Hood v Vittorio Veneto

[dunmunro]

Dunmunro wrote: "VV's turret faces are quite thick but the 30d inclination means that almost any hit will have less than 30d obliquity where the 14in AP is very efficient, so the turret faces are probably not immune in a short range fight."

Hi,
that's true at long range, from where the vertical turret armor of the KGV offered a better protection. At short range, with almost flat trajectories (under 15° even for slow British 14") the inclined armor is better than a vertical one.

Another reason not to approach the Littorio's

Bye, Alberto

It might be better but it would still be vulnerable to the 14in AP hits so neither ship's main armament is safe.

[Alberto Virtuani]

Maciej wrote: "I don't know how concrete will work."

Hi,
there was no concrete in between, just air, to facilitate the "precession" motion.

you wrote: "So in that situation, against 14" British shells, we can simply add those two plates, and have no real difference in protection."

I don't see your point. The Italian gun is given a perforation of 460mm KC at 16km (according to cautionary "fighting instruction") or 550 mm (according to OTO Melara data or US empiric formula)......
So the array worked much, much better than the sum of the 2 plates against it.....

Against the 14", who knows, but for sure I don't expect such a bad performance of just 350 mm (70+280)......


Bye, Alberto

[dunmunro]

Maciej wrote: "I don't know how concrete will work."

Hi,
there was no concrete in between, just air, to facilitate the "precession" motion.

you wrote: "So in that situation, against 14" British shells, we can simply add those two plates, and have no real difference in protection."

I don't see your point. The Italian gun is given a perforation of 460mm KC at 16km (according to cautionary "fighting instruction") or 550 mm (according to OTO Melara data or US empiric formula)......
So the array worked much, much better than the sum of the 2 plates against it.....

Against the 14", who knows, but for sure I don't expect such a bad performance of just 350 mm (70+280)......


Bye, Alberto

The RN knew, prewar, that the RM was using spaced armour on VV and in 1943 they were able to obtain the precise details. Post war the RN built an accurate model of VV's spaced armour and tested it. The results were as I and Maciej stated.

Again, we don't know the differences between RM and RN AP shells and how those differences effected their performance against spaced armour.

Bagnasco. p.76 states:

With respect to its power to penetrate case-hardened vertical plates, at a distance of 23,774 metres, the 381/50 ball ammunition was able to penetrate 348mm of armour plate (at a terminal velocity about 550 m/s) at a 90° angle of impact*. This fell to 238mm at a 50° impact angle**. Maximum penetration of 416mm was achieved 19,000 metres at a 90° angle of impact.
* 0 deg obliquity at 1805fps (DM)
** 40 deg obliquity (DM)

This is actually a bit worse than the RN 14/45: 350mm at ~1850fps at 30deg obliquity
Proofing trials showed that the RN 14/45 could perforate intact through 10in/250mm (400lb) CA/45deg obliquity at 1630fps (497m/s).
Proofing trials showed that the RN 14/45 could perforate intact through 8in/200mm (320lb) CA/45deg obliquity at 1290fps (393m/s).

[Maciej]

there was no concrete in between, just air, to facilitate the "precession" motion.

It is some time, since I have read Bergano’s “The Littorio Class”, so my memory could be flawed, but I remember, that “air” was between plates over machinery spaces. Over magazines that space was full with concrete or cement or something like that. M I right or wrong?

I don't see your point.

I will try to explain. But sorry about language problems. English is not my first language.

The Italian gun is given a perforation of 460mm KC at 16km (according to cautionary "fighting instruction") or 550 mm (according to OTO Melara data or US empiric formula)......

I’m very curious how was calculated that performance.
In case of “US Empirical”, it is worthless, if You calculate penetration of perforation limit of shells and armours other than US. And specific US.
Haw was calculated 460 mm KC capability calculated by Italians? I don’t know, but I want to know.

So the array worked much, much better than the sum of the 2 plates against it.....

Possibly against shells, Italy tested. In case of British, I checked 1948 year report now.

There are rumors about 1903 tests of decapping composition. In 1903 test – composition failed.
Than in 1908 was next series of such tests. Composition failed.
In 1919 next series was done, again with “disappointing results”
Some details of those tests are given, but not much.

In 1937 reports were received that Littorio will be fitted with that spacing array. It was reproduced and tested.
Target was build with 80 lbs NC forward plate and 480 face hardened main plate. It was fired by 15” shell at 30 degree oblique impact with striking velocity 1613 feet/s ( limit of perforation to 600 lbs one plate ). I know that 480+80 = 560 lbs, but heavy support structure was considered to be equivalent of weight of 40 lbs plate. In later test “box structure” was considered the same weight as 20 lbs plate.
Assembly was defeated, the shell passing through with considerable remaining velocity
( direct citation )

In 1943 it was learnt that Littorio had 2.75” external Krupp cemented plate, than 6 to 7” “egg-box” construction than 11” Krupp cemented plate.
Tests inconclusive.

