Bismarck vs. Rodney: hand to hand?

[Dave Saxton]

What is the actual striking angle and velocity at a given range-and what is required? The face plate is not vertical but sloped back about 12*. It is also curved and the radius in this case requires approximately 12% more velocity than if it was flat. In cases of KC it's mainly a matter of velocity among large caliber projectiles of similar caliber. The exposed barbet is 13.4" (340mm), not 12". It is of course round, which requires more V than a flat section of plate of equal thickness. Required velocity and striking angle is the correct way of examining this.

These principles are why we find the British battleships with seemingly thin barbet and turret face thickness as well. For example, Vanguard had a 330mm curved face plate and 330mm barbet. KGV had a 324mm flat front face plate -although it is also declined. KGV's barbets are 330mm. Littorio had 350mm face plates and barbets.

[Bgile]

What is the actual striking angle and velocity at a given range-and what is required? The face plate is not vertical but sloped back about 12*. It is also curved and the radius in this case requires approximately 12% more velocity than if it was flat. In cases of KC it's mainly a matter of velocity among large caliber projectiles of similar caliber. The exposed barbet is 13.4" (340mm), not 12". It is of course round, which requires more V than a flat section of plate of equal thickness. Required velocity and striking angle is the correct way of examining this.

These principles are why we find the British battleships with seemingly thin barbet and turret face thickness as well. For example, Vanguard had a 330mm curved face plate and 330mm barbet. KGV had a 324mm flat front face plate -although it is also declined. KGV's barbets are 330mm. Littorio had 350mm face plates and barbets.

I didn't realize Bismarck's barbette was that thick, and I stand corrected. That makes them less vulnerable than I'd thought. The Bismarck's faceplate looks flat. It can't be curved very much, because it looks flat in photos. Where do you get the 12 percent benefit? That is certainly significant if it's that much.

And then we have the US ships with very thick turret armor, as well as Yamato. How about Jean Bart? I don't have the French ships info available to me.

Why do you consider a 12 deg slope to be good? Doesn't that just mean incoming shells hit it closer to normal, so penetration would be greater than with a vertical plate, not less?

There are experts who say the 180mm angled faceplate is a weakness, but you think otherwise apparently. Why is that?

I guess I'm going to have to dig out the penetration formulas ... which is like going to the dentist ... but I don't think the ones I've seen take curvature into consideration, just angle.

You are saying that all BB shells are equal, and velocity and striking angle are the only important things wrt to penetration. That isn't borne out in the ballistics tables at all.

[alecsandros]

Guys, I just had a thought: from what I know, in WW2, all the hits on the barbettes/turrets caused the respective turrets to be knocked out of action, if not destroyed.

So, with regards to our discussion, I would say a 380mm hit on Rodney and a 406mm hit on BS's turrets would most likely take them out, at any normal battle ranges.

The historical examples that I know:

- Hood hits the Dunkerque in 1940 on the roof top of a turret. Although it doesn't penetrates entirely, the turret is out of action.
- Rodney hits the BS at about 15km, taking out 2 turrets at once.
- KGV hits the BS at close range - 4-8km - on the face plate of turret Caesar. The shell fails to penetrate, but the concusion takes the guns out of action.
- Massachussets hits Jean Bart's barbette in 1942, causing a large splinter to jam the turret's train, causing it to seize fire.
- Kirishima hits the South Dakota in 1942 on the barbette, causing it to train much slowly.

Note: I don't have my books here, so I'm writing everything from memory. I may be wrong with some of the damage, but I hope you get my point: a 14"+ hit on a battleship main armament is very likely to knock out the respective turret.

[RF]

a 14"+ hit on a battleship main armament is very likely to knock out the respective turret.

Which essentially highlights the point about accuracy of shooting and rate of fire.

[lwd]

Guys, I just had a thought: from what I know, in WW2, all the hits on the barbettes/turrets caused the respective turrets to be knocked out of action, if not destroyed.
....

I believe SoDak's turret was not put out of action by the 14" hit on her barbette.

[Bgile]

Guys, I just had a thought: from what I know, in WW2, all the hits on the barbettes/turrets caused the respective turrets to be knocked out of action, if not destroyed.

So, with regards to our discussion, I would say a 380mm hit on Rodney and a 406mm hit on BS's turrets would most likely take them out, at any normal battle ranges.

The historical examples that I know:

- Hood hits the Dunkerque in 1940 on the roof top of a turret. Although it doesn't penetrates entirely, the turret is out of action.

There was a hole in the turret top, and of course it was out of action. It killed the crew in that part of the turret. I believe only half the turret was out of action, though. The French used cemented armor on the turret tops of that class ... a mistake not made by other navies. Again, a penetration.

- Rodney hits the BS at about 15km, taking out 2 turrets at once.

That's really short range, so of course. I think something must have penetrated to take out two turrets, but I don't think anyone knows what happened. It's hard for me to imagine what kind of hit would do that. What makes you think that was a non-penetrating hit?

- KGV hits the BS at close range - 4-8km - on the face plate of turret Caesar. The shell fails to penetrate, but the concusion takes the guns out of action.

No one would expect a turret to survive a hit at that range.

