Tosa (ship, 1922)
 The Tosa in January 1925 before sinking
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The Tosa ( jap. 土 佐 ) was a battleship of the Japanese Navy and type ship of the Tosa class. It was never fully completed as a result of the Washington Naval Agreement of 1922 and was finally sunk by the Japanese Navy itself in 1925 after several tests and attempts at fire. It was named after the ancient province of Tosa , on Shikoku , in Japan.
Planning and construction
The Tosa was laid on February 16, 1920 in Nagasaki by the Mitsubishi company and, after several delays, was launched on December 18, 1921. The equipment phase that followed was to be completed in July 1922.
One day before the conclusion of the Washington Naval Conference , which ended with the signatures of the representatives on February 6, 1922, the completion of the ship was stopped.
At this point in time, the ship was largely completed, with the exception of the armament and parts of the superstructure.
The Tosa was towed to Kure in August 1922 . It remained there until June 1924, when it was handed over to the Navy's artillery school, which was supposed to carry out various tests on the armor.
Testing
The test phase began on June 6, 1924. The Japanese engineers fixed pressure gauges and small copper tubes (10 × 15 mm) at equal intervals on a scaffolding on the outside of the ship's side wall, in order to later measure the pressure on the deformation the underwater explosions had affected various parts of the hull.
- Test at position 1 (see drawing): A Mk.-1 sea mine , filled with 100 kg of explosives, was detonated in 3.7 meters water depth at the height of frame 57 on the ship's side on the starboard side. The high water pressure and the splinters generated by the explosion damaged around 26 m² of the outer skin of the hull. Seventeen watertight compartments immediately filled with water, five more slowly filled as a result of progressive flooding. In total, the hull took around 995 tn.l. Water and developed a list of 1 ° 54 '. The damage was classified as severe, but not fatal. The ship would have survived the hit. The maximum pressure measured near the explosion point was 7.66 kg / mm² (around 75 N / mm² ).
- Test at position 2 on June 8th: A year 6 torpedo with a 200 kg explosive charge was detonated on the port side at the height of frame 87, around 10 feet (3 meters) above the keel . The explosion destroyed several watertight compartments and tore the torpedo bulkhead from the ship's bottom and bent it inward. Around 24 m² of the ship's side were damaged. The bulkhead in front of the ammunition chamber remained intact. Around 1,008 tn.l. Water absorbed 28 departments ran full. Again, the ship would have survived the hit, even if the shock had partially disabled the observation systems and weapons.
- Test at position 4 on June 9th: A 300 kg explosive charge, similar to that of a year 8 torpedo, was detonated with the torpedo's impact fuse at frame 192 on the starboard side, 10 feet above the keel on the hull . 13.4 m² of the outer skin were damaged. The torpedo bulkhead was badly deformed and the following longitudinal bulkhead also suffered damage. 1,203 tn.l. Water flooded 27 departments. However, the adjacent engine rooms did not fill up. Here, too, the damage did not pose a threat to the Tosa’s ability to swim .
- Test at position 3 on June 12 was a copy of the test from June 9, this time on the port side and with a 350 kg remotely detonated cargo. The affected part of the outer skin was larger, but the result was comparable to the test on June 9 and the warhead was classified as inadequate in use against a ship target with such a structural protection system. The crumple tubes used in the protection system were rated as effective by the engineers, but because of their heavy weight they recommended that they be better used for stronger conventional armor plates. 26 departments ran with around 1,160 t tn.l. Full of water. The maximum pressure measured near the explosion point was 13.41 kg / mm² (around 131.5 N / mm² ).
- Test at location 5 on June 13 consisted of a Year 9 mine detonated about 5 feet above the keel on the starboard wall at frame 87. The energy released by the 150 kg of explosives was largely absorbed by the ship's structural protection system, and there was no damage that could have threatened buoyancy. Around 32 m² of the outer hull was damaged. 726 tn.l. Water flooded 20 departments. The adjacent magazines were not damaged.
