The screw sloop Hartford, launched at Charlestown in 1858, was one of a follow-up class of steamers. (These and other screw steamers of the ’50s were all frigates and sloops; no steam ship-of-the-line was built at Charlestown or any other yard. As we have seen, the era of such large wooden ships was over by the time the Navy was converting to steam.) These were smaller vessels with a shallower draft—better suited to coastal and river operations. As Rear Admiral David G. Farragut’s flagship in victories at New Orleans and Mobile Bay, Hartford was perhaps the most celebrated steamer in the Union Navy.
With propellers, even the most hidebound captains could appreciate the better maneuverability steam gave them during combat. Gradually the tactical roles of steam and sail were reversed, with increasingly efficient and dependable steam engines officially becoming the primary power source and sail the auxiliary. As a matter of economy, however, American vessels continued to use sail whenever possible on long-distance cruises.
Steam technology demanded a whole new set of skills of Charlestown’s mechanics. When the steam battery Fulton II docked there in 1839, the yard could repair only the vessel’s wooden components, having to contract work on the engine to local companies. But by 1845 yard personnel could fully service the screw sloop Princeton. While some carpenters may have made the transition, it is more likely that most of those working with steam machinery had a background in the field.
As the yard adapted to the new age, it underwent a decade of modernization and quickened production preceding the Civil War. The dry dock was lengthened; gas lights were installed; the yard began manufacturing wire rope in 1857. But the most important improvement was a state-of-the-art machine shop—its 240-foot stack long a landmark at the yard—that replaced the old smithery in 1859. It contained such equipment as a machine that could plane a metal surface 10 feet square and a huge lathe capable of handling iron propeller shafts 35 feet long. The facility also helped the yard to incorporate a new technology dramatized (though not introduced) by C.S.S. Virginia: ironcladding.
Sinking of large warships had rarely occurred in naval battle. Solid shot either bounced off thick wooden hulls or left a small, patchable hole. So warships normally just blasted away at each other until one of them, casualties mounting and its deck and rigging a shambles, hauled down its colors. Yet Virginia had sunk or caused to eventually sink two of them in two hours. Its ironcladding allowed it to get close enough to Cumberland to use an ancient but still effective technique, ramming, and close enough to Congress to pound the ship at close range with its broadside shot and big rifles. While ramming would not remain a tactical option, ironcladding was universally adopted as every naval power raced to design hulls that could withstand ever more powerful explosive shells fired from rifled guns (see pages [42]-43).
As in every war, technology helped shape strategy in the Civil War and strategic considerations helped determine how new technologies were applied. The Navy’s major role in the war effort was to blockade some 3,500 miles of Southern coastline. The South’s blockade runners were typically the most advanced examples of British shipbuilding, steam-powered sidewheelers that were often iron- or steel-hulled. In the first year of the war, only about one in eleven of these runners were caught (partly because sidewheelers were still faster than screw steamers), and the Union Navy continued to build, borrow, and buy every vessel it could to strengthen the blockade.
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Steam Propulsion
When steam was introduced as an auxiliary naval power source in the 1820s, paddle-wheels were the initial method of propulsion. In the late 1830s engineers began working with propellers—“screws” in naval terminology. Each technology had its partisans: the sidewheel provided greater combat maneuverability, was suited to riverine warfare, and presented no problems of leakage, as did the screw’s underwater shaft hole. However, the exposed wheels were vulnerable during combat, ate up deck space needed for guns, hindered sail handling, and created more drag than a screw when the vessel was under sail. The launching of the screw warships H.M.S. Rattler in Britain and U.S.S. Princeton in the United States in 1843 signaled the coming ascendancy of screw propulsion. In the historic 1845 tug-of-war between Rattler and an otherwise-identical sidewheeler, the greater efficiency of the screw was publicly confirmed.
