38 cm shells

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paul.mercer
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Re: 38 cm shells

Post by paul.mercer » Sat May 18, 2013 10:45 pm

Billy wrote:Found an amazing web site called Bismarck battle film analysis. An actual film of the battle that has been authenticated and would strongly recommend you guys look it up. It shows a number of things, namely Bismarck firing her forward turrets at intervals of 25 and 27.5 sec during the battle and that POW actually ceased fire at 6:07:30.
Hi Billy,
What was the website that you found?

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Re: 38 cm shells

Post by tommy303 » Sun May 19, 2013 1:40 am

I believe Billy is referring to an article entitled Bismarck Battle Film Analysis by Robert Winklareth:

http://www.german-navy.de/kriegsmarine/ ... ture7.html

The article is nearly seven years old and I believe, if I recall correctly, the subject was heatedly debated on this board back at least that long ago, particularly in connection with a book by Robert on the Bismarck Chase; it would appear that a newer book on the Denmark Strait action has been published recently by him, but I have not read it to see if it is an all new work or a rehashing of the Denmark Strait section of his original work.

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Re: 38 cm shells

Post by Guest » Sat Apr 18, 2015 10:38 pm

Hi Guys! I must apologize for my long absence. The Bismarck bug has bitten again and I'm off into the literature again doing my own studies in these amazing warships.

Anyway, my earlier post on the " battle film analysis " is exactly that. A film taken of the battle itself. It comes up first on the list if you do an internet search under that name. That captures on film that Bismarck did go into rapid fire sometime within the battle ( 25 sec, 27.5 sec for front salvoes so I would think that the tacticle use of rapid fire within a battle would be proved. Especially regards in comparison PE who got off a lot more BECAUSE she had a much higher rate of fire gun. As to the high proportion of hits for a heavy cruiser 3+ percent hits is exceptional for an 8 inch gun at the range in question. Refer the rate of other navies if you doubt that ie mostly sub 1 %.

The armour penetration values of 25 % greater for British and German armour I would think to be in my opinion indisputable if a careful contemplation of the balistics is analyzed. For brevity I used just the one example of the British and American 14 in weapon but I have found the same discrepancy in multiple other calibres. What should be agreed on is that American and British shells were similar ( Brit better at 0 - 30 deg, Am better at oblique impact which I'm sure you all know already anyway). Yet given this the calculated penetration figures using USN Empericle formula and British test always leads to a discrepancy of 25% less for Brit armour and this after the better penetration at normal impact for Brit shells. This also being proved by the balistic test of the 14 in shells stated earlier.

Lastly I think it may come to some surprise that the effect of the angle of inclination and fall of shot is not additive any way. Only being of importance where an angled belt is broadside on veritably increasing angle of incidence. I also thought at first it was A2+B2 = C2. But surprisingly you may find that for example a shell falling at 15 deg striking an angled belt at 15 deg strikes a ship at 30 degrees inclination the angle of incidence IS 30 deg! Same as a ship with no angled belt with a shell falling at 15 deg and an angle of inclination of the ship of thirty degrees. The striking angle is still only 30 degrees. This is because the angles are in 3 dimensional space and not on a 2d piece o paper. I know it sounds unusual but I was also surprised by the results.

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Re: 38 cm shells

Post by Guest » Sat Apr 18, 2015 10:55 pm

Ok, I think I owe you guys an opology! Whoops just rechecked my Maths and I am in error regarding the angle of incidence thing. It definatly is A2 + B2 = C2. The effects ARE additive as the root of the two squares if that makes sense.

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Re: 38 cm shells

Post by Thorsten Wahl » Mon Apr 20, 2015 12:28 pm

Ther is no 25% difference in ballistic limit of american FH armour compared to german and british FH armour (with german and british presumably being better but not by 25%).

What penetration values you are referring? You may offer some samples.
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Re: 38 cm shells

Post by Dave Saxton » Mon Apr 20, 2015 3:18 pm

Guest wrote: What should be agreed on is that American and British shells were similar ( Brit better at 0 - 30 deg, Am better at oblique impact which I'm sure you all know already anyway). Yet given this the calculated penetration figures using USN Empericle formula and British test always leads to a discrepancy of 25% less for Brit armour and this after the better penetration at normal impact for Brit shells.
British and American shells were not really very similar. One of the big differences was the head shape. American head shapes were almost hemispherical. British shells were had a caliber head radius of 1.4. This is why the British shells performed better close to or at the normal, and the American shells performed better at more acute striking angles. Tests vs decks showed that the American 14" shell still out penetrated (deck penetration) the longer and heavier British 14" shell, even though the American shell was much easier to de-cap. Also the British shells usually had larger explosive cavities and thinner walls.

