Failure Knowledge Database / 100 Selected Cases

Capsize of torpedo boat Tomozuru
March 12nd, 1934, Seas near Sasebo port, Nagasaki prefecture
KOBAYASHI, Hideo (Tokyo Institute of Technology)(Summary)
On Marc h 12nd, 1 934, a J apanese tor pedo boat capsized. Th e t orpedo b oat, named T omozuru, w asheading no rth to Sasebo port. Ho wever, du ring t he navigation the weat her tu rned to be rou gh, andTomozuru was su ddenly inclined by a st rong win d an d wav e. Un fortunately sh e di d no t hav e eno ugh
stability against the inclination so finally she capsized, and one hundred officers, including the captain ofTomozuru, died.
Tomozuru was one of the Chidori Class torpedo boats. The center of gravity of Tomozuru was too highdue to heavy armaments. As a result, her stability against inclination was insufficient; she was so-called a
top-heavy ves sel. A t t he time that t he Tomozuru c apsized, w aves fl ooded from obli que b ehind and s heshook violently because the frequencies of the waves and her own body's natural vibration frequency were
almost the same.
The res ponsibility of t he o ver t op-heavy struc ture w as on th e cr ewmembers w ho dem anded th at t hevessel be armed heav ily and s hipbuilders w ho ac cepted t he demand. Sin ce t hen, the J apanese N avy
fundamentally rethought the ability of its vessels to maintain stability against waves.
1. Component
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 lessthan 600 tons and her maximum speed was approximately 30 knots. Her performance was no less than thatof a Second Class Destroyer (Fig. 1). Tomozuru was completed on February 24th, 1934 at Maizuru, towed
to Sasebo at the end of the month, and joined the 21st torpedo fleet that was organized with her and twoother bo ats of the sam e ty pe, Ch idori an d Ma nazuru. The flee t be longed to the S asebo G uard squadron
whose flagship was light cruiser Tatsuta.
2. Event
At 1 :00 a.m. on Marc h 1 2nd, 1934, Tomozuru fo llowing Ch idori lef t t he Terashima Chan nel, 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 sus pended at 3:25 a.m. On the way ba ck t o Sas ebo port, t he sway ofTomozuru intensified and her radio fell down from the desk and died. She contacted the other boats with alight signal, but at 4:12 a.m. Tomozuru's light signal suddenly ceased.
The two othe r boats im mediately conducte d a se arch for Tomozuru wi th t heir s earchlights but t hey
could not find her at that time. Airplanes and vessels from the units of Sasebo Naval Station looked for her,1

Failure Knowledge Database / 100 Selected Cases

and finally 21st destroyer fleet found drifting Tomozuru capsized at 1:00 p.m. on March 12nd. The flagship
Tatsuta managed to tow Tomozuru to Sasebo, and she reached the port at 7:00 a.m. on March 13rd.
Some sailors in Tomozuru were stil l alive, s o air a nd som e liq uid fo od was s ent ins ide t he bo at.
However, because a capsized ship leaks easily, buoyancy was adde dto Tomozuru by means of bindi ng

her to other ships and cutting off some projections, then she entered the dock at 8:00 p.m. on March 13rd,
and then the seawater was drained ou t. Finally th irteen sai lors were save d a nd th ree sai lors es caped bythemselves before her entering the dock, but the other one hundred sailors, including the captain Lieutenant
Okuichi Iwase, died.
Naval officers had ass umed th at v essels w ould never capsiz e, e ven if t he w inds or w aves w ere
enormously rou gh. This w as w hy they co nducted many hard m aneuvers before t he denunciation ofdisarmament treaty so-cal led 19 36's crisis. Thus, t his i ncident c ompletely sh ocked them . They also h ad
believed that the Japanese newly constructed naval vessels, like Tomozuru, had the highest performance inthe 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 A dmiral Kichisaburo Nomura. After someinvestigations, they discovered the cause of the capsize, and the chairman submitted a re port 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.
3. Course
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 andunder restri ction of t he number of destr oyers. A lthough 1,400-tons class destroyers w as co nstructed 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, whichwere 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 ageof t he Russo-Japanese W ar (19 04~05). Requirements in cluded 600 t ons b asic displacement, 3 0 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 adestroyer, and so me additi onal equipment was adde d so th at the weig ht became hea vier th an they had
expected. The freeboards w ere enlarged in order t o improve the vessel's seaworthiness, and livability wasbetter than that of conventional destroyers. In addition to all of this, armament planners of each department

