Bismarck class turret protection

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Re: Bismarck class turret protection

Postby Bgile » Wed Jun 25, 2008 3:43 pm

dahlhorse wrote:One thing people fail to recognize and come to terms with is that no other battleship when surrounded by enemy forces and unable to steer with speed reduced to 5 to 7 knots in strong headwind with crew exhausted would have been able to take the pounding the great Bismarck took at close ranges for naval warfare; everyone seems to think that the rodney or the POW or KGV or iowa or any other class battleship have better armour or better guns or better this and better that. It is all nonsense; come to one conclusion in your heads and do not forget it; The Bismarck took one hell of a ganging up on and pounding and still had to be scuttled by "His" crew to send it below the surface; NO other battleship would have been able to take that pounding from all angles and then have to be scuttled to end it.The Bismarck would still pummel any battleship then or now one on one; If it was matched up with the same radar technology and sensors of modern day. END OF STORY


Just curious ... do you think we should all put "come to one conclusion in your heads and do not forget it" and "END OF STORY" in our arguments? Is that what makes them correct?

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Re: Bismarck class turret protection

Postby lwd » Wed Jun 25, 2008 4:33 pm

This looks like arguemnet by fiat. Combined with a number of falacies.
dahlhorse wrote:One thing people fail to recognize and come to terms with is that no other battleship when surrounded by enemy forces and unable to steer with speed reduced to 5 to 7 knots in strong headwind with crew exhausted would have been able to take the pounding the great Bismarck took at close ranges for naval warfare;

Some of this is not clear but it's an open question as to whether or not several other BBs could have taken the damage handed out and been in as good or better shape afterwards.
everyone seems to think that the rodney or the POW or KGV or iowa or any other class battleship have better armour or better guns or better this and better that. It is all nonsense;

Why is it nosense? It is for the most part based on numbers and facts. It's debated becasuse there are different interpretations to some of those but it's hardly nocnsense.
come to one conclusion in your heads and do not forget it;

Who made you the ultimate authoraty on this?
The Bismarck took one hell of a ganging up on and pounding

I don't think anyone has debated this.
and still had to be scuttled by "His" crew to send it below the surface;

It's pretty clear that she was in sinking condition and the scuttling was hardly required. Indeed some on this board have suggested that it may actually have prolonged her time above the surface.
NO other battleship would have been able to take that pounding from all angles and then have to be scuttled to end it.

Conjecture unsupported by any analysis or fact. For instance put the Musahi in her place and she might still have been fighting
The Bismarck would still pummel any battleship then or now one on one; If it was matched up with the same radar technology and sensors of modern day.

Conjecture again unsuported by analyisis or fact. Indeed when examined in the light of some facts it is highly debatable. Even with the radar/technology equivalant ships like the Yamato, Musahi, Iowa, North Carolina, South Dakota, etc were capable of dishing out more weight of fire especially at longer ranges with better chances of penetrating than Bismark.
END OF STORY


Substitute fairy tale for story and that's about right.

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Re: Bismarck class turret protection

Postby Karl Heidenreich » Thu Jun 26, 2008 1:11 am

I don´t really know where is this taking all of us. Because of posts like the ones of dahlhorse many other previous discussions lost their sense and a lot many work trying to stand some ground battered.

This issue about Bismarck´s "construction flaws" had been discussed a lot before and have been the ground of very acid fights (fights in which I don´t want to be dragged again), and no certain answer have been reached.

I only have to say this: many, if no almost all, of Bismarck´s "flaws" are known to us because in combat they were relevant. Many consider that the three propeller arragement of Bismarck and rudder distribution are a "flaw" because of the Swordfish lucky hit. We know for a fact something happened there because of that design under those circumstances. What if Hood, PoW, Yamato or Iowa falled victim of such a lucky hit? Would they have behaved better? Or worse? We don´t know because that didn´t happened to them. Bismarck´s turret armor was not ideal? Such as what? Missouri´s? DoY´s? Nagato´s? How many BBs in WW2 did suffer the barrage Bismarck did on May 27th? How many were hit at their turrets? How many times?

