U.3 and U.4.
(Completed 1910.)
These two vessels are of the Krupp design, and have a submerged displacement of 300 tons. The horse-power of their heavy-oil surface engines is 600. The electric motors develop 200 H.-P. The surface and submerged speeds are 13 knots and 8 knots respectively. The surface range of action is 1,500 miles, and the armament consists of two bow and one stern tube with five 18-inch torpedoes. Their complement is fifteen officers and men.