Bismarck construction flaws

Discussions about the history of the ship, technical details, etc.
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Dave Saxton
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Re: Bismarck construction flaws

Postby Dave Saxton » Thu Jun 24, 2010 8:19 pm

The elongation metric is just a general indicator of ductility. It varies with hardness and tensile strength that the material is treated to. The elongation of Wh was not significantly different from STS per hardness up to 80kg/mm2. At 80kg/mm2 it was about 23-25% elongation, and at 70kg/mm2 it exceeded 25% elongation. At 90kg/mm2 it was about 20%. If one were to plot a graph of elongation vs tensile strength, one would find that the elongation plot for Wh would not plot as a straight line. At more than 75kg/mm2 the curve flattens out a bit so that it remains around 20% elongation through a wide range of tensile strengths. German homogenous armour for tanks ..ect..was often much harder than that used for ships, as well as of different compositions. Hoyer stated that the usuable range of tensile strength of homogenous armour for use in ships was from 70kg/mm2 to 90kg/mm2.
Entering a night sea battle is an awesome business.The enveloping darkness, hiding the enemy's.. seems a living thing, malignant and oppressive.Swishing water at the bow and stern mark an inexorable advance toward an unknown destiny.

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Re: Bismarck construction flaws

Postby tnemelckram » Fri Aug 27, 2010 3:58 am

Hi All!

After reading the radar discussion above, especially where it got to the point of whether Bis had a radar advantage over other ships it would engage in 1941, the I have a couple of questions for Dave. But first a brief three point preface.

a. It seems to me that the critical type of radar in a fight would be fire control, not sea search.

b. As far as I can recall, the discussion about Bismarck's Seetack(sp) radar on all threads has focused on the relative merit of her sea search radar. That's probably because the strategic driver of her mission was to stay hidden or if found get lost, so detecting the presence of enemy ships before they detect you is a critical advantage. Bismark lost n' found is also the thing that gives the story its drama. So it's only natural that the focus would be on her sea search radar capability.

c. I think that some or all of the new US BB's had a unique FC advantage because at some point between 1941 and 1945 their FC radar was tied into the main battery so that the guns could automatically maintain their bearing on target even while turning.

So my questions for Dave:

1. DO you regard Bis' FC radar as being equally advanced and thus conferring an advantage equal to her SC radar?

2. Did the US ships when they were launched by May 1941 already have the FC capability in c. above?

3. Did c. actually provide a practical and substantial FC advantage?

4. Was c. as I believe "unique", or at least, the only one that actually worked?

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Re: Bismarck construction flaws

Postby Thorsten Wahl » Fri Aug 27, 2010 6:50 am

c)
see my post here
viewtopic.php?f=1&t=1145&start=900#p34581





short sketch of german fircontrol
to my current knwledge
radar for range was first used in 1940 - circuit either
sketch reproduces this
download/file.php?id=206
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Re: Bismarck construction flaws

Postby tnemelckram » Fri Aug 27, 2010 9:28 am

Thank you Thorsten!

That pretty much answers all four of my questions.

Looks like the Germans were on the same track and timing as the US regarding FC radar. I guess they just lacked ships, interest or both to put it to work and make it better known. Looks like the biggest advantage of the US system was that it was actually put to widespread use.

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Re: Bismarck construction flaws

Postby Dave Saxton » Fri Aug 27, 2010 2:51 pm

Hi Tenmelckram,

So my questions for Dave:

1. DO you regard Bis' FC radar as being equally advanced and thus conferring an advantage equal to her SC radar?



The GEMA Seetakt was a multirole radar and rather biased toward the firecontrol role in is function. As Thorsten pointed out the German radar was intergrated into the centralized firecontrol system.

2. Did the US ships when they were launched by May 1941 already have the FC capability in c. above?



No. In 1941 USN battleships at best only had CXAM airwarning radar. CXAM evolved into the SK with a large antenna or SC with small antenna. It was a good airwarning radar, but not a good sea surveilence radar and not a firecontrol radar. In 1942 USN battleships began to receive the 40cm Mk3 and MK4 firecontrol sets, as well as the exceptional 10cm SG sea surveilence radar. One of the interesting aspects of the night battle in which Washington and South Dakota engaged near Savo Is., was that the Washington's SG was the star of the battle and not the Mk3 and Mk4 firecontrol sets. In some ways the 40cm sets were inferior to contemporary British and German decimetric radars.

3. Did c. actually provide a practical and substantial FC advantage?



There's no question that radar ranging, particularly if intergated to the FC system, is a significant firecontrol advantage. The accuracy available with radar range finding is an order of magnatude better than with optical range finding alone. The large optical stereoscopic range finders up top on the US battleships could provide a range accuracy that was IRCC Approx 1% of the range. The range accuracy of USN radar was about ten times more accurate than their optical range finders +/- 40 yards with Mk3, and +/-15 yards with centimetric sets. The German 80cm sets eventually attained range accuracies of +/- 25 meters regardless of the range. Also the ability to use radar to correct the fall shot provides a significant advantage. The difference isn't as stark between the accuracy of radar bearing and optical bearing measurements. It was common practice to combine optical bearing with radar ranging by just about everybody, unless the target could not be seen, of course. In that case it was necessary to use all radar targeting.

