PzIIIH: Layered vs Single Plate Armour - why not in succedding variants?

[Little_Black_Devil]

I've been doing some reading, and reflecting lately on the armour plating as seen on the PzIIIH.

What has me perplexed, is the difference between the Ausf H, and later varriants - which seem to be less armoured - which logicaly seems like a step backwards.

My question for the armour specialists out there is - why?

What is it/was it about the PzIIIH layered armour that, despite its effectiveness - prompted the Germans not to make this type of layered armour common practice?

Why didn't they at least increase the thickness of the single layered plates to an equivilent of the two layered plates to achieve the same level of protection on newer versions of the PzIII?

What were its drawbacks that made it so undesireable so as to convince the Germans not to reproduce on other variants of the PzIII, to say nothing of other tanks and AFVs which incorporated layered armour?

On a side question - can anybody confirm the thicknesses of each respective plate? I've seen it refered to as both 30mm+30mm and 30mm+32mm. Are both correct?

Thanks in advance.

[JasonC]

CMBB in past "builds" modeled layered armor as more effective than a single plate of equivalent thickness. This was probably a mistake, overmodeling the effective thickness by a considerable amount.

30+30 was probably about 50-55mm effective thickness for a single plate, not ~70 as it was modeled before. The Germans switched from 30+30s to 50s because they thought they were getting a comparable level of protection for a lower weight. I am not sure if this is being changed for 103, but it may well be.

50mm uniform was sufficient against Russian 45mms and 2 pdrs. To get adequate protection against 76mm (and other guns, 57mm and Brit 6 pdr e.g.), they went up to 50+20, 50+30, and eventually uniform 80mm plates. The former two thicknesses are probably overmodeled in CMBB for the same sort of reason, though less dramatically so.

[flamingknives]

The layered plates (50mm base with 30mm bolted on) are supposedly effective against the Soviet 76.2mm shell, as the shock of the impact of the first plate sets off the fuse, so the HE charge goes off inbetween the two plate, thus forestalling any further penetration. Doesn't work as well on AP shot .

In addition, after a few hits, the external plate is ripped off, frequently messing up the bolts, making attaching a fresh plate a major engineering job.

[offtaskagain]

Originally posted by flamingknives:

The layered plates (50mm base with 30mm bolted on) are supposedly effective against the Soviet 76.2mm shell, as the shock of the impact of the first plate sets off the fuse, so the HE charge goes off inbetween the two plate, thus forestalling any further penetration. Doesn't work as well on AP shot .

In addition, after a few hits, the external plate is ripped off, frequently messing up the bolts, making attaching a fresh plate a major engineering job.

Partially correct. The 50+30 or 50+20 hull plates on most up-armored vehicles were NOT spaced, only the 50+20 on the turret front of Pz IIIs was spaced. This caused AP rounds with a burster to detonate after penetrating the first plate and fail to penetrate the 2nd plate. This included big rounds like 122mm APHE from an IS-2. The reasons for going to a single plate were easier construction and maintenance. Making one FH or RHA plate is easier than making 2 and bolting them together. In combat the bolts holding the top plate on tended to break when shells impacted and let the plate fall off. I haven't seen any myself, but apparently some pics from the desert show late model Pz IIIs with their applique armor broken off.

[Michael Emrys]

I have heard that the spaced armor broke up the British 2pdr AP shot better than single-plate armor, but don't pretend to be an expert on this subject.

Where's Rexford when you need him?

Michael

[Michael Dorosh]

Originally posted by Michael emrys:

I have heard that the spaced armor broke up the British 2pdr AP shot better than single-plate armor, but don't pretend to be an expert on this subject.

Where's Rexford when you need him?

Michael

Given the verbiage in his posts, I would say probably still typing his response.

[Stalin's Organ]

But it'll be a good one!!

[rexford]

There are two schools on the effectiveness of the PzKpfw IIIH 32/30 layered combo, where the plates were in contact.

British firing tests in Africa showed that the 32mm/30mm face-hardened layered armor was equivalent to a single 69mm face-hardened plate. The only question is whether the tests were conducted with the gun aiming directly at the hull front, or if there was a 30 degree angle from gun to hull facing. Nothing in the report on firing angle (so much for Allied thoroughness).

