Tirpitz vs South Dakota according to German sources

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Tirpitz vs South Dakota according to German sources

Post by alecsandros » Tue May 27, 2014 8:29 am

HEllo,
I was thinking about the way the Kriegsmarine was expecting to deal with enemy battleships.

Are there any sources mentioning expected hit ratios of various world battleshps vs Tirptiz/Bismarck and vice-versa ?

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Re: Tirpitz vs South Dakota according to German sources

Post by Thorsten Wahl » Sat May 31, 2014 4:39 pm

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Re: Tirpitz vs South Dakota according to German sources

Post by Steve Crandell » Sat May 31, 2014 8:31 pm

For those of us who can't read German, where there any findings of great significance?

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Re: Tirpitz vs South Dakota according to German sources

Post by Iranon » Sun Jun 01, 2014 7:18 pm

Against Nelson: Main combat range of 12-16km, stay at an angle around 30°. Effective fire still possible, especially hits on turrets and barbettes, at 16-24km. At distances longer than 23km, own deck may become vulnerable without a corresponding weakness of the enemy.
Use AP for decisive hits. For HE to be an option, see general guidelines. Nelson has an unprotected bow, much of the upper ship and superstructure is unprotected.

Against Royal Sovereign (meaning: R Class): Main combat range 12-18km, keep at an angle around 20°. Own barbetters endangered, otherwise considerable superiority over the opponent. Rough parity outside these distances.
Use AP for decisive hits. Fore HE see guidelines, less attractive than against Nelson since the upper ship is better protected.

Against Dunkerque: Main battle distance 13-18km, comfortable superiority at this range. Own barbettes and turret faceplates endangered. Decisive hits against opponent's turrets and barbettes expected to be possible out to 27km. Own armour deck can be penetrated over 26km.
13-18km is recommended because of possible decapping by a layered armour scheme.
Use AP to destroy. See guidelines for HE use, note that Dunkerque has an unprotected bow, upper ship and superstructure.

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Re: Tirpitz vs South Dakota according to German sources

Post by Steve Crandell » Sun Jun 01, 2014 10:48 pm

Thank you! That's interesting, but nothing about South Dakota.

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Re: Tirpitz vs South Dakota according to German sources

Post by alecsandros » Mon Jun 02, 2014 9:26 am

Steve Crandell wrote:Thank you! That's interesting, but nothing about South Dakota.
Indeed...

What's interesting also is that the GErmans expected NElson to be firing at 840m/s...

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Re: Tirpitz vs South Dakota according to German sources

Post by Steve Crandell » Mon Jun 02, 2014 5:12 pm

alecsandros wrote:
Steve Crandell wrote:Thank you! That's interesting, but nothing about South Dakota.
Indeed...

What's interesting also is that the GErmans expected NElson to be firing at 840m/s...
Yes, and that they were concerned about deck penetration. The Germans didn't seem to be quite so sanguine about that as Dave is.

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Re: Tirpitz vs South Dakota according to German sources

Post by Dave Saxton » Mon Jun 02, 2014 6:11 pm

Steve Crandell wrote:
Yes, and that they were concerned about deck penetration. The Germans didn't seem to be quite so sanguine about that as Dave is.

The requirement, as documented, was for the IZ to extend to 30,000 meters (32,800 yards) vs 15" fire, and it certainly did meet that requirement. Such guidelines tend be very conservative giving the user a wide margin for error, nonetheless.
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Re: Tirpitz vs South Dakota according to German sources

Post by tommy303 » Tue Jun 03, 2014 12:01 am

What's interesting also is that the GErmans expected NElson to be firing at 840m/s...
That is not so far off from the original 823m/s loading originally planned for the guns, but which was found to cause too much barrel wear and poor accuracy.

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Re: Tirpitz vs South Dakota according to German sources

Post by José M. Rico » Tue Jun 03, 2014 12:52 am

tommy303 wrote:
What's interesting also is that the GErmans expected NElson to be firing at 840m/s...
That is not so far off from the original 823m/s loading originally planned for the guns, but which was found to cause too much barrel wear and poor accuracy.
The 840mps figure was probably increased on purpose as a safety margin.
The actual muzzle velocity for these guns was below 800 mps.

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Re: Tirpitz vs South Dakota according to German sources

Post by Steve Crandell » Tue Jun 03, 2014 2:26 am

Dave Saxton wrote:
Steve Crandell wrote:
Yes, and that they were concerned about deck penetration. The Germans didn't seem to be quite so sanguine about that as Dave is.

