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Justin S.

'Curved' armor tests

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Soddball and I are going to test to see how curved armor affects the general survivability and protection levels of the german tank destroyers in both CMBB and CMAK. I would also like to determine if the *estimate* (by JasonC and others) of the random angle generated by curved armor (30 deg. roughly) is accurate.

To do this I will create a flat, open ground map of ten "firing lanes" sperated by a LOS block- Nine ridge lines. In those lanes I will place a Hetzer (60mm front plate 'curved') behind no cover, at range opposite of it, and at the same elevation and aspect angle (to avoid oblique angles confounding data) an allied tank (both will be bogged and only the allied tank will have ammunition- i will only be counting upper hull hits- i chose not to place Hetzer hull down as this isnt a turret/mantlet test, and i didnt want low hit percentages being a problem). To enable a direct comparison with Soddball's experiment (and to try and find a noticable change from CMBB to CMAK) I will initially use a 75mm Sherman (i intend to also test Sherman 76, using varying rounds, and also the T34/85). I will be sure to note date and round type for each test and AVF type. Using the values in the unit screen for which ever AP type it is carrying at the momment, I will place the Sherman at a distance where its maximum penetration value is *equal* to the protection level of 60mm armor sloped at 30 deg. This is easily done because the gun data menu gives values for that angle of impact and i would graph it parabolicaly (with a best fit equation on a TI-83+) to find a more precise intersection point- the point where the effective armor resistance and penetration values are nearly identical. The reason for this is that if 30 deg is in fact the average randomly generated angle, then i would get a rough distribution curve that was measurable by counting the type of hits. If 30 deg is average i should get a significant number of 'partial penetrations', because the armor protection level would be very close to the rounds penetration ability. If the estimate is accurate it should also produce similar numbers that fail to penetrate as those that fully penetrate. Obviously we cant determine by how much the rounds succeed or fail by, but this is a more general test and Ill leave the higher theory and grog work to Lorin or Tittles.

I plan to record at least 100 upper hull hits on the Hetzers (from each AFV and ammo type) at the stated range. I will record ricochets (to see if JasonC's 1/6 figure is accurate) round failures (because i wont have the data for by how much ill lump them together- same for full pen.), full penetrations, and partial penetrations. Hopefully at 10 Hetzers per test, this should go reasonably fast.

After I get the data from my tests i will post it here in a makeshift, easy to read, 'chart' smile.gif

Combined with Soddballs data not only will we be total armor nerds, we might have established a fairly accurate proof of the average random angle generated by curved armor in CMBB and CMAK. Stand by for the numbers... (it might take a couple of days)

Soddball- It might be good for you to conduct the same type of experiment so that we have comparible data. Let me know if you think ive got something wrong, or you disagree. Also any other members are more than welcome to offer suggestions and criticism to testing methods.

EDITED to correctly spell Soddball.. 4 times redface.gif

2nd EDIT: rexford in fact did not put forth the 30 deg. estimate, so i removed his name from that association.

[ September 10, 2004, 07:50 AM: Message edited by: Justin S. ]

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I seem to recall somebody saying that 'curved' armour differs greatly from tank to tank.

For instance, despite both the Stug 80mm armour and the Jagdpanther 80mm armour being described as 'curved' the level of protection they offer is very different.

If true, would that mean that your tests are valid only for Hetzers and no other 'curved' armour tank/tank destroyer?

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Justin, I'll set the tests up identically.

Some tips:

You can create 'immovable' vehicles by placing the vehicle on a grass tile in the map screen in the editor, and then placing a rough tile on top of the grass tile.

Hetzers are vulnerable to lower hull hits at many ranges. You'll probably lose half your Hetzers in the first firing round which will make obtaining the results tiresome, to say the least. smile.gif

You should bear in mind that you can reduce the incidence of this by placing the Hetzer 'hull down' on a piece of slightly-sloped ground but I'm not sure how this will influence the tests.

Given that tank commanders would (I assume) have sought a hull-down position it's not unreasonable to use it.

What range are you going for? 800m between each tank?

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Well, i just spent an hour running the test with over several hundred hits... the results where very surprising and frankly, quite disappointing.

