IJN Torpedo Boats TOMOZURU 1934 and HATSUKARI 1935 building process

PIT-ROAD SkyWave no.W40 model kit of IJN CHIDORI Class Torpedo boats (2 in box) in scale 1/700 waterline series

Part 1.

The kit.

The kit comes with a choice of building 2 ships of the 4 Chidori-Class ships . The TOMOZURU 1935 and HATSUKARI 1945, but firstly I had more interesting in building TOMOZURU as seen in 1934, because of the tragic and thrilling story of the capsize of the ship in bad weather general known as the "Tomozuru incident" this event was the direct cause to the Imperial Japanese Navy's rethinking of how to design and build future warship. Many already existing ships was modified to counter similar fate as TOMOZURU had on the 12th of March 1934. Secondly the kit of HATSUKARI will show the class of boats after the modification (Hull, super structure and armament) in 1935 as seen at the box art above.

Please read about the "Tomozuru incident" at the bottom of this page!

Picture #1:

The ship-class had a heavy armament as in the "as build" configuration in fact they were more small destroyer than torpedo boats they carried two 5 inch turrets -one single and twin - they are not in the box but are on the spur of PIT-ROAD IJN vessel ordinance set. It's a surplus from my other builds and are attached many small SkyWave kit's. I know that the single 5 inch turrets is available, but is not in my inventory at the moment so I decided to "make" one of the twin turret, by cutting it in half, and sanding the inner sides down to just accomplish one gun barrel


Here is the two gun turrets -the single will be located in front of the ship and the twin will be at the quarterdeck at the back. The small protrusions at the right is a small gun director tower in the 5 inch turret (12.7 cm), 50 cal DP, 3 rd Year (1914) has a round shape instead of the sooner type.

The super structure is extended with an extra deck level under the commando bridge, and the additional vents is mounted. The windows is cut open and replaced with Lion Roar PE-set Ladders 1:350. Some windbreakers at the top and sides, is replaced with sheet metal plate (styrene plastic)


Firstly the break water is removed on the front deck -due to a bigger gun (the turrets act as break water itself) also note the two store rooms for spare torpedoes on each side of the funnel. A deck vent is also added on the foredeck. At the freeboard on the hull two bulges is added by a pair of styrene plastic strips they are also seen at picture.#4.

Part 2.

Picture #5:

This picture show the different armament configuration in the "pre incident" and after the modification for the vessels.

Picture #6:

I made new masts of silver tread (0.5mm and 0.3 mm)  note also the higher superstructure on TOMOZURU in front and HATSUKARI in the back.

Picture #7 and #8:

HATSUKARI will have the single closed twin 53cm Torpedo launcher compared to TOMOZURU two open twins 53cm torpedo tubes. The four new cable drums is made of styrene plastic round bars with copper wire as ropes . On the platform just after the searchlight TOMOZURU will have a single 40mm AA gun here will HATSUKARI have a single 7.7 mm AA gun. The red chocolate colored linoleum deck, is painted and hereafter the small strips of brass dividers is shown by scratching (with a scalpel) the lines down to the light colored plastic below. an alternative would be to glue small copper wires upon the lines.

"Tomozuru incident"

Capsize of torpedo boat IJN TOMOZURU

Author KOBAYASHI, Hideo (Yokohama National University)

TOMOZURU was the third vessel of the Chidori Class torpedo boats, and she was not yield to the London Naval Treaty. She had three 12.7cm main guns and four torpedo tubes while her total displacement was less than 600 tons and her maximum speed was approximately 30 knots. Her performance was no less than that of a Second Class Destroyer (Fig.2). TOMOZURU was completed on February 24, 1934 at Maizuru, towed to Sasebo at the end of the month, and joined the 21st torpedo fleet that was organized with her and two other boats of the same type, Chidori and Manazuru. The fleet belonged to the Sasebo Guard squadron whose flagship was light cruiser Tatsuta.

On March 12, 1934, a Japanese torpedo boat capsized. The torpedo boat, named TOMOZURU, was heading north to Sasebo port. However, during the navigation the weather turned to be rough, and TOMOZURU was suddenly inclined by a strong wind and wave. Unfortunately she did not have enough stability against the inclination so finally she capsized, and one hundred officers, including the captain of TOMOZURU, died.
TOMOZURU was one of the Chidori Class torpedo boats. The center of gravity of TOMOZURU was too high due to heavy armaments. As a result, her stability against inclination was insufficient; she was so-called a top-heavy vessel. At the time that the TOMOZURU capsized, waves flooded from oblique behind and she shook violently because the frequencies of the waves and her own body's natural vibration frequency were almost the same.
The responsibility of the over top-heavy structure was on the navy who demanded that the vessel be armed heavily and shipbuilders who accepted the demand. Since then, the Japanese Navy fundamentally rethought the ability of its vessels to maintain stability against waves.