Why we don´t speak, instead, of PoW´s flaws when sunk by "just" an airborne attack on December 1941? Or Repulse´s flaws? Why we don´t refer to South Dak´s superb wiring at Guadalcanal? South Dak was lucky because she wasn´t facing Yamato instead of aging Kirishima.

Again: Bismarck´s "flaws" are like those of Titanic. We know their problems because, historically, they fall victim of some phenomena. Other vessels, maybe, had the same or worse "flaws" and we will never know because they never hit an iceberg or were surrounded by a whole fleet whist doing 7 knots and unable to steer.

Well, this is not a fighting issue. I don´t back up dahlhorse´s ballistic opinions but neither the "ultranza" anti Bismarck position.

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Re: Bismarck class turret protection

Postby Bgile » Thu Jun 26, 2008 2:35 am

Karl Heidenreich wrote:Why we don´t speak, instead, of PoW´s flaws when sunk by "just" an airborne attack on December 1941? Or Repulse´s flaws? Why we don´t refer to South Dak´s superb wiring at Guadalcanal? South Dak was lucky because she wasn´t facing Yamato instead of aging Kirishima.


Ummm ... we DO speak of those things, Karl. At great length.

But you make some good points.

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Re: Bismarck class turret protection

Postby RF » Thu Jun 26, 2008 8:30 am

Unlike some people I don't have a set view on the Bismarck, good or bad, or indeed on any other ship. I think the majority of the members of this forum lean this way also. But there are some rather narrow minded and tunnel vision views around and I think they should be allowed to be expressed so that they can be challenged and exposed as shallow thinking, as lwd has shown us above.
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Re: Bismarck class turret protection

Postby Bgile » Thu Jun 26, 2008 6:00 pm

I just reread this whole thread and was reminded that it was a very interesting discussion right up until June 12. Some good info in there.

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Re: Bismarck class turret protection

Postby yellowtail3 » Fri Nov 13, 2009 2:34 pm

dahlhorse wrote:One thing people fail to recognize and come to terms with is that no other battleship when surrounded by enemy forces and unable to steer with speed reduced to 5 to 7 knots in strong headwind with crew exhausted would have been able to take the pounding the great Bismarck took at close ranges for naval warfare... NO other battleship would have been able to take that pounding from all angles ... The Bismarck would still pummel any battleship then or now one on one... END OF STORY

heh heh heh heh. Silly.
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Re: Bismarck class turret protection

Postby delcyros » Wed Apr 17, 2013 2:33 pm

BISMARCK turret protection reconsidered.

Disclaimer.
Following a hint of Herr Nielsson that the turret faceplate appears to be the only element protected by face hardened armour of the revolving structure of the turret (the similarely face hardened KC/n.A. plates of the barbettes are fixed to the ship´s structure), I once more looked into GKdos-100 curves kindly provided to me by Thorsten Wahl to approach the rational behind the turret protection. I´d take opportunity to thank them providing me valuable information.

Introduction.
Previously, I took it as granted that the slope plates are made of KC/n.A. and not homogenious, full armour grade materials (Wh./n.A.), though altough this notion maybe found in various secondary sources, this is not reflected by support frm primary sources. Parts of these questions have been dealt with in Nathan Okun´s influential article "ARMOR PROTECTION OF THE BATTLESHIP KM BISMARCK" (9/6/1991) to be found here:
http://www.combinedfleet.com/okun_biz.htm
However, several aspects leave a lot to be desired.

