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The reasoning behind vertically shaped armor?


curious1234

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During the "Operation Think Tank" Q & A session with Nicholas Moran and other tank experts, when they were asked about why armor wasn't sloped was up to a point in time the answer was because of how sloped armor limits the useful space inside the tank.

According to Ralf Raths from Deutsches Panzermuseum the reason German engineers didn't use slopes was because they thought a sloping plate might get ripped off when hit because it's attached to other sloping plates and can't be strongly held in place, while a vertical or only slightly angled plate can.

Was this a real problem or was it only imagined? Was this the reasoning in other nations aswell? Was there an invention that made it possible to angle the armor much more?

 

Edited by curious1234
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Weakly sloped armor was never efficient. Welds breaking etc. isn't an issue, as the welds are longer the more slope you have, and in a deflection there is less transfer of momentum. Thin sloping armor isn't very good vs lowish velocity HE though, at least if it fuses, because the HE charge itself can break a thin highly angled plate even if it is enough to deflect the round on delay, and in the early periods a common threat (or perceived threat) is going to be infantry guns and medium field guns etc. firing HE, as dedicated AT guns are somewhat rare. But by the start of WW2 these considerations should have held basically no weight.

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I wonder what he means by "strongly held in place". Did he mean riveting plates to a frame? You can make a frame to attach sloped armour to, easily. Welding sloped plates together? Well that isn't a problem, for either sloped or flat armour. The way it's described, it's nonsensical. Could you maybe give a direct translation of his own words, so that we could understand the context better?

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Sloped frontal armor wasn't unusual, see various British, Soviet and French tanks. So not doing it because of internal volume makes sense. Panzer III got good grades in that regard from Nick. 

As far as Ralf's statement goes, could you link the Youtube clip, so I can listen what he says?

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4 hours ago, Interlinked said:

I wonder what he means by "strongly held in place". Did he mean riveting plates to a frame? You can make a frame to attach sloped armour to, easily. Welding sloped plates together? Well that isn't a problem, for either sloped or flat armour. The way it's described, it's nonsensical. Could you maybe give a direct translation of his own words, so that we could understand the context better?

"Strongly held in place" was my phrase, sorry for confuding you. English isn't my first language.

5:10 min here: https://www.youtube.com/watch?v=w3oUeIZ5ieU

My question was whether this was the reasoning among other nations engineers aswell. Even if flat armor creates a lot of internal space it's still strange to me why the front armor wasn't at least sloped. Take a Pz III for example, it looks like the glacis plate could've easily been sloped from the roof to the nose plate and it wouldn't have made the tank that much larger or decreased the useful space inside.

Edited by curious1234
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Yes, that is about the structural integrity of the chassis. The idea was that angled plates would be dislodged easier and not to forget the German doctrine expected the whole to tank to be angled by the crew.   

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1 minute ago, seahawk said:

...and not to forget the German doctrine expected the whole to tank to be angled by the crew.   

Life is not WoT. That assumes crew knows where exactly ATGs are, which is usually wishful thinking until they start firing, when it is usually too late.

Edited by bojan
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23 minutes ago, curious1234 said:

My question was whether this was the reasoning among other nations engineers aswell.

Even if flat armor creates a lot of internal space it's still strange to me why the front armor wasn't at least sloped. Take a Pz III for example, it looks like the glacis plate could've easily been sloped from the roof to the nose plate and it wouldn't have made the tank that much larger or decreased the useful space inside.

WAG: Other nations had more experience with tank design and construction because they weren't severely restricted by something like the Versailles Treaty. 

I wonder what level of protection the Germans were initially looking for. With 30mm plates probably just against HMG and maybe 20mm autocannons. If you angle that 35°(primary) you get the equivalent of 50mm but you do loose volume at the front. https://panzerworld.com/relative-armor-calculator 

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Right the alleged argument of the anti-sloping engineers is that on non-sloping plates the side plates can be directly behind the front plate, and the force after a hit is transmitted largely by compression forces and barely at all by shear. It isn't a good argument, but the presenter is only saying that that is what was given at the time, and he even agrees that it isn't very good.

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5 minutes ago, KV7 said:

Right the alleged argument of the anti-sloping engineers is that on non-sloping plates the side plates can be directly behind the front plate, and the force after a hit is transmitted largely by compression forces and barely at all by shear. It isn't a good argument, but the presenter is only saying that that is what was given at the time, and he even agrees that it isn't very good.

It's strange to me that they didn't just do some tests to see if it was true before letting a theory influence design.

