The solution is simple. Assign the shell type to AP but with a penetration modifier that sits between SAP and AP. It might not perform as good as 100% typical AP but it’s sure much better than SAP.
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I forwarded your message to the developers, but they do not accept Jordan’s reproduction of the shell cross-section as binding. You would need a blueprint of the OPF shell to allow for an argument to be made here.
Similar to this:
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I appreciate your efforts for sending that information to the developers and I understand why they would doubt the accuracy of such a sketch. Therefore, I will prove that such an analysis of a sketch is reasonably accurate through the method of approximation on the German sketch.
So let’s begin with the German sketch of the shell.
Given that this sketch was used in the developer’s analysis, it is reasonable to say this would be a credible source. We have the shape of the AP cap on the outside but we do not have an internal profile that shows how thick it is inside.
However, we can use approximation method on the German sketch to prove that the weight of the AP cap is within the reasonable range of AP shells.
For illustrative purposes, I used Jordan’s sketch to display my method of approximation. All approximations are done on the German sketch.
In this method, we make two assumptions on the shape of the shell under the cap before modelling it.
Assumption #1 (see green dotted lines): The shape of the shell continues at the same slope measured between the base of the shell cap and the shell until it meets the halfway height of the shell cap. This assumption is justified as the side profile of shells curve inwards towards the tip rather than continuing at a constant slope and the worst case would be a constant slope that decreases volume taken up by the AP cap. We expect a reduction in volume of the AP cap using this assumption.
Assumption #2 (see blue dotted lines): From the halfway point, the shape of the shell extends directly to the very tip of the hardened cap at a constant slope. This assumption is justified as the AP cap is meant to improve the armor piercing capability of the shell by adding an extra layer of metal. We take the worst case possible and assume the thickness of the cap measured between the tip of the AP cap and the tip of the shell is near zero. We expect a further reduction in volume of the AP cap using this assumption.
With these assumptions in mind, I modelled the shell cap according to the German sketch.
From this model, we get an estimated volume of 6106.67 cm³. As expected, the two assumptions clearly stated at the beginning of the analysis reduced the volume of the cap which was previously 6657.81 cm³.
Now we can calculate how close the approximation of the German sketch was to the direct calculation of Jordan’s sketch.
6657.81 - 6106.67 = 551.14
551.14 / 6657.81 = 8.28%
Now we calculate the percentage weight of the AP cap using the worst case estimate of the volume.
Let’s assume the density of regular steel is 7.85g/cm³.
We multiply volume of the shell cap by density to get the mass.
6106.67 * 7.85 = 47,937 g or 47.94 kg
We divide the mass of the AP cap by the mass of the shell to get the percentage weight of the shell cap relative to the shell.
47.94 / 570 = 8.41%
Therefore if the worst case given by assumption #1 and assumption #2 using improbable shell characteristics is valid, the absolute minimum weight percentage of the shell cap is 8.41%. Given that the volume approximation of the German sketch using worst cases only deviates 8.28% from the volume measurement using Jordan’s sketch, we can conclude that Jordan’s sketch is not at all likely to portray the size of the AP cap larger than it should be and that such an estimation is accurate.
Mathematical Proof
Spoiler
Now some of you might doubt that the mesh volume measurement tool is accurate, or even worse, suspect that I manipulated the model to get a larger measured volume while making it look normal from a fixed point of view. Such concerns are reasonable as I would have similar thoughts. I can assure you that for a simple mesh like a shell cap, the mesh volume measurement tool is very accurate for this application. However, I would like to further solidify my analysis through manual calculations to prove that the estimations given by the tool fall within a reasonable range of accuracy as well as to show that there is no foul play involved in the model.
To show that the volume estimate of the worst case model is accurately measured to a reasonable degree, I made a simplified model of the shell cap using 7 basic shapes that would give an approximate volume measurement. We can calculate the volume of each shape using already known formulae and measurements extrapolated from the German sketch.
Shapes 1-5 represents the outer profile of the shell cap while shapes 6-7 represents the inner profile. By adding up the volumes of shapes 1-5 and subtracting the volumes of shapes 6-7 from it, we can expect to get a volume approximation that is very close to the mesh volume measurement of the original model.
