15in Up Gunned Gneisenau v 1939 Modernized Renown

[Bgile]

Bgile:

OK, my mistake. 29,000 yds then. Not much difference. Neither one is very good at deck penetration because of the flat trajectory.

I do believe that a 15" shell from Bismarck, plunging, was the one that blew Hood. Hardly flat trajectory.

This is a quote from Bill Juren's study:

"A number of authors have attributed the loss of Hood to insufficient deck armor, stating in effect that she was lost due to an excessive vulnerability to plunging fire. The results of a recently developed computer program, however, seem to suggest that rather than being too thin to adequately protect her, Hood's deck armor was in fact at or near the thickness that would have granted her maximum protection at normal battleranges."

It seems more likely that her side armor was penetrated.

[Thorsten Wahl]

Renown has 4" + 1" of D steel deck armour over the magazines and about 3.5" over the machinery, but the armour is layered and there are thinner decks above the MAD. There is a 2.5" turtle deck behind the 9" main belt which is also inclined about 12 degrees.

Thanks for the additional information.
12 degrees from the vertical?
If so the additional 2,5" slope werent that suitable to improve ballistic abilities of the whole system on relativly low oliquique impacts. The required speed for penetration is less then 100m/s. But it offers splinter protection if the AP-projectile detonates in front of this bulkhead.

4" + 1"
the 1" deck has no relevant ballistic abilites even at high oblique impacts. And it doesnt prevents the parts behind this bulkhead from splinterdamage
the 4" impact resistance has been described above.
the 3,5" protection over machenery offers somwhat less protection then the 4"

If the Gneisenau was using its original 280 mm guns then the deck protection of R offers better protection, vertical protection were roughly comparable at mid to long range engagements, but on low range engagements the Gneisenau should have an advantage due to the better vertical protection. (More guns higher ROF)

[Karl Heidenreich]

Bgile:

It seems more likely that her side armor was penetrated.

I found rather difficult to guess what`s your agenda on this one, but:

Bill Jurens estimated about 18,000 meters the distance from Bismarck to Hood when the fatal shot hit the latter. At these ranges the Bismarck's shells will have velocity of about 550 meters/sec, and the angle of fall will be only about 15 degrees: Indeed flat for those ranges. Anyway this is not the case if distance increases to the 25,000-30,000 yard range in which the shell will travel in a parabolic trajectory and "falls" or "plunges" over the enemy ship`s deck with a steeper angle.

Now, the HMS Hood had zero IZ against the German 15" and, for that same matter, neither would have the Renown, which makes your previous statement invalid. The 11" could also have defeated the thin armour, both belt and/or deck of the British battle cruisers at most battle ranges.

Best regards

[Bgile]

Bgile:

It seems more likely that her side armor was penetrated.

I found rather difficult to guess what`s your agenda on this one, but:

Bill Jurens estimated about 18,000 meters the distance from Bismarck to Hood when the fatal shot hit the latter. At these ranges the Bismarck's shells will have velocity of about 550 meters/sec, and the angle of fall will be only about 15 degrees: Indeed flat for those ranges. Anyway this is not the case if distance increases to the 25,000-30,000 yard range in which the shell will travel in a parabolic trajectory and "falls" or "plunges" over the enemy ship`s deck with a steeper angle.

Now, the HMS Hood had zero IZ against the German 15" and, for that same matter, neither would have the Renown, which makes your previous statement invalid. The 11" could also have defeated the thin armour, both belt and/or deck of the British battle cruisers at most battle ranges.

Best regards

My quote was not fabricated. Nathan Okun's ballistics table (http://www.navweaps.com/index_nathan/Pe ... _index.htm) shows Bismarck's guns can't penetrate 4" of horizontal armor inside about 29,000 yds. That would also be true of the same guns on Renown.

[Karl Heidenreich]

Bgile:

My quote was not fabricated.

No, just mistaken.

[Bgile]

Bgile:

My quote was not fabricated.

No, just mistaken.

You don't have to accept it, but it's there for anyone to see.

[Karl Heidenreich]

[Dave Saxton]

We must remember that these tables online are based on the mostly theoretical. The deck penetration data in these tables doesn't square with much primary documentation. (The FH penetration for the British CA is reasonably close though) As far as the German shell performance, the best data is indeed the Krupp curves because it is based mainly on extensive and repeatable real world testing:

Obviously after such a mathematical normalization of the curves, values need to verified by actual firing trials. The finalized characteristics of the curves as they used for computations, is settled, here again, by experimentation. Years of work have produced such sheets of penetration graphs for both types of armor plates as well as for armor piercing shells used by the Navy.....please allow me to say a few words about the mathematical procedure. The question about which plate thickness is penetrated by a given projectile at a given distance can be readily answered from the penetration curves. The impact angle and the terminal velocity can be derived from the distance; therefore, the parameter for plate thickness can be obtained from the curves...... (Hoyer)