I set up the test as i mentioned above, and added the rough terrain to make the ammoless Hetzers stay put. The parameters where as follows:

July 1944, Combined theaters, Mid Day, Dry, Cool, Still.

Ten Sherman 75L38 firing APCBC down range at Ten Hetzers (all regular crews).

All Shermans where 999 to 1000 meters from the Hetzers at 1st go- this is the stated range that the Shermans would penetrate 60mm of armor at 30 deg. from vertical.

After watching two full turns of literally NOTHING but upper hull ricochets, i moved the range to 950mm for all the Shermans. Again, same thing. The occasional lower hull hit would cause internal flaking- that was it. I stopped tallying on the paper at this point because out of 57 upper hull hits, 54 where ricochets, the other 3 being gun or track hits.

I continued this method all the way down to 100 meters. NO, repeat, NO penetrations occured against the front upper hull of the Hetzers. In CMBB the Hetzer is impenetrable by the 75L38 at *ALL* ranges on the upper hull.

Conclusions: As Glider said, the 'curved' declaration may be diferent for each AFV. If this is the case, then the hypothesis for an all- inclusive average generated angle is out the window. Clearly, it is not 30 degrees in the case of the Hetzer. Note that i am assuming that the ricochet property is directly related to angle of impact and is not a seperate varible than can be adjusted. Im curious to see what Soddball's data for CMAK shows (i just realized i had been typing 'sodball' this entire time- sorry). Thanks for everyones input and I have the saved games and scenario set-up if anyone wants a second look.

Next up: Id like to test out the Panther's mantlet/turret against late 1944 T-34/85 and see if going hull down is *statistically* advantageous in regards to reducing penetrations. Two main factors will be covered- Hit percentages against Panther (hull down vs exposed), contrasted with percentages of penetration. In other words, does the reduced enemy hit percentage of going hull down in a AFV with a superior glacis produce a higher survival rate than the same tank exposed?

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It is easy to see in CMBB, the Jagdpanther 80mm 'curved' armour offers a dark blue level of protection, while the Stug 80mm 'curved' armour offers a light green level (easily penetrated by 85mm Russian guns).

IIRC, somebody mentioned that the actual algorythm used to describe the 'curved' armour is rather more complex than it appears and includes size of mantlet, shot traps and actual more/less vulnerable areas for each 'curved' armour section for each tank type separately.

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Importantly, Justin, you're seeing exactly what, IMO, should happen. The Sherman 75 should not penetrate the Hetzer at any point from the front.

This was an issue with CM:BB when I first got it (search for 'curved hetzer') and you'll bring up a thread on this. 1.00 and 1.01 versions of CM:BB had realy 'curved' armour issues and by 1.03 these issues had disappeared. I imagine that the CM:AK data came across with CM:BB 1.03.

One important factor to bear in mind for the Germans is that all their tanks seem to have been developed with the Eastern Front in mind - the Western Front was very much a secondary consideration. Witness wider treads to handle the foul conditions in Russia, for example. You might therefore expect the German tanks to produce more significant results facing off against T34s and JS tanks.

If you want to do the Panther, that's fine by me. I'll run some tests with the Firefly because that's not in CM:BB (and because I like Fireflies smile.gif ) to see what its effectiveness is like against the Hetzer, and if you want some CM:AK tests run against the Hetzer let me know.

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I had a crack at four dozen ammoless, dug in Hetzers with a dozen T34/85s

At 500m, with a hit chance of 96% (elite crews coupled with boresighting) 71 shots (between 5 and 7 shots each) produced 8 ricochets, and 30 Hetzers rendered combat-ineffective through KO or gun damage.

At 1000m, a hit chance of 77% (same deal as before), a comparable number of shots produced similar numbers of partial penetrations and ricochets. 12 Hetzers were rendered combat ineffective.

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Originally posted by Glider:

It is easy to see in CMBB, the Jagdpanther 80mm 'curved' armour offers a dark blue level of protection, while the Stug 80mm 'curved' armour offers a light green level (easily penetrated by 85mm Russian guns).

IIRC, somebody mentioned that the actual algorythm used to describe the 'curved' armour is rather more complex than it appears and includes size of mantlet, shot traps and actual more/less vulnerable areas for each 'curved' armour section for each tank type separately.