4. Was c. as I believe "unique", or at least, the only one that actually worked?


The German and also the British radar directed firecontrol also worked, and worked well. The Hipper had to rely on radar directed firecontrol at the Battle of Barents Sea, and its shooting accuracy was exceptional, scoring first salvo straddles and hits vs destroyers in several cases.
Entering a night sea battle is an awesome business.The enveloping darkness, hiding the enemy's.. seems a living thing, malignant and oppressive.Swishing water at the bow and stern mark an inexorable advance toward an unknown destiny.

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Re: Bismarck construction flaws

Postby RF » Fri Aug 27, 2010 6:12 pm

tnemelckram wrote:
Bismark lost n' found is also the thing that gives the story its drama. So it's only natural that the focus would be on her sea search radar capability.


I'm not that clear that sea search radar is that important to the Bismarck, as both German ships picked up the noise of the screws of Hood and POW on their sonar listening devices several hours before they came into visual range.....
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Re: Bismarck construction flaws

Postby lwd » Mon Aug 30, 2010 6:08 pm

I don't think I've read of any other countries putting this sensative of sonar on their capital ships. I can see how it might not work well in certain areas but the passive nature of the German system certainly has a lot to recomend it.

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Re: Bismarck construction flaws

Postby Bgile » Tue Aug 31, 2010 7:29 pm

lwd wrote:I don't think I've read of any other countries putting this sensative of sonar on their capital ships. I can see how it might not work well in certain areas but the passive nature of the German system certainly has a lot to recomend it.


We don't do it today. It isn't normally done because large ships are inherently very noisy. Sonar, especially passive sonar, doesn't usually work very well on them. I suspect the performance of Bismarck's array at DS was the result of unusual propagation conditions, coupled with the object being detected being very large and noisy itself. Keep in mind that this sonar is also the device which picked up non existent torpedoes a while later.

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Re: Bismarck construction flaws

Postby lwd » Tue Aug 31, 2010 8:27 pm

I thought that was the one(s) on Eugen. In any case any new complex sensor will have a significant learning curve before people become good at using it. Certainly there are considerable parallels with radar.

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Re: Bismarck construction flaws

Postby Bgile » Wed Sep 01, 2010 11:25 pm

lwd wrote:I thought that was the one(s) on Eugen. In any case any new complex sensor will have a significant learning curve before people become good at using it. Certainly there are considerable parallels with radar.


Yes, it was the one on PE. As far as I know, that one was the same as the one on Bismarck. In any case, I have some experience with the USN BQR series sonars up through 1976 on US submarines. These sonar arrays were developed as a result of experimentation with the array from PE, and of course then received several generations of enhancements through the years. It was very dependent, as all of our sonars were, on own ship noise levels. The slower and quieter the better. As you increase speed you have both increased machinery noise and increased flow noise over the transducers, and both reduce your ability to listen effectively. I can assure you that in 1976 US submarines were substantially quieter than Bismarck in 1941.

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Re: Bismarck construction flaws

Postby dale3242 » Fri Oct 01, 2010 1:32 pm

I have some observations concerning the construction/design flaws of the Bismarck that contributed to her demise. The torpedo that hit the Bismarck's stern initially jammed both rudders. However, one rudder was successfully unjammed. The ship could then be steered successfully by use of the engines and one rudder. However, the drag caused by the jammed rudder and the requirement to run one side screw in reverse so slowed the ship that the waves crashing on the stern from the heavy seas from the north would have successively flooded the stern through the damaged bulkheads. Had the Bismarck had a stronger stern, meaning stronger internal watertight bulkheads in the stern, the ship could have continued on a southerly course to safety.

In the previous discussion concerning AA guns, I did not notice any comments concerning the fuse setters. A problem that I have read about concerned the 4.1 inch AA guns fuse setting predictors (The mechanical analog computers for setting the time to explode the AA shells after they are fired.). The Germans had designed these based on modern aircraft with fast attack speeds. They didn't have the capability to properly set the fuse for an attacking plane that was flying as slow as a Swordfish! As such the fire from the 4.1 inch guns was almost useless. Finally, the US navy is probably the only navy that took seriously the threat of air attack prior to WWII. Even so, by the end of WWII the US navy was moving away from the massed batteries of 40 mm to 3 inch AA guns. The Bismarck might have been better served with more numerous, but smaller caliber AA, perhaps 24 or 30 3.5 inch (88 mm).

An finally, I don't think anyone has brought up a human failing of the Germans. On the Bismarck, the crew were kept at their action stations for most of the cruise with little or no rest. As was typical for the Germans, they gave their crews stimulants including amphetamines. Never the less, I have read that some of the men were so tired that in the final battle they fell asleep at their posts.

