Fig 6.2 Pressure distribution around a wing section
Most of the wing sections of interest in sailing yacht design are symmetric, as in Fig 6.1, since they have to work equally well on both tacks. At zero angle of attack the pressure distribution along the section looks in principle like the one along a waterline (see Fig 5.9), ie there is high pressure at the nose and tail, and lower pressure in between. However, at non-zero angle of attack (as in Fig 6.1), the flow becomes highly asymmetric. In particular, there is a large difference between the flow that has to move from the stagnation point past the nose on to the upper side and the one moving backwards from the stagnation point. While the former flow passes a region of very large curvature, the latter moves more or less straight back. There is also a difference in speed between the two sides, the upper speed being higher than the undisturbed one, and the lower speed slower. Quite different pressures are then created as shown in Fig 6.2, and it is particularly noteworthy that there is a large suction peak at the nose. Further back on the top side the suction is gradually reduced. On the lower side the pressure is positive, but its absolute value is lower than on the other side. If all the pressure forces on the section are added, a resulting force (shown as an arrow) is obtained. The angle between the undisturbed flow and the resulting force depends on the efficiency of the wing. For a two-dimensional case without friction the angle would be 90°. In a real situation it is always smaller than 90° (pointing more backwards). The designer's task is to make the angle as close to 90° as
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Lets start by identifying what exactly certain boats are. Sometimes the terminology can get lost on beginners, so well look at some of the most common boats and what theyre called. These boats are exactly what the name implies. They are meant to be used for fishing. Most fishing boats are powered by outboard motors, and many also have a trolling motor mounted on the bow. Bass boats can be made of aluminium or fibreglass.