What I mean to say is, was there a new French design during Napoleon's wars that would be seen as revolutionary to the contemporary English?
Or rather, what were the differences between a top of the line English vessel and a French one in the early 1800's?
In the book the mystery supership was the USS Norfolk, which author O'Brian based largely off of the USS Constitution.
The US at the time didn't really have any proper first rates. Instead their capitol ships were six oversized and overgunned frigates. They were designed to live up to the oft sought goal of being able to outfight any ship they couldn't outrun, and were fairly unique for their time. They proved to largely live up to the hope. Constitution herself earning the nickname "old Ironsides" in a battle with HMS Guerriere, because Guerriere wasn't able to penetrate Constitution's oak construction. The Norfolk was a fictional ship, but within the book Far Side of the World it's made quite clear that it was a member of the class.
When it came time to adapt the story to film, Miramax was uncomfortable with a story that cast the Americans as the "bad guys." So the Americans became French and the Norfolk became the Acheron. But the bones of the story remained the same.
Finally it should be emphasized that the USS Constitution was not a first rate ship. During the period a first rate ship like the HMS Victory displaced 3,500 tons and carried over 100 guns. The USS Constitution only had 44 guns and displaced 2,200 tons. It's purpose wasn't to challenge the British battlefleet. Instead it was intended to attack merchants and/or defend them from other commerce raiders.
So the early 1800's did see am advent of a new type of surface combatant that bedeviled the Royal Navy's frigates and light combatants. But it wasn't from French yards, but American ones!
And in the film the point is made that the Acheron too is Yankee built and fitted. Here is the scene for reference. Essentially she is a copy of the 3 original 44 gun "Super Frigates" of the US Navy. Of the original 6 frigates ordered for the USN there were 2 designs prepared by the master shipwright Joshua Humpreys(with help from Quaker Josiah Fox whom he eventually fell out with and who did a poor job altering the designs of the Chesapeake), a more conventional 36 gun design, and a huge 44 gun one. These ships would outgun any other frigate they might meet, but would be faster than a Razee, which was a larger ship of the line which had been cut down. Additionally these ships would be a good deal longer and more narrow than might have been considered, but sturdily built and with a rather unconventional diagonal scantling or ribbing that would help reinforce the hull and prevent warping or hogging of the frame. While they would be built from a very particular wood, Southern Live Oak, when it could be gotten. This is a VERY dense wood, and prized for its naval usages, and many a slave and worker suffered in the swamps of Georgia and the Carolina's to find sufficient timber.
And of the 6, one of the 44's, USS Constitution was selected to be built in Boston, first putting to sea in 1798. The 44's had a heavier broadside in both cannon size and number, a longer range, and sturdier hull than the commonly encountered British frigates. They also had on some of the ships excellent sailing qualities. Their string of victories in 1812(44's fought 3 duels to open the war against smaller single British Frigates and won all 3) caused the Admiralty to forbid British frigate captains from engaging one on one with American frigates. This was ignored when HMS Shannon tangled with USS Chesapeake off Boston where her history as a ill fated ship continued and she was taken as a prize by the Royal Navy.
So the knowledge and ability to build one of these fine ships existed in Boston, but so far only at the Navy Yard, and they of course were not taking orders. However in addition to the Original 6, states and cities also funded new construction either in Navy Yards or Private Ship Builders. Among these were the New York of 36 guns from NYC, from Charleston the John Adams of 30 guns, and from Salem Mass the 36 gun USS Essex. So it was not unheard of for sub national or even local entities to engage in ordering a warship, and of course purpose built privateers were far from unheard of.
So while Acheron would be a VERY unique case, especially considering the Quasi-War, it would have been one of just a series of frigates ordered in the US not by the federal govt, though absolutely the biggest as a derivative design of the 44's.
If you are interested in more of the designs and how they did a GREAT intro book is 6 Frigates: The founding fo the US Navy by Ian W. Toll. It charts the debates over the form and size of the Navy through the Quasi-War, against the Barbary Pirates, and Britain for round 2. As noted below the book variation places it during 1812 and against a Yankee 44 making it all much simpler.
