Bismarck and her contemporaries

Discussions about the history of the ship, technical details, etc.

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sineatimorar
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Re: Bismarck and her contemporaries

Post by sineatimorar » Sun Nov 03, 2013 3:30 pm

As facehard program is briefly mentioned. Although it is designed to simulate face hardened armour penetration, I find ,if you know what the backing material properties are you can come up with homogenous armour performance by removing the hardened % settings in the program. I got some results that close in equivalent performance doing so.

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Re: Bismarck and her contemporaries

Post by alecsandros » Sun Nov 03, 2013 6:36 pm

... Another program for perforation of homogenous armor was created by Nathan:

http://www.navweaps.com/index_nathan/index_nathan.htm

It is called "HCWCALC STS Armor Penetration Calculation Program "

I used it to calculate some solutions for designs with multiple armor plates, and then compared the output with GKDOS curves and various test trials.
As you can see, almost all battleships had multiple armor plates protecting the most likely trajectories towards the main magazines... thus after the initial impact (with cemented armor), the projectile needed to pass through 1,2 or even 3 layers of homogenous armor plates.

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Re: Bismarck and her contemporaries

Post by sineatimorar » Sun Nov 03, 2013 10:10 pm

The only problem I have with the program I have seen for homogeneous armour by Nathan Okun is it lack of armour choice and shell type, both of which seem to me to be restricted to one type each more along the lines of the international standard for testing steel strength, than any real world comparisons. The facehard program once you get your mind around what the modifiers actually do, seems a much more accurate reflection of the real world situations , as compared to theoretical world of laboratory conditions.

Understand I am not saying one is MORE accurate persa than the other, it just that I have to do less interuption of results, which makes it easier to relate to actual conditions.

The program provides enough ballistic information on both the ejected armour plug, and shell trajectories and condition to calculate multi-layer armour penetration, either as a dud or by timing of fuse delay to allow you to predict either the point of explosion or final resting point. If the intention of the programmer was only to deal with facehard armour, why place the modifier functions at the hands of the user?

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Re: Bismarck and her contemporaries

Post by alecsandros » Mon Nov 04, 2013 6:18 am

sineatimorar wrote:The only problem I have with the program I have seen for homogeneous armour by Nathan Okun is it lack of armour choice and shell type,
... The inputs allow for several informations about projectile and armor parameters, allthough maybe not as specific as one would prefer.
Variance between Nathan's homogenous calculator and firing trials is up to +/-12% for some tests. HOwever, it fits within +/- 3% for US armor attacked by US shells.

... And it represents tremendous synthesis work and the only one of this type that is free on the internet that I know about.

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Re: Bismarck and her contemporaries

Post by Thorsten Wahl » Mon Nov 04, 2013 9:36 am

Alecsandros you should use the armor thicknesses only (without platethicknesses of the holding structure)

Yes these plates have some ballistic value, but adding their thicknesses to the thickness of the armor plates appears more misleading as ignoring them completely.

the 68 degrees figure for Bismarck class(Declination from the vertical is only correct for machinery spaces
This angle is reduced, as the width of the TDS is reduced next to magazines.
Meine Herren, es kann ein siebenjähriger, es kann ein dreißigjähriger Krieg werden – und wehe dem, der zuerst die Lunte in das Pulverfaß schleudert!

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Re: Bismarck and her contemporaries

Post by alecsandros » Mon Nov 04, 2013 10:47 am

Thorsten Wahl wrote: the 68 degrees figure for Bismarck class(Declination from the vertical is only correct for machinery spaces
This angle is reduced, as the width of the TDS is reduced next to magazines.
Aaa, your're right Thorsten!

The angle of the slope next to the magazines varies, as the angle of declination the main belt plates next to magazines also varies.

From the plans that I have and measuring the angle myself, it appears the slope was inclined at ~ 58* next to magazine of turret Anton. Is this what you measured as well ?

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Re: Bismarck and her contemporaries

Post by sineatimorar » Mon Nov 04, 2013 4:49 pm

There is a very good explaination as to the accuracy of the American products. His program is directly linked to the methods used in USA when working out the orginal charts. The +- 12% error in other types is exactly as I expected due to the relative guess work about foreign armour in the 1940's and I believe in scientific standards this level of error voids the programme as a reliable tool other than when it comes to American products.

If you fiddle about with the armour modifiers in facehard and compare results with listed historical charts, the accuracy is more acceptable. I have got similar results to the historical charts when looking at the 38cm c 1934 sk weapon charts. ( In an exercise in proofing the programme for my own studies ).

The basic rule been the backing material of Kcna has similar metallurgical properties to Wh when you remove the facehard % setting. And with changes to the other settings a close approximation of Ww seems to be obtainable, but as I have limited historical figures pertaining to penetration charts for Ww type, I have limited ability one way or the other to confirm these modified settings.

Historical data from varied independent sources seems to confirm my initial basic rule principle.

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Re: Bismarck and her contemporaries

Post by alecsandros » Mon Nov 04, 2013 6:26 pm

sineatimorar wrote:The +- 12% error in other types is exactly as I expected due to the relative guess work about foreign armour in the 1940's a
All armor penetration formulas give errors when compared to specific trials.
They produce averages of expected performance.

It is the only available program on the internet that I know about, and it has tons of work behind it.

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Re: Bismarck and her contemporaries

Post by sineatimorar » Tue Nov 05, 2013 11:26 am

Do not get me wrong here, it is probably a perfectly viable program based on what is in reality a very hard science to accurately predict in theoretical terms for terminal ballistics. Empirical testing was and still is the only sure fire method proofing any weapon of this type. It just a personal preference on which program I prefer to use. As I said with the correct modifiers set, you can get just as accurate results. Including the reported behaviour of Wh armour and increasing oblique strike angles.
It like an old saying I like. It looks likes a duck, quacks like a duck, walks like one, so by definition it must be a duck.
In short it proven to work, so why not use it? Whether or not it was the original intent of the programmer to use it for this purpose or not.

