Jangada

A Jangada is a traditional fishing boat made of wood used in the northern region of Brazil. Some claim the historical legacy of the jangada dates back to the ancient Greeks and that it was Ulysses' vessel in The Odyssey.

The construction of the jangada incorporates some improvements in neolithic handcraft - better materials were found and the physics of sailing was better observed through experimentation. The details are closely guarded by artisans.

Its triangular sail makes use of some effects of fluid dynamics. Also known as a "latin" (lateen) sail, it allows one to sail against the wind, taking advantage of the pressure difference on the air that rises on its external face (the one that becomes convex for the internal wind pressure) and its internal face (the one that becomes concave, the side where the sailor goes). Some big watercraft also used the Latin sail, but in a limited manner, because its successful use was crucially dependent on the presence of the sailor, who must be aware of the wind movements: the pressure difference is manipulated constantly whilst sailing against the wind. The same principles are used to keep a plane in the air, thanks to its wing geometry.

In the jangada, there is a gracious curve almost parabolic on the upper part of the triangle, and another one more extended and short, below. This asymmetry is due to the manipulation high of the mast, that turns gently - this time using the lever mechanic principle - around its axis.

Its construction depends on the correct use of materials such as fluctuation woods (like the Brazilian balsa, and other rare species), artisan tissues and ropes. The traditional Jangada doesn't have any metallic elements like nails; its structure is completely put together with joints and lashings using ropes made of hand-woven fibers.

The jangada is typically made using 6 wooden logs rafted together in parallel: two in the center (called "meios", or central ones), 2 more on either side of those (called "mimburas", a Tupi word), and 2 on the outside, called "bordos". The 4 most central logs ("meios" and "mimburas") are united using hard wooden pegs, made of stronger wood than the logs. The "bordos" are then bound to the "mimburas" using more wooden pegs, so they can be more elevated.

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Wikipedia