Wind influence. The influence of the interaction of the starboard rudder propeller on the behavior of the vessel Maneuvering the vessel at the command “man overboard”

Position of the vessel relative to the water	Steering wheel position	Propeller operating mode	Screw operating direction	Result
1.Motionless	Directly	Only included	Forward	The bow will roll to the left (the stern will be thrown to the right)
2.Moves forward	Right	Steady	Forward	The bow is thrown to the right (the stern is thrown to the left)
3.Moves forward	Straight or left	Steady	Forward	The bow of the ship will roll towards the rudder deflection
4.Motionless	Directly	Only included	Back	The stern is thrown to the left. The nose will roll to the right
5.Moves backwards	Left or right	Steady	Back	Individually for each vessel. Usually the stern goes towards the shifted rudder
6.Moves forward	Directly	Only included	Back	The bow of the ship will roll to the right, the stern to the left

A left-hand rotation screw, other conditions being equal, will give results opposite to those shown in the table.

If a right-handed propeller is installed on the vessel, the vessel will turn better to the right; the circulation diameter to the right will be smaller than to the left. When going astern, the ship's maneuverability is usually worse. A ship with a right-handed propeller in reverse turns better to turn its stern to the left than to the right. Therefore, when moving forward on a ship with a starboard propeller, they tend to approach the berth with the left side, since in this case, with a change of speed to the rear, the stern will be pressed against the wall.

Some motor yachts and boats are equipped with two motors, each with its own shaft and propeller. In this case, the screws usually rotate in different directions. They can be installed either with outward rotation, that is, in the upper part the blades go from the middle to the side, or with inward rotation, when the blades in the upper part go from the side to the middle. This or that direction of rotation of the screws, as well as the inclination of the axes of the screws and shafts to the horizontal and diametrical planes, are of great importance in relation to agility.

Wind influence

Each vessel is exposed to wind to varying degrees. Depending on the direction and strength of the wind, the control of the ship and its maneuverability change. Often, not only small, but also large ships cannot withstand the wind either with the rudder or the operation of the propeller, it cannot stay at anchor, approach the pier or move away from it. As the strength and direction of the wind changes, the path and speed of the ship changes. The effect of wind on a ship depends on its strength and direction, on the total area of the underwater part, on the windage of the ship, its draft and displacement.

Rice. 104. The vessel's yaw and yaw rate: A- arrogance; b - yaw rate

The side of the ship facing the wind is called windward, and the side opposite it is called leeward. The wind blowing in the stern is called a tail wind, and the wind blowing in the bow is called a head, opposite or head wind. During mooring operations, the wind blowing towards the berth is called bulk, or pressure, and the wind in the opposite direction (from the berth wall) is called dump, or push.

The wind, with a constant direction in the river valley, will change direction relative to the ship following the bends of this river. When the vessel moves near the mouths of rivers and rivers, past ravines and gullies, especially past high banks, a strong squall wind may blow, varying in direction. The wind reflected from high quay walls, from a high shore, can sharply change its direction, swirl, change in strength, and sometimes stop completely. This is often felt when entering the lock chamber from the tailwater.

A squall, i.e. the sudden appearance of a strong wind or a sharp change in its direction or strength, is dangerous for small ships. A squall with frequent changes in wind direction and speed compared to the previously operating wind is especially dangerous. The effect of a squall is strongest at the beginning and especially after a calm.

Spray carried by the wind interferes with the control of small boats. They end up on maps, instruments, and flood the windshield. The wind complicates the vessel's approach to the berth, locking and other operations.

The sail area of a ship is determined by the total area of the freeboard of the hull, superstructures and devices that provide wind resistance. The point of application of the resultant of all wind forces is called the center of windage. A side wind pushes a ship away from the direction given by its course, i.e., it creates ship drift. Drift decreases with increasing ship speed; The smaller the vessel's draft, the smaller it is.

The relative position of the center of gravity and the center of sail determines the properties of the vessel, which are called yaw or yaw. A ship whose center of sail is located forward of the center of gravity is characterized by evasion or the desire to evade the wind. Yaw or the tendency to go towards the wind are characteristic of ships whose center of sail is located aft of the center of gravity (Fig. 104). Consequently, these properties of the ship can be adjusted by moving cargo or passengers on the ship forward or aft. To keep the ship on course when it is swaying, you have to shift the rudder to the wind, and when yawing - to the wind. In both cases, the rudder is not in the center plane of the vessel and creates additional resistance, which reduces the speed. However, a yaw vessel behaves better than a limp one in stormy conditions, when the position of the vessel with its bow to the wave is safer than along the wave or side to it.

