Bismarck construction flaws

[Monitor]

This subject is often discussed in military and naval circles.
Can somebody enumerate Bismarck construction flaws and their possible impact on the ship's final demise?

[Javier L.]

Hello all,

One flaw was the 10.5 cm battery installed in two different type of mounts (L/31 and L/37), this was corrected on the Tirpitz. Some people will argue about the 3-shaft arrangement, the armor distribution, or weak stern, but I don't think a construction flaw was responsible of the ship's final demise. The fate of the Bismarck was sealed when the rudders were jammed and her steering disabled after an unfortunate torpedo hit. It doesn't matter how well (or bad) constructed the Bismarck was, it could happen to any ship. An Iowa Class battleship in heavy seas 600 miles off the nearest harbor with both rudders jamed 12 degrees to port would have suffered the same fate.

[Bgile]

Not having the capability of remote pumping of the forward compartments containing fuel has been mentioned.

Her AAA was hopelessly deficient but that was in common with most of her contemporaries in 5/41. Lack of a DP secondary has been mentioned but the Japanese had the same failing and the British 5.25" was a failure in that regard - only the US got it right with the 5"/38 in their new BBs. Really, the state of AAA technology was poor at the time of her sortie and that definitely contributed to her demise.

I initially mentioned luck, but removed that para because that has nothing to do with the design. Luck works both ways, too.

[pdfox99]

How about the inability to steer without rudders? I believe they tested this during her trials and it was discovered, but too late for changes. In addition, the rudders could not be blown off if damaged beyond repair.

[Javier L.]

Months ago I had a discussion with a Spanish friend about this.

Steering without rudders, or locked in an amidships position, is always very difficult. If the rudders are jammed 12 degrees to port steering is even more difficult. It is well known that the Bismarck couldn't steer with propellers alone when her rudders got jammed, but I don't think this was caused by the 3-shaft arrangement like some people claim.

The Prinz Eugen had 3 shafts too, and when in 1942 she was torpedoed off the Norwegian coast losing the stern and rudder, she still managed to steer with propellers alone and reach safety unlike the Bismarck. This is a coincidence but the P.Eugen was torpedoed in about the same place as Bismarck, and hit by more powerful torpedo (21 vs. 18 inches).

If Bismarck had trouble steering with propellers alone, other factors caused that most likely: Her big size when compared with P.Eugen? Convergent design of her propeller shafts? Did the Hipper or Scharnhorst classes have convergent shaft designs too?

Finally, are there any other examples in history of battleships trying to steer with propellers alone?

Javi

[foeth]

Convergent design of her propeller shafts?

I think converging shafts are actually beneficial for steering, though not that it would matter much, the angle is always very small. I doubt tripple of quadrupple shafting arrangements in itself are any cause for how good the ship will steer, but rather the interaction between propeller and lateral hull surface area. I'd like to know a little bit more about it, I think that the South Dakota's should have very poor propeller steering behavior, Iowa a lot better, purely due to skeg location.

[Javier L.]

Hello Foeth,

I agree with you, I think that converging shafts must be better for steering that no convergence at all. It is Müllenheim-Rechberg who wrote that only using her engines with both rudders locked in an amidships position, the Bismarck could be held on course only with great difficulty. The reason for this being that the convergent design of her propeller shafts provided only a weak turning movement, even with the outboard shafts rotating in opposition at full power.

I have just checked blueprints of the Scharnhorst class and noticed that unlike Bismarck, their shafts had no convergence at all. What about American battleships, were their shafts of a convergent design?

[Bill Jurens]

The convergence (or non-convergence) of shafts has no effect on steering with propellers at all. It's a common lay-misconception. The whole idea of this is based on the concept that somehow one propeller 'pushes' while the other 'pulls'. This couple is inconsequential compared with the hydrodynamic effects caused by pressure differences on both sides of the hull surface aft.

Bill Jurens

[Bill Jurens]

One will note a very significant -- though rarely discussed -- flaw in the side protection system. If one looks at the cross section through the engineering spaces, for example, one finds that at the bottom of the engine rooms there is a space a few meters high where the protection system is actually ONLY ONE PLATE THICK, disregarding the shell! This is an area of extreme vulnerability, particularly insofar as the area where a breech would occur would be difficult to get at at best, and very become completely inaccesible once flooding commenced.

This represents, in design terms, a fairly substantial 'boner'.

Bill Jurens.

[foeth]

The whole idea of this is based on the concept that somehow one propeller 'pushes' while the other 'pulls'. This couple is inconsequential compared with the hydrodynamic effects caused by pressure differences on both sides of the hull surface aft.

The interesting thing is that if you use the push/pull theory you may have a hard time explaining why the ship is moving in the other direction. Bit like a ship with some forward speed being pushed to the side by tugs steering into the tugs, not away from them as you'd expect.

[Javier L.]

The convergence (or non-convergence) of shafts has no effect on steering with propellers at all. It's a common lay-misconception. The whole idea of this is based on the concept that somehow one propeller 'pushes' while the other 'pulls'. This couple is inconsequential compared with the hydrodynamic effects caused by pressure differences on both sides of the hull surface aft.

I think it would be marginally better than a non-convergent design. At least in theory.
Considering that Scharnhorst's shafts were non-convergent (they even look a bit divergent to me!! ), I wonder what made the Germans adopt a convergent shaft design for the Bismarck class.

[Bill Jurens]

The convergence or divergence of the shafts, like the rake (vertical slope) of the shaft lines, is usually more-or-less a non-issue. The naval architect decides where the propellers must be using hydrodynamics as a guide. The engineering people (and perhaps the N.A.) decide where the engines must be. One joins the end of the engines to the centers of the propellers with straight lines. Provided that the shaft lines do not cause too much difficulty with arrangments aft, e.g. provided they do not interfere with other required functions aft, then one is essentially 'good to go'. Otherwise some rearrangment must be done. But nobody really cares exactly what the shaft angles (which are always quite small in any case) actually are so far as propulsion is concerned.

Few people realize that the shafts on a multi-shaft ship are rarely symmetrical. Usually the rake angle and the convergence/divergence are different for each shaft in a multi-shaft system. This is because the propellers are almost always fixed in a symmetrical location, but the engines are often at different fore-and-aft points in the hull, and often vary in their transverse locations as well.

Convergence/divergence would not have had -- and does not have -- any significant effect on maneuverability per se. At best, it's a second or third order effect.

Bill Jurens.

[tommy303]

Bill,

The gap in the side protection system of which you speak: is it the one where the wireway-passage way was used as a holding bulkhead to contain any leaks in the main torpedo bulkhead. If so I have noticed that as well.

[Bill Jurens]

No, this defect -- a much more serious one -- occurs right at the bottom of the holding bulkhead, just at the junction with the inner bottom. At that point you have the shell, the holding bulkhead and nothing else. In other words, if the outboard tank is full, you could stand in the inside of the engine room, put your hand on the inside of the bulkhead, and essentially have only the ocean on the other side. If the outboard tank is empty, than the holding bulkhead is directly vulnerable to fragments etc.

Very bad.

Bill Jurens

[tommy303]

Bill,

Oh yes! I see what you are talking about. I wonder what the reasoning was behind that, or if it was simply an oversight in the rush to build the ship. I wonder why the inner boundary of the outboard void was attached slightly above the double bottom on the torpedo bulkhead instead of curving down into the inner bottom where it would be better supported. It also seems to me that the attachment point on the torpedo bulkhead would cause undue stress on the torpedo bulkhead should the outer void be flooded by damage or flooded as a counterflooding measure.

thomas