"The rotating turrets are also slightly lighter in armor than the average foreign designs with 14.17" (360 mm) KC n/A near-vertical faces (port plates), 8.66" (220 mm) KC n/A vertical sides, and 12.6" (320 mm) KC n/A backs (this thicker back is due to it being used as a counterweight for the gun barrels to balance the turret). Most foreign designs used heavier faces except for the British HMS KING GEORGE V Class which used smaller 14" (356 mm) guns and only 12.75" (324 mm) CA faces (the lower scaling effects of thin-faced British CA partially offset this slightly low face thickness).
(...)
Turret roofs on the BISMARCK were of the unique standard German WWI pattern, being "faceted," with a central flat rectangular 7" (180 mm) Wh region raised up above the upper edge of the turret sides and connected to the sides using prism-shaped 7" Wh sloped plates on the sides and front. This raised the roof of the turrets a couple of feet without having to increase the height of the heavy side and face armor and thus this design lowered the weight of the turrets. Most foreign contemporaries had turret roofs of that thickness or greater that were flat or slightly sloped to the sides or fore-to-back. However, the BISMARCK's steeply sloped roof edge plates were much less oblique than the flat central roof and were not increased in thickness to compensate. To me, that makes them weak spots in the turret; they should have been thickened to at least 9" (229 mm) or, if not, at least the front sloped plate should have been sloped at a much shallower angle, as it was the one most likely to be hit by the enemy that the turret was shooting at.
"
-Nathan Okun (1991), see above for reference

A number of updates appear to be necessary in order to bring that part of the article to the present state of knowledge:
[A] the central flat portion of the turret is not 180mm Wh but only 130mm Wh
[B] the degree of the sloped part of the turret is determinable to 66 to 68 deg (depending on the detailed plan from which the measurement is taken, I use therefore 67 deg herewith as a working prelimiary)
[C] the 360mm thick frontal plate is leaned back 8declined by between 8 an 10 deg (again, depending on sources, using 9 degs herewith)
[D] there is no evidence to suggest that the thick side- or back plates of the turret are similarely made from face hardened KC derivates as the turret face.
It does also require an analysis in order to allow for a conclusion that there is a weak spot with regard to which thickness which is required to allow protection from BISMARCK´s own guns at certain distances.


I. Barbette and turret faces:

Thus, the Elements of face hardened armour (KC/n.A.) appear to be the ~9 deg declined 360mm turret faceplate and the 340mm vertical but rounded barbette plates, while homogenious armour appears to cover other areas of the turret such as the 180mm thick frontal and back slopes (67 deg declined), flat turret roof (130mm) and turret back.

Image

In order to determine the protection of these areas, these surfaces are to be compared against the 38cm L4.4 800kg APC fired from the SK C/34e housing in these turrets. I am aware that this is a very artificial comparison. The penetration curves and ballistic data are taken from "Unterlagen zur Bestimmung der Hauptkampfentfernung und Geschoßwahl, Heft h" with reference to individual penetration charts for homogenious armour (drawing 5 AKB 9259), face hardened armour (5 AKB 9214) and ballistic curves (5 AKB 1861a).
The individual points for striking velocity and impact obliquity (adjusted for angle of fall and decline of the plate) can be plotted against the penetration curves for face hardened armour. One has to keep in mind that turrets are exposed and even a partial penetration can have catastrophic effects due to driven in hot fragments of the projectile or plate, even without high order detonation. I therefore feel justified to use the (black) penetration curves for "grenz" penetration, which is sometimes incorrectly called "broken". The definition for "grenz" is dependent entirely on the complete depletion of the striking energy during the penetration process, thus the whole projectile is expected to pass the plate but with no remaining residual velocity either intact or broken. One has to reckon that in conditions of high or medium obliquity, this would likely cause the projectile to break but it´s not necessary for the projectile to be ineffective, it´s only necessary to deplete it´s energy to attain this definition. Thus, in terms of US terminology, this definition touches "partial penetration", "NBL" and "EEF", altogether but is closer to the US Naval Ballistic Limit than any else.

