Armored Ship Misconceptions

It’s obvious from the preceding post (see, "Fitzgerald Collision") that there is a lot of misguided and incorrect thought out there about ship size and the impact of armor on a ship’s performance.  I’m reading consistent statements that modern ships can’t bear the weight of armor without seriously impacting endurance, range, and speed.  That’s just absolute bilgewater and betrays a lack of knowledge about previous ship designs – WWII, in particular.  So, to help put ships and armor into an actual and factual context, let’s look at WWII ship designs versus today.

In the following discussion, I’m going to generically refer to “armor” as the total of hull plating and any add-on armor that may have been present.

Here’s the relevant specifications for the Burke class DDG.

Burke Class Flt IIa

Length  509 ft

Displacement  9200 t

Range  4400 @ 20 kts

Speed  30+ kts

Armor  5/8” – 7/16” hull plating, 7/16” – 1/2” deck (1);  no additional external armor

Now let’s look at some WWII designs.

Portland Class Cruiser (ex. USS Indianapolis)

Length  610 ft

Displacement  10,000 t

Range  13,000 @ 15 kts

Speed  33 kts

Armor  “The ships were completed with belt armor 5 inches thick over the magazines and 3.25 inches elsewhere.  Armored bulkheads were between 2 inches and 5.75 inches, deck armor was 2.5 inches, the barbettes were 1.5 inches, the gunhouses were 2.5 inches, and the conning tower was 1.25 inches  …”  (2)

We see that the Portland class cruiser, armed with 9x 8” guns and 8x 5” guns, carried armor ranging up to 5.75” and still managed to make 33 kts with a range of 13,000 nm.  I guess WWII ship designers didn’t realize this was impossible.

Okay, you say, a large cruiser could carry armor but how about a smaller ship – a ship the size of, or smaller than, a Burke?  How about the Fletcher class destroyers?

Fletcher Class Destroyer (4)

Length  376 ft

Displacement  2500 t

Range  5500 @ 15 kts

Speed  36 kts

Armor  1/2” – 3/4” hull and deck

The Fletcher class, much smaller than a Burke, had its thinnest plating equal to the Burke’s thickest and had heavier, thicker 3/4” plating in many locations, in addition.  So, the Fletcher, despite being significantly smaller than a Burke, carried more armor and had as good range and speed.  I guess WWII ship designers didn’t realize this was impossible.

Let’s take a look at one more, the Atlanta class light cruiser.

Atlanta Class Light Anti-Aircraft Cruiser

Length  541 ft

Displacement  7400 t

Range  8500 @ 15 kts

Speed  33 kts

Armor  1.1” – 3.5” belt, 1.25” deck (3)

Hmm ……..  Yet another example of a ship slightly longer than the Burke, significantly lighter, and yet has larger amounts of armor, greater range, and equal speed.  I guess WWII ship designers didn’t realize this was impossible.

I can go on with example after example but the point is made.  For a properly designed ship, there is no range, endurance, or speed penalty.  Those who believe that modern ships can’t carry armor without significant performance penalties are just ignorant of what was common practice decades ago.  Every US surface combatant of WWII had far more armor than a Burke and yet had equal or superior range and speed.

There is no reason not to armor our ships commensurate with their size and purpose.

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(1)Unpublished cross sectional construction drawing for Burke class

(2)Wikipedia, retrieved 21-Jun-2017,

https://en.wikipedia.org/wiki/Portland-class_cruiser

(3) Wikipedia, retrieved 21-Jun-2017,

https://en.wikipedia.org/wiki/Atlanta-class_cruiser

(4)United States Navy Destroyers of World War II, John C Reilly, Jr., Blandford Press, 1985

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