Tirpitz vs South Dakota according to German sources

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Dave Saxton
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Re: Tirpitz vs South Dakota according to German sources

Post by Dave Saxton » Tue Jun 03, 2014 6:23 pm

alecsandros wrote:... 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.
An online source has the 16"/45 2700 lb shell exceeding 130 mm by about 24.6 km (27,00 yards), and exceeding 150 mm by 26.5 km (29,000 yards). One of the main reasons the American and German shells performed well at oblique striking angles is because of the blunt head shapes. Indeed the reason the 1944 shell performs better is because of more blunt shape than the 39-44 shell. Which brings this into play:
Thorsten Wahl wrote:...but one has to expect some additional protection by the special arrangement of the armor.
Because of yaw, that more ideal factor of the blunt shell head digging into homogenous armour goes out the window, and the performance enhancement of the blunt head shape is not as significant.

With quality homogenous armour, partial penetrations don't really happen; it either fully penetrates or no penetration occurs.
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Re: Tirpitz vs South Dakota according to German sources

Post by alecsandros » Tue Jun 03, 2014 6:49 pm

Dave Saxton wrote:

..but one has to expect some additional protection by the special arrangement of the armor.
"some" maybe.
this is also the case for Montana class armor - upper deck + main deck, with about 4 meters in between them. Not as much as in Tirpitz, but a respectable distance nonetheless...

Also, the behavior of 16" shell attacking 50mm (2") of deck greatly favors the attacking shell.
Because of yaw, that more ideal factor of the blunt shell head digging into homogenous armour goes out the window, and the performance enhancement of the blunt head shape is not as significant.
agreed but
With quality homogenous armour, partial penetrations don't really happen; it either fully penetrates or no penetration occurs.
... as Musashi's case may point out, a heavy explosive impact on the MAD can blow pieces/explosives into the spaces below. In Tirpitz case, the "space below" the MAD was the main cartridge magazine for 38cm shells...

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Re: Tirpitz vs South Dakota according to German sources

Post by paul.mercer » Tue Jun 03, 2014 9:04 pm

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.[/quote]
Gentlemen,
Once again I have to ask for your help.
Am I correct in assuming that 45 or 50/16" means 45" or 50" x 16" is the length of the barrel? if so would the extra 5 x 16" make much difference in either range or penetration whether or not a standard or super heavy shell was used?
Also, why would a battleship use anything other than armour piercing against anothe battleship?
Thanks again for your answers.

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Re: Tirpitz vs South Dakota according to German sources

Post by Dave Saxton » Tue Jun 03, 2014 11:18 pm

Paul,

The other number is essentially the length of the barrel in calibers. So a 16"/45 has a barrel 45 calibers long and a 16"/50 has a barrel 50 calibers long. The 16"/50 is more powerful even if they use the same shell and the same propellant charge because it will have a higher muzzle velocity. The reason it has a higher muzzle velocity is because it is accelerated for longer period of time inside the barrel. A longer barrel also usually has longer riflings length so the shell gets twisted more and usually attains a greater rotation rate before leaving the barrel. A longer barrel also weighs more, requiring a larger mounting and more robust supporting systems.

There are a several methods of measuring barrel length. Usually it is the overall length of the barrel from the muzzle to the breach. The German guns had a different breach design from most others, though. They used a sliding wedge as the breach instead of an plug with interrupted screws. So the Bismarck's 15" was a 15"/52 overall, but from muzzle to breach it measured 48.5 calibers. However, calling it a 15"/48.5 would also be in error because the rifling length or the distance from muzzle to where the shell was seated was about the same distance in calibers as an American 16"/50 but a slightly shorter combustion chamber.

The Germans also used a metal case or cartridge for their propellant charge instead of silk powder bags within the combustion chamber, so required combustion chamber length is not comparable. (although there was a small bagged "forecharge" to take up the slight variable space between the shell and the cased main charge) Once the charges were loaded, the breach wedge was slid back to close the breach. The breach was sealed when the gun fired by the momentary expansion of the metal "cartridge."

Bagged charged are usually employed with breaches that are of the interrupted screw types and length from muzzle to breach is straight forward.
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Re: Tirpitz vs South Dakota according to German sources

Post by Steve Crandell » Wed Jun 04, 2014 7:09 am

The US 16"/45 used a 535 lb SPD powder charge and the 16"/50 used a 660 lb SPD powder charge.

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Re: Tirpitz vs South Dakota according to German sources

Post by Steve Crandell » Wed Jun 04, 2014 7:15 am

Dave Saxton wrote:With quality homogenous armour, partial penetrations don't really happen; it either fully penetrates or no penetration occurs.
That is interesting. You seem to be implying that a given thickness of homogeneous armor is as effective as a thicker face hardened plate, since the former eliminates partial penetration. That doesn't make sense to me.

