AOSHIMA
1/700-scale WATER LINE SERIES WW2 JAPANESE NAVY DESTROYER IJN HATSUHARU
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Additional Information from
Internet Encyclopedia
The Hatsuharu-class destroyers (Hatsuharugata
kuchikukan) were a class of Imperial Japanese Navy destroyers in the service
before and during World War II. The final two vessels in the class, completed
after modifications to the design, are sometimes considered a separate
"Ariake class".
Background
The provisions of 1930 London
Naval Treaty stipulated that the overall destroyer tonnage for the Imperial
Japanese Navy would be capped at 105,500 tons with a maximum permissible
tonnage per ship of 1,850 tons. Furthermore, only 16 percent of the overall
tonnage could be of this size, with the remainder not exceeding 1,500 tons per
vessel. This effectively meant that additional units of the previous Fubuki and
Akatsuki-class destroyers could no longer be built. The Imperial Japanese Navy
responded by ordering naval architects to design ships that were lighter by at
least 260 tons, and yet mount the same armament. In the end, the new class
ended up with one less gun (three turrets with five 127 mm guns instead of
six), with a smaller hull and displacement. This armament design was not
unprecedented, however, as the two Romanian Navy destroyers Mărăști and
Mărășești were fitted with two twin and one single 120 mm guns a few years
prior, in 1926.
This stretched contemporary
destroyer designs beyond the limits, and resulted in a top-heavy design, with
severe stability problems. The weight-control measures used by designers were
carried to an extreme, which further contributed to structural weakness. This
was a problem shared with other Japanese ship designs of the time, which
attempted to place too much armament on too small a displacement hull. This was
graphically demonstrated when the torpedo boat Tomozuru capsized in 1934 during
heavy seas (the "Tomozuru Incident") and when a typhoon ripped the
bows off two Fubuki-class destroyers (the Fourth Fleet Incident) in 1935. As a
result of these two incidents the Hatsuharu-class vessels had to be rebuilt
(the first two completed had to be rebuilt twice) or modified while building to
remedy their stability problems.
Design
The Hatsuharu-class destroyers
were designed to accompany the Japanese main striking force and to conduct both
day and night torpedo attacks against the United States Navy as it advanced
across the Pacific Ocean, according to Japan's naval strategic projections.
They were to be armed much as the Fubuki class despite displacing only 1400
tons compared to the 1700 tons of the earlier destroyers. Furthermore, their
fire control systems were to be more modern than the older systems and suitable
for anti-aircraft use. This required the gun turrets to be modified for
high-angle fire, which also meant more powerful motors to traverse and elevate
the guns more quickly to engage high-speed aircraft. The torpedo launchers were
to be given a protective shield to allow for use in heavy weather and to
protect against splinter damage. And the Hatsuharu vessels were to be fitted
with modern, enclosed command spaces protected against strafing aircraft. These
requirements could only be met by adding weight high up on the ship and
increased the ship's center of gravity. The only way to adhere to the allotted
displacement was to try to reduce the weight of the hull and other equipment
below the waterline as much as possible. But this put the ship's designers in a
no-win situation as any reduction of weight below the waterline further raised
the ship's center of gravity and reduced her stability.
The weight of the hull could
generally be reduced by using higher grades of steel that were lighter and
thinner for the same strength, reducing dimensions, particularly length, or
using advanced construction techniques like welding that saved weight over the
conventional riveting. The Japanese used the same high-tensile steel for the
Hatsuharu class as they did for the older destroyers and chose not to increase
the power of the turbines and boilers to achieve the desired high speed, but
lengthened the hull to offset the reduced power of the light-weight machinery.
The beam was increased to counter some of the extra top-weight, but the draft
was reduced to reduce hull resistance, which also reduced stability by
lessening the area of the hull beneath the waterline in comparison to the area
above it, which was subject to pressure from the wind.
Extensive weight-saving measures
were used during the design and construction of the hull. More frames of
lighter construction were spaced more closely together to reduce the thickness
of the hull plating and the extensive use of welding (only the longitudinal
stringers and a few other parts were riveted) were some of the techniques
utilized to reduce hull weight by 66.5 tonnes (65.4 long tons; 73.3 short tons)
in comparison to the Fubuki class. Electric welding was extensively used to
reduce weight although it was at an early stage of development in Japan and was
still problematic.[6] The Hatsuharu vessels were some 10 metres (32 ft 10 in)
shorter than the Fubuki-class vessels, but weighed 4.9 tonnes (4.8 long tons;
5.4 short tons) per 1 metre (3.3 ft) of hull length compared to the latter's
5.09 tonnes (5.01 long tons; 5.61 short tons) per 1 metre (3.3 ft).
