Rosselsprung 1942 actual combat

Historical what if discussions, hypothetical operations, battleship vs. battleship engagements, design your own warship, etc.
Steve Crandell
Senior Member
Posts: 954
Joined: Wed Feb 05, 2014 7:05 pm

Re: Rosselsprung 1942 actual combat

Post by Steve Crandell »

Bismarck fired four gun groups at Denmark Strait. A&B, then C&D about 10 seconds later. That is what the film shows, and I believe that was German doctrine for those ships.

If the seas were heavy Washington would have a lot more trouble than Tirpitz, and that might very well have a significant effect on the outcome.
Steve Crandell
Senior Member
Posts: 954
Joined: Wed Feb 05, 2014 7:05 pm

Re: Rosselsprung 1942 actual combat

Post by Steve Crandell »

alecsandros wrote:
Steve Crandell wrote:Alecsandros,

Were you using the German 50% dispersion number for salvo pattern length? They are different.
I uswd the 50% value multiplied by 1.5 which was the coefficient for 38cm turret (salvo) fire.

Also 50% value for 16" guns but multiplied by 2.43
Well, here you have it from delcryos, who's numbers you are using for a basis of your position here:

"The 4 gun pattern of 38cm is similar enough to the 16" 3 gun pattern to be a wash. Its roughly 5-10% larger but not 50% smaller."

In other words, for equal numbers of guns the patterns are going to be about the same for the two gun types.
alecsandros
Senior Member
Posts: 4349
Joined: Wed Oct 14, 2009 2:33 pm
Location: Bucharest, Romania

Re: Rosselsprung 1942 actual combat

Post by alecsandros »

Steve Crandell wrote:
alecsandros wrote:
Steve Crandell wrote:Alecsandros,

Were you using the German 50% dispersion number for salvo pattern length? They are different.
I uswd the 50% value multiplied by 1.5 which was the coefficient for 38cm turret (salvo) fire.

Also 50% value for 16" guns but multiplied by 2.43
Well, here you have it from delcryos, who's numbers you are using for a basis of your position here:

"The 4 gun pattern of 38cm is similar enough to the 16" 3 gun pattern to be a wash. Its roughly 5-10% larger but not 50% smaller."

In other words, for equal numbers of guns the patterns are going to be about the same for the two gun types.
No, the "numbers" come from MWA 39,16 and from Brad's TMD graph. check the thread again for more details - Delcyros used an average TMD across all interval, while at the same time applying a theoretical model for 4-gun battery fire [which is not likely to have been used - as he mentions himself].

Anyway, until either thread is settled, it is not alright to cross-talk between forums.

3-gun turret dispersion vs 2-gun turret dispersion will ALWAYS be about 50% bigger, for obvious reasons. Similarly, 4-gun salvos, if fired simultaneously, would yield larger patterns than 3-gun and 2-gun salvos.
Steve Crandell
Senior Member
Posts: 954
Joined: Wed Feb 05, 2014 7:05 pm

Re: Rosselsprung 1942 actual combat

Post by Steve Crandell »

alecsandros wrote: 3-gun turret dispersion vs 2-gun turret dispersion will ALWAYS be about 50% bigger, for obvious reasons. Similarly, 4-gun salvos, if fired simultaneously, would yield larger patterns than 3-gun and 2-gun salvos.
No, it is not linear. Pattern size does not increase in direct proportion to the number of guns firing.
alecsandros
Senior Member
Posts: 4349
Joined: Wed Oct 14, 2009 2:33 pm
Location: Bucharest, Romania

Re: Rosselsprung 1942 actual combat

Post by alecsandros »

Indeed, but for this number of guns (1, 2, 3, 4 guns), and with very close performances of individual guns, dispersion will increase from 1 to 4 guns used, albeit not at the same rate of increase. It is also a matter of range...
alecsandros
Senior Member
Posts: 4349
Joined: Wed Oct 14, 2009 2:33 pm
Location: Bucharest, Romania

Tirpitz vs Washington revisited

Post by alecsandros »

... In a revised estimate, I should add the following:

1) Based upon Tirpitz official rate of fire, the main battery was expected to fire 2rounds/minute in full (8-gun) salvo firings.
The actual firing would be done by 4 + 4 guns, with a delay of 2-4 seconds. Each group of 4 guns was fired with a slight delay, owing to the automatic system that kept the firing circuits opened until the muzzles of each gun actualy pointed exactly towards the same future position of the target.
This means very small patterns at long range (most likely similar to those of 2-gun and even 1-gun firings, so all shots within 150 meters at 25.000 meters). It also means that the spread may have been actualy to small, and actualy hiting a rapidly manouvreing target would be a daunting task, even for a high m-v gun.

2) Based upon Washington's action with Kirishima, Massachussets action off Casablanca, and USS West Virginia action with IJN Yamashiro, I can add the following:
- rate of fire for full-gun salvos in US 16" gun battleships under director control could easily have been 1.5 rounds/minute for ranges ~ 20km. West Virginia averaged 41 seconds salvo interval for her first 12 salvos. Massachussets and Washington, both without serious experience, averaged between 1.2 to 1.5 salvos/minute for 9-gun salvos, in actions at ranges of 7 - 19km.
- salvo patterns for 8-gun and 9-gun 16" guns were small. At 20km, Massachussets reported 200-250meters long salvos, of 3 to 9-guns. West Virginia reported average salvo length of 270 meters for 8-gun salvo at 21km.
Actual firings involved full-gun salvos against capital ships, with slight delays owing to the delay coils.

... After proper crew training, probable full-salvos could be fired at 1.8 salvos/minute (some guns of Washington and Massachussets actualy obtained this average. Alabama obtained 1.84 salvos/minute in 1945 during trials)

===

This implies that rate of fire of Tirpitz and Washington, considering excellently trained crews, was almost the same. Rates of fire COULD differ, if either ship was to fire independent salvos from turrets or turret groups. In this direction, Bismarck's salvo interval for forward turrets at Denmark Strait was as low as 23 seconds (2.61 salvos/minute), and AVKS tests hint towards the possibility of a 2.9 - 3.1 salvo/minute maximum rate of fire. On the other hand, during Short Range Battle Practice, all US 16" battleships averaged 2.5 salvos/minute/gun. So again, not much difference.

===

Then comes the rather subjective aspect concerning salvo pattern length:
> a tight pattern can produce more hits but requires the best functionalities in radar/optical directors, and almost perfect timings, while minimizing the possibility of discerning between watercolumns. This was mentioned during Bismarck's AVKS testings. What this system can do is to land 2 or more shells/full salvo (8 guns), because of individualy firing each of the 8 guns, not leaving to much room for gun whiplash effects to interfere between each other. But this only works with excellent systems, which may or may not have been operational. Certainly not all was operational on Bismarck, as she had 8 minutes of fire against Prince of Wales (6:01 - 6:09) at range 13 - 18km, and hit her 3 times - only when range was ~ 14km. The firing solution was lost immediately as Bismarck changed course from 220 to 270, and no more hits were obtained. This was probably due to the smoke screen, and the difficulties in assessing the real rate of range change.

> A somewhat larger pattern gives good spotting conditions, and due to the large number of shells, good hit probability for at least 1 shell / salvo)


===
Thus it all boils down to angle of fall of the shells and the number of shells actualy fired / minute. Angle of fall affects hiting space, and Tirpitz has a good advantage over Washington (38cm shells fall at 24* at 25000 meters, while 40.6cm shell falls at 30*). But the number of shells fired/minute would probably be advantaging Washington: about 14.6 shells fired/minute while Tirpitz would fire 14.4

===

Thus, with excellently functional systems and extra-trained crew, I would give a marginal hit advantage for Tirpitz, but in no way 2 vs 1, but more like 1.2 to 1 or so, at range of 25.000 meters. As the range decreases, the difference in falling angle and hiting space becomes smaller and smaller, thus the hit ratio comes down towards 1 for 1.

