Bismarck's port rudder

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Bill Jurens
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Re: Bismarck's port rudder

Postby Bill Jurens » Tue Apr 27, 2010 12:32 am

Indeed, the rudders were aligned roughly parallel to one another as the ship was turning. But that does not mean they saw the explosion in the same way. If you draw two parallel lines and create an explosion somewhere along one of them, the rest of that particular line will see the explosion 'end on'. But the other line will see the explosion much more from the side. The situation gets worse (for the second line) as the rudders move over to an extreme position. Try it and see.

Structural distortions forward, around Turret Bruno, indeed suggest that the ship hit bow first. By then, I think, the port rudder was already gone.

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Re: Bismarck's port rudder

Postby RF » Wed Apr 28, 2010 7:34 am

Bill Jurens wrote: To me, the actual path of the torpedo prior to impact remains conjectural.
Bill Jurens.


Bill, presumably from the position of the attacking Swordfish when it released the torpedo the angle of track would be at something approaching right angles to Bismarck's stern?
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Re: Bismarck's port rudder

Postby Bgile » Wed Apr 28, 2010 1:50 pm

RF wrote:
Bill Jurens wrote: To me, the actual path of the torpedo prior to impact remains conjectural.
Bill Jurens.


Bill, presumably from the position of the attacking Swordfish when it released the torpedo the angle of track would be at something approaching right angles to Bismarck's stern?


wouldn't that depend on how much Bismarck turned before the torpedo hit her?

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Re: Bismarck's port rudder

Postby Bill Jurens » Wed Apr 28, 2010 6:26 pm

The nature of torpedo hits is such that they rarely, if ever, disclose the obliquity of the initial impact (unless they are 'duds').

Excepting a small angle which would be masked by the position of the port rudder, the torpedo that hit the starboard rudder could have come from anywhere. Although the size of the charge and the position of the detonation is important, the path which the fatal torpedo took to get to that position is really of little-or-no forensic relevance.

I'll leave that for the historians and tacticians to figure out...

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Re: Bismarck's port rudder

Postby Herr Nilsson » Fri Apr 30, 2010 3:26 pm

Bill Jurens wrote: The rudder stock broke off just inside the outer surface of the collar where the rudder passed through the shell plating.


Hello Bill,

Is there any visible damage of the shell plating near the collar?
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Re: Bismarck's port rudder

Postby Bill Jurens » Fri Apr 30, 2010 7:02 pm

Basically, no.

Certainly nothing significant.


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Re: Bismarck's port rudder

Postby Herr Nilsson » Fri Apr 30, 2010 9:36 pm

Well, that’s indeed astonishing. The rudder stock broke at its thickest part. After all, it’s a tube of 82 cm in diameter with a 30 cm bore! I would expect that the hull around the collar or the collar itself is at least deformed.
:think:
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Re: Bismarck's port rudder

Postby Bill Jurens » Fri Apr 30, 2010 10:58 pm

I think we were all a bit surprised to see that configuration, i.e. with the rudder post broken off and the collar etc. and the plating alongside not even significantly deformed. It's clear the rudder wasn't CUT off, insofar as the broken edge is inside the hole a bit. On the other hand, it appears that the rudder broke where bending stresses were greatest, i.e. just where the support from the hull disappeared, and that's just what one WOULD expect.

It's my suspicion that the gas bubble pulsations working on the broad face of the rudder blade, superimposed with the large stresses imposed by a high speed (probably rather tight) turn, augmented by hull vibration and whipping simply overwhelmed the structure, and the post failed right where the stresses were greatest. The broken face does not, at least yet, permit of close enough examination to determine if the break occurred in one go or was due to fatigue. Getting enough detail to resolve this -- assuming that the broken surfaces have not been overly-obscured by corrosion -- would probably require another expedition to the wreck.

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Re: Bismarck's port rudder

Postby 30knots » Sat May 01, 2010 3:04 pm

Thanks for all the replies and discussion gents.

