Bismarck's TDS so abysmal?

[spicmart]

Hello,

I read this in an internet group about dreadnoughts:

The guy firmly believed that the TDS of Bismarck is practically non-existent.

no system of underwater protection was provided in bismarck apart from that afforded by an outside air space (between the skin plating and the wing oil-fuel tanks) and her protective bulkhead.
Abreast the forward engine rooms and boiler rooms, there were no wing compartments, so that any leak in the protective bulkhead in these areas would have resulted in the flooding of a major machinery compartment.
This is a serious deficiency when one considers that bismarck had ten feet more beam than the majority of older battleships, and fifteen feet more than the kgv class
And if you look at this pic where the red arrow is there is no protection between the machinery space and the outer hull.
I showed this photo to an experienced RN Naval Architect (I have his qualifications should you require them) and he said
"That cross section is interesting. I hadn't appreciated the structure of the TPS just above the red arrow was so dislocated - any blast in that region would punch the frames through the holding bulkhead into the machinery space.
One of those structural discontinuities that we make sure young engineers don't create"
Ist möglicherweise ein Bild von Text „50 KBismarck.com com 145 30 320 45 110 80 170 45 Bismarck midship section“

[Steve Crandell]

Can't view the image you posted.

[spicmart]

Hope that works.

[Thorsten Wahl]

i cannot see any of your pictures

[Herr Nilsson]

This one?


From the construction flaw discussion:
http://www.kbismarck.org/forum/viewtopi ... 1459#p1459

[spicmart]

Yes, Herr Nilsson.
That's the one!
At least the same spot is meant.

[SteveSmith]

On the Iowas and SODAKs their are four torpedo bulkheads compared to Bismarck's two. The supports on the inner two bulkheads are staggered so that the those for bulkhead no. 3 are at half frame locations. If there were a blast against bulkhead No. 3, there is no bracing to transmit the force directly to No. 4—as the diagrams above show would happen on Bismarck.

[Bill Jurens]

My thanks to Herr Nilsson for re-posting the previous correspondence on this.

I must admit that I remain somewhat baffled as to exactly how this sort of apparent flaw actually made it through the construction process.

There are three primary possiblilities:

1) That the designers of the ship just didn't think this out properly -- which I feel is unlikely, because most or all of them must have been, in reality, pretty smart guys.

2) What appears to be a flaw, actually isn't a flaw, and our negative interpretation of this feature resides in our incomplete or incorrect understanding of the full situation.

3) That the design was actually somewhat different originally, some changes occurred elsewhere, and that for some reason the flaw was recognized, but retained because no alternatives presented themselves.

Certainly this sort of arrangement would be very vulnerable to a deep-running torpedo, and problems would be exacerbated because a) without an intermediate void, which would at least slow down immediate flooding of the engineering spaces whilst it was filling up itself, any leakage into important interior spaces would have taken place immediately, and b) the source of this flooding would likely have originated low down close to the floor plates, which would mean the source might be quite quickly submerged and difficult to locate or access. There are other problems, too, insofar as this area is quite far from the ship's neutral axis in bending, which means it would typically be expected to be carrying high loads as the ship flexed in a seaway, etc.

The idea that some of the interior structures inside the protective system would have been capable of 'punching through' the holding bulkhead, might not represent a serious threat, as it's typically of fairly light construction anyway, but is still something you really do want to avoid. Structural items attached to the holding bulkhead should be, as much as possible, located on the inboard side, or arranged in such a way that they fail in tension as the holding bulkhead deflects inboard.

Comments very welcome indeed...

Bill Jurens

[Thorsten Wahl]

A detonation of 300 kg S1 produces a bubble of about 8,5 m diameter.

therfor the TD-bulkhead is possibly within direct reach of the primary bubble.

The bulkhead is a continous plate from the bottom of the ship up to about 70 cm above armor deck.

I dont know if a 45 mm Ww- bulkhead can withstand the force of explosion at this distance if placed perpendicular to the detonation.

But the bulkhead is supported by the double bottom wich probably gives way, if the bulkhead is not destroyed by the primary detonation forces.

All structural plates attached to the TD-bulkhead are 10 mm or 8 mm except the bottom hull plate

all plates adjacent to the T bulkhead are connected with multi row riveting (3 rows if i remember correctly)

[Herr Nilsson]

2) What appears to be a flaw, actually isn't a flaw, and our negative interpretation of this feature resides in our incomplete or incorrect understanding of the full situation.

I think 2) is possible. This kind of "gap" already existed on the large cruisers of the Mackensen-class and the subsequent designs. So they had almost 20 years to think about it and fix it, but they kept it in a very similar way on Scharnhorst-, Bismarck- and the projected H-class.

PS: A substantial part of the affected lower oil bunkers amidships was screened by the bilge keel anyway.

[spicmart]

2) What appears to be a flaw, actually isn't a flaw, and our negative interpretation of this feature resides in our incomplete or incorrect understanding of the full situation.

I think 2) is possible. This kind of "gap" already existed on the large cruisers of the Mackensen-class and the subsequent designs. So they had almost 20 years to think about it and fix it, but they kept it in a very similar way on Scharnhorst-, Bismarck- and the projected H-class.

PS: A substantial part of the affected lower oil bunkers amidships was screened by the bilge keel anyway.

Would it be conceivable that the bilge keel had been included into the TDS or is that nonsensical?

[José M. Rico]

Hello,
In my opinion, the German designers were very well aware of this feature and didn't see this as a flaw. In fact, the same construction geometry appears again in the next H-Class battleships. Moreover, I don't believe, the underwater protection would have been improved at all fixing this "flaw" by connecting the inner floor to the wing bulkhead. A deep-running torpedo hit in that place would be dangerous regardless. We could even argue if adopting this lower "gap" provided better structural strength overall against torpedoes hitting the hull sides at normal depths above the bilge keel.

Thorsten pointed out something important too, and that is that the 45-mm bulkhead goes all the way down to the bottom plate (I think it would be a mistake if it didn't), and the subdivision of double bottom serves as structural support for the bulkhead. The torpedo bulkhead in the South Dakotas and Iowas for example, didn't extend all the way to the bottom plate.

[José M. Rico]

By the way, does anybody know the exact distance of this "gap" amidships?
I calculate something between 40-50 cm.

[spicmart]

At the position of turret Anton the minimum distance of the TDS to the barbettes is only 3 m. How would you rate this "weakness"?
How were other battleships protected against torpedoes in this area?

[Bill Jurens]

To Mssrs: Rico and Nilsson:

By my measurement, the height of the 'gap' appears to be around 500 mm. The idea that the bilge keel might serve to 'screen' the side protection system is interesting, but I am not sure whether the advantages of having the torpedo detonate somewhat farther outboard might be somewhat reduced by the effects of heavier structure, i.e. parts of the bilge keel itself, possibly being projected inboard by the explosion itself. The desire to reduce fragmentation was one reason why, in general, shell plating, etc. in these sorts of large vessels was deliberately kept fairly light.

The true answer to this might, in practical terms, be essentially unknowable at this stage...

Bill Jurens