Than in July 1948 next series of tests, with different combination of first and second plate. Not many combinations, but more than one.
Shells used for tests were 14” and, 9.2” and 8” caliber. Oblique angle 45 degree for 14” shells and 30 degree for rest.

In short conclusions:

Against calibre or subcalibre attack spaced array is equivalent to solid plate of the same thickness. In braking shell capability, spaced armour is nearly 100% as effective.

Against supercalibre attack spaced array is worse than solid plate of the same thickness.

So in short.
In case of Littorio’s 280 + 70 mm armour. Against KGV guns its armour was equivalent to ~360 mm of solid plate ( extra 10 mm for supporting structure )
Against Nelson, Littorio’s armour is a bit worse than solid plate 360 mm thick.

Against the 14", who knows, but for sure I don't expect such a bad performance of just 350 mm (70+280)......

So lets say it was equivalent of 360 mm plate.
Not bad, but not so superior.

[Alberto Virtuani]

Hi Macej,
I can confirm no concrete was used on Littorio's. I don't know about the RN tests.


The Italian tests gave an immunity to the array combination against the 15" Italian gun at 16km range,
They initially gave good results for an array with distance of 60 cm between the plates but the void space in between was judged a danger for the buoyancy of the ship. So RM tested the array with 25 cm separation space and found it was even better as it caused the shell to hit the second plate in a bad stability situation. In any case much better than the sum of the 2 plates (else Italians would have built a single plate instead of an array......)

I do think that if the array was safe against the Italian 15" at 16 km (perforation between 460 and 550 mm KC vertical armor), it should be immune against the British 14" at 12 km.

The result of the tests, as well as the penetration data, is reported by E.Bagnasco in his book ("Littorio Class Battleships") in the appendix and here as well: (the empirical formula is reported by Bagnasco as OTO Melara tested data)
http://www.navweaps.com/Weapons/WNIT_15-50_m1934.htm

As a comparison, here you have the British 14" performances.....
http://www.navweaps.com/Weapons/WNBR_14-45_mk7.htm

Bye, Alberto

[dunmunro]

Here's the output from NAaB for the RM 15in / RN 14in

Penetration* / Range yds. / SV f/s / Descent °

RM 15in @ MV = 2789fps
20.7 / 5,000 / 2,533 / 2° 1.9'
18.1 / 10,000 / 2,296/ 4° 39.0'
15.8 / 15,000 / 2,085 / 7° 59.4'
13.7 / 20,000 / 1,906 / 12° 10.5'
11.9 / 25,000 / 1,769 / 17° 10.4'
10.3 / 30,000 / 1,674 / 23° 0.8'
9.2 / 35,000 / 1,627 / 29° 20.4'
8.4 / 40,000 / 1,626 / 35° 48.4'
6.8 / 45,000 / 1,666 / 42° 21.4

RN 14in @ MV = 2483fps
20.7 / 5,000 / 2,234 / 2° 35.9'
17.7 / 10,000 / 2,008 / 6° 0.6'
14.9 / 15,000 / 1,812 / 10° 29.1'
12.5 / 20,000 / 1,657 / 16° 9.0'
10.0 / 25,000 / 1,552 / 23° 0.9'
8.1 / 30,000 / 1,504 / 30° 43.2'
6.5 / 35,000 / 1,511 / 39° 15.1'
4.9 / 38,600 / 1,558 / 46° 23.4'

*RM facehard armour @ 15deg inclination.

NAab gives the RM gun an advantage but not a huge one and the advantage declines at closer ranges.

[Maciej]

Be very careful with data of performance of guns on navweaps.com
It is various mix of data collected from various sources, but problem is that not always is stated what is source of penetration data!
More – data for different guns are for different situations.
In this particular example of British 14” gun and Italy 15” gun

1. British gun is “used”. “New gun” had muzzle velocity 2483 feet/s, but in table is for MV 2400 feet/s
It is considerable difference. For example difference in MV between American 14” C45 and C50 guns is 100 feet/s. So in those tables KGV guns are at start degraded for nearly one generation.

2. How is initial temperature of propellant for MV? I don’t know for what temperature are data for Italy guns, but British were for a bit cooler propellant compared to US. It gives less difference, but still next ~20 feet/s ( in case of taking British guns to US standard in initial MV). Add those two parameters, and it is more or less safe to simply add ~100 feet/s MV of British gun in those tables, compared to US.
If Italy guns are for the same temperature, than ~80 feet/s
It is considerable difference. Calculated difference in penetration between C45 and C50 American guns at 15 000 yards is about 1 inch.

