Naval History Forums

August 1945

Wertheimer's comment is based on the faulty premise that the German arrangement must trade off horizontal protection.

Dave Saxton wrote:Wertheimer's comment is based on the faulty premise that the German arrangement must trade off horizontal protection.

I suspect that it is slightly more complicated. A battleship's survival may depend on the armoured raft from the keel to the main armoured deck. If damage causes flooding above the armoured deck and especially if shell or bomb damage allows water to move between compartments above the main deck, the battleship is likely to sink. Thus a ship such as Bismarck with a relatively low main deck must have a larger proportion of its hull as part of the armoured raft than a ship such as Yamato or South Dakota. As the Bismarck designers were happy with four turrets, this was probably not a worry to them. However, I am not sure if the Bismarck armour scheme would work for the shorter armoured raft designs and it would not have allowed boilers to be above the engine rooms. The consequence is that Bismarck had 50 mm + 80mm or 100mm while South Dakota had 38 mm + 146 mm or 154 mm + 16 mm (I have seen a weather deck of 1.25” rather than 1.5” mentioned and the main deck is a laminate of 135 mm or 127 mm on 19 mm). Thus South Dakota's shorter but deeper armoured raft allows it to have a greater total thickness of armour even if Dave will argue that the effects of decapping and yaw and the avoidance of laminated layers allow Bismarck to have similar resistance to shells.

Mostlyharmless wrote:...even if Dave will argue that the effects of decapping and yaw and the avoidance of laminated layers allow Bismarck to have similar resistance to shells.

Yes I would, and I agree with many of your points Mostlyharmless. Nonetheless, there is little to no trade off in horizontal protection to gain Bismarck's superior vertical protection. Wertheimer apperently assumed such a trade off was/had to be made.

..thus South Dakota's shorter but deeper armoured raft allows it to have a greater total thickness of armour...

This points out some of the efficiencies of the Bismarck's arrangement.

A couple of points about the pros and cons of the low armored deck on Bismarck. Assume that this deck forms a flooding boundary, (a) the lower boundary for shell hits from above and the upper boundary for underwater damage from mines, torpedoes and shell hits that pass underneath the belt. Undoubtedly, a low armored deck has disadvantages in case (a), especially if there is a free water surface, as probably contributed to the loss of Kirishima. However, in case (b) the low armored deck is advantageous, as it limits the flooding from below. Looking at appendix A in Axis battleships by Dulin and Garzck, which details a number of underwater damage cases, some severe, one sees that raising the armored deck would increase the loss of buoyancy and stability in cases A-2 to A-5. And even in case (a) there will be instances where there is a leak after a non-penetrating hit on the belt, which will result in more water being shipped and a greater resultant list than for a ship with a low armored deck sloped down to the bottom of the belt.

Bismarck aslo had several longitudinal bulkheads between the 2 armored decks, which would have also funciton as flooding barriers. Also, the reserve buoyancy of the ship was very large.

Yes, and Bismarck also has a wide margin of GM. Loss of stability to above panzer deck flooding is highly unlikely.

Remember that at realistic operational displacements Bismarck's panzer deck is at least 1 meter above the waterline. This point is stressed by Chief Engineer Toebicke in MA6. It would require considerable settling without much list or trim to enccounter expansive flooding above the panzer deck. If there was enough flooding below to settle the ship level by that much, then it would likely further increase the GM margin. The area above the scarps also acts as sumps for minor flooding.

Another advantage of the upper belt is that the waterplane remains armoured (unlikely to be riddled by splinters) even with rather drastic settling.

Historcally, the kind of thing theorized about Kirishima did not happen to Bismarck during the final battle.

The ship's pumping capacity should also be emphasized, as I understand it was allmost double from that of contemporary battleships ?

Do you have specific information about the Bismarck's pumping capacity in relation to contemporary battleships?

RobertsonN wrote:Do you have specific information about the Bismarck's pumping capacity in relation to contemporary battleships?

No, but here's the source:
viewtopic.php?f=2&t=629&hilit=pump&start=30#p35007
Bismrack had about 16.000 tons/hour pumping capacity...

No, but here's the source:
viewtopic.php?f=2&t=629&hilit=pump&start=30#p35007
Bismrack had about 16.000 tons/hour pumping capacity...

Needs to be put in perspective, otherwise the figure alone is not representative for a qualitative approach trying to compare different battleships.

For what´s worth, the pumping capcity of SMS BADEN according to Goodall´s report was 11,121 tons/hour.
But BADEN was -of course- kind of a smaller vessel.

As big as Bismarck was, you'd think they'd have used some of that tonnage for bigger guns. Wasn't 8x15" kind of... light, for 1940?

yellowtail3 wrote:As big as Bismarck was, you'd think they'd have used some of that tonnage for bigger guns. Wasn't 8x15" kind of... light, for 1940?

Yes it was...
They devoted much more attention to protection than to offensive power...
My speculation is that they did this knowing the ship would fight at a disadvandtage in numbers, so they armored it as best as possible to ensure survivability in hostile waters.

alecsandros wrote: They devoted much more attention to protection than to offensive power... knowing the ship would fight at a disadvandtage in numbers, so they armored it as best as possible to ensure survivability in hostile waters.

There is an irony here - if there is a disadvantage in firepower, with no real regard to the 35,000 ton weight restriction, why not beef up the firepower? Say with triple turrets of 15 inch and triple turrets of 5 inch DP in place of the 5.9 inch and 4.1 inch batteries? That could have been done without substantially reducing armour protection? Or speed?

If it is the case of ''single ship'' syndrome, then Bismarck/Tirpitz could have been used as a pair like Scharnhorst and Gneisenau.....

Thinking further there is one interesting question.... if the Japanese had been commissioned to design and build a Bismarck for the Germans, just what would they have come up with? Or indeed an American shipyard?