I have previously written variously of new technologies that have been tested at the Washington Navy Yard over the years, from lights to radio. Unsurprisingly, there was also a great deal of interest in new ways of protecting and improving the ships that were being built there.
One of the new technologies to be employed during the Civil War was that of iron cladding on ships. While both the French and British navies had built ships protected by iron, it was two American ships so built that first actually battled each other, during the Battle of Hampton Roads in March 1862. Interest in improving the quality of iron plating was, understandably, enormous thereafter. As so often, the Washington Navy Yard was at the forefront of the research.
A month after the battle between the Monitor and the Merrimac, the Washington Evening Star reported that the Navy Yard carpenters were busy building, “iron-clad targets a few hundred yards from the wharf.” Their work was done soon, though the iron to protect it was likely to cause further delay.
Unfortunately, the result of the tests was less than satisfactory. An article from the Alexandria Gazette from November 17th of that year describes what happens when a 10-inch Dahlgren gun is fired at such a target (presumably not one of those parked offshore, however)
A solid shot weighing 130 pounds was thrown at an iron-clad target, at a distance of five hundred yards, perforating the iron plating, four inches thick, as also ten inch oak planking, passing out the other side. The plating was torn into fragments, one piece fling backward into the joiner’s shop, two hundred yards in the rear of the gun, and seven hundred from the target.
Obviously, this would not do. Fortunately, American ingenuity came to the rescue, and a year later, Scientific American reported on the patent that Charles W. S. Heaton had secured the previous April. Heaton had determined that putting wood outside the iron dramatically improved the whole system’s ability to withstand shot.
Graphic illustration of the differences in armoring, as shown in the January 2, 1864 Scientific American (Google books)
Heaton himself described the results:
The Washington Navy Yard may be said to be full of such targets, which (I think) in every instance had been penetrated under such tests as mine was subjected to, and not only penetrated, but the ball generally, after passing clean through the target, penetrates the bank behind them from 4 to 12 feet. My target was one of them, and a damaged one, at that; the only addition I made to it was to cover the lower half with timber, twelve inches thick, which was equivalent in weight to about 5/8th of an inch additional iron. … The ball did not penetrate it, being checked by the timber; the ball was broken to fragments against and in the iron plate, which was broken but not penetrated, the wood backing being practically not injured.
Even better, it turned out, was to then cover the outside with a thin sheet of iron or by adding a thickness of rubber somewhere within. Shortly thereafter, the first monitor using this technology, the USS Onondaga, was built in Greenpoint, Brooklyn by George W. Quintard (pic)