Σάββατο, 14 Μαΐου 2011

YAMATO ΤΟ ΜΕΓΑΛΥΤΕΡΟ ΘΩΡΗΚΤΟ ΜΕΡΟΣ 1ο

The Yamato class were designed in the post Washington Naval Treaty period. The treaty had been extended by the London Naval Treaty of 1930 which limited the signatories to no battleship production before 1937 - the Japanese withdrew from the Treaty at the Second London conference of 1936. Design work on the class began in 1934 and after modifications the design for a 68,000 ton vessel was accepted in March 1937. The Yamato was built at a specially prepared dock at Kure Naval Dockyards beginning on 4 November 1937 . She was launched on 8 August 1940 and commissioned on 16 December 1941 . Originally it was intended that five ships of this class would be built, but the third ship of the class, Shinano , was converted to an aircraft carrier during construction after the defeat at the Battle of Midway , the un-named "Hull Number 111" was scrapped in 1943 when roughly 30% complete, and "Hull Number 797", proposed in the 1942 5th Supplementary Program, was never ordered. Plans for a Super Yamato class, with 50.8 cm (20 inch) guns, provisionally designated as "Hull Number 798" and "Hull Number 799", were abandoned in 1942.

The class was designed to be superior to any ship that the United States was likely to produce - At the time Japanese didn't think Americans could come up with a two-ocean navy, thinking that all ships should pass the Panama-channel. The 46 cm (18.1 inch) main guns were selected over 40.6cm (16 inch) because the width of the Panama Canal would make it impracticable for the U.S. Navy to construct a battleship with the same caliber guns without severe design restrictions or an inadequate defensive arrangement. To further confuse the intelligence agencies of other countries, her main guns were officially named as 16inch Special , and civilians were never notified of the true nature of the guns. Their budgets were also scattered among various projects so that the huge total costs would not be immediately noticeable.

At the Kure Navy Yard where she was built, the construction dock was deepened, the gantry crane capacity was increased to 100 metric tonnes, and part of the dock was roofed over to prevent observation of work.

Arc welding , a relatively new procedure at that time, was used extensively during construction. The lower side-belt armor was used as a strength member of the hull structure. The undulating line of the main deck forward saved structural weight without reducing hull girder strength. Tests of models in a model basin led to the adoption of a semitransom stern and a bulbous bow , which reduced hull resistance by 8%. The ship had one single large rudder (at frame 231), which gave it a small (for a ship of that size) turning circle of 640 meters. By comparison the US Iowa class fast battleship had one of over 800 m. There was also a smaller auxiliary rudder installed (at frame 219) which was virtually useless. The steam turbine power plant was of a relatively low powered design (25 kgf / cm² (2.5 MPa ), 325 °C), and as such, their fuel usage rate was very high. This is a primary reason why they were not used during the Solomons Campaigns and other mid-war operations. There were a total
of 1147 watertight compartments in the ship.

Plans for the Super Yamato Class

During the second world war, almost all of the participating countries had plans for their own super class battleships. These are ships that for whatever reason - usually more pressing wartime programs - were designed but never built, although most were laid down. The intended superclass ships were the Montana class (U.S.), Lion class (UK), 'H' class (Germany), and Sovyetskiy Soyuz class (USSR). However, none of these ships with the possible expception of the Montana class, would have been been a match with Yamato and Musashi even if they were built. While others were planning their superclass ships, the Japanese already had built theirs. However, even further plans for the Super Yamato Class were still done. Warships number 798 and 799 were to be the first Super Yamato class battleships. These were designed in 1941 with construction to begin the following year, with completion estimated for 1946. These ships were also referred to as design A-150. The orders were never placed, so any specifications are rudimentary at best.

The A-150 Super Yamatos were planned with 20 inch main guns, have a maximum speed of 30 knots and maximum displacement of 82.000 tons. Ballistic tests were conducted on the 20-inch gun with an AP round that weighed 4,188 lb. However, no examples of this gun were found after the war. No further preparations were carried out on these ships due to the changing strategic situation after 1942 - in other words, Japanese were starting to run out of resources. With the fate that all other Yamato class ships shared, it was probably good Super Yamatos were never built.

Super Yamato

Illustration of a possible configuration of a Super Yamato Class Battleship with 20 inch guns.

Sources:

Wikipedia (Construction History), Ibiblio.org (Super Yamato), Alt-Naval (Super Yamato illustration)
 
  • Crew: 2700 officers & men,
  • Displacement: 65.027 tonnes empty (inc. 21.266 tonnes of armor), 72.800 tonnes full load
  • Length: 263 meters (256 meters waterline)
  • Beam width: 36, 9 meters
  • Draught: 11 meters
  • Propulsion: 12 Kanpon boilers driving 4 turbines (153.553 horsepower / 110 MW), Four 3 bladed propellers 6m in diameter
  • Speed: 27 knots, 50 km/h
  • Range: 11.500 km at 16 knots
  • Consumption: 70 tonnes of fuel oil in hour at maximum speed. In-f###ng-credible! (Drives your car about 1,1 million kilometers, 30 times around the world - hardly in an hour!)
  •  

    Tower Bridge

    Tower bridge was the ship's control center. Perched at its top, 100 feet (30 meters) above the weather deck, was a rangefinder with state-of-the-art optics. Similiar rangefinders aided targeting at Yamato's three main gun turrets. Their range estimation would have been critical in battles with distant enemy ships. But like Yamato's modern radar and sonar equipment, the rangefinders were little or no help in her final showdown with Allied planes. Yamato veteran Naoyoshi Ishida, who was stationed at the tower bridge, could see the American pilots with his unaided eyes!

