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U.S. Navy's Semi-Submerged Torpedo Boat, 1943
During World War Two the U.S. Navy was not known for its unconventional thinking. While the Italians and British quickly embraced novel means of sneak attacks, America focused on overwhelming conventional forces. Yet that doesn't mean that everyone within the U.S. military thought that way; there were various unconventional naval craft being built. One such craft was a semi-submersible torpedo boat.
Photos of a 'semi-submersible torpedo craft', named only C-25465, appear on the Naval History and Heritage Command website. They indicate that it was built at the Robert Jacob, Inc., Shipyard, City Island, New York, in around March 1943.
Little else is known about the craft and it almost certainly didn't enter service. The value of torpedo boats was clear, and the U.S. Navy developed the successful PT series. These operated in open water as well as ports and there seems to have been no inclination to switch to a more stealthy form of torpedo boat.
The design is interesting though. It has two torpedoes carried in the lower hull shooting forward through hatches in the bow. The hatches appear watertight and there are lifting chines along the hull showing that the boat could plane (lift out of the water) for high speed transit. It could then semi-submerge so that the deck was awash. This was likely achieved by flooding floatation tanks either side of the torpedoes. We can guess that the torpedo hatches would have leaked, meaning that it would need pumping and that the torpedoes would be exposed to sea water for extended periods.
Shearer Torpedo Boat?
The design is reminiscent of some proposals by American inventor William Baldwin Shearer of the International Torpedo Boat Corp around 1917-23. Shearer was born in Philadelphia, and served with the U.S. Navy in the Spanish-American War (possibly aboard USS New Orleans. When World War One broke out he sailed to England and offered his services to the Admiralty, before returning to America and serving again with the U.S. Navy throughout the war.
Shearer conceived of a sneak craft which could make an attack on the German submarine base at Zeebrugge. He proposed a semi-submerged torpedo boat to the Department of the Navy in around 1917, but it took years to get built.
Various patents were filed showing a low profile vessel which run awash with a torpedo in the bow similar to this later design. The earlier designs had a single torpedo in a trough between flotation tanks, and a single crewman aft. Power was limited so speed would have been quite slow. At least two vessels, the 'Sea Hornet-I / II' torpedo boat, were built. These were similar in concept to the patents but differed in final form. The first reportedly passed trials but, coming just after the war, was not adopted. Amusingly the second vessel, Sea Hornet II, was later renamed 'Com-an-Go' and used as a prohibition-era smuggling vessel .
We can speculate that the later design was also from, or at least influenced by, William Baldwin Shearer. Naval-History.net notes that he also submitted a proposal in 1942, and this might be that, but I cannot confirm at this point.
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