1. Propeller influence

The control of a ship largely depends not only on the rudder, but also on the design of the propeller, its speed of rotation and the contours of the stern of the ship.

Propellers are made of cast iron, steel and bronze. The best propellers for boats should be considered bronze propellers, as they are lightweight, easy to polish, and resistant to corrosion in water. Screws are characterized by diameter, pitch and efficiency.

The diameter of the propeller is the diameter of the circle described by the extreme points of the blades.

The pitch of the screw is the distance along the axis of the screw that any point on the screw moves in one full revolution.

Rice. 103.

The efficiency coefficient (efficiency) of a propeller is determined by the ratio of the power developed by the propeller to the power expended on its rotation.

The operation of a propeller is based on hydrodynamic force created by vacuum on one surface and pressure on the other surface of the blade.

Modern ship propulsors are still very imperfect. Thus, propellers, on average, spend about half of the power given to them by the engine uselessly, for example, on screw-like twisting of water particles in the jet.

On boats, two-, three-, and less often four-blade propellers are used. On fishing boats, propellers with rotating blades or so-called adjustable pitch propellers are sometimes installed, which allow you to smoothly change the speed or direction of the vessel with constant one-way rotation of the propeller shaft. This eliminates the need to reverse the engine.

Screws differ in the direction of their rotation. A propeller rotating clockwise (when viewed from the stern to the bow) is called a right-hand rotation propeller, counterclockwise is called a left-hand rotation screw. When moving forward under the stern valance of the ship's hull in front and behind the rudder, a passing water flow (Fig. 103) is formed and forces arise that act on the rudder and affect the maneuverability of the vessel. The speed of the passing flow is greater, the fuller and blunter the contours of the stern.

The vacuum on the convex side of the blade, called the suction side, draws water toward the propeller, and the pressure on the flat side, called the discharge side, pushes water away from the propeller. The speed of the jet being thrown out is approximately twice that of the jet being sucked in. The reaction of the thrown water is perceived by the blades, which transmit it to the ship through the hub and propeller shaft. This force that sets the ship in motion is called thrust.

In a stream of water thrown by a propeller, particles do not move in a straight line, but in a helical manner. The passing flow seems to be pulled behind the ship and its size depends on the shape of the stern part of the boat. The flow slightly changes the pressure on the rudder, which is moved away from the center plane of the vessel.

The combined effect of all flows has a noticeable effect on the controllability of the vessel; it depends on the position of the steering wheel, the magnitude and change in speed, the shape of the hull, the design and operating mode of the propeller. Therefore, each vessel has its own individual characteristics of the action of the propeller on the rudder, which the navigator must carefully study in practice (Table 4).

Table 4

INFLUENCE OF INTERACTION OF THE RIGHT RUDDER PROPELLER ON THE BEHAVIOR OF THE VESSEL

Position of the vessel relative to the water	Position	Propeller operating mode	Screw operating direction	Result
1.Motionless		Only included		The bow will roll to the left (the stern will be thrown to the right)
2.Moves forward		Steady		The bow is thrown to the right (the stern is thrown to the left)
3.Moves forward	Straight or left	Steady		The bow of the ship will roll towards the rudder deflection
4.Motionless		Only included		The stern is thrown to the left. The nose will roll to the right
5.Moves backwards	or right	Steady		Individually for each vessel. Usually the stern goes towards the shifted rudder
6.Moves forward		Only included		The bow of the ship will roll to the right, the stern to the left

A left-hand rotation screw, other conditions being equal, will give results opposite to those shown in the table.

2. Wind influence

Rice. 104.A- arrogance; b - yaw rate

3. Effect of roll and trim

Roll is the transverse inclination of the ship on one of the sides. Trim is the longitudinal inclination of the ship to the bow or stern.

Roll and trim can be formed as a result of the movement of people, cargo, pitching, and turning. Crepe angles can reach dangerously critical angles, especially if there is water in the boat and its overflow. The movement of water towards the slightest inclination of a small vessel contributes to the formation of an even greater roll and trim and can lead to the capsizing of the vessel.

In order to prevent the boat from turning over due to the overflow of water that has entered it, it must be drained.

When heeling, the pressure from the side of the heeled side is greater and the ship tends to evade towards the higher side. Therefore, to keep the ship on course, you have to shift the rudder towards the heeled side, which increases the drag force and accordingly reduces the speed.

