British postwar tests on armor

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alecsandros
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Re: British postwar tests on armor

Post by alecsandros » Sat Apr 27, 2019 9:49 am

Duncan,
the 2inch on Tirpitz was made of whotan steel, which was armor grade material. The 1,5inch on Rodney was made of consruction steel, which was not armor grade.

There was some importance of construction steel against incoming attacks , but not as much as full armor grade material would provide (the coefficient being between 0;5 to 0;9 depeding on quality parameters).

Also, if discussing steel decks (in general) , both Rodeny and Tirpitz had more steel decks in between the upper and lower decks, both of them totalling near 200mm (some areas of Tirpitz near 220mm IIRC).

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Re: British postwar tests on armor

Post by dunmunro » Sat Apr 27, 2019 10:43 am

alecsandros wrote:
Sat Apr 27, 2019 9:49 am
Duncan,
the 2inch on Tirpitz was made of whotan steel, which was armor grade material. The 1,5inch on Rodney was made of consruction steel, which was not armor grade.

There was some importance of construction steel against incoming attacks , but not as much as full armor grade material would provide (the coefficient being between 0;5 to 0;9 depeding on quality parameters).

Also, if discussing steel decks (in general) , both Rodeny and Tirpitz had more steel decks in between the upper and lower decks, both of them totalling near 200mm (some areas of Tirpitz near 220mm IIRC).


The Nelson class weather deck was 60lb (1.5in) D steel, which was an improved HT steel and it had very good armour qualities. However, what you don't seem to understand is that having a thick weather deck imposes severe topweight penalties and as a result the MAD must be thinner, additionally the scarf extension is very costly in terms of top weight. Consequently Nelson could have a 1.5in DS weather deck, a .5in MS battery deck, and a 6.25in MAD (over .5in D steel) over the shell rooms and an additional 1.5in splinter deck directly above the magazines which were under the shell rooms. BWOC, Bismarck had a 50mm weather deck, a ~6-20mm battery deck and a 100mm MAD, with the magazines directly under the MAD, and the Bismarck class deck armour arrangement was unquestionably worse in terms of providing protection from AP bombs. The KM reports on the 1600lb bombs made it clear that the bombs that failed to penetrate the MAD, only failed because they were released too low (the KM estimated a release height of 300 and 1300ft), but even then they sent splinters through the MAD. OTOH, the Nelson class armoured deck arrangement was essentially invulnerable to a 1600lb bomb unless dropped at very high altitude (~7000ft).

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Re: British postwar tests on armor

Post by HMSVF » Sat Apr 27, 2019 11:33 am

dunmunro wrote:
Sat Apr 27, 2019 10:43 am
alecsandros wrote:
Sat Apr 27, 2019 9:49 am
Duncan,
the 2inch on Tirpitz was made of whotan steel, which was armor grade material. The 1,5inch on Rodney was made of consruction steel, which was not armor grade.

There was some importance of construction steel against incoming attacks , but not as much as full armor grade material would provide (the coefficient being between 0;5 to 0;9 depeding on quality parameters).

Also, if discussing steel decks (in general) , both Rodeny and Tirpitz had more steel decks in between the upper and lower decks, both of them totalling near 200mm (some areas of Tirpitz near 220mm IIRC).


The Nelson class weather deck was 60lb (1.5in) D steel, which was an improved HT steel and it had very good armour qualities. However, what you don't seem to understand is that having a thick weather deck imposes severe topweight penalties and as a result the MAD must be thinner, additionally the scarf extension is very costly in terms of top weight. Consequently Nelson could have a 1.5in DS weather deck, a .5in MS battery deck, and a 6.25in MAD (over .5in D steel) over the shell rooms and an additional 1.5in splinter deck directly above the magazines which were under the shell rooms. BWOC, Bismarck had a 50mm weather deck, a ~6-20mm battery deck and a 100mm MAD, with the magazines directly under the MAD, and the Bismarck class deck armour arrangement was unquestionably worse in terms of providing protection from AP bombs. The KM reports on the 1600lb bombs made it clear that the bombs that failed to penetrate the MAD, only failed because they were released too low (the KM estimated a release height of 300 and 1300ft), but even then they sent splinters through the MAD. OTOH, the Nelson class armoured deck arrangement was essentially invulnerable to a 1600lb bomb unless dropped at very high altitude (~7000ft).
I don't know if you have a copy of Burts "British Battleships 1919 - 1945" but if you havent it goes into some detail in regards to post war tests performed on...

