Bendable Trim Tab Curvature Control for Boat Drag Reduction
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Solution Overview
Problem
Prior art trim tabs have limitations in effectively changing the attitude of a boat due to abrupt changes in the water surface contour, leading to flow separation and poor lift-to-drag ratios, with excessive drag generated for lift, and are prone to fatigue failure during excessive downward motion.
Innovation Solution
A trim tab shape control system utilizing a regressive flexural stiffness beam and multiple force rams to control the curvature of a bendable trim tab, allowing for optimized up and down deflections, minimizing boundary layer separation, and distributing forces across the trim tab to enhance lift and reduce drag.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a hinged flat plate trim tab is used, then the trim tab can be mechanically actuated to change boat attitude, but it causes abrupt changes in water surface contour leading to flow separation and poor lift-to-drag ratio
Solution Approach 1:
The patent applies curvature by designing the trim tab as a bendable plate that forms a smooth curved surface when deflected, rather than an abrupt flat plate. This curved geometry eliminates flow separation by maintaining smooth water flow along the trim tab surface, directly resolving the technical contradiction between mechanical actuation capability and flow separation prevention.
Solution Approach 2:
The patent implements dynamics by using a bendable trim tab with varying flexural stiffness that can dynamically adjust its curvature based on deflection angle. The trim tab transitions from a rigid flat plate to a flexible curved surface, allowing the geometry to adapt to different operating conditions and maintain optimal hydrodynamic performance throughout the range of motion.
2Object-generated harmful factors
If a bending flat plate trim tab is used, then the contour change is softened reducing flow separation, but excessive drag is generated for the lift produced
Solution Approach 1:
The patent applies local quality by varying the flexural stiffness along the length of the trim tab, with different sections having different stiffness characteristics. This allows the trim tab to exhibit optimal curvature in high-flow regions while maintaining structural integrity, thereby reducing drag in critical areas without compromising overall structural strength.
Solution Approach 2:
The patent implements parameter changes by modifying the flexural stiffness parameter of the trim tab material and geometry. By carefully selecting material properties and cross-sectional dimensions, the trim tab achieves the optimal balance between curvature formation (for reduced flow separation) and structural rigidity (for reduced drag), resolving the contradiction between smooth contour and energy efficiency.
3Strength
If a trim tab with equal stiffness in up and down directions is used, then structural integrity is maintained, but excessive downward motion causes fatigue failure
Solution Approach 1:
The patent applies asymmetry by designing the trim tab with different effective stiffness characteristics for upward and downward deflection. The asymmetric design allows greater flexibility in the downward direction for corrective actions while maintaining sufficient upward stiffness for normal operation, preventing excessive motion that would lead to fatigue failure while preserving structural integrity.
Solution Approach 2:
The patent implements beforehand cushioning by incorporating features that limit extreme downward deflection before fatigue damage can occur. The asymmetric stiffness distribution and structural design provide inherent protection against excessive motion, cushioning against fatigue failure in advance while maintaining the necessary flexibility for effective trim control.
4Manufacturing precision
If multiple force rams are used to control trim tab curvature, then precise control and optimized lift-to-drag ratio are achieved, but device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the trim tab into multiple sections that can be independently controlled by separate force rams. This segmentation allows precise control of curvature at different locations along the trim tab, optimizing hydrodynamic performance while distributing the complexity across modular components that can be independently designed and maintained.
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
The system achieves improved lift-to-drag ratios, increased down trim capabilities without fatigue, and enhanced stability by controlling the trim tab's curvature to optimize boat attitude and reduce drag, while maintaining long cycle life and precise control.
Implementation Method 1
A trim tab shape control system utilizes a regressive flexural stiffness beam and multiple force rams to control the curvature of a bendable trim tab
Implementation Method 2
When underway, water rushes under the boat, causing the rear of the boat to be deflected up or down by the trim tabs
Implementation Method 3
A trim tab shape control system utilizes a regressive flexural stiffness beam and multiple force rams to control the curvature of a bendable trim tab
Data Source
AI summary
A trim tab shape control system for a boat with a transom according to an embodiment of the present invention includes a flexible plate and a trim tab control system. The flexible plate has a forward end attached to the transom, a rearward end, and an operative bottom surface. The trim tab control system includes a first force mechanism that is attached near the rearward end of the flexible plate and at least one second force mechanism interfacing the flexible plate between the transom and the first force mechanism. The force mechanisms are operative to deflect the operative bottom surface of the flexible plate in a controlled curve while in an up position, where the plate retains a shape in a down position which varies with force applied by the first and second force mechanisms and the operating conditions of the boat.