Bill Jurens wrote:Yes. My observations suggest that the torpedo actually struck -- or exploded very near to -- the starboard rudder. Probably, the starboard rudder was not detached because it was essentially 'end-on' to the shock wave, i.e. had a knife-edge pointed towards the explosion. It ended up getting pushed forward into the propellers. It's my feeling that the port rudder failed because it was 'side-on' to the blast and thus presented a great deal more surface area that the starboard rudder did. To me, the actual path of the torpedo prior to impact remains conjectural.

Bill Jurens.


With the greatest of respect, and I do realise this has been discussed before, and apologise if this is an inapprpriate place to post this, but if the starboard rudder ended up being pushed into the propeller(s) upon torpedo impact, there would have been massive damage to the propeller (whichever one), the shaft and bearings, seals, internal gearing etc. All reports i have read indicate none of this occurred and that all three shafts were operating 'normally' after the torpedo hit.

Interestingly, no one has commenteted directly on my suggestion about manually turning the port rudder to the exact opposite angle of the damaged starboard rudder, in an attempt to at least giving steering with the shafts alone a better chance. My understanding is divers could indeed access the steering compartment, albeit with great difficulty.

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Re: Bismarck's port rudder

Postby Bgile » Sat May 01, 2010 5:42 pm

30knots wrote:Interestingly, no one has commenteted directly on my suggestion about manually turning the port rudder to the exact opposite angle of the damaged starboard rudder, in an attempt to at least giving steering with the shafts alone a better chance. My understanding is divers could indeed access the steering compartment, albeit with great difficulty.


I commented on it right after you made it. You apparently ignored my comment. It apparently wasn't possible for them to do much of anything in there, and they didn't "let the rudder fall out". It seems to have broken off at some point.

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Re: Bismarck's port rudder

Postby Bill Jurens » Sat May 01, 2010 9:15 pm

To 30knots:

I am not sure exactly what your sources are, but regarding damage to the propellers and rudders, etc., one must remember that most of the accounts now generally available were written well prior to the detailed examination of the wreck itself. Further, many are inherently ambiguous, either because the Germans were deliberately trying to keep information away from Allied interrogators, because a certain amount has inevitably been 'lost in translation' from German, because many secondary sources simply repeat -- often with slight elaborations -- the text of the original source material, which is actually quite meager, and because the German appreciation of the extent of the damage, which could not easily be fully evaluated 'on-site' was itself rather sketchy, insofar as many flooded compartments were never de-watered or examined in detail. This can cause problems. One good example of this is the oft-seen description of the floor plates in the center engine room being displaced about a half-meter, with no reference to whether this represented a permanent or a temporary deflection. What IS clear, is that anything written prior to about 2002 -- including some of my earlier work -- must now be reinterpreted and re-evaluated int the light of much more recent discoveries.

The rudder and propeller area of Bismarck has been examined in great detail by at least two expeditions with access to high quality cameras and recording equipment. While detailed examination of the resulting videotapes conclusively shows that the forward edge of the starboard rudder definitely did intercept the center propeller, the precise duration of that impact and the subsequent damage to the propeller (part of which remains buried in the sediment) and the propeller shafts, etc. remains somewhat conjectural. Although I do have have my own opinions, It's really an area where honest, knowlegeable, and intelligent men can disagree, or at least so far HAVE disagreed. The forensic team will, I think, be able to eventually reach a consensus on this, but that has not yet been done.

It is obvious from an examination of the videotapes that there would have been no hope whatsoever in attempting to move the starboard rudder after it was damaged. Regarding your suggestion to re-align the port rudder, It is not clear whether the port rudder was even on the ship after the torpedo explosion, so the effects of any attempt to move it to any particular position are again somewhat conjectural. That being said, and assuming the port rudder was actually there to move, moving it to a position where it in some way compensated for the erratic effects of the damaged starboard rudder -- and admitting that I have done no formal calculations regarding this issue -- it's likely I think that the resultant drag would have been so high that the top speed of the ship -- and the ship's subsequent endurance -- would both have been quite small. In that regard, I am not sure that such a rudder manipulation, even if it were done, would have had any significant impact on Bismarck's final fate. Tactically, steaming at (say) 8 knots in a straight line is probably not that much more productive than steaming at (say) 12 knots in circles. In either case, I don't think that Bismarck would have had enough time and fuel to reach France before being sunk by British air or surface attacks.


