Angled Plate Always Better Than Vertical Plate?

[Lady Roxanne]

I understand that some types of AT ammo are more effective against angled armor plate than others, and that the others tend to be more effective against fairly vertical plates. However, is it still correct to say that an angled plate is more resistant to penetration than the same plate in the vertical, regardless of the ammo used against it? IOW, does the increase in effective thickness due to sloped armor make up for the fact that some AT ammo (APBC?)does better against sloped armor than other types?

To put it another way, could a situation come about where a tank crew would actually prefer that their armor be at 0 degrees to the vertical due to the ammo type being used against them (if they knew the ammo type)?

Thanks!

[ July 12, 2003, 04:38 PM: Message edited by: CrankyKris ]

[Stavka_lite]

In a word, no. The whole idea of angling the armor is to decrease the amount of force applied to a specific spot. The AT gunner always wants to hit his target as close to perpendiculr as possible. This serves two purposes, 1. the maximum amount of energy is applied to as small of an area as possible, 2. there is less material for the shell to have to penetrate.

Chemical reaction shells that use shaped charges or HEAT are an attempt to overcome the angle and thickness of the armor. What these types of ammo are most successful at is reduceing the amount of enegry needed to get the round to the target.

[Lady Roxanne]

Thanks, Stavka.

On the two reasons you gave for using sloped armor, which is the more important of the two? Is it the added thickness that must be penetrated, or the increase in area the force of the round is applied to?

[Stavka_lite]

"Is it the added thickness that must be penetrated, or the increase in area the force of the round is applied to?"

By increasing the angle of the armor you increase its effeciency, thereby decreasing the amount of plating needed to do the job. I don't have the equations handy so these numbers are not accurate, just an illustration. Say, for intance you have 60mm of armor at 0 degrees, 60mm of plating angled at 45 degrees would give twice protection. You can substitute thickness by angling your armor. The inverse is also true you can decrease the thickness of the plating and still have the same protection. But back to your question...the thicker ( or more angled) the plating the more energy is required to penetrate. At the risk of contradicting myself and muddying the waters the thickness(and angling) is more important. You can have a very small round (37 or 20mm) fired at a very high velocity and it will not penetrate because it will lose its kinetic energy very quickly. If you shoot a large round( 75 or 88mm) round at the same velocity, it will have more kinetic enegry due to the increase in mass making penetration more likely.

Please forgive my verbosity and I hope this helps.

[Lady Roxanne]

I understand what you are saying, Stavka. We are communicating.

Here are the numbers. To double the amount of material a round must penetrate for any given plate, the plate must be angled 60 degrees to the vertical, not 45 degrees. For example, a 50mm vertical plate will require a round on a horizontal trajectory to penetrate 50mm of armor. The same plate tilted at 60 degrees to the vertical will require the horizontally travelling round to penetrate double that, or 100mm of armor. At 45 degrees the round must penetrate about 71mm of plate.

It took me over an hour to work out that basic high school trigonometry. The formula is:

Plate Thickness/Cosine of angle to the vertical = effective thickness of plate (amount of material the round must penetrate)

[ July 12, 2003, 09:36 PM: Message edited by: CrankyKris ]

[Redwolf]

The angled armor is not that much better as the numbers apply. While the plate can the thinner you usually need more plate to fit all the stuff you need inside the tank.

But to answer the original question: against WW2 AP shots the angle does more than just increasing thickness, it creates ricochets, and hence is more effective than the cosinus of the angle would imply.

Some WW2 rounds are less, others are more affected by angles. For example, rounds with tungsteen core but no disgarding sabot (i.e. they hit with their housing) have great difficulties getting grip on the target if there is an angle. But in no event will a round find less than the cosinus of the angle. So, no, you would never prefer not to have an angle.

Modern SABOT darts are formed to dig into the target and are practially not affected by angles in the ricochet sense, but of course the thickness improvement still applies.

[Stavka_lite]

As you can see Cranky, this can be a very in depth subject and alot of people have put alot ot time, money and effort to create good armor. The quality of the plate makes a great deal of difference as well.

Is the armor bolted on or welded?

Is the turrent cast?

As the war progressed the armor improved as well. When the Germans ran into the first T-34s they discovered that its sloped armor was hard to punch through and their little 37mm just couldn't do it.

Speed (manuveurability), Armor and Firepower are the three most important things that a tank has. By increasing Armor, Speed is decreased. Sloping the armor reduced the the thickness needed and the speed was kept. A good example of this is the Tiger, great gobs of heavy armor but slow as a turtle.

