During the 17th to 19th centuries, the British Royal Navy had a number of unrated vessels under the command of lieutenants and commanders.
The British Royal Navy rated their warships from First Rate to Sixth Rate. Captains and high-ranking naval officers commanded these ships, while commanders and lieutenants were put in charge of smaller ‘unrated’ vessels such as sloops and cutters.
A sloop of war was a vessel commanded by an officer with the rank of commander. Sloops could be armed with between 10 and 18 guns, be ship rigged or brigs (two-masted square rig) and were capable of most of the tasks undertaken by frigates, with the exception of fleet reconnaissance. They were often armed with carronades (a short, smoothbore cannon), giving them a heavy punch at close range. The cruiser class was the most numerous class of sailing warships ever built. They carried a crew of 120 men.
Bomb vessels and fireships
Developed from two-masted craft (ketches) armed with mortars for shore bombardment, and first used by the French in the late 17th century, the bomb vessel of the late 18th century had ship rig (three masts). The fireships were intended to be used to set enemy ships on fire, and were often converted merchant ships, though some were specially built for the Royal Navy. Both the bomb vessel and the fireship were rarely used for their designed role, but used as patrol or convoy escort sloops.
Gunboats and gunbrigs
These were small, two-masted vessels, at a Lieutenant’s command, and originally intended for anti-invasion patrol. Later, they developed into more capable vessels fit for a variety of tasks.
Cutters were usually the smallest commissioned ships in the fleet. Developed from craft used by English smugglers, these single-masted vessels were built for speed. They were employed as patrol boats and dispatch carriers. Schooners, two masted fore- and aft-rigged vessels were used for similar purposes.