Bismarck vs USS Iowa coass

[Carl Schwamberger]

My understanding is in 1942 the USN doctrine was still to look for results in the midrange gunfight & not expect anything decisive at long range. This is going to affect tactics in such a encounter.

[Thoddy]

The 1,764-pound shell could penetrate 16.5 inches of armor at 11 miles

To be exact; based on the fireeffectables of Bismarck and Tirpitz (Unterlagen zur Bestimmung der Hauptkampfentfernung und Geschosswahl, Heft h Eigene Durchschlagsangaben für Schlachtschiffe Bismarck und Tirpitz), the armor piercing shell would be able to penetrate at 11 (sea)miles (= 18,1 km) a single vertical FH-armor plate of about 17.4 inches thickness.

It’s 1942...Iowa has ...Mk 13 fire control radar

The Mk 13 firecontrol radar came into service in late 1945.

Iowa has one technological innovation, the German battlewagon doesn’t: radar-directed main guns

According to primary documentation available at the Bundesarchiv/Militärarchiv Freiburg (for instance file Artilleriewaffenfragen ab 1939; several files regarding "Rheinübung" ) about german radar (Funkmess = Dete= EM2 = NVK Gerät).
out of the three radarsets on board Bismarck two were dedicated firecontrol sets,
-general range of these sets ~30 km against ground targets ; against prominent landmarks range up to 70 km
They had so called fine range (Entfernung fein) and fine bearing(Seite fein) equipment); modular extensions, wich improved the capabilities of the standard tactical sets.
-bearing fine accuracy about 3/16 degrees
-range fine accuracy at any range about 50 m.
Range and bearing data were fed into the firing computer, parallel to data from optical equipment.
Bismarck and Prinz Eugen were the first ships equiped with this set. Based on the EM2 protocol of Prinz Eugen this set was also able to spot shell splashes.
Germany used radar directed(range and bearing) artillery fire since winter 1940, especially the coast defense battery "Großer Kurfürst".

Admiral Scheer and Admiral Graf Spee conducted a comparative night firing excercise in summer 1939, with Admiral Graf Spee using radar (only for range) with the result that the use of radar by "Admiral Graf Spee" outperformed the pure optical equipment on board of "Admiral Scheer".
By 1941 the radar sets on board Bismarck were "state of the art".

Nevertheless they werent comparable with the performance of the "cm"- sets and the ppi presentation used on board of american ships since about 1943.

[Carl Schwamberger]

Not to induce thread drift, or a outright hijacking; I've found it much more interesting to consider a USN patrol of a couple BB, cruisers, fleet destroyers, and a carrier coming in intercept range of a undamaged Bismarck & Prince Eugeon doing a anti convoy raid in the mid Atlantic.

[Don71]

Please can you name one single USS BB in Mai 1941, which was war ready and could possible intercept Bismarck and Prinz Eugen?
Weather North Carolina nor Washington were to this time near war ready and I would like to see how it is possible to intercept a fast BB, which could achieve 30kn with 21kn BBs.

[Takao]

Please can you name one single USS BB in Mai 1941, which was war ready and could possible intercept Bismarck and Prinz Eugen?
Weather North Carolina nor Washington were to this time near war ready and I would like to see how it is possible to intercept a fast BB, which could achieve 30kn with 21kn BBs.

North Carolina commissioned in early April '41 & Washington commissioned in mid-Late '41. They were not ready for combat.

Texas was in the area just before Bismarck sailed and was heading home. New York was in the area after the action had moved on, but is reported to have almost stumbled across Prinz Eugen, but I don't think it was that close. The only way they would have caught Bismarck is by coming across her in poor visibility, and the German could have easily out distanced them, given that the 21-knot battleships could only do 18-19 knots after their modernizations.

[T. A. Gardner]

Speed here is only useful for running away. If that were Bismarck's Captain's intent then it becomes a tactical mission fail because the opposing battleships drove him off. While they didn't sink or damage his ship, he couldn't complete the mission within the battle space. If on the other hand, he stays and fights, speed really doesn't matter. Bismarck cannot realistically outrange another battleship in a duel. Both can realistically fire with some probability of hitting to about 20,000 yards and both are likely to be about equally accurate.
But, as Bismarck is likely to face 2 or more US battleships--they operate in divisions of 2 or 3 normally--then the Bismarck is at a disadvantage as one or more opposing battleships is unengaged and that means Bismarck is likely to loose the fight.

[Carl Schwamberger]

Two USN Standards closing head on present 12 14" cannon, if the Bismarck turns broad side it presents only 8 cannon. If the lead US BB turns broadside while the other closes its 15 cannon to eight. Adding the Prinz Eugen back into the mix does not seem to balance the equation decisively.