I'll shut up now and thanks for doing the math

[rexford]

The effective resistance of angled armor is not a function of the horizontal thickness that is presented. Using geometry and trig, a 60mm plate at 60 degrees from vertical presents a horizontal distance of 120mm to incoming rounds.

However, projectiles don't penetrate sloped armor on a straight line, they do all sorts of odd things.

If U.S. 76mm APCBC hits armor at 60 degrees from vertical, the round first starts to ricochet so the nose points upward, and then it tries to drive down a plug so the ammo would actually defeat the plate going downward if it was successful. No straight line here.

60mm at 60 degrees slope resists U.S. 76mm APCBC like 173mm of vertical plate, so Hetzers are safe from M10's on glacis hits. 76mm APCBC hits would ricochet off harmlessly, even against poor quality plate.

When flat nosed Russian APBC hits 60 degree armor, the flat nose digs in and resists the ricochet effect, and twists the round so it lines up closer to the armor perpendicular. When Russian 76.2mm hits 60mm at 60 degrees the armor resists like 163mm vertical, when 122mm APBC hits 60mm/60 degrees the vertical resistance is 98mm, so projectile diameter and weight play a part.

If 122mm APCBC (post WW II) and 122mm APBC hit 60mm at 60 degrees, the vertical resistances are 155mm (vs 122mm APCBC) and 98mm (vs flat nose APBC).

Tungsten core ammo is very hard and brittle, so angled armor is a real problem since it snaps the round and causes fracture. U.S. 76mm HVAP against 60mm at 60 degrees is resisted by a vertical plate equivalency of 267mm. U.S. 76mm HVAP bounces off the Hetzer glacis plate at point blank unless the armor is deficient.

[ July 13, 2003, 08:22 AM: Message edited by: rexford ]

[Lady Roxanne]

Now Rexford, did you have to go and complicate things?

What got me started on all this is that I kept finding myself trying to compare gun penetration stats in CMBB with the armor I was up against, and vise versa. Gun stats are only given at 0, 30, and 60 degrees. It seems the armor I'm trying to compare with these stats is often somewhere between a 30 and 60 degree slope.

There's a big difference in effective thickness between 30 and 60 degrees, especially with the thicker plates. At 30 degrees, effective thickness (assuming horizontal travel through plate) is increased about 15%. At 60 degrees of slope, the increase is 100%. So, there's a big difference between even a 45 degree slope and a plate at 55 degrees.

I made a chart that shows effective thickness of armor at various slopes. I'm hoping I can simply use the chart in conjunction with gun penetration stats at zero degrees to gain a better understanding of my actual chances. IOW, I will always have gun data to match my plate angle because I've converted the plate angles to 0 degrees. Granted, this will be very imprecise; but I'll bet it's twice as precise as what I have now when working with armor at slopes between 35 and 55 degrees.

[rexford]

Why estimate penetration at angles using straight line horizontal distance when some better figures are available?

Slope effect for APCBC ammo, such as most German rounds of 47mm and greater diameter, varies with the thickness of the plate divided by the projectile diameter.

Here are some sample figures to go by, which are based on analysis of firing test results:

75mm plate at 30 degrees

========================

95mm vertical vs 50mm APC (1.27 slope effect)

92mm vertical vs 75mm APCBC (1.23 slope effect)

91mm vertical vs 88mm APCBC (1.21 slope effect)

75mm plate at 45 degrees

========================

139mm vertical vs 50mm APC (1.85 slope effect)

131mm vertical vs 75mm APCBC (1.75 slope effect)

127mm vertical vs 88mm APCBC (1.69 slope effect)

60mm plate at 50 degrees

========================

128mm vertical vs 50mm APC (2.13 slope effect)

118mm vertical vs 75mm APCBC (1.97 slope effect)

114mm vertical vs 88mm APCBC (1.90 slope effect)

60mm plate at 55 degrees (Panther nose)

=======================================

157mm vertical vs 50mm APC (2.62 slope effect)

141mm vertical vs 75mm APCBC (2.35 slope effect)

136mm vertical vs 88mm APCBC (2.27 slope effect)

80mm plate at 55 degrees (Panther glacis)

=========================================

226mm vertical vs 50mm APC (2.83 slope effect)

203mm vertical vs 75mm APCBC (2.54 slope effect)

195mm vertical vs 88mm APCBC (2.44 slope effect)

60mm plate at 60 degrees (Hetzer glacis)

========================================

193mm vs 50mm APC (3.22 slope effect)

175mm vs 75mm APCBC (2.92 slope effect)

168mm vs 88mm APCBC (2.80 slope effect)

The above slope effects do not apply to uncapped pointed nose AP or Russian flat nose APBC which has a windscreen to reduce air resistance.

