In Lev Grossman's 'The Magician King' ( aka, the Magicians book 2 ) a central feature is the Muntjac. I'm trying to visualize a real-life parallel, and I'm thinking a large schooner maybe? But that doesn't seem enough war-like. Is there something in the old Navies which was a very fast, deep sea ship which could crew about 60 people?
Well the type of ship is limited due to it's size. If I go on size it would have been classed as a sixth rate ship or and unclassified sloop-of-war -
The rating system did not handle vessels smaller than the sixth rate. The remainder were simply "unrated". The larger of the unrated vessels were generally all called sloops, but that nomenclature is quite confusing for unrated vessels, especially when dealing with the finer points of "ship-sloop", "brig-sloop", "sloop-of-war" (which really just meant the same in naval parlance as "sloop") or even "corvette" (the last a French term that the British Navy did not use until the 1840s). Technically the category of "sloop-of-war" included any unrated combatant vessel—in theory, the term even extended to bomb vessels and fire ships. During the Napoleonic Wars, the Royal Navy increased the number of sloops in service by some 400% as it found that it needed vast numbers of these small vessels for escorting convoys (as in any war, the introduction of convoys created a huge need for escort vessels), combating privateers, and themselves taking prizes.
It would have looked like this -
In the 18th and most of the 19th centuries, a sloop-of-war in the Royal Navy was a warship with a single gun deck that carried up to eighteen guns. The rating system covered all vessels with 20 guns and above; thus, the term sloop-of-war actually encompassed all the unrated combat vessels, including the very small gun-brigs and cutters. In technical terms, even the more specialised bomb vessels and fireships were classed as sloops-of-war, and in practice these were actually employed in the sloop role when not carrying out their specialized functions.
It would have had three masts -
A sloop-of-war was quite different from a civilian or mercantile sloop, which was a general term for a single-masted vessel rigged in a way that would today be called a gaff cutter (but usually without the square topsails then carried by cutter-rigged vessels), though some sloops of that type did serve in the 18th century British Royal Navy, particularly on the Great Lakes of North America. In the first half of the 18th century, most naval sloops were two-masted vessels, usually carrying a ketch or a snow rig. A ketch had main and mizzen masts but no foremast, while a snow had a foremast and a main mast but no mizzen. The first three-masted (i.e. "ship rigged") sloops appeared during the 1740s, and from the mid-1750s most new sloops were built with a three-masted (ship) rig.
It would have had square sails and if a ship sloop three masts square rigged -
Brig sloops had two masts, while ship sloops continued to have three (since a brig is a two-masted, square-rigged vessel, and a ship is a square-rigger with three or more masts, though invariably only three in that period).
But if not then never fear it might have been a for of frigate! A Sixth rate ship they were small and only carried 28 guns -
A frigate /ˈfrɪɡᵻt/ is any of several types of warship, the term having been used for ships of various sizes and roles over the last few centuries. In the 17th century, this term was used for any warship built for speed and maneuverability, the description often used being "frigate-built". These could be warships carrying their principal batteries of carriage-mounted guns on a single deck or on two decks (with further smaller carriage-mounted guns usually carried on the forecastle and quarterdeck of the vessel). The term was generally used for ships too small to stand in the line of battle, although early line-of-battle ships were frequently referred to as frigates when they were built for speed. In the 18th century, the term referred to ships that were usually as long as a ship of the line and were square-rigged on all three masts (full rigged), but were faster and with lighter armament, used for patrolling and escort. In the definition adopted by the British Admiralty, they were rated ships of at least 28 guns, carrying their principal armaments upon a single continuous deck — the upper deck — while ships of the line possessed two or more continuous decks bearing batteries of guns.
it would have looked like this -