"Armor on the Bismarck" Topic

Conway's lists the Bismarck as having a 12.5" belt. It also describes 4" deck slopes.

I was under the impression from some other books I read that sloping deck armor somehow contributed to the horizontal protection.

How exactly did it contribute? Did it slope down so far as to be behind the main belt, forming in essence an inner belt? Something else? Was my impression wrong?

The second part of my question is, if the sloped deck armor didn't offer additional horizontal protection, why is so much fuss made over the Bismarck's armor scheme? (excluding the Bismarck is teh roxorz folks) It seems significantly less well armored than many of the contemporary American battleships. Was it just because the actual combat record shows it standing up to so much pounding?

Bismark wasn't all that well-armored by WW2 standards. In fact, she was armored to WW1 standards, which is why she is often called an 'improved Bayern' class battleship.

WW1 armor schemes looked like an armored 'bathtub' – side armor was vertical, and there was a heavy armored deck carried low down that connected them. This is great against shells coming more or less parallel to the water, that is, from short range. As luck would have it, the Brits chose to hammer her from short range, so her armor scheme worked well in keeping the ship afloat. Of course all the major combat systems were knocked out, since the armor didn't protet them. But she floated!

Between the wars, battleship armor schemes were re-arranged to provide better protection from plunging shells. So better deck armor, carried across the tops of the main belt, to prevent plunging fire from reaching the machinery spaces. Side belt armor was now inclined inward slightly, so that plunging shells would be diverted downwards into the water. A good example of this would be USS North Carolina.

So, in short, Bismark "lucked" into a situation where her obsolete armor arrangement worked in her favor. If the Rodney had stood off and dropped shells from long distance I don't think she would have lasted as long.

The sloped deck did help the Bismarck deflect shells fired at shorter ranges. Ranges that were the average of North Sea due to weather effects. The 4" sloping deck would add 8" of effective horizontal armor giving it maybe 20.5".

US ships were designed to be effective in the Pacific as well. There expected ranges were to be very long where the chances of plunging fire would be much greater. The later US designs also had a thin outer belt that acted to decap AP caped shells before they impacted the face hard main belt. Which seems to calculate out to another 20% of armor effectiveness.

Excellent. Thanks guys.

Depending on the angle of impact, sloping just means there is more armor to go through.

"How exactly did it contribute? Did it slope down so far as to be behind the main belt, forming in essence an inner belt? Something else?"

It depends. First, not all ships had sloped horizontal decks. The Americans did not care for them, for example.

On some ships, such as Yamato, the horizontal deck was higher than the edge of the main belt, and the slope swept down to meet the top of the belt – sort of forming a beveled box-top to the armored box.

Like this:

/-------\
|…….|

On others, Bismarck included, the armored deck was at about mid-belt level, and the slope swept down to meet the belt at or near the bottom of the belt – which would indeed provide further reinforcement for the belt. In such cases, the slope would provide a second layer of thick protection, like this:

| _______ |
|/………..\|

This arrangement contributed to Bismarck's reputation for being comparatively well protected.

Ignore the periods, BTW.

BTW, last night I was in a B&N and saw a new book out on Bismarck that some of you MAY (I'm not making a recommendation one way or the other,) be interested in:
link

The following link may also be useful:

link

It compares the major modern battleships of WW2, trying to determine the 'best.'

You must also never ever forget the power of propaganda. And by that I am talking British propaganda.

Who would want the biggest ship in their navy (Hood) sunk by anything but the most powerful ship afloat?
Then when they sank it, well….it sounds much better if your navy has just sunk the best there ever was.

There are many myths that grew up around the Bismarck and modern historians are helping to dispell them. Similarly the Italian ships were made light of, and put down as useless, for propaganda purposes. If you cant out run them to sink the darned things…the next best announcement is to say they are a bunch of cowards and didnt want to fight.

Sifting through those issues to find the facts, is an important part of Naval research.

Well. . . as it turns out. . . Bismarck didn't do so well in tonight's playtest so the armor issue didn't come into play for very long. Freak magazine hit from a carrier strike by Ark Royal on the first turn settled her for the game.

Funny thing is, both me and the guy playing her just "knew" she was going to get a rudder hit. Well. . . the rudder got destroyed too I guess.

Still the German player sallied on. Genisenau, Graf Spee, and Prinz Eugen, supported by a division of 1936A destroyers gave a good account of themselves against Hood, PoW, and a handful of British cruisers and destroyers.

Had Bismarck been present, things would not have gone well for the British. . . so I guess Ark Royal was the hero of the day – easily outclassing Graf Zeppelin.

Hello Everyone.

Reading the above discussion raises a number of questions I was hoping someone could answer for me please.

The Bismarck appears to have had two armoured decks – one that was 50mm-80mm thick and then the main armoured deck that was 80-120mm thick.

What I would love to know is this:
What is the purpose of two armoured decks? Why not have just one thick deck 130mm-200mm thick? Which type of method was more effective – the "all or nothing" approach or the dual decks that seem to have been used in most WWII German ships?

Thanks in anticipation.
Andrew.

On modern USN battleships, there were three armored decks: a thin "bomb deck" to stop non-AP projectiles and to start the delayed fuses on anything that might penetrate; the main armored deck that's meant to stop everything; and a thin "splinter deck" below that, to contain shell splinters from anything that got through the main armored deck.

It sounds like the Bismarck used the same idea, but no splinter deck. If the upper deck starts a shell's delayed fuse before it hits the main deck, it will probably go off before it has a chance to penetrate that main deck.