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howardxu_23

Armor scheme effectiveness

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Was thinking about this in releation to real life intended role and effectiveness vs effectiveness in wows after I visited the Belfast. I noted that the bow area of the ship(stern area is generally locked out) have things that could potentially provide enough resistance for a shell to arm if it hits it, and also potentially slow it enough to cause it to detonate inside, so that made me think about armor schemes.

i have came up with 2 main types looking though the armor models here and the internet, one is all or nothing, another is incremental.

 

all or nothing:

examplesnagato, US BBs in general

all or nothing is based on the idea that if you blow up the boiler in a boiler-turbine-shaft system, the entire thing is going to stop working anyways. The same thing goes to ammo+propellant , it is extremely difficult to arrange them without having the resulting explosion when they get hit damaging something else.

In the ideal form of the system, all of a battleship's armor was concentrated to form an armored "citadel" around the ship's vitals: an armored box of uniform thickness designed to defend against the largest enemy guns. Anything else that is not crucial to a ship’s combat/movement capability is left unarmored.

pros:

  • gives the best thickness around the citadel and vital areas.
  • Ideally, the ship can lose its bow and stern completely and still float.
  • The idea behind an unarmored bow, stern and superstructure is that shells can pass through them without having the fuse in them arm, then the shell could pass through the entire ship without exploding.

Cons:

  • a shell flying through the ship is still causing damage along the path of the said shell.
  • there can be something in the way that could arm the said shell, a cooking pot, the admiral’s bed, or some scrap metal piled up somewhere.
  • compartmentalising the said bow and stern for better resistance to flooding may end up giving enough stuff to slow and arm the said shell.
  • crew moral may drop if they know that they have to work in the unarmored section of the ship while it’s in combat, refer to 1st point, there can be every chance that you end up in the way of the shell.

incremental armor:

examples: KM BBs, Fuso, WW1 RN BBs

A older system of armouring the ship that dates to when the first steel clad ships came out. It is basically covering the entire ship with armor plates, each with enough thickness to stop gun calibers that were used at that time. The design of those ships at that time had a thick middle belt where the ammo and engines are behind, and medium thickness everywhere else to stop small - medium sized guns, and the deck having just enough to stop splinters. It was later phased out as gun calibers became larger and engagement ranges increased, where only the thickest armor is effective and plunging fire became more of a problem, and treaties limiting the tonnage of warships+physical constraints itself(solid steel blocks are not gonna float)

pros:

  • makes the ship immune to small-medium calibers of weapons.
  • Good for close range engagements of the time.

cons:

  • Less raw thickness of armor plates.
  • as gun effectiveness increased, it soon became clear that only the thickest possible armor is gonna work, or have nothing at all and hope that the shell does not arm.
  • Increased engagement ranges means that the lack of deck armor can become fatal.

 

effectiveness of each scheme in wows:

HE+IFHE spam is strong vs All or nothing schemes due to how damage works, and to a certain extent you can lolpen the lightly armored sections of the ship to get large damage. The best example of the problem is nagato, she has a 310mm belt, but her weather deck, bow and stern is only 25mm thick and contains HP, which means she is  weak to HE spam, and to herself oddly enough, due to how overmatch works(410mm can lolpen 25mm armor). However having a thick belt means that shots aimed at it needs to pass through more of it, a good example being GK vs Yamato. GK has 380mm belt, which makes it the thinnest at t10, Yamato has 410mm belt on the other hand, then thickest(assuming all steel quality is the same). When a shell impacts at 45 degrees, the shell has to pass though about 580mm of armor for the Yamato, increasing the chance of a shell shatter, on the other hand on the GK the shell needs to pass through 537 of armor, which makes it more likely that the shell will penetrate, and the effect increases with angle.

 

on the other hand, incremental armor scheme can be more effective in certain situations, such has the fuso(only had experience with her so far) she has a 100mm plate which covers her upper belt and more armor plates covering her bow and stern area, which makes it so that there is no way that a small-medium caliber HE shell can pen it, and also means that it is always above the threashold limit for autobounce to work. A good example is Yamato and GK again. Yamato can overmatch up to 32mm worth of armor, but GK has 60mm(?) plates covering a large portion of her bow, which effectively makes it nearly immune to yamato’s guns when bow in. However having a thinner overall armor plate over the vital areas means that if you got caught showing full broadside in a turn or got jumped on, you get deleted faster or in the case of Germans, take massive penetration damage.

 

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On 9/10/2018 at 9:12 PM, howardxu_23 said:

The idea behind an unarmored bow, stern and superstructure is that shells can pass through them without having the fuse in them arm, then the shell could pass through the entire ship without exploding.

Depends on reliablity of the fuze.

 

During the Jutland Battle the Germans achieved 30 hits on unarmored/thin armored parts. 29 shells exploded after the expected delay.

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On 9/10/2018 at 9:12 PM, howardxu_23 said:

incremental armor:

Better to say layered armor.

The "german armour scheme" consists of several layers.

 

To reach vital parts of the ship i.e. magazines/machinery/energy, it was required to defeat always several layers of armour with different functions.

