The invasion of Oahu, December 1941.

[Carl Schwamberger]

I'm thinking the best answer to the question of fragmentation size & potiential damage would be to look at the damage reports & see if there is anything indicating what the Japnese bombs did in this regard.

[OpanaPointer]

I'm thinking the best answer to the question of fragmentation size & potiential damage would be to look at the damage reports & see if there is anything indicating what the Japnese bombs did in this regard.

The War Damage Reports would be the go-to for that. http://ibiblio.org/hyperwar/USN/rep/WDR/index.html

[glenn239]

I'm thinking the best answer to the question of fragmentation size & potiential damage would be to look at the damage reports & see if there is anything indicating what the Japnese bombs did in this regard.

The War Damage Reports would be the go-to for that. http://ibiblio.org/hyperwar/USN/rep/WDR/index.html

That's an interesting report - is the one for the LST's going to be posted?

USSBS, Vol10, Chp 2, pg 27 provides probable value of MAE ( Mean area of effect, 1,000 square feet of damaged building per ton of bomb)

500lbs GP 13.3
1000lbs GP 13.0
2000lbs GP 13.9

[OpanaPointer]

That list is all I'm aware of insofar as WDRs are concerned.

The "damage" includes punctured walls and roofs, IIRC. Zimm cites an effort on the coast of the Red Sea where the Italians deliberately and methodically sabotaged a repair facility. The USN crew got it going again in 30 days, using only the materials on hand. And they improved the output over the best the Italians had done. An air raid would produce much less damage.

[BDV]

Did the japanese have any airplane cannons in 1941?

That, rather than bombs seems the tool for the petroleum-tank busting job.

[Carl Schwamberger]

Yes many of the Japanese naval aircraft of 1941 were equipped with a pair of 20mm cannon. While they were 'underpowered' compared to European & US models they were better than medium aircraft MG in terms of damage per X seconds of firing. A quick web search should turn up more than one source with penetration data for the Japanese 20mm aircraft cannon ammo.

Ok. Here is a Red Army report, translated, of the ignition of Diesel & gasoline type fuels in tanks. While this is not the same as ships bunker type fuels it should give some general idea of what it takes to ignite petroleum fuels in containers and spilled or uncontained fuels. Another point is the ratio by weight or volume of explosive to fuels is vastly different between a cannon projectile/132 liter vehicle fuel tank and a 500lb bomb & a large depot type storage tank. A extended discussion of this report is here: http://www.armchairgeneral.com/forums/s ... ost2699481 ...which includes authentication of the report from current Russian sources.

Bottom line is ignition of fuel more likely occurs where there is a large volume of vapor inside the fuel tank. Ditto for detonation of the fuel. In tests on full fuel tanks ammunition detonations would burst the tank but ignited the diesel fuel in only four of 18 test shots, 22%. Detonations of the fuel occured in three of 18 test shots. 17%. What is easy to miss in the report is the lack of evidence that fragments entering the fuel tanks caused either ignition or detonation.

All this leads me to question how volitile the bunker fuel was at the temperatures from around early November to 7 Dec, and if there was a safety venting system for the fuel tanks to disapate vapor from the fuel.

"Source #632/2
September 11, 1944

Report of the NKV Special Laboratory #101-1 on the topic of STUDY OF CHARACTERISTICS OF STRIKING A T-34 GAS TANK WITH AP-HE OR CUMULATIVE (HEAT) SHELLS OF THE GERMAN FASCIST ARMY

Responsible: Rozov, Kaminskiy, Shurov
Supervisor: Sarafanov

History of the topic

In the spring and summer battles of 1943, tank commanders began to note instances of T-34s destroyed by fire or detonation of fuel tanks. For example, during the summer of 1943, at Kursk, fires happened more often than on the T-70 by 4-9%. By the order of the Head of the BTU GBTU of the Red Army, Engineer-Colonel Afonin, a special commission was formed on September 11th, 1943. Our team was tasked with exploring the possibility of detonating the T-34's gas tank using several armour-piercing measures, and the evaluation of the impact on the crew and internal equipment.

