Vanguard and Bismarck

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Dave Saxton
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Re: Vanguard and Bismarck

Postby Dave Saxton » Fri Oct 20, 2017 5:50 am

Hoyer's 1943 lecture described how the belt and the scarp work together to prevent penetration of the vitals. Hoyer reported that if the scarp is heavy enough and set and an unfavorable geometry to the shell, it will prevent penetration at any battle range. If the scarp is heavy enough, the necessary velocity required of the projectile to penetrate both the main belt plus the scarp will exceed the shatter velocity of the shell. Or in other words, if the impact velocity is less than the shatter velocity then it cannot penetrate both plates. This is why in the H class they could reduce the thickness of the main belt to 300mm. The scarp thickness was increased to 150mm.
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Re: Vanguard and Bismarck

Postby Maciej » Fri Oct 20, 2017 9:35 pm


That is sort of calculation I name „creative counting”



Call whatever you want, but you are not arguing with me. You are arguing with scientists and engineers from Krupp and the Kriegsmarine,

As should be obvious for everyone English is not my primary language, so possibly I misunderstand something.
If I take it correct than German Krupp scientists show counting such way that:
Bismarck deck(s) were 130 to 150 mm thick
KGV/Vanguard decks were 127 to 150 mm thick
Iowa 140 mm thick and so on.
So it seems that
1. For Bismarck both weather deck and main deck should be just added
2. For British ships only single deck armour should be used, and all other decks omitted (so no backing, no weather deck)
3. For US ships armour and backing had to be simply added, and rest ommitted.

M I right, or I simply don’t understand something?

Or that sort of counting was not “German Krupp scientists” or some mistake done by someone else and repeated so many times, that some of us don’t even look at those figures?

Or something else?


who understood this far better than any of us.

Clearly.
But they were not alone in the world. Strange that all other scientists abandoned multi deck protection (commonly used in WWI era and before, to be honest later than single deck protection)
Only Germans were right? Or simply done nothing between the wars due to political limitations, and rest of the world simply made studies about battleship construction?
Or another possibility – simply had different priorities than others, so something was better for them, not “universally better”?

However, they also reported that a spaced array could match or exceed the sum total of the armoured plates if certain design conditions are featured. Among those conditions are that it should be in most cases only two plates of armour grade material (not construction steel),

What is “construction steel” what is not is not so simple.
Example – Americans designed its STS steel for both construction and protection purposes. Sometimes even the same plate could be counted both as protection and constuction (part of it as “armour” part as “construction”)
After its success, and knowledge about such steel, British designed they Ducol steel for exactly the same purpose, and was very similar in parameters.
British not added this to protection for simple reason - they choose "worst case scenario". So calculated deck armour only, and knew that in real world such deck should perform better, as there is backing, and other decks abowe.

Different fleets had different metodology of calculation. Nothing wrong in it as long as we are aware of it and with "cross country evaluation" use the same criteria for all ships.
Last edited by Maciej on Fri Oct 20, 2017 9:51 pm, edited 1 time in total.

Maciej
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Re: Vanguard and Bismarck

Postby Maciej » Fri Oct 20, 2017 9:49 pm

BTW
Americans used for calulation of deck
0.5*weather_deck + armour_deck + 0.7*backing
So relative for Iowa would be 1.5*0.5 + 4.75 + 0.7*0.5 = 0,75 + 4,75 + 0,35 = 5,85 inch = ~147 mm if we add weather deck
If not - some trajectories were such that shell could omit weather deck and strike just armour deck than = 5,1 inch = ~130

Of course that is very oversimplification of calculation. But considering all unknown areas in armour penetration should be "good enough"
Simple counting too.
The only problem I have is to use the same criteria for all.
Yes I know enough distance for yawing, decapping thickness and so on and so forth.

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Re: Vanguard and Bismarck

Postby Paul L » Sat Oct 21, 2017 2:52 am

As I understand the main reason allies went to single deck armor plate was to defeat bombs, not shells.
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Re: Vanguard and Bismarck

Postby Dave Saxton » Sat Oct 21, 2017 3:41 pm

Backing plates add almost nothing to the effective thickness. The British documented this fact in their live fire testing records. It was found that if there was space between the two plates it actually yielded greater effective thickness than if the main plate was in direct contact with a backing plate. For example, on Iowa, the 120mm main plate and the 19mm backing plate, using the square root of main plate squared plus backing plate squared method, would yield a combined effective thickness of 121.5 mm if the plates were spaced. Add 1/2 of the armoured weather deck and we come to about 140mm. The Americans actually used a short hand method of calculation that fractioned the main plate's thickness and added the backing plate- but it yields the same result. For Iowa: 140 mm. This also takes into account the splinter deck.

We can confirm this by realizing that the designed Iowa outer IZ was 31,000 yards against the West Virginia class 16"/45 firing the extra large cap 2240 lb 16" projectile. The total deck penetration of that projectile and gun combination at 31,000 yards is about 140mm. South Dakota had slightly greater effective thickness than Iowa because the main plate was slightly thicker and the backing plate slightly thinner ( a thinner structural deck able to be used on the shorter length ship).

The Germans also knew that backing plates add almost nothing to the effective thickness regardless of their material quality. The Germans use of WHnA weldable homogeneous armour allowed them to combine structural and ballistic functions in the same plate. They used single armoured plates with no backing plates for each of their armoured decks.

One approach or method of construction is not necessarily better or worse in terms of reaching the design requirements for IZ. The Tirpitz and Vanguard had about 5" effective over the machinery, and about 6" over the magazines using entirely different armour protection schemes. The Iowa/South Dakota also had about same deck protection and outer IZ as Tirpitz and Vanguard.
Entering a night sea battle is an awesome business.The enveloping darkness, hiding the enemy's.. seems a living thing, malignant and oppressive.Swishing water at the bow and stern mark an inexorable advance toward an unknown destiny.

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Re: Vanguard and Bismarck

Postby Maciej » Sat Oct 21, 2017 6:18 pm

Paul L wrote:As I understand the main reason allies went to single deck armor plate was to defeat bombs, not shells.

Both.
Reason was simple. With increasing power of shells allies goes to conclusion that detonation of shells had to keep out of ship.
Multilayer protection was designed in such way to force shell to detonate inside hull but abowe main armour deck. So machinery should be intact but large portion of ship damaged.
With relative medium power of shells it seem ok specially when seen that single plate could not be thick enough to stop shells in expected battle range.
With increased range single plate protection become more practical and with increased power of shell (there was time when 18" and even heavier shells were considered) keeping them out of hull was more important.
If course while hull could not be protected such way so compromise citadel with thick armour and relative soft rest.

In case of backing.
Ok if I'd not important than US battleships deck should be counted similar way.
So Iowa has 120 mm deck South Dakota about 127 North Carolina less than 100....
But interesting that sometimes British give total thickness of armour deck and backing as protection and sometimes armour alone.
Doesn't matter what material wal used for backing.

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Re: Vanguard and Bismarck

Postby Thorsten Wahl » Thu Oct 26, 2017 9:19 am

As I understand the main reason allies went to single deck armor plate was to defeat bombs, not shells.
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