Bismarck and her contemporaries

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

Postby JtD » Tue Sep 28, 2010 3:34 pm

In order to achieve a total obliquity of 30.5° with a ship 20° off your beam, you'd need to present a total inclination of 23.5° (falling shot, inclined armour). The only instance of that (30°+ obliquity) occurring during that engagement would be if a shell hit the far side of the target, meaning around the rear magazines early on or around the forward magazines later on, where the curvature of the ships hull adds to the off beam position of Washington.

630m/s equals about 2050 fps, and from I have read German shells had a comparatively large chamber for the HE content, making their shells more prone to shattering than other nations shells. I think it is safe to assume that the 16" would not shatter at 2000fps.

I know that PoW's protection if far better than Kirishimas, that's a pretty obvious fact. However, I severely doubt that it would have made a difference in that instance. We know that the US 16" did penetrate the 26" faceplate of the Yamato class turrets, with 1700fps at about 0° obliquity. It also penetrated at 2000fps btw., and did not break up. Now even with the better quality of the British armour and the somewhat larger obliquity in the scenario, there's little doubt in my mind that if the projectile manages 26" at 1700 fps, it will manage 15", let alone 14" at 1900+ fps.

It is certainly more interesting to see if the projectiles did hit areas that would prevent them from fusing. I doubt it, because at 5.5° angle of fall, a shell penetrating the side would sooner or later hit a deck, where the high obliquity would certainly suffice to arm the fuse. Hits to the superstructure might get through, even though it appears to me that the hit 1 would have hit the protected conning tower.

I disagree with dunmunroe in that I don't think "many" hits would not have fused, and in the bottom line I think that a KGV class BB would not have faired better than Kirishima eventually, it would not have been able to make it back to base on its own. Maybe it would have stayed afloat a little longer, but maybe it would have blown up right away.

dunmunro
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Re: Bismarck and her contemporaries

Postby dunmunro » Tue Sep 28, 2010 9:23 pm

JtD wrote: We know that the US 16" did penetrate the 26" faceplate of the Yamato class turrets, with 1700fps at about 0° obliquity. It also penetrated at 2000fps btw., and did not break up. Now even with the better quality of the British armour and the somewhat larger obliquity in the scenario, there's little doubt in my mind that if the projectile manages 26" at 1700 fps, it will manage 15", let alone 14" at 1900+ fps.



Can you provide a source for this statement? The SV seems a little low for that kind of penetration.

JtD
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Re: Bismarck and her contemporaries

Postby JtD » Tue Sep 28, 2010 9:39 pm

Source is the www. 1700fps is partial penetration.

http://www.navweaps.com/index_tech/tech-040.htm

Edit: Brain fart on my part: 1700fps the armour was perforated, but the projectile did not penetrate. 1840fps were calculated to be necessary for penetration.

dunmunro
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Re: Bismarck and her contemporaries

Postby dunmunro » Tue Sep 28, 2010 10:23 pm

JtD wrote:Source is the www. 1700fps is partial penetration.

http://www.navweaps.com/index_tech/tech-040.htm

Edit: Brain fart on my part: 1700fps the armour was perforated, but the projectile did not penetrate. 1840fps were calculated to be necessary for penetration.


Holing the plate is not a partial penetration, and of course this test is done at zero obliquity which cannot occur at the stated SVs against an actual turret during combat. Additionally, from the article referenced: ...the U.S. Navy 16"/50 firing a 16" Mark 8 Mod 6 AP projectile (the later Mod 7 and Mod 8 designs were post-WWII...

The Mk 8-6-8 was a very late war design, not in service in 1942, and maybe not ever in a seagoing WW2 ship.

JtD
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Re: Bismarck and her contemporaries

Postby JtD » Tue Sep 28, 2010 10:41 pm

Mod 6 was said to be considerably better at obliquities 35° and up, afaik.

I'd consider all this a bit moot as it is 26+" vs. 15" required.

dunmunro
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Re: Bismarck and her contemporaries

Postby dunmunro » Tue Sep 28, 2010 11:39 pm

JtD wrote:

I disagree with dunmunroe in that I don't think "many" hits would not have fused, and in the bottom line I think that a KGV class BB would not have faired better than Kirishima eventually, it would not have been able to make it back to base on its own. Maybe it would have stayed afloat a little longer, but maybe it would have blown up right away.


