Then we began to talk about the merits of sloped vs vertical armour (I know, exciting right...). As I've just read a presentation to a large gathering of armour officers about this very subject I figured it'd be good to make an article on it. So what follows is a non-mathematician trying to explain a horribly complex subject (and we all saw how well that went in the nuclear bomb article).
It is a commonly held belief that sloped armour is better than vertical armour, this isn't strictly true (some claim it isn't even slightly true). Equally it's often claimed that the Russians invented sloped armour on the T-34. First of all let's address the last point and consider what the claim is saying, that every engineer between the ancient Greeks (I'm using Greeks, as Pythagoras' measurements of triangles are the one most used in later on in this article), and the Russian designer of the T-34 had forgotten or were never taught the maths that make up geometry. Yet tanks before and after the T-34 continued to be made with flat plates... why? Maybe it's because flat armour isn't as bad as many claim, if not superior. Consider this, if sloped armour is so inherently superior why do modern tanks use fairly shallow angles on their front plates, and some like the Leopard 2, use none?
|Its a Tiger!|
|The Sherman is narrower than the T-34, yet the Sherman could carry the bigger gun.|
But what of the armour itself? An example given in the paper I mentioned is a 100mm vertical plate vs a German KwK 42 L/70 75mm, the gun most famously mounted on the Panther, at 2000 yards. At that range the KwK 42 could penetrate 104mm, and so beat the 100mm vertical plate by 4mm.
But what if we slope it?
Well to cover the same area, at say 30 degrees, the plate now weighs more. Before you all grab for calculators scratching your head or reach for the comment button, remember the missing part is the roof and thus normally much thinner and lighter, and is a different calculation and balancing act for the designer. We're just talking about the ability to protect fire from the flanks. Most people when working this out have the “roof” of the triangle the same thickness as the sides for simplicity. However even the newest student of armour design can spot that the idea of having a 100mm thick roof is a bad idea. (Note: I'd actually be interested in seeing a comparison of weights and thickness that includes the difference in thicknesses of side and roof plates)
So using the same weight of armour means you could get, 80mm of armour at 30 degrees. The same gun at the same range as used before has a penetration of 89mm. So you're actually worse off as the gun has beaten you by over twice the margin of the vertical plate.
|Yeah, now go down the slope and the angle decreases, and add in a ballistic curve to the shot.|
So in summary, a vertical plate will always give its designed level of protection, and may actually give more. It's also technically (possibly?) lighter. With that in mind why are modern tanks not universally square? I honestly have no idea, it is reported that sloped armour is actually harder to spot, and blends into the background better than a square tank, and that right angles show up really well to radar. There's also a question of crew morale, as sloped armour is seen as better. So if you ever see another “design your own tank” competition, give the poor humble vertical plate another chance!
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