Description
The Hatsuharu-class ships were
shorter than their predecessors, at 109.5 m (359 ft 3 in) overall. The ships
had a beam of 10 metres and at full load a draft of 3.35 m (11 ft 0 in).
Despite the emphasis on weight-saving during construction, the ships were
significantly overweight as completed and displaced 1,530 metric tons (1,510
long tons) at standard load, and 1,981 metric tons (1,950 long tons) at full
load, nearly 130 metric tons (100 long tons) more than planned.
The hull of the Hatsuharu-class
vessels retained the general configuration of the Fubuki-class destroyers with
a long forecastle and a pronounced flare of the forecastle to improve
sea-keeping at high speeds by adding buoyancy and reducing the spray and water
coming over the deck. A large bridge structure was located at the aft end of
the forecastle deck topped by four fire control stations of various types.
Lowest, just above the compass bridge, was the torpedo director (Hassha
shikisho), with the gunnery fire direction station (Shageki shikisho) next
above. The fire director tower (Hōiban shagekito) was third from the bottom and
behind it was the 3 m (9 ft 10 in) rangefinder. Each of these was protected by
10 mm (0.39 in) plates of Dücol steel against strafing and shell splinters.
For the first time in a Japanese
destroyer, a superfiring turret was fitted forward of the bridge. It was only a
single gun Model A turret, to save weight high in the ship, and was mounted on
a deckhouse to elevate it above the twin gun Model B Mod 2 (B-gata kai-2)
turret mounted on the forecastle deck. The second twin gun turret was mounted
at the rear of the ship on the main deck. These turrets were slightly heavier
than the earlier Model A and Model B turrets fitted on the Fubuki-class. All
turrets were fitted with the 12.7 cm (5.0 in) Type 3 gun.
The uptakes of the two forward
boiler rooms were trunked together aft of the break in the forecastle into the
fore funnel while the rear boiler room exhausted into the smaller rear funnel.
Both funnels were inclined to the rear to reduce the amount of smoke that might
reach the bridge. A tripod mast was fitted between the bridge and the fore
funnel. Between the two funnels was the forward 61 centimetres (24 in) triple
torpedo tube mount fitted on a low platform. Behind it "was a torpedo
locker with its mechanical quick reload system (Kiryoku sōtenshiki jihatsu
sōten sochi) for the three reserve torpedoes inside."[9] To preserve
lateral stability the aft funnel was offset to starboard while the torpedo
mount was offset to port. The reload locker was also offset slightly to port
and angled inboard to facilitate reloading. The middle torpedo mount was
positioned behind the aft funnel on the centerline, but its reload locker was
positioned identically to that of the forward mount. Superimposed to starboard
and overlapping the middle mount was the rear triple torpedo mount positioned
on the rear deckhouse. Immediately behind the mount was its locker positioned
on the centerline, but angled slightly to the right so that its mount only had
to traverse slightly to align with the locker and begin reloading. This was the
first ship in history to be fitted with superimposed torpedo tubes, made
necessary by the designer's insistence on fitting nine torpedo tubes despite
the Navy's requirement for only six.
A small platform that carried a
2 m (6 ft 7 in) rangefinder was mounted above the rear torpedo locker and a 90
cm (2 ft 11 in) searchlight was mounted on a tower behind the rear funnel. The
two license-built Vickers 40 mm (1.6 in) (pom pom) anti-aircraft guns were
mounted on an elevated platform at the front of the rear funnel. Curiously they
were another case where the designer exceeded the requirements laid down by the
Navy.
Propulsion
The Hatsuharus carried two sets
of Kampon geared steam turbines, one for each shaft. Each set consisted one
low-pressure and one high-pressure turbine, plus a cruise turbine connected to
the high-pressure turbine. The LP and HP turbines were connected to the
propeller shaft by a two-pinion reduction gear. Each propeller had a diameter
of 3.05 m (10 ft 0 in) and a pitch of 3.7 m (12 ft 2 in). The total horsepower
of the Hatsuharu class was only 42,000 shp (31,000 kW) compared to the 50,000
shp (37,000 kW) of their Fubuki-class predecessors, but the machinery was
significantly lighter and more powerful on a unit basis. The Hatsuharus'
machinery weighed only 106 tonnes (104 long tons; 117 short tons) compared to
the 144 tonnes (142 long tons; 159 short tons) of the Fubuki class, or 396
shaft horsepower per tonne versus 347 shaft horsepower per tonne for the older
ships.