I really wish that people would pull out a calculator and/or NAab or Facehard, or some similar action before making blanket statements. Nathan Okun has carefully modelled Facehard based upon USN armour penetration trials, so we can be reasonably certain that NAab and Facehard will reflect closely what would actually happen. For example NAab states that at 36 deg total inclination and 1900fps SV, against RN 14.7in armour, that only a partial penetration will occur and there is enough uncertainty about the inclination, that this cannot be ruled out. Additionally, some of the USN 16" hits dived under Kirishima's armour and this is much less likely to occur against a KGV. In summary, a KGV class (or a South Dakota) would be badly damaged after enduring 20 16" hits, with the same general location as on Kirishima, but not nearly to the same extent as happened to Kirishima.

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Re: Bismarck and her contemporaries

Postby alecsandros » Wed Sep 29, 2010 6:19 am

I put a nice reply last night, that disapeared in the forum.
Most of what I wrote was anyway discussed in the last posts.

One more aspect however:
The 630mps figure I mentioned concerns German L4.4 APC shells (the same as the ones used by Bismarck), it does not refer to HE shells.
However, the German 380mm shell carried about the same explosive quantity as the US 406mm shells, and that at a much shorter shell (380mm shell - 1.67m including windscreen, 406mm shell - 1.91m). So, as JtD mentioned, the ratio between filler and shell mass remains larger for the German shells, possibly leading to somewhat lower shatter velocities.

[I'm not sure about that, though, as Krupp paid very much attention to keeping the shells intact during perforations]

The shatter velocity was also associated with plate thickness. IIRC, the 630m/s was the shatter velocity against 12" KC n/A plates. The shatter velocity decreased as the plate's thickness increased.

So, against 15" very high-quality plate, the shatter velocity for 380mm shells may have been as low as 530-550 m/s (my estimate :D ). How this translates to US 406mm shells, I don't know. But it's worth taking into consideration, I guess...

JtD
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Re: Bismarck and her contemporaries

Postby JtD » Wed Sep 29, 2010 8:09 am

dunmunro wrote:For example NAab states that at 36 deg total inclination and 1900fps SV, against RN 14.7in armour, that only a partial penetration will occur and there is enough uncertainty about the inclination, that this cannot be ruled out.


You're joking, right?

I wish people weren't through and through fanboys that, once their favourite ship is in question, threw overboard all reason and go long stretches just to show how well it would perform.

Lundgren, btw., shows all hits occurring before the turning of Kirishima with +20° to -15° inclination, and while I don't think he intended his sketches to be used for that purpose, it is the most accurate source available to me. And as far as I can tell, there'd be
1 hit to the conning tower
2 hits to the belt covering the machinery, 20° inclination
1 hit to rear magazines, -13° inclination
1 hit to forward magazines, -15° inclination
2 hits to turret 1, -15° inclination (facing of turret not known to me)
1 hit into the waterline of the bow
1 hit into the rudder armoured box
3 hits into the hull above the armour
1 hit into the superstructure of the bridge
3 hits into the bow section
3 hits into the stern section
1 hits into the screws

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Re: Bismarck and her contemporaries

Postby alecsandros » Wed Sep 29, 2010 8:46 am

Unfortunately, as nice and neat mr Lundgren's analysis is, is far from being a definitive source regarding the engagement between Washington and Kirishima.
The description of battle damage and damage analysis are very interesting, but they are not suported by the analysis of the wreck, and neither by the usual underwater behavior of large-caliber shells.

Bill Jurens raised several important questions, such as:
- why is a large part of the ship missing (the stern, IIRC), as the ship was not torpedoed, and a possible underwater explosion simply could not have "vanished" such a large portion
- what is the evidence that the filmed wreckage is actualy Kirishima, and not Hiei, which sank rather close to the battle's sight ?
- if the wreckage is that of Kirishima, where is the visual evidence of the numerous large-scale impacts? (Lundgren only filmed 3 holes, 2 of which were very simetrical and were in about the spot Kirishima had some exhaust valves, or something like that)

Nathan Okun, on several interventions on the forum, explained several tests of underwater trajectories for BB caliber shells. Bill Jurens, on his "re-analysis of the loss of HMS Hood", published on Warship International, made also several comments on the behavior of large-caliber shells when striking water, and their probable trajectories.

