BISMARCK armor scheme = BADEN?

[Dave Saxton]

If we follow this logic a step beyond (or back?), then the Rodney 16" is more powerful because it is more likely to remain intact, especially if de-capped, and carries a more destructive warhead. Another step on the logic path reveals that the German L/4.4 at 38cm is deadly indeed. It has an advantage over the Rodney shell through a more effective head shape at typical striking obliquities, and is also more likely to stay intact, especially if de-capped.

[alecsandros]

If we follow this logic a step beyond (or back?), then the Rodney 16" is more powerful because it is more likely to remain intact, especially if de-capped, and carries a more destructive warhead.

That maybe, but not during high obliquity impacts... Where the US shells perform better (they remain intact or in a fit state to burst more often than the British 16")

Another important aspect is projectile mass. Thus, while it's true Rodney's 16" shells were filled with 23kg of TNT, that shell "only" weighed 930kg (with cap). The US shell, filled with 19kg of explosive mix, had a mass of 1225kg (again, with cap).
But, as the shell perforates armor, it usualy loses it's cap, especialy if we're talking about thick FHA. (and we should be talking about it, because with regard to horizontal armor perforation, on high obliquity impacts, the US shell greatly outclasses the British one).

The masses for de-caped projectiles would be:
--816kg mass for Rodney's 16" shells.
--1080kg mass for Iowa's 16" shells.

And it is one thing for a ship to absorb 816kg of molten, exploding, metal, and another to absorb 1080kg... (32% more). Another thing: it is more likely that bigger fragments of shell would be created after the explosion of the US shell, both because it was bigger, and had a smaller explosive filler. And bigger fragments, thrown at ~ 500-600fps, can cause greater damage than smaller fragments at the same velocity.

(The velocities are taken from Nathan's analysis of projectile post-penetration damage)

The German guns, shells, battery arrangement, fire control system and overall ship behavior during a gun battle makes me believe they designed their weapon systems with an emphasis on precision.
("We're going to mount only 8 guns but they will have longer range, more rapid firing cycle and better accuracy than anything the enemy has")
The US and RN, especialy early war, put the emphasis more on saturation...
("We're going to mount as many guns as possible, and as big as possible, onto our battleships. Maybe they won't be very accurate, but one shell would be an important blow...")

Only my opinion...

[Karl Heidenreich]

The US and RN, especialy early war, put the emphasis more on saturation...
("We're going to mount as many guns as possible, and as big as possible, onto our battleships. Maybe they won't be very accurate, but one shell would be an important blow...")

Why is it that this do not surprise a bit.

[Dave Saxton]

That maybe, but not during high obliquity impacts... Where the US shells perform better (they remain intact or in a fit state to burst more often than the British 16")

...

Hi Alex,

How do we know that the British 16" is less likely to penetrate in a state fit to burst than the American 16" during highly oblique impact?

Let's properly connect cause and effect. The British shells were placed at a disadvantage during highly oblique impact because of their head shape not because they were less massive per caliber. Indeed British tests revealed that slightly shorter shells per caliber with larger burster cavities were more likely to penetrate intact than longer ones with smaller bursters. The Rodney 16" was shorter per caliber and less massive per caliber than KGV 14". The 1938 design 15" shell and the KGV 14" were very close in design but the 15" was more likely to penetrate intact. The differences were minor, but with the KGV 14" being slightly longer per caliber and containing a slightly smaller burster cavity.

A smaller burster actually worked against penetrating intact. One interesting comparison is the tests results of both the American 14", which was shorter and less massive, to the KGV 14", which had a larger burster. The American 14" had a blunt head shape, and the British shell had a 1.4 caliber radius. The American 14" had better performance vs decks, despite being less massive overall, but it was also even less likely to remain in fit state to burst.

[Bgile]

I have a serious problem believing the British 16" shell or any other shell would have a better chance to penetrate thick armor intact than the US 16" heavy shell. There would not normally be decapping before impact on this type of armor. The walls are thicker and the whole body of the shell is thicker and more massive and would therefore be more likely to remain intact against a given armor thickness. Shellite is more likely to burst on impact. There is evidence that is exactly what happened to some of Rodney's shells against Bismarck, judging by British observation of visible burst on impact and the failure to penetrate Bismarck's conning tower when ballistics tables would indicate that would happen easily.

I don't see why this comparison can be drawn with the British and US 14" shells because in both cases their design is so much different from the new US 16" shell. It was a radical departure from previous designs by anyone.

I also don't see any indication that anyone sacrificed accuracy for saturation shooting. Why would they do that? The designed their guns to be as accurate as possible, and the US 16" guns seemed to be the most accurate US gun.

[Dave Saxton]

If we restrict the context to perforation of thick armour then we are probably talking about belt penetration by capped shells, not striking accutely oblique. At such obliquity the dynamics of penetration are to plug the armour, and the more massive aft section of the longer body type will drive through the armour better if striking close to the normal. As the obliquity increases it may not prove better at staying intact according to the British tests observations, however.

The Rodney short body per caliber 16" was more likely to remain intact than the longer body per caliber 14" and 15" shells, (all with the same head shape) striking 12" cemented armour 30* from the normal. In this context, velocity factors will be of greater importance to the questions of penetration and remaining intact than factors related to mass. Not only the velocity required for penetration but also the critical velocity for remaining intact will become factors. With the cap, the Vc will be much higher than without the cap. Typically such Vc for capped shells will be above 630 M/s. Hence the shell is more likely to be compromized, even with the protective cap still on, through distortion of the burster and fuze cavity or shatter and so forth, at high impact velocities vs heavy armour, typically enccountered at short battle ranges.

