IL123461A - Fishing trawl net assembly - Google Patents

Abstract

A fishing trawl net aseembly (10) arranged to be drawn by a powered vessel (12), said assembly comprising a plurality of connected substantially conical nets (14, 16) a base (18, 20) of each said conical net being open to allow ingress of water and fish, said conical nets being interconnected at said bases and arranged so that in use the apex (24, 26) of each of said conical nets substantially faces away from the direction of motion of said vessel. 2639 י" ד בחשון התשס" ב - October 31, 2001

Description

123461/3 (16.04, A FISHING TRAWL NET ASSEMBLY 123461/2 - 1 - The present invention relates to fishing nets, and particularly to fishing nets adapted for shrimp fishing, in a method known asvtrawl,for " trawling" .

More particularly, the invention specifies a traw net of a conical hopper-like structure which is dragged along near the bottom of a body of water by a boat and collects fish while being pulled through said water.

Fishing by means of nets has long been known. Nets of large size are pulled by one or two motor boats or ships. In order to catch fish which are found near the bottom of the sea there have been developed nets of specific structure and shape, such as trawler nets.

Fishing with a large net raises the problem of supplying adequate ship propulsion power, since the net contains a large volume and creates high fluid resistance. For economic reasons large nets are preferred, as the larger the spread of the opened net, the larger the catch.

However, increasing the size of the opened net spread increases its volume, thereby correspondingly increasing its drag resistance. Such resistance poses a serious problem for a small fishing trawl, which is unable to pull such a net at an acceptable speed.

A typical fishing boat, powered by a 140 H.P engine, towing standard American trawl gear, and having a net spread of 15 to 17 meters, achieves a speed of 2.2 knots. Any attempt at using a larger net results in serious loss of boat speed, unless a more powerful boat, such as a 250 H.P. trawl, is used.

A further disadvantage arises in using a prior-art large conical net where the intention is to fish near the bottom of a sea or river, for example when shell fish are to be harvested. Only a small portion of such a net will collect from near the water bottom, most of the net will be far higher and will therefore be less effective.

In US Patent No. 4,771,565 Shepherd discloses a bottom trawl roller intended to overcome friction as a trawl net is dragged along the ocean bottom. While his device is intended for harvesting shell fish and the like, the disclosure does not E:\2MAIN\D68\68243A.DOC concern itself with minimizing fluid drag which is the primary concern of the present invention.

It is therefore one of the objects of the present invention to obviate the disadvantages of prior art trawl nets and to provide a trawl net with a large total swept volume, and yet which has low resistance to motion through water or drag resistance.

The present invention achieves the above object by providing a trawl net assembly arranged to be drawn by a powered vessel, said assembly comprising a plurality of connected substantially conical nets, the base of each said conical net being open to allow the ingress of water and fish, said conical nets being interconnected at said base and arranged so that in use the apexes of said cones all substantially face away from the direction of motion of said vessel.

In the preferred embodiment the trawl nets are interconnected by means of riggs so as to maintain the desired function.

In a further preferred embodiment of the present invention there is provided a trawl net assembly arranged to operate substantially below the water surface.

E:\2MAIN\D68\68243A.DOC In a most preferred embodiment of the present invention there is provided a trawl net assembly wherein the net mesh is sized for the collection of shrimps and other shellfish.

Yet further embodiments of the invention will be described hereinafter.

The fluid drag produced by a deployed fishing net is a function of many variables, such as net shape, mesh size, and wave generation; however, other factors being equal the total volume enveloped by the net in use is approximately proportional to the generated drag.

In this regard, the following illustrative example using figures which are typical to Israeli practice, shows how in the present invention total volume, and thus drag, is lower in comparison with a prior art net of identical swept area.

Prior Art Present Invention Swept area, sq. meters 201 201 No. of cones 1 2 Open cone base dia, m 16 11.3 Net depth, 1.5 x base dia 24 16.95 Volume 1 cone cu. m 1608 667 Total volume of cones 1608 1334 E:\2MAIN\D68\68243A.DOC The advantage of the smaller volume becomes even more pronounced where 3 more cones are used.

It will thus be realized that the novel device of the present invention serves to allow the use of either a larger net with an equivalent size trawl or the use of an equivalent sized net with a smaller trawl.

To test the invention a three-cone prototype was constructed.

Experimentation was carried out on a 140 H.P. boat. The prototype was towed achieving the speed of 2 knots at 170 rpm. The net spread was measured and found to be 27 meters, while the same boat dragging a standard net of only 15 metres spread achieved 2 knots only at 2000 rpm.

The experiment was video-taped using an under-water recorder.

The invention will now be described further with reference to the accompanying drawings, which represent by example preferred embodiments of the invention. Structural details are shown only as far as necessary for a fundamental understanding thereof. The described examples, together with E:\2MAIN\D<58\68243A.DOC 123461/2 the drawings, will make apparent to those skilled in the art how further forms of the invention may be realized.

In the drawings: FIG. 1 is a S lD&perspective view of a preferred embodiment of a two-cone general trawl net assembly, according to the invention; FIG. 2 is a^ ^ perspective view of an embodiment configured for operation near the bottom of a body of water; FIG. 3 is a perspective view of a net assembly provided with cable anchor points; and FIG. 4 is a perspective view of a triple trawl net. tflCi.5 , 6 r7 provide a general description of the claimed novelty There is seen in FIG. 1 a two-cone fishing net assembly 10.

