Bismarck and her contemporaries

Discussions about the history of the ship, technical details, etc.
dunmunro
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Re: Bismarck and her contemporaries

Postby dunmunro » Mon Sep 27, 2010 10:32 am

JtD wrote:That's exactly where I got the information from. Washington started 65° off Kirishimas bow and ceased firing 85° off the stern, therefore a classic drive by shooting, with most of the damage done from a position almost exactly to the side of Kirishima.

Now if you want to add vertical inclination to reach a 45° degree figure, you'd need between 40° and 45°. A sip listing that bad is capsizing, even if you subtract 10° of belt inclination.



Kirishima inclination:
http://www.navweaps.com/index_lundgren/ ... lcanal.pdf (p17)
0100 open fire - Inclination = 34deg
0101 - inclination = 26deg
0102.5 cease fire - inclination = 9deg
0103 = minimum inclination
0104 resume fire - inclination = 10deg
0105 inclination = 46deg
0106 inclination = ~60deg
0107 cease fire inclination = ~80deg

The angle of fall of the 16" projectiles is 5.5degs minimum (8500yds)
The inclination of the KGV armour over the magazines is 5 to 10 degs for any hits on those areas.

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Re: Bismarck and her contemporaries

Postby JtD » Mon Sep 27, 2010 11:07 am

I don't see that written down in the text, anywhere, so I'm assuming you've read that from the chart. The chart would also say that Washington opened fire at Kirishima with a bearing of 358° true, however it did with 8° true. This can also be seen in original charts. Since Washington hit, there's reason to assume that the original charts do not need much of a correction. First round of firing was ceased at 0103, so during that time Kirishima went through a full broadside engagement with maximum inclination of 25° in the initial stage. During these three minutes, Kirishima received most of the crippling damage.

The inclination of PoW side armour over the magazines reaches from 1° to 10°, with most parts of the forward magazines at 5° and less. The machinery spaces have no inclination worth mentioning, and this is where most of the hits occurred.

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Re: Bismarck and her contemporaries

Postby dunmunro » Mon Sep 27, 2010 4:45 pm

JtD wrote:I don't see that written down in the text, anywhere, so I'm assuming you've read that from the chart. The chart would also say that Washington opened fire at Kirishima with a bearing of 358° true, however it did with 8° true. This can also be seen in original charts. Since Washington hit, there's reason to assume that the original charts do not need much of a correction. First round of firing was ceased at 0103, so during that time Kirishima went through a full broadside engagement with maximum inclination of 25° in the initial stage. During these three minutes, Kirishima received most of the crippling damage.

The inclination of PoW side armour over the magazines reaches from 1° to 10°, with most parts of the forward magazines at 5° and less. The machinery spaces have no inclination worth mentioning, and this is where most of the hits occurred.


I measured the inclination at the stated time intervals using the measuring tool in the GIMP. The original chart shows an inclination of 30degs at 0100. However, with such a short ToF, the original gunnery plot could have substantial errors and still result in many hits, so the plot in the Lundgren article is probably more accurate. Again, I not claiming that KGV armour could stop all the hits, but it would likely have stopped some while others would not have fused.

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Re: Bismarck and her contemporaries

Postby JtD » Mon Sep 27, 2010 4:51 pm

So, which ones would have been stopped, which ones would not have fused?

It never ceases to amaze me how people cherry pick figures that suit them, really. Feel free to contact Mr. Lundgren and ask him if he thinks if Washington opened fire with 358° true, as the chart he published and you're using for gospel indicates, or if it was 8° true as all the other data he published and you chose to ignore indicates.

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Re: Bismarck and her contemporaries

Postby alecsandros » Mon Sep 27, 2010 5:33 pm

dunmunro wrote: Again, I not claiming that KGV armour could stop all the hits, but it would likely have stopped some while others would not have fused.

Hi Duncan,
I ran some numbers in facehard:
20* target inclination, 5.5* projectile falling angle; 1810fps impact velocity; 2700pds mass, caped.
The impact obliquity is 31.5*, at least from my calculation -- arccos (cos20*) x (cos5.5*)

Facehard says "no holing of the plate, projectile broken".

So, maybe.. ?

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Re: Bismarck and her contemporaries

Postby JtD » Mon Sep 27, 2010 5:42 pm

alecsandros wrote:The impact obliquity is 31.5*, at least from my calculation -- arccos (cos20*) x (cos5.5*)


The result of that equation is 20.7°.

Nominal velocity at 10000yards was 1900fps, so it can be expected to not be lower than that at 8500.

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Re: Bismarck and her contemporaries

Postby Bgile » Mon Sep 27, 2010 7:16 pm

alecsandros wrote:
dunmunro wrote: Again, I not claiming that KGV armour could stop all the hits, but it would likely have stopped some while others would not have fused.

Hi Duncan,
I ran some numbers in facehard:
20* target inclination, 5.5* projectile falling angle; 1810fps impact velocity; 2700pds mass, caped.
The impact obliquity is 31.5*, at least from my calculation -- arccos (cos20*) x (cos5.5*)

Facehard says "no holing of the plate, projectile broken".