3. In what atmospheric parameters ballistic tables are calculated. Again different temperature and density of atmosphere are used in different navies, so shell fired with the same MV will generate different hit velocity and angle of impact due to different air resistance. Again, I have no knowledge about Italy “standard atmosphere”, but in case of British/US, British “standard atmosphere” used to calculate ranges, is more dense and cooler, co makes larger resistance to shell. So even if shell is fired with the same MV, will slow down faster! Reason was not different shells shape, but different parameters used to calculate standard tables! It is quite obvious that if there is tow to tow battle, real fight tables will be in the same atmospheric parameters, as air will be the same. So British shells will gain performance, or US will loose performance ( or both ) compared to “ideal situations” used to calculate tables.

All of those need to be taken to the same initial parameters just to calculate range table, to have correct data about striking velocity and striking angle, to be able to compare apples to apples, not apples to oranges.

And last but not least.
How those penetration data are calculated. If You take those initial data to the same initial principles, than You need to calculate penetration.
How.
Different navies used different formulas, with different results. So taking data from primary sources are good, but again not directly comparable to each other, as different criteria were used to give “critical velocity” in different navies!
One of the choices is use the same formula for calculations.
Many data on navweaps are calculated that time.
But most (all) of those formulas ignores armour quality and shell construction.
Example “US Empirical”. I used it extensively for some time.
It takes:
armour thickness
diameter of shell
mass of shell
angle of impact
and gives velocity of penetration.
Doesn’t matter what quality of armour is, or what construction of shell is. You take two shells with the same mass, and the same striking parameters, and will have the same penetration.
So according to that formula, switch to different heavy shell in US in late part of WWII changes nothing.
But we know that it changed much in reality.

In case of other country shell/armour that formula is useless. Error is so large, that results You can throw away.
For example – we know penetrating power of KGV shells. In tests it penetrated british 12” plate at 30 degree oblique angle with speed corresponded to ~25 000 yards or more.
When You see range table, it is quite simple to see that at ~25 000 yards descent is ~30 degree ( for used gun, with new gun will be better ), so at that distance that shell is able to penetrate 12” british plate. Used gun, not new.
US Empirical gives penetration capability at that distance 9.5”. Of US armour ( as US armour was used to make that formula ), and it is known that British armour was a bit stronger.
Add to this, higher MV for British gun, less air resistance, higher temperature of propellant, and easy You could add about an inch of penetration capability.
So if You want to compare US with KGV guns penetrating power, You need to put penetration capability of KGV at 25 000 yards ~13", to have the same initial parameters as US guns.
Not 9.5" as is put on navweaps.

FaceHard by Nathan Okun tries to include all those differences in armour/shell quality ( not in ballistic, as it not calculated ballistic tables ).
I know about severe critical statement about that program. It is clearly not perfect, but makes better results than any other formula.

[alecsandros]

So lets say it was equivalent of 360 mm plate.
Not bad, but not so superior.

The British tests that you quote are flawed, as they did not use the materials used by the Italian or German navies, did not properly space the plate, and did not decline the plates at the historical angles used in foreign battleships.

Rheinmetal Borsig trials showed that a fully decapped shell will shatter in contact with a KC plate of minimum 0.6 diameters in thickness (so 400mm shell will shatter against 240mm KC plate). The problem was to ensure "full" decaping, and that required considerable space between initial plate and main plate.

[Alberto Virtuani]

Maciej wrote: "All of those need to be taken to the same initial parameters just to calculate range table, to have correct data about striking velocity and striking angle, to be able to compare apples to apples, not apples to oranges."

Hi Maciej,
I do agree, but I haven't yet seen a final comparison table that can be universally accepted......

Dunmunro wrote: "NAab gives the RM gun an advantage but not a huge one and the advantage declines at closer ranges.
"

Hi Duncan,
I don't know the NAab data, but I have a problem to understand.... Let's make things simple:

The Italian shell was 885 kg , the British was just 721kg. Difference is huge (plus than 22%)
MV was 850 m/sec for the Italian vs 757 m/sec for the British. Difference is huge (plus than 12%)
Thus Italian shell initial energy was more than 50% superior than British one......
In addition, the Italian shell was explicitely designed with a very heavy cap and very heavy walls to enhance penetration, as a consequence it had a small change inside.....

Still these data gives no difference at very short range and limited at long range ???

Bye, Alberto

[dunmunro]

So lets say it was equivalent of 360 mm plate.
Not bad, but not so superior.

The British tests that you quote are flawed, as they did not use the materials used by the Italian or German navies, did not properly space the plate, and did not decline the plates at the historical angles used in foreign battleships.

