncertain if the remaining boats received them during construction. These greatly improved the boats' depth-keeping, surfacing and diving abilities compared to the A-class boats. These were later exchanged for bow planes; the last boat to receive them was B6, which did not get hers until January 1916. The B-class submarines lacked any internal bulkheads which exposed the crew to the petrol engine's exhaust fumes. In fact mice were used to detect any concentrations of carbon monoxide inside the hull. Ventilation was provided for the batteries, but none for the crew's living area. No accommodations were provided for the crew and they were forced to improvise while at sea. In recognition of this issue, the crew's endurance was only expected to be four days during the summer and three days during the winter.

The submarines' hulls were tested to a nominal depth of 100 feet (30.5 m) by filling the hull with water and subjecting it to a pressure of 35 psi (241 kPa; 2 kgf/cm2), but the maximum operational depth was considered to be 50 feet (15.2 m). Nonetheless several boats safely dived to 95 feet (29.0 m) during World War I. It took about three minutes to dive the boat due to the shape of the boat and that it could dive out of control if water was pumped into the ballast tanks too quickly. Submerged endurance was officially considered to be 10 hours, but several boats were submerged for 16 hours during the war.