15in Up Gunned Gneisenau v 1939 Modernized Renown

[alecsandros]

What armor was sacraficed? My understanding was that the armor they were built with was what was planned. The only difference being the armament was upgraded.

IIRC, their initial armour was designed against their own 356mm guns (initialy proposed). As the turrets were changed, the armor layout stayed the same: a rather thin skin (mainly the belt)...

[Bgile]

What armor was sacraficed? My understanding was that the armor they were built with was what was planned. The only difference being the armament was upgraded.

IIRC, their initial armour was designed against their own 356mm guns (initialy proposed). As the turrets were changed, the armor layout stayed the same: a rather thin skin (mainly the belt)...

what does this have to do with Renown vs Geneisenau?

[lwd]

What armor was sacraficed? My understanding was that the armor they were built with was what was planned. The only difference being the armament was upgraded.

IIRC, their initial armour was designed against their own 356mm guns (initialy proposed). As the turrets were changed, the armor layout stayed the same: a rather thin skin (mainly the belt)...

what does this have to do with Renown vs Geneisenau?

It's a response to Karl's OT side swipe at the US ships. I have a hard time not responding to inaccurate statments even if they are OT.

[Karl Heidenreich]

Bgile:

what does this have to do with Renown vs Geneisenau?

You tell me: you are the one bringing the super heavy issue over and over. So, if you start being off topic don`t come to us saying what our rebutals are off topic.

I still don`t know how the super heavies could save Renown in this...

[Karl Heidenreich]

lwd:

It's a response to Karl's OT side swipe at the US ships. I have a hard time not responding to inaccurate statments even if they are OT.

Lee, my friend, I`m sorry that I have not yet answer your last posts on this because I have a serious hard time today. But if not today it will be in the following days that I will (and you know I will). As I point out to Bgile, I answer OT because the OT was started with the super heavy fallacy. I pointed out, previously, that it is OT. I also pointed out that Bismarck and her Contemporaries thread is the best place to deal with this.

Uhmm... aside from pointing out about my "falacies" you have swipe nothing...

Best regards,

[Bgile]

Bgile:

what does this have to do with Renown vs Geneisenau?

You tell me: you are the one bringing the super heavy issue over and over. So, if you start being off topic don`t come to us saying what our rebutals are off topic.

I still don`t know how the super heavies could save Renown in this...

I wasn't trying to introduce the US gun into the debate. I was merely using it as a tool to indicate it's unlikely for the German gun to penetrate that much deck armor at that range, since the US gun can't do that. I'm sorry if people think that was intended to derail the thread. I will try to avoid using an example of something outside the topic like that, because it's obviously a hot button.

[Dave Saxton]

It appears that the 16” 2700 lb projectile (from both length guns) does get more than 100mm of deck penetration at 23km battle range though. It doesn’t seem unlikely at all that the German 15” gun gets approximately 100mm deck penetration at 23km. 23km is slightly more than 25,000 yards. Nonetheless it doesn’t really matter what we think is likely or unlikely as the Krupp data speaks for itself.

As far as being relevant to the question of an 15” gun Gneisenau vs Renown, it is established that the German 15” was not as weak in terms of deck penetration as the common wisdom seems to believe today. Indeed 100mm effective of top quality deck protection is only adequate to about 25,000 yards against the German 15”. And if you plan on taking deck hits from this gun at ranges beyond 25,000 yards you better have 128mm+ effective RHA.

The British document on 1930’s capital ship design considerations posted by Thorsten is most interesting. I hope everybody can take the time to study it. Some of the ideas postulated are that a design that expects to stand in the line of fire in most cases should be balanced in terms of protection, firepower, and speed. Although it will not be taking fire from its own gun, it is unreasonable to expect that an opponent’s gun will not be about as powerful or almost as powerful as the ships own gun. Another idea put forth was that it was optimistic that your own ship will be able maintain a favorably oblique target angle relative to your opponent’s gunfire in a real battle. Indeed maintaining a 20* target angle was probably unlikely much less a 30* target angle.

