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.
● A Super VecTwin System is one that new concepts are applied to a VecTwin Rudder System, such as fitting of reaction fins, improvement in rudder form and rudder layout, etc., based on technical knowledge obtained from the actual results of the VecTwin Rudder Systems that they have been installed on board about 50 vessels, and as a result of technical development made thereafter. Thus we have come to succeed in improving a VecTwin Rudder System so that it can heighten propulsive efficiency while keeping its inherent high maneuvering performance.
● A Super VecTwin System is one that, with a pair of Fish Tail Rudders being symmetrically arranged behind a fixed pitch propeller, a ship can be maneuvered at any mode including going-astern with turning capability, hovering,extra dead slow forwarding, not to mention turning port and starboard, by means of various rudder angle combination of two rudders, with propeller revolution being kept in the forward direction.
● A single joystick lever can control such rudder angle combination of two rudders so that they can control a propeller slip stream and develop thrust in all directions.
● By virtue of such arrangement of VecTwin Rudders that a propeller slip stream is enclosed between two rudders, fluctuation of thrust by wave when navigating can be reduced, and that course keeping quality at straight-ahead-going is excellent. Thus it contributes to reduced power loss and reduced loss of ship speed in fluctuating ocean weathers. Particularly, it is highly appraised that, even in following-sea condition, ship’s yawing is in low level, and safety is secured.
● This system enables easy and short-time approaching to and departing from berth, and hence mental and physical hardships of crew are reduced. From a collective point of view, this is a system that brings an excellent economical effect.
● A Super VecTwin System places its standard on manual operation, but if desired, it can be connected with various automation systems including dynamic positioning.
Special Features of System
● In a Super VecTwin System, a reaction fin provided on the respective rudder blade so as to protrude from its inboard face, where a propeller slip stream passes, when navigating, rectifies the propeller slip stream and produces forward vectored thrust from revolving flux of the propeller slip stream. Thus propulsive efficiency is improved. Furthermore, propulsive efficiency is further improved by means of incorporating in the system propeller boss cap fins (PBCF) that removes propeller hub vortex.
● Excellent maneuverability exhibited by a Super VecTwin System is achieved by incorporated joystick control.
● The System gives a ship hovering function that can keep a ship in the fixed place in situ, with propeller revolution being kept in the forward direction. When a joystick lever is tilted in the right and left directions at the hovering condition, postural control of a ship is obtainable without accompanying movement in the ahead and astern directions.
● With propeller revolution being kept constant in the forward direction, ship speed can be freely controlled by a Super VecTwin System, and even at very low speed or at standstill condition, good steerability is secured. The System can steer a ship in all directions, including going ahead and astern unrestrictedly.
● By virtue of such capability of a VecTwin System provided in the stern as to be able to develop thrust in all directions, combined operation with a bow thruster easily makes it possible for a ship to approach and depart a berth in parallel, diagonally move, and spin in situ. Thus degree of freedom of maneuvering is remarkably improved. Furthermore, in case of a small ship, an excellent maneuvering ability of a Super VecTwin System makes a ship exhibit excellent maneuvering, even without a bow thruster.
● A central joystick is newly provided with an emergency stopping switch in consideration of further strengthening safety of navigation. Simply pushing this switch brings a ship to emergency stop, no matter which maneuvering mode, auto-pilot or manual steering, a ship is taking. Stopping distance in this case is reduced to about a half of that of a conventional ship. Even while such emergency stopping is in operation, ship maneuvering by joystick control that makes a good use of the special properties of a VecTwin System can be put into operation at once, and thus a great ability to avoid a risk is exhibited.
● A Super VecTwin System is composed so that command signals emitted from a joystick are transmitted to a controller, and control respective hydraulic pump units via a servo-amplifier provided in a wheel stand, and the respective hydraulic pump unit operates a respective rotary vane steering gear that operates a respective VecTwin Rudder.
● The following options are prepared for a new type joystick at a customer’s request:(1)A joystick with a CRT(cathode ray tube)that can visualize thrust vector patterns corresponding to a joystick command; and(2)A joystick with a small rudder angle indicator.
● A hovering position indicating lamp is newly provided, and thus it has become easy to confirm the hovering position, that is the standard condition for the rudders, by means of a lamp and a buzzer.
● A rudder angle indicator in a wheel house is so designed as to be easily visual at night.
● A control system is processed by digital signals, and thus control preciseness is high, and that any outside electrical interference is minimized.
● Rotary vane steering gears are employed, which are adaptive to wide operating angle, small sized, and light weighted, compared with a ram-cylinder type steering gear.
●The operating range of respective VecTwin Rudders is 105°in the outboard direction and 25°in the inboard direction.
●Respective rudder angle combination peculiar to the VecTwin System is so devised as to be automatically controlled by a joystick.
(1) Joystick with CRT (cathode ray tube) that displays thrust vector patterns.
・As a new type joystick, a joystick with a CRT for displaying thrust vector patterns has been developed. This is provided with a CRT that displays thrust vector that can be directed in all directions, obtainable by means of combining rudder angle of the respective rudders in a peculiar manner to the VecTwin Rudder System.
・The CRT displays both a joystick command and a resultant thrust vector with its magnitude and direction, and in addition, movement of the respective rudders.
・Thrust becomes mighty as propeller revolution increases.
(2) Joystick with Rudder Angle Indicator.
・A small rudder angle indicator is so designed as to be easily visual at night.
・A joystick body is of water-proof construction, and can be used even in the open air.