When making sharp turns at high speed, the roll is especially high. The draft from the roll increases.

When trimming to the bow, the ship's heading stability deteriorates, yaw increases, and speed decreases. With a large trim to the stern, the ship becomes squat, does not hold course well and is very responsive to wind and waves. A slight trim to the stern is considered normal, which usually improves the agility and propulsion of the vessel.

4. The influence of excitement

Waves make swimming difficult, cause rolling, a strong wave complicates the operation of the propeller, which, together with the stern, can periodically become exposed. This lowers the propeller thrust, reduces the speed of the vessel, and reduces the action of the propeller on the rudder blade. At the moment the bow and especially the propeller are exposed, the ship immediately becomes highly exposed to the wind and goes off course; for boats with outboard motors, this occurs even in slight seas. Strong waves can damage the hull, mechanisms, wash people overboard and cause other problems. The propeller coming out of the water has a harmful effect on the engine, as well as on the hull of the vessel. Wave impacts make it difficult to shift the rudder in a timely and quick manner. On a wave, it is more difficult to choose and maintain a given course.

With oncoming waves, if they do not stop the ship, it is somewhat easier to control it than with passing and side waves. With oncoming waves, the ship stays on course better.

In shallow water, waves not only make it difficult to control the vessel, but can cause damage to the bottom of the hull from hitting the bottom or breakage of the rudder and propeller.

5. Influence of current

The current has a great influence on the control and maneuverable elements of the vessel relative to the ground (shores)

When moving against the current, the ship obeys the rudder well, the inertia of the ship decreases and it is easier to stop. It is more difficult to control the rudder when turning the ship in a tailwind, in which the ship obeys the rudder less easily. Consequently, it is more difficult to perform various maneuvers when moving downstream. As the speed of the current increases, the distance required to turn a vessel going downhill increases, since the circulation curve lengthens and distorts when drawn relative to the shore.

The best conditions for controlling the vessel and, in particular, stopping it when moving against the current are used by navigators when approaching the pier and mooring, i.e., a vessel moving with the current approaches the pier or shore after turning below the berth on the opposite course.

Particularly unpleasant are stall currents passing at an angle to the main flow, as they cause a sharp displacement of the vessel from the chosen course (drift off course). A flow (current) acts like a dump current in a relatively calm river, reservoir, lake, or sea, for example, at the confluence of tributaries and rivers, during surge phenomena. The vessel experiences the greatest drift when moving broadside towards the current. The direction and speed of the current can continuously change due to the action of tides, wind, especially in the mouths and on the banks of rivers, as well as behind various capes and islands.

To prevent the ship from being blown off course by the current, you can shift the rudder and steer in the direction of the current. Then the ship will move in the direction of the resultant speed of the current and its own speed. The angle of correction for the current is determined by eye by observing shore and floating signs.

6. The influence of narrowness

In a wide expanse of water, the water displaced by the vessel diverges in all directions as it moves. The influence of the fairway width when steering a vessel is determined by changes in the nature of the flow, wave formation conditions, and the occurrence of additional resistance. Therefore, in narrow spaces there can be many reasons that throw the ship off course and make it difficult to control.

7. Influence of depth and draft of a moving vessel

When a vessel moves from a deep-water channel to shallow water, wave formation increases, resistance increases and speed decreases. In shallow water, at a sufficiently high speed, the ship will trim to the stern, and near the middle of the ship the water level will noticeably drop - a large depression will form, where the supporting force will decrease. Therefore, the vessel can increase its draft compared to the draft in deep water. The greater the vessel's draft, the smaller the gap between the hull and the bottom, and therefore the relatively greater the speed of water flow under the hull. Therefore, while moving in shallow water, the ship will be sucked to the bottom (usually by the stern). This phenomenon is especially common on ships with flat bottoms. The additional draft of the vessel increases with increasing speed and can cause damage to the hull or propellers when passing through shallow water. The increase in draft while moving in shallow water for some types of vessels reaches 0.5 m.

In the event of an unexpected approach to a shallow place, the bow of the vessel may sharply “push off” from it due to the suddenly increased resistance of the water, and also because in front of the bow the water will be forced into the shallow place, pushing the ship to greater depths.