If you played CM:BO, you'll remember that the Jagdpanther was pretty much invulnerable against anything up to a Firefly (unless you hit the 'armour flaw') and the Jagdpanther's vulnerability was noticeably higher in CM:BB. It would be interesting to see if this, too, was still the case in CM:AK.

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...If you played CM:BO, you'll remember that the Jagdpanther was pretty much invulnerable against anything up to a Firefly (unless you hit the 'armour flaw') and the Jagdpanther's vulnerability was noticeably higher in CM:BB. It would be interesting to see if this, too, was still the case in CM:AK. [/QB]
I played CMBO and CMBB but all I learned (at least from actual games as opposed to penetration tables) about Jagdpanthers was to avoid them until they present me with a flank shot smile.gif

Just checked CMAK, tungsten-armed Firefly has low - very low chance of killing a hull-down Jagdpanther head-on at 700m. It is interesting to note that the kill chances varies drastically as soon as you move the Firefly several degrees off 90-degree head-on angle and this (from my experience with the CM series) means that you need a really lucky hit to kill a JP.

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Hetzers in CMBO were swines when they turned up against 17pdr guns. The glacis was just thick enough to defeat the 17pdr. If CMBB treated the glacis as a single 60mm plate, the 85mm gun would have the same problem, going by the given numbers.

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There are two types of curved armor on tanks, in general.

Many mantlets assume a circular shape, going from a 0 degree from vertical angle at the center to close to 80 degrees from vertical at the upper and lower edges.

And there are the rounded mantlets (Saukopf) where the angle goes from 0 degrees from vertical to a high value very quickly.

For the Panther mantlet, assume a half circle, and the following impact angle distribution applies for even spread of shots across the height (vertical resistance to 17 pdr APCBC hits is in brackets and is taken at angle half way thru angle range, and cast armor resists with quality factor of 0.95 so 100m cast = 95mm rolled):

9% strike at 5 degrees or less (95mm vertical)

8% at 5 to 10 degrees (96mm)

9% at 10 to 15 degrees (98mm)

8% at 15 to 20 degrees (101mm)

8% at 20 to 25 degrees (106mm)

8% at 25 to 30 degrees (113mm)

7% at 30 to 35 (124mm)

7% at 35 to 40 (138mm)

7% at 40 to 45 (158mm)

6% at 45 to 50 (186mm)

5% at 50 to 55 (226mm)

5% at 55 to 60 (282mm)

4% at 60 to 65 (359mm)

3% at 65 to 70 (467mm)

3% at 70 to 75 (602mm)

1% at 75 to 80 (824mm)

2% at 80 to 85 (1324mm)

0% at 85 to 90

If 17 pdr APCBC hits are evenly spaced across the vertical height of the Panther mantlet, there is no side angle from gun to armor facing and the round penetrates 160mm at a given range, 29% of the hits will have less than a 50% chance of penetrating, about 25% will never penetrate and about 57% or so will always completely penetrate.

Note that the 30 degree resistance is not a good model for the rounded mantlet resistance, because using 30 degrees results in an estimate of 113mm which is penetrated all the time by 17 pdr APCBC and U.S. 76mm APCBC hits, while using the full angle complement results in less than a 100% success rate. I never said 30 degrees was a good angle to use for rounded armor and have always suggested that a distribution be used.

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Originally posted by flamingknives:

Hetzers in CMBO were swines when they turned up against 17pdr guns. The glacis was just thick enough to defeat the 17pdr. If CMBB treated the glacis as a single 60mm plate, the 85mm gun would have the same problem, going by the given numbers.

Yeah, I just checked, at 700-800m the game gives 'OK' kill chance to 17-pounder Fireflies with tungsten ammo against hull-down Hetzers, but when I tried all 5 hits the Fireflies managed to score bounced.

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Don't test with the tungsten shots against Hetzer or Jagdpanther.

They lose penetration quicker with angle than APC. Against high-angled armor they have the same or less penetration and less after-armor effect.

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The cast mantlet on the Hetzer, JagdPanther and StuG IIIG appears to present an inpenetratable angle to incoming rounds over most of the area that would be hit on a frontal shot with no side angle.