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Re: Bismarck's port rudder

Postby George Roumbos » Sun May 02, 2010 8:28 am

Interesting discussion :ok:
I'll copy and paste here what Antonio wrote and I seconded it as being one of the translators when we met, sat down and had lunch with the Bismarck survivors:

"from the information I have collected from a Bismarck survivor on May 2005.
He was very close to the Bismarck stern when the ship capsized and noticed this very clearly :

1) The 3 propellers were all still running when the ship capsized.

2) No rudder was obviously jammed into any of the 3 propellers.

3) Bismarck went down like an ' elevator '.
He ment Bismarck presented herself vertical on the sinking process, stern went down first and last the bow.

This means that the damage on the starboard rudder and the consequent jamming into the center propeller was caused by the hit on the bottom of the ocean.

It should be very interesting to analyze correctly current damages on the hull structure and determine how really Bismarck hit the ocean bottom.

How come the stern was separated by the hull, the rudder jammed the propeller and how the bow section was lifted up causing such a damage on the B-Bruno barbette area.

I am sure a good analysis can recreate the whole process.

Moving on the torpedo hit area, it should be first of all determined were the torpedo hit the Bismarck, and from what I saw on the wreck photos and film it is an area not so close to the rudder.

Hope to have provided some clear elements for addittional evaluations."

But not only that... the survivor was actually part of the damage control team sent to investigate the 3 prop shafts / tunnels after the torpedo hit.
They ALL reported back that ALL 3 shafts were undamaged, no water was to be found in the tunels and ALL 3 props were still turning.

Nevertheless it is a very interesting topic :cool:
"Ich lasse mir doch mein Schiff nicht unter dem Arsch wegschiessen. Feuererlaubnis !"

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Re: Bismarck's port rudder

Postby Bill Jurens » Sun May 02, 2010 6:21 pm

Hello George:

Thanks for posting this.

It's not uncommon when visiting wrecks to find numerous instances where the testimony of survivors just couldn't possibly be true, which over the years generated the well-known forensics phrase "...the steel doesn't lie." This does not, of course, suggest that the witnesses were being deliberately deceptive -- although this phenomena, especially in mercantile cases where insurance is involved -- is far from unknown, just that in the heat of battle, every man sees things somewhat differently. In the case of Bismarck, for example, I have read witness reports that clearly stated that the shell plating was undamaged from torpedo hits as well.

That being said, the observations you quote are not necessarily incompatible with our examination of the wreck on the bottom. In the previous memo, I was quite careful to state that there is a good possibility that the rudder/propeller interference was momentary. The rudder is not in interference with the propeller now, and although I suspect that this is due to hydrodynamic effects which in effect pushed the rudder back towards the stern immediately after the blast, it is admittedly sometimes quite difficult to sort out damage from the torpedo explosion itself from possible modification of the rudder position due to impact with the bottom and the subsequent slide. On the starboard side, the rudder supporting structure is quite heavily compromised and it is difficult to tell exactly how resistant to exterior forces the remaining structure actually is, or was. There are some aspects of the rudder damage which are clearly due to explosive effects, other aspects which are quite probably due to the bottom impact and subsequent slide, and some aspects which remain ambiguous.

