15in Up Gunned Gneisenau v 1939 Modernized Renown

[Bgile]

.... I think laminate is closer to a single plate than two separate plates in effective thickness, is it not? And US homogeneous armor plate is as good as anyone's.

Actually in British tests post war they found that laminates had less ballistic resistance than if the plates were spaced.

How much spacing? Was that for homogeneous armor or face hardened? What was the difference in effective thickness?

[Dave Saxton]

Doesn't matter. The laminates (including H/H) were the worst perfoming of all the various combinations tested.

[Bgile]

Doesn't matter. The laminates (including H/H) were the worst perfoming of all the various combinations tested.

Well, I'm interested in the effective thickness of US 2nd deck armor, so it does matter.

[Dave Saxton]

Krupp developed a simple formula for calculating the necessary velocity or effective thickness for multiple plates and laminates in most cases:

Vnot={square root} v1(squared) + v2 (squared)...ect...

This formula doesn't apply to all cases though. This will give you the correct enough Ep for the laminated deck but not for the combination of the main deck and the yaw deck. A more sophisticated methodology (beyond the scope here) indicates that the effective thickness of the main deck + the upper armoured deck; is about 88% the sum of the main deck effective thickness and the upper deck. The yaw deck's yaw factor is essential and gives the fast battleship's good overall deck protection, but if you throw that out the engineering appears less efficient.

[Bgile]

Krupp developed a simple formula for calculating the necessary velocity or effective thickness for multiple plates and laminates in most cases:

Vnot={square root} v1(squared) + v2 (squared)...ect...

This formula doesn't apply to all cases though. This will give you the correct enough Ep for the laminated deck but not for the combination of the main deck and the yaw deck. A more sophisticated methodology (beyond the scope here) indicates that the effective thickness of the main deck + the upper armoured deck; is about 88% the sum of the main deck effective thickness and the upper deck. The yaw deck's yaw factor is essential and gives the fast battleship's good overall deck protection, but if you throw that out the engineering appears less efficient.

Thank you.

[dunmunro]

Regarding laminated plates, Nathan Okun has a formula that he uses:

http://www.navweaps.com/index_nathan/Mu ... ussion.pdf

see page 7.

[Dave Saxton]

There is very good agreement between the USN rule of thumb and the Krupp formula. This forumula also works fairly well for multiple, relatively thin, spaced plates were de-capping, and yaw ect.. have little effect- as per the USN rule of thumb there. (Try this forumula on the Hood deck arrangement) Krupp had settled the question by experimentation. They built full scale mock ups of their own arrangements and those of foreign designs and tested them with live fire. Dr. Kratz used a very similar methodology to Nathan's for single plates, also based on deMarre, but he stated that it was problematic to extend this type of methodology to multiple plates were de-capping, nutation, and precession are in play.

Another Krupp engineer, Dr. Geroke, developed more usefull models for both single and multiple plates. These models used contstants for the material properties of the exact armour types, and also accounting for the caliber of, and design features of the APC shells, and scaling effects. A moddified version of his model could also be extended to examination of special two plate spaced arrays.

The results of British post war tests of several two plate systems is predicted almost exactly and consistently by Geroke's methods. The results of the various spaced arrays in the British tests varied widely from effective thicknesses of well less than the sum thickness to effective thicknesses exceeding the sum thickness, depending on the specifics of the design, spacing, and the materials used. For example, a spaced array consisting of an NCA de-capping plate and a FH resistace plate gave an effective thickness greater than the sum thickness of the two plates when attacked by sub caliber shells, but the effective thickness was slightly less than sum thickness when attacked by super caliber projectiles. This was because of the use of a CA resistance plate instead of an homogenous plate of a calculated tensile strength and hardness.

[Dave Saxton]

The USN calculation (close to the Krupp formula results for the laminate) for laminated plates sits well into the IZ calculations listed in G&D for the USN BB's, if the STS yaw deck has the effect that the Krupp methods predicted it would. This gives an IZ for NC extending to 28,000 yards vs 14"/50 shell fire. And it gives similar IZ's for SD and Iowa vs the Maryland's 16"/45.

