AU604183B2 - Otter board - Google Patents

Description

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4183 COMMONWEALTH OF AUSTRALIA Patents Act 1952 f r e I Name of Applicant Address of Applicant Actual Inventor Address for Service ROBERT STEFAN JOHN STANDEN Lot 24, Plantation Road, Edmonton, via Cairns, Queensland, 4870, Australia ROBERT STEFAN JOHN STANDEN GRANT ADAMS COMPANY, Patent Trade Mark Attorneys, 333 Adelaide Street, BRISBANE. QUEENSLAND. 4000

AUSTRALIA.

COMPLETE SPECIFICATION FOR THE INVENTION ENTITLED: "OTTER BOARD" The following statement is a full description of the invention including the best method of performing it known to the applicant.

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THIS INVENTION relates to otter trawl boards as used in the fishing industry, In use of fishing nets, when trawling for prawns, fish etc., otter boards are used as a means of maintaining the mouth of the net open. Conventional otter trawl boards rely on a flat surface that is towed at an angle to the towing boats direction to spread the opening of the net. The weight of the board provides the means to keep the net tracking along the ocean floor. A proportion of a trawler's fuel consumption is expended in the otter board's operation. Lighter, 0 0 oooo smaller boards would enable faster trawling or savings o on fuel. Lighter, smaller boards would be more easily 0000 o0 handled and stowed between usage.

o 0a 0o00 15 It is an object of the present invention to 00ooo"0 provide an otter trawl board with an improved 00 0 performance; that may be lighter and more easily handled; and that enables greater trawl speeds and/or fuel savings. Other objects and various advantages of it the present invention will hereinafter become apparent.

The invention achieves its object in provision of an otter board comprising: elongate upper and lower spaced apart support means; a plurality of vertically oriented mutually spaced apart foils extended between the upper and lower support means; and a plurality of horizontal fins, mutually spaced apart between the upper and lower support means; the support means being each elongate in a direction substantially parallel to the movement of the i other board in use; and the vertically oriented foils being so configured and angled relative to the direction of movement as to generate thrust transverse of the direction of movement.

2 r In the specification the following terms are to be taken to include the meaning indicated unless the context requires something more specific.

FOILS and FINS are single or composite elements providing surfaces acted on by the flow of water thereover so as to generate thrust and/or otherwise influence the direction of travel of the otter board and includes surfaces established from planar or sheet-form stock or more complex two dimensional or three dimensional structures produced by moulding, bending, welding and other suitable manufacturing o 00 oo ooool process ~The invention will now be described with 00'.0 0,0 0 reference to a preferred embodiment which is shown in 0 00 0, 0 15 the accompanying drawings in which: o o0 00 FIG. 1 is a view of an otter board in no oo 00 0 S o 0 accordance with the present invention; FIG. 2 shows the shape of the top fin of the otter board of FIG. 1; o o ro o 20 FIG. 3 is a view of the board of FIG. 1 from above with the top fin removed; 0, 00 FIG. 4 is a view of a weight that might be employed in the board of FIG. 1; FIG. 5 is a view from above of the pivot at which the towing bracket of FIGS. 6 and 7 is attached; FIGS. 6 and 7 are plan and side elevations of a bracket that may be used in conjunction with the otter board of FIG. 1.

FIG. 1 shows a side elevation of an otter trawl board 10 having connection point 11 at the top, a bracket 12 at the side and a connector 13 at the rear.

Bracket 12 is described in greater detail below. The board comprises a plurality of foils 14 to :L6 and fins 17 to 21 mounted above a base structure or foot 23. The foils and fins are described below. The top fin doubles as an upper support means for the connection point 11.

3 In this embodiment three foils and five fins are employed but it should be apparent these numbers might be varied. The foot 23, or lower support means, may have an I-beam type structure with a web 24 between upper and lower plates 25 and 26. Plate 26 may be curved upwardly at 28 at the forward end. *7neath foot 23 there may be attached one or more plates 27, as desired, to add weight to adjust the performance of the otter board FIG. 2 shows the top fin 17 removed to reveal in FIG. 3 the otterboard 10 of FIG. 1 from above. The foils 14 to 16 extend between base plate 25 of the foot 23 and the top fin or support means 17. The fins 18 to 21 comprise infills between the foils and fin 18 is seen, its two parts 29 and 30 being spanned as shown between foils 15 and 16, and, 14 and 15 respectively.

