Artillery versus Spall Liner Worksheet – World of Tanks

Why are we going to go over this Artillery versus Spall Liner Worksheet you ask? Well, I saw someone complaining that Artillery was again, over powered. This brought on the guy mentioning that his Spall Liner should have deflected or otherwise mitigated the damage. This is why we need to go over it again... and for those of you who think that Artillery is in fact over powered, I dare you to level any Arty/SPG to level 4 - then tell me they are OP - cause they aren't...

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Artillery versus Spall Liner Worksheet

Spall liner "isn't very good" because of how HE splash damage is calculated:

0.5 * nominalDamage * (1 - ImpactDistance/SplashRadius) - 1.1 * nominalArmorThickness * SpallCoefficient

Artillery versus Spall Liner WorksheetThis formula is then evaluated for maximum damage for every non penetrating HE shot, or to put it more bluntly, the game automatically picks the best outcome for the artillery player, by picking the optimal combination of ImpactDistance and nominalArmorThickness at the point of impact. There are two effects in play that severly limit the effectiveness of the spall liner:

  • The Spall Liner reduces the damage reduction contribution of the NOMINAL armor thickness of the armor part in question by 50% (for the "Super Heavy..." variant), which is very often not that much to begin with. Even with 200 nominal armor thickness (which is a lot, most tanks rely more on angles than on actual armor thickness) that is only 100 additional damage reduction, and keep in mind this is an UPPER BOUND for the effectiveness of the spall liner.
  • Because the game automatically optimizes the above formula for damage, adding a multiplier might just shift the "point of impact" around and reduce the effectiveness of the spall liner even further. See the math at the end of this points for some numbers, but in the most extreme cases this means that the spall liner does nothing.

I think overall the Spall Liner COULD be a way to give HTs some much needed help against SPGs, but not the way it is currently working out. Just a flat out reduction in damage from HE shells (either as a multiplicative or even as a fixed subtractor) could work wonders. But as it stands, Spall Liner really isn't a thing unfortunately.


Lets do some math. Assume a 1000 damage shell is hitting a target that only consists of two points, one with 240 armor right at the point of impact and another point half the splash radius away with 25 armor (think turret front and turret roof). Without spall liner, the shot would deal 236 damage and be calculated at the turret front:

0.5 * 1000 * (1 - 0/1) - 1.1 * 240 * 1    = 500 - 264   = 236 
0.5 * 1000 * (1 - 0.5) - 1.1 * 25 * 1    = 250 -  27.5 = 222.5

Lets put in spall liner because it HALVES THE DAMAGE OF ALL NON PENETRATING HE SHELLS? HOW GOOD IS THAT, WHY AM I NOT RUNNING THAT IN ALL MY TANKS?! WOW!! (me, circa 2 years ago when I first discovered the item):

500 - 1.1 * 200 * 1.5 = 500 - 330 = 104
250 - 1.1 * 25 * 1.5 = 250 - 41.25 = 208.75

World of Tanks Expert PackNow the turret roof is calculated, and instead of cutting the damage in half, or even reducing it by another 100 or whatever, putting in a spall liner lead to a damage reduction of just ~10%. Barely noticeable in a semi chaotic game where the damage range for each shell is +- 25%.

Disclaimer: Yes, the numbers are to illustrate my point, I fully realize that a tank doesn't only have "2 points" and that the 240/25 armor is a rather big difference. I was giving an example and making a point and I didn't want to get into finding local extrama for multivariable functions to do that.


So hopefully this Artillery versus Spall Liner Worksheet has helped you to understand why a High Explosives shot hitting into a Spall Liner isn't really going to do much for you, in terms of Damage Mitigation.

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