Scale model of Achille, a typical French seventy-four of the Téméraireclass at the beginning of the 19th century.
|Type||ship of the line|
|Tons burthen||2,000–3,000 bm|
|Length||161–182 ft (49–55 m)|
|Beam||46 ft (14 m)|
|Draught||23 ft (7 m)|
|Sail plan||ship rig|
The "seventy-four" was a type of two-decked sailing ship of the line, which nominally carried 74 guns. It was developed by the French navy in the 1740s, replacing earlier classes of 60- and 62-gun ships, as a larger complement to the recently-developed 64-gun ships. Impressed with the performance of several captured French seventy-fours, the British Royal Navy quickly adopted similar designs, classing them as third rates. The type then spread to the Spanish, Dutch, Danish and Russian navies.
The design was considered a good balance between firepower and sailing qualities. Hundreds of seventy-fours were constructed, becoming the dominant form of ship-of-the-line. They remained the mainstay of most major fleets into the early 19th century. From the 1820s, they began to be replaced by larger two-decked ships mounting more guns. However some seventy-fours remained in service until the late 19th century, when they were finally supplanted by ironclads.
Standardising on a common ship size was an appealing ideal for naval administrators and bureaucrats. Although the seventy-four was a common type, the ship classes were not identical, even within the same navy. In the period 1750–1790, seventy-fours could measure from just under 2,000 to 3,000 tons burthen. The armament could also vary considerably, with the lower deck mounting 24-pounder to 36-pounder long guns, and a variety of calibres (sometimes including a few carronades) used on the upper deck. Some seventy-fours of the Danish navy only carried 70 guns. 
The first 74-gun ships were constructed by the French as they rebuilt their navy during the early years of the reign of Louis XV. The new ship type was a very large two-decker big enough to carry the largest common type of gun (36-pounders) on the lower gun deck, something only three-deckers had done earlier. This great firepower was combined with very good sailing qualities compared to both the taller three-deckers and the shorter old-style 70-gun two-deckers, making the 74 the perfect combination of the two. A disadvantage of the 74 was that it was relatively expensive to build and man compared to the older type of two-decker.
The 74-gun ship carried 28 (24-pounders- to 36-pounders) on the lower gun deck, 28–30 (18- to 24-pounders) on the upper gun deck, and 14–18 (6- to 12-pounders) on the upper works.  Crew size was around 500 to 750 men depending on design, circumstances and nationality, with British ships tending to have smaller crews than other navies. The French had large and small seventy-fours, called "grand modèle" and "petite modèle", the waterline length of a "grand modèle" seventy-four could be up to 182 feet.  This was copied by the Royal Navy in about two dozen such ships of its own, such as HMS Colossus where they were known as Large, while the other seventy-fours built to be between 166–171 feet (51–52 m) were known as Common. 
Given the construction techniques of the day, the seventy-four approached the limits of what was possible. Such long hulls made from wood had a tendency to flex and sag over time. Increased maintenance could counter this to some extent, but this was of course costly. This limited the success of the even bigger two-deck 80-gun ships that were built in small numbers after the seventy-four had been introduced. Three-deckers did not have the same problem due to their additional deck giving more rigidity.
The significance of the 74s however is hard to overstate, as shown by a summary of the ships of the line for all nations that were in commission at any time during the Revolutionary/Napoleonic Wars period.
The Royal Navy captured a number of the early French 74-gun ships during the War of the Austrian Succession (for example, Invincible, captured at the first battle of Cape Finisterre in 1747) and the Seven Years' War and was greatly impressed by them compared to its own smallish 70-gun ships. As a result, it started building them in great numbers from about 1760, as did most other navies. Navies that were restricted by shallow waters, such as the Dutch and Scandinavian navies, at least early on tended to avoid the 74-gun ship to a certain degree due to its size and draught, preferring smaller two-deckers instead. Even so, the seventy-four was a standard feature in all European navies around 1800. Only a handful of 74-gun ships were commissioned into the United States Navy; the US Navy's early sea power concentrated on its frigates.
