Ship’s courses relative to the wind
The heading of the vessel relative to the wind is the angle between the direction of the wind and the diametrical plane of the vessel, that is, the heading angle to the horizon point, from where the wind blows, expressed in angular degrees or rumbas.
Depending on the magnitude of this angle, the courses relative to the wind have their own names:1 – steep badewind (30 ° – 45 °);
2 – full badewind (45 ° – 75 °);
3 – halfwind (about 90 °);
4 – Bakstag (110 ° – 160 °);
5 – fordevind (160 ° – 200 °);
6 – leventik (30 ° on each side)
Leventik (fr. Le vent) – a course that forms an angle close to 180 degrees with the direction of the wind, that is, the wind blows almost exactly from the front in relation to the ship. Since the sailing ship cannot go on such a course, they usually do not say “course”, but “leventik position”.
Beydevind (Dutch bij de wind) – a course at which the angle between the direction of the wind and the direction of movement of the vessel is more than 100 degrees (less than 8 points). Allocate a full-range badewind (from 100 to 120 degrees) and a steep one (over 120 degrees). The thrust of the sail is entirely determined by its lift, with an increase in drag, the thrust decreases, but the drift force increases. Thus, in this course, a sail installed with a minimum angle of attack to the pennant wind (5-10 °) works as an aerodynamic wing.
The best sailing vessels sail at an angle of 30-35 ° to the direction of the true wind. Due to the addition of the vectors of wind speed and oncoming air flow, the speed of the pennant wind on the badewind course is maximum, as well as the aerodynamic force on the sail, proportional to the square of the wind speed. The maximum value reaches and the power of drift. If you try to go at a sharper angle to the wind, then the speed of the vessel will decrease, the sail will rinse, the aerodynamic force will decrease and, finally, there will come a moment when the drag of the sail and the resistance of the water to the movement of the boat will far exceed the thrust. The ship will reverse.
Gulfwind (Dutch halve wind), or half-wind – the course at which the angle between the direction of the wind and the direction of movement of the vessel is approx. 8 points (from 80 to 100 degrees). In this course, the wind blows perpendicular to the DP, and the pennant wind is directed from the nose at an acute angle to the DP. Accordingly, the sail is set at a lower angle of attack, its thrust is equal to the lifting force, and the drift force is the drag of the sail. in this course, the sail should divide the angle between the windbreak and the direction of the pennant wind in about half.
Bakstag (Dutch bakstag) – a course that forms an angle with the direction of the wind greater than 8, but less than 16 points (more than ten and less than eighty degrees), that is, the wind blows from the side to the side of the ship; the course is distinguished by a full backstop at which the angle is not more than twenty degrees, that is, approaching a fordewind; the sail is set at an angle to the wind from the leeward. Usually on this course, a sailing ship develops the highest speed. At the backstage, the sail works with a large angle of attack, at which the drag plays a major role in creating the thrust of the sail. The strength of the drift is practically absent.
Vordewind (Dutch voor de wind) – a course in which the wind is directed into the stern of the ship.
Vordewind is the same “tailwind” that sailors desire, although sailing is not the fastest course, as you would expect. In addition, it requires steering attention and mastery of the art of controlling additional sails (usually a spinnaker). The sail is placed perpendicular to the direction of the wind, the thrust on it is created due to frontal resistance. A weak wind on this course is practically not felt, since the speed of the pennant wind is equal to the difference between the true wind speed and the speed of the oncoming air flow.
Vordewind – one of two turns (turn – tack change) of a sailing vessel, in which the direction of the wind at the moment of turn passes through the stern. In contrast to the “overshoot” turn, the turn of the fordewind is more complex and, at times, dangerous, requires clear command actions when working with sails. It is no coincidence that the team serves with the clarification: “Get ready for the turn of the fordewind!”, While when turning the “overstag” the commander simply commands “Get ready for the turn!”.