Armor is used to protect vital systems from hits.
It is represented as the thickness of armor plating in a specific region of a ship (in inches or millimeters). There are other factors such as the materials used, quality of armor as well as slope. Armor at a sloped angle deflects incoming shells better, making it much more effective without having to actually thicken it.
The hull of a ship has two armor values: belt (vertical) and deck (horizontal) which represent the protection against a hit to the side or a hit from above.
Regions of the superstucture and gun turrets of a ship have a single armor value.
The following factors determine whether a shell will penetrate armor:
Caliber – Larger shells can punch through thicker armor.
Muzzle Velocity – Higher velocity shells possess more energy to penetrate armor.
AP Shell – Armor-piercing shells have a smaller explosive warhead, but penetrate armor about 5x better than a HE shell of similar caliber.
Striking Angle – Shell strikes at shallow angles may simply bounce away (ricochet).
Short Range – shell has a higher velocity with shallow trajectory. It can punch through belt armor but ricochet off of deck armor.
Long Range – shell arcs downward with steep trajectory. It can ricochet off belt armor but penetrate deck armor (called plunging fire).
DAMAGE DEALT BY SHELLS
When an AP shell strikes armor the following may occur:
– Shell caliber is greater than 14x the thickness of armor struck, it automatically penetrates and explodes doing full damage.
– Shell strikes, penetrates the armor, and explodes doing full damage.
– Shell strikes at a shallow angle and is deflected (ricochet) doing 20% damage.
– Shell fails to penetrate armor and explodes externally, causing only 20% damage.
High explosive (HE) shells do an additional 25% damage.
HE shells can still penetrate armor but are as only as effective as an AP shell about 1/5th of their caliber.
Any hit to an unarmored part of a ship (or if shell caliber is greater than 14x armor thickness struck), will automatically penetrate and explode doing full damage.