Copper sheathing on hulls and lighter cannons are two examples of improvements in Royal Navy ship design in the 18th century.

Despite the system of Establishments in the 18th century, which standardized the design of Royal Navy ships and hindered the advance of ship design, there was a steady improvement in the efficiency of vessels. Important changes took place in steering, sails, guns and the underwater protection of hulls.

Underwater protection

In the early 18th century, underwater hulls were smeared with a compound, such as a mixture of tallow, sulphur and resin, to repel wood-boring 'shipworm' and other molluscs like barnacles. This was a common method of protection but it did not stop weed growing on the hull. Marine growth such as shellfish or weed affected sailing ability.

After much experimentation, it was found that covering the underwater hull with copper plates kept off both worm and weed. Between 1778 and 1781 most of the fleet was coppered.

Gunnery

The number and types of the guns allotted to each ship type were formally laid down in periodic Gun Establishments. By 1700 bronze or 'brass' guns had been largely replaced by cast iron, which was much cheaper. Bronze, however, was still used for the guns of First Rates for some time.

In 1716, guns lost their medieval names and became known by the weight of the shot they fired. The 42-pounder – the old cannon-of-seven – was the largest but it was found only on the lower deck of the First Rates. The principal weapon of ships of the line was the 32-pounder – the largest gun which could be used efficiently in action.

An important innovation was the carronade, which appeared in service in the late 1770s as an extra weapon on large ships. This large-bore but lightweight gun threw a heavy ball at low velocity over a short range. Far fewer men were needed to operate it than were required for a cannon.