Objective

Examination of 72 tanks at SPAM bases, destroyed during the battle at Kursk, the commission found that most of them (68%) were destroyed by un-sealing of the fuel tanks and subsequent ignition of the diesel fuel. All these tanks were struck in the side or overtrack hull by an AP, HEAT, or HE shell. Approximately a third of the examined tanks lack one or two gas tanks, and have damage to the welding seams due to the internal explosion. Only a small portion of the tanks have traces of internal explosion and fire (8%), while 24% of the vehicles were destroyed by explosions only, with no traces of fires. The ammunition remained undamaged in the racks. Acting on our orders, we examined specifically the cause of destruction by an exploding fuel tank.
...
Engineer-Colonel Gurov and Dr. Krutov, after examination of the tanks, suggested that the damage is caused by detonation of the front fuel tanks, after being hit with some kind of special German shell. Engineer-Major Firsov theorized that this could have happened after detonation of a high temperature shell inside the gas tank, like one based on thermite. Comrade Sarafanov's team was ordered personally by the chief of the GBTU to investigate the possibility of detonation of the T-34's gas tanks as a result of being hit with various types of shells used by the fascist armies.

Equipment used in the experiments

To evaluate the theories of comrades Gurov, Firsov, and Krutov, NII-48 and Uralmash built three T-34 full scale models from 35 mm thick armoured steel with a 135 liter (see blueprint #2) fuel tank. Also, as a result of letter #312-a sent on April 21st, 1944, the BTU supplied us with a T-34 hull, with equipment inside, but without armament.

Experiments

The first test of the models happened on December 12th, 1943, from a 75 mm model 1940 tank gun, from 30 meters. During these tests, the fuel tank was fully filled with diesel fuel, according to comrade Afonin's letter from December 5th.

8 model 38 shells were fired, as well as 5 model 39/40 shells, and 5 HEAT shells. The results are as follows: the fuel tank was destroyed completely 3 times. The fuel ignited 4 times. No explosions were observed. When struck with a model 39/40 shell, the fragments were rapidly stopped. A full T-34 gas tank cannot be a source of an explosion, and also offers protection from armour fragments and cores of model 39/40 shells.

Comrade Krutov suggested that gasoline would also be unable to explode when the tank is full. Comrade Fedin ordered a gas tank be installed. 3 model 38 shells and one HEAT shell were fired. No explosions. The gasoline ignited 2 times.

The second stage started on February 9th, 1944. The same gun was used, along with an 88 mm recoilless model 1943 gun, shooting 88 mm HEAT charges. The tests were done on tanks that were partially filled. Before this, the full tanks were driven around on a truck for 1-2 hours on a dirt road, and then fuel was partially drained from it.
...
Fourth series of shots. The tank was filled 10-25%. The tank explodes when hit by a HEAT shell at under 25% capacity. The explosion was equivalent to 30-50 grams of TNT. The gas tank cover was knocked off. In the case of a gasoline tank, the explosion is 1.5 times weaker. The gas tank cover opens as a result of the explosion. Welding seams remain intact.
...
The effect of a detonation of a 75 mm AP shell with the red ring, equipped with 80 g of TNT and a 20 g detonator, is quite different. The explosive force grows several times over. The overtrack hull seams burst, and the roof of the model is deformed. The model becomes useless.

Conclusions

The best conditions for a detonation is a tank that is 10-15% full, and a detonation of the "rot" shell with 80 grams of TNT and 20 grams of phlegmatized explosive. The fumes detonate, resulting in a force equivalent to a 105-122 mm AP shell.
An even better effect is achieved by the detonation of the domestic 76.2 mm BR-530A shell, with 150 g of TNT, which is equivalent to a 152 mm shell with 400 g of TNT. With a reduced caliber, the likelihood of an explosion decreases drastically. 45 mm and 37 mm guns are nearly incapable of causing a detonation. An increase in caliber does not result in an increase of explosive effect. The optimal caliber is 75-85 mm and 50-100 grams of TNT, or a smaller amount of more powerful explosive substances (30-80 grams of A-1X-2 or 25-50 grams of phlegmatized cyclonite). The tank must be at least 100 liters in size. Tanks 30-50 liters in size do not result in significant increase of the shell's explosive force.

Countermeasures
Do not place fuel tanks inside the fighting compartment.
Use fuel from rear tanks first, as they are less likely to be hit.
Build fuel tanks that collect less vapours. As fuel is spent, replace it with an inflammable fluid or a gas that does not ignite. Before battle, flush gas tanks with CO2, CO, or constantly ventilate front fuel tanks.
Half the size of fuel tanks in the fighting compartment.
Place the fuel tanks behind airtight armoured plates.
Rozov
Kaminskiy
Shurov

Sarafanov"

[OpanaPointer]

The 20's were fused super-quick to kill aluminum aircraft. Not much good against steel of any thickness.

