BOW THRUSTER BT100Kgf

18

2.1 TUNNEL LOCATION

Point of Boat

Rotation

B = 9 mt

A = 10 mt

Tunnel

Fig. 2

Fig. 1

To obtain the best result, locate the tunnel of the bow thruster as close as possible to the bow of the boat

(Fig. 1). Because of the leverage effect, the thrust of the unit is detriment from the distance from the tunnel relative to the

rotation point of the boat. (Fig. 2).

Example:

A: 55Kg of thrust x 10m of leverage = 550Kgm Torque.

B: 55Kg of thrust x 9m of leverage = 495Kgm Torque.

In position A is noted a 10% of torque more.

In a plaining hull boat, locating the tunnel in such a way will result with the tunnel over the water line level, so to avoid any obstacle. (Fig. 3).

In case of large dimension boats, one can install two bow

thrusters one after the other. In this case, according to meteorological conditions, the units can be used separately or simultaneously (Fig. 4).

The position of the tunnel has to be as low as possible for the following reasons (Fig. 5):

• To prevent from any air which can be pulled resulting in weakening the thrust available.

• To have the highest pressure of water possible to utilise the maximum efficiency of the propeller.

Generally the highest part of the tunnel must be 1/2 x Diameter of the tunnel bellow the water line level. This is just the minimum possible but we recommend that at least 3/4 x

Diameter under the water line. The optimal distance is approximate 1/1 x Diameter.

The optimal length of the tunnel should be 2 or 4 times the diameter of the tunnel; must be avoided tunnels longer than

6/7 times the diameter, to avoid losses of thrust. Should the tunnel be so long, the internal distance will reduce the velocity of water and so the thrust. Should the tunnel be very short

(normally in the lower part of the tunnel) could result in cavitations and so reduction of the performance and create noise (Fig. 6 e 7).

PLAINING HULL BOAT

Tunnel

Water Level

Fig. 3

IMBARCAZIONE DI GROSSE DIMENSIONI

Bow-thruster

Water Level

Fig. 4

Fig. 6/7

Fig. 5