Bismarcks armour

Discussions about the history of the ship, technical details, etc.

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paul.mercer
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Bismarcks armour

Post by paul.mercer » Sun Oct 14, 2012 10:04 pm

Gentlemen,
In the RAF museum at Duxford there is a square section of steel supposedly taken from the Tirpitz when she was broken up, from what I can remember it was over a foot thick and looked an extremely heavy and solid piece of metal. I presume the part was from the side of the ship and would be similar to what was on Bismarck, but I find it difficult to believe that a 14" or 16" shell fired from almost point blank (for a battleship) range would fail to penetrate even this mighty bit of steel as some have claimed.
I realise that when firing at another ship the point is to hit it and keep hitting rather than to target a particular spot so I wonder if the claims of very few armour penetrations was because KGV & Rodney were mainly hitting the upperworks (which appear to be almost completely destroyed) rather than the hull?

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Re: Bismarcks armour

Post by frontkampfer » Sun Oct 14, 2012 11:44 pm

IMHO-I would say its easier at close range to aim and hit another ships upper works than its sides!
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Dave Saxton
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Re: Bismarcks armour

Post by Dave Saxton » Mon Oct 15, 2012 1:56 am

paul.mercer wrote:Gentlemen,
In the RAF museum at Duxford there is a square section of steel supposedly taken from the Tirpitz when she was broken up, from what I can remember it was over a foot thick and looked an extremely heavy and solid piece of metal. I presume the part was from the side of the ship and would be similar to what was on Bismarck, but I find it difficult to believe that a 14" or 16" shell fired from almost point blank (for a battleship) range would fail to penetrate even this mighty bit of steel as some have claimed.
Nobody knowlegable has claimed such a thing. Nonetheless, what some ballistics experts, including the German experts of the time such as B Hoyer, are talking about is a system referred to as the "scarp triangle" rather than a single piece of steel. The belt was only one componant of the overall belt protection. Behind the belt were heavy scarps of 12cm thick Wh armour. The scarps were arrayed so that any shell that penetrated the belt would then strike the scarp at a very unfavorable angle. The heavy belt of face hardened armour would of course decap an armoured piercing projectile and consume most of it's energy. If the scarp was sufficiently heavy then the amount of energy required for a shell to defeat both the belt and the scarp would mean that a de-capped battleship caliber shell in most cases would be destroyed in the attempt.

The Germans considered the scarp to be of greater importance to the overall belt protection than the belt itself.

Additionally, the scarp protected the areas behind it from plug ejections, lids, and other forms of plate debris, and splinters and projectile debris.
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Re: Bismarcks armour

Post by Djoser » Mon Oct 15, 2012 7:35 am

There you have it.

I am inclined to believe the Baron's account--that the engines were still running and the ship was basically intact as far as the internal works were concerned, until he was scuttled--other that the armament and the upper works of course. No doubt he would have sunk eventually, but it took more than all they could throw at it to do the job in that short a time period. A marvelous work of design and engineering...

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Re: Bismarcks armour

Post by alecsandros » Mon Oct 15, 2012 7:58 am

Also, shells had a shatter velocity, which, beyond a certain point, would cause the shell to break up in contact with the armor plate. THis is a possible explanation for Rodney's 16" shells exploding against Bismarck's side armor.

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Re: Bismarcks armour

Post by RF » Wed Oct 24, 2012 7:53 am

Djoser wrote:
I am inclined to believe the Baron's account--that the engines were still running and the ship was basically intact as far as the internal works were concerned, until he was scuttled--other that the armament and the upper works of course. No doubt he would have sunk eventually, but it took more than all they could throw at it to do the job in that short a time period. A marvelous work of design and engineering...
But alas, still not unsinkable.

Bismarck indeed was a marvelous work of design and engineering - but was still lost as a result of one small torpedo, dropped by an obsolete biplane, striking a vital area, and no means of countering the crippling damage caused.
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Re: Bismarcks armour

Post by alecsandros » Wed Oct 24, 2012 8:54 am

RF wrote: But alas, still not unsinkable.

Bismarck indeed was a marvelous work of design and engineering - but was still lost as a result of one small torpedo, dropped by an obsolete biplane, striking a vital area, and no means of countering the crippling damage caused.
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Re: Bismarcks armour

Post by Djoser » Wed Oct 24, 2012 2:59 pm

alecsandros wrote:
RF wrote: But alas, still not unsinkable.