===

In terms of Immunity Zone, interestingly no ship is immune to the others fire at battles from 0 - 25km. At least not anything above the waterline - con towers, directors, radars, barbettes, turrets, funnells, first decks. Tirpitz machinery can be vulnerable to 406mm gunfire (through the armored decks). Washington's machinery also vulnerable to 380mm gunfire (through the belt).

This only leaves the magazines , which should be protected very well for those ranges (Tirpitz 150-180mm (?) decks, Washington ~ 120mm effective decks, both safe within 25000meters vs enemy fire)

===
So it would get messy and ugly, with the luckiest ship probably turning out as the victor. Tirpitz had more staying power due to her size and redundancy. But it would require several early critical strikes on the Washington without being to badly mauled herself in order to swing this battle in a German victory.
User avatar
Dave Saxton
Supporter
Posts: 3148
Joined: Sat Nov 27, 2004 9:02 pm
Location: Rocky Mountains USA

Re: Rosselsprung 1942 actual combat

Post by Dave Saxton »

The firing solution was lost immediately as Bismarck changed course from 220 to 270,...This was probably due to the smoke screen, and the difficulties in assessing the real rate of range change.
Perhaps but perhaps not. It could be because of anything. We dont know. This is speculation.
In terms of Immunity Zone, interestingly no ship is immune to the others fire at battles from 0 - 25km. At least not anything above the waterline - con towers, directors, radars, barbettes, turrets, funnells, first decks. Tirpitz machinery can be vulnerable to 406mm gunfire (through the armored decks).
This is not correct. The 16" won't attain 5" total deck penetration until the angle of fall exceeds ~30*. Besides at these ranges the shell will self destruct before it reaches the panzer deck.
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.
alecsandros
Senior Member
Posts: 4349
Joined: Wed Oct 14, 2009 2:33 pm
Location: Bucharest, Romania

Re: Rosselsprung 1942 actual combat

Post by alecsandros »

Dave Saxton wrote:
The firing solution was lost immediately as Bismarck changed course from 220 to 270,...This was probably due to the smoke screen, and the difficulties in assessing the real rate of range change.
Perhaps but perhaps not. It could be because of anything. We dont know. This is speculation.
... Bismarck straddled with 5 of her initial 8 salvos obtaining 5 or 6 hits, and 0 times with her later 6 salvos, obtaining 0 more hits.

In terms of Immunity Zone, interestingly no ship is immune to the others fire at battles from 0 - 25km. At least not anything above the waterline - con towers, directors, radars, barbettes, turrets, funnells, first decks. Tirpitz machinery can be vulnerable to 406mm gunfire (through the armored decks).
This is not correct. The 16" won't attain 5" total deck penetration until the angle of fall exceeds ~30*. Besides at these ranges the shell will self destruct before it reaches the panzer deck.[/quote]
... It was not 5" thick. It was 2" + 3.25". In terms of effetive thickness it may come close to 5", but the phenomenon of perforation would be as follows: 16" shell striking 2" weather deck. Maybe decaped, certainly fuzed, probably yawed. Regardless, it still remains at at least 2300 pds in weight, and travels at ~ 420-430m/s. Tremendous energy, which would slam against the 3.25" MAD. I doubt it would stop it. Possiby the shell would be inert (like so many bombs that went trhough Scharnhorst and Tirpitz deck system), but it would still be able to cause damage by shock alone. (And there is always the possibility of superperforation of 16" shells from Massachussets vesrsus Jean Bart armored decks...)
Steve Crandell
Senior Member
Posts: 954
Joined: Wed Feb 05, 2014 7:05 pm

Re: Rosselsprung 1942 actual combat

Post by Steve Crandell »

I think a valid point to be made is we can't be sure either way. No formula is going to tell us what would happen in an actual instance, and what did happen once might not happen the same way the next time. There is a lot of uncertainty. We all like to debate the minutia of small differences in protection and so on, but when it comes right down to it we don't really know. It's fascinating, but admittedly some of it comes down to the proverbial counting of the number of angels which can fit on a pinhead.