With a 30 degree side angle, 32/30 resists like one 57mm thick face-hardened plate according to my calculations.

32mm/30mm layered armor on PzKpfw IIIH, and the layered armor on PzKpfw IVG, was a hasty attempt to uparmor tanks. The bolts on the PzKpfw IIIH tended to shear on angled hits, and it became a maintenance headache.

To weld two face-hardened plates together requires that the areas around the edges be free of face-hardening.

Anyway, making two face-hardened plates is a major headache compared to making one face-hardened plate, since that type of armor takes a long time to produce and requires alot of skill.

A single 50mm face-hardened plate may resist with a little less effective thickness than 32/30, but it allows more tanks to be built.

And a 76.2mm APBC round will destroy 32/30 and 50 face-hardened at long ranges if those British tests were at 30 degrees side angle.

[rexford]

Originally posted by Michael Dorosh:

</font><blockquote>quote:</font><hr />Originally posted by Michael emrys:

I have heard that the spaced armor broke up the British 2pdr AP shot better than single-plate armor, but don't pretend to be an expert on this subject.

Where's Rexford when you need him?

Michael

Given the verbiage in his posts, I would say probably still typing his response. </font>

[Michael Emrys]

Originally posted by rexford:

</font><blockquote>quote:</font><hr />Originally posted by Michael Dorosh:

</font><blockquote>quote:</font><hr />Originally posted by Michael emrys:

I have heard that the spaced armor broke up the British 2pdr AP shot better than single-plate armor, but don't pretend to be an expert on this subject.

Where's Rexford when you need him?

Michael

Given the verbiage in his posts, I would say probably still typing his response. </font>

[Bastables]

Originally posted by rexford:

There are two schools on the effectiveness of the PzKpfw IIIH 32/30 layered combo, where the plates were in contact.

British firing tests in Africa showed that the 32mm/30mm face-hardened layered armor was equivalent to a single 69mm face-hardened plate. The only question is whether the tests were conducted with the gun aiming directly at the hull front, or if there was a 30 degree angle from gun to hull facing. Nothing in the report on firing angle (so much for Allied thoroughness).

Lt. Col. H.D. Drew who undertook the tests, carried them out at "broadside/normal impacts" or 0 deg angles unless other wise stated. The first Int Summery dated May 1941 for instance stated in yards the distance for normal impacts (0 deg) vunrability on German Mks I, II, III and IVs and then noted 30 deg engagement ranges for 30mm, 40mm and 45mm armour.

[ May 25, 2003, 12:52 AM: Message edited by: Bastables ]

[rexford]

Originally posted by Bastables:

</font><blockquote>quote:</font><hr />Originally posted by rexford:

There are two schools on the effectiveness of the PzKpfw IIIH 32/30 layered combo, where the plates were in contact.

British firing tests in Africa showed that the 32mm/30mm face-hardened layered armor was equivalent to a single 69mm face-hardened plate. The only question is whether the tests were conducted with the gun aiming directly at the hull front, or if there was a 30 degree angle from gun to hull facing. Nothing in the report on firing angle (so much for Allied thoroughness).

Lt. Col. H.D. Drew who undertook the tests, carried them out at "broadside/normal impacts" or 0 deg angles unless other wise stated. The first Int Summery dated May 1941 for instance stated in yards the distance for normal impacts (0 deg) vunrability on German Mks I, II, III and IVs and then noted 30 deg engagement ranges for 30mm, 40mm and 45mm armour. </font>

[Bastables]

Originally posted by rexford:

[The British tests against PzKpfw IIIH were conducted in Cairo during May 1942. No mention of angle. [/QB]

Still "normal" hits are at 0 deg obliquity, this is how the British tested versus German tanks in Africa 1941. Unless the pattern changed completely in 1942 I think that this still holds true, this practice (O deg as "normal hits") continued in Normandy. The 30 deg standard on the other hand is always suffixed as such, which is the complete opposite of German practice. (30 deg hits are "normal" and 0 deg ones are suffixed).

[ May 25, 2003, 05:15 AM: Message edited by: Bastables ]

[rexford]

Originally posted by Bastables:

</font><blockquote>quote:</font><hr />Originally posted by rexford:

[The British tests against PzKpfw IIIH were conducted in Cairo during May 1942. No mention of angle.