The requirement, as documented, was for the IZ to extend to 30,000 meters (32,800 yards) vs 15" fire, and it certainly did meet that requirement. Such guidelines tend be very conservative giving the user a wide margin for error, nonetheless.
"Against Nelson: ... At distances longer than 23km, own deck may become vulnerable without a corresponding weakness of the enemy."

And that was at the very high muzzle velocity they were erroneously assuming for the British 16".

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Re: Tirpitz vs South Dakota according to German sources

Post by Thorsten Wahl » Tue Jun 03, 2014 6:26 am

just a comment
the written explanations on the protection of german regarding vertical and horizontal from the Textbook "Unterlagen zur Bestimmung der Hauptkampfentfernung und Geschoßwahl Heft a" should be considered additionally. The calculations were some kind of worst case scenario, but one has to expect some additional protection by the special arrangement of the armor.
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Re: Tirpitz vs South Dakota according to German sources

Post by alecsandros » Tue Jun 03, 2014 8:00 am

Thorsten Wahl wrote:just a comment
the written explanations on the protection of german regarding vertical and horizontal from the Textbook "Unterlagen zur Bestimmung der Hauptkampfentfernung und Geschoßwahl Heft a" should be considered additionally. The calculations were some kind of worst case scenario, but one has to expect some additional protection by the special arrangement of the armor.
... agreed, but some caution should also be taken in terms of shell parameters: Nelson's 930kg shells were the lightest 16" shells used by any navy during WW2, and fired at a pretty high velocity (790m/s Nelson, 780m/s Nagato, 703m/s North Carolina/South Dakota, 785m/s Iowa). Thus penetration of horizontal armor was probably less than other guns.

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Re: Tirpitz vs South Dakota according to German sources

Post by Dave Saxton » Tue Jun 03, 2014 2:20 pm

The Germans were greatly over estimating the deck penetration of the enemy guns. Obviously this is a kind of worst case scenario, as Thorsten points out, not knowing the actual performance of enemy guns and shells.

Post war firing range testing, as the British were exploring options for new designs, revealed that none of their 14", 15" and 16" could penetrate up to 6-inches effective deck at ranges of less than 32,000 yards. So the Nelson class deck penetration was about 150 mm at about 30 km. Less for the 14" and 15" guns.

The Germans did know the actual performance of their own guns. For their 38 cm it was 128 mm at 30 km. Hence the Bismarck class was required to have 130 mm minimum deck protection to meet the IZ specifications. Thus Bismarck indeed had 130 mm turret tops and 130 mm effective over the machinery. Over the magazines it was a bit more at 150 mm effective- same as KGV which had 5-inches over the machinery and 6-inches over the magazines. For KGV it was 124 mm turret tops plates.

The American shells probably performed better than the British shells against decks because of their rounder head shape. The head shape is much more important than the weight for deck penetration (see Hoyer). How much better? We can find out from the South Dakota class IZ requirements.

The South Dakota and Iowa class were required to resist the 2240 lb 16" shell out to 31,000 yards. The deck penetration performance at that range is about 5.5-inches. Thus these ships have about 140 mm effective deck, or about the same as KGV and Bismarck classes. The 16"/50 firing the super heavy projectile has about the same deck penetration as the 16"/45 firing the lighter projectile. Therefore, the American 16" shells out performs the Nelson class 16", but not by a whole lot. The 16"/45 firing the super heavy would get more than 5-inches deck penetration at a lesser range of course.
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Re: Tirpitz vs South Dakota according to German sources

Post by alecsandros » Tue Jun 03, 2014 3:33 pm

... I would add that the only battleship designed to resist 16"/L45 and 16"/L45 gunfire was the Montana class.

Immunity zone was 18 - 31.000yards. Deck protection was a layered system of 38mm upper deck on 19mm STS, and a MAD of 155mm on 32mm STS, with a third, 16mm STS splinter deck. Total thickness of the armor of the decks was an unprecedented (and unmatched since) 252mm. Effective thickness using square root formula gives around 165mm, and that not considering yaw, and decapping effects of the upper 57mm deck (from 2 separate pieces though..)

So we can consider 165mm as the minimum thickness to ensure protection against 16"/L45 at 31.000yards (28km).

USN immunity zones were calculated agaisnt complete, intact penetrations, with the shell in a fit condition to burst, IIRC.

Thus Tirpitz 150mm magazines armor was probably safe out to, maybe 25-26km, while the machinery was safe down to 22-23km or so. However, partial penetrations could still cause haevy damage, and I would estimate that those could occur at ranges 5-10% smaller.

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