Image

From the penetration curves in GKdos-100 it appears that the slightly declined turret face is vulnerable to BISMARCK´s own guns out to 300hm / 32,820 yard to penetration in "grenz" conditon. This is a very long range by any standarts but one may easily see that even a 18.1 inches or 460mm KC/n.A. plate -installed the same way as in BISMARCK´s turrets- would not have provided ballistic protection against the 380mm L4.4 APC at likely battle range of 200hm (21,880 yard). In order to provide ballistic protection at 150hm a plate similarely thick as SHINANO´s famous turret faceplate would be required and the weight for it -together with the balancing turret back plate may have been prohibitive in this case from the point of view of topweight and stability considerations.
The barbette plates, albeit vertical, allow protection from 270hm and larger (roughly 30,000 yard) for centre barbette impacts (no horizontal angle involved). Again, this appears to be a very large distance with very little immunity provided.

II. Horizontal armour protection of the turret.

Homogenious armour is -unlike face hardened armour- in general not able to damage the L4.4 Psgr APC projectile, at least for the range of thicknesses (to 200mm plates) referred to in the penetration graphs. Thus, a penetration at "grenz" is always also an effective penetration with the projectile capable of penetrating high order behind the plate. In this case, the "grenz" curves are identic to the "US effective ballistic limit". It should also be noted that, because the projectile impacts with windscreen and armour piercing cap attached, the GKDos-100 penetration curves are valid. They also assume a fully intact projectile impact with all nose coverings and caps in place.
The flat roof plates (130mm Wh) and the sloped parts (180mm Wh) have been plotted against the penetration curves for homogenious armour and the speific impact conditions caused by striking velocity, angle of fall and decline of plate:

Image

As can be seen in this plot, the sloped parts of the turret are not -as has been claimed- vulnerable at short or medium distances to penetration. It requires a minimum distance of 230 to 240hm (roughly 26,000 yard) to allow a penetration according to GKdos-100 curves. The flat 130mm Wh roof is vulnerable to penetration only at extreme range, ca. 300hm, which is coincidently the same range which we have seen where the penetration through the face hardened turret front ceases to be possible.

III. Results.
It appears that the statement that there "is no classical immune zone for BISMARCK´s turrets" still holds true in light of the faces vulnerability not ceasing before ~33,000 yard, while the vulnerability of the flat turret roof appears right there and that of the 180mm turret slopes already earlier at 26,000 yard.
Still, not every plate of a turret is vulnerable to ballistic penetration at any range. Hits impacting the turret slope or roof plate at, say 25,000 yard likely will not get through while impacts on the barbette or turret face at extreme range equally have little chance to be successful.
The possible impact trajectories are plotted below.

Image

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Re: Bismarck class turret protection

Postby Dave Saxton » Wed Apr 17, 2013 3:40 pm

Thanks delcros,

I have done similar exercises and came to the same results for the homogenous armour sections. At ranges beyond 200hm these sections are more likely to be hit than the face plate. The face plate is most likely to be hit at shorter ranges but as you point out even 460mm plate will still not be proof.

I came to a battle range less than 30km for the face plate using intact penetration as the definition. Hoyer points out that intact penetration was the limit used in all calculations by the designers. As I recall it still is vulnerable to penetration beyond 200km, but I also got to looking into the curvature of the plate.

It is not flat. (Obviously the barbets are curved as well.) British designs seem to be taking into account curved face plates as well. Modern literature clearly point out that a curved plate increases the necessary velocity compared to the same plate thickness if flat. Also USN interwar literature provide for the effect of curved plate. I don't recall the exact math but the USN formula takes into account the secant angle on the total obliquity. This way I found the face plate is viable closer to about 200hm -for full intact penetration.

The 9* angle back seems puzzling until one considers the possible shattering velocity of many AP shells striking face hardened armour, even if still capped. At shorter ranges the striking velocity can be very great and that additional striking angle at short ranges can make a difference, possibly causing shatter in these cases where not enough amour can be used anyway. This is especially the case of smaller caliber shells (perhaps with soft or relatively small caps) which may strike with very high velocity at shorter ranges, thereby making the turret more vulnerable to smaller caliber fire as well as larger caliber fire. Velocity is a prime factor of penetrating face hardened armour. The angle of the upper Wh plate also makes some sense in these cases as well.
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Re: Bismarck class turret protection

Postby tommy303 » Wed Apr 17, 2013 5:42 pm

. . . all of which seems to confirm what the Germans already suspected, that in the armour versus gun race, as metalurgy stood in the the 1930s, the gun had won, particularly when a designer is forced to use an orthodox, single plate thickness for protection.

