It depends on the type of bow thruster, but controllable pitch is more common than not. This allows the thruster itself to remain rotating, but if the pitch is at 0 (neither port nor starboard), then it is effectively idling, not pushing any water. Fixed pitch models are generally smaller (under 500 kW), and the electric drive motor is connected to a variable frequency controller, so the motor speed (and prop speed) is not only adjustable, but also quick to respond.Guest wrote:Thanks for the answers Guest from EU, so is the bow thruster controllable pitch or reversible? You see some of the thrusters on the older ships of 400 hp some 600hp they seemed to get more powerful as time went on, so my question would the 400hp bow thruster or basically any thruster under 1000hp be of much use on a 730 or footer I'm sure if a stiff wind is blowing low hp thrusters would be of little use?
The size of electric motor thruster drive on a ship is determined on the hull form, sail area, size of thruster unit, and others (of particular note is consideration of congested waters and trading routes/maneuverability requirements specific for the lakes). To answer your question of whether a certain size thruster drive unit is effective or not for a certain size ship, the answer is really variable. A ship with low freeboard could require less power than a similar ship with higher freeboard. A faired hull form would offer less resistance than a basic, block-shaped hull. I would venture to guess that a 600 kW unit in a 730' lake boat would be sufficient for most needs.
The Great Lakes ships generally have larger size thrusters than most ocean-going vessels, as the lake boats generally do not use tugs for mooring/un-mooring. By not using tugs, the ships require a greater degree of maneuverability.