From those readings, it appears that the underwater trajectory (that Lundgren mentions for several impacts) is only possible if some conditions are met. Most importantly, the impact velocity should be in a given scale (450-550m/s), the impact angle in a certain interval (above 15* for most shells).
In the given situation - with shells at 600m/s and 5* falling angle, it would be next to impossible for a shell to remain intact and travel underwater. Most likely, they would explode on contact with the water, or, if lucky, act as solid shots and hit the ship without exploding (but provoking flotation damage).
However, Lundgren's drawing shows at least 6 underwater hits, which would imply an extraordinary "luck" factor, as said above...

My impression is that Washington's initial report is the best source for reconstructing how many shells struck Kirishima. And, MAYBE, we could add 2-3 hits that weren't spotted by them ? (underwater and non-explosive hits, such as some passing through the forecastle). But 20 hits is an big overestimation, IMO.

Cheers, Alex

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Re: Bismarck and her contemporaries

Postby JtD » Wed Sep 29, 2010 9:06 am

There are 6 hits into the waterline and 1 below (hitting the rudder) illustrated by Mr. Lundgren.

If underwater hits are impossible, why did Kirishima sink at all?

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Re: Bismarck and her contemporaries

Postby dunmunro » Wed Sep 29, 2010 11:47 am

On the one hand JTD argues that all the hits must be low obliquity, and then, in the same breath argues, that despite the low obliquity that even the hits that don't strike heavy armour will detonate...He wants it both ways and simply ignores any information that that he finds inconvenient.

I am also sceptical of 20 hits, as claimed by Lundgren, but I have simply accepted it as a basis for discussion.

KGV's magazines are on the lowest level of the ship, and it is impossible for a properly fused 16" shell fired at these close ranges to dive deeply enough to penetrate them. 16" shells that did fall short and dive would almost certainly strike KGV's belt armour and thus have a probability of being stopped or detonated prior to the TDS armoured bulkhead.

The fact that a brand new design AoN BB might perform better than a pre-WW1 design BC even against this kind of pounding, should not be controversial but instead of having an academic discussion about the merits of an AoN design and the effects of target inclination on penetration we get locked into a kind of rigid discussion where all the parameters are fixed to suite one point of view.

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Re: Bismarck and her contemporaries

Postby JtD » Wed Sep 29, 2010 1:21 pm

In case you did not read what you wrote:
"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)"

That's 25mm. That's hull thickness of KGV. Reliably sets off at 20°. So obviously, it wouldn't "reliably" set off the fuses, however, it is absolutely possible that it did. It might be worth noting that the unarmoured hull of the class apparently had a higher inclination than the belt. In addition to that, the shells would hit decks or transverse bulkheads at far higher obliquities, which posed their own challenges, but would reduce the nominal thickness of the material to 13mm. That said, 28mm would set it off at any angle. I couldn't find the plate thicknesses used in the bow and stern area, feel free to post if you know. Maybe you can find the some numbers for the same areas on Kirishima as well, showing how much thicker they were.

Also, if the belt was defeated, the remaining projectile speed would need to be below about 600 fps in order to have it detonate within the TDS, and even if it did there is no reason to assume that the bulkhead would have dealt with the explosion. However, the 600 fps is unlikely if we assume total inclinations of 20° and less for the magazine hits.

And I'm not arguing "better than Kirishima", I'm arguing "good enough". And no, at the obliquities in question, it wouldn't have been good enough. Feel free to make that discussion academic, by going back to the 45° you immediately invented to prove your point.

I'll argue that an S-Boat would have done better still, since it wouldn't have been hit in the first place.

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Re: Bismarck and her contemporaries

Postby alecsandros » Wed Sep 29, 2010 1:23 pm

JtD wrote:
If underwater hits are impossible, why did Kirishima sink at all?