The supporting structures around the center shaft was, by the standards of most other navies, remarkably robust, with heavy structural bulkheads supporting rather closely spaced spring bearings. This lends some credence to the conjecture that the effects of the torpedo explosion and the subsequent rudder displacement into the propeller may not have had much effect farther up the run of shafting forward. (On the other hand, one must account for the half-meter displacement of plating in the center engine room. )

My documentation suggests that the after portion of the shaft tunned was indeed flooded well before the ship sank. How rapidly this flooding occurred remains undocumented, and it is my feeling that the flooding probably occurred not directly 'from sea' but farily slowly from adjacent trimming tanks which had been counterflooded on 24-25 May. The after portions of the shaft tunnel were probably not easy to get into, and it is possible that a failure of one of the shaft couplings far aft might not have been noticed unless the tunnel was examined in detail from end to end, i.e. the forward portion of the center shaft may have visually continued to turn almost normally while the propeller itself remained essentially stationary. (alternatively, the propeller keys might have failed.) Further, an immediate -- and perhaps somewhat cursory -- examination of the shaft tunnel for immediately obvious damage might not have revealed slow leakage from adjacent tanks which could have flooded the after tunnel over a period of hours instead of minutes.

The forward section of the shaft tunnel and the center engine room are recorded as being flooded before record-keeping efforts were abandoned later in the action on 27 May. If the ship was indeed scuttled by flooding the engineering spaces, I would consider the report of "all three propellers still turning" to be improbable.

The last James Cameron expedition to the Bismarck was detailed enough to allow the R.O.V.s to enter the after torpedo hole directly and penetrate some distance into the hull, so we do know a good deal about exactly where the hole is and what it looks like.

The damage to the shell plating around turret Bruno is strongly suggestive of an initial bow-first impact on the bottom. The damage caused by the subsequent slide, has unfortunately 'over-written' much of the damage that occurred prior to the sinking.

I would very much like to learn more about the survivor testimony you mentioned in your memo, especially regarding the shaft tunnel situation, as these reports are certainly not in agreement with other damage control records. Do you know how many men were involved, how far they actually proceeded into the tunnel, and exactly when their examination was conducted?

Bill Jurens.

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Re: Bismarck's port rudder

Postby Herr Nilsson » Mon May 03, 2010 11:35 am

One good example of this is the oft-seen description of the floor plates in the center engine room being displaced about a half-meter, with no reference to whether this represented a permanent or a temporary deflection.


Well, I’m not sure, if there is a misunderstanding regarding the German word “flurplatte”. (It’s seems to be a little bit like the “corn”-“Korn” mistranslation of the postwar period.)
The testimony of Junack says that “Flurplatten” were “hochgeschleudert”. “Flur” means not floor, but corridor. Not the inner bottom was displaced but the plates of the corridors between the turbines and other machinery in the center engine room. These corridors were on a higher level than the inner bottom and a lot of the plates were removable to gain access to the inner bottom level. “Hochgeschleudert” means these plates were thrown up …. and probably fell down with no further effect.


The forward section of the shaft tunnel and the center engine room are recorded as being flooded before record-keeping efforts were abandoned later in the action on 27 May. If the ship was indeed scuttled by flooding the engineering spaces, I would consider the report of "all three propellers still turning" to be improbable.


IIRC the turbines were capable of running even in a flooded engine room. The question is whether boilers were still producing steam.
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Re: Bismarck's port rudder

Postby George Roumbos » Mon May 03, 2010 1:42 pm

Bill Jurens wrote:Hello George:

...
I would very much like to learn more about the survivor testimony you mentioned in your memo, especially regarding the shaft tunnel situation, as these reports are certainly not in agreement with other damage control records. Do you know how many men were involved, how far they actually proceeded into the tunnel, and exactly when their examination was conducted?

Bill Jurens.


Thank you for your long and well placed reply.
The survivor told us that three men were sent to examine each shaft. When I asked him if he went to the starboard shaft, his reply was that he didn't examine te starboard shaft but the center one.
How far they proceeded is unknown to me as no one asked him...
I'd suggest you attend thiw year's Bismarck meeting in Hamburg on May 27th and I'll be happy to give you the name of the survivor we talked to back in '05.

Best rgds,
George
"Ich lasse mir doch mein Schiff nicht unter dem Arsch wegschiessen. Feuererlaubnis !"

George "tango-echo" Roumbos, Hellas

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