BENEFITS
BASIC PRINCIPLES AND CONSEQUENT BENEFITS
Essentially a waterjet drive is like an aircraft turbojet with the difference that the operating fluid is water instead of air. The propelling force is generated by adding momentum to the water through accelerating a specific flow of water sternward.
Water flow from under the vessel is fed through an inlet duct mounted at the transom, flush to the hull bottom, into an inboard pump (the impeller) adding head to the water. A movable grid is fitted at the duct water inlet to protect the intake.
From the pump, the water flow passes through an integrated stator which removes the water swirl generated by the impeller and converts all this pressurized energy into speed, discharging a straight high-speed jet much higher than the boat speed. This water acceleration generates the thrust which propels the boat.
Steering thrust is achieved by deflecting the water flow by means of steering nozzle while reversing thrust is achieved by deflecting the water flow in forward direction by means of a reversing bucket.
When the reversing deflector is placed in an intermediate neutral position, the water flow is equalized. In this way, vertical neutral thrust can be achieved independently from the pump speed resulting in zero forward and backward thrust which keeps the boat at a standstill, while full steering is available for precise manoeuvring.
Fine trimmable forward, backward and side movements can be achieved simply by raising and lowering the reversing bucket from the neutral position and by moving the steering nozzle.
Water flow from under the vessel is fed through an inlet duct mounted at the transom, flush to the hull bottom, into an inboard pump (the impeller) adding head to the water. A movable grid is fitted at the duct water inlet to protect the intake.
From the pump, the water flow passes through an integrated stator which removes the water swirl generated by the impeller and converts all this pressurized energy into speed, discharging a straight high-speed jet much higher than the boat speed. This water acceleration generates the thrust which propels the boat.
Steering thrust is achieved by deflecting the water flow by means of steering nozzle while reversing thrust is achieved by deflecting the water flow in forward direction by means of a reversing bucket.
When the reversing deflector is placed in an intermediate neutral position, the water flow is equalized. In this way, vertical neutral thrust can be achieved independently from the pump speed resulting in zero forward and backward thrust which keeps the boat at a standstill, while full steering is available for precise manoeuvring.
Fine trimmable forward, backward and side movements can be achieved simply by raising and lowering the reversing bucket from the neutral position and by moving the steering nozzle.
WATERJET TYPICAL BENEFITS
SPEED
Above speeds of approximately 30 knots the traditional fixed pitchpropeller, an open stream machine, cannot operate due to the poor priming of its blades. The introduction of a case which produces a radial discontinuancewith the outside, allows an increase of the priming of the turbo-machinery blades and the achievement of higher speeds (40 – 60 knots depending on waterjet design).
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MAXIMUM ACTIVE & PASSIVE SAFETY FEATURES
The absence of open rotating parts provides complete safety for people in the water. Rescue operations by divers for survivors can be safely performed with the engine running to withstand wind or currents. The reversing bucket may be quickly activated to stop the boat at any speed, within 1.5 times its length.
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RUNNING COMFORT
The absence of high speed cavitation pressure peaks, caused by proximity of the propeller blades to the hull and torque effects, drastically reduces hull vibrations and under water noise.
MAXIMUM RELIABILITY, LOW VULNERABILITY, ENDURANCE
It is impossible to damage the impeller, shafts or steering and reversing actuators in the event of grounding as nothing protrudes from the keel.There is no danger of vital components (control levers, hydraulic rams) being affected by sea incrustations, by corrosion or by impact as these are all inboard mounted where they are serviceable without docking the vessel.
EXCELLENT MANEUVRABILITY AT SPEEDS IN ANY POSITION
The boat speed and direction can be adjusted continuously, independently from the pump speed, by setting the bucket, without the impeller losing its grip on the water, because it is never disengaged. This is a great advantage because the maximum thrust is available at low speed or performing precise maneuvers while in severe conditions, in contrast to traditional propulsion systems in which thrust increases boat speed.
In a twin installation, using one drive in reverse, the other in neutral (and balancing their thrusts to keep the boat at a standstill), it is possible to move the boat sideways while adjusting the steering nozzles, without the use of bow thrusters or electronic control systems. |
CASTOLDI WATERJETS ADDITIONAL BENEFITS
LIGHTER
The Castoldi waterjet drive is very light due to the aluminium alloyconstruction of its principle parts. The gearbox is integrated in the unit therefore the engine need not be provided with a marine transmission.