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Re: Bismarck and her contemporaries

Post by alecsandros » Tue Nov 05, 2013 11:30 am

sineatimorar wrote:Empirical testing was and still is the only sure fire method proofing any weapon of this type.
Yes,
However empirical testing in itself has pretty large variances. The same type of sehll fired from the same gun against the same type of plate in the same circumstances requires more or less kinetic energy for penetration, because of small variances in projectile and/or plate quality factors, gunwear, powder temperature, ambiental temperature, humidity, pressure, etc.

It's not a perfect science

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Re: Bismarck and her contemporaries

Post by sineatimorar » Tue Nov 05, 2013 12:30 pm

Exactlly my point. I was actually quite shocked to how inaccurate this whole science is. I have made a complete fool of myself earlier on in other questions I asked and was finally set straight by Mr Bill Jurens. Needless to say he had some intertesting opinions on the whole question of computer simulations in regards to the science of ballistics, to which I will leave to him to make public if he wishes to do so.

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Re: Bismarck and her contemporaries

Post by alecsandros » Tue Nov 05, 2013 1:48 pm

sineatimorar wrote: Needless to say he had some intertesting opinions on the whole question of computer simulations in regards to the science of ballistics, to which I will leave to him to make public if he wishes to do so.
... I know he put alot of effort into an external ballistics simulator in the 90s

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Re: Bismarck and her contemporaries

Post by sineatimorar » Tue Nov 05, 2013 2:09 pm

Yes he did suggest a programme he published in a naval magazine to gain a better working knowledge of simulated ballistics, but I thought I would get a more in-depth look by attempting my own simulation. While doing so I found some of his earlier posts on this site where he gave a basic over view of which ballistic methods that could be applied with some accuracy to large calibre ballistics which short circuited my quest for accuracy as I had a free download of a programme based on the suggested format. There is still the struggle to simulate the complete flight profiles of high elevation long range shots but it is usable as a guide to minimum ballistic performance for what ever weapon you are looking at. It still frustrates the hell out of me , but it motivates me to keep on with question.

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Re: Bismarck and her contemporaries

Post by Thorsten Wahl » Tue Nov 05, 2013 3:52 pm

Regarding the final ballistics programmes made by Nathan Okun.

Ther is no question, he did a tremendous work in putting together data from ballistic tests and deriving a empirical programm wich fairly accurate predicts pentration.
But ther are several shortcomings as far as I can see.

He had created a virtual penetration curve for a ideal combination of elongation, UTS, deepness of face and some other factors
this curve neglected the variation of the underlying physical properties(and used for calculation) at different thicknesses of armor.

This problem became even worser, as ballistic quality between say american and german armor varies at different thicknesses
the US research tested several german plates from 8.5 to about 15 inches. The best german plates at the whole intervall were better then every US plate testet until this time and even much more better when comparing to average results of US plates. The thicker the plate the better (up to abpout 8 percent higher ballistic limit) the relative performance of the german plates.
Nevertheless N.O. created an constant quality factor for foreign(non american) armor.

According N.O,s calculation programs british and US RHA had the same ballistic capabilites, being better then german RHA in the order of 10 %. This calculated value is contradictory to the findings of british research, wich found that german RHA used for ships provided a somwhat higher limit then british RHA.

He derived the inferority from imputed lower elongation for german steels. As german elongation was measured by DIN standards and US elongation by US-Navy-standards the results differ considerably(in favour of the US measurements) as the dimensions of the specimens were different.

Some german plates wer found to perform worser,
the problem is, no pysical proprties data and informations about the composition of the steel were submitted by the american sources. Its therfor impossible to assign these results to regular armor plates or plates of a earlier date or even experimental plates or non armor steel plates. Additional later german steels suffers greatly from a lack of raw materials like molybdenum, chrome and nickel wich enhances the physical properties of steel alloys.
Meine Herren, es kann ein siebenjähriger, es kann ein dreißigjähriger Krieg werden – und wehe dem, der zuerst die Lunte in das Pulverfaß schleudert!

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Re: Bismarck and her contemporaries

Post by alecsandros » Tue Nov 05, 2013 5:10 pm

@Thorsten,
all the elements that you named make FACEHARD and NAAB orientative programs.

In the tabel that I have posted, both programs were used for calculations of secondary, tertiary and quaternary armor plates, with the main plate (primary plate) being calculated according to GKDOS-100 curves. As much as possible, I tried to compare the outputs for the II, III and IVth plates with test results that I have and estimates of other navies.

The result is the one that you can see - not perfect for sure, yet quite defendable, IMHO...

Initialy, I wanted to make a table with intervals. That is , for each type of perforation (heil at 0*, grenz at 30*, etc), to have a perforation interval that would depend on heel, pitch, variances in armor plate to plate quality, variances in shell to shell quality.
Of course this rapidly became unfeasible, as the variances are not known to me, and the ones that are tend to be so large that the intervals become meaningless. [for instance, British plates tested alongside Tirpitz 12.17" armor plate required with up to 8% more velocity for perforation, depending on their quality. Shell variations were in the range of +/- 5%, and heel and pitch could alter the final obliquity angle by so much that they could improve penetration (or not) with up to 20% at same range. Thus the interval for perforation of KGV's main belt at 30* could be between 8 - 18 km (in the table it is 13km)]

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