Slope effects used in above example do not apply to tungsten core ammo.

Note that when 17 pdr APCBC hits Panther glacis (76.2mm round), penetration is not going to occur unless the round hits a weld line or gets a lucky break (in the brittle armor that some Panthers carried).

[rexford]

The Americans used standard slope effects for all rounds as a function of angle, which went something like this:

10 degrees from vertical, 1.01 multiplier

15 degrees, 1.03

20 degrees, 1.07

25 degrees, 1.15

30 degrees, 1.25

35 degrees, 1.37

40 degrees, 1.52

45 degrees, 1.69

50 degrees, 1.89

55 degrees, 2.13

60 degrees, 2.50

For source, go to http://salts.britwar.co.uk/mod.php?mod=fileman&menu=8&PHPSESSID=467d5558481062a2dd0a4e84f50196d8

WW II weapon penetration tables.

then go down page to WO 185/118.

Suggest you use the above figures for a quick conversion of 0 degree penetration to angled performance, but only for APC and APCBC ammo.

[ July 13, 2003, 06:53 PM: Message edited by: rexford ]

[Lady Roxanne]

Thanks, Rexford!

I will modify my chart to use the American multipliers. The figures are not terribly different from my own; but different enough that it's worth reworking the chart. That will be close enough for my CMBB purposes. Generally one doesn't have much choice in a scenario anyway. It's just that there are instances where the gun to armor matchup is fairly close. In these cases, the in-game stats are insufficient IMO, especially if the armor in question is sloped somewhere between 35 and 55 degrees.

Thanks again!

[rexford]

Just remember that the slope effects I posted are for German capped ammunition (47mm and 50mm APC, 75mm, 88mm and upwards APCBC).

If you want I'll post some slope effects for uncapped AP and APBC, which is what the Russians used.

[Lady Roxanne]

Yes, please Rexford, give me some multipliers for the other ammo types. Speaking of ammo types, there seems to be many more than I realized. We have APC and APCBC for the Germans and APBC and AP for the Russians. What do the letters stand for? Let me try first.

AP - Armor Piercing

APBC - Armor Piercing Ballistic Capped

APC - Armor Piercing Capped

APCBC - Armor Piercing Cobalt Bomb Container

Is that correct? What does the last one stand for?

You do realize that if I lose too many armor fights I will be on this forum blaming my defeats on your multipliers, right?

[Bastables]

Pzgr 39 titled APCBC by the British = AP cap ballistic cap. Simply it's an APC round with an aerodynamic cap.

[ July 14, 2003, 12:04 AM: Message edited by: Bastables ]

[rexford]

Originally posted by Bastables:

Pzgr 39 titled APCBC by the British = AP cap ballistic cap. Simply it's an APC round with an aerodynamic cap.

Yup, you beat me to it.

German 50mm ammo consisted of AP and APC.

AP was a pointed nose projectile without any caps, the German 50mm AP had an explosive filler.

APC for 50mm gun had an armor piercing cap that also served as a ballistic windscreen, since it improved the air resistance of uncapped AP. But the APC air resistance was not as low as APCBC, so 50mm APC loses velocity at a good clip.

APCBC is an armor piercing round with an armor piercing cap, and both are under a ballistic cap windscreen that improves the aerodynamics.

German 75mm L24 round had one cap that functioned as both an armor piercing cap and a ballistic cap. Normally armor piercing caps have a square looking nose, but on the 75mm L24 round the armor piercing cap was sleek and aerodynamically well shaped.

Armor piercing caps are designed to decrease the probability of nose shatter against hard armor and face-hardened plates, and to reduce shatter possibilities. There is a good chance that early German ammo, such as 37mm and 50mm AP, was softer and uncapped and may have shattered on Russian and British thick armor.

The armor piercing cap fits over the nose and shoulder of the projectile, often with an air space between the cap and the projectile nose. When the round hits armor the initial impact is spread over the projectile shoulder and very little makes it to the nose, so shatter and nose damage chances are minimized.

British 2 pdr AP shattered alot against German face-hardened armor in Africa.