Assembly 10 is arranged to be drawn through cables 74, 76 by a powered vessel 12, for example a 140 H.P. trawler. The assembly 10 comprises two connected substantially conical nets 14, 16. The base 18, 20 of each conical net 14, 16 is open to allow the ingress of water and fish 22. The conical nets 14, 16 are interconnected at points 70, 72 at their bases 18, 20 and arranged so that in use the apexes 24, 26 of the cones substantially both face away from the direction of motion of vessel 12. 123461/2 - 7 - The cones 14, 16 are interconnected by centeralr anchor pointe in a manner ensuring that the two cones are aligned with each other horizontally and that the cone bases 18, 20 are maintained open at all times, including during dragging and turning.

For this purpose four cables 28, 30, 32, 34, all substantially horizontal, connect the cone outer edges 36, 38, 40, 41 to the central cone interconnection edges 70, 72. The cables 28, 30, 32, 34 prevent excessive cone flattening in operation.

With reference to the rest of the figures, similar reference numerals have been used to identify similar parts.

Referring now to FIG. 2, there is seen an assembly 42 similar to assembly 10 described with reference to FIG. 1.

However fishing net assembly 42 is arranged to operate substantially below the water surface 44 while maintaining spread.. This is achieved by adding otter doors 46, 47 to the assembly 42. An otter door is a device, commonly used in trawl fishing, which while being pulled forward, tends to move side way, thus forcing the trawl net to open. 123461/2 (20.09.00) 8 In the present embodiment the net mesh 48 is sized for the collection of shrimps and other shellfish, which are usually harvested from near the bottom 52 of body of water. The plurality of smaller conical nets 56, 58 have a much larger propotion of their opening 54 near the bottom 52 of the water than would be possible with a larg single conical net.

FIG. 3 illustrates a two cone fishing net assembly 60 further including six anchor points 36, 38, 40, 41, 70, 72 for cables. The anchor points 36-41 are located at each end of the said assembly, and two points 70, 72 in the center. The pair of centeral points 70, 72 are connected to other to other points 36-41 by cables 23, 30, 32, 34 as seen in fig. 1.

Seen in fig. 4 is a fishing net assembly 78 including three net cones 80,82,84. The total deployed length of assembly 78 exeeds 25 meters.

In the figure the net cones 80, 82, 84 are shown partially flattened,as this is the form often resulting during deployment.Centeral net 82 is inter¬ connected with other nets 80 and 84, at base points 69, 70, 71, 72 which arw connected to points 36, 38, 40, 41.

Otter doors 46, 47 are connected to points 36-41 as seen in fig. 1 and 2. 123461/3 (20.09.00) 9 Fig.5 shows standart trawl net deployment, where boat 2 drags a trawl net 3 by cables 4, 5.

Net 3 achieves its spread by use of otter doors (boards) 6, 7.

Fig.6 shows a double trawl net deployment as described in the claims. Nets 8, 9 replace net 3 of fig.5.

Other components in fig.6 are aimilar to tohse of fig.5.

In the present deployment, same spread is being achieved, as in fig. 5.

However, the total amount of webbing in nets 8, 9 is half the amount needed to construct net 3 of fig.5. Thus volume and resistance of the present deployment is reduced according to the same rattio.

Fig.7 shows a triple trawl net deployment.

Net 10 is constructed out of the difference in webbing amount of the nets in fig.5 and fig.6.

Spread of the deployment in fig.7 is larger by 1/3 than the spread shown in fig.5, which is the standart deployment. Resistance, however, is the same or even less than prior deployments. 123461/3 (20.09.01) 10 It will be noted that vertical cone flattening is advantageous in arranging that a large proportion of the net opening can operate near the sea or river bottom.

It will be understood that larger numbers of cone nets can be joined in horizontal series, the moderate total volume of such nets making possible a spread of up to 35-40 meters without causing fluid drag.

The scope of the described invention is intended to include all embodiments coming within the meaning of the following claims. The foregoing examples illustrate usefull forms of the invention, but are not to be considered as limiting its scope, as those skilled in the art will readily be aware that additional variants and modification of the invention can be formulated without departing from the meaning of the appended claims.

Claims (6)

123461/3 (20.09.00) 11 WE CLAIM:

1. A fishing trawl net assembly arranged to be drawn by a powered vessel, said assembly comprising a plurality of connected substantially conical nets, a base of each said conical net being open to allow ingress of water and fish, said conical nets being interconnected at said bases and arranged so that in use the apex of each said conical nets substantially faces away from the direction of motion of said vessel.

2. The fishing trawl net assembly as claimed in claim 1 wherein the nets are interconnected by means of riggs so as to maintain desired function.

3. The fishining trawl net assembly as claimed in claim 1 arranged to operate substantially below a water surface.

4. The fishing trawl net assembly as claimed in claim 1, wherein a mesh of the net is sized for a collection of shrimps and other shellfish. 123461/3 (20.09.00) 12

5. The fishing trawl net assembly as claimed in claim 1 further comprising at least six anchor points, four of said anchor points being located at each end and two anchor points being located at a center of said assembly.

6. The fishing trawl net assembly, substantially as hereinbefore described and with reference to the accompanying drawing.