According to the navigator Michael of Rhodes (?-1445), who was in service to the Serenissima between 1401 and 1445, the ships in use during the late Middle Ages were of two types: oared galleys and sailing ships.
Oared galleys were originally warships which over the course of the 14th century came to be adapted for trade even though their form was little suited to such a function. Although they did not accomodate a great volume of cargo, they guaranteed security and reliability in the delivery of merchandise. The large crew they required was able to defend the ship from the incursions of pirates, and propulsion by the force of oars lessened delays caused by absence of wind.
The galley of Flanders was the largest type of these trading galleys. Having to navigate the turbulent waters of the Atlantic during voyages from Venice to as far as London, the galley of Flanders had a very robust hull capable of carrying a larger volume of cargo. The beams of the hull were fixed to the internal ribs of the ship with wooden nails. It was equipped with a rudder at the stern and two lateral rudders, five anchors, and two lifeboats, one large and one small. The galley had stabilizers that would function as oarlocks, a winch for lifting the anchors and other heavy objects, various tipes of ropes and rigging, masts, and booms. There were two masts: the mainmast, in the middle of the ship, and a smaller mizzenmast toward the stern. The booms held huge triangular sails, which could be changed according to the strength of the wind and weather conditions.
The so-called galley of Romania was of smaller dimensions, and was used in particular for voyages to Constantinople and the Black Sea. Still smaller was the “galia sottil” or “light galley”, used almost exclusively for military purposes.
Sailing ships were generally smaller and more round in shape than galleys, and were distinguished according to their sails, whether triangular (“lateen sail”) or square (“square sail”). The lateen sail originated in the Mediterranean, while square-rigged ships, called “cocche”, derived from the high-sided vessels used on the Atlantic coasts of France and northern Europe.