Another Iron clad armor question


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#2
A4CDC26E-487C-4713-9ABD-46E486622511.jpeg


It depended on circumstances and availability. As I recall, the Confederacy was able to roll up to 2 inch thick armor at Tredegar in Richmond; two layers of this were laid at right angles to each other to form the 4 inch overall armor plate on the first CSS Virginia. (This was generally not as strong as a single 4 inch plate.) In other cases, strap iron or actual sections of rails were used (above, in CSS Georgia). The United States was generally better off in its ability to roll heavy iron plate, but there was never enough to go around.
 
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rebelatsea

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#3
In addition to Tredegar, there was Scofield & Markham at Atlanta. Two major sources of rolled iron plate, almost all 2" thick although CSS Mississippi's plate was 1.25" plate in three layers. I have not solved the reason why her iron wasn't 2". Eason Bros at Charleston had the capability but so far as is known didn't produce armour There was also a foundry at Mobile rifling guns, and this may have also produced plate as CSS Montgomerey carried 4.5 " iron - an odd thicknessLate in the war Charlotte Naval Ironworks was experimenting with 5" plate.
 

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In addition to Tredegar, there was Scofield & Markham at Atlanta. Two major sources of rolled iron plate, almost all 2" thick although CSS Mississippi's plate was 1.25" plate in three layers. I have not solved the reason why her iron wasn't 2". Eason Bros at Charleston had the capability but so far as is known didn't produce armour There was also a foundry at Mobile rifling guns, and this may have also produced plate as CSS Montgomerey carried 4.5 " iron - an odd thicknessLate in the war Charlotte Naval Ironworks was experimenting with 5" plate.
2" plate was also rolled at the Shelby Iron Works in Shelby, Alabama and this plate was used on the CSS Tennessee along with other Mobile area vessels such as the CSS Nashville, CSS Huntsville and the CSS Tuscaloosa.
 
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Saphroneth

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#6
Analysis both contemporary and later has revealed that:

Wrought is better than cast as it absorbs the energy better.
Rolled is superior to hammered for the same thickness, because it is more cohesive and more even.
Layers are significantly inferior to a single thickness piece of the same total weight.
Backing armour with the right amount of timber can double or more the resistance, as well as prevent spalling.
Contemporary armour can be measured in consistent terms of durability based on foot-tons of energy required per inch of circumference of the round.


What this means (as demonstrated in a contemporary British treatise) is that two guns of different bores and shot weights but with the same total muzzle energy per inch of circumference of the round will have the same terminal effect on armour.

This is why I'd argue that Confederate ironclad armour was superior to Union, at least technically - a Confederate ironclad with 2x2 layers (or 1x4.5 layer) of rolled wrought iron, backed, will resist shot of a given effectiveness, while a Union Monitor able to resist the same shot will require a much greater weight per armour square foot, because it's making up that resistance with several 1" layers.


It's actually possible to use formulae to calculate the amount of (single plate unbacked) wrought iron that a given cannon should be expected to pierce in ideal conditions, though I believe these formulae had not been worked out at the time.
 

67th Tigers

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#7
The machinery you had defined what was possible.

The plates for almost all monitor turrets were rolled by Abbott of Baltimore. They had the only facility for producing 10 ft long plates, and the thickness was defined by the mass of iron in the bar fed in, and the height of the rollers. Because the mass was set, the cross-section would always be 40 sq. ins. The final plates were 9 ft long, and rolled down to 1 inch thick, meaning they were 40 inches wide.

The length defined the height of a monitor turret - the plates were 9 ft high when stood up, and so the turrets were always 9 ft high. If you could heighten the rollers to 2", then the plate would only be 20 inches wide, and hence a greater part of the armour would be weakened by rivets passing through in.

The Virginia was plated with plates 8 ft long, 2" thick and 8" wide. It should be obvious the Tredegar was forging smaller bars to be rolled. This meant there were a lot more rivets needed, which weakened the structure.

Conversely, Warrior's plates were 12 ft long, 3 ft wide and 4.5" thick. They individually each massed 21 times a Monitor plate (see below). This is another reason for the apparent strength of RN plates vs USN plates of a similar thickness - the shot was far less likely to strike at a weak joint between plates.

Virginia's plates: 392 lbs
Monitor's turret plates: 1,101 lbs
Warrior's plates: 23,328 lbs
 
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#8
In addition to Tredegar, there was Scofield & Markham at Atlanta. Two major sources of rolled iron plate, almost all 2" thick although CSS Mississippi's plate was 1.25" plate in three layers. I have not solved the reason why her iron wasn't 2". Eason Bros at Charleston had the capability but so far as is known didn't produce armour There was also a foundry at Mobile rifling guns, and this may have also produced plate as CSS Montgomerey carried 4.5 " iron - an odd thicknessLate in the war Charlotte Naval Ironworks was experimenting with 5" plate.
In the case of the Montgomery 3 x 1.5 inch plate? I know that pre-war one of the RR at New Orleans was using 1.5 inch strap iron. In Lt. Carter's Letter Book from Shreveport there is a reference to a mill being completed in NE Texas with a comment that it was 300 miles from Galveston and any production would have to be hauled by wagons drawn by livestock.
 