    Tower bridge
    Tower bridge illustration

    Tower bridge
    Tower bridge as seen in the model in the Yamato Museum at Kure, Japan.

    Fire Control

    This was Yamato's weakest point compared to its Allied counterships. Yamato was using Mk2 Mod2 gun-control radar with a wavelength of 10cm and power output of 2kW, compared to for example USS Iowa which had 3cm wavelength and 50 kW power output. According to Combinedfleet, Yamato was cabable of shooting accurately to 27.000 yards. Yamato was relying on the information carried from the spotplanes, but was not able to take advantage of the full blind-fire radar fire control, something that the Americans had developed a bit further. Therefore during fast manouvers such as dodging torpedoes, keeping accurate fire up against the enemy targets wasn't easy.

    - Two Type 21, Mod 3 surface and air search radar. One mounted on either side of the 15 meter rangefinder.
    - Two Type 22, Mod 4 Surface search and gunnery radars
    (10cm at 1 Kw). One mounted on either side of the main control tower. (little horns)
    - Two Type 13 air search sets (mounted on either side of her radio-spreader mast aft of the main funnel)


    - Multiple E27 passive radar detection systems (copied German FuMB 1 Metox R.600)

    Although Japanese radar does not compare well with Allied sets of the same period, which were capable of full blindfire without optics, she was not blind either by any measure. Japanese radar was reliable and durable, withstood shock well, mostly because it was cruder, lower power and lacked as many sensitive advanced parts that superior Allied radar had.

    Her radar assisted (not controlled) the finest optical fire control system mounted afloat in WW2, which also had the best night fighting sets. She had both a special analogue computer and electronic firing delay between guns to lesson dispertion and tighten her salvo speads. The whole strategy was to land a tight, massive impact of Type 91 shells just shy of the waterline, to drive the shells through the water and deep into the hull.

    Main battery fire control was exercised by the Type 98 LA system with a director position atop the foretower with a 49ft range-finder and a secondary position aft fitted with a 33ft range-finder. All three 18in turrets also carried 49ft range-finders. Secondary battery control was by means of four directors each equipped with 15ft range-finders, while the 5in AA battery was controlled by the Type 94 HA system, which was reputed to compare very favourably with the USN's Mk 37 DP system.

    Symbol of Glory

    A golden, chrysanthemum-shaped shield more than six feet (two meters) in diameter protruded from ship's bow and was visible for miles. Such "Kikusui" crests, named for a hero and martyr on the 14th century, appeared on only the most important ships of the Imperial Navy - battleships, aircraft carriers, and cruisers. The only other element that was painted gold was the ship's name, which like the crest was apowerful symbol. "Yamato" is a poetic, even mystical synonym for Japan itself.

    Chrysanthemum crest
    Illustration of the chrysanthemum crest
    Chrysanthemum crest
    The chrysanthemum crest as seen in the Yamato model built for the movie Otokotachi no Yamato.

    Flood Control

    Yamato had 1150 watertight compartments, which were meant not only to prevent unwanted flooding but, in some cases, to purposely be flooded. If the ship listed to one side, water could be pumped into compartments on the opposite side. Fuel could also be transferred to tanks on the upward side to help counter the tilt. Midway through Yamato's last battle (see Battles), as the ship listed 15 degrees to port, her crew relied on the system to reduce the tilt to five degrees. But soon all the flood control departments on the starboard were filled, and more torpedo hits flooding on the port side capsized the ship.

    flood control

    Heavy Armor

    The ship's steel armor weighed 23.000 tons, more than 30 percent of Yamato's total weight. The Imperial Navy developed new ways to harden steel and otherwise improve armor technology for the ship. Plated of armor 25 inches (63cm) thick - the heaviest armor ever mounted on a battleship - shielded the turrets of her main guns. The side of the ship could survive the impact of 3000-pound armor piercing projectiles like those shot from the ship's big guns. But Yamato's bow and stern were not as well protected. Most of the torpedoes that ultimately sank her struck there, below the waterline, where she was most vulnerable.

    heavy armour

    Gigantic Hull

    If greatness can be measured by size, Yamato was indeed the greatest battleship ever built. Her giant hull was 863 feet (263 meters) long. Fully loaded Yamato diplaced about 70.000 tons of water, outweighting even the biggest Allied battleships by more than 20 percent. Her hull was so immense that in the mid-1930s no Japanese shipyard could contain it. A dry dock in Kure, the city where Yamato was built, had to be deepened by several feet before construction could begin.

    yamato hull

    Bulbous Bow

    Yamato's vast width posed a challange: her designers had to come up with a hydrodynamic bow to help the ship cut through water. They tested 50 different wax models and struck upon a bow shape that greatly reduced drag at the front of the ship. The bulbous bow, jutting out 10 feet or three meters, creates its own wave that cancels out another wave generated by the main part of the ship. Less hindered by wave resistance, Yamato could reach top speed of nearly 28 knots, 32 miles or 50 kilometers per hour, extraordinary at the time for a ship of her size.

    bow

    150.000 horsepower engine

    A system of four steam turbine engines with a staggering 150.000 horsepower propelled the massive ship. Twelwe boilers, heating steam to 700 degrees F or 370 degrees celcius, fed the four engines which then moved an array of propellers. Each propeller was nearly three times the size of an avarage man! At Yamato's maximum speed of 32 mph or 50 kmh the propulsion system consumed 70 tons of fuel oil every hour. Thats equal to 440 barrels an oil in an hour, 33.000 US dollars in an hour with todays oil prices!

    yamato engine


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