British postwar tests on armor

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paul.mercer
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Re: British postwar tests on armor

Post by paul.mercer » Wed May 01, 2019 9:43 am

Gentlemen,
Out of interest, when the tests for penetration were carried out would the bombs be filled with explosive or just a similar weigh of inert material so the actual depth of penetration could be accurately measured?

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Re: British postwar tests on armor

Post by Bill Jurens » Wed May 01, 2019 2:58 pm

Both methods were used. In USN trials, pure penetration was measured via the penetration of an inert bomb. When explosive effects were to be tested, a live bomb was inserted into a 'pre-dented' depression or hole in the target and the bomb detonated. Testers were aware that the pre-denting didn't precisely match the strain-rate effects of an actual bomb strike, but considered the difference fairly inconsequential. They were probably right in that assessment.

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Re: British postwar tests on armor

Post by Thorsten Wahl » Thu May 02, 2019 10:25 am

Herr Nilsson wrote:
According the German short report from February, 28th 1942 the armoured deck was knocked open and destroyed. There is no mention of any hatch.
Marc do you have the original Nara reference?
Would like to read.
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Re: British postwar tests on armor

Post by Herr Nilsson » Thu May 02, 2019 2:45 pm

@Thorsten

T1022-Roll2997 PG47991
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Re: British postwar tests on armor

Post by Thorsten Wahl » Fri May 03, 2019 7:30 am

Text shortend for relevant informations

Telex 27.02.1942
first Bomb hit 11:15 p.m. height Anton
loss of anton crew and leak defense group V
Fire in turret Anton and surrounding camouflage material
shortly after this flame from turret Anton possibly from cartridges with disruptive discharge to Bruno

second Bomb hit 11:40 p.m. foreship department upper deck tored off at compartment XXI and folded back strong fire in the foreship, batterydeck and Zwischendeck(steerage comment horizontal extension of the main armored deck over the scarps
Access to the center of fire impossible because of destruction, heat and gases
ammunition stores turret Bruno flooded

Casualties: about 100 dead
3000 t water within the ship

Telex 28.02
summary report

26.2 11:15 bomb hit probably 950 kg penetrated upperdeck, battery deck and Zwischendeck(steerage? comment horizontal extension of the main armored deck over the scarps) and detonated above the main armor deck- with destruction of the main armor deck at frame 185

thereby burning off of main cartridges in both forward ammo stores in compartment XVIII additional oil fire from leaking forward oil cells
(Comment of mine with a delay after the bomb detonation)

barbette turret Anton completely annealed - fire extinguishing was therofore extremly difficult
second bomb hit unlikely after further findings

damage:
-Turret A lifted by the flame slewing ring damaged when the turret falls back. Turret burned out completly inside, all platforms destroyed
-both forward main cartride rooms compartment XVIII burned out.

-bulkhead between upper powder room and cartrige loading room and
-bulkhead between lower powder room and and projectile room and
-ceiling between upper und lower powder chamber strongly destroyed

-Cartrides in aft main cartridge room and both aft powdwer rooms not burned out (comment of turret A)
...
-several oil cells in the foreship damaged by bombdetonation - completely burned out
-connection between main armor deck and torpedo defense bulkhead in the area of the powder chamber frames 180 - 185,7 cracked
-longitudinal bulkhead between turret A and B slightly deformed by heat.
-battery deck port compartment XIII - XXI damaged
-battery deck starbord compartment XVII - XXI damaged
-Zwischendeck port compartment XIV - XVIII (steerage Comment horizontal Extension of the main armored deck over the scarps) damaged
-upper deck tored off at compartment XXI folded back on the back - aft Bruno dented
-slight damge to the outer plating


ist my interpretion from the description the bomb datonation took place over the scarp of the main armor deck near the torpedodefense bulkhead causing severe cracks to surrounding bulkheads and a oil fire ; oil leaks throuhg the ruptured tanks into the main cartridge rooms causing a ongoing fire ...???
and there was a second large explosion about half hour after the bomb hit wich was interpreted in the first Telex as a second bomb hit
Last edited by Thorsten Wahl on Fri May 03, 2019 8:22 am, edited 1 time in total.
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Re: British postwar tests on armor

Post by Alberto Virtuani » Fri May 03, 2019 8:17 am

@Thorsten,
many thanks for this exhaustive explanation. Two questions are still in my mind:

1) I wonder where the "hatch left open" interpretation come from, going into Whitley's quite precise book account (timing 23:15, second explosion from fuel oil, initial interpretation of a second bomb, frame 185.6, etc.).
2) Why after the first explosion weren't the fore magazines flooded immediately, avoiding the second destructive explosion while fire was ravaging the ship ? Was it a failure from the damage control parties ?

