In height adjustable Veth L-drives.
Because of the huge efficiency advantages and better manoeuvrability, VOF Amulet chose to equip the ship with L-drives from manufacturer Veth Propulsion.
Meanwhile, the comparable system experience has been acquired with the current ship from Frans and Igor Jansen, the MTS Jade. On this ship, Z-drives were used. After putting it into use, MARIN took some measurement tests. The conclusion of MARIN is that using the thruster system provides an efficiency advantage of 15% compared to the regular drive, as it is common in the inland shipping with the propeller shaft, reversing-clutch and rudders
The L-drive system, which is used on the MTS Amulet, has some extra advantages on top of the Z-drives from the MTS Jade. First of all, the L-drive has a transmission less, as a result of this; there will be less friction loss. Secondly, the L-drive is height adjustable; because of this the propulsive efficiency of the propeller can be used optimally.
A big advantage of the possibility to adjust the L-drive in height, is the fact that the ship does not need to set ballast, because man can move the propellers by empty sailing.
In practice it turns out that circa 50% of the bunker barges sail empty and that an enormous efficiency loss occurs, because the ships have to take ballast water in the stern to get enough water with the propulsion propellers. After all, the propellers have to be underneath the water at all times. First of all, the result of this is that the ship is not straight in the water anymore, but backwards. This leads to a much higher resistance during sailing, because the ship will ësuckí and hold water. Moreover, the propellers push the water a bit down instead of straight back. Secondly, the ballasting itself costs energy, because the pumps have to be driven. An additional environmental advantage is the fact that there will not come any more ballast water in the water surface and that the ballast tanks will need less coating.