[Bgile]

The first document link posted by Thorsten is also quite interesting, as it shows the British expected to be able to penetrate Bismarck's deck protection into her engineering spaces at less than 22,000 yds. They don't seem to have considered the spacing between the two armored decks or the British fuse delay or yaw to be relevant to the issue.

I'm not sure what relevance a balanced design is here, since Renown obviously wasn't, and neither was Bismarck. Renown was under armored against low trajectory hits. Bismarck was over armored against short range attack against her vitals, under armored with respect to her turrets and barbettes compared to the penetration capability of her own guns, and the British seem to have felt she was quite weak against deck hits.

[dunmunro]

It appears that the 16” 2700 lb projectile (from both length guns) does get more than 100mm of deck penetration at 23km battle range though. It doesn’t seem unlikely at all that the German 15” gun gets approximately 100mm deck penetration at 23km. 23km is slightly more than 25,000 yards. Nonetheless it doesn’t really matter what we think is likely or unlikely as the Krupp data speaks for itself.

As far as being relevant to the question of an 15” gun Gneisenau vs Renown, it is established that the German 15” was not as weak in terms of deck penetration as the common wisdom seems to believe today. Indeed 100mm effective of top quality deck protection is only adequate to about 25,000 yards against the German 15”. And if you plan on taking deck hits from this gun at ranges beyond 25,000 yards you better have 128mm+ effective RHA.

The British document on 1930’s capital ship design considerations posted by Thorsten is most interesting. I hope everybody can take the time to study it. Some of the ideas postulated are that a design that expects to stand in the line of fire in most cases should be balanced in terms of protection, firepower, and speed. Although it will not be taking fire from its own gun, it is unreasonable to expect that an opponent’s gun will not be about as powerful or almost as powerful as the ships own gun. Another idea put forth was that it was optimistic that your own ship will be able maintain a favorably oblique target angle relative to your opponent’s gunfire in a real battle. Indeed maintaining a 20* target angle was probably unlikely much less a 30* target angle.

The 38cm penetration of Wh (Wotan hart) doesn't necessarily correspond to that gun's penetration of other nations deck armour. Okun's penetration data seems to indicate that it was inferior to USN and RN NCA armour:
http://www.navweaps.com/index_nathan/Pe ... ermany.htm

I don't see anything in the document to suggest that maintaining a 20+ deg target angle was unlikely. In fact, looking at WW2 BB actions it seems that higher target angles were probable and that lower target angles were unlikely.

[Dave Saxton]

......The 38cm penetration of Wh (Wotan hart) doesn't necessarily correspond to that gun's penetration of other nations deck armour. Okun's penetration data seems to indicate that it was inferior to USN and RN NCA armour:
.....

Post war British testing with their 15" APC and also 8" projectiles against Wh plates compared to their own NCA doesn't indicate this at all. In fact it took on average about 7%- 10% more energy to penetrate the Wh than it did the NCA.

[Dave Saxton]

The first document link posted by Thorsten is also quite interesting, as it shows the British expected to be able to penetrate Bismarck's deck protection into her engineering spaces at less than 22,000 yds. They don't seem to have considered the spacing between the two armored decks or the British fuse delay or yaw to be relevant to the issue.

I'm not sure what relevance a balanced design is here, since Renown obviously wasn't, and neither was Bismarck. Renown was under armored against low trajectory hits. Bismarck was over armored against short range attack against her vitals, under armored with respect to her turrets and barbettes compared to the penetration capability of her own guns, and the British seem to have felt she was quite weak against deck hits.

After the war the British built a mockup of the German deck protection scheme to test against when they were reevaluating the effectiveness of their armor piercing shells. They found that their earlier ideas about the expected German vulnerability to deck hits had been somewhat wrong. The German system was found rather effective because it always removed the cap from the shell and it always induced yaw. To see how a de-capped 14" APC would perform against the panzer deck, un-capped 14" armour piercing shells were fired at a 4" homogenous plate 65* from the normal to simulate conditions at 25,000 yards battle range. They found that the 14" uncapped shell could defeat that thickness of armour, at those striking angles, if the velocity exceeded 467 meter/sec and there was no yaw. These two conditions would not be obtained in practice, however.

