For sailing vessels commonly found during the age of Sword & Sorcery pulp fiction adventures I have turned to Elric!'s Sailing on the Seas of Fate supplement from Chaosium for basic seafaring statistics.
There is a nice spread of different types of sailing vessels to be found in its pages; from simple canoe to two-masted brigs and war galleys. It also provides a nice guide of terminology you will find when describing characteristics of sailing vessels.
Having a ready made terminology for adjudicating sea adventures I find immensely useful when I'm trying to provide a nautical setting, and Chaosium does provide enough of this bedrock information.
The book is also useful for providing basic answers to everyday mechanical questions one would encounter plying your fantasy seas regardless of the game system to be used. The most important of these being movement speeds.
One topic the book does not cover are costs of purchasing and maintaining a sailing vessel ins a fantasy world. A sailing vessel naturally occurs as a likely resource sink for adventurers who have looted their fair share of moldering crypts. That and land holdings, estates would likely come up as possible uses for the PC's ill-gotten gains. Mercenary forces too. With enough gold any barbarian dog can put together a band of desperate sell swords, but how much gold is that really? How do you come up with a sensible economic scale for these above mentioned enterprises?
I'm not saying the Elric! supplement should have addressed all these topics, but if you have costs on ships and what it takes in men and material to maintain them on a monthly basis you should be able to extrapolate out all these other concerns for your campaign world.
In the spirit of the USR rules set I have had to approach the Chaosium BRP system with an eye towards stripping game elements and mechanics to a minimum. Seaworthiness, Hull Quality, Structure Points, these all become your USR Hits, Armor, Stats... Specialisms can be used to detail characteristics to differentiate say a war ship from a merchant cog. For example;
The Moebius; a Ghazorian merchant cog, 15 crew members.
Hull Quality: 4 Length: 70' Beam: 18' Draft: 7'
The Sailing on the Seas of Fate descriptions and uses of the few game statistics for the boat are easily understood, and can be taken out and used on their own in most fantasy settings. The Sailing on the Seas of Fate ship record sheet provides a great compass heading for "stat'ing" up a sailing vessel in USR game terms and can be adequately shoehorned into USR's simple format.
From my experience with D&D, Champions, GURPS, BRP, etc. vehicles in general become overly complex character sheets and their utility gets buried under the time heavy bookkeeping and cost calculating. For both the player and the GM. And vehicles in a campaign world, at some level become a commodity and therefore must be able to generated in large numbers.Through USR I am trying to reduce the paperwork so everyone can spend more time courting adventurous death. Unless your players want a crunchy sea battle. I think these rules can be used with battle maps and detailed turn sequences if everyone wants to game out a tactical simulation.
I found Zach S.'s Wavecrawl Kit a useful tool as well for random encounters at sea. Combined with the Sailing on the Seas of Fate event tables I have plenty of material to game out fantastic Sword & Sorcery sailing adventures. If the supplementary rules I'm hacking into my Sword & Sorcery game are lacking in any area I would say I don't have rules for flying creatures and vehicles. At some point I will search the web for useful rules to hack and add them in.