Hydrofoil trawl door
AssigneeMassachusetts Institute of Technology
InventorClifford A. Goudey
Life of this patent
Estimating the term…
Abstract
A hydrodynamically superior trawl door with increased efficiency in harvesting fish and reducing fuel expenditures is composed of curved steel panels, which may be of constant radius to allow for economy in manufacturing. The door approximates an ideal hydrofoil surface, presenting a streamlined surface to the flow of water and a relatively sharp hydrodynamic trailing edge, and allowing for a moderate angle of attack and a high lift coefficient. The door is hollow and may be airtight and contains a flood opening with a baffle to allow air to be trapped inside to provide, even when hydrostatically compressed, some measure of vertical stablity. Further, the water ballast is automatically jetisoned during hauling in. The bottom of the door is curved to allow easy clearance of seafloor obstructions.
Claims33
A trawl door with a hydrofoil cross-section comprising:
- a plurality of connected substantially rectangular first, second, and third plates,
- the cross-sectional shape of said door defined by a plurality of curved sections of said plates, the first plate of which is convex outward,
- the second plate is concave outward, one end of each first and second plate being joined at their ends to form an acute angle at the trailing edge of said door, the third plate is convex outward and at one of its ends joins the second plate at its remaining end, the tangents of the second and third plates coinciding at their juncture to form a smooth point of inflection;
- a pipe, the remaining ends of the first and third plates are joined with said pipe, whose radius is at least an order of magnitude smaller than the radius of said first and second plates, to form a convex arc such that the tangents of the first and third plates when they are joined to the pipe form a fair surface with said pipe, said pipe arc forming the leading edge of said door,
- said assembly of first, second, and third plates and pipe having a cross-section in the form of a hydrofoil having high lift and low drag,
- a first and second end plate, the unconnected ends of said first, second, and third plates and said pipe ends being attached to said end plates,
- one of said end plates being substantially heavier than the other to form the bottom of said door,
- at least one opening in said door near its bottom being so constructed as to allow water to enter and exit the interior of said door.
A trawl door with a hydrofoil cross-section comprising
- a first and second plate, each plate being curved, said plates being joined at one end of each at an acute angle to form the trailing edge of said door,
- a pipe for forming the leading edge of said door,
- said first plate forming a convex arc being joined at its other end to said pipe, to form a first junction running along the length of said pipe,
- said second plate forming a concave arc being joined at its other end to said pipe to form a second junction running along said pipe on substantially the opposite side of said pipe from said first junction,
- said pipe radius having a radius sufficiently large so that the tangents of the first and second plates when they are joined to the pipe form a fair surface with said pipe and the portion of said pipe between said points with first and second plates form a convex pipe arc, said pipe arc forming the leading edge of said door,
- end plates fastened to the remaining ends of said plates and the ends of said pipe to form a hollow trawl door of substantially hydrofoil cross-section, one of said end plates being subtantailly heavier than the other to form the bottom of said door,
- said door having at least one opening near its bottom to provide a flooding port to allow water to enter and exit the interior of said door when said door is immersed in water.
Dependencies are inferred from the claim text.