Similarly the three Kampon Type
Ro-Gō boilers used in the Hatsuharu-class ships weighed 50 tonnes (49 long
tons; 55 short tons) in comparison to the 51 tonnes (50 long tons; 56 short
tons) boilers used in the Fubuki class, but produced 14,000 shp (10,000 kW)
each while the older boilers produced 12,500 hp (9,300 kW). This gave a ratio
of 3.6 kg per shaft horsepower for the Hatsuharu's compared to the 4.1 kg per
shaft horsepower of their predecessors. The newer design of boilers initially
used steam pressurized to 20-bar (290 psi), just like the older models, but
used superheating to improve efficiency while the older boilers simply used
saturated steam.
A single 100 kW turbo-generator
was fitted behind the reduction gears in a separate compartment and two 40 kW
diesel generators were located between the propeller shafts. As initially
completed the Hatsuharu had a range of 4,000 nautical miles (7,400 km; 4,600
mi) at a speed of 18 knots (33 km/h; 21 mph) with 460 tonnes (450 long tons;
510 short tons) of fuel. On trials, Nenohi had a top speed of 37.64 knots
(69.71 km/h; 43.32 mph) from 47,150 shp (35,160 kW) at a displacement of 1,677
tonnes (1,651 long tons; 1,849 short tons).
Armament
The Hatsuharu-class destroyers
used the same 50 caliber 12.7 cm gun as the Fubuki class, but all turrets could
elevate to 75° to give the main guns a minimal ability to engage aircraft.
During the war the single turret was removed on all surviving ships after 1942.
The only anti-aircraft guns were two water-cooled, license-built Vickers
40-millimeter guns. These guns were deemed to be too heavy, slow-firing and
short-ranged and were replaced by license-built French Hotchkiss 25 mm (0.98
in) Type 96 anti-aircraft guns in single, double and triple mounts from 1943
for the surviving ships. Exact numbers are not always known, but Hatsuharu was
carrying three triple power-driven mounts, including one mounted in lieu of the
single 12.7 cm gun turret, one twin power-driven mount fitted on a platform in
front of the bridge and two hand-worked single mounts in June 1944. These
powered mounts were unsatisfactory because their traverse and elevation speeds
were too slow to engage high-speed aircraft[14] and more single mounts were
fitted to ships in the last year of the war. For example, Hatsushimo mounted
ten single 25 guns when she was lost in July 1945. Four license-built Hotchkiss
13.2 mm (0.52 in) Type 93 machine guns were also fitted to Hatsushimo, but
these were of limited utility against modern aircraft.
The 61 cm Type 90 torpedo was
mounted in triple tube Type 90 Model 2 launchers, derived from the twin tube
Type 89 launcher used in the Takao-class heavy cruisers. Shields were fitted to
both the torpedo mounts and lockers to protect them from the weather and from
strafing aircraft. Initially, the shields were made from Duralumin to save
weight, but these quickly corroded and had to be replaced. "NiCrMo"
steel, taken from the air chambers of obsolete torpedoes, 3 mm (0.12 in) in
thickness, was chosen for the new shields to save weight. The Type 90 Model 2
weighed, including the shield, a total of 14.4 tonnes (14.2 long tons; 15.9
short tons) excluding the torpedo itself. Despite the addition of an extra
torpedo tube, it was still lighter than the 14.5 tonnes (14.3 long tons; 16.0
short tons) of the Type 89. It was traversed by an electro-hydraulic system and
could traverse 360° in twenty-five seconds. If the backup manual system was
used the time required increased to two minutes. Each tube could be reloaded in
twenty-three seconds using the endless wire and winch provided.
Only eighteen depth charges were
initially carried in a rack at the stern, but this increased to thirty-six
after the autumn of 1942. Apparently, no sonar or hydrophones were fitted until
after the outbreak of the war when the Type 93 sonar and Type 93 hydrophones
were mounted. Both of these were inferior to contemporary American and British
designs.