...Texas was in the area just before Bismarck sailed and was heading home. New York was in the area after the action had moved on, but is reported to have almost stumbled across Prinz Eugen, but I don't think it was that close. The only way they would have caught Bismarck is by coming across her in poor visibility, and the German could have easily out distanced them, given that the 21-knot battleships could only do 18-19 knots after their modernizations.

Was the Ranger accompanying the Texas, or New York? My scenario is the German task group stumbles across a convoy at the edge of the Exclusion or Neutrality Zone. US flagged cargo ships are sending radio messages about being under attack. The Admiral of the USN TF looks at his chart & sees the range is under 200 nm, then considers the Ranger & its dive bomber wing...

[Takao]

No, Ranger was operating out of Bermuda, patrolling the central Atlantic at the time.

[Avalancheon]

Does anyone know how the FuMO 23 radar set compared to the Mk 8 radar set? Were they both capable of estimating range and bearing? The FuMO 23 had a wavelength of 82 cm, and a power output of 8 kw. The Mk 8 had a wavelength of 10 cm, and a power output of 15-20 kw. It seems like the American equipment was significantly better than what the Germans were using.

Although with that being said, there is some question about the ability of the Iowa class to score hits at extreme ranges. The U.S. Navy did a firing test in July 1944 to determine the accuracy of the main battery, at a range of 10,000, 20,000, and 30,000 yards. They concluded that at the upper range limit, only about 2.7% to 1.4% of shells fired would hit a target the size of an Iowa class battleship. (Former was for a broadside target, latter was for an end-on target)

[Carl Schwamberger]

Does anyone know how the FuMO 23 radar set compared to the Mk 8 radar set? Were they both capable of estimating range and bearing? The FuMO 23 had a wavelength of 82 cm, and a power output of 8 kw. The Mk 8 had a wavelength of 10 cm, and a power output of 15-20 kw. It seems like the American equipment was significantly better than what the Germans were using.

Although with that being said, there is some question about the ability of the Iowa class to score hits at extreme ranges. The U.S. Navy did a firing test in July 1944 to determine the accuracy of the main battery, at a range of 10,000, 20,000, and 30,000 yards. They concluded that at the upper range limit, only about 2.7% to 1.4% of shells fired would hit a target the size of an Iowa class battleship. (Former was for a broadside target, latter was for an end-on target)

Looked up the article I'd been thinking of when I wrote post #46. From Alan Zimm 'American Calculations of Battle Line Strength 1941-2'

Zimm describes USN BB design & interwar doctrine as influenced by the assumption very long range gunfire had too low a hit probability to base tactical doctrine on. Golden Bullet territory as I would put it. USN doctrine & ship design was focused on the midrange engagement of under 22,000 yards. While the USN did not neglect VLR gunnery interwar, they even increased attention to it in the latter 1930s, there was the doctrine that decisive result were more likely to occur under 22,000 yards. The physics of gunnery as the USN saw were parallel to calculations of the BB 'Immunity Zone' vs Japanese main guns. For the Standards that was pegged at a minimum of 13,000 yards for ten of the Standards & a minimum of 15,000 yards for three others. The upper limit of the Immunity Zone varied between 22,000 yards (six ships) & 26,000yds for three of the Standards. Simm discuss at length how this pertain perceptions of gunnery accuracy & armor immunity zone influenced tactical & strategic doctrines of the USN vs Japan during 1942. At the tactical level this boiled down to the USN battleship commander would seek to rapidly close the range until within the optimal range between 13,000 & 22,000 yards. Zimms discussion is focused on fighting Japan & through 1942. But it suggests the USN BB commander would have 20+ years of this doctrine behind his thinking in a hypothetical battle vs the Bismarck class or any other German warship. That is try to shape the battle to occur inside the this sweet zone, or not a VLR ranges of +22,000 yards.

[T. A. Gardner]

Does anyone know how the FuMO 23 radar set compared to the Mk 8 radar set? Were they both capable of estimating range and bearing? The FuMO 23 had a wavelength of 82 cm, and a power output of 8 kw. The Mk 8 had a wavelength of 10 cm, and a power output of 15-20 kw. It seems like the American equipment was significantly better than what the Germans were using.