[Thorsten Wahl]

for quick reference
From navsource


http://navsource.org/archives/01/015501e.jpg
http://navsource.org/archives/01/015501d.jpg

[Dave Saxton]

I typed out the relavant passages from the BoO correspondance word for word. This is mainly about developing spaced armour for aircraft armour protection. For our purpose only the first few sentences are most important as it proves that the weather deck armour of the USN fast battleships was a yaw deck and designed as such, and intended to function as such vs battleship caliber AP shot. I included more because it is instructive about certain aspects of how yaw effects the ballistic performance in all spaced armour arrays. The tests indicated that using particular material properties for the homogenous armour could cause the velocity required for penetration to exceed that of an single STS plate of equal thickness. This amount was not insignificant with Vnot being up to 138% that of a single plate of equal thickness. This agrees well with Krupp data of two plate systems of particular design and materials.

……….©. Yaw Plates

The first experiments with yaw plates to improve the ballistic properties of armor were carried out by the Bureau in 1936 in connection with the design of the protective decks of the new battleships. Extensive tests were made with the view of utilizing a 1 ½-inch main deck as a yaw plate for major caliber A. P. projectiles. Then the Bureau set up a project at the NRL for this study of light aircraft armor. The subject of yaw plates was stressed in the early stages. The 4th and 5th partial reports of 1938 and 1939 dealt exclusively with this subject. In the 7th report of March 1940 a specific design for armored aircraft next utilizing yaw plates was submitted. The NRL tests were followed up by similar tests at the NPG proving great improvements in the ballistics properties due to yaw plates. Reference D is a comprehensive report of a test conducted at Aberdeen to determine yaw as a function of obliquity and distance from the yaw plate for different materials. As would be expected the yaw varies with distance from the yaw plate, it does not necessarily follow that the ballistic protection varies in the same manner as the yaw. There is the possibility that once the projectile has a yaw above a certain minimum it, results in a flat impact, giving maximum ballistic protection. A program to further study this aspect is being considered.

It is considered that the data on the general characteristics and the ballistic improvements due to yaw plates is sufficiently advanced now to make possible their utilization in armor. More work along some general lines (min yaw required for flat impact…ect…) is contemplated. Also some general problems will probably have to be investigated in connection with specific design for aircraft protection. A large program as to reference A is not necessary…..

The British in their tests with a full scale mock up of the Tirpitz array and using actual battleship caliber shells found that the distance from the yaw plate and its effect on the amount of yaw developed did have effect on the ballistic protection in cases of relatively slow rates of precession, which they enccountered using the American battleship APC with blunt head shapes. The distance between the panzer deck and the upper deck as per the original German design was ideal to develop the min yaw required to cause flat (yawed) impacts.

[lwd]

Interesting but at least in the case of the North Carolina's it doesn't support the deck being designed as a "yaw" deck. At least according to wiki at:
http://en.wikipedia.org/wiki/North_Caro ... battleship
The preliminary designs predate 1936 and by October the designs had been pretty well established. Especialy with the references to the armored upper deck as being designed as a bomb deck it looks to me like these tests actually just produced more data on the benefits of that deck in regards to AP rounds.

[Dave Saxton]

That seems quite a stretch to me. Last I checked NC has a 1 1/2-inch upper deck just as described in the document. NC was the new battleship at the time of the document. 1936 is plenty early enough to work these findings into the design. The bomb deck idea makes a nice cover when such matters were still highly classified though . But a 38mm bomb deck doesn't function as such very well in practice.

[RF]

Coming back to the arguments in the original thread, it appears that the consensus is that Gneisenau would have had the edge over Renown.

Suppose we switch Renown for Warspite - do you think the same edge would apply there, or is Warspite a tougher nut to crack?

[Bgile]

If the German ship decides to accept combat, Warspite has thicker armor than Renown and more guns. The date would determine whether Warspite had radar FC. Gneisenau can dictate the range, but not sure if that helps her much.

[Thorsten Wahl]

I take QE class as nearly equivalent to the R-Class
Unterlagen zur Bestimmung HKE are expecting an advantage for the british ship at distances between 15-20 km because of the disadvantage with original 280 mm guns in punching performance against belt
So recomended distance should be less then 15 km or over 20 km