- The last test, carried out on June 16, did not affect the underwater hull of the Tosa , but rather a simulation of an internal explosion in the torpedo room , immediately in front of the barbed of tower A in the forecastle. For this purpose, several warheads from Type 8 torpedoes were detonated in the room. The explosion tore up the side walls on both sides of the ship and tore the walls on the port side from the weather deck to just above the waterline. The torn parts of the three steel decks were bent upwards and outwards. The recommendation derived from this was to give the torpedo room massive armor in order to prevent enemy shells from penetrating the room and igniting the torpedoes. If this is not possible, the torpedo room should be closed on one side with a weaker bulkhead in order to direct the energy of an explosion inside the room via the weak bulkhead in a certain direction so that extensive damage could be avoided as far as possible.
The underwater tests mentioned led to the realization that the watertight compartments behind the ship's side that provided structural protection against explosions should not be filled exclusively with air. Compartments filled with air were suitable for breaking down the pressure wave of an explosion, but were almost ineffective against the fragments that an explosion also produced. A liquid, i.e. water or fuel, in tanks appeared to be the most sensible solution for slowing down splinters, but was not universally applicable due to the high weight. As a result, a mix of air and liquid was the best way to effectively protect a ship.
The Tosa was after the conclusion of the underwater tests for classical firing tests with artillery used. A 41 cm shell that was too short hit the water around 25 meters from the ship's side, but continued on its way and hit the side at a depth of 3.5 meters at the height of frame 228. It penetrated the outer hull, a longitudinal bulkhead and the 75 mm thick torpedo bulkhead before detonating in one of the engine rooms. This unexpected result - more severe damage than any previous test - led, on the one hand, to the revision of the principles for underwater protection and, on the other, to the development of new grenades that were supposed to take advantage of this effect.
Sinking
The ship was subjected to further tests shelling and finally, after the middle of January 1925, the instruction for scuttling was granted within a month, cannibalized and prepared for sinking.
After the attempt to sink the ship with explosive charges on February 8th, due to the failure of the detonators, it was finally opened on Monday, February 9th, 1925 in the Bungo Canal, the waterway between Kyūshū and Shikoku , by opening the Bottom valves, brought to sink. Thus the scrapping measures imposed on Japan under the Washington Treaty were fulfilled.
Remarks
All data of the tests were taken from the report S-01-9 of the US Navy of January 31, 1946, conversion as follows:
- ↑ 5.79 m (19 ft ) x 4.57 m (15 ft) = 26.46 m²
- ↑ 6.71 m (22 ft) x 3.66 m (12 ft) = 24.56 m²
- ↑ 5.49 m (18 ft) x 2.44 m (8 ft) = 13.40 m²
- ↑ 5.49 m (18 ft) x 5.79 m (19 ft) = 31.79 m²
The British unit tn.l. ( long ton ) has 1,016 kg, in contrast to the metric ton with 1,000 kg.
literature
- Siegfried Breyer, Alfred Kurti: Battleships and battle cruisers, 1905–1970. Doubleday, Garden City / New York 1973, ISBN 0-385-07247-3 .
- Anthony J. Watts, Brian G. Gordon: Imperial Japanese Navy. The Garden City / Doubleday, 1971, ISBN 0-385-01268-3 .
- William H. Garzke, Robert O. Dulin: Battleships. Axis and neutral - Battleships in World War II. US Naval Institute Press, 1985, ISBN 0-87021-101-3 .
- Reports of the US Naval Technical Mission to Japan, Article 9, S-01-9, Underwater Protection, January 31, 1946.
Web links
Individual evidence
- ^ Battleships: axis and neutral - Battleships in World War II. P. 30.
- ^ Battleships: axis and neutral - Battleships in World War II. P. 21.
- ↑ Eric LaCroix: Japanese Cruisers of the Pacific War. Linton Wells, US Naval Institute Press, 1997, ISBN 0-87021-311-3 , pp. 758, 759.
- ↑ New York Times article, February 12, 1925