- Massachussets hits Jean Bart's barbette in 1942, causing a large splinter to jam the turret's train, causing it to seize fire.

A freak hit where the shell glanced off the side of the turret and hit the top of the barbette where the turret joins it and put a dent where it would jam it until it could be cut free.

- Kirishima hits the South Dakota in 1942 on the barbette, causing it to train much slowly.

Turret still in action.

Note: I don't have my books here, so I'm writing everything from memory. I may be wrong with some of the damage, but I hope you get my point: a 14"+ hit on a battleship main armament is very likely to knock out the respective turret.

Testing was done, and the respective navies felt the heavy armor was worthwhile. Otherwise they'd just have armored against cruiser fire and saved a lot of weight. Boise had a turret hit on a 6" turret faceplate by an 8" AP which didn't affect it's operation. There aren't a lot of turret hit examples on ships. Tanks took turret hits all the time which didn't put the turret out of action. Some did, some didn't. The examples you gave which took the turret out of action seem to have been penetrating hits, but I don't dispute the fact that at least some non penetrating hits would disable the turret, but not all.

[lwd]

Washington apparently hit Kirishima's main armamanet a number of times and does appear to have taken it out but at the ranges involved the US AP round could even be considered overkill vs her armor.
As for the hit on Bismarck one of the turret's did fire again from what I remember reading although it may have just been the round "cooking off". Could Rodneys hit have taken out power to the turrets?

[Dave Saxton]

You are saying that all BB shells are equal, and velocity and striking angle are the only important things wrt to penetration. That isn't borne out in the ballistics tables at all

I'm not saying they are exactly equal but the effect of weight and slight differences in diameter is minor compared to velocity (also the head shape and hardness gradient) when attacking vertical FH armour. Nathan has talked to this factor on these forums:

Also, shell weight does not matter very much as to penetration of face-hardened armor (it is only to the 0.2 power), though full weight effects occur against homogeneous armor. The homogeneous armor gives way slowly and the entire projectile momentum has time to get involved in punching a hole. Thus, projectile weight and the square of the velocity can be seen to balance the complete kinetic energy required to penetrate (a heavy projectile has a lower striking velocity to penetrate in accordance with the conservation of energy of the entire plate and projectile).

Face-hardened armor, however, is rigid and does not give until the force gets too great to resist, at which point the hard face caves in suddenly and the pressure can then tear through the soft, ductile rear of the armor. Usually, the face breaks prior to the full weight of the projectile getting involved -- the impact shockwave that reflects and cracks the plate face layer involves only the projectile nose and by the time the shockwave in the projectile reaches the lower body of the projectile, allowing that lower body to get involved in the penetration process, the face has already either broken, allowing penetration to proceed, or it hasn't and the rest of the projectile's weight is not going to help. Only in a narrow range of striking velocities does the full projectile weight get involved at all and this is where the projectile barely penetrates the ductile back layer after the face layer has cracked open, so hitting above this velocity renders the full projectile weight of no consequence. If the plate were hard all the way through, projectile weight would mean even less, once a minimum is reached.

This is why the use of 2700-lb 16" shells (US final Mark 8 AP design) does not buy you much compared to 2100-lb 16" shells (WWI Mark 3 AP design) -- a 29% weight increase -- against the same face-hardened armor plate, assuming equal damage to both projectiles from the impact. You only can reduce the impact velocity with the heavy shell here to 94% of what you need for the light shell; hardly worth the effort to make the heavy shell here.

It can't be curved very much, because it looks flat in photos. Where do you get the 12 percent benefit? That is certainly significant if it's that much.

I have studied this in depth and it is more curved than it looks. In several US ballistics studies the effect of impacting curved plates is presented, although well beyond the scope of this post they indicate a 12% increase in Vnot. Another way to look at is that the curve in this case creates the eqivilent of striking 17* yawed.

Why do you consider a 12 deg slope to be good? Doesn't that just mean incoming shells hit it closer to normal, so penetration would be greater than with a vertical plate, not less?

A 12* angle of fall occurs at ranges of less than 18,000 meters in most cases, which means that at lesser ranges than 18km the shell is striking slightly obliquely when it's velocity is extremely high, possibly within the shatter zone for a capped shell. At greater ranges than about 18km the obliquity is once again increasing as the velocity is decreasing, bringing it into play at the ranges beyond about 20km.

There are experts who say the 180mm angled faceplate is a weakness, but you think otherwise apparently. Why is that?

If you apply the velocity and actual striking angles per range of the 38cm to the homogenous armour curves you will find that the result stays outside of the 180mm curve at all ranges of less than about 23km.

And then we have the US ships with very thick turret armor, as well as Yamato. How about Jean Bart? I don't have the French ships info available to me.

The US engineers had to compensate for the use of homogenous plates, because the original planned Class A plates were found not up to the task. The Class B plates were also known to be slightly sub par when used for very thick plates, which required compensation. The French probably rightly considered that they should have an additional safty margin with all their firepower concentrated in only two turrets forward. However, employing more armour tonnage than absolutely needed is rather poor engineering from a weights efficiency perspective.