The German 15" could penetrate 4" of homogenous armour by 22-23km (24-25k yards) battle range according to the primary data. In my opinion the Krupp penetration data and methodology is the most correct and will not also be not too much different for non-German shells of the same caliber, per angle of striking and impact velocity. The British testing of their own 14",15", and 16", shells indicated that their shells "could not penetrate up to 6" of homogenous armor at any range less than 32,000 yards." A major limiting factor of the British shells they determined from the tests was the relatively sharp shape of the shell's head of 1.4 caliber radius. The American (even lighter per caliber models) shells did better compared to the British shells against single layer deck systems mainly by using a rather blunt head shape. The L/4.4 head shape was in between the American and British practice among other factors of the L/4.4 design.

[Bgile]

As far as I know, Okun used primary data to compare with his tables, and they agree pretty closely. Can you show us where the German primary data is?

If you are correct, it isn't hard to imagine what the US Mark 7 projectile would do against Bismarck's deck. Rounder nose, heavier shell. Okun is a lot more knowledgeable than any of us here.

Maybe we can settle all this by just agreeing that this is a Bismarck site and so Bismarck's shells outperform anyone else's against both horizontal and vertical armor at all ranges.

[Bgile]

OK, what Dave is claiming is Bismarck's 1,764 lb shell will penetrate the same amount of horizontal armor as the US 2,700 lb shell fired by the 16"/50 cal gun.

I'm beginning to see that my contribution here is of questionable use and maybe I should leave this sort of thing to the people who come hear to learn only of German superiority in all things. I hate to do this because I enjoy this sort of thing, but it's beginning to approach the level of absurdity.

[Dave Saxton]

LOL.. The data is hard data and is not subject to modern biases. The curves and associated data are contained within Gkdos100 and Jose has at times posted pages of this data. The Krupp engineers, like Dr Kratz and Dr Geroke, and people like Hoyer, and non Germans like Dr Simon, and Dr Richie, in the US to name just a few, knew far more than anybody today.

[Karl Heidenreich]

Bgile:

Okun is a lot more knowledgeable than any of us here.

Are you sure? Life is full of surprises.

[Dave Saxton]

OK, what Dave is claiming is Bismarck's 1,764 lb shell will penetrate the same amount of horizontal armor as the US 2,700 lb .

Using what data set?

At a range of only 24,000 yards and striking at about 70* from the normal, I would not expect the results (assuming the same data set) to be greatly different in terms of inches. I think you will find that 14", 15", and 16" caliber shells with relatively blunt head shapes will obtain similar deck penetration at such acute striking angles (~70* from normal). For example, it will be about 125mm deck at ~ 60 degrees from the normal for this range of projectile calibers, at the typical terminal velocities, at the ranges were they obtain that angle of fall (30*). I would not expect a penetration graph per range to plot the same for these shells as the range increases through. On such a graph it will plot as a curve that has a compoud radius and will not be linear. The curves for different gun/shell combinations will plot differently, because of the rates that heavier and lighter shells of differing aerodynamics loose velocity, and because of their different mass, and because their head shapes may also be different. The compound radius plot of the German 15" will be rather flat from 22km through 30km, such that it only increases from ~4" to ~5" penetration. The 16"/50 plot will be less flat through that range, but still more flat than a 16"/45 with the same shell. After the angle of fall reaches approximately 30* then the plot's curve shape changes and deck penetration really takes off in most cases.

A heavier shell with a blunter head shape would have greater penetration vs a single plate deck system. It quickly gets very complicated when de-capping, and yaw, are introduced into the equation though. Trade offs will be enccountered.

[Thorsten Wahl]

As far as I know, Okun used primary data to compare with his tables, and they agree pretty closely. Can you show us where the German primary data is?

here is the piece

Image2.jpg

(188.28 KiB) Not downloaded yet

If you are correct, it isn't hard to imagine what the US Mark 7 projectile would do against Bismarck's deck. Rounder nose, heavier shell. Okun is a lot more knowledgeable than any of us here.

Maybe we can settle all this by just agreeing that this is a Bismarck site and so Bismarck's shells outperform anyone else's against both horizontal and vertical armor at all ranges.

no performance of Mark 7 is better than PzSprG 38 m BdZ. The longer the distance is, the better the Mark 7 performs compared with the german projectile due to its lower loss of energy in flight.

But in terms of energy used up by penetration the german projectil is still better, because its needs less energy to pentrate the same amount of armor even taking in account the smaller diameter

[Karl Heidenreich]

But how the USN Mark 7 will help Renown in a fight with a 15" gunned Gneisenau, I don`t know? In that case we can talk about the Japanese 18" too, if required. To what purpose? Don`t know, you tell me...