The foils have surfaces transverse of the direction of movement of the otter board which is parallel to the plane of the board. The resulting assembly may be welded together. A pair of lugs 31 and 32 are provided on the front foil 14 for attachment of a towing bracket (described below). The front foil provides two surfaces; a forward planar surface 33 in the plane of the otter board and a rearward planar surface 34, the two surfaces meeting at a line 35. This foil may comprise a bent section of otherwise flat stock. The two rearward foils may be both planar and parallel as shown. The forward edge of the foils may be provided with a bead such as 36 on foil 15 to give the leading edge additional strength. The trailing edges of the respective foils 14 to 16 may be provided with spoilers 37 to 39.

FIG. 4 shows the outline of a weight 27 that may be attached beneath foot 23.

FIGS. 5, 6 and 7 show lug 31 which receives a pin 40 in hollow bar 41 to which connection plate 42 is 4

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mounted for pivotal movement. Plate 42 is provided with holes such as 43 at which a bracket 44 may be attached by bolts or other suitable means. Bracket 44 carries a connector plate 45 with holes 46 for connection of a tow line.

The above described design allows either an increase in speed or a decrease in fuel consumption or both. It holds the bottom better as a result of the design and it fishes cleaner (less trash). The spoilers at the rear of the aquafoils increase the spread force and decrease drag. The leading edge attack angle sets o0000 the response to be expected in adverse conditions. The °000 foils generate the spread force while the fins may oo provide a downwards thrust to assist the board in 0 00 o0Oo 15 holding the sea bed. The use of surfaces with no 0000 compound curves allows for relatively inexpensive 0 0 00 o manufacture.

In the above described embodiment, whilst the fin spacing is shown to be constant from top to bottom S 20 other patterns might be adopted without detracting from r performance. Similarly, the areas and angles of the 0, foils might be varied from front to rear to generate a desired spread force. The spoilers might be produced by bending back the trailing edge of the flat stock employed in the foil with a basically wedge shaped spoiler produced, the sheet edge being welded to the sheet to add strength. The towing plate 42 may be provided with a plurality of holes to enable adjustment of the point of hitching of a towline. A point two to three centimetres above the centre line will be typical.

The forces generated by the fins will be best arranged if these are symmetric about the centre line of the board. The width of the top plate can be chosen to prevent spillage over the edge whereby the pressure on the foil might otherwise be reduced at the upper edge.

i The forward edge of the front foil acts as a shear rudder.

A device as described above will typically be rectangular in shape, 122cm x 84 cm. The top fin will be typically 10cm wide as will be the foot. The weights will be typically plate material 6cm wide and 1.25cm thick.

Whilst the above has been described with reference to a preferred embodiment, it will be apparent that many modifications and variations will be made by persons skilled in the art, which variations are within S« the scope and spirit of the invention hereinbefore set forth.

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Claims (8)

1. An otter board comprising: elongate upper and lower spaced apart support means; a plurality of vertically oriented mutually i spaced apart foils extended between the upper and lower I support means; and i a plurality of horizontal fins, mutually spaced apart between the upper and lower support means; the support means being each elongate in a i Sdirection substantially parallel to the movement of the i otter board in use; and the vertically oriented foils being so i configured and angled relative to the direction of ii 15 movement as to generate thrust transverse of the i direction of movement.

2. An otter board as claimed in Claim 1 wherein the lower support member includes an I-beam type structure along its length beneath which there is or are one or more weight adding plates that are removably attached.

3. An otter board as claimed in either one of Claims 1 or 2 wherein the first foil in the direction of travel has a forward planar section in the plane a 25 parallel to the direction of movement and a rearward planar section transverse thereto. ii

4. An otter board as claimed in Claim 3 wherein i the remaining foils are planar and transverse the direction of travel.

5. An otter board as claimed in Claim 3 or Claim 4 wherein the forward edge of the foils is provided with a strengthening beading and the trailing edges with spoilers.

6. An otter board as claimed in any one of Claims 3 to 5 wherein each of the fins are established by 7i 7 F r planar sections extended between the foils, being integrally bonded thereto.

7. An otter board as claimed in any one of the preceding claims wherein spaced lugs are applied to the first foil in the direction of travel and a pin therethrough pivotally locks an attachment plate at which a towing bracket may be selectively attached at a range of locations therealong.

8. An otter board substantially as hereinbefore described with reference to the drawings. DATED this sixteenth day of February 1989 0o s ROBERT STEFAI JOHN STANDEN o" By his Patent Attorneys o o GRANT ADAMS COMPANY. 0 00 0000 ooo o o 0 00 0o00 0 0 0001 0 00 0 i8 "i I 8 .I -I