Still "normal" hits are at 0 deg obliquity, this is how the British tested versus German tanks in Africa 1941. Unless the pattern changed completely in 1942 I think that this still holds true, this practice (O deg as "normal hits") continued in Normandy. The 30 deg standard on the other hand is always suffixed as such, which is the complete opposite of German practice. (30 deg hits are "normal" and 0 deg ones are suffixed). [/QB]</font>

[JasonC]

Side angle is not the only interpretation of the 69mm figure. Shatter may also be involved. Indeed, that is what I have suggested in the past, not side angle.

The 57mm figure implies 2 pdr can succeed against the combination - never beyond 500m, and needing limited side angle (around 15-20 degrees) even at 100m - but penetration possible. The 69mm figure implies penetration impossible even with flat hits at point blank.

But it is possible for 2 pdr to fail at the short, low angle ranges even believing the 57mm figure. It is a round of considerably smaller diameter than the plate thickness, hitting face hardened armor. It is entirely possible shatter caused additional failures despite the plate only having the instrinsic strength of 57mm, not 69mm.

The 69mm figure, on the other hand, implies that 25 pdr AP should start failing at 500m, against typical tactical angles (30 degree combined angle). This is not what DAK reported about the effective range of 25 pdrs against Pz III Hs. They report those killed at 1000m, even with the SOP of rotated hulls. Pz IIIs preferred to engage from as far as 1500m, to stay well outside the lethal envelope of 25 pdrs.

The Russian 76mm is rated by practically everyone as having better penetration than the 25 pdr. This is not surprising, as its muzzle velocity is so much higher. The muzzle energies of the two weapons are basically the same.

It seems to me questionable to base estimates of the effectiveness of a given plate against 76mm and 88mm caliber shells on reports of the effectiveness of 40mm caliber shells. The diameter to thickness ratios are so far apart that expected shatter behavior is quite different.

I don't doubt that 2 pdr was particularly unsuccessful against Pz III Hs. But to conclude the reason was multiple plates always adding rather than lowering effectiveness compared to a uniform plate, against any round, is basing too extreme a conclusion (one the naval formula disputes, etc) on too narrow a report.

The evidence supports an entirely different reading - that layered plates resist slightly worse than uniform plates, the second smaller of the two being about 85% effective, as other formulas suggest. That fits the 57mm figure. Some even say you get only 85% of the combined thickness, which would be lower still (around 53mm).

But then the 2 pdr underperforms the raw numbers due to typical shatter problems with high T/D engagements against face hardened armor. Without assuming the Brit tests were conducted at 30 degrees.

Any figure for the combine effect of the two plates that has the Russian 76mm start failing well under 1000m is going to imply the 25 pdr failing even closer in. And we have it straight from the Germans that this just wasn't so, that the 25 pdr killed reliably at 1000m, at tactical side angles. Which means the Russian 76mm should be killing reliably at 1000m.

Which fits 57 or 53 and everyone else's formulas for combined plates just fine, but does not fit 69 and the "layer cake boost" theory. Since right now that theory is making late Pz III fronts invunerable to Russian 76mm down to 500m, making Pz IIs impervious to 45mm, etc, this is rather important. Underperforming 2 pdrs are a slim reed to hang all of that on.

[ May 25, 2003, 04:50 PM: Message edited by: JasonC ]

[Little_Black_Devil]

I'm glad I'm not the only one Rexford.

Thanks for everyone's help - most helpful and informative (as always).

Still though, from certain perspectives it does seem somewhat of an elusive mystery as to why the Germans didn't just stick to the PzIIIH model of layered armour, which would seem to have originally been a stop gap measure.

So far, it would seem to me, that the foremost reasons for moving to a single plate in succedding varriants are the weight issues as well as the shearing/maintenance issue and the time required for face hardening seperate plates.

I'am glad though, that I'm not the only one perplexed by this.

[Bastables]

Originally posted by Little_Black_Devil:

I'm glad I'm not the only one Rexford.

Thanks for everyone's help - most helpful and informative (as always).

