Inside the CSS Georgia's armor: Without preferred rolled plate, railroad iron had to do

(USACE, Savannah District)

I’ve researched and written about the Confederacy’s CSS Georgia for years, noting that the vessel had armor made of railroad iron. But I never really pictured what the outer layer of its casemates might have looked like – until recently.

The U.S. Army Corps of Engineers’ Savannah office, in charge of removing the wreckage in the Savannah River as part of a massive harbor deepening project, released a photograph of a cross section of one of the three casemate chunks remaining on the river bottom.

There they are. Five sliced pieces of T-shaped railroad track wedged in an iron box, corrosion and river sediment filling the gaps. Wow.

It seems almost everything about the CSS Georgia -- which lacked the locomotion to fight the enemy in open water, and instead became a floating battery defending the city – is currently up for study: Exactly how long was the ironclad? How did its propulsion system work? How was the casemate, which housed the Georgia’s guns, put together?

The CSS Georgia was believed to have about 24 inches of pine and oak beneath her iron cladding. Historians and archaeologists are eager to see how all of that was held together. They don’t have blueprints from which to work.

(USACE)

Alvin N. Miller’s machine and shipbuilding business in Savannah produced the “one-off” CSS Georgia in 1862. Estimates on the vessel's length range from 150 to 250 feet.

Bob Holcombe, a naval historian living in Columbus, Ga., said the builders relied on railroad iron for armor because that’s what was available.

Most Confederate ironclads were armored with rolled plate.

“Rolled plate was considered stronger than railroad iron. Railroad iron was used as an expedient,” Holcombe told the Picket. “It was readily available and it did not have to go through the process of being heated and rolled flat; indeed, there were only a couple of rolling mills in the Confederacy capable of rolling 2-inch plate: Tredegar in Richmond and Schofield & Markham in Atlanta.”

What does that mean in battle?

The CSS Georgia, with its casemates at a nearly 45-degree pitch, likely would have stood up to smaller artillery pieces. But, the 11-inch 15-inch Dahlgren might be another matter.

Commenters on the Legacy of the USS Monitor Facebook page have been discussing the photograph of the railroad iron, asserting that the CSS Georgia would have been vulnerable to the Passaic class of Union monitors.

One cites the testing by Texas A&M University on a section of casemate brought up from the CSS Georgia in late 2013. An 8-inch section of rail featured “relatively large impurity inclusions,” an indication of some weakness in the iron.

Holcombe said the Arkansas, Manassas and Louisiana were among the Confederate ironclads fitted with railroad iron armor.

“After the (CSS) Atlanta was pounded by the monitors off Savannah the Confederate States Navy started adding additional plate, which seems to have better resisted the 15-inch guns.”

Cross-section of CSS Georgia rail (USACE)

While some material from the CSS Georgia was recovered after the war, four artillery pieces, parts of the propeller and propulsion system, a boiler and three casemates remain in the swift, dark waters, according to a CNN article. One of the casemates is huge: 68 feet by 24 feet.

Divers have begun preliminary work and recovery; the larger pieces are expected to be brought up in the spring and summer.

The Corps of Engineers said previous recovery efforts, the absence of the lower hull and extensive damage from dredging many years ago will hinder their effort to give a full picture of the CSS Georgia’s operations, which ended in December 1864 when her crew scuttled her as Federal forces rushed to the city.

Still, archaeologists and others want to glean as much as they can during and after the $15 million recovery.

“A detailed examination of the surviving elements of the casemate might support the hypothesis that it was designed to accommodate standard lengths of available iron,” the Corps says on its new website on the CSS Georgia. “Documentation of the rails … could provide evidence that would identify different types of rail used and provide insight into the companies that supplied that material.”

The Corps is not sure all of the casemate can be brought up intact, given most of the wood that held it the vessel is long gone. The wreck site includes disjointed pieces of railroad near the casemates.

Holcombe, who has studied the CSS Georgia and followed developments, said the reason for vessel’s lack of motive power “is the $64,000 question and one I don't think can be fully answered until the machinery comes up and, hopefully, some sections of the hull.

“My gut feeling is that it has more to do with machinery issues and/or hull design than weight of armor, but until everything comes up and is examined it's just a guess.”

Wreck site in the Savannah River (USACE)