In T1022-Roll3864 PG47997B report, dated April 6, 1942, I could find this scheme (I don't however speak German, therefore I'm unable to read any page of the (very long) report and its possible conclusions).

Gneisenau_bomb.jpg
Gneisenau_bomb.jpg (82.16 KiB) Viewed 431 times

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Last edited by Alberto Virtuani on Fri May 03, 2019 8:39 am, edited 1 time in total.
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Re: British postwar tests on armor

Post by Thorsten Wahl » Fri May 03, 2019 8:36 am

deleted
Last edited by Thorsten Wahl on Fri May 03, 2019 9:38 am, edited 1 time in total.
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Re: British postwar tests on armor

Post by Thorsten Wahl » Fri May 03, 2019 9:35 am

Edited:

A british 2000 lb AP bomb had about ~80 kg explosive content. In a contact detonation this amount seems sufficent to open a 105 mm armor plate at least 2-3 m wide.
A left open hatch is not necessary

But wat was the reason for the second? forward detonation half an hour later.
the overpressure and heat from the first detonation should be enough to cause flash immediately. If this happend ther is not further explosive content left, to cause a second detonation. Except the lower powder room was not included in the first flame/flash from turret A.
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Re: British postwar tests on armor

Post by pgollin » Fri May 03, 2019 11:37 am

Thorsten Wahl wrote:
Fri May 03, 2019 7:30 am
.

....... barbette turret Anton completely annealed ......

....... -Turret A lifted by the flame slewing ring damaged when the turret falls back. ......



.

Thanks for that, always useful to get proper info.

Re. the annealing that presumably totally ruined the armour qualities ?

Re. the "Turret A lifted" was that caused by the second (?) explosion (whatever that was) or did the fire buckle the structure thus lifting the turret and not allowing the turret to reseat properly ?

Thanks.

.

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Re: British postwar tests on armor

Post by Thorsten Wahl » Fri May 03, 2019 12:52 pm

pgollin wrote:
Fri May 03, 2019 11:37 am
...
re annealing: yes any heat threatment to FH-armor produces scrapmetal

re Turret a lifted
they did not directly say when the turret was liftet, as it was mentioned in different paragraphs.
But from wording it appears to me the lifting happened shortly after the bombexplosion at 11:15 p.m.

paragraph 1 " ...Bombe detoniert... dadurch Abbrennen Hauptkartuschen beider vorderer Hauptkartuschkammern.."
paragraph 2 "Turm A durch Abbrennen der Hauptkartuschen angelüftet..."

in the second, more detailed summary report is no further Information apparent on a second explosion only a exclusion of a bomb hit.
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Re: British postwar tests on armor

Post by Alberto Virtuani » Fri May 03, 2019 2:54 pm

Hello everybody,

thanks again to Thorsten for the kind explanations provided.

I think we should conclude now from them (and also from a photo available in T1022-Roll3864 PG47997B, showing in the caption "Detonationsort unter dem Panzerdeck", hopefully correctly translated by Google Translator as "Detonation under the Armor Deck") that the MAD was pierced, at least by splinters by the bomb that struck at 23:15 (albeit not with a "direct penetration"), even if I still wonder where the "hatch" story came from...

If this is the case, is it possible that Bismarck and Tirpitz too could be destroyed by a single "simple" 2000 lbs AP bomb ? The MAD of the Bismarck class was just 100mm above magazines (in its horizontal part, that seems to be the one where the detonation happened, looking at the scheme I have posted viewtopic.php?f=1&t=8539&p=83270#p83262), thus not really stronger than Gneisenau one (105mm), while the amount of cartridge powder was probably higher...

Was then the usage of the "Tallboy" just an "overkill" demonstration (with all the modifications needed to the Lancasters to carry such a huge bomb)?


Bye, Alberto
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Re: British postwar tests on armor

Post by dunmunro » Fri May 03, 2019 7:19 pm

Alberto Virtuani wrote:
Fri May 03, 2019 2:54 pm
Hello everybody,

thanks again to Thorsten for the kind explanations provided.

I think we should conclude now from them (and also from a photo available in T1022-Roll3864 PG47997B, showing in the caption "Detonationsort unter dem Panzerdeck", hopefully correctly translated by Google Translator as "Detonation under the Armor Deck") that the MAD was pierced, at least by splinters by the bomb that struck at 23:15 (albeit not with a "direct penetration"), even if I still wonder where the "hatch" story came from...

