Fuel rate of Asashio class destroyer
IJN task force ( kido butai ) accomanied 9 destroyers in Pearl Habor operaion, which left Hitokkapu Bay on 23 November 1941. 7 of 9 destroyers were Kagero class. And the rest were Asashio class. Range of Kagero class was 5,000 nm at 18 kt, otherwise Asashio class was 5,700 nm at 10 kt, 960 nm at 34kt. The displacement of Asashio class was less than 120t compared with Kagero class. As fuel capcity of Asashio class was 500 t, I guess fuel capacity of Kagero class was 620 t. So, Kagero class spent fuel of rate 8.1 nm/t at 18kt.
|2nd Range [nm]||
|3rd Range [nm]||
|2nd Fuel [nm/t]||11||9.2||8.0||5.6||4.1||3.5||1.9|
|3rd Fuel [nm/t]||11.4||8.7||7||4.3||3.1||2.6||1.9|
Drag force is proportional to speed by Newton's law. The drag force is proportional to square of speed considering area effect of the body. I computed fuel comsumption rate of Asashio by 2nd order (square) interpolating function. Considering the work of engine, drag force D is,
D = kv²
Power is proportional to cubic of speed. Pitch of propellar is not variable. Power is dependent on revolution of
propellar. Fuel consumption may be proportional to the revolution of engine. Capacity of fuel is constant. So range is
inverse proportional to cubic of speed. Interporation curve of range is a function of
Dds = kv²ds ( ds is infinitive length )
dW = Dds
dW/dt = kv²ds/dt ( dt is infinitive time )
P = kv³ (dW/dt = P, ds/dt = v)
Range = k/(v³-h)
The result is as follows. Asashio class may run 4,000 nm at 18kt judging from the fuel capacity. This is shorter than
1,000 nm than Kagero. How much fuel did the destoryers spend? After refuel off 600 nm Hawaii, The KB ran. The KB
stayed till 13:00 to receive aircraft. Sunrise and sunset are 6:56 and 17:49 in Honolulu on 7 December. The KB ordered to launch aircraft at 6:00.
24 kt for 5 hours 120 nm 21 tIt looks very little. The KB might run zigzag. The destroyers always have to adjust output of engine to keep
formation of the KB. In fact, some destoryers refueld 200 t in 30 hours depearture from Hitokkapu Bay.
The KB ran at 14 kt. The destroyers was to spend at the rate of 2.1 nm/t at 14 kt. 7 Oilers
fueld destoryers on 28, 29, 30 November, 1, 2, 5, 6 and 7 December. I do not know how each destroyer refueld. The
destroyers was short of fuel, if the incredable rate was true.
28 kt for 5 hours 140 nm 34 t ( Kaga's max speed )
? 110 nm 14 t ( in case of 18 kt )
26 kt for 5 hours 130 nm
20 kt for 6 hours 120 nm
Light cruiser Abukuma refueld on 30 November, 1, 2, 5, 6 and 7 December. Why did Abukuma refuel with capacity of 1,260 t
seven times in spite of 5,000 nm range at 14 kt? IJN range data of warships were planned values. The displacement of
Abukuma increased 1,500 t comparing with the original 5,500 t. The range might decrease 27 % at least.
After all, speed of the KB was limited by aircraft carrier Kaga, and freedom of the operation was limited by the fuel
capacity of Kagero class destroyers.
IJN destroyers ratio per carrier
Only 9 destroyers had escorted 6 aircraft carriers in Pearl Harbor Operation. Two destroyeres Kasumi and Arare were
seperated from KB to escort oilers. The both were Asashio class destroyers.
|Ref. Genda p.274|
Though 2 battle cruisers, 2 heavy cruisers and 1 light cruiser also escorted, they had no depth charges for ASW. IJN
thought that USN submarines were not threat because of unknown operation, didn't it? The table shows ratio of
destroyers per carrier. Some historians criticizes that the KB should do the third air strike. Could only 7 destroyers
shield 6 aircraft carriers effective?
USN destroyers ratio per carrier
|Ref. Yomitan history, ASW|
CNO King of USN ordered submarines to sink destroyers than merchant ships at first on Apr 1944. IJN lost 11 destroyers, 4 destroyer escorts and 3 other escorts because of enemy submarines from April to Jun 15th.
IJN selected Tawi-tawi as anchorage port of 1st Kido Fleet. Saipan is nearer to Japan than Taui. The reasons were,
But Tawi-tawi was enroute that USN submarines ran from Freemantle to the South China Sea. And worse Tawi-tawi and Japan was the same distance from Kwajalein.
- Gunreibu guessed USN would invade Palau at first
- Shortage of oilers was to anchor near oil export
1st Kido Fleet came to Tawi-tawi on May 13th. It was necessary for pilots of carriers to train landing everyday etc. Carriers could not run to train pilots out of the port freely, becasue submarines were hiding. So 1st fleet ordered destroyers to sweep submarines. 4 destroyer were sunk one by one for 4 days. These were Minazuki, Hayanami, Kazakumo and Tanikaze. Ooi p.238-241
Sonars of the destroyers were worse than US submarines. I do not know how each destroyer repeated failure of anti submarine combat. The below is image of the Tawi-tawi Bay
The table shows 3 types of discharges which IJN developed in 1937 to 1943.
Specifications of IJN depth charges
|Type||Year||Decending speed||Set of Depth [m]||Explosive||Weight||Length||Diameter|
|Type 95||1937||1.9m/s||30, 60||100kg||160kg||775mm||450mm|
|Type 2||1942||2.0m/s||30, 60, 90, 120, 150||100kg||162kg||775mm||450mm|
|Type 3||1943||5.0m/s||40, 80, 120, 160, 200||100kg||180kg||1400mm||450mm|
The production of depth charges was as follows. Strangely production of 1943 decreased. Was production of Type 3 depth charge in 1944 actually?
Production of IJN Depth charges
Sekai no kansen, No.507
Gunzo, p5-11, No74