2Failure Knowledge Database / 100 Selected Casesin the Headquarters demanded armament having c omplex and elaborate mechanics. As a result , the centerof gravity of t he Chidori Class torpedo boats rose, and her bas ic displacement was held down to only 527
tons.
The first vessel of C hidori Class, named Ch idori, w as lai d k eel in O ctober 1 931 a t Ma izuru an dlaunched in April 1933. Originally, shipbuilders of military vessels needed to measure the vessel's weighton 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 andthat 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 abl e t o hold down her cent er of gravity. T he department of s hipbuilding at Mai zuru im mediately
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 te st itself was a lso cancelled at that t ime. They worked urgently todevelop countermeasures, but many of the countermeasures they did were not effective. In the end, they put
bulges o n t he sides of the vessel, a nd sh e suc ceeded in m aking the 35 d egree t urn w ith a rol ling of 20
degree in the reexamination, and the construction of the vessel was completed with hoisting naval ensign
on November 1933. As a r esult of the fast navigation examination during two successive day-and-nights,
and the performance examination at the heavy weather such as w ind 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 C hidori, and was brought
to Sasebo. She capsized soon aft er that. When she capsized, she w as not carrying many consumables likefuel or w ater tha t w ould h ave m ade her cen ter of gra vity l ower. O n th e ot her h and, munitions such as
torpedoes were fully equipped, so the situation was much worse than the trial run. As a result, the distancefrom the surface of t he 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.
4. Cause
The c ause of the capsize of Tomozuru was the lack of stabi lity tha t resulted from the s o ca lled "TopHeavy S tructure". The crewmembers who dem anded ex cessively hea vy arm aments a nd the ship builders
who accepted these demands were responsible for this incident.
5. Immediate Action
On April 5th, 1934, a special investigative committee of the vessels' performance was formed under thecontrol of Ad miral Kanji K ato. Its m embers consisted of crewmembers and shipbuilders, and Dr. Hiraga,
Professor of the University of Tokyo, was added to the committee as a temporary employee of the JapaneseNavy.
3Failure Knowledge Database / 100 Selected Cases

The c ommittee i nvestigated the ca use of T omozuru's capsi ze e xhaustively. T hey looked throughliterature a nd ot her m aterials rel ated to stab ility of all the pre vious vessels i nside a nd o utside a ndinvestigated the current situation of all the vessels of the Japanese Navy. Figure 2 illustrates the principles
that govern a vessel's stability using the analogy of a self-righting "daruma" doll. A high Center of Gravity(COG) means a large distance from the surface of the se a to the COG, and a decrease of GM, resulting in anarrow ran ge of sta bility. F urthermore, winds af fect a vessel m ore severe ly if the dis placement is sm all(although the small displacement was inevitable in th e case of Tomozuru because of the limitations of the
London Naval Treaty). In addition, she had far too many armaments for her displacement. The total weightof all guns, torpedoes and other electronic weapons amounted to 167 tons, which was almost 24 percent ofher total displacement. This percentage was much larger than that of the former destroyer Mutsuki, whose
weight of ar maments was 178

tons an d co ntributed to o nly 10 perce nt of t he t otal dis placement.

