Every summer during the arrival in port, the helmsman husbands, wives send the poor to take the mooring line, for a strange reason these do not help the boat hook, and put their hand in the water to pick up the mooring line. Husbands, forgetting the presence of his wife, but being very careful to not hit the stern of the boat against the dock of the port, give throttle. The propeller starts to spin, and alas, the grim hand of the woman makes a bad end. As you can see in this post will discuss the propeller, of course, this preface is a bit 'novel, but unfortunately stories of hands cut off by the propeller, have happened. So watch the prop!
Apart from being the cause of many wives of severed hands the propeller is also the driving device, which acts by pushing back the water which runs to the hull and sending the corresponding reaction thrust forward.
technical information:
Step: The path of the propeller in a 360 ° turn six is \u200b\u200bscrewed into a solid body. Is determined by the inclination and the size of the blades (the first illustration of the photo at right); Redress: the difference between the theoretical wheelbase (quoted previously) and the actual pitch (what happens in water). Example shown in the second photo image side;
propellant surface: the surface of the blades projected onto a plane perpendicular to the axis of rotation;
Diameter: The diameter of the circle described by the propeller itself;
Speed : is the product of the pitch by the number of laps.
Cavitation :
phenomenon that occurs when the pitch is suitable for the type of boat is so Formas, near the rotating blades, a god area vacuum and air emulsified. This includes: creation of vortices, with poor performance of the propeller, an uncontrolled increase in speed and corrosion. To see if our
helix does not exhibit this phenomenon, we need to see exactly if it is oxidized or not. In fact, during cavitation is formed like a bubble of air that corrodes the blades. So when we are at anchor, or at anchor would be useful to check the condition of our propeller, the engine is off course;)!
Cavitation is a phenomenon that can be created even while browsing, taking. For example, bad wave. The engine will rev up, a phenomenon easy to perceive, we will see in the water at our bow, the air bubbles, and decrease the speed of our boat because the propeller is no longer acting as an organ of propulsion. The simple thing to do is decrease the number of laps to make sure that our propeller starts to work again.
This phenomenon is most visible with the motor boats, speedboats and so forth, when they occur so-called gliding, because, for us sailors, the real place where we sail planing, because the engine of a sailboat is not as powerful .
The sea and wind, the variations are continuous and there is no bottom to the world that can adapt well to all these situations you may encounter endless browsing. However, just as in the car just shift up to make a curve a little better dry, so a strike at sea flap may lead to a more comfortable and safe navigation. You
sea bow? Surely your boat, if only row 20 knots, will tend to jump like a wild mustang on every wave, raising his head to the sky and then falling heavily the next wave. Lower both of your flap and you will see that the boat will again be a docile friend who sfonderà waves without trying to become an interplanetary rocket, and your back will thank you. ;)
Bow RH and LH:
addition to its propulsion, the propeller also produces side effects, the more pronounced when lower the speed of propulsion, so you must know the characteristics of its propeller and take them into account, especially during operation (eg, mooring, berthing at the quay, anchor), moments in which ' propeller effect is greater than that of the rudder.
propeller clockwise : view from the stern, the blades rotate clockwise.
Bow Left: view from the stern, the blades rotate counter-clockwise.
Both examples are done in terms of forward movement. The bow will rotate in the opposite direction (see esmpio shown in photo).
Good wind at all!
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