Although with that being said, there is some question about the ability of the Iowa class to score hits at extreme ranges. The U.S. Navy did a firing test in July 1944 to determine the accuracy of the main battery, at a range of 10,000, 20,000, and 30,000 yards. They concluded that at the upper range limit, only about 2.7% to 1.4% of shells fired would hit a target the size of an Iowa class battleship. (Former was for a broadside target, latter was for an end-on target)

There's really no comparison. The Seetakt in all versions used an A-scope display. It would look something like this:



The Mk 8 display was far more sophisticated, not just because the radar was more accurate.



http://www.researcheratlarge.com/Ships/Misc/FCR-Mk8/

You could pick out individual shell splashes on a Mk 8, and easily discern with great precision the range and bearing of a target. Seetakt was mostly useful as a supplement to optical range finding rather than a means of accurate input on its own.

[Carl Schwamberger]

Running off my rabbit trail of the USS Ranger & possible Standard BB.. It appears the Bismarck had a uniform deck armor of 110mm thickness.

Wh n/A (Wotan hart, new type). Homogeneous armour steel with a tensile strength of 85-95 kg/mm², a strain of 20% and a yield point of 50-55 kg/mm². This material was used for the armoured decks, and, in the thickness employed aboard the Bismarck, was the equal of most foreign homogeneous plates.

Did the 1000lb bombs of the USN have any ability to penetrate or severely damage this horizontal armor covering? Im assuming here the 500lb bomb could not. Also assuming a 'average' USN dive bombing attack of May 1941.

[Thoddy]

The Mk 8 display was far more sophisticated, not just because the radar was more accurate.

its a end of 1945 model

As I said above the Germans started radar directed firing versus ships at the end of 1940 (Battery Grosser Kurfürst at distances up to 33 km).
the funkmess equipment on Bord Bismarck had a range of 30 km+ it has "Seite fein" and "Entfernung fein" modules.
bearing accuracy 3/16 degrees -using lobe switching on the receiver end
range accuracy ~50 m using Messkette -(calibrated electronic circuit)
splash spotting was possible

It appears the Bismarck had a uniform deck armor of 110mm thickness.

upper deck 50 mm partly increased to 80 mm (around several guns)
armored (third) deck,
-horizontal part 80 mm over machinery, 110 mm over magazines
-slopes 110 mm abreast machinery, 120 mm abreast magazines

the horizontal protection can be considered as a spaced array giving somwhat more protection as the sum of plartes under certain attack conditions.
british ballistic research give equivalent numbers of 6 inches single plate versus british projectiles in service at the end of 1945.
US research on spaced armor W. Hurlich 1950
https://apps.dtic.mil/docs/citations/ADA954865

the vertical protection also gaves more protection as the nominal sum of armor thicknesses.

[T. A. Gardner]

I don't think the armor scheme of any battleship is all that relevant to its continued ability to fight effectively. In every case in WW 2, the loss of fire control, command stations, and things like fires and flooding were far more destructive to any ship in combat than whether the armor protection actually prevented penetrations.
In fact, in most battle situations, the belt system of a battleship remained mostly or totally unpenetrated. Hits on turrets didn't have to penetrate to render the turret unserviceable. There were several occasions where hits jammed a turret in train without penetration. Loss of main machinery could be affected simply by serious damage to the boiler forced draft system and ship's stacks.
A large uncontrolled fire could put the ship in serious danger. The same goes for flooding even if the torpedo defense system was not penetrated.

Look at the historical Bismarck situation sans aircraft attack. PoW had one shell hit forward causing somewhere around 2,000 tons of flooding and leaving Bismarck down by the bow. In her finial fight, loss of main fire control by damage to the directors early in the fight left her almost blind trying to fight back. It didn't matter that the wreck was still afloat at the end of the fight any more than it did with Kirishima versus Washington and S. Dakota. The ship was wrecked and hors de combat. Scharnhorst at North Cape, same thing. Yamashiro at Surigao Straight, is yet another example.

So, quibbling over the exact armor scheme and quality of it is really nearly meaningless. What matters most is who is on target first and gets solid hits. Bismarck in any realistic scenario would be up against more than one battleship and that means Bismarck loses--PERIOD.

[Carl Schwamberger]

My question concerning the penetration of aircraft bombs came from thoughts about mobility reduction. The CV Ranger is not supposed to have torpedoes or torpedo planes in May 1941. So, its all on the 40 odd dive bombers it had to sortie vs the target. A look at the pictures suggests 2/3s of the Bismarcks length, from rudder mount to forward boiler compartment was mobility dedicated. & it looks like all that was under armor.

If notionally 30 dive bombers attack a 10% hit rate or three bombs seems reasonable. So continuing with crude numbers 2/3s or two bombs hit over or adjacent to boiler, engine, propulsion & steering, with 1000lb bombs cause enough damage to reduce speed. If not the Bismarck escapes, otherwise the speed/manuver damage OTL are reproduced & its run down.