So, maybe.. ?


Well, there we have it! PoW was completely immune to 16" gunfire. ;)

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Re: Bismarck and her contemporaries

Postby dunmunro » Mon Sep 27, 2010 8:05 pm

Bgile wrote:
alecsandros wrote:
dunmunro wrote: Again, I not claiming that KGV armour could stop all the hits, but it would likely have stopped some while others would not have fused.

Hi Duncan,
I ran some numbers in facehard:
20* target inclination, 5.5* projectile falling angle; 1810fps impact velocity; 2700pds mass, caped.
The impact obliquity is 31.5*, at least from my calculation -- arccos (cos20*) x (cos5.5*)

Facehard says "no holing of the plate, projectile broken".

So, maybe.. ?


Well, there we have it! PoW was completely immune to 16" gunfire. ;)


No, not quite...but target inclination and modern armour can defeat AP rounds, even at relatively close ranges.

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Re: Bismarck and her contemporaries

Postby dunmunro » Mon Sep 27, 2010 8:08 pm

JtD wrote:So, which ones would have been stopped, which ones would not have fused?

It never ceases to amaze me how people cherry pick figures that suit them, really. Feel free to contact Mr. Lundgren and ask him if he thinks if Washington opened fire with 358° true, as the chart he published and you're using for gospel indicates, or if it was 8° true as all the other data he published and you chose to ignore indicates.


So your saying that Lundgren's chart and Washington's chart are both wrong? They both show target inclination of at least 30deg at 0100.

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Re: Bismarck and her contemporaries

Postby JtD » Mon Sep 27, 2010 8:25 pm

Funny one, really. The original chart has a discontinuity exactly at 0100. So if we were to count seconds, and to assume that Washington did not open fire before 0100:00, then it is less than 30° - because we go with the course plotted after 0100. If we consider this a typical inconsistency of historical data and use and average of the two courses, it is less than 30° and if we focus on the fact that the inclination at the starting point of the engagement was the largest, we can consider it insignificant, in particular since it would be less than 30° within the frigging flight time of the shells.
If we, however, just want to be right in order to be right, we can search for trivia and very well insist on an inclination of >30°, even though this is idiotic since it is irrelevant for all practical purposes.

So, which hits would have been stopped by PoW armour, which ones would not have fused?

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Re: Bismarck and her contemporaries

Postby dunmunro » Mon Sep 27, 2010 9:20 pm

JtD wrote:Funny one, really. The original chart has a discontinuity exactly at 0100. So if we were to count seconds, and to assume that Washington did not open fire before 0100:00, then it is less than 30° - because we go with the course plotted after 0100. If we consider this a typical inconsistency of historical data and use and average of the two courses, it is less than 30° and if we focus on the fact that the inclination at the starting point of the engagement was the largest, we can consider it insignificant, in particular since it would be less than 30° within the frigging flight time of the shells.
If we, however, just want to be right in order to be right, we can search for trivia and very well insist on an inclination of >30°, even though this is idiotic since it is irrelevant for all practical purposes.

So, which hits would have been stopped by PoW armour, which ones would not have fused?


I don't understand what you are getting so upset about. This is the original post, that sparked this discussion:

dunmunro wrote:
Bgile wrote:
alecsandros wrote: ... So, again, I don't understand how you can view these combatants as "comparable"... ?


Has there ever been a fight between "comparable" battleships? I don't think so.

I also don't think that PoW's armor would have done much better than Kirishima's at 8,500 yds.


Some other match ups:
Renown versus S&G
Warspite and Giulio Cesare (this seems pretty close in terms of specs)

Depending on the inclination of the ship, KGV's belt armour might have stopped some of the 16in hits, but more importantly, since she was an AoN design many of the hits would have simply passed through without fusing.


I was merely pointing out that a combination of target inclination and thick armour can defeat AP rounds even at comparatively close range. I analysed the target inclination based upon both available charts and posted my findings. However, since you asked:

Hits 1, 12, 13, 14, 2, 3, 4, 10 and 17 have a good probability of not fusing. Hit 19, assuming that it was scored towards the end of the action, would have been a very high obliquity hit as would hit 15 and 16, and so there is a good probability of these hits being defeated.
http://www.navweaps.com/index_lundgren/ ... alysis.pdf, p8. Also see the armour diagrams on page 17-18 and note the armour distribution which is almost guaranteed to fuze BB calibre AP projectiles.

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Re: Bismarck and her contemporaries

Postby JtD » Mon Sep 27, 2010 10:46 pm

The document contains the likely inclination for each hit, and the obliquity is in the "not nearly perpendicular" zone only for hit 19.

You're assuming that 25mm do not fuse the shell? Or am I remembering thicknesses wrong? I'd say they'd fuse, based on the 16" performance against Richelieu, with a similar protection scheme.

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Re: Bismarck and her contemporaries

Postby dunmunro » Tue Sep 28, 2010 12:07 am

JtD wrote:The document contains the likely inclination for each hit, and the obliquity is in the "not nearly perpendicular" zone only for hit 19.

You're assuming that 25mm do not fuse the shell? Or am I remembering thicknesses wrong? I'd say they'd fuse, based on the 16" performance against Richelieu, with a similar protection scheme.


