Awareness and Design Flaws in the Yamato-Class Battleships' Torpedo Defense System

The Yamato-class battleships, built for the Imperial Japanese Navy (IJN) during World War II, were designed with extensive armor and advanced features for their time. However, like many naval designs, they had known weaknesses, particularly in their torpedo defense system (TDS). This article delves into the IJN's awareness of the weak joint in the ships' TDS as they were being designed and constructed.

The Design and Known Weaknesses

During the design and construction of the Yamato-class battleships, the IJN was aware of some vulnerabilities in the torpedo defense systems. Specifically, the design included a longitudinal bulkhead to protect against torpedo hits. However, the joints between the bulkheads and the outer hull were not as robust as they could have been. This weakness became evident during the Battle of Leyte Gulf in 1944, when the battleship Yamato was damaged by torpedoes.

Despite these design flaws, the focus on heavy armor and firepower often overshadowed the need for a more comprehensive torpedo defense system. The IJN believed that the battleships would be able to withstand significant damage, and this belief influenced their design priorities.

Model Testing and Improvements

It is important to note that the Japanese, like most countries, conducted scale model testing of torpedo defense designs. From 1934 to 1939, they found that the lower belt was not properly rigged, which made the joint a weak point. However, by this time, the design was sufficiently developed that it could not be fundamentally changed.

While there were problems with the TDS, it was not exactly weak. It would still take a charge of 700 to 800 lbs of trinitrotoluene (TNT) equivalent to breach the TDS. Unfortunately for Yamato, she was hit with torpedoes that had torpex warheads, which were equivalent to 900–1200 lbs of TNT. These torpedoes breached the TDS, leading to the sinking of the battleship.

Survivability and Challenges

The Yamato-class battleships were designed to withstand significant damage, especially from torpedo attacks. According to historical records, the ships were able to withstand nine torpedoes hitting on the same side, which would hardly be considered a "weak joint." The real weakness in the defense system was the anti-aircraft armament, which failed completely to protect the ship from air attacks.

No other ships in history have survived as many torpedo hits as Yamato and Musashi, the other member of the Yamato-class. This indicates that while the torpedo defense had its flaws, the battleships were still capable of surviving significant hits under optimal conditions.

In conclusion, while the IJN was aware of the weaknesses in the Yamato-class battleships' torpedo defense system, the design focus on heavy armor and firepower often overshadowed the need for a more comprehensive system. The reliance on these battleships' survivability capabilities, despite the known flaws, highlights the complex nature of naval design and the challenges faced by the IJN during World War II.