Bismarck class turret protection

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Tiornu
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Post by Tiornu » Wed Oct 18, 2006 11:39 pm

I can certainly believe I was optimistic about the 14in shell's chances against the faceplate. Do the figures from that table refer to British armor? Do they assume new-gun or average velocity? What definition of penetration do they use? I was referring specifically to holing. At what angle are Bismarck's faceplates inclined?

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Post by foeth » Thu Oct 19, 2006 7:53 am

Just interjecting, but is the hyphen only present when "sloped-back" is an adjective? Example:

The armour was sloped back
The sloped-back armour

That's British armor of course.

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Post by RF » Thu Oct 19, 2006 8:19 am

foeth wrote:Just interjecting, but is the hyphen only present when "sloped-back" is an adjective? Example:

The armour was sloped back
The sloped-back armour

That's British armor of course.
Thats the beauty of the English language. Otherwise its backsloped armour in any other language....
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Post by Tiornu » Thu Oct 19, 2006 8:40 am

"Just interjecting, but is the hyphen only present when "sloped-back" is an adjective?"
Yes. The two words together to form the adjective. You see similar constructions when amounts or measures serve as adjectives: nine-inch nails, two-thirds majority. The clue in this case is that the word directly before the noun is not itself an adjective; it is not a back plate. This is where the confusion stemmed from.

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foeth
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Post by foeth » Thu Oct 19, 2006 8:45 am

I've got Strunk's "The Elements of Style" within reach, perhaps I should re-read it. I usually hyphenate on feeling. That usually works.

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Post by José M. Rico » Thu Oct 19, 2006 9:02 am

Tiornu wrote:I can certainly believe I was optimistic about the 14in shell's chances against the faceplate. Do the figures from that table refer to British armor? Do they assume new-gun or average velocity? What definition of penetration do they use?
Good questions.

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Post by Tiornu » Thu Oct 19, 2006 9:29 am

The faceplate is such a small surface in drawings that I can't get a good measure of its angle. I'll be happy to accept the British calculated figure as a conservative estimate of penetration range--faceplate hits will be increasingly rare beyond that range anyway--but it won't have any effect on the IZ question as the now infamous back-sloped plate can only hope to keep out the majority of a shell body.
(Note: I could have hyphenated "British calculated" above, changing the syntax of the sentence but not the meaning.)

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Post by Dave Saxton » Thu Oct 19, 2006 2:56 pm

tommy303 wrote:
..... The combination of a longer shallower slope and heavier armour might make it appear to be have been a careful calculation, but then one would have to ask why the turret rear when logic would say it should have been the turret front that needed the attention most.
The "sloped-back" angled facet I'm talking about is the front angled facet, 180mm piece. The penetration of a 15" shell of the front angled facet, is only 170-175mm through out the probable IZ range.

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Post by Dave Saxton » Thu Oct 19, 2006 3:38 pm

I feel that the only data base to properly use are the original penetration data pools when possible. In this case I must place weight on the Krupp curves for the 38cm gun, and not give more weight to modern computor model revisions of the original data.

As to the validity of the Krupp curves, let me quote Hoyer:

"..The inherent meaning is much more closely related to computational method that will take ealier data obtained at the firing ranges and applying these results to the problems of today. Firing data that were collected in many years of work at the firing ranges are systmatically anylized....obviously after such normalization of the curves, values in certian questionable areas of the curves need to be verified by actual firing tests. The finalized characteristics of the curves as they are used for computations is settled here again by expermentation....years of work have produced such penetration graphs for both types of armour plates as well as for all armour peircing shells used by the Navy...the entire material has been incorperated into the so called Atlas of Penetration by the Krupp firm. This penetration atlas forms the basis of all computations..the correctness of these assumptions (energy consumption by the plate) has been verified by experiments.."

What is the diffinition of penetration worked into the Krupp curves?

Hoyer: "..Such sets of curves are established by defining the penetration limit for destoyed and intact projectiles...the Navy is interested mostly in cases that show an intact penetration by the projectile...The value of Vg is the penetration limit for a destroyed projectile and represents the velocity at which the energy of the projectile is just about consumed during the penetration attempt of the target plate, when the projectile becomes stuck intact, or when it breaks apart and an approximate eqivilant weight is deposited in front of and behind the plate...Vh is the zone in which...the lowest speed at which the plate is penetrated and the projectile is still barely intact..."

I'll leave it to others to decide what that corrosponds to in other systems of classification. Nonetheleless, there is a disparity between the Krupp penetration curve values, and the values given in some modern computor models. DK Brown agrees with the penetration calculations of German KC given by Krupp as 350mm at 22,00 yards, and provides a bench mark for comparison:

"German claims for penetration [of the] L4.4 shell were exceptional; 13.8 inches at 22,000 yards... this was more than the thickness of the (6crh) shell used by the old British 15-inch gun, and utterly beyond the capabilities of the the new British 14-inch."

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Post by tommy303 » Thu Oct 19, 2006 5:57 pm

Hi Foerth,

I have Strunk's Elements of style too. English is not the easiest language to learn, to be sure; now with the hyphen properly in place Dave's argument makes much more sense.

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Post by Tiornu » Thu Oct 19, 2006 10:49 pm

"The penetration of a 15" shell of the front angled facet, is only 170-175mm through out the probable IZ range."
So the Bismarck shell is within 5-10mm of achieving the sort of penetration defined in your post, which allows roughly half of the shell weight through the plate. How much of the shell weight would be allowed into the turret in this case? How much of the shell was allowed into Dunkerque's turret by that 15in hit?

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Post by mike1880 » Fri Oct 20, 2006 12:06 am

Here we go again. Obviously if there are lots of decimal points in the results it must be an accurate answer.

And while we're on the subject of what English phrases actually mean:

"DK Brown agrees with the penetration calculations of German KC given by Krupp...'German claims for penetration [of the] L4.4 shell were exceptional'..."

There is absolutely NO implication of agreement in the quoted phrase. Somewhat the reverse; use of the word "claim" implies at best neutrality and at worst outright scepticism.

Mike

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Post by tommy303 » Fri Oct 20, 2006 12:17 am

Hi Tiornu,

If you are referring to the hit on Dunkerque scored by Hood, was not the shell itself rejected and only parts of the cap together with armour fragments driven into the gun chamber?

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Post by Tiornu » Fri Oct 20, 2006 1:59 am

Yes, at least the majority of the shell was rejected. In fact, I believe it deflected with sufficient force to carry into one of the other battleships--if true, this would be the only case I know in which one shell hit two battleships. Dunkerque's roof was face-hardened and more likely to produce splinters. The hit wiped out an entire two-gun crew.

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Post by Dave Saxton » Fri Oct 20, 2006 8:15 pm

Although the Vg or the penetration limit of a damaged projectile served as the foundation of penetration curve calculations, the actual Krupp penetration curves usually used, are based on the Vnot or necessary velocity, and the Vnot has a safety margin built in according to Hoyer:

" (The necessary penetration energy) ...makes the assumption that the consumed energy in the plate, at the marginal limit of the shot, is equal to that energy which is consumed by the penetration of the plate, with an arbitrary surplus."

Additionally, the plate thickness used seems to have been about 3% more than the Vnot curves would indicate as needed.

With this in mind, the numbers make much more sense to me, and it helps me understand how the English could feel confident with 330mm face plates on Vanguard, and 324mm face plates on KGV.

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