Rosselsprung 1942 actual combat

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Steve Crandell
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Re: Rosselsprung 1942 actual combat

Post by Steve Crandell »

alecsandros wrote: it would depend on trajectory. some shells may go through weather deck + flat MAD. other shells through weather deck + slope.
In Bismarck and Tirpitz, the MAD was a turtle shell design.
The slope has little to do with deck protection. It is part of the system including the main armor belt. Shells on a trajectory to hit the MAD are unlikely to encounter the slope without first hitting side armor. No one really questions the near impossibility of penetrating that part to the system.
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Re: Rosselsprung 1942 actual combat

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Dave Saxton wrote:
Okay, scaled up it looks like it is the USS Montana deck protection design vs 16" at about 40,000 meters range. The 1943 date would certainly indicate this as well. The main problem with yaw not being fully effective is the distance between the upper deck and the MAD is too small for procession to become manifest.
Where do you get 40,000m? A new 16"45 will have a 30 deg incidence at about 27,000 yds, and a 16"/50 at about 32,000 yds. That's with a new gun, which so many people keep saying is not likely.

When people want to discredit a weapon's penetration they often consider a worn liner when dealing with belt penetration and a new gun when dealing with deck penetration.
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Re: Rosselsprung 1942 actual combat

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30* from the normal is 60* angle of fall.

Scaled up the middle plate is 7.5" or the effective thickness of the Montana class MAD. A 15" or 16" shell will not have that much deck penetration at 30* angle of fall. It surely must be 30* from the normal and not 60* from the normal, which it would be at 40,000 meters.
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Re: Rosselsprung 1942 actual combat

Post by alecsandros »

Steve Crandell wrote:
alecsandros wrote: it would depend on trajectory. some shells may go through weather deck + flat MAD. other shells through weather deck + slope.
In Bismarck and Tirpitz, the MAD was a turtle shell design.
The slope has little to do with deck protection. It is part of the system including the main armor belt. Shells on a trajectory to hit the MAD are unlikely to encounter the slope without first hitting side armor. No one really questions the near impossibility of penetrating that part to the system.
... I am not so sure about it's invulnerability at close ranges, but that's anoter matter.

A shell coming from the forward part of the ship, or from the aft part, could perforate the weather deck and then go towards the slope (or towards the flat MAD - it would depend on the exact point and angle of entry).

The flat portion of the MAD was indeed somewhat thin by WW2 standards, especialy above machinery...
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Re: Rosselsprung 1942 actual combat

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Dave Saxton wrote:30* from the normal is 60* angle of fall.

Scaled up the middle plate is 7.5" or the effective thickness of the Montana class MAD. A 15" or 16" shell will not have that much deck penetration at 30* angle of fall. It surely must be 30* from the normal and not 60* from the normal, which it would be at 40,000 meters.
Ah, the meaning of "obliquity". I can't imagine why anyone would want to test a shell hitting a deck at 30 degrees from normal, since that's a rather unlikely angle. Was obliquity Thorsten's term, or that used in the report? If it means 30 deg from the normal, the test is meaningless.
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Re: Rosselsprung 1942 actual combat

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Indeed, it is meaningless as to determining much about the effectiveness of Tirpitz's deck protection. But that is not what they were testing for. They were testing the effectiveness of flat nosed projectiles vs more conventional projectiles. The obliquity of 30* does mean they were testing 30* from the normal. They also tested at 0* obliquity and indeed 60* from the normal. That 0* obliquity = the Normal and 30* is 30* from the normal, and 60* is 60* from the normal is proven by the limit velocities and energy consumed data presented. It also reccomends that flat nosed AP bombs should be considered because bombs would strike at the same obliquities vs decks as in this test, considering since it was by scale an array similar to used on new USN BBs of the time.


One thing I found interesting was that no yaw was measured. They used yaw cards and no precession was manifest within the short distances between plates. This is as expected because procession is a slow proccess requiring considerable distance. This would confirm Krupp observations about necessary spacing distances within spaced arrays.

This is very interesting and thank you Thorsten for posting the link.

On edit: yaw cards were placed in front of the plates in each case. Most of the tests were vs single plates and not against spaced arrays. This indicated that no yaw was present before striking the plates. They also noted that flat noses were ineffective if the armour thickness exceeded 50% of the projectile diameter but were very effective at less than 50%.

Another interesting factor was that the reason ascribed for the effectiveness of flat nosed projectiles was the lesser amount of armour material worked vs pointed projectiles. If yaw is present then more area is impacted which would prove that yaw effectively increases necessary velocity.

It also noted that through penetration of a plate the same energy is consumed for heavier projectiles as it is for lighter projectiles.
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Re: Rosselsprung 1942 actual combat

Post by Thorsten Wahl »

I used american terminology with obliquity 0 degree = perpendicular to plate.
So the 30 degrees obliquity is an normally impossible attack angle for deck protection. The reason I choose to mention this test, was that spaced arrays has to be adjusted to the general type of attack and projectile(s) for beeing effective. Inadeqately adapted spaced arrangements may decrease protection under certain circumstances.
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Re: Rosselsprung 1942 actual combat

Post by Dave Saxton »

Thorsten Wahl wrote: Inadeqately adapted spaced arrangements may decrease protection under certain circumstances.
Indeed, in my opinion the unit with questionable deck protection in this scenario is not the Tirpitz but the Washington.
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Re: Rosselsprung 1942 actual combat

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Dave Saxton wrote:
Thorsten Wahl wrote: Inadeqately adapted spaced arrangements may decrease protection under certain circumstances.
Indeed, in my opinion the unit with questionable deck protection in this scenario is not the Tirpitz but the Washington.
Why ? I don't see danger for Washington's decks from the 38cm gun at 30km or less.
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Re: Rosselsprung 1942 actual combat

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alecsandros wrote:
Dave Saxton wrote: Indeed, in my opinion the unit with questionable deck protection in this scenario is not the Tirpitz but the Washington.
Why ? I don't see danger for Washington's decks from the 38cm gun at 30km or less.
I do. By the American IZ calculations and also using Krupp's calculas the deck protection is 105mm for Washington. Before I was giving a bit more based on the yaw deck (aka bomb deck), but given Thorsten's finding 105mm is probably correct.

