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Battleship Armor Thread


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#1 DesertFox

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Posted 31 October 2010 - 1750 PM

Decide to move the discussion to her instead of the armor scientific forum. . . .

The United States South Dakota II and Iowa class battleships have an outboard STS armored plate of 1.25 to 1.5 inches.
Heard it discussed both ways as both being effective as a decapping plate and not effective.

The US armored belts though work of the idea that a shell with hit the armor at a steep angle, both lessening the energy delivered to the belt by deflecting and the armor itself being thicker than it would otherwise be.

What I am curious is if the outer plate, assuming that the decapping effect does not work, would it cause the shell to increase its angle and therefore further reduce the energy striking the belt and to angle it such that the belt is effectively thicker.

So people understand how I am comparing armor thickness due to the shell's angle of fall compared to the belt armor.
Posted Image

Using the chart, a 4 degree increase in angle at 22 k yards vs the 16 inch would result in almost a 7% decrease in energy and about an inch of additional armor.

Edited by DesertFox, 31 October 2010 - 2019 PM.


#2 ScottyB

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Posted 03 November 2010 - 1713 PM

Heard it discussed both ways as both being effective as a decapping plate and not effective.


Where did you read that the STS plate wasn't effective at decapping? Off the top of my head I can't think of an exanple of it being tested in combat. Thanks in advance.

Scott

#3 DesertFox

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Posted 04 November 2010 - 0930 AM

Where did you read that the STS plate wasn't effective at decapping? Off the top of my head I can't think of an exanple of it being tested in combat. Thanks in advance.

Scott


More like looking at Nathan's page and hearing people argue over it.
He also revisited it and not sure of the proper conclusions.

One main argument is that no source seems to support that the outer plate does have the purpose for decapping rounds.

Edit-1: I was reading Friedman on US Naval Weapon systems and he does refer to Nathan Okum in his writings

Edited by DesertFox, 04 November 2010 - 1209 PM.


#4 D Simcock

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Posted 05 November 2010 - 0000 AM

From memory Nathan Okun stated that his revised calculations suggest that the US STS plate was too thin for decapping most batteship shells of WWII era. I may have been effective against 14in shells but not against anything larger.
Littorio's decapping plates may well have been more effective, but they were thicker than on the US ships.

The incline on the US armour is a slight adavantage versus non-inclined armour, but is negated by the fact the belt is thin (only 12.2 in) compared to others.

The KGV's belt is supposedly at a disadvantage from not being inclined, but it was thick (14-15 in) and British battleship armour was much higher quality than anyone else's. Taking quality into account, the KGV's may have had the best belt armour protection of the WWII battleships. Shame about the turrets and guns though...

#5 DesertFox

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Posted 05 November 2010 - 0633 AM

Those calculations of energy deflection and increased thickness are calculated using the formula values for each.
As target angle increases, the thickness increases at a logarithmic rate. At about 24 K yards, due to angle of fall, the 12.2 inch belt will actually probably be thicker (using a 16 inch round) due to angle than the 14 inch non angled belt.

The progression on energy deflected is a bell curve however. Its increase goes up until 90 degrees where 100% of energy is deflected. Formula energy reduction = ((sin(angle))^2)*original energy

The big disadvantage I see with an angled belt is that you effectively always take damage. It cannot just go splat on the belt.

My idea is that when you hit the 1.5 inch STS layer, it likely will not decap but it will increase the angle of the projectile which both increases effective armor thickness and amount of energy deflected. Think of it like hitting glass with a bullet, the glass will deflect the bullet often creating a miss. In this case you are not generating a miss but just changing the angle of the shell.

Edited by DesertFox, 05 November 2010 - 0648 AM.


#6 D Simcock

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Posted 05 November 2010 - 1005 AM

Seems doubtful. Unless decapping occurred, having thin layers of weather deck armour preceding the main deck armour didn't seem to help much with plunging fire at extreme ranges, which still involved angles much greater than you're talking about.

Your loss of energy (presumably proportional to depth of penetration) seems a bit extreme with increasing angle. The following link shows much smaller losses in penetration with shells coming in at angles of obliquity of 20 and 30 degrees.
http://www.navweaps....R_15-42_mk1.htm

For a serious discussion on this, you will most likely have to go to the Armor Scientific Forum.

#7 DesertFox

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Posted 05 November 2010 - 1243 PM

Seems doubtful. Unless decapping occurred, having thin layers of weather deck armour preceding the main deck armour didn't seem to help much with plunging fire at extreme ranges, which still involved angles much greater than you're talking about.

Your loss of energy (presumably proportional to depth of penetration) seems a bit extreme with increasing angle. The following link shows much smaller losses in penetration with shells coming in at angles of obliquity of 20 and 30 degrees.
http://www.navweaps....R_15-42_mk1.htm

For a serious discussion on this, you will most likely have to go to the Armor Scientific Forum.


I actually first tried to introduce the ideas I want to discuss into the "Armor Scientific Forum" but did not get much of a response so though I would go here. I do need somebody who understands what is being discussed so that I can see where and if my ideas go wrong and what the next step is.

The effect I am talking about might also be called "Glancing effects" where a certain amount of energy is pushed in a different direction. Nathan Okum talks about the same basic effect in his discussion of decks. He also discusses the idea that when you pass through one layer before passing through another (when separated), that the angle will change as well.

Edit: Think f it a little like punching a thick pane of glass with your fist. A straight vertical, most of that energy goes straight into the glass and shatters the glass. Imagine the glass at a 45 degree angle. Much of that energy then deflects to the side and you are much less likely to shatter the glass.

Edited by DesertFox, 05 November 2010 - 1341 PM.


#8 D Simcock

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Posted 05 November 2010 - 1555 PM

There will be some defletion effect, but it is likely to be insignificant given the angle of obliquity is very low, and the plate's thinness. Significant deflection may be more significant on the main belt, being much thicker and aided by the incline belt's incline. Deflection with deck armour will be more significant because even at maximum range the angles of impact are much greater.

#9 DesertFox

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Posted 05 November 2010 - 1602 PM

At least we seem to be discussing at similar levels. I am really only referring to a few degree change anyway which would make the main belt slightly more effective




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