There certainly were large ships, such as the fine one sailing up the Bosporus that reportedly incensed the Byzantine emperor Theophilos (d. 842) when he learned that its owner was his wife Theodora, or the three-masted “pirate” naus. Threemasted sailing ships certainly existed in the eleventh century, as is proved by a depiction on glazed Pisan bacini, which were glazed pottery bowls from the Muslim world placed on the facades of churches at Pisa and elsewhere to reflect sunlight and give the churches a glittering aspect. However, such large ships have left no trace in the documentary record before the thirteenth century.
The twelfth and thirteenth centuries saw no innovation in the technology or construction of Mediterranean sailing naves; however, the length and beam, number of masts, and number of decks and depth in hold of some increased dramatically. By the mid–twelfth century, iconography depicted as a matter of course two-masted naves with multiple-tiered sterncastles and substantial forecastles, such as the Genoese ship conveying Conrad of Montferrat to the Holy Land in the Paris manuscript of the Annals of Genoa
[MS Paris, Bibliothèque nationale de France, suppl.lat.773]. By the thirteenth century, the mosaics of San Marco in Venice also showed three-masted ships. No documentary evidence for threemasted ships survives; however, it is available for twomasted ships provided by Genoa and Venice in 1246–1269 for the two crusades of Louis IX of France.
Quelle: John Pryor: "Ships" in: The Crusades. An Encyclopedia, 2006