Radar
Radar was not installed on the
surviving ships of this class until late in the war, possibly as late as 1944.
They were given a Type 22 radar on the foremast, a Type 13 on the mainmast and
a Type E-27 radar countermeasures device was carried high on the foremast.
Construction
A dozen Hatsuharu-class
destroyers were authorized in 1931 as part of the so-called Circle One Program
(Maru Ichi Keikaku). Three were laid down in Fiscal Year 1931 and the next
three in Fiscal Year 1933. The remaining six ships were built as the Shiratsuyu
class.
Design modifications
On trials Hatsuharu was found to
roll heavily, with a very short period of roll and she heeled at an angle of
38° at high speed when her helm was set to 10°. This demonstrated to the Navy
that her metacentric height was too low. The Navy ordered in September 1933
that 30-centimetre (12 in) bulges be fitted on each side to increase her beam
and thus raise the metacentric height. Hatsuharu and Nenohi were modified after
completion; Wakaba and Hatsushimo were modified during construction. Ariake and
Yugure were at a much earlier stage of construction and had their beam
increased by 1 metre (3.3 ft). The bulges were estimated to add 30 tonnes (30
long tons; 33 short tons) to the trial displacement.
The capsizing of the torpedo
boat Tomozuru in 1934 forced the Navy to re-evaluate the heavy armament of the
Hatsuharu and other classes. As a result of the investigations in ship
stability after the capsizing of the torpedo boat Tomozuru, all vessels in the
Hatsuharu class were modified to improve their stability:
The after deckhouse and
rangefinder were removed and the forward single 12.7 cm gun mounting was
relocated to this position, directly ahead of the after twin gun mount; its
magazine was converted for use as a fuel tank.
The No.3 triple torpedo mount
and its reload locker were removed.
The compass bridge was lowered
by one level and the anti-strafing armor was removed from the entire bridge
structure.
Both funnels were shortened by
11.5 metres (3 ft 3 in 4 ft 11 in) as were both masts.
The forward torpedo tube mount
was lowered 30 centimetres (12 in), the machine-gun platform by 1.5 metres (4
ft 11 in) and the searchlight platform by 2 metres (6 ft 7 in).
The bulges were removed and the
anchor chain stowage was lowered by one deck.
The outer bottom plating was
reinforced and about 70 tonnes (69 long tons; 77 short tons) of ballast was
added in the ship's bottom.
An automatic system was fitted
which filled part of the fuel tanks with seawater to compensate for the
consumption of fuel and resulting rise in the center of gravity and hence loss
of stability. When the sea water was added to the fuel tank due to their
different specific gravities the seawater sank to the bottom of the tank, while
the oil floated on top.[17]
The first two ships of the class
Hatsuharu and Nenohi had already entered service by the time of the
Tomozuru Incident. They were removed from service and modified in the Kure
Naval Arsenal. The remaining four members of the class were still under construction
and were modified before completion.
Based on the stability issues
shown by Hatsuharu during her trials, Ariake and Yūgure had been modified for
two balanced rudders placed directly behind the propellers and angled outward
18.5° to reduce the angle of heel when turning. These proved to reduce their
speed by one knot and were removed after their trials as superfluous since both
ships had been rebuilt to reflect the lessons of the Tomozuru Incident.[22] The
two ships also had a beamier hull and a shallower draft to accommodate the
rudders, and this allowed them to operate in areas of shallow water.
Reinforcement of the hull
As a result of hull damage
sustained by two Fubuki-class destroyers during a typhoon on 26 September 1935,
the subsequent investigation led to all ships in the Hatsuharu class spending 3
months in the shipyards having their hulls strengthened, at the cost of an
extra 54 tonnes (53 long tons; 60 short tons) of weight, and their fixed
ballast increased from 64 to 84 tonnes (63 to 83 long tons; 71 to 93 short
tons). As a result of these and previous modifications the ships were 23.2%
heavier, had lost 33% of their torpedo armament and were 3 knots (5.6 km/h)
slower compared with their original design values.
Wartime service
All Hatsuharu-class ships were
lost during the Pacific War. Four were sunk by aircraft attack, and Nenohi was
sunk by the American submarine USS Triton. Hatsushimo, the last Japanese
destroyer lost in the war, struck a mine on 30 July 1945. All ships in the
class took part in the Invasion of the Aleutians.