Differences in armour penetration has more to do with the quality of the armour rather than the penetration properties of the shells. The poor quality of American FH armour is well documented.
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Re: 38 cm shells

Post by tommy303 » Mon Apr 20, 2015 7:24 pm

There was also a difference in hardening of the shell body. British shells were decrimentally hardened, while US (and the L/4,4 German shells were sheath hardened. Sheath hardening gave better results in oblique impacts, while decremental hardened shells gave their best results at low obliquity.

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Re: 38 cm shells

Post by Thorsten Wahl » Tue Apr 21, 2015 9:29 am

Oblique performance of american shells

The published data on oblique performance of american shells are based on calculated values based on Bu Ord scetch 78841 based on US empircal formula(Thompson F Formula). The obliqity term describe the real performance only approximative to say.

The formula tends to overestimate oblique performance of armor piercing shells in the obliquity area of 60degrees by about 10-25 percent.

There are also several factors that have considerable effect on oblique performance such as
lenght of projectile
hardness profile of projectile
head shape
cap
cap weight
attachment of cap
hardnessprofile of cap.

cap-armor piercing cap
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Re: 38 cm shells

Post by pgollin » Tue Apr 21, 2015 10:20 am

.

Quote ( Thorsten Wahl ) ;

"....... based on US empircal formula(Thompson F Formula) ......"

unquote


The UK took one look at the US's formula and dismissed it. They believed that IF it was accurate it was only accurate for a particular "family" of shell against a particular "family" of armour.

.

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Re: 38 cm shells

Post by Thorsten Wahl » Tue Apr 21, 2015 2:27 pm

The UK took one look at the US's formula and dismissed it
this statment can be found in SUPP 6/910 THE PENETRATION OF ARMOUR PLATE
the formula seems wrong even for all US shells as far as I know about.
Ther is also a US ballistic report, wich deals with the "exxageration".
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Re: 38 cm shells

Post by slaterat » Tue Jun 02, 2015 5:03 am

I wouldn't really say that the 38cm/52 is under rated or over rated, it probably depends more on who you are talking too. It is a big gun that fires a comparatively light shell and that may lead to the strong opinions about its merits. On the other hand I believe that the British 14/45 is much more often under rated. The knock on it is usually about its treaty limited 14 inch diameter, without considering overall aspects of the gun like range , penetration , accuracy and bursting charge, which are all pretty good.

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Re: 38 cm shells

Post by Billy » Mon May 01, 2017 11:47 pm

And also lets not forget accuracy. Also a not too mentioned topic. If you cant hit the target then what good is muzzle energy. From all accounts the 14 in was accurate. Although I do still really believe that the 38/52 is very underated. People say its got a light shell BUT it turns out that armour penetration is more a velocity dependant action. Recently read an analysis comparing a 2700 lb shell needing 94% of the velocity of a 2100 lb shell for the SAME penetration. Seems the Germans were wise to put the energy into a lighter faster moving shell after all. The one thing I do have a gripe about is penetration values are quoted side by side with no attention paid to comparative armour values and even worse quoted figures do not correspond to original documents. This is especially noticeable with the 38/52. Take a look at Navweaps site and it gives figures apparently from the German documents only the figures are completely different. One thing that did catch my eye though was that a British study in 46/47 concluded that a heavier (15%) cap is beneficial especially in oblique impacts. Thats about 12 -13 years after the Germans started to incorporate it. I think that poorer quality American armour penetration values corresponding to lesser penetration with American shells at normal impact has camoflaged the exceotional penetration abilities of German shells on very good Kn/ca armour as the nos will then seem to correspond.

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Re: 38 cm shells

Post by Billy » Tue May 02, 2017 12:27 am

Firstly - that it turns out that British and American shells were not that similar - you are actually right. However that greater performance at NORMAL impact of British shells only serves to camoflage the inferior American armour as it gives more penetration when penetrating superior British armour. Secondly that the American emperical formula gave unreliable results I can believe but IF that is implying that its the error in American armour quality Im not so sure. If that descrepancy of 10 - 25 percent happens at 60° then its not related to -25 % armour values as the -25 % was manifest at normal impact values >30.

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Re: 38 cm shells

Post by spicmart » Tue Oct 16, 2018 6:45 pm

@ Dave Saxton.

You once wrote that the lightweight shell of Bismarck's guns actually gave better horizontal armor penetration at longer ranges as it decelerates more quickly and thus has a steeper angle of fall than heavier shells e.g. the US superheavies which were more designed for deck penetration.
When one sees the higher possible barrel elevation of those guns and their highly steep angles how can it be that Bismarck's shells give an advantage?
I also heard that the the lighter shell would wobble more lose accuracy over range.

Can you elaborate on these things, please?

Thanks

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Re: 38 cm shells

Post by spicmart » Sat Nov 03, 2018 10:27 am

Or can anyone else answer my question (last post)?

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