Therefore, Tomozuru had as much armament as a First Class Destroyer whose to tal displacement was 2.5
times larger. Even the Spe cial Hubuki Class Destroyer, which was kn own as a revo lutionary heavy armed
destroyer, had an armament weight of 302 tons, which was only 13.7 percent of the total displacement. .
It is clear that Chidori Class had an extraordinarily large weight of heavy armaments. Thus her center ofgravity was unusually high and her stability was too low. The capsize was triggered by the situation that thefrequencies of the waves were similar to the vessel's natural vibration frequency, which causes the vessel toroll terribly.
Of course, th e ca psize c ould h ave b een a voided if the crew's navi gation ski ll was better, but m ilitary
ships have to carry out their missions under the not so extraordinary rough weather.
In May 1895, the Japanese Navy's No.16 torpedo boat (54 tons) capsized due to the rough weather inthe seas near Penghu Island, Taiwan. The cause of this capsize was also lack of her stability.
In December 1932, the Second Class Destroyer Sawarabi (820 tons) capsized and went down due to therough weather during her cruise in the seas near Taiwan. Sawarabi's incident occurred only a year before
Tomozuru's capsize so investigations should have been more discreet. All the m ore than twenty destroyersof the same class as Saw arabi had not been pointed out that they were bad at stability for fiftee n years, sothey thought that the cause of the capsize was overloading on her deck, instead of her stability.
Crewmembers also d emanded unreasonable am ounts of arm ament for many oth er vesse ls, and t heshipbuilders w ho desi gned Tomozuru al so accepted all of th ose d emands. A s a result, many vessels
designed by the shipbuilders, namely the Air Career R yujo, Soryu, the Submarine Depot Ship Taigei, theMogami Class Cruis ers a nd s ome ot her minesweepers, ca ble re pairing shi ps, d estroyers an d s ubmarine
chasers, also had high COG's. Moreover, the tendency towards high COG's increased for later vessels. The
Committee urgently had to alter every vessel including existing or under construction

recognized that its

stability w as not sufficient. For v essels t hat h ad n ot b egan construction, th e committee had t o determine
expected standard of the vessel's stability and change the construction plan accordingly. However, since theadversary for the vessel's stability is nature, and the vessel's situation varies depending on the environment,
theoretical marine engineering at that time could not determine the standard. After extensive research, they
concluded that it was impossible to determine the standard at last, but that in order to avoid another incident

4Failure Knowledge Database / 100 Selected Cases

like Tomozuru, they should determine a r ough standard. Therefore, a list was m ade based on t he vesselsthat were thought to have good stability. In particular, the list treated GM as the most important quantitativevalue, and it gav e stric t stan dards for the rat io between t he s ubmerged are a of a vesse l and thenon-submerged area. It also designated a lightest weight limit for each type of vessel and st ipulated that if
the wei ght di d not m eet the l imit, bal lasts m ust be added. A mechanical device that fil ls t he vessel wi th
seawater automatically as the vessel's fuel is consumed was equipped on some vessels.
Furthermore, the committee established the following rules for the vessel's stability:(1) The weight of a vessel m ust be calculated and m easured as a ccurately as possibl e, and any w eight
difference between the calculated and measured values must be clarified as quickly as possible.
(2) If a new device is added to an existing vessel, the new COG and weight gain must be calculated. If the
new COG is too high, existing devices of the vessel should be either removed or shifted in order to in
return the COG to a value that satisfies the vessel's stability.
(3) When the construction or refit of the vessel is completed, devices must be loaded at the expected place,and performance examinations have to be m ade with the vessel's weight and COG agre eing with thecompleted co ndition. Appointed member of t he performance consi deration c ommittee, discusses
strictly whether the vessel has enough performance to her missions.
In addition to these rules, some other measures were given for existing vessels:(1) Unnecessary arm aments an d eq uipment w ere rem oved. The m ain arm aments in s ome vessels were
removed or downsized.
(2) Ballast or a ballast keel was put at the bottom of some vesses.
(3) The width of some vessels was changed, and some vessels were equipped with bulges.
(4) A seawater ballast tank was equipped on some vessels.
Moreover, bridges or funnels were shortened or downsized.
The C hidori Class T orpedo Bo ats a nd the H atsuharu Class Destroyers were investigat ed es peciallycarefully, and some of the main armaments were removed or changed. The Tone Class Cruisers, Air Career
Souryu and Shiratsuyu Class Destroyers were fundamentally rethought in terms of t heir stability, and four
Chidori Class torpedo boats were thoroughly remodeled. From the f ifth, the vessels were redesigned fromthe start, and the newly constructed torpedo boat was categorized as Kou Class (Fig.3).
With Tomozuru's capsize a s a tri gger, the Japanes e Navy fun damentally re thought th e st ability of i ts
vessels. I n 19 34 a nd 1935, all t he rec onstructions of vessels w ere conducted at every na val ( or so me
private) s hipyard. As a res ult of this re modeling, wh ile som e vessels had t o decrease their velocity orarmament, t he sta bility of all vesse ls wa s dram atically im proved. The fu ndamental question is why th evessels were e quipped with so many armaments at the sacrifice of the vessel stability, which is one of t hemost important issues for a vessel's safety. Although the principal cause of the accident is the demands ofthe crewmembers, the responsibility of the accident is on the shipbuilders who accepted those demands. In
the middle of the 1920s, Vice Admiral Jouzo Hiraga designed the Yuubari, Furutaka and Myoko Classes ofvessels. Ea ch vesse l had g ood sta bility characteristics. Howev er, t he sta bility of vessels in t he Japa nese
Navy got lower and lower after Vice A dmiral H iraga retired from desi gning vessels. Spec ifically, th e