A very interesting question.
My impression of the damage suffered by Kirishima is the following:

SInce Washington was on a almost paralel course to Kirishima, the shots fired were almost perpendicular to Kirishima's direction of movement.
The 2700pds mk8 shell fired from 16"L45 gun has a giant impact energy at 8500y.
The thickest part of Kirishima's armor that got hit (according to eye-witnesses) was the upper-belt, of 149mm pre-1916 cemented armor. It's armor equivalent was 120mm - 127mm of British post-1930 CA.

Factoring in the shell's properties at the point of impact (600mps, 2700pds, 610pds cap weight, 0.035s fuze delay) with the armor properties (149mm but of low quality according to WW2 standards), we arive at complete penetration, with an exit velocity of 510-520 m/s.
Provided the shell functioned properly, 510m/s and 0.035s fuze delay would mean close to 18 meters covered before detonation..
Kriishima was a rather "thin" design, with the widest part at 28 meters.

So, I think some shells actualy had enough energy to pass all the way through, and explode on the other side.

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Re: Bismarck and her contemporaries

Postby Serg » Wed Sep 29, 2010 2:14 pm

JtD wrote:There are 6 hits into the waterline and 1 below (hitting the rudder) illustrated by Mr. Lundgren.

If underwater hits are impossible, why did Kirishima sink at all?

Because of flooding above her armour deck and some "help" from her crew. It looks like Warspite at Jutland when 1 or 2 hits slightly above the waterline considerably reduced her metacentric height.

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Re: Bismarck and her contemporaries

Postby Bgile » Wed Sep 29, 2010 5:28 pm

alecsandros wrote:Unfortunately, as nice and neat mr Lundgren's analysis is, is far from being a definitive source regarding the engagement between Washington and Kirishima.
The description of battle damage and damage analysis are very interesting, but they are not suported by the analysis of the wreck, and neither by the usual underwater behavior of large-caliber shells.

Bill Jurens raised several important questions, such as:
- why is a large part of the ship missing (the stern, IIRC), as the ship was not torpedoed, and a possible underwater explosion simply could not have "vanished" such a large portion
- what is the evidence that the filmed wreckage is actualy Kirishima, and not Hiei, which sank rather close to the battle's sight ?
- if the wreckage is that of Kirishima, where is the visual evidence of the numerous large-scale impacts? (Lundgren only filmed 3 holes, 2 of which were very simetrical and were in about the spot Kirishima had some exhaust valves, or something like that)

Nathan Okun, on several interventions on the forum, explained several tests of underwater trajectories for BB caliber shells. Bill Jurens, on his "re-analysis of the loss of HMS Hood", published on Warship International, made also several comments on the behavior of large-caliber shells when striking water, and their probable trajectories.

From those readings, it appears that the underwater trajectory (that Lundgren mentions for several impacts) is only possible if some conditions are met. Most importantly, the impact velocity should be in a given scale (450-550m/s), the impact angle in a certain interval (above 15* for most shells).
In the given situation - with shells at 600m/s and 5* falling angle, it would be next to impossible for a shell to remain intact and travel underwater. Most likely, they would explode on contact with the water, or, if lucky, act as solid shots and hit the ship without exploding (but provoking flotation damage).
However, Lundgren's drawing shows at least 6 underwater hits, which would imply an extraordinary "luck" factor, as said above...

My impression is that Washington's initial report is the best source for reconstructing how many shells struck Kirishima. And, MAYBE, we could add 2-3 hits that weren't spotted by them ? (underwater and non-explosive hits, such as some passing through the forecastle). But 20 hits is an big overestimation, IMO.

Cheers, Alex


Good insights, but I have a few minor quibbles.

A 16" AP shell would be unlikely to explode on contact with the water. It would arm the fuze and explode .035 seconds later. That might do significant damage to the ship, depending on where it hit. If it travelled a short distance underwater and then passed through armor before exploding, it would probably not be seen by washington as a hit. I imagine most hits are seen by the bright flash caused by kinetic enerygy of impact and the actual explosion behind armor wouldn't be seen. I get this from my experience with tank gunnery where we would fire sabot at old tank hulks and even though there was no explosive involved there would be a flash on impact easily seen in bright sunlight.


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