Armor piercing caps improve penetration against face-hardened armor, since that type of armor defeats hits by damaging the nose and body of the round. If the nose and body of the ammo is slightly damaged or untouched, the face-hardened armor is in trouble.

U.S. 75mm APCBC penetrates about 105mm of face-hardened armor at 0m and vertical, Sherman 75mm AP penetrates about 95mm.

But armor piercing caps absorb energy against homogeneous armor and decrease the penetration: 75mm APCBC from Sherman penetrates 91mm homogeneous armor at vertical and 0m, 75mm AP penetrates 114mm.

Homogeneous armor is the same hardness all the way through (more or less), face-hardened has a thin layer that is very hard.

[Tero]

Originally posted by redwolf:

While the plate can the thinner you usually need more plate to fit all the stuff you need inside the tank.

Ie. the vehicle is either extremely cramped or has a high silhouette. Or both.

It also makes the design harder to uparmour than a design made out of vertical plate "boxes". The quantity needed for the beef up armour is greater and so is the weight.

[zukkov]

while all this is very interesting, wouldn't it be easier to put a target line on the armor to see what your chances are?(ie: good, fair, rare, none, etc.). after all this is a game. lol..

[Michael Emrys]

Originally posted by rexford:

Is it not also the case that caps reduce the likelihood of a riccochet on angled armor?

Michael

[Lady Roxanne]

Zukkov,

Those are your chances of penetrating, but not your chances of being penetrated. Also, movement status of the vehicle is taken into account I think. I'm not interested in hit percentage or a general assessment of my penetration chances at one instance in time. I want to know how my equipment compares to the enemy's in a head-on shootout at various ranges. This is not a game after all, it's war!

[rexford]

Originally posted by Michael emrys:

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

Is it not also the case that caps reduce the likelihood of a riccochet on angled armor?

Michael </font>

I've read where armor piercing caps are supposed to reduce ricochet chances.

Analysis of slope effects shows that pointy nose AP has lower slope effects than APCBC, which suggests that the APCaps aren't doing much biting into the armor.

The armor piercing cap against sloped armor may fall into the same caregory as the curved cast hull front on M4A1 that is supposed to present superior armor resistance, two theories that may not hold water.

[ July 14, 2003, 04:38 PM: Message edited by: rexford ]

[Lady Roxanne]

Rexford!!

Where's my AP and APBC multipliers for converting to vertical plate?!

[Michael Emrys]

Hold your horses! Sexy Rexy may work slow, but he works deep. Let him do it his way and you shall be amply rewarded.

Michael

[Lady Roxanne]

Rexford says, "If 122mm APCBC (post WW II) and 122mm APBC hit 60mm at 60 degrees, the vertical resistances are 155mm (vs 122mm APCBC) and 98mm (vs flat nose APBC)."

The flat nose APBC is apparently some good stuff with its windscreen. I would have thought the Germans would have the better ammo types for defeating sloped armor.

[Lady Roxanne]

A highly motivated person could calculate the multipliers (and divisors) for every gun/ammo type at 30 and 60 degrees using CMBBs own gun data tables. I assume these tables use the actual figures the game uses.

Once the 30 and 60 degree multipliers for every ammo/gun type are determined, the multipliers for the angles inbetween could be estimated. The estimates could be based on careful consideration of the American table Rexford listed. IOW, the figures between 30 and 60 degrees could be chosen by maintaining the proportional relationship of one angle's multiplier to another.

For example, the American multiplier for 40 degrees is 1.52. For 45 degrees it is 1.69. This give an 11% increase in the multiplier from 40 to 45 degrees. These multipliers would have to be juggled a bit to fit nicely between CMBBs 30 and 60 degree figures, but they would be fairly close because the 30 and 60 degree figures are "perfect" as they relate to CMBB.

This would give individual multiplier sets for EVERY specific ammo/gun combination. Every gun would have its own chart, just like in the game, but no angle gaps. Hehe.....talk about overkill; but it's interesting.

Once the hard work is finished, a PBEM armor battle could be started with confidence. Then on turn 10, when I get the inevitable highly unlikely bad break, I can curse myself for wasting so much time on penetration charts.

EDIT: Heck, if you have a "perfect" multiplier for every gun/ammo type at 30 and 60 degrees you could just space out the rest of the figures, increasing the gap a little as the angle increased. It would be close because you're starting with specific multipliers for a single gun/ammo type at the extremes (30 and 60).

[ July 16, 2003, 05:45 PM: Message edited by: CrankyKris ]