The type fell into disuse after the Napoleonic Wars, when improved building techniques made it possible to build even bigger two-deckers of 84 or even 90 guns without sacrificing hull rigidity.
The last seventy-four, the French Trafalgar veteran Duguay-Trouin , was scuttled in 1949. Her stern ornamentation is on display at the National Maritime Museum, Greenwich. In addition, dozens of ship models exist, produced as part of constructing the real ships, and thus believed accurate both externally and internally.
A frigate is a type of warship. In different eras, the roles and capabilities of ships classified as frigates have varied somewhat.
In the rating system of the Royal Navy, a third rate was a ship of the line which from the 1720s mounted between 64 and 80 guns, typically built with two gun decks. Years of experience proved that the third rate ships embodied the best compromise between sailing ability, firepower, and cost. So, while first-rates and second-rates were both larger and more powerful, third-rate ships were the optimal configuration.
In 1603 all English warships with a compliment of fewer than 160 men were known as 'small ships'. In 1625/26 to establish pay rates for officers a six tier naval ship rating system was introduced. These small ships were divided into three tiers, Fourth, Fifth and Sixth rates. Up to the end of the 17th century the number of guns and the compliment size was adjusted until the rating system was actually clarified. A 'Fourth Rate' was nominally a ship of over thirty guns with a complement of 140 men.
In the rating system of the Royal Navy used to categorise sailing warships, a second-rate was a ship of the line which by the start of the 18th century mounted 90 to 98 guns on three gun decks; earlier 17th-century second rates had fewer guns and were originally two-deckers or had only partially armed third gun decks. A "second rate" was the second largest class of warships in a hierarchical system of six "ratings" based on size and firepower.
In the rating system of the Royal Navy used to categorise sailing warships, a fifth rate was the second-smallest class of warships in a hierarchical system of six "ratings" based on size and firepower.
The rating system of the Royal Navy and its predecessors was used by the Royal Navy between the beginning of the 17th century and the middle of the 19th century to categorise sailing warships, initially classing them according to their assigned complement of men, and later according to the number of their carriage-mounted guns. The rating system of the Royal Navy formally came to an end in the late 19th century by declaration of the Admiralty. The main cause behind this declaration focused on new types of gun, the introduction of steam propulsion and the use of iron and steel armour which made rating ships by the number of guns obsolete.
Santísima Trinidad was a Spanish first-rate ship of the line with 112 guns. This was increased in 1795–96 to 130 guns by closing in the spar deck between the quarterdeck and forecastle, and to 140 guns around 1802, thus creating what was in effect a continuous fourth gundeck although the extra guns added were actually relatively small. She was the heaviest-armed ship in the world when rebuilt, and bore the most guns of any ship of the line outfitted in the Age of Sail.
The Océan-class ships of the line were a series of 118-gun three-decker ships of the line of the French Navy, designed by engineer Jacques-Noël Sané. Fifteen were completed from 1788 on, with the last one entering service in 1854; a sixteenth was never completed, and four more were never laid down.
The Magenta class consisted of two broadside ironclads built for the French Navy in the early 1860s. They were the only ironclad two-deckers ever built, and the first ironclads to feature a naval ram.
The 1745 Establishment was the third and final formal establishment of dimensions for ships to be built for the Royal Navy. It completely superseded the previous 1719 Establishment, which had subsequently been modified in 1733 and again in 1741. Although partially intended to correct the problems of the ships built to the earlier Establishments, the ships of the 1745 Establishment proved just as unsatisfactory, and important changes in the make-up of the Admiralty and Navy Boards finally led to the end of the establishment era by around 1751.