We will be working from bottom to top with three formulae:
-
V = 1/3 × πh (r1² + (r1 × r2) + r2²)
Volume of partial cone where V= volume, h = height, and r1, r2 = radii -
V = π × r² × h
Volume of cylinder where V = volume, r = radius, and h = height -
V = (1/3) × π × r² × h
Volume of cone where V = volume, r = radius, and h = height
Shape 1
r1 = 30.44/2 = 15.22 cm
r2 = 32.42/2 = 16.21 cm
h = 2.80 cm
This is a partial cone so we use V = 1/3 × πh (r1² + (r1 × r2) + r2²)
V = 1/3 × π (2.80) (15.22² + (15.22 × 16.21) + 16.21²)
V = 2173.10 cm³
Shape 2
r1 = 32.42/2 = 16.21 cm
r2 = 29.91/2 = 14.96 cm
h = 11.53 cm
This is a partial cone so we use V = 1/3 × πh (r1² + (r1 × r2) + r2²)
V = 1/3 × π (11.53) (16.21² + (16.21 × 14.96) + 14.96²)
V = 8802.90 cm³
Shape 3
r = 26.06/2 = 13.03 cm
h = 2.67 cm
This is a cylinder so we use V = π × r² × h
V = π × 13.03² × 2.67
V = 1424.13 cm³
Shape 4
r1 = 26.06/2 = 13.03 cm
r2 = 12.45/2 = 6.23 cm
h = 15.05 cm
This is a partial cone so we use V = 1/3 × πh (r1² + (r1 × r2) + r2²)
V = 1/3 × π (15.05) (13.03² + (13.03 × 6.23) + 6.23²)
V = 4566.88 cm³
Shape 5
r = 12.45/2 = 6.23 cm
h = 4.12 cm
This is a cone so we use V = (1/3) × π × r² × h
V = (1/3) × π × 6.23² × 4.12
V = 167.46 cm³
Now we do the inside volumes.
Shape 6
r1 = 30.44/2 = 15.22 cm
r2 = 20.54/2 = 10.27 cm
h = 17.78 cm
This is a partial cone so we use V = 1/3 × πh (r1² + (r1 × r2) + r2²)
V = 1/3 × π (17.78) (15.22² + (15.22 × 10.27) + 10.27²)
V = 9187.27 cm³
Shape 7
r = 20.54/2 = 10.27 cm
h = 18.39 cm
This is a cone so we use V = (1/3) × π × r² × h
V = (1/3) × π × 10.27² × 18.39
V = 2031.19 cm³
We add up all the volumes of shapes 1-5 to get the solid volume.
2173.10 + 8802.90 + 1424.13 + 4566.88 + 167.46 = 17134.47 cm³
We add up all the volumes of shapes 6-7 to get the volume of the shell inside the cap.
9187.27 + 2031.19 = 11218.46 cm³
We subtract the volume of the shell in the cap from the solid volume in order to get the approximate volume of the shell cap.
17134.47 - 11218.46 = 5916.01 cm³
Now let’s see how close the mathematically calculated volume of the simplified model is to the volume of the original model measured by the mesh volume tool.
6106.67 - 5916.01 = 190.66 cm³
190.66 / 6106.67 = 3.12%
Using a simplified model to manually calculate the volume of the shell cap only deviates 3.12% from the volume of the original model measured directly by the mesh volume tool. The slight reduction in volume is to be expected, as using only cones and cylinders does not cover the entire volume of the shell cap, especially at the bottom.
Therefore if the manual calculation of the simplified model is correct and only deviates 3.12% from the volume of the original model measured by the mesh volume tool, we can conclude that the mesh volume tool is accurate to an acceptable degree in this analysis and there is no foul play involved with making the model.
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That’s a piece of work there good job 👍 … how much time did you spent making all of that ? Hopefully it will not be ignored by the devs .
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Maybe roughly 2 hours? I’m used to doing analysis of sketches like these as I formerly modelled in 3D from various blueprints and schematics for game development.
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Incredible work !
I hope it will be taken into account :).
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Sadly it’s the second option, I cannot do more than you when it comes to technical/suggestion stuff :).
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ha that sad … thanks for you consideration anyway : )
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HK Reporter liked Admiral_Bofors post, so I’m sure he’ll forward it to the Devs.
Fingers crossed 🤞 🤞
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Great job. It takes some skill to do something like that.
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yes, bacause it’'s french
Great work in any case, to all those involved. And thanks a lot for going the extra-mile for the sake of all our enjoyment.
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24 h no response and the dev serv closed … idk if i like that :/ .
Maybe they haven’t got a response from the devs.
And apparently the update is coming out next week, so there’s time.
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agreed
update will most likely drop early next week so we still have this week’s last few days to get an answer
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really next week ? it cant be possible to drop tomorow or after tomorow ?
gszabi99 said that the update gonna drop next week. He has some inside info, because he always leak stuff.
For Thursday update we would have the news announcement already. And they don’t do updates on Fridays, the Weekends or Mondays.
So upcoming Tuesday is my guess.
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Post updated to include mathematical proof for those who might be skeptical of the mesh volume measurement tool used in the analysis.
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