The Pirates of the Caribbean is set around the mid 1700's. The Black Pearl's gun load was/is 32 cannon. Now, the Pearl originally started out as a merchant ship, and the ship's design was based on that of the Galleon with some features of an East Indiaman. Galleons were large and expensive vessels for the time, and the first of them were built around mid 1500's, and the ship type continued to be built well into the 1800's. The fastest usually did not exceed 10 knots. There were some very famous Galleons - the Golden Hind (22 guns) was one of these, and an interesting replica of the Hind can be seen docked in London, England. At some point the Pearl was converted to a pirate vessel. The lack of cargo and the additional sails would mean she would be faster than your average laden merchantman of the time. Possibly as fast as some of the English warships also depicted in the movie. The fictional (& supernatural ) speed of the Pearl would obviously not be reflected in real life. Now a converted merchantman is one thing, however by the mid 18th Century - and in real life - the Navy's of the world had moved on and were using a number of dedicated naval designs. For speed, probably the most popular would be the Frigate - a fine example of a frigate would be the USS Constitution (1797), and capable of 14 knots on a good day. So, if one were looking for an example of a fast Frigate easily capable of matching or exceeding the realistic speed of the Pearl, then that might be HMS Endymion (1797), a 40 gun ship, again capable of 14 knots, the design of which was copied and modified from a captured French Frigate - the Pomone. As a slightly different example, the Cutty Sark, a famous clipper ship, was recorded as being able to achieve 17 knots. Hope all this helps?