The first extant treatise on shipbuilding was written ca. 1436 by MICHAEL of RHODES, a man who began his career as an oarsman on a Venetian galley in 1401 and worked his way up into officer positions. He wrote and illustrated a book that contains a treatise on ship building, a treatise on mathematics, much material on astrology, and other materials. His treatise on shipbuilding treats three kinds of galleys and two kinds of round ships.
Shipwrights in the South adopted, then adapted, a Northern European kind of ship known as a cog. The cog was much larger than southern shipwrights were used to building. It had a flat floor and wide beam that provided plenty a large cargo space and very high sides that made it easier to defend. A cog was normally equipped with a stern rudder and carried a square sail on a single mast. Its hull was clinker-built, meaning that planks on the outside overlapped each other in much the same way one can still see on an old wooden rowboat. Most of the strength of the hull in clinker-built ships resided in the shell created by the planking. Internal frames were used to reinforce the planks rather than provide a structural foundation. Scholars refer to this kind of ship as "shell-built." When Mediterranean shipbuilders began to build cogs in greater numbers after 1300, they borrowed the cog's large dimensions and the stern rudder, abandoning the steering oar. But they applied their own construction techniques. In particular, they used the Southern European "frame-built" technique. Using this method of construction, the strength of a ship's hull is provided by its internal skeleton, and the planks are basically used to make the framework watertight. During construction, the frame was erected first and then planked over, but the planks were placed edge to edge and did not overlap. This edge-planking technique came to be called "carvel." This word would soon evolve into "caravel," the name given to the Spanish and Portuguese ships that led the way in the Age of Discovery. New and different sail plans came into use on different kinds of ships.
Michael's treatise on shipbuilding reflects two approaches to these problems. For the types of ships built in private shipyards, he describes a system based on a proportional approach; for the galleys built in the state-run Arsenal, his approach reflects the recording of actual measurements on paper. Describing his nave latina, Michael quickly gives a series of dimensions for parts of the hull. First he gives the length of the keel. Next he gives measurements for the midship frameand the height of the deck. Then he gives the overall length of the ship on the deck. The first step in construction was to lay the keel on a series of posts driven into the ground. The keel was a long, thick timber that provided the foundation for the entire ship's structure.The next step was to raise the stem and sternposts. These were two thick timbers defining the curve of the bow and stern. They were scarfed, or joined, to either end of the keel.Then place the midship frame,taiframes and so on. On both fronts, Mediterranean developments during the 14th and 15th centuries outran those of Northern Europe. As a result, although Michael's sailing ships might seem somewhat ordinary to us, and even a little dull compared to his galleys, they would have been seen as examples of the very latest technology to many mariners and shipwrights from the Atlantic.
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Source: http://brunelleschi.imss.fi.it/michaelo ... iling.html
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