If the ship is moving through shallow water with variable depth, then the correct direction of movement of the ship must be maintained by frequent rotation of the steering wheel. The narrower and shallower the fairway and the faster the ship moves, the faster and more erratically the stern waves will catch up with the ship, acting unevenly on its stern, now on one side, now on the other. At the same time, the water pressure on the rudder blade changes all the time. The described phenomena cause the vessel to yaw, especially when approaching a deep place to a shallow one. This is most dangerous when diverging from oncoming ships, as it can cause the vessel to run aground, damage to the hull, and a collision between ships.

Consequently, in a shallow fairway, the stroke should be reduced in order to reduce the additional draft and yaw of the vessel and thereby ensure greater traffic safety and improve controllability.

2. The influence of wind on the progress of the ship.

Rice. 104. The vessel's yaw and yaw rate: A- arrogance; b - yaw rate

The side of the ship facing the wind is called windward, and the side opposite it is called leeward. The wind blowing in the stern is called a tailwind, and the wind blowing in the bow is called a head, opposite or head wind. During mooring operations, the wind blowing towards the berth is called bulk, or pressure, and the wind in the opposite direction (from the berth wall) is called dump, or push.

The relative position of the center of gravity and the center of sail determines the properties of the vessel, which are called yaw or yaw.

A ship whose center of sail is located forward of the center of gravity is characterized by evasion or the desire to evade the wind.

Yaw or the tendency to go towards the wind are characteristic of ships whose center of sail is located aft of the center of gravity (Fig. 104).

Consequently, these properties of the ship can be adjusted by moving cargo or passengers on the ship forward or aft. To keep the ship on course when it is swaying, you have to shift the rudder to the wind, and when yawing - to the wind. In both cases, the rudder is not in the center plane of the vessel and creates additional resistance, which reduces the speed. However, a yaw vessel behaves better than a limp one in stormy conditions, when the position of the vessel with its bow to the wave is safer than along the wave or side to it.

3. The influence of roll and trim.

Roll is the transverse inclination of the ship on one of the sides.

Trim is the longitudinal inclination of the ship to the bow or stern.

The movement of water towards the slightest inclination of a small vessel contributes to the formation of an even greater roll and trim and can lead to the capsizing of the vessel.

Waves make swimming difficult, cause rolling, a strong wave complicates the operation of the propeller, which, together with the stern, can periodically become exposed. This lowers the propeller thrust, reduces the speed of the vessel, and reduces the action of the propeller on the rudder blade. The moment the bow and especially the propeller are exposed, the ship immediately becomes highly exposed to the wind and goes off course; for boats with outboard motors, this occurs even in slight seas. Strong waves can damage the hull, mechanisms, wash people overboard and cause other problems. The propeller coming out of the water has a harmful effect on the engine, as well as on the hull of the vessel.

Wave impacts make it difficult to shift the rudder in a timely and quick manner. On a wave, it is more difficult to choose and maintain a given course.

With oncoming waves, if they do not stop the ship, it is somewhat easier to control it than with passing and side waves. With oncoming waves, the ship stays on course better.

In shallow water, waves not only make it difficult to control the vessel, but can cause damage to the bottom of the hull from hitting the bottom or breakage of the rudder and propeller.

5. Influence of current.

The current has a great influence on the control and maneuverable elements of the vessel relative to the ground (shores)

The vessel experiences the greatest drift when moving broadside towards the current.

The direction and speed of the current can continuously change due to the action of tides, wind, especially in the mouths and on the banks of rivers, as well as behind various capes and islands.

To prevent the ship from being blown off course by the current, you can shift the rudder and steer in the direction of the current. Then the ship will move in the direction of the resultant speed of the current and its own speed. The correction angle for the current is determined by eye by observing shore and floating signs.

6. The influence of narrowness.

If the ship is moving through shallow water with variable depth, then the correct direction of movement of the ship must be maintained by frequent rotation of the steering wheel.

The narrower and shallower the fairway and the faster the ship moves, the faster and more erratically the stern waves will catch up with the ship, acting unevenly on its stern, now on one side, now on the other. At the same time, the water pressure on the rudder blade changes all the time. The described phenomena cause the vessel to yaw, especially when approaching a deep place to a shallow one.

This is most dangerous when diverging from oncoming ships, as it can cause the vessel to run aground, damage to the hull, and a collision between ships.

Rice. 104. The vessel's yaw and yaw rate: A- arrogance; b - yaw rate

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Wind influence. The influence of the interaction of the starboard rudder propeller on the behavior of the vessel Maneuvering the vessel at the command “man overboard”