Bismarck indeed was a marvelous work of design and engineering - but was still lost as a result of one small torpedo, dropped by an obsolete biplane, striking a vital area, and no means of countering the crippling damage caused.
It's impossible not to think of the death of Achilles in the Trojan war...
Ha wow one of my favorite works of literature, and yes in many ways the same story...

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Re: Bismarcks armour

Post by delcyros » Wed Oct 24, 2012 4:43 pm

Nobody knowlegable has claimed such a thing. Nonetheless, what some ballistics experts, including the German experts of the time such as B Hoyer, are talking about is a system referred to as the "scarp triangle" rather than a single piece of steel. The belt was only one componant of the overall belt protection. Behind the belt were heavy scarps of 12cm thick Wh armour. The scarps were arrayed so that any shell that penetrated the belt would then strike the scarp at a very unfavorable angle. The heavy belt of face hardened armour would of course decap an armoured piercing projectile and consume most of it's energy. If the scarp was sufficiently heavy then the amount of energy required for a shell to defeat both the belt and the scarp would mean that a de-capped battleship caliber shell in most cases would be destroyed in the attempt.

The Germans considered the scarp to be of greater importance to the overall belt protection than the belt itself.

Additionally, the scarp protected the areas behind it from plug ejections, lids, and other forms of plate debris, and splinters and projectile debris.
and the same rational in my graphical interpretation:
Image

To penetrate 320mm KC/n.A. is not a trivial task. This main belt may offer a very high degree of immunity at target angles of 30 deg or more, making penetration highly unlikely unless one is able to get a clean shot on an perfectly to the projectile´s trajectory aligned belt. These conditions exist, though and most ww2 large calibre, modern APC armed guns may be capable of defeating the belt itselfe.
However, the scarp protects against these unfavourable attack conditions involving low target angle´s and low firing distances. It also deletes one good 3rd of the ships beam against plunging fire hits and the belt protects another 1/3. Finally, it adds structural strength and significantly limits the amount of floodwater passing into the ship from belt hits.

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Re: Bismarcks armour

Post by Dave Saxton » Wed Oct 24, 2012 6:21 pm

delcyros wrote:To penetrate 320mm KC/n.A. is not a trivial task. This main belt may offer a very high degree of immunity at target angles of 30 deg or more, making penetration highly unlikely unless one is able to get a clean shot on an perfectly to the projectile´s trajectory aligned belt.
Additionally, the main belt is sloped some over most of it's length because it follows the shape of the hull. For example, outboard of A turret magazines it is sloped ~17*.
Also, shells had a shatter velocity, which, beyond a certain point, would cause the shell to break up in contact with the armor plate. THis is a possible explanation for Rodney's 16" shells exploding against Bismarck's side armor.
This highlights a big advantage of the design. If the opponant is far enough away that the striking velocity of his projectile is low enough to avoid this problem, it likely isn't carrying enough velocity to defeat both the belt and scarp. If so close that his projectile has enough striking velocity to possibly defeat both, it will likely shatter against the heavy face hardened plate- as appears to be the case.
It also deletes one good 3rd of the ships beam against plunging fire hits and the belt protects another 1/3.
Moreover, it has been reported that post war the British determined that the deck protection spaced array of 50mm + 80mm provided the same deck protection as up to 150mm single plate.


In terms of vitals immunity zone the system provides a very wide zone extending from short range to approx 30km vs battleship caliber projectiles. But whats more important is that the IZ covers many battle ranges that are likely to be enccountered, rather than leaving the vitals possibly naked inside of 20km against battleship caliber projectiles.
Entering a night sea battle is an awesome business.The enveloping darkness, hiding the enemy's.. seems a living thing, malignant and oppressive.Swishing water at the bow and stern mark an inexorable advance toward an unknown destiny.

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Re: Bismarcks armour

Post by Thorsten Wahl » Thu Oct 25, 2012 11:52 am

reference document for the 6 inch assumption for Tirpitz/Bismarck
excerpt from SUPP 6/481 Proc No Q 4010 from 1.Jan 1946
Attachments
Supp 6-481 proc No. 4010 .1.Jan.1946.JPG
Supp 6-481 proc No. 4010 .1.Jan.1946.JPG (53.01 KiB) Viewed 3933 times
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