 Acutely aware of the fact, the Confederacy's chief naval engineer John L. Porter (co-designer of "Virginia", which was likewise powered by her original, wooden frigate engine) had originally envisioned his subsequent casemate ironclad designs to be equipped with superior British-made engines, theoretically giving them a cruising speed of at least ten knots.However, the Union blockade meant that very few such engines reached Confederate naval shipyards, forcing them to do with whatever was on hand (typically, engines stripped from trapped wooden blockade runners), and thus most of their ironclads were not able to surpass a speed of four to six knots at most.As an example, the engines of the first two ironclads of the Charleston Squadron, the and , were so weak that they were unable to overcome Charleston Harbor's five knots tides under their own power.