Still though, from certain perspectives it does seem somewhat of an elusive mystery as to why the Germans didn't just stick to the PzIIIH model of layered armour, which would seem to have originally been a stop gap measure.

So far, it would seem to me, that the foremost reasons for moving to a single plate in succedding varriants are the weight issues as well as the shearing/maintenance issue and the time required for face hardening seperate plates.

I'am glad though, that I'm not the only one perplexed by this.

One can look to the experience of the Panther story, where before Kursk their were fears that the single FH 8cm glacis would be too thin and attempts were made to bolt/weld extra 2 or 3cm plates. MAN stated that bolting/welding extra FH plates presented extraordinary difficulties and the matter was dropped. The Panther II with 10cm FH glacis armour was then envisaged, and then killed as a development route.

An interesting aside is that the basic 3cm armoured PIIIs were only converted a 1/3 ratio to ausf H 3cm+3cm standard, the rest comming out as 3cm armoured PIIIs with 5cm KwK guns. This 1/3 ratio implies that bolting/welding extra FH plates was a expensive and difficult undertaking best preformed in small figures/batchs, this then precluded up armouring all the by then thin skinned early 3cm armoured PIIIs even in the face of the Russian 7,62cm threat.

Rexford

Not being visesious but I think everyone will feel, adrift throughout their life. Still it does seem that the PIII ausf H was a expencive special case, as were all bolted/welded FH armoured StuGs and Pz?s.

[Bastables]

Originally posted by JasonC:

The 69mm figure, on the other hand, implies that 25 pdr AP should start failing at 500m, against typical tactical angles (30 degree combined angle). This is not what DAK reported about the effective range of 25 pdrs against Pz III Hs. They report those killed at 1000m, even with the SOP of rotated hulls. Pz IIIs preferred to engage from as far as 1500m, to stay well outside the lethal envelope of 25 pdrs.

Yet the British 25pdr tables of engagement for 30 deg oblique stated that only 5,2cm of armour could be penetrated at 500yds. I'd say these ausf H that are being killed at 1000m + are actually 3cm armoured ausf G.

There were only ever 4 to 5 PIII ausf H in Africa at any one time. The capture of ausf H tac number 1102 on the 14 April was one of the few of these rare panzers that were "killed" by guns from the front. That being said 1102 was only penetrated with a front turret hit (3cm armour) at around 500yds from a 25pdr after proving impervious to 2pdrs and 25pdr hull hits.

German SOP was to hit antitank positions with artillery or duels with 7,5cm armed PIVs. Duels with PaKs at 1500m sporting a 5cm weapon seem a height of fancy.

[ May 25, 2003, 06:45 PM: Message edited by: Bastables ]

[JasonC]

If they are a "height of fancy", it is the fancy of the chief of staff of DAK. It is reported from his book on the north african campaign. With decent optics I don't see it as fanciful at all. Desert is very open. A gun at 1500m viewed through 8x sights, or even with 4x sights, should not be all that difficult to pick up.

He is talking about 1942 engagements, and says the short 75mm Pz IVs stood off at 2 km tossing HE, while the IIIs closed to 1500m. He is specifically talking about engaging guns at those distances, 2 pdrs and 25 pdrs, with 50mm from 1500m as well as 75mm at 2 km. They also called indirect arty, of course.

And he says the entire force, which by then included III Js, stayed beyond 1000m to avoid the danger from 25 pdrs, which he says reliably killed any plate, any aspect and angle at that range. The 30mm idea does not make any sense, because the 25 pdr would reliably penetrate armor that thin even at 1500m.

30+30 was not a solution to the threat from Russian 76mm. It was a solution to the threat from 2 pdrs and Russian 45mm - a highly effective solution against both. 50mm single plates also did that job - in the case of the 2 pdr, at practical ranges at least. Against 76mm, then did not consider 30+30 sufficient protection, and quickly went to 50+20 and then 50+30, and uniform 80mm after that.

Which makes perfect sense if you apply the .85 rule. Then those steps were giving roughly 67, 75, and 80 protection, perhaps marginally lower for .95 quality somewhere along the way. The first would then leave the Russians still effective at 1 km, but not beyond that. The second limited them to closer ranges, and the last provided good protection against anything but flat close or very close hits.

