Chapter 14 - Our U-Boats and their Method of Warfare
IN the year 1916, up to the time of the Battle of the Skagerrak, the following additions had been made to the U-boat fleet: 38 large U-boats, 7 large submarine minelayers, 34 U-B-boats. Two large submarine minelayers, 3 U-B-boats and 3 U-C-boats had still to undergo steam trials; 53 large U-boats, 10 large submarine mine-layers, 27 U-B-boats and 66 U-C-boats were under construction. Since the outbreak of war we had lost 21 large U-boats, 1 large submarine minelayer, 6 U-B-boats, 7 U-C-boats, and 2 U-B-boats had been handed over to the Bulgarian Government. The distribution of all the U-boats was so arranged that half were under the orders of the Admirals of the Fleet, and of the rest one half were stationed in the Mediterranean, while the other half, the last quarter, were assigned to the Naval Corps in Flanders. For the sake of quick construction the new types of so-called "U-B"-boats and "U-C"-boats had been introduced, in addition to the main type of large U-boats similar to "U 19," the first one fitted with Diesel engines.
The chief characteristics of the different types were as follows: "U 19," surface displacement, 650 tons; highest speed on the surface, 12 knots; under water, 9 knots; number of torpedoes, 9, of 50 cm. calibre. Improvements were made in the type. From "U40" onwards the displacement was raised first to 700 tons, and from "U 80" onwards to 800 tons, the speed was raised to 17 knots on the surface, the number of torpedoes increased to 12, and from "U90" onwards to 16. The torpedo of 50 cm. calibre had an explosive charge of 200 kilos. The first large submarine minelayers were not armed with torpedoes. They had a displacement of 760 tons, a surface speed of 9.5 knots, and under water 7.5 knots; they carried 34 to 36 mines.
Of the U-B-boats, at first a small number with a displacement of 125 tons was built for use in Flanders, with four torpedoes, speed of 8.5 knots on the surface and 5.5 knots under water. The U-B-boat was then enlarged to 500 tons, with a speed on the surface of 12.5 knots and of 7 under water.
The U-C-boats were of a type designed both for minelaying and firing torpedoes. At first only a small number of these was built, with a displacement of 150 tons; ultimately the boats had a displacement of 400 tons, speed of n knots on the surface and 6.5 under water. They carried 18 mines and could take four torpedoes.
At the beginning the U-boats were armed with one 5 cm. gun as a defence against enemy submarines. But as their use was developed in the war, such various demands were made upon them that their armament had to be increased. One or two guns of 8.8 cm. were placed on the U-boats, U-B-boats, and the U-C-boats; the submarine cruisers were in part armed with a gun of 15 cm. calibre.
The majority of the large U-boats was assigned to the Fleet for use in the blockaded area west of England. The length of their trips was 21 to 28 days, but this was also dependent on the amount of ammunition used when the boats had found a favourable opportunity to fire their torpedoes soon after leaving port. The big minelayers were also under the command of the Fleet, and could be sent on distant expeditions - to the White Sea or to the Mediterranean.
The U-B-boats, being rather smaller, had proved to be very handy and quickly submersible, although they could not remain so long at sea. They were, therefore, mainly assigned to the base in Flanders, as were the U-C-boats, of which a small number, however, was at the disposal of the Fleet and used for laying mines on the east coast of England. The distribution of the boats among the various bases was carried out according to the facilities the latter had for repairing the boats on their return from expeditions. The large amount of technical apparatus in a U-boat required very careful overhauling and repair on her return from an expedition; also the damage due to the voyage or to enemy attacks had to be repaired. Generally speaking, after four weeks at sea a boat would need to lie in the dockyard for the same length of time for repairs. The Imperial dockyard at Wilhelmshaven had been enlarged and was the chief place to which the U-boats of the Fleet were sent for repair. The docks at Kiel and Danzig were needed for other purposes; the bases at Zeebrugge and Pola were used at first mainly for overhauling the boats. Until these dockyards had been altered so as to be able to undertake more extensive work the boats which belonged there had to return home for important repairs.
