Trawl Door with Movable Plate Elements for Variable Hydrodynamic Area
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Solution Overview
Problem
Existing trawl doors face challenges in adjusting spreading force and depth in water without increasing water resistance or complicating the design, making it difficult to optimize performance for various fishing conditions.
Innovation Solution
A trawl door design featuring movable plate elements at the trailing edge that can be displaced or pivoted to adjust the hydrodynamic area, allowing for changes in the aspect ratio and depth without altering fastening points, using manual, electric, or pneumatic drive mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the area of the trawl door is increased to improve spreading force, then the spreading force is improved, but the towing resistance increases
Solution Approach 1:
The patent applies a movable plate element that can be displaced between a retracted position and an extended position, allowing the trawl door's hydrodynamic area to be dynamically adjusted. This enables the spreading force to be optimized for different fishing conditions without permanently increasing the door's size and associated towing resistance.
Solution Approach 2:
The patent changes the effective hydrodynamic parameter (area) of the trawl door by extending or retracting the plate element. This allows the same trawl door to operate with different effective areas, optimizing the balance between spreading force and towing resistance based on specific fishing requirements.
2Force
If the H:B ratio is increased to improve spreading force efficiency, then the spreading force efficiency is improved, but the difficulty of handling on-board increases
Solution Approach 1:
Instead of permanently increasing the H:B ratio with a taller door structure, the patent uses a movable plate element that extends vertically to increase the effective height only when needed. This maintains a compact, easy-to-handle door structure while enabling high H:B ratio operation during fishing.
3Adaptability or versatility
If multiple trawl door sizes are used to optimize for different fishing conditions, then the adaptability is improved, but the device complexity and inventory requirements increase
Solution Approach 1:
The patent makes a single trawl door design universal by adding a movable plate element that can be positioned to create different effective hydrodynamic areas. This allows one door to perform the functions of multiple doors with different sizes, eliminating the need for maintaining an inventory of different door types.
Solution Approach 2:
The movable plate element allows the same physical door to dynamically change its effective size and characteristics, providing the adaptability of multiple door sizes without the complexity of having actually multiple doors or complex switching mechanisms.
4Adaptability or versatility
If a central mechanical drive mechanism in a tube section is used to adjust plate elements, then the adjustability is improved, but the weight increases which disadvantageously influences capability
Solution Approach 1:
The patent extracts the drive mechanism from a centralized tube section and distributes it to individual plate elements. This allows each plate element to be driven independently by simpler, lighter mechanisms, reducing the overall weight while maintaining full adjustability.
Solution Approach 2:
Instead of using a single centralized drive mechanism in a tube section, the patent segments the drive system so that each plate element has its own drive mechanism. This distribution of the drive system reduces concentration of weight in one area and allows for more efficient, lighter overall design.
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
Enables adjustable spreading force and depth without significantly increasing water resistance, allowing for optimized performance in different fishing conditions without the need for multiple trawl door sizes or complex mechanical systems.
Implementation Method 1
the plate element can be moved between two positions, a first position in which the plate element is substantially disposed along a non-perforated region of the fixed body plate or airfoil profile, and a second position in which the plate element is moved a length relative to the fixed body plate or airfoil profile such that the active hydrodynamic area of the trawl door is increased thereby
Implementation Method 2
The spreading force, which is the lateral force exerted by a trawl door for spreading the mouth of the trawl net, is greater the larger the area of the trawl door as seen from the side
Data Source
Figure 1~2
Figure 3~6
Figure 7a~9
AI summary
The invention concerns a pelagic trawl door with variable hydrodynamic area. At its trailing edge (12) the trawl door is provided with movable plate elements (13, 14) that may be displaced in longitudinal direction of the trawl door. An opening (21) or a region at the trailing edge (12) can thereby be opened up or covered by a plate element (13, 14). The displacement can be effected by means of a screw spindle (22) which is operated manually or driven by an electric motor. By the invention is achieved a simple and light construction where a change in the area of the trawl door can occur such that a reduction in lateral force at the same time results in reduction of the towing resistance, thereby maintaining or enhancing the effect of the trawl door during fishery.