Post by miletus12 on Dec 20, 2021 16:31:31 GMT
One finds the weirdest stuff when one looks at a topic.
Yuzura Hiraga and Keiji Fukuda, the designers of the Yamato class created this debacle of a torpedo defense system.
Explanation. What the two designers tried to do, was create an external "bulge" system of voids and ballasts that would provide the 5.5 meter minimum adjudged adequate for the offset needed to protect the armored raft float bubble. The problem comes at the joint. If the torpedo hits at the V-shaped joint where the bulge joins the inclined belt, the water hammer is amplified immensely. The proof of voids and cells in a "test" where the elements are not modeled to exactly duplicate the conditions and parameters of the actual TDS at that V will result in false predictive results.
It comes as no surprise, that this V joint acted like a zipper, when US torpedoes hit it.
In the case of Musashi and Yamato, theoretically proofed against 400 kilograms of TNT effect, the ships' TDS unzipped from the inclined belts, from the effects of puny 200 kg TNT effect warheads, The water hammers also shattered the stiff back plate of the lower belt armor. In the case of Musashi, a half dozen flood intrusions forced her to attempt to beach, but she sank. Yamato appears to have caught fire internally from a belt strike just ahead of number three main armament turret. The flame path reached a magazine adjacent to number three turret and about 400 tonnes of propellant exploded. Shinano took between three and four submarine torpedo hits. Her loss has been blamed on watertight doors not being fitted and an incompetent crew, but one wonders if those three or four torpedoes just might have been enough even if she had been buttoned up and her crew was properly damage control trained?
To answer the opening question, though, of how Musashi was lost, one can suggest that it only takes one fundamental simple mistake to cost a complex system to fail. In the case of the Yamatos, it was that V notch where the torpedo defense system seamed into the inclined belt. What makes it worse is that there were TWO such seams in the Yamato class.
One can only wonder at the incredible oversight that missed this engineering flawed solution, not once, but twice?
Yuzura Hiraga and Keiji Fukuda, the designers of the Yamato class created this debacle of a torpedo defense system.
Damage from the initial kinetic energy of incoming shellfire could best be minimized by thick armor plate with a hardened exterior, hut such a system could never hope to defeat a torpedo's explosive charge of several hundred pounds detonating in direct contact with it and amplified by the surrounding water. Matters could actually he made worse since the heavy armor tended to fracture and the broken shards could rip deep into the hull. Volume was the best protection against torpedoes since it allowed for the expansion of the explosive gases while the remaining force rapidly dissipated with distance. There was never enough internal volume in a hull to provide much space for this and designers generally had to be satisfied with providing the minimum. In the case of Yamato the constraints were severe despite her great beam because of her chosen machinery layout. This was exacerbated by the choice of a reliable but bulky set of boilers, which ran at relatively low pressure. They were used because replacement beneath the 200mm armored deck would have proved extremely difficult hut the corollary was a narrower torpedo defense.
The width of this around her machinery spaces was on average 5.l m, and was narrower than that of almost all her contemporaries in other navies despite her displacing considerably more. Two examples will suffice to illustrate this. The American North Carolina, on a displacement calculated in a comparable manner at 45,298 tons, had a system 5.6m deep, while the German Scharnhorst on only 35,398 tons still managed a depth of 5.4m. For Yamato, it was therefore essential that within the comparatively narrow space remaining the best possible arrangement was used.
In order to counter a torpedo explosion, a space outside the true hull was required which would be strong enough to detonate the weapon well away from a stronger yet flexible main bulkhead beneath. The Japanese developed empirical formulae to determine the thickness of protective bulkheads and bulges based on tests with models and full scale systems. Once established they were then used with much confidence and for Yamato the main bulkhead was to be 75mm ducol steel. When a full scale plate of this was duly tested in 1939 against a blast of 400kg of TNT, the results were encouraging since it did not split open although its watertight integrity was lost.
The width of this around her machinery spaces was on average 5.l m, and was narrower than that of almost all her contemporaries in other navies despite her displacing considerably more. Two examples will suffice to illustrate this. The American North Carolina, on a displacement calculated in a comparable manner at 45,298 tons, had a system 5.6m deep, while the German Scharnhorst on only 35,398 tons still managed a depth of 5.4m. For Yamato, it was therefore essential that within the comparatively narrow space remaining the best possible arrangement was used.
In order to counter a torpedo explosion, a space outside the true hull was required which would be strong enough to detonate the weapon well away from a stronger yet flexible main bulkhead beneath. The Japanese developed empirical formulae to determine the thickness of protective bulkheads and bulges based on tests with models and full scale systems. Once established they were then used with much confidence and for Yamato the main bulkhead was to be 75mm ducol steel. When a full scale plate of this was duly tested in 1939 against a blast of 400kg of TNT, the results were encouraging since it did not split open although its watertight integrity was lost.
It comes as no surprise, that this V joint acted like a zipper, when US torpedoes hit it.
In the case of Musashi and Yamato, theoretically proofed against 400 kilograms of TNT effect, the ships' TDS unzipped from the inclined belts, from the effects of puny 200 kg TNT effect warheads, The water hammers also shattered the stiff back plate of the lower belt armor. In the case of Musashi, a half dozen flood intrusions forced her to attempt to beach, but she sank. Yamato appears to have caught fire internally from a belt strike just ahead of number three main armament turret. The flame path reached a magazine adjacent to number three turret and about 400 tonnes of propellant exploded. Shinano took between three and four submarine torpedo hits. Her loss has been blamed on watertight doors not being fitted and an incompetent crew, but one wonders if those three or four torpedoes just might have been enough even if she had been buttoned up and her crew was properly damage control trained?
To answer the opening question, though, of how Musashi was lost, one can suggest that it only takes one fundamental simple mistake to cost a complex system to fail. In the case of the Yamatos, it was that V notch where the torpedo defense system seamed into the inclined belt. What makes it worse is that there were TWO such seams in the Yamato class.
One can only wonder at the incredible oversight that missed this engineering flawed solution, not once, but twice?
