to William Cramp & Sons. William Cramp claimed credit for the detailed design of the ship's hull, but the general design work was done by Merrick & Sons. New Ironsides was long between perpendiculars and long overall. She had a beam of and a draft of . The ship displaced , more than her designed displacement. To minimize her draft, New Ironsides was given a wide beam and a flat bottom. She had a rectangular ram that projected forward from her bow. The ship's crew consisted of 449 officers and men. A two-piece articulated rudder was fitted to New Ironsides, but it proved unsatisfactory in service as the ship became more unmanageable as her speed increased. The rudder was blamed at the time, but the very full shape of the ship's hull aft was the most likely cause as it screened the rudder from the flow of water behind the hull. The ship's hull was coppered to reduce fouling. Propulsion New Ironsides had two simple horizontal two-cylinder direct-acting steam engines driving a single brass propeller. Steam was provided by four horizontal fire-tube boilers at a working pressure of . The engines produced which gave the ship a maximum speed around . New Ironsides carried of coal and her propeller could be disengaged to reduce drag while under sail alone. The ship was barque-rigged with three masts that were used only for long-distance voyages, and were removed, with their rigging, once on station. The best speed under sail and steam together was only about . Armament The ship's main armament was originally going to consist of 16 smoothbore, muzzle-loading Dahlgren guns mounted on the gun deck. However, the navy was less than impressed by the performance of 9-inch Dahlgrens during the Battle of Hampton Roads and wanted more powerful guns. Accordingly, the design changed while the ship was under construction to accommodate fourteen 11-inch Dahlgren guns and two muzzle-loading , 150-pounder Parrott rifles. Two , 50-pound Dahlgren rifles were fitted on the upper deck as chase guns. They were replaced by 60-pound Dahlgren rifles by October 1864. Each 11-inch gun weighed approximately and could fire a shell at a range of at an elevation of 15°. The muzzle-loading Parrott rifles fired a shell at a muzzle velocity of . The 17-caliber guns weighed each. The 50-pounder Dahlgren rifles weighed approximately . The small size of the gun ports limited the guns,