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Re: Tirpitz vs South Dakota according to German sources

Post by Dave Saxton » Wed Jun 04, 2014 2:52 pm

Homogenous armour is more effective at oblique striking angles according to the curves and also to USN text books. At striking angles at or near the normal face hardened armour is better, even with the potential plug ejection and plate debris problems, however. Another factor is that face hardened plates can be manafactured of acceptable quality up to 12-13-inches thick. Not so with homogenous plates.
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Re: Tirpitz vs South Dakota according to German sources

Post by Steve Crandell » Wed Jun 04, 2014 5:21 pm

Dave Saxton wrote:Homogenous armour is more effective at oblique striking angles according to the curves and also to USN text books. At striking angles at or near the normal face hardened armour is better, even with the potential plug ejection and plate debris problems, however. Another factor is that face hardened plates can be manafactured of acceptable quality up to 12-13-inches thick. Not so with homogenous plates.
I suppose it is not coincidental that the maximum thickness of face hardened armor the Germans used was 14", where as other countries apparently chose to use unacceptable armor in their battleships.

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Re: Tirpitz vs South Dakota according to German sources

Post by alecsandros » Wed Jun 04, 2014 5:49 pm

Steve Crandell wrote:
Dave Saxton wrote:Homogenous armour is more effective at oblique striking angles according to the curves and also to USN text books. At striking angles at or near the normal face hardened armour is better, even with the potential plug ejection and plate debris problems, however. Another factor is that face hardened plates can be manafactured of acceptable quality up to 12-13-inches thick. Not so with homogenous plates.
I suppose it is not coincidental that the maximum thickness of face hardened armor the Germans used was 14", where as other countries apparently chose to use unacceptable armor in their battleships.
... IIRC the problem with thick KC plates resided in the different speed at which the hardened layers were chilling in comparison with the rest of the plate.
Each manufacturing nation tried various methods of production. German Krupp KC armor was expected to mantain 100% resistive quality out to 320mm thickness (12.7"), with anything thicker being less and less resistant than a theoretical "perfect" plate (one that would retain perfect resistive quality at any thickness of the plate). American manufacturers discovered the same effect occured at class A plates of more than 12" (305mm) thickness.
Interestingly enough, those were the actual armor plate thicknesses employed in the battleships built for WW2 (Bismarck, North carolina, South Dakota and Iowa classes)

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Re: Tirpitz vs South Dakota according to German sources

Post by Steve Crandell » Wed Jun 04, 2014 7:29 pm

Yes, but there is a difference between less than perfect and unacceptable. The US would have used 16.1" belt and 18" turret armor on the Montana class, the latter over 4.5" STS. I don't think they would have done that unless they expected the increased thickness to result in increased protection worth the increased weight. The Iowa class also had very thick homogeneous face plates, which were chosen because they were more effective than the same face hardened plate.

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Re: Tirpitz vs South Dakota according to German sources

Post by alecsandros » Thu Jun 05, 2014 10:53 am

Steve Crandell wrote:Yes, but there is a difference between less than perfect and unacceptable. The US would have used 16.1" belt and 18" turret armor on the Montana class, the latter over 4.5" STS. I don't think they would have done that unless they expected the increased thickness to result in increased protection worth the increased weight. The Iowa class also had very thick homogeneous face plates, which were chosen because they were more effective than the same face hardened plate.
... The thickness helped, but not as much as a "perfect" plate. For instance, Krupp 400mm plate would have been as resistant as 375mm perfect plate. 375mm Krupp plate would have been strong as a 355mm plate, and so on.

Also, war-time developments of US armor contruction may have increased the 305mm thickness.

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Re: Tirpitz vs South Dakota according to German sources

Post by lightyear » Sun Feb 24, 2019 10:22 am

Steve Crandell wrote:
Wed Jun 04, 2014 7:29 pm
Yes, but there is a difference between less than perfect and unacceptable. The US would have used 16.1" belt and 18" turret armor on the Montana class, the latter over 4.5" STS. I don't think they would have done that unless they expected the increased thickness to result in increased protection worth the increased weight. The Iowa class also had very thick homogeneous face plates, which were chosen because they were more effective than the same face hardened plate.
I also find that the class B facelet of iowa is more resistant than class A in Naab program. shell goes less in class b than class a even kc at 24 degree from vrtical. but how can it possible? 24 degree from vertical is far from high oblicity. i.e. c34 is at 16.4 degree at 20000 meter. the turret face is 40.5 backwards. so the compund angel is 40.5-16.4=24.1 degree. how can homo perform much better than FH at this angel? i don't understand.
also, do you mean the 460 class b face is better than 460 class a?
thank you

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