 

Side protection

1) main armour belt 320 mm

2) sloped part of the main armour deck 110/120 mm

3) torpedo bulkhead 45 mm

 

The side protection requires, depending on angle of fall of the attacking projectile, 550 mm - 750 mm armor grade material in series to be penetrated AND with he the projectile required to remain whole, to allow for full order detonation within the vital area of the ship.


In "Unterlagen und Richtlinien zur Bestimmung der Hauptkampfentfernung..." they used a additional textual explanation using the wording with regard to side protection:
" Es muss deswegen angestrebt werden, soweit irgendwie möglich, auch den Horizontalpanzer in das Gesamtsystem des Seitenschutzes einzugliedern. Hierdurch kann erreicht werden, dass wenigstens auf den Hauptgefechtsentfernungen die Zerstörungswirkung von den lebenswichtigen Teilen des Schiffes ferngehalten wird. "
translation
"It must therefore be seek for, as far as possible, to integrate the horizontal armor into the overall system of side protection. In this way it can be achieved that at least at the main combat distances [/ b] [/ u] the destructive effect is kept away from the vital parts of the ship."

As main combat distances they give 12-18 km against various battleships, these distances correspond with distances at wich own guns may defeat enemies side protection completely.

 

Horizontal protection

the horizontal protection consists of 

1) upper deck50 mm

2) battery deck ~ 20 mm high tensile steel and splinter bulkhead 30 mm - 75 mm armour grade steel

3)main armoured deck 80 mm/ 100 mm

according to primary documentation of the Kriegsmarine on immunity zones the 50 mm + 80mm protection offers protection against penetration of own gun up to 30 km distance.

 

In the context of the evaluation of the horizontal protection "Battleship H", fears were expressed, that the horizontal protection consisting of a 50 mm upper deck and 100 mm armored deck could already penetrated at angles of fall of 15 ° - 25 ° (corresponding to a distance of at least around 20 km).

The Navy Weapons Office(Marinewaffenamt) therefore carried out fullsize ballistic tests with 40.6 cm armor piercing shells, which were able to dispel the fears.

It is confirmed that there is a risk to the horizontal protection with regard to penetration through the armored deck (penetration whole) requires a angle of fall of about 27 ° corresponding to a distance of 30 km.

Hauptgefährdung Panzerdeck Schlachschiff H.jpg
Hauptgefährdung Panzerdeck Schlachschiff H.jpg (85.21 KiB) Viewed 114 times

(Bundesarchiv BA-MA RM 20/1913 Akte Oberkommando Kriegsmarine AV Allgemeine Typfragen für Schlachtschiffe, Panzerschiffe und Kreuzer (02/1939- 12/1939) Schreiben Marinewaffenamt M WA Ia 759/39 g-Kdos. vom 6. April 1939)

 

With regard to the splitted horizontal arrangement.

Not every splitted arrangement of deck protection may reach the same or better results of ballistic protection as a single plate of same total thickness.

British ballistic research gave requirements for the positive case
1) detachment of armor piercing cap (ADM 281-37 The ballistic performance of Non-Cemented, Cemented and Face Hardened Deck Armour (200+240 lbssqft) under attack by decapped APC)
at 60 degrees angle of incidence, the speed required for perforation of single armor plate for usual decapped armor piercing projectiles was increased by about 15 - 20 % percent compared to the same capped armor piercing projectile

2) sufficent distance between first deck and armor deck to develop sufficent yaw., (DEFE 15-490 High Obliquity Attack of Deck Targets. Part III, it was a series of three reports describing high angle attack of deck targets.)

Yaw is a double edged sword. It may assist or prevent perforation, depending on development of yaw.
-The yaw increases steadily after perforating the first plate.
-Decapped projectiles develop yaw faster.

With so called "Optimum Yaw" a shell may perforate a plate of given thickness far below its expected ballistic limit ( 20-40%).
The "Optimum Yaw" region lies for Armour piercing projectiles in the region of about 15 degrees projectile tilt towards armor plate compared to the line of flight.
But if yaw was sufficent, the projectiles usually failed to perforate by topple. It makes a somersault on impact of the main armour plate.
Image

The german armour scheme is probably the only one possessing a first deck with sufficent thickness for potentially decapping incoming projectiles and it was also the only one wich includes a distance of two decks until the main armour deck.

Further explanation see also SUPP 6-910 THE PENETRATION OF ARMOUR PLATE Summarized report of all british ballistic research up to 1951
Chapter four "Complex Targets.

British post WW2 research uprated Tirpitz horizontal protection to an equivalent of 6" single plate against british projectiles compared to earlier assessments.
In SUPP 6-481 Underwater performance of shells they described the target
"a target similar to the Tirpitz with dimensions as follow
-Beam 125 feet deck armour 6 inches
-vertical side armour 12 inches extending to 8 feet above waterline
-vertical underwater target equivalent to 2 inches extending from 8 feet below WL to 22 feet below WL.
.....
Chance of an effective hit .. against deck armour
...range 30000 yard; Nil..."

This report was written after the first "High obliquity attack of deck targets report" from July 1945

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