PT-boat

A PT boat (short for Patrol Torpedo boat) was a torpedo-armed fast attack craft used by the United States Navy in World War II. It was small, fast, and inexpensive to build, valued for its maneuverability and speed but hampered at the beginning of the war by ineffective torpedoes, limited armament, and comparatively fragile construction that limited some of the variants to coastal waters.

The PT boat was very different from the first generation of torpedo boat, which had been developed at the end of the 19th century and featured a "displacement" hull. These first generation torpedo boats rode low in the water, displaced up to 300 tons, and had a top speed of 25 to 27 kn (29 to 31 mph; 46 to 50 km/h). During World War I the US and UK developed the first high-performance motor torpedo boats (often with top speeds over 40 kn (46 mph; 74 km/h)) and corresponding torpedo tactics, but these projects were all quickly disbanded with the Armistice. World War II PT boats continued to exploit some of the advances in planing hull design borrowed from offshore powerboat racing and were able to grow in size due to advancements in engine technology.

During World War II, PT boats engaged enemy warships, transports, tankers, barges, and sampans. As gunboats they could be effective against enemy small craft, especially armored barges used by the Japanese for inter-island transport. Several saw service with the Philippine Navy, where they were named "Q-boats" most probably after President Manuel L. Quezon

Primary anti-ship armament was four 2,600 pound (1,179 kg) Mark 8 torpedoes. Launched by 21-inch Mark 18 (530 mm) torpedo tubes, each bore a 466-pound (211 kg) TNT warhead and had a range of 16,000 yards (14,630 m) at 36 knots (66 km/h). Two twin M2 .50 cal (12.7 mm) machine guns were mounted for anti-aircraft defense and general fire support. Some boats shipped a 20 mm Oerlikon cannon.

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Wikipedia