Page 170 - Vetus

DOCKING

Thrusters can take the stress out of docking by giving you sideways control of the movement and position of the bow and the
stern of your boat. They work by rotating a propeller (at very high speed and power) in a submerged tube or a housing mounted
athwartships (across the boat), and located near the bow and/or the stern.
A simple control panel (usually a joystick) allows you to push the bow and/or stern sideways, to resist the force of a crosswind and
cross current, while you are docking or maneuvering in close quarters (getting in or out of the marina).
What thrusters will do for you and your boat

• Allow you to maintain control while docking and manoeuvering, even into a very tight slip in a crowded marina
• Allow a single crew member to pick up and secure the dock lines while you move the boat sideways from one piling or mooring
buoy to the next - slowly, carefully, quietly and with very little pushing, pulling or shouting.
• Allow you and your one-person crew to handle and control a much bigger and more comfortable boat
• Avoid the possibility of hitting another boat, a dock or a piling, that might cause expensive damage to your boat, another boat or
the marina facilities
• Minimize the risk of a crew member being injured during docking manoeuvers in difficult conditions
• Allow you to handle your boat with the same expertise, grace and panache as the other captains whose boats are equipped with
VETUS thrusters
• Make boating more fun

VETUS offers a solution for each and every boat. From small to big boats, with a shallow or deep draft, slow or fast, electrically or
hydraulically driven. New products are continuously introduced and existing products are frequently updated, so please go to
www.vetus.com for the latest developments.

HOW TO CHOOSE THE CORRECT BOW AND STERN THRUSTER

After you have selected your type of thruster, the following tool can be used to calculate the required thrust force or you can use
the table below to select your ideal thruster.

The influence of the wind
The force applied to the boat by the wind is determined by the wind speed, the wind angle and the lateral wind draft area of the
boat. If the wind blows at right angles to the boat, this wind pressure is most difficult to counter. However, this is seldom the case
and as most boat superstructures are fairly streamlined, a reduction factor of 0.75 is generally applied, when calculating the wind
pressure.

The turning moment
The turning moment is calculated by multiplying the wind force by the distance (A) between the centre of effort of the wind and
the point of rotation of the boat. In order to simplify this somewhat: for the vast majority of boats a rule of thumb may be applied
that the turning moment is calculated by multiplying the wind force by half of the boat’s overall length.

The thrust force
It is the thrust force which is the true measure of a bow thruster’s usefulness and not the output of the electric or hydraulic motor
in kW or HP. The nominal thrust force is a combination of the motor power, the shape of the propeller and the efficiency losses
inside the tunnel. VETUS electrical bow thrusters have a very high thrust of between 17 and 23 kgf per kW motor power. The
required thrust force to counter the effects of the wind is now calculated by dividing the turning moment by the distance (B)
between the centre of the bow thruster tunnel and the pivot point of the boat.
Note
The further forward the tunnel can be positioned, the greater effect the thruster will have.

Wind force Description Wind speed Wind pressure
Beaufort m/s (ft/s) N/m - (kgf/m )
2
2
4 moderate breeze 5,5 to 7,9 (17 - 27) 20 to 40 - (2,0 to 4,1)
5 fresh breeze 8,0 to 10,7 (27 - 37) 41 to 74 - (4,2 to 7,5)
6 strong breeze 10,8 to 13,8 (37 - 47) 75 to 123 - (7,7 to 12,5)
7 near gale 13,9 to 17,1 (47 - 57) 125 to 189 - (12,7 to 19,2)
Pivot point Point of attack 8 gale 17,2 to 20,7 (57 - 67) 191 to 276 - (19,4 to 28,2)
wind force Thrust force
Centres of rotational effort

170 Maneuvering systems - Want to know more? Visit www.vetus.com