WO2010036381A1

WO2010036381A1 - Lower cost, higher efficiency trawl construction

Info

Publication number: WO2010036381A1
Application number: PCT/US2009/005397
Authority: WO
Inventors: Sharif Adham Safwat
Original assignee: Hampidjan, Hf
Priority date: 2008-09-29
Filing date: 2009-09-29
Publication date: 2010-04-01

Abstract

A trawl (20, 20', 20") that includes riblines (76) that have a negative hang which may be formed as a sheath (106) that surrounds an inner core (104) of more elastic linear elements. Another aspect is a trawl (20, 20', 20") having corners (38) that includes both a highly elastic ribline (72) and a relatively inelastic stop line (76). A trawl (20, 20', 20") may include tension separator frontropes (156) coupled to netting panels (32, 24, 26) where the mid-portion (24) mates with the front-end (22) of the trawl (20, 20', 20"). Such a trawl (20, 20', 20") may also advantageously further include at least a pair of disconnected front part corners (192). Finally, the trawl may also advantageously further include a codend spreader and connector (162) located between the back-end (26) of the trawl and a codend or brailer bag (68).

Description

LOWER COST, HIGHER EFFICIENCY TRAWL CONSTRUCTION

Technical Field

The present disclosure relates generally to the technical field of midwater trawls and, more particularly, to midwater trawl apparatus and methods used for catching pelagic and semi- pelagic fish.

Background Art A conventional midwater trawl, including those used for catching Alaska Pollock, has a front-end that provides a mouth for the trawl and that includes wings that tend to herd fish toward the center of the trawl . The aft end of the trawl ^■ s front -end connects to a mid-portion of the trawl the aft end of which connects to a back-end of the trawl . A packer tube and/or codend or brailer bag connects to the aft end of the back-end and closes the end of the trawl furthest from the mouth provided by the front-end.

The front-end, mid-portion and back-end of a midwater trawl are made from netting having a mesh size which decreases progressively from the mouth at the trawl's front-end to the aft end of the trawl's back-end to which the packer tube and/or codend or brailer bag connects. As used herein the terms "codend" and "brailer bag" are used interchangeably for netting connected to the trawl's back-end that closes the end of the trawl and that amasses fish during trawling.

It is highly desirable to have as much volume as possible in the back-end of midwater trawls to increase fish flow and water velocity flow into the brailer bag or codend, while keeping open the mesh in the netting that forms the back-end of the trawl. Keeping open the mesh in netting forming the back-end of the trawl also reduces bycatch, unintended catching of marine organisms. Bycatch increases if the drag of conventional netting collapses the back-end of the trawl thereby drowning marine mammals and preventing smaller marine organisms from passing through the netting.

A midwater trawl's back-end is usually assembled from conventional machine-made knotted netting. When being towed through the water, conventional netting entrains a pressure wave in the water. The pressure wave created by the bulk of back-end's netting produces what is known colloquially as a bucket effect. This pressure wave produces competing forces which act on the netting both:

1. to keep the back-end of midwater trawls open thereby effectively operating analogously to a conventional sea anchor; and

2. to significantly reduce the trawl's volume due to tension in the trawl's mesh forward of the back-end caused by the netting's drag.

In view of the preceding considerations, it is clearly advantageous if netting throughout a trawl exhibits the lowest possible drag for specified strength. Fishing gear drag is a significant factor in overall efficacy of a fishing operation including a trawler's fuel consumption and how long it takes to fill the packer tube and/or codend or brailer bag.

Trawls having ropes and/or netting meshes that generate lift vectors mainly directed outward away from the center of a trawl are known to be self spreading. Self spreading trawls generally employ ropes such as that sold by Hampidjan USA, of Seattle, Washington and by Hampidjan HF of Iceland under the name Helix. This type of Helix rope has cambered sections disposed along its length. Mesh bars of a self spreading trawl formed by lengths of Helix rope locate the rope's cambered sections that are on the outside of the trawl aligned more along the trawl's longitudinal axis than are the cambered sections on the inside of the trawl. Self spreading trawls generally exhibit more drag than a comparable trawl made with conventional, round ropes and twines, but advantageously reduce bycatch.

Thus, it can be appreciated that a long felt need continues to exist in the industry for midwater trawls that are less expensive to manufacture and that exhibits less drag and catch fish species such as herring, capelin, blue whiting, red fish and pearlside well, i.e. exhibit higher efficiency, than trawls now being used for catching pelagic and semi -pelagic fish. As used herein the phrase "stretch measure" specifies a length measured from mid knot to mid knot of :

1. a single mesh of netting when the mesh is completely- closed by being pulled taught in the fore to aft direction perhaps under a specified tension; or

2. a series of connected mesh when all the mesh in the series are completely closed in the way described above for a single netting mesh.

