Armour scheme - AoN vs. Sloped deck

[aeson]

There are two types of flooding in the game - normal or controllable flooding, which can be reduced and stopped by damage control, and progressive or uncontrollable flooding, which cannot be reduced or stopped by damage control; the two are summed to get the flooding number you see in the ship window during battle. It is my belief that a part of the advantage AoN has over non-AoN armor schemes is that progressive flooding is less likely to occur, and if it occurs then is likely of a lesser magnitude, with AoN than without it.

[imryn]

When considering "Reserve buoyancy" it doesn't matter where it is. It can be centred at the waterline, above the water line, or below the waterline. All it means is that if a ship built with a citadel is flooded outside the citadel it will remain afloat until the weight of water that enters the ship, plus the mass of the ship, exceeds that value. From this it can be seen that where the water enters the ship is irrelevant. It doesn't matter if it is forward, aft, or above the citadel; it is the mass of the water plus the mass of the ship that matters.

If you want to talk about stability, that is a whole different question; and yes, then where the flooding is matters very much. Flooding above the citadel would be much more dangerous in terms of stability than flooding forward or aft.

You avoid getting flooding above the citadel by putting the roof of the box above the waterline, but this means the side of the box is now vulnerable to being hit. If you expect to receive mostly plunging fire that hits the deck not the sides then this is fine. If you expect to receive direct fire that hits the sides not the deck its not so good.

How the game models this is beyond me. I don't recall ever seeing anything to indicate that a ship has capsized before sinking so I assume the concepts of buoyancy and stability have been lumped together into a single model in the game engine.

[dorn]

rimbecano, aeson
Thanks, I think you are right as I remember that in RTW1 I built early powerful battlecruiser and to have 3x2x15" guns and heavily armour main belt and deck, I completely sacrifice belt and armour on extended parts of the ship. As ship has sloped deck I was quite surprised how many floatation points were lost compared to number of hits. 

imryn
You can have reserve buoyancy above waterline however it matters where it is as it need to be below waterline till ship is sunk to be used. This is main disadvantage of sloped deck as if shells penetrate belt and not deck, ship can be still flooded, especially if it is deeper in water. This means that even if citadel is not compromise it has not enough reserve buoyancy to remain afloat.

[imryn]

Feb 13, 2020 12:22:09 GMT -6 dorn said:

rimbecano , aeson
Thanks, I think you are right as I remember that in RTW1 I built early powerful battlecruiser and to have 3x2x15" guns and heavily armour main belt and deck, I completely sacrifice belt and armour on extended parts of the ship. As ship has sloped deck I was quite surprised how many floatation points were lost compared to number of hits. 

imryn
You can have reserve buoyancy above waterline however it matters where it is as it need to be below waterline till ship is sunk to be used. This is main disadvantage of sloped deck as if shells penetrate belt and not deck, ship can be still flooded, especially if it is deeper in water. This means that even if citadel is not compromise it has not enough reserve buoyancy to remain afloat.

In regular ships reserve buoyancy is the volume of the hull above the waterline. The waterline on a ship is calculated by comparing the mass of the ship to the mass of the water the ship displaces. As the mass of the ship increases (e.g. loading cargo) the ship settles lower in the water and the reserve buoyancy is reduced. In the event of flooding the ship will continue to float until the mass of the water inside the hull, plus the mass of the ship (including cargo etc) equals the mass of water the hull displaces. At that point the waterline is at the top of the hull and the ship sinks.


Warships can be designed with an armoured citadel and this citadel is designed to contain enough volume to keep the ship afloat even if the rest of the hull is flooded. It doesn’t matter what shape the citadel is, or where it is in the hull, if the hull is full of water but the citadel is intact the waterline will never reach the top of the hull and the ship will float.


Often, when you look at documents about a ship you see a phrase like “has sufficient reserve buoyancy” when describing the citadel. This is quite vague. If the ship is completely flooded (apart from the citadel) is 1 inch remaining free-board sufficient? Or 1 foot? Or 2 feet? More?