Oh, and the tanks had floating tops that reduced the amount of space available for volatiles to accumulate. It's almost as if they knew vapors burned.

[Carl Schwamberger]

... It's almost as if they knew vapors burned.

Seriously. I wonder if the floating top was heavy enough to dampen the hydrostatic pressure wave in the fuel enough to burst the sides of the tank. Or would the top pop off and some of the oil geyser upwards?

[OpanaPointer]

... It's almost as if they knew vapors burned.

Seriously. I wonder if the floating top was heavy enough to dampen the hydrostatic pressure wave in the fuel enough to burst the sides of the tank. Or would the top pop off and some of the oil geyser upwards?

They were on tracks to avoid torquing. So either the shock would jam them against the rails or they'd slide up with the shock wave. (Jamming would seem most likely as the force wouldn't be even around the periphery.)

[Carl Schwamberger]

The question still stands. Even if the guides jam the covers may not be heavy or strong enough to withstand the upward pressure of the oil and pop apart. A bomb might have to detonate very close to the tank walls to put enough pressure on them to fail.

Elsewhere I'm told bunker fuel was created by removing as much of the volatile fractions as practical. The idea being to not have a lot of vapors. Also told this is a difference between refined bunker grade fuels and unrefined light crude oils. The latter exude a lot of light fraction vapors, which include the highly volatile fractions. Those occur in proportions, quantities, and at temperatures that are not entirely predictable.

Unfortunatly the promised link for this info is not yet forthcoming.

[OpanaPointer]

Carl, petroleum fractioning is the process of cooking crude and separating the various chemicals so they can be siphoned off. This is the purpose of refining. It's not to remove volatiles from the fuel oil, it's the acquire those volatiles in a more pure state. The bunk oil is one of the left overs, a few steps removed from tar, and the refineries were happy that the navies wanted it.

[phylo_roadking]

Just as an aside...

Bottom line is ignition of fuel more likely occurs where there is a large volume of vapor inside the fuel tank. Ditto for detonation of the fuel

...which was of course the reason why aircraft dropped (and still do) their external drop tanks BEFORE going into combat - so they don't start exchanging hot lead or cannon rounds while sitting on top of basically a couple of unarmoured fuel-air bombs!

Also why some aircraft fitted with internal wing tanks in the first days of high performance monoplane fighters etc. had CO2 systems onbard - to purge the tanks of vapour as they emptied of liquid fuel.

[Carl Schwamberger]

Carl, petroleum fractioning is the process of cooking crude and separating t... .... happy that the navies wanted it.

More to the point information on the quantity of vapor produced by stored bunker fuel made in the US in 1945 has not yet turned up. Somewhere there must be data for safety engineering. Maybe information on how well the tanks were vented is available somewhere. Other information that might be useful would be Japanese reports on damage to their storage tanks at Truk or the Indonesian refineries. Both were attacked by the USN & USAAF. Maybe this last has been posted here earlier? I've not yet checked.

[OpanaPointer]

Carl, petroleum fractioning is the process of cooking crude and separating t... .... happy that the navies wanted it.

More to the point information on the quantity of vapor produced by stored bunker fuel made in the US in 1945 has not yet turned up. Somewhere there must be data for safety engineering. Maybe information on how well the tanks were vented is available somewhere.

You can be sure that the engineers who designed those tanks weren't morons and any dangerous vapors were properly vented. Each tank also had a fire suppression system.

Other information that might be useful would be Japanese reports on damage to their storage tanks at Truk or the Indonesian refineries. Both were attacked by the USN & USAAF. Maybe this last has been posted here earlier? I've not yet checked.

USSBS would have that data. The Allied forces would have been using bombs appropriate for the task, 1,000 or 2,000 pound bombs.

[Carl Schwamberger]

Problem with assumptions is they dont really settle anything. This debate on damaging the PH fuel tanks has gone round and round for years on multiple forums/threads with many participants and very few have attempted to do more than swap guesses or post a few photographs.

Unfortunatly I'm stalled on the subject of vapor off bunker fuel. Found that my informant on the subject died some time ago. John Mortenson a retired marine propulsion engineer with a career on cargo ships and previously a USN patrol boat crewman in Viet Nam passed after his second severe cardiac failure. I'd first met him three years ago as part of a group of veterans who helped restore his house to habital condition. So RiP John M.

So, what are the details of fire suppresion system?