I don't see Gneisenau as unbalanced with a 15" armament although it certainly was with 11" armament. I also don't find the German designs as unbalanced in too much bias against short range fire at the expense of deck protection.

[Bgile]

Yaw always seems to be the "magic bullet" when defending German armor schemes. Do we really have any idea how much effect this has? We know that a 2" deck actually deflects a shell toward the normal, which helps it penetrate a succeeding deck. How much yaw is induced and in what direction?

How might I access these British studies?

[Thorsten Wahl]

Yaw always seems to be the "magic bullet" when defending German armor schemes. Do we really have any idea how much effect this has? We know that a 2" deck actually deflects a shell toward the normal, which helps it penetrate a succeeding deck. How much yaw is induced and in what direction?

How might I access these British studies?

me too

[Dave Saxton]

Don't confuse yaw with trajectory change as a result of penetration. They are two different things. As far as trajectory change, the Germans determined that in the case of Wh materials the amount of trajectory change after penetration was ~4* if the thickness of the Wh plate was 50% the diameter of the shell. In the case of the German oberdeck it was only about 13% the diameter of battleship caliber shells, so the amount of trajectory change isn't very significant.

American studies of yaw of small caliber projectiles during WWII indicated that a yawed projectile can require up to ~38% more velocity to obtain penetration than a non-yawed projectile at the same striking angle. A modern American study by the US National Laboratory of Yawed Oblique Impacts indicated that if the yaw was nose up at impact it required typically ~28-30% more energy to obtain penetration, or if it was nose down about 15% more energy. This same study indicated that if the projectile wasn't yawed prior to impact, or nose down, the trajectory change after penetration was more toward the normal, but if it was yawed nose up prior to impact the trajectory was changed away from the normal.

One of the Krupp engineers commented that in the case of calculating the penetration of a two plate system; that it can be done taking one plate at a time, if you know the striking angle, the remaining velocity, the remaining shell weight without the cap, and if there is no nutation or precession. If there is nutation and precession (yaw) then exact calculations become rather too complex to make accurate predictions using this methodology. Another, Krupp engineer developed a reliable and simple mathematical model for calculating the approximate necessary velocity for penetration of a properly designed two plate system though.

I don't how you can access the British study? I don't know if it is available on line? I can't send it over the internet.

[tommy303]

Don't confuse yaw with trajectory change as a result of penetration. They are two different things.

This true, but to expand a little more on it, yaw is a function of stability in spun cylindro-conoidal projectiles and can be visualized by picturing a child's top. When at high enough speeds, the top is stable and moves only very slightly in a very small circle, the center of which is the top's axis. Virtually all spun bullets or shells have a small amount of yaw to them and yaw increases as rate of spin decays, much as yaw in a top increases as its rate of spin slows down until it becomes completely unstable and tumbles over. A shell can do the same thing if it is in the air long enough, though designers tend to impart sufficient spin to keep it stable over the whole of its trajectory out to maximum range (this is a tricky calculation as you do not want the projectile to be over or under spun--in the former the shell nose may not turn downwards to follow the curve of the trajectory, and this leads to more friction resulting in decreased range and possible problems at the target; in underspun projectiles the shell may wobble in flight leading to increased friction, decreased range, and higher dispersion rates).

While yaw and trajectory changes are certainly different things, they often go hand in hand. Impact with the target can cause a trajectory change if the conditions are right, but it can also cause increased yaw if the impact causes an abrupt slowing of the projectile. A sufficient check in velocity will cause yawing, even in cases where no trajectory change has occurred, such as in a right angle impact against armour. If the trajectory change is particularly severe, as in a shell penetrating a calibre-thickness plate after an oblique impact, it can induce more yaw in the projectile beyond that cuased by the the loss of velocity.