In late 18th century, the backbone of the English battle fleet was composed of third-rate 74-gun ships - armed with a combination of 28 32-Pounder guns in the lower deck, 28 18-Pounder guns in the upper deck and 18 9-Pounder guns in the quarterdeck and in the forecastle. HMS Zealous was an Edgar class ship of the line. Similarly to the Bellona class, the Edgar class was one of the designs by Thomas Slade, using a slightly modified version of the original Arrogant design.