Different design choices dictate the shape of the citadel and it’s positioning in the hull, but “has sufficient reserve buoyancy” is always a requirement and is a function of the volume of space it encloses. It is technically possible to build a ship with a citadel that does not encompass enough reserve buoyancy, but I don’t know of one that was built that way. It’s a bit of a “no brainer” and they probably shoot naval architects that forget it.


The choice of armour scheme also has an impact on the shape of the citadel. “Flat deck on belt” armour schemes tend to put the roof of the citadel on top of the hull. This creates a very tall citadel and leaves the sides vulnerable to being hit by direct fire. It is very easy to incorporate enough reserve buoyancy into the citadel with this design. The areas of the hull outside the citadel are forward and aft of it.


“Sloped deck” armour schemes tend to put the roof of the citadel below the top of the hull and angle the sides down to meet the belt armour near the waterline. This creates a short citadel and gives the sides very good protection against direct fire. Because the citadel is shorter it is more difficult to incorporate enough reserve buoyancy into this type of citadel. The areas of the hull outside the citadel are forward, aft, and above it.


In reality armour schemes were much more varied, but for RTW purposes we have these two.


If we only consider buoyancy there is nothing to differentiate between them – if the citadel isn’t flooded, they both float, if it is flooded they both sink, but buoyancy isn’t the whole story. As a ship floods stability becomes the critical issue. If a ship can be flooded above the citadel the water can slosh from side to side and induce the ship to capsize.

I don’t believe stability is specifically modelled in this way in the game engine – at least I have never seen anything about a ship capsizing before sinking.


We have been down this road before, discussing sloped deck vs AON, and I absolutely don't want to go there again. That said, I still don't like the way the game models them. The sloped deck armour scheme is available from 1899 in the game and doesn't appear to change at all right through to the end. This is just plain wrong. Early sloped deck ships had no armoured citadel and that meant that hull penetrations anywhere could potentially flood the whole ship. Later sloped deck ships did have an armoured citadel and that meant that hull penetrations outside that citadel could not cause flooding within the citadel. I believe that the reason ships with sloped deck armour are subject to greater flooding in the game is down to the way the armour schemes are implemented - the sloped deck scheme does not get the benefits of an armoured citadel.


The game offers only a very limited number of choices of armour scheme, and that is a very poor representation of the changes that took place in the time period. I would like there to be a lot more granularity in the design process instead of limiting us to a handful of “historical” armour schemes.

[euchrejack]

I agree that the armor system is a gross simplification, as trying to make historical ships is nearly impossible, as just trying to find out from their specs how much armor to set generally is an exercise in guesswork.

However, there are more than two options regarding the issues of buoyancy and armor, and thus it isn't as simple as mentioned.
Options are:
Armor scheme: Protected, Sloped, AoN
Magazine Box
Belt/Deck/Extended Belt/Extended Deck
Inclined Belt
Narrow Belt

Less obviously, any weight left over is converted into extra buoyancy.
Ship type also has a factor in armor layout and seaworthiness, maybe even buoyancy.
An unknown factor is the effect of Low Seaboard on the process.
Even overall speed may be a factor.

[aeson]

Feb 14, 2020 10:13:10 GMT -6 euchrejack said:

Less obviously, any weight left over is converted into extra buoyancy.

This is incorrect. Being over the design displacement comes with a flotation point penalty, but there is no bonus for having free tonnage left over.

[euchrejack]

Feb 14, 2020 10:37:56 GMT -6 aeson said:

Feb 14, 2020 10:13:10 GMT -6 euchrejack said:

Less obviously, any weight left over is converted into extra buoyancy.

This is incorrect. Being over the design displacement comes with a flotation point penalty, but there is no bonus for having free tonnage left over.

Sorry, my mistake, I'll remove it from the above.

[Deleted]

I always wanted to know how much deck or belt armor is added by having the turtleback armor, but I always got just an answer that there is *some* bonus.

