38 cm shells

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alecsandros
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Re: 38 cm shells

Post by alecsandros » Thu May 09, 2013 5:19 am

tommy303 wrote:... As to the rates of fire, one might say both German ships were shooting in a deliberate manner.
If I understand correctly, all ships involved fired their initial salvos for ranging purposes.

Bismarck did not have the necessity or opportunity to attempt firing at maximum rate of fire, as Hood was destroyed during the ranging phase, and Prince of Wales shifted course several times, making her a more difficult target. [Bismarck's abrupt course change following the fake torpedo alarm also affected firing...]

Perhaps only salvos 5 and 6 from Bismarck were fired without waiting for range confirmation [continous fire], as salvo 5 destroyed Hood and salvo 6 was already in the air at the time of the detonation of the magazines [suggesting a firing cycle of less than 24sec, time of flight of the 38cm shells fired at 16km distance]

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Re: 38 cm shells

Post by Billy » Thu May 09, 2013 9:35 am

Thank you Paul for your well researched info. Just wanted to add or point out the potential value of rapid fire capability within an actual battle. The question I would like to ask is was Bismarck firing full 8 gun salvos or was was she ranging with only 4 at a time? The other thing was that once the range was found as in the case of Hood, she had a rapid burst from the 4th and 5th salvos, evidenced by the fact that Hood was encompassed by shell splashes as she was blowing up,after the hits of the 4th salvo. I don't think that the Bismarck would intentionally fire at an already vanquished or blowing up foe, and given the time of flight at that range that would seem to rule out that possibility. However if you do compare the amount of rounds gotten off potential or actual between P.E. and Bismarck, this
would definetly support the value of a higher rate of fire weapon in battle and would go some way to explain the high proportion of hits from the little 8 in gun cruiser.

As to the comparison between German and British 15 inch guns being the same, the data does not support that assertion. The data in fact shows quite a big advantage in favor of the German gun and as the data is based on actual test results, I will not doubt it.

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Re: 38 cm shells

Post by paulcadogan » Thu May 09, 2013 12:27 pm

Billy wrote:Thank you Paul for your well researched info. Just wanted to add or point out the potential value of rapid fire capability within an actual battle. The question I would like to ask is was Bismarck firing full 8 gun salvos or was was she ranging with only 4 at a time? The other thing was that once the range was found as in the case of Hood, she had a rapid burst from the 4th and 5th salvos, evidenced by the fact that Hood was encompassed by shell splashes as she was blowing up,after the hits of the 4th salvo. I don't think that the Bismarck would intentionally fire at an already vanquished or blowing up foe, and given the time of flight at that range that would seem to rule out that possibility. However if you do compare the amount of rounds gotten off potential or actual between P.E. and Bismarck, this
would definetly support the value of a higher rate of fire weapon in battle and would go some way to explain the high proportion of hits from the little 8 in gun cruiser.
Bismarck fired 8 guns per salvo but, based on footage and eyewitnesses, each was split into 2 half salvoes from the forward and aft groups separated by 2 or 3 seconds.

It was the 5th salvo that destroyed Hood, not the 4th which was short. I'm not sure where you got the info that Hood was surrounded by splashes as she blew up because none of the eyewitness testimony I've read suggests that. Some (e.g. Captain Leach) saw a straddle with the up-rush of flame occurring in a couple seconds, while others never noticed splashes at all. (see: http://www.hmshood.org.uk/reference/off ... _intro.htm ) The 6th salvo would have landed somewhere ahead of Hood's position since the ship rapidly lost forward speed.

As for the Prinz, she did not score a "high proportion of hits" - in fact quite the opposite, comparatively! She scored one known hit on Hood (possibly two, IF she scored the hit at the base of the bridge as that could have been Bismarck), and 3 hits on PoW totaling 5 out of 157 shells fired - a hit rate of 3.2% at the most, compared to Bismarck's 6 (2 on Hood - could have been 3 - , 4 on PoW) from 93 or at the least 6.5%! PoW's hit rate too - 3/55 or about 5.5% was better!
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Dave Saxton
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Re: 38 cm shells

Post by Dave Saxton » Thu May 09, 2013 2:25 pm

Billy wrote:The Japanese did copy from British sources, but as I understand it that was circa ww1. I would find it highly unlikly that they would reveal or give top secret information away that would drastically improve their armor.
According to the Technical Mission to Japan the MNC homogenous material was essentially the same as contemporary British homogenous NCA material.

I don't recall if VH was the same quality as contemporary British CA. I doubt if it would be very sub-standard.

Nonetheless, it could depend a great deal on thickness of the plates in question. The thicker the plate the lower the quality. As a rule of thumb, face hardened plate should not be thicker than about 13" to maintain the highest quality, and homogenous plates should not exceed about 6" or 7" and preferably be less than 5".