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Originally posted by rexford:

... I never said 30 degrees was a good angle to use for rounded armor and have always suggested that a distribution be used.

Great distribution and it really made the physical aspect a bit clearer to me.

But why various curved armour sections in CMBB (and CMAK, I guess) offer different levels of protection? The most radical example being 80mm curved Jagdpanther against 80mm curved Stug... in-game the Jagdpanther curved armour feels like it offers almost twice the protection.

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For CM armor "curved" basically means "variable slope". The angle distribution table most often found in this forum is ok for armor plates that are basically vertical, which is often ok for turret fronts with a rounded gun mantlet.

But for vehicles like the Hetzer or Jagdpanzer, we have front upper hull slopes of somewhere between 45° and 60° depending on the exact model. So we have a default slope of 45° to 60°, and this value is varied for some hits (close to the gun). So even if the Hetzer front plate is listed as curved, most of it is angled at 60°, which will bounce your 75mm shells.

So you have to take a look at the slope value of a certain plate, too.

Dschugaschwili

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But we have no slope value for upper hull in info screens... we just have the term 'curved'. So, the only way to know how effective, for instance, the Stug IV 80mm 'curved' armour is - is to play a nummber of games and see that it simply cannot stop Russian 85mm shells.

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I tried an experiment similar to this not long ago, using first vanilla shermans and then t-34/85 m43s in CMBB v 1.3, with the tanks firing at first 500 and then 300m against dug-in targets. The Jagdpanzer IV and Hetzer seemed to do equally well against shermans, though GtuG IIIGs did substantially more poorly than either. Strangely, the kill probability for a t-34/85 against a Hetzer read 'none', though if the tank was manually given a Hetzer as a target it would fire and often kill on the first hit.

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First I like to clear up some errors. Going back and reading through the threads on curved armor it appears that all of them tossing around the "30 deg." idea are prior to patch 1.03. Also, i apologize to rexford. He is quite right when he says he never advocated using the 30 deg average- He was posting in the same threads but never gave it his approval. The majority of talk about 30 deg. came from JasonC, whom i typically think is fairly reliable- To his credit this was pre-1.03 and things may have changed greatly, i dont know. However, even if things changed in 1.03, the common perception sure didnt. If you go back and review even this thread, and especially the "Seeking final word on mantlets" thread, I think youll find why i felt the need to test out the effects of curved armor, especially the Hetzer.

Redwolf:

the vulnerability of the Panther, and the joke that Jagdpanther, Hetzer and Jagdpanzer IV became when they got curved armor indicates that it returns low angles very often.

Soddball:
Units such as the Hetzer, which were extraordinarily hard to kill in CM:BO, have been affected by the 'curved' armour which really negates their biggest advantage. It's a shame, because with 'curved' armour it's nearly impossible to use the Hetzer as it would have been. Personally I think it was an error to implement the 'curved' option for the Hetzer, because it's taken it from a tough, rounds-bounce-off TD to a slow-to-turn, slow-reloading, narrow-arced mobile pillbox that'll crack off maybe one shot before it gets toasted by a 75mm Sherman.

Soddball also mentioned how rare it is to see the TD's being played in CMBB; i would assume some of this can be attributed to the common idea that they are still 'flawed'. Im qouting these guys simply to show that before we did these tests, we had very different ideas about the effects of curved armor and the effectiveness of the TD's, specifically Hetzer.

Id also like to summarize some of the points mentioned in this thread that really seem to stand out.

Glider really hit it on the head when he reminded me of the color bars in the unit screen. This clearly shows that each AFV's curved armor is modeled differntly. I about smacked myself :D

He also said this

IIRC, somebody mentioned that the actual algorythm used to describe the 'curved' armour is rather more complex than it appears and includes size of mantlet, shot traps and actual more/less vulnerable areas for each 'curved' armour section for each tank type separately.
Which i think makes a key point (even though its been said many times); The algorythmic models are far more complex than the limited values it shows to the player. This particular example makes me more confident about more "accurate" AFV engagements, and shows what a great job the Dev team has done.

Of course rexfords distribution chart really helps one get a better picture of how rounded mantlets work.

A big thanks to everyone; I think we have settled the issue of curved armor (for me at least), even if you grogs already knew ;) .

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