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Re: Bismarck class turret protection

Postby delcyros » Wed Apr 17, 2013 6:41 pm

While the previous attempt can be regarded as fairly constructive and save, extrapolation to other data appears to be more difficult. Using the 16in US class A turret faceplate of the NORTH CAROLINA class as an example, the penetraion curves suggest that the plate is likely to be penetrated at all distances by the SK38 C/34e firing the L4.4 Psgr.

The declination (=leaning backwards) of the turret faceplate makes penetration at long range even more feasable than in BISMARCK´s case because the angle of fall increases and the impact obliquity correspondingly reduces with range. If You assume that GKdos-100 penetration curves are representative for penetration performances of face hardened armour, and if You further assume that KC/n.A. and US class A are similar but slightly different in stopping quality as evidenced by shooting trials carried out in the USNPG Dahlgren in 1946, suggesting a figure of merit in between 1.055 and 1.083 in favour of KC/n.A when attacked by US 14" APC (less than that when attacked by 12in and 8in and likely more than that when attacked by 16in, -though untested- due to scaling). The choosen figure of merit is possibly conservative because the average US class A in 1946 was ca. 2.5% better in stopping power than pre-1944 manufactured US class A according to Revision "J". Since all of NORTH CAROLINA´s class A plates were manufactured before Revision "J" was issued, we should therefore take an 2.5% lower average stopping power into account. This would translate to a figure of merit against 14in projectile of +8% or +11% for the two KC/n.A. plates tested 1946 in the USNPG Dahlgren. The definition of penetration in this case is the US NBL. We can safely assume that US thick chill class A armour induces even more projectile damage than german KC/n.A., thus while the NBL is lower, the EEF should be higher. I therefore estimate that 380mm KC/n.A. plate are comparable in "grenz" penetration to a generic 16 inches US class A plate manufactured in the late 30´s + it´s STS backing plate as far as complete penetration (but not necessarely penetration in effective bursting condition...) is concerned.
Assuming further the turret faceplate was declined 42 degrees (measured by myselfe -EDIT: actual inclination of the turret faces of the similarely laid out SOUTH DAKOTA´s 16"/45 triple turret was 40.9 deg according to builders drawings, see Warships International Vol. 43, issue 4, p.414f) then You can plot the coordingates of striking velocity and impact obliquity for various ranges and compare them with the ballistic limit velocities for various thicknesses KC/n.A. as has been described previously:

Image


The interpretation of this comparison may support the idea that NC´s 16in 42(?) deg declined class A faceplates -at least in theory- are not excluding full penetration at virtually all ranges by 38cm L4.4 Psgr. fired from 38cmSK C34, resulting in similar non existing immune zone for the turrets in case of NORTH CAROLINA. Thoddy already outlined critiques to this approach. One may add to the variances of projectile and plate quality the distance of the hole to the corner of the plate (note cutouts for gun barrels, too in this context) or that the edges of turret faceplates were wrapped in aspest and correspondingly had no face hardening applied. Finally, it may be questioned that the L4.4 Psgr does indeed penetrate as well as the US 14in Mark 16 mod 8 did.

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Re: Bismarck class turret protection

Postby alecsandros » Thu Apr 18, 2013 5:26 am

Turret geometry would be another factor.
Bismarck's turret shape has most facets of all known battleships , thus making compounded impact obliquity of a shell more unfavorable for any kind of penetration (intact or otherwise)

=====

If it weren't for the 13cm thin armored roof, these would be superb turrets.
But the 13cm plate can easily be perforated by any kind of AP and even some SAP bombs.
Vulnerability to British 15"/L42 and US 16"/L45 between 22-27km should also be noted.