Smelting infrastucture and technology can also affect the overall quality, and the ability to proper face harden, normalize, and temper. The impurity content among both face hardened and homogenous plates is also greatly affected by smelting method. In the BIOS documents the British mission found that electric arc furnace smelting resulted in much higher quality armour grade steels in Germany.
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Re: 38 cm shells

Post by Billy » Sat May 11, 2013 9:49 am

Hi Paul, I got the info from Axis and neutral battleships of WW2, which gives quite a facinating and well researched account of the battle. It refers to Hood being struck by the 4th salvo, but I know other sources quote the 5th salvo.

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Re: 38 cm shells

Post by Thorsten Wahl » Sat May 11, 2013 5:09 pm

Billy wrote: The British gun could pierce 14 inches of armor at 13700 yards, the american weapon could pierce 17.63 inches of American armor at the same range. Now if you divide 14 by 17.63 you get a ratio of 1.259, or 25.9 percent more resistance. Which is almost exactly the value given by authors such as D.K. Brown. It is therefore proved that British and German armor was superior by the stated amount of 25%.
A comparision on that basis is failing as the impactenergies of these projectiles were different and also angle of incidence. The american projectile has approximately 15 per cent mor energy, therfore it should be able to penetrate thicker armor. Additional the penetration figures for the british projectile were made considering an average gun(i.e. reduced muzzle velocity).

did D.K. Brown wrote, where he get this information, as this statement is apparantly in stark contrast to practical british ballistic research as I mentioned few posts above.
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Re: 38 cm shells

Post by Billy » Sat May 11, 2013 9:59 pm

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.

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Re: 38 cm shells

Post by Billy » Sat May 11, 2013 10:14 pm

To Thorsten Wahl. The test in question was conducted at the U.S. Proving grounds. As I don't think they actually shipped an entire British gun over they would have performed the test in an American gun with more than likely identical charges, since it is the same chamber, probably even using the same gun. Their energies would therefore be very close together. Their findings were that " at 30' obliquity, both the U.S. and British projectiles were virtually identical in penetration ability". Hope this is helpful but need more details as to how the test was conducted.

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Re: 38 cm shells

Post by Billy » Sat May 11, 2013 11:56 pm

Sorry forgot to add, at the range in question ie 13700 yards, the relative velocities of the projectiles in question are, 541.8 mps (1774 fps) for the British 723.5 kg (1595 pound) projectile and 565 mps (1853 fps) for the American 680.6kg (1500 pound) projectile. Now if you use the equation 1/2mv2 (half mv squared), you get the energies of 106,2 MJ for the British shell and 108,6 MJ for the American shell. As you can see they are very evenly matched at this velocity with only a 2.2 percent advantage in energy at the range at which I specified , in favor of the American weapon. However with my calculations I got a 25.9 percent advantage of British armor at that range. Even if you subtracted 2.2 percent from 25.9 you still get 23.7 percent advantage over American armor and still very close to the stated value of 25%. I would therefore regard this is still valid and proof of the 25% advantage.

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Re: 38 cm shells

Post by Thorsten Wahl » Sun May 12, 2013 10:46 am

Billy wrote:To Thorsten Wahl. The test in question was conducted at the U.S. Proving grounds. As I don't think they actually shipped an entire British gun over they would have performed the test in an American gun with more than likely identical charges, since it is the same chamber, probably even using the same gun. Their energies would therefore be very close together. Their findings were that " at 30' obliquity, both the U.S. and British projectiles were virtually identical in penetration ability". Hope this is helpful but need more details as to how the test was conducted.
here you are
https://docs.google.com/file/d/0B12aaMD ... sp=sharing

conclusion from this test
Summary comparative performance of american and britiosh 14 inch APC shell against american armour.jpg
Summary comparative performance of american and britiosh 14 inch APC shell against american armour.jpg (129.69 KiB) Viewed 4350 times

As you can see they are very evenly matched at this velocity with only a 2.2 percent advantage in energy at the range at which I specified

but the pentration data you took was from the original british penetration tables wich use average wear figures(i.e reduced muzzle velocity). If you include the higher velocity the british projectil would perforate thicker armor too.
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Re: 38 cm shells

Post by Billy » Sun May 12, 2013 2:56 pm

Thanks Thorsten for the info, much appreciated. Although also I never added in any of the advantage at normal incidence and penetration tables are calculated for normal incidence at the range specified. This would make up for any small discrepancies and push it up around or over the 25% value. From what I understand though is that American battleships used sloped armor which would have seriously enhanced their armor capabilities. For example the South Dakota clas had an armor belt angled at 19 deg. She also had a 1.5 skin plating in front of that, that would have decapped all other navy shells with the exception of theGerman weapon which used type 2 hard caps and needed at least 2.54 in for decapping. I am aware that the framing would have added too the thickness in places on the plating itself, but I think edge effects would have largely nullified this (exposed edges likely to tear including that of the frame itself), but still not a good idea to rely on a possible hit on framing as well. My own calculations would suggest a relative thickness of a 12.25 in belt against all other except German of about 19.5 in. Even if you subtract for the 25% you would still get a value of 15.6 in (very good indeed!). If you calculate for German shell you still get values of 17.2 in adjusted for 25% still gives a value of 13.79.( still not bad indeed at all and the equal to all other navies if not better.)

