Statute and history
These tugs are the property of the city of Antwerp and belong to the port authority.
Operation in the port
Their job is to tow the cargoboats from the locks, which connect the river Schelde with the actual port, and assist in the docking of these "giants".
Considering the lack of propulsion and the room to manoever these "colossus" , (they are only allowed to sail under reduced power. The efficiency of the ship's own rudder reduces approximately with the ship's speed squared. As a result, the ship's own controllability decreases rapidly.) Depending on size, windage, environmental and local conditions an enhanced external assistance, of these tugs, is required at different speeds.
Usually, they work in tandem which means that one tug will pull the cargoboat from the front and the other will stear the tow from behind.
This allows, in a turn, the bow of the cargoboat to be pulled in the desired direction, the other tug preventing the stern from swinging out.
When they reach the dockside,the cargoboat is manoeuverd and held against the wall so it can be moored in it's required location
The secret these "boys" have is a mystery to the observer and is to be found underwater actually. One should not look for a rudder or screw because these tugs are equipped with VSP-propellers and nozzle plate under head of the ship and stabilising fin under after ship (skeg). The terms "bow" and "stern" are irrelevant because of the omnidirectional performance of such vessels
The tug is actually built around the propellers
Two propellers because the risk of engine failure still exists and the resulting consequences of such a failure would be disastrous.
The propellers are to be found at 1/3 way up the hull.The blades of the propeller are set up vertically and revolve in opposite directions between the hull and the nozzle.
NozzelThe nozzle effect increases the propeller thrust (comparable to that of a turbine). It also protects the propeller against grounding and supports the vessel in the dry dock.
The "skeg" and the tug's hull, aft of the tow's stern, may be seen as a steering gear forcing the rudder of the tow.
Each propeller is driven by a diesel which supplies the necessary KW. This engine can, thanks to the type of drive, run at the most efficient number of revolutions. The propeller being the gearbox, as it were