Armored Citadel?

[destroyer67]

So, I just have a quick question. I'm slightly confused about what the armored citadel actually is. I've looked around, but I can't seem to get a straight answer. From what I can understand, the armored citadel is a place or several places around the ship that are incredibly well armored that store ammunition, fuel, the engines, and the crew that aren't fighting. Is there anything more to it than that, or did I hit it right on the nail?

[TheSenmori]

You got it right mostly. Typically just boilers and magazines (ammo storage) that is better armored than everything else. Direct penetrating hits to the citadel will blow them up.

[CadaverHvyMtl]

Basically.

 

Watch the videos on the Battleships WoWs has.  It kind of explains it better. 

 

The Citadels are the core areas of the ship, with the most armor.  These areas typically housed the "brain center" of the warship - the modern term is CnC for Command and Control.  This is where they would have the plotters for aiming the guns, the U.S. ships particularly, would have their radar and precursors to computers.   Yes, ammo, fuel, and engine areas could also be part of the Citadel.

[Elouda]

For most all or nothing designs, you can basically describe it as the volume enclosed by the armoured deck on top, the main belt to the sides, and the fore/afk belt bulkheads on the ends. Generally it starts anywhere from 0.5-2m above the waterline (though there are exceptions) and extends from a few to many meters below. It also includes volume enclosed by the turret barbettes where these extend above the main armour deck, and I've seen turrets both included and not (depending on if the definition is 'region of most importance' or 'region required for intact core bouyancy').

 

Generally this volume will include the engine and boiler rooms, some or all of the engine shafts, ammunition and powder magazines, main battery plotting and fire control room, primary damage control room, etc. This can vary a fair bit by design.

 

For a practical example, the blue shaded area on this diagram (the side-on one) of the Iowa's protective scheme shows the citadel areas;

[mariandavid]

When you look at various battleships one can spot the various devices that designers used to reduce the size of the citadel - which in turn meant less armour weight and then less tonnage. The best examples are the RN Nelson and both the French Strasbourg and Jean Bart classes all of which massed their turrets in one area so reducing the length of the citadel protecting the magazines - these and the gunnery control rooms got the best protection both in terms of armour and 'depth' which is a measure of how far it is from the belt and/or deck to the critical point. 

[Sad_But_Drew]

The other thing a "raft" citadel like the Iowa's will do is enclose enough buoyancy to keep the ship afloat and stable.  The "ends" being unarmored but divided into many small compartments.  The idea is to make sure the BB can keep moving floating and fighting as long as possible.