The "layers are better" notion, on the other hand, has the Germans adopting an effective armor against 76mm and 25 pdrs at km ranges and then abandoning it for protection only 72% as good (30+30 replaced by 50). Then they adopt a mix with the same bolting maintenance drawbacks they were supposedly abandoning, which gives protection down to 500m flat.

But not satisfied with that for some reason, they use thicker outer plates on heavier vehicles, giving complete invunerability from the front. Still bolted. Finally they relax that to get uniform plates again, reducing protection to get that supposed advantage.

This is a pretty silly sequence for supposedly reasonable people to go through. It certainly is much harder to believe than the monotonic increasing protection until the enemy gun is finally outmatched seen by the rival, 0.85 estimate of layered plate effectiveness.

As for additional plates on Panthers as impractical, of course they were impractical. They would be a large addition of weight, up front, and the early Panther overstrained its engine already. As for factory uparmoring, many plate conversions were done in the field rather than at the factories.

The Germans did not consider bolted armor so impractical for production reasons that they didn't use it, not just once, but 3 successive times. But they got away from it after each time, as soon as a uniform plate of comparable protection could be used instead.

This suggests it did not increase effectiveness for the weight but reduced it. Higher protection from greater overall thickness was worth the hassles of bolted armor. It was a matter of rendering 37mm to 45mm guns ineffective (for the 30+30 step), or increasing protection against 75mm to 88mm ones in the case of the 50+20 and 50+30 steps.

But the extra weight of bolted layers compared to uniform plates was not worth it - because it protected less efficiently, not more efficiently. Everyone else's formulas says as much, and all the tactical and production evidence agrees.

The only thing on the other side is reading tons into a report of the ineffectiveness of 2 pdrs against 30+30. It is much more likely the 2 pdr underperformed in that match up due because it faced high T/D and face hardened armor, leading to shatter problems, than that all the production moves and tactical testimony about larger guns is completely wrong.

Why did no one before CMBB notice that Pz III Js and L are invunerable from the front down to 500m, not to US 37mm but to Russian 76mm, and layered StuGs are invunerable at all ranges, Pz IIs invunerable to Russian 45s, etc, etc. Layered boosting just has too many ahistorical implications. There is no need for so strained a notion, to fit the data.

[Bastables]

Originally posted by JasonC:

If they are a "height of fancy", it is the fancy of the chief of staff of DAK. It is reported from his book on the north african campaign. With decent optics I don't see it as fanciful at all. Desert is very open. A gun at 1500m viewed through 8x sights, or even with 4x sights, should not be all that difficult to pick up.

He is talking about 1942 engagements, and says the short 75mm Pz IVs stood off at 2 km tossing HE, while the IIIs closed to 1500m. He is specifically talking about engaging guns at those distances, 2 pdrs and 25 pdrs, with 50mm from 1500m as well as 75mm at 2 km. They also called indirect arty, of course.

Really? Nothing I have on General Gause has him purporting any such thing as a SOP; Von Luck the recce commander says nothing about this either. He certainly did not on sighting dug in enemy anti tank guns cry; " Avast! The bounders have dug in 25pdrs of doom. Call Pz Regt 5 so that they may carry out a fair duel with the scoundrels a 1500m." as opposed to any thing tricky like bypassing or killing them with artillary. This sort duel with dug in guns reaction was the thing that British tank sqns were famous for during 41, 42.

It?s interesting that ausf H now turn into ausf J...

During Torburk the 25pdrs only started scoring kills when Pz regt 5 in a fit of idocicy decided to drive parallel to enemy positions looking for a break in the fortifications.

This is also a theatre where the usual "killing" range of the long range 8,8cm FlaK is 800m, long range shooting in the deserts was problematic, both sides encountered large difficulties in range estimation, the PaKs and dug in guns generally being better off than magnified telescopes on the panzers/cruisers.

[ May 25, 2003, 09:43 PM: Message edited by: Bastables ]

[Bastables]

Originally posted by JasonC:

As for additional plates on Panthers as impractical, of course they were impractical. They would be a large addition of weight, up front, and the early Panther overstrained its engine already. As for factory uparmoring, many plate conversions were done in the field rather than at the factories.

