Trawl Door Pulling Points for Stable Low-Angle Operation
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Solution Overview
Problem
Trawl doors face instability and inefficiency at higher angles of attack, particularly at slower towing speeds, due to increased drag-induced directional forces and varying operational conditions, necessitating a solution for improved stability and efficiency at lower angles of attack.
Innovation Solution
The trawl door design features pulling points located within the channels, allowing operation at significantly lower angles of attack (10-20 degrees) by incorporating an upper and lower frame with aerofoil panels and flexible pulling points, enhancing stability and reducing water resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If trawl doors operate at larger angles of attack to maintain stability under destabilizing forces, then stability is improved, but water resistance increases and efficiency decreases
Solution Approach 1:
The patent applies dynamics by making the trawl door's angle of attack adjustable rather than fixed. The door can dynamically change its orientation relative to the towing direction, allowing it to operate at optimal lower angles during stable conditions while maintaining stability when needed through active control mechanisms.
Solution Approach 2:
The patent changes the operational parameter of angle of attack from a fixed high value to a variable low value. By reducing and optimizing the angle of attack parameter, the system achieves both stability and reduced water resistance, resolving the contradiction between these two requirements.
2Stability of the object's composition
If trawl doors operate at larger angles of attack to maintain stability during vessel maneuvers, then directional stability is improved, but towing efficiency decreases
Solution Approach 1:
The system dynamically adjusts the angle of attack based on operational conditions. During vessel maneuvers when destabilizing forces occur, the door can increase its angle for stability. During normal towing, it operates at lower angles for maximum efficiency, thus resolving the contradiction between directional stability and towing efficiency.
3Stability of the object's composition
If trawl doors are designed for high angles of attack, then stability under destabilizing forces is improved, but performance at shallow depths and high speeds deteriorates
Solution Approach 1:
The patent optimizes the angle of attack parameter for high-speed operation by reducing it to 10-20 degrees. This parameter change allows the trawl door to maintain stability even at high towing speeds and shallow depths, where traditional high-angle designs would create excessive drag and reduce efficiency.
4Device complexity
If pulling points are placed on the inside of the trawl door, then structural integration is improved, but angle of attack becomes too high causing instability
Solution Approach 1:
The patent relocates the pulling points from the inside surface to the outer surface of the trawl door, positioned at the trailing edge. This spatial repositioning in another dimension allows the door to operate at lower angles of attack (10-20 degrees) while maintaining structural integrity, resolving the contradiction between structural integration and stability.
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 design significantly improves stability and efficiency at lower angles of attack, reducing water resistance and preventing tangles, while maintaining operational stability under various destabilizing conditions.
Implementation Method 1
panels (4, 5) connected between the lower (3) and upper frames (2) frames, said panels preferably being of aerofoil construction and connected to the frames in their respective ends, and said panels are placed over each other thereby establishing channels for water to flow through the trawl door
Implementation Method 2
trawl doors operating at large angles of attack create enough drag induced directional forces on the trawl doors so as to impart sufficient stability to the trawl door system
Data Source
Figure 1
Figure 2
AI summary
There is provided a trawl door used for trawl fishing, and more particularly, a trawl door adapted for stable and efficient operation. The door is equipped with pulling points in one or more of the middle frames so as to produce angles of attack relative to a vessel pulling the trawl door of between 10 and 20 degrees.