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1 hour ago, seahawk said:

Who says they did not? I am guessing the concern was mostly about hits by HE.

Well against HE the argument is invalid, because the force from the HE charge is always roughly normal to the plate, no matter the slope. But as above for the same areal density, the sloped plate will be thinner and more susceptible to breaking. But also sloping also partially replaces thin roofs with thicker glacis plates etc. so the performance of sloped plate is actually usually better vs plunging HE.

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27 minutes ago, KV7 said:

Well against HE the argument is invalid, because the force from the HE charge is always roughly normal to the plate, no matter the slope. But as above for the same areal density, the sloped plate will be thinner and more susceptible to breaking. But also sloping also partially replaces thin roofs with thicker glacis plates etc. so the performance of sloped plate is actually usually better vs plunging HE.

So you're saying that it doesn't make sense to use vertical shapes when making armor thick enough to resist HE and make the plates as short as possible to reduce weight, because even if you make the vertical glasic plate on, say, a Pz III thick enough, the thinner plate covering the transmission will be vulnerable when the glacis is hit?

Edited by curious1234
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14.5mm armor on early Pz III/IV - vs small arms with AP bullets, 30mm armor - vs 20mm guns.

8 minutes ago, curious1234 said:

So you're saying that it doesn't make sense to use vertical shapes when making armor thick enough to resist HE and make the plates as short as possible to reduce weight, because even if you make the vertical glasic plate on, say, a Pz III thick enough, the thinner plate covering the transmission will be vulnerable when the glacis is hit?

Yes. Sloped armor has same weight for a same equivalent thickness as vertical one (basic trigonometry), but vertical one also needs horizontal plates which add more weight and also contribute to the vulnerability vs HE. You can not save weight by using vertical armor, which is why it generally* went the way of dodo.

*Modern "slab sided" tanks like Leo 2 before A5 upgrades and such still have internal structure of the composite armor that heavily uses sloping, through with different idea than standard sloping armor).

Edited by bojan
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That is wrong if you want the same interior volume. And if you look at the PzIII the decision is quite obvious, as the hull escape hatches needed be to be placed somewhere and would make a big weak spot if integrated into one sloped plate. The same goes for the transmission and brake hatches  as well as the escape hatches on the Pz IV.

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No, front sloped armor can be as affective with internal space as is vertical, but vehicle has to be planned with it from the onset, not to be a conversion of vertical armor existing one. It was side hull sloped armor that limited internal volume seriously, and for that reason it was also mostly ditched post-WW2.

Edited by bojan
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Speaking of sloped armor, how much effect does very slight angling have on anti-tank shells? Like the 9-10 degrees on the hull front on early German tanks or Tiger II's turret.

Since a choice has been made to angle the armor even if it's only that I imagine it must've made a some difference.

Edited by curious1234
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On the IS-3 and T-10 the sloping side armor was quite efficient space wise as the sloping was bulging outwards and over the tracks from the lower hull, which was necessary to allow a larger turret ring without the hull itself becoming very wide. The T-54/55 layout was not better for space efficiency, but it was much easier to produce.

The T-34 and Panther style deep inward sloping of the upper side armor became infeasible with larger turrets and had no rationale with lower hulls.

Edited by KV7
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Quote

Speaking of sloped armor, how much effect does very slight angling have on anti-tank shells? Like the 9-10 degrees on the hull front on early German tanks or Tiger II's turret.

Since a choice has been made to angle the armor even if it's only that I imagine it must've made a some difference.

Practically no effect, either positive or negative. It is simply too small of an angle. 

Quote

So you're saying that it doesn't make sense to use vertical shapes when making armor thick enough to resist HE and make the plates as short as possible to reduce weight, because even if you make the vertical glasic plate on, say, a Pz III thick enough, the thinner plate covering the transmission will be vulnerable when the glacis is hit?

That's absolutely right. One of the problems with using stepped shapes is that a HE shell impacting on the recessed step can blast through the thin joining plate. For instance, if you fired a HE shell at the side hull of a Pz. IV, it can burst through the thin sponson floor, and if you fired a HE shell at the upper glacis, the shell can burst through the thin roof plate over the transmission. This isn't just a hypothetical situation, it's a real issue. To solve it, you increase the thickness of that roof plate, but by doing that, you are adding more weight to solve a problem you would never have had if you used a sloped front hull shape instead.

Overall, vertical plates do not give any constructional advantages over sloped plates, but bring a number of drawbacks and inefficiencies in terms of volume and weight.

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