British postwar tests on armor

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spicmart
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British postwar tests on armor

Post by spicmart » Wed Apr 24, 2019 7:38 pm

I heard that there was a British test on armor postwar where German plates were tested and shown that two layers of horizontal armor equal about one single plate of the cumulative thickness, thus proving that the long range horizontal protection was on par with most Allied ships
When exactly were those tests performed, what were the detailed results and is there a primary source?
It seems not very known in some circles.

Thanks.

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Re: British postwar tests on armor

Post by alecsandros » Wed Apr 24, 2019 8:15 pm

You will have alot of digging to do,
but good references can be found in:
ADM213/951 (published 1946)
SUPP 6-481 Underwater performance of shells (1946)
and if you can find it
SUPP 6-910 the penetration of armor plate (1950)

And yes, there are quick references here and there on several naval forums. If you have the time and patience, try digging through Thorsten's posts here on Kbismarck. I'm quite sure he posted several pages from SUPP 6-910 , which is the final (end product) in battleship armor development testing , coming from British research, and which has , amongst other interesting finds, the equivalence of Tirpitz horizontal (2 armored decks of 2" + 4") armor array as approximately 6" of full plate, at most combat ranges.

As for the timeline of the tests forming the basis of the papers, British research into spaced array goes along way back (start of the XXth century IIRC), and continues up until 1948 (at least). My rememberance is that the said tests were conducted after obtaining documents and interrogation reports of German and Italian engineers who worked in the design of Bismarck and Littorio classes, and who provided them with new info about the spacing and thickness requirements for the armor plates, so that the final product (space array) could be effective (most space arrays were not effective, and in any case not as effective as a single plate of the same thickness). Therefore, the probable timeline for the final British tests was around 1946-1948 or so.

Hope this helps,

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Re: British postwar tests on armor

Post by spicmart » Thu Apr 25, 2019 6:04 pm

Thank you. I prefer to have a summary of these things as I do lack the expertise for delving too deep into these matters. What matters to me is that these tests were conducted and the result was that two thin plates equal one thick plate if spaced-array arrangement is done right.

I wonder why some people downright neglect those tests and its findings or plainly don't know about them. Knowledgeable peope that is.
The German armor scheme is frequently talked down as being unsuitable for long range combat.
The primary sources can be used as reference.

Maybe the new book will incorporated these tests.

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Re: British postwar tests on armor

Post by alecsandros » Thu Apr 25, 2019 6:53 pm

It is important to consider that the space array did have it's limitations. Firstly, I think, the quality of the materials used had to be very good (very low impurities). Secondly, the completed array had it's virtues against heavy bombs and heavy shells, which were to be stopped before entering the vitals. It was also good against light shells and bombs, which woudl be (probably/hopefully) destroyed/rendered ineffective by the first armored deck alone. However, for intermediate, or medium sized bombs and shells, the array was not well adapted, as the first deck would produce the triggering of the fuze, while the projectile would travel inside the ship (between the 2 decks), and explode, causing damage in the interspace between first and second deck. It would be the same if a heavy shell or bomb had a short fuze delay.

In any case, my impression so far is that , in 1939, the guns were simply much too powerfull to be stopped by armor , even good armor array. Unless favorable geometry, obliquity of target/plate, and or other factors (weather, sea state, efficacity of electronics, etc) came into play, the ship with the most powerfull gunnery system (and correct fire control) would destroy her opponent (or badly damage it) in rapid mode.

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Re: British postwar tests on armor

Post by HMSVF » Thu Apr 25, 2019 9:25 pm

alecsandros wrote:
Thu Apr 25, 2019 6:53 pm
It is important to consider that the space array did have it's limitations. Firstly, I think, the quality of the materials used had to be very good (very low impurities). Secondly, the completed array had it's virtues against heavy bombs and heavy shells, which were to be stopped before entering the vitals. It was also good against light shells and bombs, which woudl be (probably/hopefully) destroyed/rendered ineffective by the first armored deck alone. However, for intermediate, or medium sized bombs and shells, the array was not well adapted, as the first deck would produce the triggering of the fuze, while the projectile would travel inside the ship (between the 2 decks), and explode, causing damage in the interspace between first and second deck. It would be the same if a heavy shell or bomb had a short fuze delay.

