All About Vetus Bow Thrusters
Having a bow thruster gives you positive control of your boat, even at low speed and regardless of wind, current or tight docking conditions. This overview of the relevant factors will help in the selection of the correct model.
The thrust force determines the effectiveness of a bow thruster and not the output of its electric motor (in hp or kW). This thrust is the result of a combination of the following factors: The power of the electric motor, the propeller shape, dimensions and r.p.m and the efficiency losses in the tunnel. VETUS bow thrusters have a thrust of between 37 to 51 lbf per kW motor power!
In addition, a smaller tunnel diameter allows the tunnel to be installed further forward, which increases the turning moment of the boat. VETUS thrusters provide the optimum combination of high thrust efficiency and low resistance while under way. Tunnels are available in fiberglass, aluminum or steel to suit different hull materials.
The nominal thrust force is only obtained under optimum conditions and the following factors will reduce the efficiency:
• Low input voltage at the motor, due to undercharged batteries.
• Excessive voltage drop due to battery cables which are too long or thin.
• Insufficient battery capacity.
• The shape of the tunnel openings.
• Bars or grilles over the tunnel openings, as well as their shape.
THE TAIL PIECE
VETUS bow thrusters are equipped with a streamlined bronze tail piece. This has proven to be stronger and more durable than other materials sometimes used, while creating the minimum of turbulence, lowest efficiency loss and lowest noise levels. The metal underwater parts are protected by a zinc anode, which is fitted as a standard component.
VETUS propellers are corrosion-free and on thrusters up to the 352 lbf model, are made of synthetic materials. Due to their low weight, the maximum thrust force is obtained very quickly and with a minimum of energy. The propeller blades are specifically designed for use in a tunnel and are shaped in such a way that the thrust is equal to both starboard and port. Because of this,
cavitation is largely avoided and noise levels are considerably reduced. Thruster models over 352 lbf have bronze propellers for increased strength and blade loadings.
Advantages of having one only propeller:
• Easier fitting in the middle of the tunnel.
• Smaller wet surface, therefore less loss of power through friction, resulting in better thrust performance.
• Easier to fit ina tunnel of which the size is more than one arm's length.
• Less risk of damage, therefore less maintenance costs.
THE ELECTRIC MOTOR
VETUS bow thrusters use high efficiency electric motors for maximum power and longevity. In contrast with modified starter motors, these allow continuous running at full power for several minutes.
The motor may be installed at any angle between vertical and horizontal. This greatly increases the range of installation possibilities, even in the tightest space.
Stern Thruster Options
Any Vetus Bow Thruster can be made to serve as a Stern Thruster, however There are four Models of Vetus Bow Thrusters that have an optional Protective Kit that makes them more suitable for use as a Stern Thruster
These are the:
*It is not safe to install a conventional electric stern thruster in the engine room, or compartment containing fuel tanks , of a gasoline powered boat, as gasoline fumes may be ignited by internal sparking in the thrusters motor.*
when installed correctly the Protective Kit will allow stern thrusters installations in gasoline powered boats to be made safely, VETUS has developed, sealed motor housing kits, meeting the requirements of the ISO 8846 Marine Standard ("Ignition protection").
Each set consists of (apart from the bow thruster) a watertight housing (IP65) for the electrical motor and its relays, seals, and electrical connectors and fastening components. In addition, a circuit breaker is supplied, accessible without opening the motor housing.
These protective kits are available for the 55 kgf (121 lbf) bow thrusters (IP55SET), as well as for the 75 (165lbf), 95 (210 lbf) and 125 kgf (275 Ibf) Thrusters (IP75SET)
These motor protection kits are also ideally suited for thrusters installed installed in damp conditions such as those found in the un-conditional bow compartments of high speed, long range, fishing boats in tropical climates.
*Need more information, or specifics? check out How to size Vetus bow thrusters