Ostr Class.

(Completed 1904–6.)

These five submarines are of the American Lake type. The Ostr was originally the American Lake Co.’s boat Protector. They have a submerged displacement of 175 tons, are 65 feet in length and 11 feet in breadth. Have petrol engines of 250 H.-P. for surface propulsion and electric motors for use when submerged. Their speed is 11 knots above and 7 knots below. The surface cruising radius is 450 knots at full speed. The armament consists of two bow and one stern tube with four 18-inch Whitehead torpedoes. The special characteristics of the American Lake type will be seen on pages [119–120].