If this is the case, is it possible that Bismarck and Tirpitz too could be destroyed by a single "simple" 2000 lbs AP bomb ? The MAD of the Bismarck class was just 100mm above magazines (in its horizontal part, that seems to be the one where the detonation happened, looking at the scheme I have posted viewtopic.php?f=1&t=8539&p=83270#p83262), thus not really stronger than Gneisenau one (105mm), while the amount of cartridge powder was probably higher...

Was then the usage of the "Tallboy" just an "overkill" demonstration (with all the modifications needed to the Lancasters to carry such a huge bomb)?


Bye, Alberto
It seems axiomatic that if a 1600lb bomb could penetrate the MAD then a 2000lb bomb would do so more efficiently.

IIRC, they chose to use the Tallboy to capsize Tirpitz via near misses, if they didn't score direct hits.

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Re: British postwar tests on armor

Post by Alberto Virtuani » Fri May 03, 2019 8:02 pm

Hello everybody,
Dunmunro wrote: "It seems axiomatic that if a 1600lb bomb could penetrate the MAD then a 2000lb bomb would do so more efficiently"
Which type of bomb hit Gneisenau on 26/02/1942?
Thorsten mentioned the explosive charge (80 kg) of a 2000 lbs AP bomb (viewtopic.php?f=1&t=8539&p=83278#p83264)...

Dunmunro wrote: "they chose to use the Tallboy to capsize Tirpitz via near misses, if they didn't score direct hits"
Wouldn't a "salvo" of 6 2000 lbs bombs have a much higher probability of hitting Tirpitz than a single 12000 lb Tallboy ?
Tirpitz was hit by 3 Tallboys + near misses (which caused damages but did not capsize the ship).
Had Lancasters carried 6 (six) 2000 lb bombs (instead of a single 12000 lbs Tallboy) each, she could have been hit (statistically...) by 18 (eighteen) 2000 lb bombs, and the probability that one of them could find its way into a magazine would have been quite high. I still don't see any logic in using a big gun to hit a "butterfly", except if they were considering Tirpitz to be much stronger than she actually was... that is well possible after the experiences with Bismarck...


Bye, Alberto
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Re: British postwar tests on armor

Post by dunmunro » Fri May 03, 2019 9:52 pm

Alberto Virtuani wrote:
Fri May 03, 2019 8:02 pm
Hello everybody,
Dunmunro wrote: "It seems axiomatic that if a 1600lb bomb could penetrate the MAD then a 2000lb bomb would do so more efficiently"
Which type of bomb hit Gneisenau on 26/02/1942?
Thorsten mentioned the explosive charge (80 kg) of a 2000 lbs AP bomb (viewtopic.php?f=1&t=8539&p=83278#p83264)...

Dunmunro wrote: "they chose to use the Tallboy to capsize Tirpitz via near misses, if they didn't score direct hits"
Wouldn't a "salvo" of 6 2000 lbs bombs have a much higher probability of hitting Tirpitz than a single 12000 lb Tallboy ?
Tirpitz was hit by 3 Tallboys + near misses (which caused damages but did not capsize the ship).
Had Lancasters carried 6 (six) 2000 lb bombs (instead of a single 12000 lbs Tallboy) each, she could have been hit (statistically...) by 18 (eighteen) 2000 lb bombs, and the probability that one of them could find its way into a magazine would have been quite high. I still don't see any logic in using a big gun to hit a "butterfly", except if they were considering Tirpitz to be much stronger than she actually was... that is well possible after the experiences with Bismarck...


Bye, Alberto
A near miss from a Tallboy would still cause extreme damage as the Tallboy carried ~40% of it's weight as explosive versus ~8% for a 2000lb UK AP bomb. However, I agree that statistically 18 x 2000lb or 1600lb AP hits would have sunk Tirpitz.

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Re: British postwar tests on armor

Post by alecsandros » Sat May 04, 2019 4:26 am

Garzke and Dulin write about a 1000lbs (454kg) bomb impacting and incinerating Gneisenau.

I understand the estimate of 2000lbs comes from the German damage report, but the real loadout should come from RAF documents. (it's the first time I read of such bombs being used in night bombing at that period of the war , while all other bombings, including the numerous attacks against S/G in Brest were of 500 and 1000lbs variety. It's not impossible, but I think a confirmation would be nice)

Also, as Alberto inquired, from where does the "opened ventilation hatch" description come ?

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