Outline of VL-Vec Twin System
Improvement in rudder performance has come to be an important element for very large blocky ships such as VLCCs, in which importance is attached to maneuverability. It can be considered to increase rudder area in order to cope with this question, but in case of a single rudder arrangement, an increase in rudder area would not be so effective for vital necessity of improving maneuverability when a ship navigates at low speed, make rudder construction heavy, affect propulsive performance, and as the case may be, require extension of hull dimension. In addition, it makes steering gear capacity too large.
With this for a background, a new system developed is so composed that twin high lift Schilling Rudders are arranged behind a single screw propeller, respective rudder being provided with a reaction fin, and a propeller boss cap being provided with fins. Despite of less total rudder area, a VL-Vec Twin Rudder System attains remarkable improvement in safety and maneuverability for very large blocky vessels, with propulsive performance equal to, or higher than that of a single rudder arrangement, along with inherent good course-keeping quality.
Outline of System.
A New VecTwin Rudder System is a rudder system, in which a pair of Fish Tail Rudders respectively having special sectional profile is arranged symmetrically behind a single fixed pitch propeller, and enables a ship to be maneuvered in any mode of not only forwarding and turning port or starboard, but also going astern with steerability, hovering, extremely slow speed navigation, emergency stopping and head or stern gyrating by means of combining rudder angle positions of the respective rudders, with the propeller being kept rotating in the forward direction.
Such rudder angle combination control is conducted by a single Joystick lever, and a propeller slip stream is directed by the rudders so as to generate thrust in any direction.
By virtue of such arrangement that VecTwin Rudders are arranged so as to enclose a propeller slip stream, which brings less propeller thrust fluctuation by wave and excellent course stability of a ship when going straight ahead, a New VecTwin System makes a horsepower loss and ship speed reduction, which are caused by seaway condition, small. It is appraised that a ship equipped with a New VecTwin System shows less yawing especially when navigating in a condition of following wave, which means safe operation.
This is a system that brings excellent economical effect from the synthetic viewpoint, as a ship equipped with a New VecTwin System can be maneuvered easily and in short time in a harbor and for approaching to and departing from a pier, and mental and physical stress imposed on crew is lightened.
The New VecTwin Rudder System bases on manual operation, but it can be connected, if requested, to various automated systems including dynamic positioning.
Special Features of System.
Excellent maneuverability of a New VecTwin Rudder System is given by Joystick control.
It is worthy of special mention that it has function of hovering, in which a ship can be brought to nearly a standstill, with a propeller being kept rotating in the forward direction, and in the meantime, ship’s heading angle little undergoes a change. In the hovering condition, postural control of a ship can be conducted, without going ahead or astern, by means of tilting a Joystick control lever right or left.
With a propeller running ahead with constant revolution, ship speed can be adjusted freely at will, and furthermore, even in the condition that a ship navigates at low speed or is brought to a standstill, good steerability is secured. A ship can be maneuvered at will extending over whole sphere from going ahead to going astern.
As a New VecTwin Rudder System generates thrust at a ship stern in any direction, a ship can easily be brought to such conditions as crabbing, diagonally moving and turning in situ, with bow thruster operation being combined. In case of a small ship, even if a bow thruster is not equipped, excellent maneuvering function of a New VecTwin Rudder System makes it possible for a ship to be easily maneuvered.
An emergency switch is newly provided in a central Joystick maneuvering console for further improving safety of a ship at sea. An emergency stop of a ship is performed by pushing this switch button simply. In this case, stopping distance will be reduced to about a half of that of a conventional ship.
Even while such emergency stopping is in operation, the Joystick control can be applied for immediately bringing the ship to a maneuvering condition that fully utilizes specific characters of the VecTwin Rudder System. This will greatly contribute to avoidance from danger, and builds up a highly safe ship.
Constitution of System.
A maneuvering system is so constituted that VecTwin Rudders are operated by Joystick through a controller, a servo-amplifier provided in a steering stand, hydraulic pump units and rotary vane steering gears.
New type Joystick can incorporate CRT (cathode-ray tube) display capable of displaying thrust vector, and a small rudder angle indicator, as requested (option).
A hovering position indicating lamp is newly provided so that the hovering position (datum rudder angle) can be easily confirmed by the lamp and buzzer.
A rudder angle indicator provided in a wheel house is designed so as to be easily visible in the nighttime.
A controller is of high accuracy and noise-proof as signals are treated digitally.
Rotary vane type steering gears are employed, which are smaller and lighter than ram-cylinder type steering gears.
Operable rudder angle range of VecTwin Rudders is 105o toward outboard and 25o toward inboard.
Rudder angle combination of VecTwin Rudders that is characteristic of this system is automatically achieved by Joystick.
1. Joystick with CRT Display for Displaying Thrust Vector.
New type Joystick with CRT display displaying thrust vector has been developed. This CRT display displays thrust vector toward all directions that is characteristically generated by rudder angle combination of the VecTwin Rudders.
On the screen, both Joystick order and rudder movement (magnitude and direction of resultant thrust generated by rudder angle combination) are displayed, and hence ship maneuver can be done firmly and easily.
The higher propeller revolution is, the larger the resultant thrust becomes.
2. Joystick with Small Rudder Angle Indicator.
The small rudder angle indicator is designed so as to be easily visible in the nighttime.
The Joystick body is of water-proof construction, and can be used even outdoors.