[lwd]

But shell design and composition will also be significant. The US SH shell had a smaller burster cavity which would imply more structural strength.

[Dave Saxton]

How do we explain the observations of AP shells with slightly larger burster cavities being more likely to remain intact?

[lwd]

I'd have to have more info. If it's only slightly more it could be a function of the shape or composition. Perhaps a heat treating effect even. But the US SH has a significantly smaller burster than the British shells and the impication is that the cavity is also.

[Dave Saxton]

But this is among shells of the same composition and treatment regimes, the different factor is the size and depth of the cavities. It is a repeatable result. Even among shells of different composition and treatment a smaller burster resulted in less durability. I know it's counter intuitive but those are the observations.

[Bgile]

But this is among shells of the same composition and treatment regimes, the different factor is the size and depth of the cavities. It is a repeatable result. Even among shells of different composition and treatment a smaller burster resulted in less durability. I know it's counter intuitive but those are the observations.

It's very counterintuitive. The difference is much less than that represented by the US shells, so there could very well have been other factors involved. The whole point of sacrificing the size of the burster cavity was to make the shell body more resistent to breaking up, wasn't it?

[alecsandros]

Hi Alex,

How do we know that the British 16" is less likely to penetrate in a state fit to burst than the American 16" during highly oblique impact?

The British shells were placed at a disadvantage during highly oblique impact because of their head shape not because they were less massive per caliber. Indeed British tests revealed that slightly shorter shells per caliber with larger burster cavities were more likely to penetrate intact than longer ones with smaller bursters. The Rodney 16" was shorter per caliber and less massive per caliber than KGV 14". The 1938 design 15" shell and the KGV 14" were very close in design but the 15" was more likely to penetrate intact. The differences were minor, but with the KGV 14" being slightly longer per caliber and containing a slightly smaller burster cavity.

Hello David!

I feel the discussion is getting to complex for the forum's resources.
There are many other elements to consider besides the ones you already mentioned, such as:

- hardness homogenity for shell bodies
- cap shape, mass and type of joint with the body
- fuze type
- filler composition
- average nutation and precession in-flight and post-penetration
- maybe other aspects ?

All the above elements influence the shell's performance during and after perforating armor plates.
For instance, the British 14" shells had a more unstable filler than the US 14". Thus, in real conditions, in was even less likely to reach the insides of a battleship than the US shell was.

ANother discussion about British 15" shell (mark XXII ? I can't remember the pre-1943 type) which had poorly cast bodies (the hardness, measured on the Brinell scale, varied from top to bottom, quite alot. This made the shell more likely to shatter during impact with armor plates).

Nutation and precession (especialy precession), from what I understand, are slightly higher in-flight for more pointed-tip shells (such as British ones) than they are for more rounded-tip projectiles. And, worse still, N and P are higher in post-penetration trajectories for pointed-tips than for rounded-tip shells. On the other hand, in post-penetration trajectories, the US shells should develop higher nutation, because they were significantly longer (I'm thinking about 16" shells).

So, I don't know how we could arive at a common denominator in this discussion... As the problems are to tangled together...

My impression, for what it's worth, is that US shells had somewhat higher casting quality, had a more stable filler and very tough-hardened caps than the British ones.
Consequently, and especialy considering the behavior of several British shells during several battles, my opinion is that the American ones were more deadly against battleships...

[RF]

Consequently, and especialy considering the behavior of several British shells during several battles, my opinion is that the American ones were more deadly against battleships...

I am inclined to concur with this opinion.

[Karl Heidenreich]

Alex:

Consequently, and especialy considering the behavior of several British shells during several battles, my opinion is that the American ones were more deadly against battleships...

Indeed they are: the number of battleships sunk by the USN's superheavy shells outnumber whatever achievements of the RN.

[Dave Saxton]

I feel the discussion is getting to complex for the forum's resources.
There are many other elements to consider besides the ones you already mentioned, such as:

- hardness homogenity for shell bodies
- cap shape, mass and type of joint with the body
- fuze type
- filler composition
- average nutation and precession in-flight and post-penetration
- maybe other aspects ?

...

Hi Alex,

Proper decremental hardening of the shell's main body is a very important aspect according to Krupp, and becomes vitally important the farther from the head of the main body the center of gravity is. There are at least two different approaches to the heat treatments. One is decremental hardening from tip to base and from outside to center. The is case hardening. If the decremental hardening is too severe the shell will be brittle and be likely to crack or break. Even if it just cracks the detonation will be significantly less effective. If decremental hardening is not enough in terms of hardeness, or decremental depth, then the main body will distort, sometimes severely, as in being turned into a bananna shape or something. Distortion of the main body causes distortion of the filler/fuse cavity to distort as well. Even a minor amount of distortion can be significant. Distortion of the filler cavity can cause a premature detonation of the filler, and distortion of the fuze block usually can result in a dud. Also base slap and the distortion caused thereby is an untractable problem in cases of oblique impact and penetration. In research as to why shells often failed to detonate, the Germans determined that base slap during accutely oblique impact was a primary cause of duds in cases of all AP shells.

It has been found that the cap shape isn't an important factor to penetration dynamics, but the cap's mass is.

The British found that the post penetration rate of precession was slower with more blunt head shapes, and so it took longer for post penetration yaw to become manifest, than with sharper head shapes. This is why the distance between yaw plate and main plate must be sufficient for yaw to become manifest. The rate of nutation is equal to the rate of spin.