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Failure Knowledge Database / 100 Selected Cases

stability of the Aoba Class was barely acceptable, and those of all vessels after the Takao Class, which wasa revision of the Myoko Class, were obviously insufficient. This shows that although Vice Admiral Hiraga
had designed some good vessels, the other persons involved in vessel design did not always agree with his
designs, and theconviction that shipbuilders should have could not compatible with the compromise.
The chief shipbuilding engineer at the time was Rear Admiral Kikuo Fujimoto, and he was famous forhis rem arkable d esigning talent. H owever, h e res igned from the post to t ake the resp onsibility for t hecapsize of Tomozuru, and he was transferred to a technological laboratory. We can just imagine how thiswell-known shipbuilding authority, who designed the Mogami and Takao Class Heavy Cruisers and Special
Class Destroyers that attracted worldwide attention felt. He trie d to rethink his design after the change ofpost, but because of his heavy anxiety he met with an untimely death. Finally Captain Keiji Fukuda (later
Vice Admiral and professor of the University of Tokyo) took over as chief shipbuilding engineer.
The Tomozuru capsize incident was the turning point for the shipbuilding technology of t he Japanese
Navy in that the importance of t he stability performance was rec ognized. One year after t he incident, theaccident concerning the shipbuilding technology occuredso called 4th Fleet Inci dent. Like those incidents,
the Japanese Navy at the time had experienced many difficulties just before the 1936's crisis.
6. Countermeasure
Tomozuru's capsize forced the Japanese Navy to fun damentally rethink the stability of their vessels. A
remodeling plan was made individually for every vessel, and shipbuilders carried out all of the remodelingplans d uring 1934~35 (Fi g. 4). The designs of a ll of the vessels under c onstruction at that t ime w ere
reconsidered from scratch.
7. Knowledge○ The t orpedo boat T omozuru ca psized d ue t o her t op-heavy stru cture. C urrent shipbuilders ha ve
valuable experience and confidence in their knowledge of sta bility. However, we must remember thedifficulties of shipbuilders in the past and make the best use of the knowledge that our pre decessors
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.

8. Background
One background issu e of Tomozuru's cas e w as a s evere d emand for in creasing t he fi ghting power of
each vess el under the restr ictions of t he disarm ament treaty. In No vember 1921 , the U.S.A, t he Bri tish
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 U.S.A, the British Empire,France, Italy and Japan agreed to restrict the total weight of each country's vessels according to the ratios 5,
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Failure Knowledge Database / 100 Selected Cases