Some proof would be nice since bolting/welding of plates to StuGs, PIV and PIII was always carried out during factory rebuilds or they came out of the assembly plants with plates attached.

Hell the Germans being the Germans had Waffenamt authorise or null acceptable field mods for such minor concern such as welding handles to the rear turret hatch of the Panther and bigger things such as concrete reinforcement of 3cm front angled plates on the StuG, yet the troops were never authorised to weld bolt extra FH or even RHA armour onto their Panzers.

The Panther engine seemed fine driving the Tiger and the two prototype 50 ton Panther II chassies around, they even ended up decreasing the revs from 3000rpm to 2500rpm without any loss in speed in the ausf D Panthers.

[ May 26, 2003, 12:31 AM: Message edited by: Bastables ]

[Bastables]

Originally posted by JasonC:

Why did no one before CMBB notice that Pz III Js and L are invunerable from the front down to 500m, not to US 37mm but to Russian 76mm, and layered StuGs are invunerable at all ranges, Pz IIs invunerable to Russian 45s, etc, etc. Layered boosting just has too many ahistorical implications. There is no need for so strained a notion, to fit the data.

Look to the jump in kill ratios during 42, 43 when 76,2cm armed T-34s failed in combating PIII lang, PIV langs and StuG lang, all veh up armoured with appliqué armour to defeat the 76,2cm round. Even late 42 during Operation Mars the Pz divs with their mix of PIIIs and PIVs proved all too capable of gutting T-34 formations with little loss. The same exaggerated kill ratio was exhibited again at Kursk with mainly late PIV and PIII formations versus 76,2cm armed T-34s. Read Glantz, Zetterling and Jentz.

[Bastables]

Originally posted by JasonC:

3The only thing on the other side is reading tons into a report of the ineffectiveness of 2 pdrs against 30+30. It is much more likely the 2 pdr underperformed in that match up due because it faced high T/D and face hardened armor, leading to shatter problems, than that all the production moves and tactical testimony about larger guns is completely wrong.

Bull****,

The 2pdr managed to punch through 6cm of bolted PIV RHA armour at 500yds in tests carried out by 5 R.T.R 4th june 1941. T/D ratios are irrelevent at such low levels. Two FH plates are stronger, two RHA plates are weaker.

[rexford]

Jason C posted the following:

"It seems to me questionable to base estimates of the effectiveness of a given plate against 76mm and 88mm caliber shells on reports of the effectiveness of 40mm caliber shells. The diameter to thickness ratios are so far apart that expected shatter behavior is quite different."

The British tests against the front of a PzKpfw IIIH were previously described in detail on this site, maybe even on this thread, and included the following guns and ammo:

U.S. 37mm APCBC

British 2 pdr AP

British 6 pdr AP

U.S. Grant 75mm AP

U.S. Grant 75mm APCBC

German PzKpfw IV 75mm APCBC

So Jason C's conclusion that all of the 69mm stuff against 76.2mm and 88mm ammo is based on a few tests with 2 pdr AP ammo is not the case.

[rexford]

Jason C has posted:

"The 69mm figure, on the other hand, implies that 25 pdr AP should start failing at 500m, against typical tactical angles (30 degree combined angle). This is not what DAK reported about the effective range of 25 pdrs against Pz III Hs. They report those killed at 1000m, even with the SOP of rotated hulls. Pz IIIs preferred to engage from as far as 1500m, to stay well outside the lethal envelope of 25 pdrs."

Please reference the above statement and give us the exact words if possible, because the above post could be very important and help resolve the issue.

According to our calculations, the North African 25 pdr AP could penetrate 60mm face-hardened at 1000m, which would fit 57mm resistance from the 32mm/30mm face-hardened in-contact combo.

Advanced Squad Leader indicated that about 325 PzKpfw IIIH were produced, and other PzKpfw IIIG were uparmored by adding extra plates. It would seem that more than a handful could have been in Africa at one time.

The wargame TOBRUK (May 1942 battle) had all PzKpfw III as Ausf H if I remember correctly, which I always thought was a slightly optimistic view.

So if Jason C would be so kind as to reference his statement on 25 pdrs vs PzKpfw IIIH we might have resolution this week.