Shipbucket

Basically the title.


Among other things I do, I write alternate history (in Korean), which you can check the most basic background in this thread. These days I've been working on naval ships, and while most are pretty standard and easy to think about, battleships are what I might consider the most difficult to understand due to armor.

Essentially, my understanding was that with WNT restricting displacement, there were numerous ideas to make the most of that limitation. On one extreme we have the British with their thick vertical belt, and on the other we have the US cutting things to the to bone to ensure sufficient firepower and speed. Of course, there is Yamato, but let's set aside that idea with so much promise yet so much disappointment in the face of inability.

Within this kaleidoscopic realm of ideas, I'm not sure what path my star battleship, Gwangmu, should follow. For that matter, I'm pretty ignorant of how the various ideas interact and counteract each other, since if you go one path you would most likely give up the other. Furthermore, there is a wider variety of armor types, which complicates my limited understanding. While tanks are relatively easy to understand (I do some historical research freelancing for World of Tanks, and my RL work is somewhat related), the physics of naval shells impacting some specific kind of armor put in a certain specification is pretty complex, to the point I have no idea what I'm reading.

With this being my situation, I would appreciate it if someone would be willing to give me some basic overview of how battleship armor is supposed to work, so that perhaps I might have a better understanding of what kind of design my AH battleships would go for.

this might help. recently came across these cross sections.

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Well, how do each different work? What was the idea behind them? What kind of material was used in what part for what reason?

Basically (IMO in not an expert, I will add a few links at the bottom) you have a Belt and a Deck, so its really simple the belt stops short range flat stuff and the deck stops long range or bombs falling from the top. But it gets more complicated .(I will use acelanceloet nice pics, NOTE Iowa has IMO part of the turret barbet/belt shown on the picture, the 17' thick black wedge so forget that)

1) You basically have 2 styles of ships protection layout in WW2 most 30s ships USN/RN/IJN are AON (with simple single belt and deck), Germans are not with multi layers as are most of the old WW1 ships.
- You also need to decide what balance of protection you will do I how important are guns v engines or the bridge etc and decide how to use your limited amount of tonnage to protect you the best.(and it depends if you think you might have to run away or not or what range you will fight, short in bad weather in north Atlantic or in nice sunny south pacific ?)
- not you can get very complicated with decapping layers and splinter layers in-front and behind the main layers.

2) Belts can be outside (Bismark/NC) or inside (Iowa), outside is easier to fix but harder to angle.
- Why angle ? well as you angle the shell has to go though a greater thickness of belt and is more likely to deflect and fail. (this worked better as the shell starts falling from higher angles at longer range, ie 10deg inst very useful, but 10 deg and shell falling at 20 deg = 30 deg and starts to really hurt performance, think cos/sin maths )
- Other things you need to think about is it all one thickness ? or does it get thinner at top and bottom ? Hopefully the bottom will always be covered with water so its OK to make it a bit thinner (NC) (to save weight, but its hard/expensive so may not be worth it) or you could have different thickness's joined (but that opens problems with linking them and Yamato had a week join of the 12-6 part).
- That bring us on to depth it has to be deeper the larger the shell you are fighting as bigger shells travel better underwater (squared/cubed so a lot better) this lead to lots of old WW1 belt being to shallow to stop WW2 shells (15/16/18') Ideally you would have something like Yamato with thin belt going down to the bottom.
- You also have to decide how high your belt goes up, again higher is better (but weights more) as it protects more of you ship and therefore traps more buoyancy per length you have protected.

3) Deck so you have is it one layer ? is it flat ? how high is it ? is it one thickness (over mags and machinery ?) etc..
- One layer works better as its stronger than 2 layers the same thickness (and the first layer will turn a shell toward the second so its even seeker).(so Bismarck 2+ and 3+ doesn't add up to 5+)
- flat decks are stronger v shells coming in at 45 deg angle (not v bombs) (note Yamato 7 and 9 deck parts)
-High is good as it stops flooding and bombs and protects more space in your ship (but bad for weight so do you have a low thick or high thin deck ?)

4) Underwater probably the most important part as it turned out but the bit least prioritized. nobody did sufficient testing pre war its hideously expensive and most systems had flaws waiting to be found or not.

Well hope that helps I'm sure it could be better explained go have a look at.
http://www.navweaps.com/ especially search the forum (with google) its has tons
http://www.combinedfleet.com/baddest.htm
+ lots of others
Note that you don't have to agree with them (well you have to pick a side Iowa v Bismark v Yamato and then argue it for ever ) some of the best battleships in WW2 where actually WW1 rebuilds just because they where ready from the start. (best usefulness of Warspite v Iowa anybody ?)

And that brings me back to the fact that nations built what they could, not necessary what they wanted to, size limits, number of docks, dates, money, treaty, limits all played a big part to limit them.

IMO Its effectively imposable to build a WW2 battleship perfectly you just have to pick the flaws you think you can live with.