The Roebuck-class ship was a class of twenty 44-gun sailing two-decker warships of the Royal Navy. The class carried two complete decks of guns, a lower battery of 18-pounders and an upper battery of 9-pounders. This battery enabled the vessel to deliver a broadside of 285 pounds. Most were constructed for service during the American Revolutionary War but continued to serve thereafter. By 1793 five were still on the active list. Ten were hospital ships, troopships or storeships. As troopships or storeships they had the guns on their lower deck removed. Many of the vessels in the class survived to take part in the Napoleonic Wars. In all, maritime incidents claimed five ships in the class and war claimed three.
The 18-pounder long gun was an intermediary calibre piece of naval artillery mounted on warships of the Age of Sail. They were used as main guns on the most typical frigates of the early 19th century, on the second deck of third-rate ships of the line, and even on the third deck of late first-rate ships of the line.
The 24-pounder long gun was a heavy calibre piece of artillery mounted on warships of the Age of Sail. 24-pounders were in service in the navies of France, Spain, Great Britain, the Netherlands, Sweden, and the United States. They were comparable to the Canon de 24 Gribeauval used by the French Army as its largest piece of siege artillery. 24-pounders were used as main guns on the heaviest frigates of the early 19th century and on fourth-rate ships of the line, on the second deck of first-rate ships of the line, and on the second deck of a few large third-rates.
The 12-pounder long gun was an intermediary calibre piece of artillery mounted on warships of the Age of sail. They were used as main guns on the most typical frigates of the early 18th century, on the second deck of fourth-rate ships of the line, and on the upper decks or castles of 80-gun and 120-gun ships of the line. Naval 12-pounders were similar to 12-pound Army guns in the Gribeauval system: the canon lourd de 12 Gribeauval, used as a siege weapon, and the canon de 12 Gribeauval, which was considered a heavy field artillery piece.
The Commission de Paris was a body of French naval engineers gathered in 1821 to design the future frigates and ships of the line of the French Navy for the post-Empire era. Presided by Jacques-Noël Sané, the Commission comprised Jean-Marguerite Tupinier, Pierre Rolland, Pierre Lair and Jean Lamorinière.
The Leon Trionfante-class were a class of at least fourteen 70-gun third rate ships of the line built by the Venetian Arsenale from 1716 to 1785, in four different series with minor changes in the ships' length. In 1797, when Venice fell to the French, Napoleon captured several ships of the class, still unfinished in the Arsenal: he chose one of them, forced the shipbuilders to have it completed and added it to his fleet en route for Egypt. After Campoformio, the remaining vessels were destroyed by the French to avoid their capture by the Austrian Empire.
The Khrabryi class was a pair of ships of the line built for the Black Sea Fleet of the Imperial Russian Navy in the 1840s and early 1850s. The class comprised two ships: Khrabryi and Imperatritsa Maria. The two ships were built as part of a naval expansion program aimed at strengthening the Black Sea Fleet during a period of increased tension with Britain and France over the continued decline of the Ottoman Empire. Both ships saw active service during the Crimean War, with Imperatritsa Maria serving as Pavel Nakhimov's flagship at the Battle of Sinop in November 1853, where the Russians annihilated an Ottoman squadron. The two ships were withdrawn to Sevastopol after the British and French intervention and were trapped there during the Siege of Sevastopol until 1855, when both were scuttled to block the harbor entrance.
The Sultan Makhmud class was a group of eight 84-gun ships of the line built for the Black Sea Fleet of the Imperial Russian Navy. The class comprised Sultan Makhmud, Trekh Ierarkhov, Arkhangel Gavriil, Selafail, Uriil, Varna, Iagudiil, and Sviatoslav. They were built as part of a naval expansion program directed against the British and French, which Russia viewed as competitors to fill the power vacuum left by the continued decline of the Ottoman Empire. The ships represented an improvement over the traditional seventy-four, as improved building techniques allowed naval designers to build larger, more heavily armed vessels without sacrificing the hull strength that had made the seventy-fours such effective warships.
The 64-gun ship of the line was a type of two-decker warship defined during the 18th century, named after the number of their guns. 64-guns had a lower battery of 24-pounders, and an upper battery of 12-pounders. Heavier variants with 18-pounder on the upper deck also existed.