HMS Nelson (in Operation Bronte).

The results were that although 2000lb bomb could penetrate her 6 inch deck it would have to be dropped above 5000 feet to achieve this (3000 to 4000 feet ended up with 3inches to almost 5 inches of penetration). 39 bombs were dropped from 8000 feet and no hits were achieved, so they dropped the altitude 6500feet (they only had 60 bombs allocated to the trial)

Eventually they did hit her 3 times and 3 times they pierced the deck.

The conclusions were that the bombs had to be dropped from 5000 feet or above, that Nelson was a well built ship and it hadn't been easy and she had been stationary, but the deck had been penetrated.


Sad end for a great ship.Not bad for a 1920's design though.


Best wishes HMSVF

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Re: British postwar tests on armor

Post by alecsandros » Sat Apr 27, 2019 4:22 pm

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Last edited by alecsandros on Sat Apr 27, 2019 4:24 pm, edited 1 time in total.

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Re: British postwar tests on armor

Post by alecsandros » Sat Apr 27, 2019 4:22 pm

dunmunro wrote:
Sat Apr 27, 2019 10:43 am
dunmuro wrote:
Sat Apr 27, 2019 9:49 am

The Nelson class weather deck was 60lb (1.5in) D steel [...]
1,5 inch D steel is not 1,5 inch of armor grade mat.

All bombs dropped over Tirpitz and Scharnhorst were either exploding on the MAD or were rendered dud (some bombs dropped on Scharnhorst perforated all the way to the bottom of the harbor).

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Re: British postwar tests on armor

Post by HMSVF » Sat Apr 27, 2019 5:31 pm

Duplicate post !

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Re: British postwar tests on armor

Post by dunmunro » Sat Apr 27, 2019 7:11 pm

The AP bomb that destroyed Gneisenau seemed to work quite well.

Two of the bombs that struck Scharnhorst detonated against the MAD after having penetrated the weather deck including:
The other 227 kg (500 lb) bomb fell forward of the after turret, to starboard, 3 meters from the deck edge; it penetrated two decks and exploded on the main armor deck, where it made a small hole. Several frames were holed by splinters, and the connection at the top of the torpedo bulkhead was damaged. The penetrated decks bulged from the explosion and were holed by splinters. Some flooding occurred in the outboard spaces. Heating, potable, and plumbing piping under the battery and middle decks was damaged. The ammunition hoists for the 37 mm guns were put out of action, although the ammunition was not affected.
http://www.scharnhorst-class.dk/scharnh ... brest.html
If the above hit had struck above a magazine it could have destroyed the ship.

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Re: British postwar tests on armor

Post by alecsandros » Sun Apr 28, 2019 10:28 am

Gneisneau was crippled by a high explosive, not armor piercing bomb.
Details of her crippling are given in Garzke/Dulin Axis Battleships.

It wasn't a failure of the armored system , but of on board discipline.

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Re: British postwar tests on armor

Post by HMSVF » Sun Apr 28, 2019 11:58 am

alecsandros wrote:
Sun Apr 28, 2019 10:28 am
Gneisneau was crippled by a high explosive, not armor piercing bomb.
Details of her crippling are given in Garzke/Dulin Axis Battleships.

It wasn't a failure of the armored system , but of on board discipline.

I was under the impression that she hadn't had her ammunition taken off whilst docked - and wasn't "closed up" at the time of the raid? If she had have been she wouldn't have burned out the forward section?