In any case, my impression so far is that , in 1939, the guns were simply much too powerfull to be stopped by armor , even good armor array. Unless favorable geometry, obliquity of target/plate, and or other factors (weather, sea state, efficacity of electronics, etc) came into play, the ship with the most powerfull gunnery system (and correct fire control) would destroy her opponent (or badly damage it) in rapid mode.
How easy would it be repair? Wasn't the KGV arrangement used because whilst the Nelson class inclined belt was clever (all be it a tad shallow) it would have been a bugger to repair?

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Re: British postwar tests on armor

Post by dunmunro » Thu Apr 25, 2019 10:58 pm

The bombing of Tirpitz by FAA Barracuda dive bombers showed the limitations of the Bismarck class deck armour arrangement. One 1600lb AP bomb cleanly penetrated both the weather deck and main armoured deck, while two other 1600lb AP bombs were able to send splinters through the Main Armoured Deck after detonating on contact with it. Each of these 3 hits could have detonated a main magazine had the bomb struck above the magazine because the magazine was directly below the MAD with no intervening splinter decks.

BWOC, post war trials on Rodney showed that a 2000lb AP bomb had to be dropped above 5000ft to penetrate her Main Armoured Deck, which was much thicker (6in versus 4in) than Tirpitz's MAD and Rodney's magazines were two decks below the MAD and had a 1.5in splinter deck directly above them.

It is difficult to simulate a spaced array armour deck armour arrangement and IIRC, test firings against it used inert shells. However, while a 14-16in AP round might not cleanly penetrate the MAD it did have a high probability of sending splinters into the magazine.

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Re: British postwar tests on armor

Post by Byron Angel » Thu Apr 25, 2019 11:34 pm

It is my understanding that the logic underlying the horizontal protection scheme of Bismarck was not so much to defeat the projectile (or bomb) outright, but to introduce such a long distance of travel between the upper armored deck (intended to initiate the projectile fuze) that the projectile would detonate before reaching the main armor deck.

The flaw in this approach was, however, its vulnerability to any heavy projectile fitted with an atypically long fuze delay.

B

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Re: British postwar tests on armor

Post by Bill Jurens » Fri Apr 26, 2019 1:38 am

It is pretty much clear that the resistance of multiple plates in close proximity, or actually touching, will not enhance resistance to penetration except in unusual cases.

The main issues to be considered in battleship type design, and this usually revolving around the relative thicknesses of decks, etc., is whether it is better to place a single thick deck high, which increases protected volume at the cost of stability, a single protective deck low, which leaves a fair amount above the protective deck relatively vulnerable, or whether it is better to separate the plating into two thicknesses, one high to initiate fuzes, etc., and one low to stop the projectile proper and/or associated splinters if the projectile detonates above the lower deck.

An oft-neglected factor revolves around accessibility and repair; one thick plate is usually easier to remove than a collection of stacked laminated plates which usually employ a staggered joint pattern from layer to layer in order to enhance resistance.

Decapping phenomena are usually of relatively little importance, which is one reason why relatively few navies included decapping plates for belt armor.

The 'best' answer probably depends more upon tactical circumstance rather than engineering analysis. One tries to select the optimal scheme to resist the most likely collection of anticipated threats. One, through the vagaries of luck rather than insufficient skill, often chooses wrong, especially in circumstances where weapon characteristics are rapidly changing and ship construction, once put in place, can be very difficult to modify.

Bill Jurens

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Re: British postwar tests on armor

Post by alecsandros » Fri Apr 26, 2019 5:12 am

HMSVF wrote:
Thu Apr 25, 2019 9:25 pm

How easy would it be repair? Wasn't the KGV arrangement used because whilst the Nelson class inclined belt was clever (all be it a tad shallow) it would have been a bugger to repair?
I never thought about that.
Probably difficult to repair, because the horizontal armored decks had both structural and protection functions. Therefore, in order to replace a damaged portion, various compartments would need to be vacated...