At 1:00 a.m. on March 12, 1934, TOMOZURU following Chidori left the Terashima Channel, Sasebo port and headed for the seas south of Otateshima Island for an approach and attack training against flagship Tatsuta. The three boats kept training despite the rough weather, but as the winds and waves got rougher and rougher the training was suspended at 3:25 a.m. On the way back to Sasebo port, the sway of TOMOZURU intensified and her radio fell down from the desk and died. She contacted the other boats with a light signal, but at 4:12 a.m. TOMOZURU's light signal suddenly ceased.
The two other boats immediately conducted a search for TOMOZURU with their searchlights but they could not find her at that time. Airplanes and vessels from the units of Sasebo Naval Station looked for her, and finally 21st destroyer fleet found drifting TOMOZURU capsized at 1:00 p. m on March 12 (Fig. 1). The flagship Tatsuta managed to tow TOMOZURU to Sasebo, and she reached the port at 7:00 a.m. on March 13.
Some sailors in TOMOZURU were still alive, so air and some liquid food was sent inside the boat. However, because a capsized ship leaks easily, buoyancy was added to TOMOZURU by means of binding her to other ships and cutting off some projections, then she entered the dock at 8:00 p. m. on March 13, and then the seawater was drained out. Finally thirteen sailors were saved and three sailors escaped by themselves before her entering the dock, but the other one hundred sailors, including the captain Lieutenant Okuichi Iwase, died.
Naval officers had assumed that vessels would never capsize, even if the winds or waves were enormously rough. This was why they conducted many hard maneuvers before the denunciation of disarmament treaty so-called 1936's crisis. Thus, this incident completely shocked them. They also had believed that the Japanese newly constructed naval vessels, like TOMOZURU, had the highest performance in the world. They had believed themselves to be successful in overcoming many difficulties in constructing a vessel with a total displacement under 600-tons (disarmament treaties restricted the weight) with the same performance as a destroyer.
An inquiry commission was organized under the control of Admiral Kichisaburo Nomura. After some investigations, they discovered the cause of the capsize, and the chairman submitted a report to the Naval Minister on April 2. The Ministry of the Navy announced that the main cause was the lack of TOMOZURU's stability and that improvements were needed to prevent the lack of the stability like TOMOZURU.

It was obvious that the lack of TOMOZURU's stability caused the capsize, that is to say that bad design led to her capsize. In 1931, a supply plan of auxiliary ships under the restriction of the London Naval Treaty was formed, and the Headquarters presented some requirements for the new ships. But they demanded too heavy armaments for two types of destroyers (1,000-tons and 1,400-tons) in spite of the limited budget and under restriction of the number of destroyers. Although 1,400-tons class destroyers was constructed as Hatsuharu Class, the construction of the 1,000-ton class destroyers was cancelled due to the restriction of the total vessel tonnage possessed, and they decided instead to construct Chidori Class torpedo boats, which were smaller than the 1,000-ton class destroyers and therefore not under the restriction of the treaty. The Chidori Class was intended to be used in place of the Second Class Destroyers in the seas near the Japanese coast. The required performance for the Chidori Class was far greater than that of a torpedo boat in the age of the Russo-Japanese War (1904~05). Requirements included 600 tons basic displacement, 30 knots maximum speed, 3,000 miles range at 14 knots, three 12.7cm main guns and four 53cm torpedo tubes. To reduce the weight, light alloys and welding were widely used, and they cut down the weight of the engines and armaments as much as possible. However, the main gun was the same turret type gun as was used by a destroyer, and some additional equipment was added so that the weight became heavier than they had expected. The freeboards were enlarged in order to improve the vessel's seaworthiness, and livability was better than that of conventional destroyers. In addition to all of this, armament planners of each department in the Headquarters demanded armament having complex and elaborate mechanics. As a result, the center of gravity of the Chidori Class torpedo boats rose, and her basic displacement was held down to only 527 tons.

The first vessel of Chidori Class, named Chidori, was laid keel in October 1931 at Maizuru and launched in April 1933. Originally, shipbuilders of military vessels needed to measure the vessel's weight on the way to construction. They have to know the weight of all the steel material, equipment, armaments and engines before they could equip them from beginning to completion of the construction. However, after the launch, a weight test was carried out, and they found that her weight had become 30 tons heavier and that the center of gravity was 30 cm higher than they expected. They already knew that her center of gravity was relatively high at the planning phase, and so the success of the construction depended on how far they were able to hold down her center of gravity. The department of shipbuilding at Maizuru immediately reported to the Headquarters that Chidori had an unusually high center of gravity and low GM (Magnetic Height) and that her stability was not sufficient. They decided to take measures after her trial run. In 1933 Autumn, Chidori's first operation was held in the seas near Maizuru bay, but when she turned 15 degrees at 28 knots, she rolled more than 30 degrees immediately. They suspended the 35 degrees turning maneuver because it was too dangerous, and the test itself was also cancelled at that time. They worked urgently to develop countermeasures, but many of the countermeasures they did were not effective. In the end, they put bulges on the sides of the vessel, and she succeeded in making the 35 degree turn with a rolling of 20 degree in the reexamination, and the construction of the vessel was completed with hoisting naval ensign on November 1933. As a result of the fast navigation examination during two successive day-and-nights, and the performance examination at the heavy weather such as wind speed of 15 m/s in the Sea of Japan,, they decided that Chidori had sufficient performance for her mission.
TOMOZURU was completed in February 1934, took the same measurements as Chidori, and was brought to Sasebo. She capsized soon after that. When she capsized, she was not carrying many consumables like fuel or water that would have made her center of gravity lower. On the other hand, munitions such as torpedoes were fully equipped, so the situation was much worse than the trial run. As a result, the distance from the surface of the sea to the center of gravity (COG) was over 1.3 m Her stability at the time that she capsized was thought to be less than 50 degrees.