[dorn]

We do not know.
At maximum range I would expect around half of thickness and there can be some additional damage if belt is penetrated but not sloped deck.

But may be there is some simplicity even more.

[rimbecano]

Feb 22, 2020 16:34:36 GMT -6 @pavelsvt said:

I always wanted to know how much deck or belt armor is added by having the turtleback armor, but I always got just an answer that there is *some* bonus.

I don't know how it's implemented in game, but from general principles I'd expect that belt hits result in a normal belt penetration calculation, and if the belt is penetrated, then a deck penetration calculation is done with a reduced striking velocity and steeper impact angle (because the outer part of the deck is sloped). I would also expect that there are more parts of the ship that can be damaged without deck penetration (since the deck is mounted lower).

[imryn]

The key concept that predated the idea of AoN armour was the armoured raft - the introduction (re-introduction I should say) of the concept of having an armoured citadel that contains all the important stuff and sufficient reserve buoyancy to keep the ship afloat if everything outside the citadel is flooded. AoN armour was simply a methodology used to armour that citadel. AoN does not even require the use of flat deck - It simply states that armour should be concentrated on the important areas at the expense of having none elsewhere. Flat deck offers weight savings over sloped deck as has been shown here, but either method could be used to armour an All or Nothing ship.

It is truly unfortunate that they chose to put a button for AON armour in the ship designer, because that locks out all other armour schemes except flat deck, and that is just patently false. Replace the AON tech unlock with an Armoured Raft tech unlock (the actual tech that offered the improved protection against flooding) and the AON button with an Armoured Raft button and let us armour it how we see fit. That would actually reflect the real world far better than the situation we have now. In the real world flat deck ships had extensive armour outside the belt and deck - no ship was ever armoured to pure AON principals.

[Adseria]

I don't know anything about the relative protection or weight or anything like that. What I do know is that, in video games, if something needs researching/unlocking, it's probably better than what you already had. As a result, once I unlock AON, I use it for all my ships. No idea if that's a good idea, but that's what I do.

[JagdFlanker]

Mar 20, 2020 7:41:52 GMT -6 Adseria said:

I don't know anything about the relative protection or weight or anything like that. What I do know is that, in video games, if something needs researching/unlocking, it's probably better than what you already had. As a result, once I unlock AON, I use it for all my ships. No idea if that's a good idea, but that's what I do.

AON may or may not be better for ship vs ship battles, but if the extra saved weight goes into deck armour it definitely helps against aircraft bomb hits

[metalslug]

From my layman's understanding of how it /should/ work, Sloped deck makes the Deck armor into a hexagonal shape behind the belt giving EXTRA citadel protection from shots with flat trajectories, causing some close range shots the penned the belt to either detonate outside the citadel or shatter. This makes plunging fire on the other hand a lot more dangerous because any shells that hit the "slope" portion of the citadel will be hitting at the best angle for penetration.

Flat deck and belt is just that, flat deck armor and flat belt. Less effective at close ranges but no detriment at long.

AoN is the same as Flat, except there is no armor spared on "non essential" parts of the ship, making structural damage a lot easier to achieve. Ships with this scheme are a lot easier to mission kill, but might still be able to limp away at 5 knots with all turrets destroyed and mangled substructure.

So if you have a Battleship meant to slug it out at <10000 yards, sloped is the way to go. If you want to engage from long range, AoN will do you more favors.

[dorn]

Mar 28, 2020 17:50:33 GMT -6 metalslug said:

From my layman's understanding of how it /should/ work, Sloped deck makes the Deck armor into a hexagonal shape behind the belt giving EXTRA citadel protection from shots with flat trajectories, causing some close range shots the penned the belt to either detonate outside the citadel or shatter. This makes plunging fire on the other hand a lot more dangerous because any shells that hit the "slope" portion of the citadel will be hitting at the best angle for penetration.

In case of sloped deck, it is lower in ship so hitting only sloped deck should not happen.