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Re: 38 cm shells

Post by Thorsten Wahl » Mon May 13, 2013 5:50 am

Billy wrote:Thanks Thorsten for the info, much appreciated. Although also I never added in any of the advantage at normal incidence and penetration tables are calculated for normal incidence at the range specified.
All german, american, british and italian penetration tables I have seen consider angle of fall of the projectile. Usually they consists changed penetration values too, for different target angles, but the resulting compound impact angle is not AOF + target angle.

the seemingly do not consideration of AOF appears as misinterpration of the meaning of the constant (target)-angle to me.
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Re: 38 cm shells

Post by Dave Saxton » Tue May 14, 2013 3:37 pm

Billy wrote: For example the South Dakota clas had an armor belt angled at 19 deg. She also had a 1.5 skin plating in front of that, that would have decapped all other navy shells with the exception of theGerman weapon which used type 2 hard caps and needed at least 2.54 in for decapping. .

That the outer shell constituted and effective de-capping array is post hoc ergo propter hoc. Nor could it have been effective in practice although unintended as such. The Italians determined that their de-capping array needed a de-capping plate of 70mm (about twice as thick) sloped 11*. This is closer to the German finding that a de-capping plate be at least 20% the diameter of the shell; if striking at any obliquity such as would be encountered by striking vertical armour (decks will require less thickness due to the acutely oblique striking angles). The SD/Iowa outer shell may have been able to de-cap American shells (the easiest to de-cap) at acutely oblique striking angles, but likely not others.
Entering a night sea battle is an awesome business.The enveloping darkness, hiding the enemy's.. seems a living thing, malignant and oppressive.Swishing water at the bow and stern mark an inexorable advance toward an unknown destiny.

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Re: 38 cm shells

Post by Billy » Wed May 15, 2013 5:08 pm

To Thoresten thanks, but what I meant was that given the British shells known advantage at normal incidence and the angle of fall at that range would still be very close to normal (around 10deg ) so the advantage would still apply as the penetration values only equaled out at around 30 deg.

To Dave, you are absolutely correct. The Italians did use thick decaping plates and this is very suggestive that they too used a type 2 type cap. As too the actual thickness needed to decap I would really like to see where you got the info that says 20% caliber was needed. If you could forward it on would be much appreciated.

The next thing I would like to discuss is the figures I quoted for the South Dakota's belt resistance. Although it may represent an advantage at a bearing of 0 deg. I was interested to find out how it would fare at different angles of inclination and got some very interesting results. So lets say for instance you have a belt inclined at 20 deg with a firing bearing of 20 deg. It is tempting at first to just add the angles together and get 40 deg. This of course would be wrong. What I thought to be the case would be the use of Pythagorus's theorum A2 + B2 = C2, which would lead to steadying decreases in advantage with added bearing. However in checking this theory I saw that it was actually wrong. If you have a belt angle of 20 deg and then a firing angle of 20 deg of bearing,the actual angle of incidence is 20 deg! So although angled armor is of value at 0 deg bearing, it has a very steep drop off in advantage to that of a 90 deg belt, where the advantage dissappears at 20 deg of bearing. At a 45 deg bearing and 20 deg belt iccidence the striking angle of the shell is 45 deg. The 20 deg only changing the throw off angle. Although this seems hard to believe you can check it yourself by holding a book in front of you, tip it forward to simulate an angled belt then turn one sides back and the other side forward by whatever degreeput a pencil in the middle of it as if you hadnt moved the book, get a potractor and measure the smallest angle. You will find that its always the larger degree that takes precident.

However that being said, if a person can decap a shell you get a 20% advantage at just about all angles of bearing and the added bonus that it would be lighter by the amount of the weight of the cap. (average around 10% although there does seem to be a large variance). One has to also take into consideration though the potential disadvantages to a decapping plate. It would really have to be thick enough so that it still provided a protected waterplane area. Otherwise there would be losses in speed and stability to even light shells and serious risk to explosive shells tearing them up, and could even risk disablement to this alone.

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Re: 38 cm shells

Post by Bill Jurens » Thu May 16, 2013 6:07 pm

I am pretty sure -- certain, actually -- that your calculations for angles are incorrect. (You should be able to find the relevant equations in my paper on the Loss of HMS Hood). It's difficult to interpret your nomenclature for angles, as it's fairly informal, but for a slope of 20 degrees (bottom of plate inboard) and a target angle of 70 degrees, the resolved obliquity should be around 28 degrees, even assuming a zero degree angle of fall.

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