At 28,000 yards the 38cm is penetrating 114mm Wh. I also think that STS was slightly inferior to Wh based on the findings in Bericht 166 documents on molybdenum and homogenous armour.

We can't preclude that Tirpitz won't seek battle at plus 25km either. It was German doctrine.

Here the Tirpitz holds a further advantage in radar firecontrol circa 1942. The Tirpitz's radar out ranges Washington's FC radar by 5,000 yards. It is also more durable and more reliable. Admiral Mustin has reported that Mk3 and Mk4 radars were usually knocked out by the first main battery salvo every single time during mid 1942. The Germans had already learned how to manage these problems. Indeed the Germans had 4 years of radar assisted firecontrol experience under their belts by this time and the Americans were only just getting started.
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Re: Rosselsprung 1942 actual combat

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Dave Saxton wrote:
alecsandros wrote:
Dave Saxton wrote: Indeed, in my opinion the unit with questionable deck protection in this scenario is not the Tirpitz but the Washington.
Why ? I don't see danger for Washington's decks from the 38cm gun at 30km or less.
I do. By the American IZ calculations and also using Krupp's calculas the deck protection is 105mm for Washington. Before I was giving a bit more based on the yaw deck (aka bomb deck), but given Thorsten's finding 105mm is probably correct.

At 28,000 yards the 38cm is penetrating 114mm Wh. I also think that STS was slightly inferior to Wh based on the findings in Bericht 166 documents on molybdenum and homogenous armour.

We can't preclude that Tirpitz won't seek battle at plus 25km either. It was German doctrine.

Here the Tirpitz holds a further advantage in radar firecontrol circa 1942. The Tirpitz's radar out ranges Washington's FC radar by 5,000 yards. It is also more durable and more reliable. Admiral Mustin has reported that Mk3 and Mk4 radars were usually knocked out by the first main battery salvo every single time during mid 1942. The Germans had already learned how to manage these problems. Indeed the Germans had 4 years of radar assisted firecontrol experience under their belts by this time and the Americans were only just getting started.

... space array or not the 37mm uper deck could knock off the cap because of the small angle of incidence. thus the impact with the MAD would have been done by a decaped shell, and probably with some imduced yaw and slighrly reduced velocity.
hence perforating the MAD would be problematic at any range below 33000y or 30km...
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Re: Rosselsprung 1942 actual combat

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alecsandros wrote:[... space array or not the 37mm uper deck could knock off the cap because of the small angle of incidence. thus the impact with the MAD would have been done by a decaped shell, and probably with some imduced yaw and slighrly reduced velocity.
hence perforating the MAD would be problematic at any range below 33000y or 30km...

Would not the American IZ calculations for the 14"/50 at 28,000 yards had taken this into account?

Assuming it did de-cap (the Germans used a minimum 50mm on de-capping decks for a reason) the maximal effect against de-capped shells was manifest by using homogenous armour that had a tensile strength of more than 80kg/mm2. STS as used didn't.
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Re: Rosselsprung 1942 actual combat

Post by alecsandros »

Dave Saxton wrote:
alecsandros wrote:[... space array or not the 37mm uper deck could knock off the cap because of the small angle of incidence. thus the impact with the MAD would have been done by a decaped shell, and probably with some imduced yaw and slighrly reduced velocity.
hence perforating the MAD would be problematic at any range below 33000y or 30km...

Would not the American IZ calculations for the 14"/50 at 28,000 yards had taken this into account?

Assuming it did de-cap (the Germans used a minimum 50mm on de-capping decks for a reason) the maximal effect against de-capped shells was manifest by using homogenous armour that had a tensile strength of more than 80kg/mm2. STS as used didn't.
Well I would add add that the 14" gun had a max range of 36800yards, ~4000 yards shorter than the 38cm gun. This is why the descent at 28000yards was 30* for the 14" gun and 23.7* for the German gun...this would probably affect decaping...
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Re: Rosselsprung 1942 actual combat

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Its a simple matter. The effective thickness of the North Carolina class total deck protection is 105mm and the German 38cm can defeat it at ranges exceeding 25km. The deck protection would need to exceed 130mm effective for it to provide protection vs the German 38cm out to 30km. It just doesn't factor up to that amount.
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Re: Rosselsprung 1942 actual combat

Post by Steve Crandell »

Dave Saxton wrote:Its a simple matter. The effective thickness of the North Carolina class total deck protection is 105mm and the German 38cm can defeat it at ranges exceeding 25km. The deck protection would need to exceed 130mm effective for it to provide protection vs the German 38cm out to 30km. It just doesn't factor up to that amount.
The penetration figure I have for the German 15" gun at 30,000 yds is a bit over 104mm. I think that would imply the end of the immune zone.
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