JSB

Actually didn't really answer you q did I .
1 - they try to stop shells getting to places you don't want fast moving hot bits of metal and explosive (hopeful covered above)

2 -
B, short range (low trajectory shells) in bad weather and to protect the ability to run away engines (v turrets, saving the ability to stand and fight) as you will be outnumbered raiding North Atlantic.
R + NC, longer ranges (better weather) so steeper shells hitting = more deck v belt. (note I'm ignoring Rs wider and has sloping bits)
I, the above but with deeper stuff as we have now done test and are worried about diving shells (and inside belt)
Y+ M, Limit what limit the same as R + NC but with much more tonnage to play with.
(you should look/goggle for KVG and WW1 ship to compare for different types as these are all quite similar basically Germany v USN/IJN)

3 - they used steel, 3 is types, Face Hardened armor, None Hardened (Homogeneous) armor and other ship construction steel (of different grades in each county)
FHA - used for belt etc its the best at stopping stuff (and breaks it up as it tries to penetrate).
Homogeneous - less good but flexes so better when hit at high angles such as deck (45 deg+ hits).(it will deflect the shell away from the ship without tearing a hole)
Other - depending on the county they all had different types of steels they used (all had good and bad points)
USN had lots of money so used STS (effectively None hardened armor) for lots of other parts to save weight.
Germany used high quality welding steel that was used everywhere post war (but its not cheap)
RN (and IJN who got it in 20s) used D steel cheap (don't use expensive alloys) and strong but hard to weld (at lest first versions).
other ? not sure probably got worse as you get into smaller poorer navy's.

Hi Sumeragi,

JSB's given a pretty comprehensive answer, however, there's a pretty good case study of Bismarck on Navweaps - http://www.navweaps.com/index_inro/INRO_Bismarck_p1.htm - going into detail about which areas got armoured and why.

The first, most obvious thing is "what threat are you facing?" - bear in mind that, for instance, the Dunkerques were largely built to counter a specific class of ship - the Deutschlands (Rather, more accurately, I think the Deutschlands represented the biggest threat that the Dunkerques were expected to deal with) - so what are you up against? If there's unlikely to be anything with better than 12" in theatre that will have different requirements from facing off against a Yamato.

I'm assuming that as a WoT'er you're familiar with the many benefits of angling armour already!

With regards to the armour types, belt armour is designed to be extremely hard as this is the stuff that will have low-angle, high-velocity shells slamming into it. Some, for instance Iowa have a small armour belt outside of the main armour belt - this is to defeat APC ammunition by stripping the cap off (some of the shells come in so fast that the steel that makes up the shell can shatter on impact. APC ammo adds a softer steel cap to the shell to transmit the force of the impact to the belt effectively - the additional outer belt takes this softer cap off, forcing the APC shell to hit the main belt without the benefit of this cap) - however hard steel is brittle, which is why things like Krupp Cemented (usually referred to as KC) usually only had the front third or so hardened (the exact proportions would change depending on the manufacturer and the size of the plate and the guns shooting at the plate - some USN cruiser stuff got up to 80%(!) hardened - and was damned good plate, too, for the size of projectile it was intended to defeat!) - the soft back distributes the stress around the plate better and (hopefully!) prevents the situation where the shell slams into the belt, doesn't penetrate ... but sends a shell-size chunk of armour plate bouncing around the inside of the ship anyway.

Deck armour seems to be universally softer - I've never seen it explicitly spelled out but I assume this is because something coming in on such a trajectory will be carrying less speed so doesn't require the hard-face protection that the belt will. There were various schools of thought on the best deck armour layout but the basic design was normally a heavy armour deck to stop the blast, sometimes with a thinner deck above it in an attempt to set off the shell \ bomb higher up in the ship, where it presumably wouldn't do as much damage, and then a splinter deck below that to stop any fragments that made it through the heavy deck.

Underwater protection, as JSB states, was not generally very well done, partly because (at least on the Allied side) the size of the warheads went up faster than was expected - North Carolina-class ships, for instance, were designed to stand up to 700lb-warhead torpedoes ... and the IJN was using 1000lb-warhead torpedoes. It's fundamentally a hard problem - because, unlike the belt, you've got water on the other side of the blast not air it doesn't dissipate anything like as well (and can in fact have secondary damaging effects, too) as a hit against the belt. The basic approach was to put distance between the side of the ship, where the torpedo will go off, and an important part of the hull (which will have armour plate to protect it from the torpedo blast). Various schemes existed to utilise this otherwise-void space, using it for fuel or water (which also slows down any fragments from the blast) and there were normally void spaces as well (the liquid spaces stop fragments, the air spaces, I think, attenuate the blast) - the USN had what was generally considered a very good system, with five compartments between the side and the internal armour, with specially-designed ductile bulkheads so that they would yield without fragmenting (absorbing as much of the blast energy as possible in the process) with 3 void compartments and 2 liquid compartments. The problem is, of course, that the more space you devote to torpedo defence, the less you can devote to, well, the ship. Torpedo defences normally thinned out around the turrets - the hull will be getting thinner at that point anyway and you've got to fit the turret in - something has to give and it was usually the torpedo defence. Because of the sizes required for the torpedo defence past a certain point you just couldn't carry it - these systems were generally 20 feet wide - leaving the bow and stern vulnerable on most ships.

Anyway, there's not terribly much more there than JSB wrote, but what is there is taken from various sources, largely Nathan Okun's stuff at Navweaps. I hope it's of some use.

Regards,
Adam

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