All this makes Castoldi waterjets the lightest ones on the market, even lighter than the smaller waterjets of other manufacturers, when combined with the weight of the marine transmissions. |
SIMPLIFIED ENGINEERING & INSTALLATION
Every Castoldi waterjet drive is equipped and delivered in a single module which includes a propulsion system with water intake, duct, steering and reversing devices, with top quality equipment required for its installation, interconnection and control, to ensure the best performance.
All this produces a pre-assembled, factory tested package; each waterjet incorporates its own self-contained hydraulic system for actuating the reversing bucket, the steering nozzle, the hydraulic clutch and the movable grid.
All this produces a pre-assembled, factory tested package; each waterjet incorporates its own self-contained hydraulic system for actuating the reversing bucket, the steering nozzle, the hydraulic clutch and the movable grid.
TOP PERFORMANCE
High efficiency at medium to high speeds (25-60 knots) due to the following: The axial flow impeller has been designed to achieve the highest efficiency and the best resistance to cavitation.
The lowering of the impeller shaft, made possible by the integrated gearbox, allows the design of a flat, straight duct enabling the water stream to flow smoothly with minimum hydrodynamic losses at high speed. |
PERFORMANCE IN SHALLOW & SANDY WATER
Castoldi waterjets are the best choice for boats operating in shallow and sandy waters for the following reasons:
The axial flow impeller is less sensitive than mixed flow impellers to clearance which may be formed between the impeller and the impeller housing. There is no water lubricated tail seal with support function, which would be vulnerable in sandy waters, and could induce vibrations and consequent damage to shafts, gearboxes, engines and hulls. The impeller shaft rotates safely inside the fin oil chamber, and is therefore perfectly protected from sand or debris being suctioned into the waterjet. |
SEA-KEEPING CHARACTERISTICS & COURSE STABILITY
The water intake is positioned as closely as possible to the stern thus limiting aeration during rough water conditions. The “holdfast effect” of the water intake and the mass of water flowing into the duct contribute to keeping the boat in contact with the water surface and stable.
The lowering of the impeller shaft and consequently the centre of thrust, allowed by the integrated gearbox, provides optimum course stability. |
MINIMUM POSSIBILITY OF WATER INTAKE & DUCT CLOGGING
The water intake is protected by the movable debris screen grid which,in most situations, blocks and rejects debris. The limited number of impeller and stator blades allows the easy transmission and discharge of ingested debris which, in any case, would not damage the impeller shaft as this turns in an oil bath inside the fin.
If, in the remote event that, despite all this prevention, the waterjet does become clogged, it is possible to manually remove the debris by opening the inspection hatch, positioned close to the water intake. On request the superior Castoldi Clear-Duct unclogging system can be installed.
If, in the remote event that, despite all this prevention, the waterjet does become clogged, it is possible to manually remove the debris by opening the inspection hatch, positioned close to the water intake. On request the superior Castoldi Clear-Duct unclogging system can be installed.
SIMPLIFIED MAINTENACE, MINIMIZED OVERHAUL
The Castoldi waterjet may be disassembled and accessed for inspection in just a few seconds, simply by removing the rear part.The impeller is driven by the spline shaft and it is kept in place by a single special screw which also acts as an extractor for easier removal.
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LONGER SERVICE LIFE
Longer service life is achieved through rugged construction and full protection against corrosion.
The whole unit is protected by a hard anodizing treatment, plating all light-alloy components with 60 microns thickness of aluminum oxide (ceramic), three layers of special paint and cathodic protection by sacrificial anodes. All the main parts (impeller, impeller shaft, etc.) are manufactured with the best available materials (AISI 316 L, Duplex, Titanium etc…).
The whole unit is protected by a hard anodizing treatment, plating all light-alloy components with 60 microns thickness of aluminum oxide (ceramic), three layers of special paint and cathodic protection by sacrificial anodes. All the main parts (impeller, impeller shaft, etc.) are manufactured with the best available materials (AISI 316 L, Duplex, Titanium etc…).
MODELS
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TurboDrive 240 L.V.T
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TurboDrive 284 H.C.T
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TurboDrive 284 L.V.T
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TurboDrive 340 H.C
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TurboDrive 400 H.C
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TurboDrive 490 H.C.T
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TurboDrive 600 H.C.T
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