[Dave Saxton]

Washington apparently hit Kirishima's main armamanet a number of times and does appear to have taken it out but at the ranges involved the US AP round could even be considered overkill vs her armor.
As for the hit on Bismarck one of the turret's did fire again from what I remember reading although it may have just been the round "cooking off". Could Rodneys hit have taken out power to the turrets?

The historical Rodney hit occured at a range where it would have exceeded 500M/s impact velocity and at less than 16* from the normal. Of course we will never know exactly what happened.

[alecsandros]

I'm back home, with my books

... The examples you gave which took the turret out of action seem to have been penetrating hits, but I don't dispute the fact that at least some non penetrating hits would disable the turret, but not all.

I said "very likely to knock out the respective turret". I did not say "surely"; it's no sure thing.
Just that in the historical engagements I read about, the heavy shells hits generaly disabled the mounted turret. The only exception is the SoDak, which anyway had a slower training speed after the hit (so it wasn't undamaged). but SoDak had a 410mm barbette, which received a 356mm shell from probably the worst 356mm gun used in the WW2 (although, admitedly, at close range). AND there still is that old point of view that the Kirishima hadn't switched to AP rounds, but used incendiary or HE shells over the SoDak... (although damage analysis tells a different story)

@ Lwd: Yes, I have forgotten about Washington's deluge of fire over the Kirishima. But anyway, the MkVI shells were expected to cut through armor like knives through butter, and at 7.5km... It was clear that any hit on any turret would blast it out...

About Rodney's hit on the fw turrets: from "Hunting the Bismarck", it would seem that the shell exploded against turret Anton and "fragments damaged turret Bruno, and killed almost all personal on the exposed part of the bridge". Minutes later, the Norfolk transmitted that "the guns from the fw turrets are up in the air, probably knocked out". So, none of the turrets was destroyed, and the guns were still fixed in their hoists, which denies a frontal penetration/explosion...

KGV's hit on turret Caesar is worthy of notice, because the shell failed to penetrate the turret-face, and also did not explode. It was glanced off into the sea. However, "the concussion damaged the elevation mechanism of the left gun".

[Bgile]

I don't think there is much doubt that a heavy shell hit on one of these turrets could disable it. It's just that I don't think we have a large enough data set to get a good idea of how likely it was.

[Thorsten Wahl]

Nathan Okun's table indicates Rodney's guns will penetrate 14" of German KC out to about 30,000 yds, and the Barbette is only 12".

The problem is the british data from facehard seems to be questionable

The british own armor efficiency diagrams are showing possible penetration of 13" at a distance of 17000 yards. (This value seems to me very little).
Navweaps predicts according USN Empirical Formula for Armor Penetration 12,2" at 20000 yards and 8,8" at 30000 yards
http://www.navweaps.com/Weapons/WNBR_16-45_mk1.htm
This is quite a huge difference to 14" at 30000 yards

In comparison with other guns (especially with the german SK 38) the amount of pentration calculated by facehard is not plausible in my opinion

[Bgile]

Nathan Okun's table indicates Rodney's guns will penetrate 14" of German KC out to about 30,000 yds, and the Barbette is only 12".

The problem is the british data from facehard seems to be questionable

The british own armor efficiency diagrams are showing possible penetration of 13" at a distance of 17000 yards. (This value seems to me very little).
Navweaps predicts according USN Empirical Formula for Armor Penetration 12,2" at 20000 yards and 8,8" at 30000 yards
http://www.navweaps.com/Weapons/WNBR_16-45_mk1.htm
This is quite a huge difference to 14" at 30000 yards

In comparison with other guns (especially with the german SK 38) the amount of pentration calculated by facehard is not plausible in my opinion

It does seem rather high.

[dunmunro]

Nathan Okun's table indicates Rodney's guns will penetrate 14" of German KC out to about 30,000 yds, and the Barbette is only 12".

The problem is the british data from facehard seems to be questionable

The british own armor efficiency diagrams are showing possible penetration of 13" at a distance of 17000 yards. (This value seems to me very little).
Navweaps predicts according USN Empirical Formula for Armor Penetration 12,2" at 20000 yards and 8,8" at 30000 yards
http://www.navweaps.com/Weapons/WNBR_16-45_mk1.htm
This is quite a huge difference to 14" at 30000 yards

In comparison with other guns (especially with the german SK 38) the amount of pentration calculated by facehard is not plausible in my opinion

It does seem rather high.

RN proof testing shows the 1590lb 14" projectile piercing 12" of CA @ 30degs at ~1500 fps, (actually as low as 1480fps) and similar results against KM CA:
http://www.panzer-war.com/Naab/Tripitz1.jpg
http://www.panzer-war.com/Naab/Tripitz2.jpg

[alecsandros]

RN proof testing shows the 1590lb 14" projectile piercing 12" of CA @ 30degs at ~1500 fps, (actually as low as 1480fps) and similar results against KM CA:
http://www.panzer-war.com/Naab/Tripitz1.jpg
http://www.panzer-war.com/Naab/Tripitz2.jpg

The discussion was about Rodney's 406mm guns... I also think it's quite high to penetrate 14" of armor at 27km.