Not necessarily:

The base fuze of the German 38 cm armor-piercing projectiles had a fixed 0.035-second black-powder delay base fuze designated the "Bd.Z. C/38" (Base Fuze ("Bodenzunder") for 38 cm armor-piercing projectiles). This fuze was much improved over its WWI, 0.025-second-delay predecessor, but still had poor reliability from reports from WWII battles. Many such fuzes would be reliably set off at right-angles impact by either a hit on a single steel plate (any kind of steel) of over 0.07 times the projectile diameter (0.07 'caliber') in thickness - 1.05" (27 mm) for the German 38 cm projectile - or by hitting two steel plates spaced a few feet apart each of which was at least 0.05 caliber thick - 0.75" (19 mm) for the 38 cm projectile. Certain highly 'safed' base fuze designs (improved safety during handling and storage prior to firing, not especially for better function at the target, though the latter also was incorporated in some of these designs) introduced during the late 1930's and during WWII by the U.S. and British navies, such as the widely-used U.S. Mark l8, 19, 20, and 21 base fuzes, eliminated the multiple plate sensitivity, requiring a minimum 0.07 caliber plate at right angles. At oblique impact, some designs allowed a thinner plate, but other primitive or poorly-designed fuzes would fail to function at all at any significant obliquity (only after WWI was oblique impact made a major projectile or fuze criterion). U.S. WWII base fuzes would be reliably set off by roughly 0.0625 caliber-thickness steel plates at 20o obliquity (16" (406 mm) projectile tests) and 0.03125-caliber-thickness steel plates at 80o obliquity (5" (127 mm) projectile tests), giving the following crude formula for the minimum plate thickness in calibers to set off a base fuze, which I will call Tfuze:

Tfuze = (X){(0.5)[1 + COS(2(OB))] + (0.4537)SIN5.7019 (OB)}

where OB is the Obliquity Angle (zero is right angles to the plate) and "X" is 0.07 for a single plate or, for those fuzes set off by two plates hit in rapid succession, 0.05 for each of the two plates. The maximum obliquity value OB to use in this formula is 61o, which reaches the minimum single-plate value of 0.03125 caliber, which is the "floor" value for that case; above 61o obliquity use the 0.03125 caliber minimum for the single plate case - 0.47" (12 mm) for the 38 cm projectile - or a 0.0223 caliber minimum for the two-plate case - 0.33" (8 mm) for the 38 cm projectile. Note that these values are for an undamaged fuze and do not care whether or not penetration was achieved. Also, above 80o obliquity fuze function is very chancy - many fuzes, including the German 38 cm design, attempted to include a "graze" feature for high obliquity impacts, but I do not know how effective most of these were. I am not sure as to the operational boundaries of the German fuze, but looking at a cross-section of it leads me to assume that it follows the above formula and retains the two-plate function due to its rather simple internal configuration (the Japanese used base-fuzes of very similar design); it was not of the "absolute" safety, intricate WWII U.S. type like the Mark 21.

http://www.combinedfleet.com/okun_biz.htm

The whole point of AoN designs was to not set off the fuzes if possible, unless the shell had a reasonable probability of being defeated by armour. This minimized the damage to South Dakota.

Besides which, hits 1 through 5 were on the superstructure, and a KGV had even thinner plating (20lb?) here.

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Re: Bismarck and her contemporaries

Postby JtD » Tue Sep 28, 2010 6:58 am

I don't think that hits 1 to 5 would all have been hitting superstructure on PoW, it looks more like deck hits to me. I superimposed a PoW sketch over the shell sketch of Kirishima, both ships have similar lengths so you can rather easily find the probable hit locations on PoW.

I know what the point of AON is, but it's a fact that it didn't always work as it should and that, with the splinter belts extending for and aft, PoW wasn't a true all or nothing design.

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Re: Bismarck and her contemporaries

Postby alecsandros » Tue Sep 28, 2010 2:42 pm

JtD wrote: The result of that equation is 20.7°.


My trig may be a little rusty.
However, what I meant was that the obliquity of the impact corresponds to a 0* target angle (perpendicular shooting), striking the plate at 30.5*.

As you can see, the decrease in penetration is significant at 30* or more obliquity, even at this very-high-speed.
===============

What is more important and has elluded the conversation so far:

- 1800 fps speed may be above the shatter velocity for this type of shell.
[Krupp found that 630m/s was the max speed for their 380mm shells. Above that speed, the shells would shatter without perforating, because of the very high impact energy.
This may be a reason why Rodney's shells exploded against Bismarck armor on May 27th.]

- British post-1930 cemented armor was amongst the best (many say the best) employed in WW2 battleships.
- the ratio between shell diamter (D) and plate thickness (T) is drasticaly worse in an engagement with KGV than with Kirishima:
Kirishima belt - 8"
KGV belt - 15"
Washington's guns - 16"

=> D/T1 = 16"/8" = 2
D/T2 = 16"/15" = 1.06

Both plate quality and D/T strongly affect projectile penetration and perforation.

===========

Cheers,
Alex


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