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Re: Bismarck class turret protection

Postby Dave Saxton » Thu Apr 18, 2013 1:59 pm

alecsandros wrote:
If it weren't for the 13cm thin armored roof, these would be superb turrets.
But the 13cm plate can easily be perforated by any kind of AP and even some SAP bombs.
Vulnerability to British 15"/L42 and US 16"/L45 between 22-27km should also be noted.

The 13cm roofs are fine. 13cm horizontal armour is good to 300hm battle range. Past that battle range the penetration increases expotentially so that 6" or 7" ...will only buy marginal increases in IZ. And its not just against the German 15" guns. In firing range tests post war, none of the British BB guns could defeat more than about 5" deck armour at less than 32,000 yards. TP's Bruno turret roof survived a direct SAP bomb hit.

Turret geometry would be another factor.
Bismarck's turret shape has most facets of all known battleships , thus making compounded impact obliquity of a shell more unfavorable for any kind of penetration (intact or otherwise)


A good question is why others, such as the British, used ~13" turret faces.
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Re: Bismarck class turret protection

Postby alecsandros » Fri Apr 19, 2013 5:52 am

Dave Saxton wrote:The 13cm roofs are fine. 13cm horizontal armour is good to 300hm battle range. Past that battle range the penetration increases expotentially so that 6" or 7" ...will only buy marginal increases in IZ. And its not just against the German 15" guns. In firing range tests post war, none of the British BB guns could defeat more than about 5" deck armour at less than 32,000 yards. TP's Bruno turret roof survived a direct SAP bomb hit.

It's hard to say, Dave.
From the penetration curves that I've seen, the British 15"/L42 and US 16"/L45 could perforate over 13cm of armor at 22km and beyond.
EDIT: as the hit on Dunkerque's turret roof showed, complete penetration is not needed at all to kill everybody inside the turret and to cause massive damage...

Other guns , with higher m-v, tended to have much less horizontal penetration at medium range.

Turret geometry would be another factor.
Bismarck's turret shape has most facets of all known battleships , thus making compounded impact obliquity of a shell more unfavorable for any kind of penetration (intact or otherwise)


A good question is why others, such as the British, used ~13" turret faces.[/quote]

?
Do you mean why did they used such thin plates ?

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Re: Bismarck class turret protection

Postby delcyros » Fri Apr 19, 2013 9:36 am

The KGV´s turret faceplate was 520lbs CA, that´s 12.74" face hardened armour. LION´s were supposed to be 600lbs or 14.7" CA..- Thus, KGV´s vertical turret face elements -if we assume a 10% quality advantage for british CA against KC/n.A.- are roughly similar in protection than a 356mm KC/n.A. plate but vertical and thus cannot be penetrated much in excess of 255hm, somehow better than BISMARCK´s arrangement.
There is evidence to suggest that even unpenetrated, every major calibre impact will knock out a turret (half a t. or heavier projectiles impacting at velocities faster than the speed of sound will most certainly kick some sensible equipment inside the turret out of alignment even if they dn´t penetrate) but DUNKERQUE´s case is unique as they employed face hardened armour on the flat turret roofs, which would be ideal for breaking up GP, SAP and AP bombs but are less desirable for the thread actually faced by this vessel, the impact of high velocity capped AP striking obliquily. Face hardened armour doesn´t flex or deform plastically in this condition before it starts to break and fracture.

The US 16"/45 mark 8 (COLORADO class) according to it´s 1942 issued penetration curves will penetrate 121mm homogenious armour at 25,000 yard.
The US 16"/50 mark 7 (IOWA class) according to Garzke referring to penetration curves for 2700lbs AP is expected to penetrate 131mm homogenious armour at 25,000 yard.

Heavier armour for turret protection may have been desirable, but then again, this would have compromised topweights and stability, the naval architects had to balance tradeoffs and I guess that the achievement of a relatively extreme metacentric stability may have had a higher priority in light of the low Panzerdeck scheme adopted to protect the embedded vitals of this vessel.


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