5, 1.75, 1.75, and 3.
In ad dition to th is d isarmament trea ty, t he L ondon N aval T reaty was co ncluded in 1930. Th e treaty
established se veral res trictions c oncerning su bmarines and auxiliary ship after m any twists a nd turns. I n
this treaty, J apan appeared to h ave part ly fulfill ed her demands from the U.S.A and the Brit ish Em pire;
however, in f act the U .S.A ga ined an a dvantage o ver Japa n in co nstructing s upport vessels under t herestriction. T hus, t he J apanese na val vessels h ad t o mount large numbers of g uns at t he cost of th eir
structural s trength, w hich l ed t o t he exposure of se rious defe cts. Tomozuru's capsize and t he 4th flee t
incident fo rced us to reco gnize that i nconsistencies b etween po licy and tech nology l ead to unexpectedtragedies.
9. Sequel
From October 23rd to 26th in 1944, the Japanese Navy was soundly defeated by the U.S in the battle of
the Philippine Sea. After the battle, the U.S. 3rd fleet under the control of Admiral Halsey was assigned toattack Leyte Island. The 3rd fleet appeared east of the Philippines and attacked Luzon Airfield after two
weeks resting in Ulithi on Decem ber 13rd. Task Group 38 carried out the attack under the control of Vice
Admiral McCain.
On December 17th, Task Group 38 withdrew to the east to refuel. However, the weather worsened, andthey h ad to s uspend the re fueling operations s oon aft er the noon. O n t he m orning of D ecember 18 th, asmall 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 veloci ty e xceeded 55 m/s. The ca ptains of De stroyers Hu ll, Mon aghan and S pence needed t o 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 thestorm w as the stron gest, a nd fi nally all three vessels sank . Som e other vesse ls, inc luding fi ve li ght air
careers, three escort air careers, two heavy cruisers, and eight destroyers, were seriously damaged, and ninevessels were slightly damaged. The number of aircraft that were thrown into the sea or tha t crashed into
each other and burned amounted to no less than 183. About 800 sailors died. Task Group 38 was hea vily
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 unf ortunate. Of course, the cause of Tomozuru's capsiz is t he top secret of the Japanese
Navy at the time, and the U .S. Navy co uld no t ha ve kn own it. In con trast, almost no Japanese vessels
capsized sin ce Tomozuru did . In military field, kn owledge of fai lure cas es ca nnot b e share d betwe ennations.
10. On the SideA historical museum in Sw eden, named VASA Museum, exhibits Battleship Vasa and her history. Vasa
capsized during her first na vigation. Shipbuilders tried to m ake Vasa the largest and most beautiful vessel
ever, but such a new and adventurous vessel is n ot always successful. Vasa capsized due to her top-heavy
structure, in the same way as Tomozuru. However, Sweden has advanced diving and salvage technology, so
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Failure Knowledge Database / 100 Selected Cases

recently it succeeded in salvaging Vasa. Vasa Museum is not j ust a historical museum but also a museumthat exhibits both the pride and the shame of Sweden. It is also a museum of failure.
Vasa w as a dig sa iling sh ip w ith a d isplacement of 1 ,210 tons, a body le ngth of 47.5 m, a m aximum
width of 11.7 m, and ten sails. She was equ ipped with 64 cannons, and she carried a crew o f 145 and 300
soldiers.
Here is the chronological record of Vasa;
1625

King Gustav II Adolf decided to construct Vasa

1626

Construction began at Stockholm Naval Shipyard

1627 Laun
1628

ching of Vasa

Jan. 16th Inspected by the King
Aug. 10th Capsized in port on her maiden voyage

1664

Most of the 64 cannons were salvaged using diving bell

1953

Investigation of the sea bottom began

1957

Digging under the body of Vasa began

1961

Salvage was completed (333 years after the capsize)

1988

Last navigation from the temporary museum to the new museum

1990 Current

Vasa Museum was completed

Why did Vasa capsize? Who should take responsibility? The court tried the following four persons:○Captain at the time

Ballast, Training, Operation○Admiral at the time

Rolling Test, Suspension of Her Navigation○King Gustav II Adolf

Severe Demands, Urge to Early Construction○Designer at the time

Concealment of Chart, Patrimonial Handing Down

Capsize of vessels c aused by to p-heavy struc tures h as oc curred often si nce a ncient t imes. Be cause
people have not been able to effectively reuse those experiences and knowledge gained, the same kind of
failure has happened again and again.
11. Primary Scenario
01.Organization Problems
02. Inflexible Management Structure
03. Acceptance of Unreasonable Demands
04. Insufficient Analysis or Research
05. Insufficient Prior Research
06. Lack of Examinations and Rethinking
07. Planning and Design
08. Poor Planning
09. Poor Design
10. Torpedo Boat
11. Top-Heavy
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Failure Knowledge Database / 100 Selected Cases

12. Usage
13. Operation/Use
14. Navigation
15. Possible Damage
16. Potential Hazard
17. Winds/Waves in Rough Weather
18. Secondary Damage
19. External Damage
20. Capsize
21. Loss to Organization
22. Social Loss
23. Defense Deterioration

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Failure Knowledge Database / 100 Selected Cases

Fig.1 Torpedo Boat Tomozuru.

10Failure Knowledge Database / 100 Selected Cases

Fig.2 Vessel's Stability.
(Initial Stability is similar to a self-righting "daruma" doll)

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Fig.3

The main point of Chidori Class's Remodeling.

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Fig.4 Change of the Destroyers and Torpedo Boats' shape.
(Before and After Remodeling)13