redbob

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#9
View attachment 304271

It depended on circumstances and availability. As I recall, the Confederacy was able to roll up to 2 inch thick armor at Tredegar in Richmond; two layers of this were laid at right angles to each other to form the 4 inch overall armor plate on the first CSS Virginia. (This was generally not as strong as a single 4 inch plate.) In other cases, strap iron or actual sections of rails were used (above, in CSS Georgia). The United States was generally better off in its ability to roll heavy iron plate, but there was never enough to go around.
A section of the CSS Georgia's armor:
casemate+profile.jpg
 

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#10
In the case of the Montgomery 3 x 1.5 inch plate? I know that pre-war one of the RR at New Orleans was using 1.5 inch strap iron. In Lt. Carter's Letter Book from Shreveport there is a reference to a mill being completed in NE Texas with a comment that it was 300 miles from Galveston and any production would have to be hauled by wagons drawn by livestock.
There was iron and coal production in NE Texas (north of Tyler), but the quality was mediocer and quantity was small. I don't recall hearing of a mill in the area.
 

rebelatsea

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In the case of the Montgomery 3 x 1.5 inch plate? I know that pre-war one of the RR at New Orleans was using 1.5 inch strap iron. In Lt. Carter's Letter Book from Shreveport there is a reference to a mill being completed in NE Texas with a comment that it was 300 miles from Galveston and any production would have to be hauled by wagons drawn by livestock.
Good point, although why that should be when 2 x 2" and even 3 x2" had become standard, unless a stache of strap iron was available for the taking at the right time.
 

rebelatsea

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#13
2" plate was also rolled at the Shelby Iron Works in Shelby, Alabama and this plate was used on the CSS Tennessee along with other Mobile area vessels such as the CSS Nashville, CSS Huntsville and the CSS Tuscaloosa.
Thank you I forgot Shelby and of course Etowah turned out plate which was rolled / re rolled at Atlanta.
 
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#14
Good point, although why that should be when 2 x 2" and even 3 x2" had become standard, unless a stache of strap iron was available for the taking at the right time.
I think this is a good point. Think how many boats had their woodwork and machinery essentially complete but just sat there waiting for iron. If you've got it, use it - regardless of type. With the loss of Atlanta did they think the pixies were going to deliver plate? Its a little Neaderthal, but reversed T-rail would have worked for me. One clinker may not have been the iron. They may have come up short on fasteners. Spiked rail is not a good idea. You need to bolt it. What I don't understand is why the incomplete hulls and Montgomery were not moved upriver from Mobile. The only answer I can come up with for the Montgomery is that they lacked crewmen. But they had a care-taking crew for the Baltic after they stripped her iron and Army gun crews had performed adequately in the Trans-Mississippi. Why didn't they use her for supporting fire for the southern forts to the east of Mobile?
 

rebelatsea

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I think this is a good point. Think how many boats had their woodwork and machinery essentially complete but just sat there waiting for iron. If you've got it, use it - regardless of type. With the loss of Atlanta did they think the pixies were going to deliver plate? Its a little Neaderthal, but reversed T-rail would have worked for me. One clinker may not have been the iron. They may have come up short on fasteners. Spiked rail is not a good idea. You need to bolt it. What I don't understand is why the incomplete hulls and Montgomery were not moved upriver from Mobile. The only answer I can come up with for the Montgomery is that they lacked crewmen. But they had a care-taking crew for the Baltic after they stripped her iron and Army gun crews had performed adequately in the Trans-Mississippi. Why didn't they use her for supporting fire for the southern forts to the east of Mobile?
CSS Powell was apparently neither armed not armoured, although sent to Mobile for the purpose. CSS Montgomery was reported by the Union to be both armed and armoured. I think you are right ,they couldn't man the latter.
 

rebelatsea

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CSS Powell was apparently neither armed not armoured, although sent to Mobile for the purpose. CSS Montgomery was reported by the Union to be both armed and armoured. I think you are right ,they couldn't man the latter.
As to why she wasn't given a temporary crew and sent to support the forts alongside CSS Nashville, I'm going to hazard a wild guess - I wonder if they had no ammunition (I'm guessing her guns were rifled and banded smoothbores) or even maybe no fuel?
 
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#17
Eason Bros at Charleston had the capability but so far as is known didn't produce armour
Perhaps because of the shortage of iron at Charleston. Lee's ram, started in 1862, never got iron before it's single use in Aug 1863. Lee was literally scouring the countryside farms for pig iron or anything else he could lay his hands on all through 1863. In that time, it seems just about all iron went to the ironclads made there. Just a thought.
 

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#18
As to why she wasn't given a temporary crew and sent to support the forts alongside CSS Nashville, I'm going to hazard a wild guess - I wonder if they had no ammunition (I'm guessing her guns were rifled and banded smoothbores) or even maybe no fuel?
When a ship is not used, my first thought is crew and second is leaking hull.
 
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Perhaps because of the shortage of iron at Charleston. Lee's ram, started in 1862, never got iron before it's single use in Aug 1863. Lee was literally scouring the countryside farms for pig iron or anything else he could lay his hands on all through 1863. In that time, it seems just about all iron went to the ironclads made there. Just a thought.
Hi Littlefield - do you know how heavily they intended to iron the Torch?
 
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#20
Hi Littlefield - do you know how heavily they intended to iron the Torch?
"No 2- Represents a transverse section of the vessel showing the arrangement of the [iron] shield within the same immersed five feet below the water line. The armour for the shield is of three thicknesses of three inch plates backed by over two feet of oak. The sides of the vessel above the foot of the shield is of ordinary sheet iron after the manner of merchant vessels but divided transversely into compartments each ten feet in length."
-Francis Lee (undated report to Beauregard)
 



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