At what speed should backing bell or bow thruster be avoided?

The backing bell or bow thruster should generally be avoided at a speed of 7 knots. This is because operating a backing bell or bow thruster at higher speeds can lead to several issues, including diminished maneuverability and increased risk of vessel instability. Specifically, at 7 knots, the hydrodynamics around the vessel change significantly, which could result in less effective thrust and potentially unintended maneuvers. At lower speeds, the effects of the thrusters are more predictable and manageable, providing the crew with better control over the vessel. Additionally, avoiding thruster use at this threshold helps to prevent potential damage to both the thruster and the vessel’s hull due to increased resistance and turbulence at higher speeds.