The cause of the capsize of TOMOZURU was the lack of stability that resulted from the so called "Top Heavy Structure". The Navy who demanded excessively heavy armaments and the shipbuilders who accepted these demands were responsible for this incident.

TOMOZURU's capsize forced the Japanese Navy to fundamentally rethink the stability of their vessels. A remodeling plan was made individually for every vessel, and shipbuilders carried out all of the remodeling plans during 1934~35 (Fig.5). The designs of all of the vessels under construction at that time were reconsidered from scratch.

* The torpedo boat TOMOZURU capsized due to her top-heavy structure. Current shipbuilders have valuable experience and confidence in their knowledge of stability. However, we must remember the difficulties of shipbuilders in the past and make the best use of the knowledge that our predecessors gave us.
* The problem of "top-heavy" can destroy structures and organizations. Top-heavy structures are prone to capsize and collapse. Top-heavy organizations are prone to bad management. Individual top-heavy (armchair theorist) may also cause failure.
* The belief of designers in their expertise cannot coexist with an attitude of compromise.

One background issue of TOMOZURU's case was a severe demand for increasing the fighting power of each vessel under the restrictions of the disarmament treaty. In November 1921, the US, the British Empire, France, Italy and Japan formed a disarmament committee in Washington D.C. In this committee, they decided that each nation should restrict the total weight of her vessels. The US, the British Empire, France, Italy and Japan agreed to restrict the total weight of each country's vessels according to the ratios 5, 5, 1.75, 1.75, and 3.
In addition to this disarmament treaty, the London Naval Treaty was concluded in 1930. The treaty established several restrictions concerning submarines and auxiliary ship after many twists and turns. In this treaty, Japan appeared to have partly fulfilled her demands from the US and the British Empire; however, in fact the US gained an advantage over Japan in constructing support vessels under the restriction. Thus, the Japanese naval vessels had to mount large numbers of guns at the cost of their structural strength, which led to the exposure of serious defects. TOMOZURU's capsize and the 4th fleet incident forced us to recognize that inconsistencies between policy and technology lead to unexpected tragedies.

From October 23 to 26 in 1944, the Japanese Navy was soundly defeated by the US in the battle of the Philippine Sea. After the battle, the US 3rd fleet under the control of Admiral Halsey was assigned to attack Leyte Island. The 3rd fleet appeared east of the Philippines and attacked Luzon Airfield after two weeks resting in Ulithi on December 13. Task Group 38 carried out the attack under the control of Vice Admiral McCain.
On December 17, Task Group 38 withdrew to the east to refuel. However, the weather worsened, and they had to suspend the refueling operations soon after the noon. On the morning of December 18, a small but strong typhoon, which weather watcher could not find struck Task Group 38. Radars were blown off, and the commanders were unable to control the vessels or contact with each other with their radios. The wind velocity exceeded 55 m/s. The captains of Destroyers Hull, Monaghan and Spence needed to keep their fuel tanks empty in order to fill them with fuel, and so they did not lower the COG of their vessels by pumping seawater into the tanks. The three unstable destroyers repeated inclined about 70 degrees when the storm was the strongest, and finally all three vessels sank. Some other vessels, including five light air careers, three escort air careers, two heavy cruisers, and eight destroyers, were seriously damaged, and nine vessels were slightly damaged. The number of aircraft that were thrown into the sea or that crashed into each other and burned amounted to no less than 183. About 800 sailors died. Task Group 38 was heavily damaged not by the Japanese Navy, but by a natural disaster.
Perhaps this incident might be caused by lack of their stability even the situation of typhoon and empty fuel tanks was so unfortunate. Of course, the cause of TOMOZURU's capsize is the top secret of the Japanese Navy at the time, and the U.S. Navy could not have known it. In contrast, almost no Japanese vessels capsized since TOMOZURU did. In military field, knowledge of failure cases cannot be shared between nations.



Kindly loan from Mr. KOBAYASHI, Hideo rapport at (Yokohama National University)