Hi there -- while u/QuickSpore and u/DBHT14 have covered pretty well the technical aspects of the movie (that is, that it transformed O'Brian's American warship into a fictitious French one) I'd like to try to comment a bit about ship construction in the British navy vs. others at the time and how it differed. I wrote about this before in a couple pretty long comments in this thread:
And also wrote about frigate construction more specifically here (Surprise and Norfolk/Acheron were both nominally frigates, but differently armed and manned):
https://www.reddit.com/r/AskHistorians/comments/2709jm/how_would_a_britishhms_frigate_built_in_1715/
To briefly summarize both those answers, what's interesting about this time period (say 1680-1830 or so) is that the English/British tended to build ships differently from other nations they were at war with, and for a variety of reasons. The French led the way at the time in what we might call a "scientific" understanding of sailing that was driven by university studies; English/British ships tended to be built on more empirical grounds. One way to look at it is that the French were theorizing about stability while the British were over on the other side of the Channel putting steering wheels on ships, an innovation it took the French close to 40 years to copy. To quote myself from that first answer:
At this point, then, it's worth pausing and considering what was happening in the world of ship design in Europe. The large French ships, at least nominally, were being built to a plan dictated from Versailles, although individual yards could and did make modifications particularly to hull shapes that could change a ship's seaworthiness. But the French designs were being dictated from academic studies (the French were the first to conceptualize of a metacenter of a ship, and to theorize about metacentric height) and they were not built well. French ships were lightly built, fastened with nails instead of treenails, and their designers favored very long hulls and taunt (very high) masts, meaning their ships would be very fast off the wind. But their performance suffered greatly close-hauled (that is, beating into the wind) and in any kind of a sea state. They were designed with light timbers to be buoyant, and carry guns high, but light timbers suffered greatly under normal hogging and sagging strains. Their theories also led them to believe that the working of a ship helped it to move faster, rather than simply causing great strain on a ship's inward parts; all these things meant that French ships had high building costs and maintenance costs and short lives, and dockyard constructors knew they were building poor ships. (I should mention, in fairness to the French, that they had natural interests in the Mediterranean that the British did not until after the capture of Gibraltar; their ships performed excellently in that odd tideless sea.) In contrast to this, British designs were by midcentury and later being voted on in the broad sense, but it was up to individual yards and shipwrights to build to specifications. British ships tended to be shorter than comparable French designs, but they were more heavily timbered; their weight helped them perform well going to windward and in heavy weather; and they had full hull forms that could be stored for long voyages, either spending time on blockade or long periods of time overseas. They were meant to be inexpensive to build and maintain, in a navy that knew that they would have a difficult time keeping pace simply out of their own building in matching their needs.
In any case, in practical terms, the French designs didn't actually tend to be faster than the British; given the technical constraints at the time, speed can't be accounted before merely by construction. The main limiting factors seem to be the cleanliness of ships' bottoms (which docking and coppering, both British advantages, contribute to) and the ship's trim, rig and the skillfulness of the crew. British ships often outsailed French ships in conditions that should have favored the French. (To briefly break the 20-year-rule, skill at sailing even today makes the difference in races between boats built to be identical.) Moreover, ships captured by the British tended to be faster after re-rigging, re-stowing of holds and re-hanging of decks, suggesting that there was technical knowledge in the shipyards' hands that was not there for the French.
I would be remiss here also not to mention the American navy, which largely adopted British shipbuilding practices (because in practice their yards and their methods had been British for a century or so before the Brits lost the colonies). The nascent American navy, famously, built six frigates to be (oversimplifying here) the equivalent of battlecruisers, heavier than any British frigate but able to run away from any British ship of the line. There were supposed to be two classes of frigate, three in each class, but idiosyncrasies among the shipyards meant that they had wildly different performance