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Re: British postwar tests on armor

Post by alecsandros » Fri Apr 26, 2019 5:13 am

dunmunro wrote:
Thu Apr 25, 2019 10:58 pm
The bombing of Tirpitz by FAA Barracuda dive bombers showed the limitations of the Bismarck class deck armour arrangement. One 1600lb AP bomb cleanly penetrated both the weather deck and main armoured deck, while two other 1600lb AP bombs were able to send splinters through the Main Armoured Deck after detonating on contact with it. Each of these 3 hits could have detonated a main magazine had the bomb struck above the magazine because the magazine was directly below the MAD with no intervening splinter decks.
The bomb that penetrated the MAD was a dud, because the forces exerted agaisnt the bomb's body and bomb's fuze were such that it was rendered useless.

The same happened with several bombs dropped against Scharnhorst.

This is a result of the use of Whotan horizontal armor, manufactured with exact specifications for armor array.
Last edited by alecsandros on Fri Apr 26, 2019 5:33 am, edited 1 time in total.

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Re: British postwar tests on armor

Post by alecsandros » Fri Apr 26, 2019 5:16 am

Bill Jurens wrote:
Fri Apr 26, 2019 1:38 am

The 'best' answer probably depends more upon tactical circumstance rather than engineering analysis. One tries to select the optimal scheme to resist the most likely collection of anticipated threats. One, through the vagaries of luck rather than insufficient skill, often chooses wrong, especially in circumstances where weapon characteristics are rapidly changing and ship construction, once put in place, can be very difficult to modify.
Hello,
Re-reading the presentation of Hoyer's 1943 naval armor conference, it is clear that the armor array was considered , at least by the Germans, to offer superior protection to that of a single armored plate of equal thickness.

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Re: British postwar tests on armor

Post by alecsandros » Fri Apr 26, 2019 5:36 am

Byron Angel wrote:
Thu Apr 25, 2019 11:34 pm
It is my understanding that the logic underlying the horizontal protection scheme of Bismarck was not so much to defeat the projectile (or bomb) outright, but to introduce such a long distance of travel between the upper armored deck (intended to initiate the projectile fuze) that the projectile would detonate before reaching the main armor deck.

The flaw in this approach was, however, its vulnerability to any heavy projectile fitted with an atypically long fuze delay.

B
The first idea was to decap the incoming shells, and to reduce the velocity of incoming bombs. The decapped shell should have been destroyed by the MAD, and the bomb with reduced velocity should have detonated before impacting the MAD.
That is what I remember from reading Dr Gercke's interrogation report.

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Re: British postwar tests on armor

Post by dunmunro » Fri Apr 26, 2019 6:55 am

alecsandros wrote:
Fri Apr 26, 2019 5:13 am
dunmunro wrote:
Thu Apr 25, 2019 10:58 pm
The bombing of Tirpitz by FAA Barracuda dive bombers showed the limitations of the Bismarck class deck armour arrangement. One 1600lb AP bomb cleanly penetrated both the weather deck and main armoured deck, while two other 1600lb AP bombs were able to send splinters through the Main Armoured Deck after detonating on contact with it. Each of these 3 hits could have detonated a main magazine had the bomb struck above the magazine because the magazine was directly below the MAD with no intervening splinter decks.
The bomb that penetrated the MAD was a dud, because the forces exerted agaisnt the bomb's body and bomb's fuze were such that it was rendered useless.

The same happened with several bombs dropped against Scharnhorst.

This is a result of the use of Whotan horizontal armor, manufactured with exact specifications for armor array.
The KM report on the bomb in question stated that it appeared to be defective and had been assembled improperly with less than 1/2 the specified burster weight.

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Re: British postwar tests on armor

Post by spicmart » Fri Apr 26, 2019 9:37 pm

dunmunro wrote:
Thu Apr 25, 2019 10:58 pm
BWOC, post war trials on Rodney showed that a 2000lb AP bomb had to be dropped above 5000ft to penetrate her Main Armoured Deck, which was much thicker (6in versus 4in) than Tirpitz's MAD and Rodney's magazines were two decks below the MAD and had a 1.5in splinter deck directly above them.
You don't count the 2 inch upper deck of Tirpitz in?

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Re: British postwar tests on armor

Post by dunmunro » Fri Apr 26, 2019 10:36 pm

I didn't count the 1.5in weather deck on Rodney either. By using such a
thick weather deck the KM was then forced to reduce the thickness of the MAD , probably for topweight considerations.

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