De-Capping Layer

Warship design and construction, terminology, navigation, hydrodynamics, stability, armor schemes, damage control, etc.
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tommy303
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Re: De-Capping Layer

Post by tommy303 » Tue Dec 16, 2014 10:42 pm

STS was not face hardened. It was homogenous armour grade plate by Carnagie.

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Re: De-Capping Layer

Post by Garyt » Tue Dec 16, 2014 11:11 pm

So per Okun, it would need a 7.5" HE or Common round to penetrate.

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Re: De-Capping Layer

Post by Thorsten Wahl » Wed Dec 17, 2014 1:22 pm

I would express it harder,
even the main artillery of destroyers is potentially able to produce holes in the waterline, causing some asymmetrical flooding and roughening of the hull, even this kind of damage should not produce real danger directly, but it could slow down the ship.

This kind of damage is not possible for ships possessing external belts, such as KGV or NC classes or even Bismarck class.

It appears to me, that Nathan Okuns calculation potentially underestimates the explosive effect of HE shells, as it is in contradiction to the findings of say german (non systematic) tests.
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Re: De-Capping Layer

Post by Garyt » Wed Dec 17, 2014 7:39 pm

It appears to me, that Nathan Okuns calculation potentially underestimates the explosive effect of HE shells, as it is in contradiction to the findings of say german (non systematic) tests.
Not a shock to me. Okun has done so much research, and has done it rather well, so much that too often IMO he is treated as the "Bible" of Naval Armor and Penetration. I certainly realize there may be other testing out there that does not entirely conform to his findings.

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Re: De-Capping Layer

Post by tommy303 » Wed Dec 17, 2014 7:58 pm

The 5" 38, if I recall, listed 1.5-in penetration at 10,000 yards for direct hits using the AA Common nose fuzed, thin walled shell. This was the predominant ammo type carried by most ships, and only a small percentage of magazine capacity being special common base fuzed Mk46. Special Common could penetrate the armour in question, see:

http://www.navweaps.com/Weapons/WNUS_5-38_mk12.htm

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Re: De-Capping Layer

Post by Garyt » Wed Dec 17, 2014 9:45 pm

One thing about these penetration values - is a "common" shell a little sturdier and does it have a bit less of an explosive filler than a "common" shell?

I'd be curious as to the bursting charge as a percentage of weight on common types compared to high explosive rounds.

I guess what I am trying to ask is that perhaps Okun's calculations are meant for HE or HC rounds as opposed to common rounds?

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Re: De-Capping Layer

Post by Steve Crandell » Wed Dec 17, 2014 9:53 pm

Garyt wrote:One thing about these penetration values - is a "common" shell a little sturdier and does it have a bit less of an explosive filler than a "common" shell?

I'd be curious as to the bursting charge as a percentage of weight on common types compared to high explosive rounds.

I guess what I am trying to ask is that perhaps Okun's calculations are meant for HE or HC rounds as opposed to common rounds?
"Special common" had about a 2 lb bursting charge. AA common had more like 7 or 8 lb.

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Re: De-Capping Layer

Post by tommy303 » Thu Dec 18, 2014 12:24 am

There were also differences in the explosives used. Explosive D (ammonium picrate) with a detonation velocity of 21,300f/s was used in most thin walled AA Common and the semi armour piercing Special Common; however, Composition A, (RDX 91% and 9% plasticizing oil as a desensitizing agent) had a detonation velocity of about 27,000f/s and was favored for AA Common later in the war.

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Re: De-Capping Layer

Post by Garyt » Thu Dec 18, 2014 1:12 am

"Special common" had about a 2 lb bursting charge. AA common had more like 7 or 8 lb.
So a common is about 13% Explosive by weight, the Special Common about 4% by weight.

Compares to about 1.5% in the 16"/50 AP shell, or 8.1% For the 16"/50 HC round.

I fond the rounds for the US Heavy Cruisers helpful in this comparison, as the have AP, SPC, CM and HC rounds. Here is the filler by % of weight:
AP- 1.4%
SPC- 4%
CM- 4.4%
HC - 8.2%

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Re: De-Capping Layer

Post by tommy303 » Thu Dec 18, 2014 7:38 pm

The AA Common 5-in had a much thinner walled shell, much like the German M-Geschoss or Mine Shell, than the normal HC general HE shell.

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