Best wishes HMSVF

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Re: British postwar tests on armor

Post by alecsandros » Sun Apr 28, 2019 1:20 pm

It's been awhile since last reading G and D, but from memory a ventilation shaft was left opened in the night of the raid, and fragments from a HE bomb which exploded in contact with the upper deck were sucked inside the shaft and transported into the main forward powder magazine, where they cause the explosion of the stored powder.

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Re: British postwar tests on armor

Post by paul.mercer » Sun Apr 28, 2019 4:41 pm

spicmart wrote:
Fri Apr 26, 2019 9:37 pm
dunmunro wrote:
Thu Apr 25, 2019 10:58 pm
BWOC, post war trials on Rodney showed that a 2000lb AP bomb had to be dropped above 5000ft to penetrate her Main Armoured Deck, which was much thicker (6in versus 4in) than Tirpitz's MAD and Rodney's magazines were two decks below the MAD and had a 1.5in splinter deck directly above them.
You don't count the 2 inch upper deck of Tirpitz in?
Gentlemen,
Just an aside, but does this mean that the two 'Nelsons' were actually pretty tough old birds

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Re: British postwar tests on armor

Post by dunmunro » Sun Apr 28, 2019 7:17 pm

G&D state that Gneisenau was hit by a 1000lb GP (SAP) bomb that burst on the upper deck, but Koop states:
She suffered only a single hit. The bomb struck the forecastle, and, having penetrated the upper and battery decks, detonated against the armour deck. The hot explosive gases were sucked through the ventilators into the magazine below ‘A’ turret and ignited the powder in the shell cases for the ready ammunition. There followed a chain reaction: the powder went up in a great jet of flame and the excess pressure lifted up ‘A’ turret and tossed it askew. All members of the turret crew were killed. The ship’s final death toll was 112. A catastrophic explosion was only averted by immediately flooding the shell rooms and magazines. On 23 April Grossadmiral Raeder visited the ship.

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Re: British postwar tests on armor

Post by alecsandros » Sun Apr 28, 2019 7:42 pm

"through the ventilation" ? Just like that ?

I remember there was a board of enquiry held after the explosion of the ship, that ultimately determined the cause to have been an ventilation shaft which was left OPENED .

What does Koop say about that ?

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Re: British postwar tests on armor

Post by HMSVF » Sun Apr 28, 2019 8:08 pm

paul.mercer wrote:
Sun Apr 28, 2019 4:41 pm
spicmart wrote:
Fri Apr 26, 2019 9:37 pm
dunmunro wrote:
Thu Apr 25, 2019 10:58 pm
BWOC, post war trials on Rodney showed that a 2000lb AP bomb had to be dropped above 5000ft to penetrate her Main Armoured Deck, which was much thicker (6in versus 4in) than Tirpitz's MAD and Rodney's magazines were two decks below the MAD and had a 1.5in splinter deck directly above them.
You don't count the 2 inch upper deck of Tirpitz in?
Gentlemen,
Just an aside, but does this mean that the two 'Nelsons' were actually pretty tough old birds
Yes, very tough, although their armoured belts were reckoned to be on the shallow side. This was identified and a planned modification was prepared but never fitted due to the onset of war. My understanding was that they employed the basics of the aborted G3 and N3 designs. They were certainly a quantum leap on previous British battleships. What they lacked (and the G3's had) was speed.


Best wishes


HMSVF

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Re: British postwar tests on armor

Post by dunmunro » Sun Apr 28, 2019 8:28 pm

alecsandros wrote:
Sun Apr 28, 2019 7:42 pm
"through the ventilation" ? Just like that ?

I remember there was a board of enquiry held after the explosion of the ship, that ultimately determined the cause to have been an ventilation shaft which was left OPENED .

What does Koop say about that ?
Koop says nothing about that.

I'm sure I've read more detailed accounts, but I can't locate any at the moment.

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