Edited several times to correct the problem I have with typing at 5:40am.
User avatar
Dave Saxton
Supporter
Posts: 3148
Joined: Sat Nov 27, 2004 9:02 pm
Location: Rocky Mountains USA

Re: Rosselsprung 1942 actual combat

Post by Dave Saxton »

No, there's not uncertainty on this matter. It will certainly be yawed and will certainly be de-capped (American naval AP are the easiest to de-cap by the way). The British found post war that de-capping is a very effective type of deck protection. Both yaw and de-capping increase the effective thickness, or the relative quality, depending on how you look at it, of the main armoured deck, resulting in an effective thickness equal to or exceeding the sum thickness. The bottom line is that the battle range would need to exceed 25km for the TP deck protection over the machinery to be defeatable by the 16" super heavy.

Nonetheless, since we are talking about ranges not exceeding 25km the shell is going to self destruct unless it is a dud. The amount of energy consumed at these lower angles of fall by the upper deck is significant as well.
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.
User avatar
Dave Saxton
Supporter
Posts: 3148
Joined: Sat Nov 27, 2004 9:02 pm
Location: Rocky Mountains USA

Re: Rosselsprung 1942 actual combat

Post by Dave Saxton »

Washington ~ 120mm effective deck
Its interesting to examin the deck protection of the North Carolina class in more detail. The IZ was designed to protect it from 1500lb 14"/50 shells out to 28,000 yards. (IZ 18,000 yards to 28,000 yards vs 14"). What was the deck penetration of the 14"/50 at 28k? 105mm. This is almost exactly what would be calculated using Krupp's square root of the sum of each deck squared method. It takes in to account no yaw or de-capping. But we know from the letter to Carnegie that yaw was considered in the design. It is certainly included in the South Dakota and Iowa class IZ calculations for 140mm effective needed to protect vs 2240 lb 16" out to 31,000 yards. If we take Krupp's calculation for yaw in this case (upper deck not thick enough to de-cap and the distance to the MAD small) it comes to about 120mm effective.

What if the Americans had used a German type scheme instead? By a German type scheme we are talking 50mm upper deck and greater distance between upper deck and MAD which would also include scarps making the belts more effective. The effective thickness of the decks could have been (95mm +50mm ) = 145mm effective thickness. Thus a much wider IZ vs 16" for very little greater weight cost (12mm thicker upper deck). There's probably no room left on 37,000 tons for an upper belt so it would have the Scharnhorst flaw. (The historical NC design has no upper belt and 95mm MAD much like SH anyway)

What if it additionally did away with the American practice of laying armour plates over a structural deck comprising the main armoured deck? In this case the MAD would be 125mm resulting in a total effective thickness of 175mm when the yaw deck comes into play. They could keep the Scharnhorst flaw with additional deck protection (especially vs bombs) or trade some of the additional deck not needed for protection vs 16" out to 30km for some upper belt. With the scarp triangle they do not need to slope the main belt resulting in better (but not perfect) protection vs below the belt hits.

If they went to 9x14" guns instead of 16" guns and 30+ knots we get a very interesting design indeed. I believe it would have been a superior design to the historical design. It gives an idea of what a Scharnhorst could have been with 9x 35cm guns too.
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.
User avatar
tommy303
Senior Member
Posts: 1528
Joined: Mon Oct 18, 2004 4:19 pm
Location: Arizona
Contact:

Re: Rosselsprung 1942 actual combat

Post by tommy303 »

Nonetheless, since we are talking about ranges not exceeding 25km the shell is going to self destruct unless it is a dud.
In 1942 one cannot rule out a USN AP shell being a dud, as problems with the Base Detonating Fuze Mk 21 Mod 0 made duds almost the rule rather than the exception unless the fuze was only recently installed in the shell.

