Tugboat Propulsion Positioning for Heading Control
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Solution Overview
Problem
Carrousel-type tugboats face suboptimal control of heading during towing and require excessive engine thrust, which limits the efficient utilization of their power and increases the need for engine force to generate towing forces.
Innovation Solution
The tugboat configuration positions one propulsion unit ahead and one behind the center point, with a distance of at least 10% of the vessel's length, allowing minimal engine thrust to correct moments and utilizing hydrodynamic resistance to increase tug cable tension, and employs Voith Schneider Propellers or azimuth thrusters for sideways force generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the propulsion units are positioned close to the centre point, then the device complexity is reduced, but the ability to control the tugboat's heading during towing deteriorates
Solution Approach 1:
The propulsion units are positioned at a vertical distance from the waterline rather than being placed symmetrically around the centre point in the longitudinal direction. This vertical positioning creates a moment arm that enables effective heading control without requiring longitudinal separation, thus maintaining simplicity while improving controllability.
Solution Approach 2:
The hydrodynamic resistance of the hull acts as a counterforce to the towing force, creating a balancing moment that works together with the propulsion units. This natural counterweight effect reduces the need for complex propulsion positioning while maintaining stable heading control.
2Ease of operation
If engine thrust is increased to control the tugboat's heading, then the heading control improves, but the use of energy increases
Solution Approach 1:
The hull's hydrodynamic resistance automatically provides a counterforce during towing operations. This self-generated resistance reduces the need for additional engine thrust to maintain heading control, as the water resistance naturally opposes the towing force and creates stabilizing moments.
Solution Approach 2:
The hydrodynamic resistance serves as a natural counterbalance to the towing force, creating moments that assist heading control without requiring proportional increases in engine thrust. This counterweight effect from water resistance reduces energy consumption while maintaining control effectiveness.
3Stability of the object's composition
If the vertical distance between the centre point and waterline is increased, then the stability improves, but the tugboat gets elevated too much above the waterline causing stability to be negated
Solution Approach 1:
The optimal vertical distance ratio (Hcp/Hp between 0.3-1.5) provides a quantitative parameter that balances stability and submersion. This parameter optimization ensures the tugboat achieves maximum stability from the vertical positioning effect while maintaining sufficient hull submersion for hydrodynamic stability and operational effectiveness.
4Force
If a larger hull is used to generate high dynamic forces, then the towing capability improves, but the weight and complexity increase
Solution Approach 1:
The system generates high dynamic forces through dynamic positioning of the propulsion units and utilization of hydrodynamic resistance during towing operations. The vertical positioning creates dynamic moments that amplify the effective towing force without requiring proportional increases in hull size or weight, enabling a smaller hull to achieve the same dynamic performance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration achieves significant dynamic forces with reduced engine power, allowing for high towing capabilities with a smaller hull and minimizing the need for engine thrust, as demonstrated by test results showing substantial steering and braking forces with lower propulsive power.
Implementation Method 1
a hydrodynamic resistance force created by the submerged hull is used to increase the tension of the tug cable
Implementation Method 2
the propulsion units comprise one or more Voith Schneider Propellers (VSP's). Such VSP's are particularly useful for generating sideways forces, especially when towing at large towing angles
Implementation Method 3
the propulsion units comprise one or more azimuth thrusters. Such thrusters can also be advantageously used to generate sideways forces
Data Source
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AI summary
The invention relates to a tugboat (1), comprising a single hull (2), a deck (3) and a towing system (4) having a base (5) connected to the deck, the base having a centre point (CP), and a cart (6) that is moveable over the base over 360°, wherein the cart comprises a powered winch (7), wherein two propulsion units (12) are provided, capable of providing thrust over 360° in a horizontal plane, wherein the propulsion units are aligned in the longitudinal direction, wherein the distance between the propulsion units is at least 10% of a length (L) of the tugboat in the longitudinal direction, wherein the tugboat is configured such that during towing the vertical distance between the centre point and the waterline (Hcp) divided by the vertical distance between the centre of thrust of the propulsion units and the waterline (Hp) is 0,3 - 1,5.