Rheinmetal Borsig trials showed that a fully decapped shell will shatter in contact with a KC plate of minimum 0.6 diameters in thickness (so 400mm shell will shatter against 240mm KC plate). The problem was to ensure "full" decaping, and that required considerable space between initial plate and main plate.

The RN built a model of the RM armour array and tested it and the RM array has a very small space between the the two plates.

[dunmunro]

Dunmunro wrote: "NAab gives the RM gun an advantage but not a huge one and the advantage declines at closer ranges.
"

Hi Duncan,
I don't know the NAab data, but I have a problem to understand.... Let's make things simple:

The Italian shell was 885 kg , the British was just 721kg. Difference is huge (plus than 22%)
MV was 850 m/sec for the Italian vs 757 m/sec for the British. Difference is huge (plus than 12%)
Thus Italian shell initial energy was more than 50% superior than British one......
In addition, the Italian shell was explicitely designed with a very heavy cap and very heavy walls to enhance penetration, as a consequence it had a small change inside.....

Still these data gives no difference at very short range and limited at long range ???

Bye, Alberto

One factor is that the RN 14in has a smaller contact surface so that the energy per area doesn't vary as much as the total energy would imply. The RN discovered that the 14in Mk1B AP round was more efficient than the RN 15in. The RM's own test results show their 15in to be a relatively poorly performing round. This may have been due to head shape and the metallurgy of the shell but I don't have a complete answer.

[dunmunro]

Be very careful with data of performance of guns on navweaps.com
...

I set the armour with an initial 15deg inclination so you have to add 15deg to the AoF to get total inclination, which explains the poor performance of the RN shell at long range. I also adjusted the range and MV to 2483fps.

I know that NAab isn't perfect and the results are only a crude comparison.

[Alberto Virtuani]

Dunmunro wrote: "One factor is that the RN 14in has a smaller contact surface so that the energy per area doesn't vary as much as the total energy would imply."

Hi Duncan,
no the surface of 14" and 15" (assuming the whole surface is involved when striking an armor, that is not the case) doesn't differ much (less than 20%).

Here we have an Italian shell with more than 50% energy plus than the British shell.......

It's simply physically impossible that at short range the 2 guns perform the same way at 0° inclination. I can admit that due to head shape the British shell perform better at very high inclinations but not when striking almost vertically.....

Bye, Alberto

[dunmunro]

Dunmunro wrote: "One factor is that the RN 14in has a smaller contact surface so that the energy per area doesn't vary as much as the total energy would imply."

Hi Duncan,
no the surface of 14" and 15" (assuming the whole surface is involved when striking an armor, that is not the case) doesn't differ much (less than 20%).

Here we have an Italian shell with more than 50% energy plus than the British shell.......

It's simply physically impossible that at short range the 2 guns perform the same way at 0° inclination. I can admit that due to head shape the British shell perform better at very high inclinations but not when striking almost vertically.....

Bye, Alberto

Remember that the table isn't for zero obliquity - you have to add 15deg to the angle of fall to get total obliquity.

If we use 2/2.5deg (instead of 2/2.5 plus 15 degs) obliquity at 5000 yds then NAab predicts penetration of 28in /23.4in for the RM/RN guns.

NAab seems to imply that the RM 15in head shape was optimized for better performance at zero obliquity so at high SV the RM shell performs relatively better at zero obliquity but poorer at obliquities up to ~35 degs.

http://www.panzer-war.com/Naab/NAaB.html

[Maciej]

The British tests that you quote are flawed, as they did not use the materials used by the Italian or German navies, did not properly space the plate, and did not decline the plates at the historical angles used in foreign battleships.

What exactly was flawed?
External plate was 2.75” face hardened.
Than distance 6 to 7”
Than 11” plate face hardened.
What was difference compared to Littorio structure? Possibly details of supporting structure. Other things?

Of course British used plates “made in England” as others were unavailable, so it is possible that structure build from German or Italy plates will perform different.

Rheinmetal Borsig trials showed that a fully decapped shell will shatter in contact with a KC plate of minimum 0.6 diameters in thickness (so 400mm shell will shatter against 240mm KC plate). The problem was to ensure "full" decaping, and that required considerable space between initial plate and main plate.

Correct me if I’m mistaken, but in those tests German shell were used, not British.
So if we are interested how Littorio is protected against say Bismarck’s shells – than this test is important.
But if we want to check how Littorio is protected against KGV shells – test is badly flawed, as “wrong shell” was used.

As Duncan already stated – whole structure was reproduced, and tested. I will add – it was attacked at 30 degree oblique angle was used.
Conclusion was “slight advantage” of such structure.
Good question what does “slight” mean exact.