Their shoulders held the sky suspended;
They stood and Earth's foundations stay;
What God abandoned these defended;
And saved the sum of things for pay.
alecsandros
Senior Member
Posts: 4349
Joined: Wed Oct 14, 2009 2:33 pm
Location: Bucharest, Romania

Re: Rosselsprung 1942 actual combat

Post by alecsandros »

Dave Saxton wrote:No, there's not uncertainty on this matter. It will certainly be yawed and will certainly be de-capped (American naval AP are the easiest to de-cap by the way). The British found post war that de-capping is a very effective type of deck protection. Both yaw and de-capping increase the effective thickness, or the relative quality, depending on how you look at it, of the main armoured deck, resulting in an effective thickness equal to or exceeding the sum thickness. The bottom line is that the battle range would need to exceed 25km for the TP deck protection over the machinery to be defeatable by the 16" super heavy.

Nonetheless, since we are talking about ranges not exceeding 25km the shell is going to self destruct unless it is a dud. The amount of energy consumed at these lower angles of fall by the upper deck is significant as well.
... What is not certain is IF the 5 + 8cm arrangement would stop the projectile from entering the machinery spaces (intact or not). Perforations with projectile in broken condition may start at 21km.

Another interesting aspect to consider is that the 16"/L45 gun had a low muzzle velocity, which was constantly decreasing as the gun fired another shell and slowly worn off. According to a discussion with Bill Jurens, and hopefully not simplifyiung things to much, an average decrease of m-v of 1 ft/second for every shell fired/gun was expected at the 16"L/45 guns. Thus, with 50 shells fired, the m-v would decrease from 2300ft/sec to 2250ft/sec, thus requiring a higher angle of elevation of the gun, leading to a slightly larger angle of impact (but with a corresponding lower terminal velocity than for the new gun). It's the little things...

And another thing: having 2 armor decks is a good thing for protecting the vital spaces. However, when the issue of cumulative damage is scrutinized, there are more disadvantages than advantages: if 1 projectile passes through the upper 5cm deck, and causes a hole in it, than, after repeated subsequent hits, a probabilty exists that a SECOND shell would strike in the same area, and would not be slowed/decaped, but it would go and strike directly the main armor deck.

In a prolonged engagement this could happen...

===
This said, I wouldn't say Tirpitz machinery was "safe" from damage from 16"/L45 guns inside 25km... And possible damaging hits may appear from 21km and above.
User avatar
RF
Senior Member
Posts: 7760
Joined: Wed Sep 20, 2006 1:15 pm
Location: Wolverhampton, ENGLAND

Re: Rosselsprung 1942 actual combat

Post by RF »

alecsandros wrote: And another thing: having 2 armor decks is a good thing for protecting the vital spaces. However, when the issue of cumulative damage is scrutinized, there are more disadvantages than advantages: if 1 projectile passes through the upper 5cm deck, and causes a hole in it, than, after repeated subsequent hits, a probabilty exists that a SECOND shell would strike in the same area, and would not be slowed/decaped, but it would go and strike directly the main armor deck.
In a prolonged engagement this could happen....
But the statistical probability wouldn't be very high though, would it?
In a prolonged action I could see it happen once, perhaps even twice - but not achieve a succession of crippling multiple hits unless the target is slowed down by other means and becomes a sitting target.
''Give me a Ping and one Ping only'' - Sean Connery.
alecsandros
Senior Member
Posts: 4349
Joined: Wed Oct 14, 2009 2:33 pm
Location: Bucharest, Romania

Re: Rosselsprung 1942 actual combat

Post by alecsandros »

RF wrote:
alecsandros wrote: And another thing: having 2 armor decks is a good thing for protecting the vital spaces. However, when the issue of cumulative damage is scrutinized, there are more disadvantages than advantages: if 1 projectile passes through the upper 5cm deck, and causes a hole in it, than, after repeated subsequent hits, a probabilty exists that a SECOND shell would strike in the same area, and would not be slowed/decaped, but it would go and strike directly the main armor deck.
In a prolonged engagement this could happen....
But the statistical probability wouldn't be very high though, would it?
In a prolonged action I could see it happen once, perhaps even twice - but not achieve a succession of crippling multiple hits unless the target is slowed down by other means and becomes a sitting target.
It wouldn't be very high. But it only needs to happen once... in a bad place...
Post Reply