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Re: Bismarck construction flaws

Postby Bgile » Fri Oct 01, 2010 7:28 pm

dale3242 wrote:I have some observations concerning the construction/design flaws of the Bismarck that contributed to her demise. The torpedo that hit the Bismarck's stern initially jammed both rudders. However, one rudder was successfully unjammed. The ship could then be steered successfully by use of the engines and one rudder. However, the drag caused by the jammed rudder and the requirement to run one side screw in reverse so slowed the ship that the waves crashing on the stern from the heavy seas from the north would have successively flooded the stern through the damaged bulkheads. Had the Bismarck had a stronger stern, meaning stronger internal watertight bulkheads in the stern, the ship could have continued on a southerly course to safety.

In the previous discussion concerning AA guns, I did not notice any comments concerning the fuse setters. A problem that I have read about concerned the 4.1 inch AA guns fuse setting predictors (The mechanical analog computers for setting the time to explode the AA shells after they are fired.). The Germans had designed these based on modern aircraft with fast attack speeds. They didn't have the capability to properly set the fuse for an attacking plane that was flying as slow as a Swordfish! As such the fire from the 4.1 inch guns was almost useless. Finally, the US navy is probably the only navy that took seriously the threat of air attack prior to WWII. Even so, by the end of WWII the US navy was moving away from the massed batteries of 40 mm to 3 inch AA guns. The Bismarck might have been better served with more numerous, but smaller caliber AA, perhaps 24 or 30 3.5 inch (88 mm).

An finally, I don't think anyone has brought up a human failing of the Germans. On the Bismarck, the crew were kept at their action stations for most of the cruise with little or no rest. As was typical for the Germans, they gave their crews stimulants including amphetamines. Never the less, I have read that some of the men were so tired that in the final battle they fell asleep at their posts.


Where did you read about the fuse setters? As far as I know, it's a myth perpetrated by people trying to explain Bismarck's very poor AA results. Bismarck had very little AA practice prior to that cruise, and her crew were aware of a number of deficiencies in that regard. Large numbers of 37mm and 20mm would have served her better than 88mm against Swordfish. The deck footprint of 88mm wouldn't be much smaller than the 105mm she had.

The US switched to 3"/50 AA guns post war so they could use VT fuses. The 40mm projectiles were too small for the VT fuses of the day. That obviously is not relevant to 1941, and 40mm were the most effective AA weapon in the US arsenal for the duration of WWII.

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Re: Bismarck construction flaws

Postby dunmunro » Fri Oct 01, 2010 8:29 pm

dale3242 wrote:

In the previous discussion concerning AA guns, I did not notice any comments concerning the fuse setters. A problem that I have read about concerned the 4.1 inch AA guns fuse setting predictors (The mechanical analog computers for setting the time to explode the AA shells after they are fired.). The Germans had designed these based on modern aircraft with fast attack speeds. They didn't have the capability to properly set the fuse for an attacking plane that was flying as slow as a Swordfish! As such the fire from the 4.1 inch guns was almost useless. Finally, the US navy is probably the only navy that took seriously the threat of air attack prior to WWII. Even so, by the end of WWII the US navy was moving away from the massed batteries of 40 mm to 3 inch AA guns. The Bismarck might have been better served with more numerous, but smaller caliber AA, perhaps 24 or 30 3.5 inch (88 mm).


I am pretty certain the Bismarck's AA FC system could accommodate the speeds to be expected from Swordfish attacks, since the Luftwaffe had been/was using TBs and float planes with similar performance. The Swordfish actually had a higher attack speed than the USN Devastator monoplane. The real problem was likely related to the fact that hitting aircraft with mechanical time fuzed (MT) shells is very difficult due to a combination of MT fuze, range, target direction and target speed errors and the fact that the KM AA FC system on Bismarck used a Gyro stabilization technique that was notoriously bad.

You simply have to compare the AA armament of modern RN ships versus any other navy to know which navy took the threat of air attack most seriously prior to WW2. Compare HMS Renown in 1939 to any other capital ship, and you will find that the RN was ahead in terms of AA armament.

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Re: Bismarck construction flaws

Postby Serg » Fri Oct 01, 2010 8:48 pm

dunmunro wrote:and the fact that the KM AA FC system on Bismarck used a Gyro stabilization technique that was notoriously bad.

Do you know another AA FC which will be better at such weather conditions?

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Re: Bismarck construction flaws

Postby tommy303 » Fri Oct 01, 2010 8:53 pm

The deck footprint for the 8,8cm would have been identical to the 10,5cm, as the latter used the 8,8cm's Dop L/C31 mounting. Half of Bismarck's 10,5cm mountings were the Dop L/C31 and half were the improved, but nearly identical sized Dop L/C37. Thus there would have been no difference in deck space taken up by 8,8cm and 10,5cm armament.

The older mountings were carried forward and the newer ones aft, but the differences in elevating, train and cross level speeds were considerable between the two mountings, and resulted in the older mounts not being adequately integrated into the fire control system. This, together with the absence of the after tri-axial heavy flak directors, and the almost complete lack of target practice on the part of the Flak crews were the major contributing factor to the Bismarck's lack of AA success. A year later, Tirpitz with the same fire control system, but well trained crews and fully integrated gun mountings, did fairly well against equally slow Albacore torpedo bombers.

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