As used herein the phrase "hang ratio" means a length of netting's mesh per length of line or rope to which the netting is secured.

Disclosure

An object of the present disclosure is to provide a midwater trawl construction that is cost effective to manufacture, and economical to use.

Yet another object of the present disclosure is to provide a midwater trawl that exhibits reduced drag, decreases fuel consumption while increasing operation and fishing efficiency. Briefly, in one aspect a trawl in accordance with the present disclosure includes riblines that have a negative hang. Another aspect of the present disclosure is a trawl ribline formed as a sheath that surrounds an inner core of more elastic linear elements. From front to back a midwater trawl usually includes:

1. a front-end providing at a front of the front-end a mouth for the trawl, the front -end including at least two (2) panels of netting with opposite lateral edges of each netting panel seamed to an opposite lateral edge of a different netting panel of the front-end along a corner of the trawl;

2. a mid-portion that at a front thereof mates with an aft end of the front -end, the mid-portion including at least two (2) panels of netting with opposite lateral edges of each netting panel seamed to an opposite lateral edge of a different netting panel of the mid-portion along a corner of the trawl; and

3. a backend that : - A - a. at a front thereof mates with an aft end of the mid-portion; and b. at an aft end, the backend is adapted for mating with a fish collecting device selected from a group consisting of: i. a codend; ii. a packer tube; and iii. a brailer bag.

Similar to the front -end and the mid-portion, the backend includes at least two (2) panels of netting with opposite lateral edges of each netting panel seamed to an opposite lateral edge of a different netting panel of the backend along a corner of the trawl .

In yet another aspect, a trawl in accordance with the present disclosure along at least one of the corners includes both a highly elastic ribline and a relatively inelastic stop line. Alternatively, a trawl in accordance with the present disclosure along at least one of the corners includes at least one ribline formed by a one piece line that includes a highly elastic inner core enclosed within a sheath that includes highly inelastic filaments. Lastly, a trawl in accordance with the present disclosure includes:

1. along at least one of the corners at least one ribline; and 2. tension separator frontropes coupled to netting panels of the mid-portion where the mid-portion mates with the front-end of the trawl.

In addition to the tension separator frontropes, the trawl may advantageously further include at least a pair of discon- nected front part corners that:

1. at an aft end each of the disconnected front part corners, respectively attach to separated corners of the trawl where the tension separator frontropes and the corners intersect; 2. extend forward within and surrounded by the front -end of the trawl disconnected from the netting panels of the front-end; and 3. at a forward end of each of the disconnected front part corners, respectively attach directly to separated trawl system components selected from a group consisting of: a. a forward points of mini-bridles located at the front of the trawl; b. towing warps ahead of a connection between the respective towing warps and separated trawl doors ; and c. the trawl doors.

Similar to the tension separator frontropes, the trawl may also advantageously further include a codend spreader and connector located between the back-end of the trawl and a codend or brailer bag. These and other features, objects and advantages will be understood or apparent to those of ordinary skill in the art from the following detailed description of the preferred embodiment as illustrated in the various drawing figures.

Brief Description of Drawings

FIG. 1 is a plan view depicting a trawl in accordance with the present disclosure at rest illustrating the trawl's front- end, mid portion, back-end and packer tube and/or codend;

FIG. IA is a plan view depicting the trawl of FIG. 1 with tension applied to the trawl's corners such as occurs during towing and fishing conditions;

FIG. 2 is a cross-sectional view depicting an alternative construction for inelastic stop lines and elastic riblines that may be used in corners of the trawl depicted in FIGs. 1 and IA; FIG. 3 is a schematic diagram depicting a construction for a corner of the trawl illustrated in FIGs. 1 and IA that is located in the back-end of the trawl;

FIG. 4 is a elevational view depicting a gore seam formed by gathering and lacing netting that is included in the trawl illustrated in FIGs. 1 and IA;

FIG. 5 is a perspective view depicting an alternative embodiment trawl in accordance with the present disclosure illustrating the trawl's front-end, mid portion, back-end, netting panels and corners ;

FIG. 6 is an elevational view of a codend spreader and connector adapted for use with the trawls depicted in FIGs. 1, IA and 5 ;

FIG. 6A is a plan view of the codend spreader taken along the line 6A- 6A in FIG. 6 ;

FIG. 6B is a elevational view of the codend spreader taken along the line 6B-6B in FIG. 6; and FIG. 7 is a plan view depicting an alternative embodiment trawl in accordance with the present disclosure.

Best Mode for Carrying Out the Disclosure

FIGs. 1 and IA are different illustrations of a midwater trawl in accordance with the present disclosure identified by the general reference character 20. FIG. 5 illustrates an alternative embodiment midwater trawl identified by the general reference character 20'. Those elements depicted in FIG. 5 that are common to the midwater trawl 20 illustrated in FIGs. 1 and IA carry the same reference numeral distinguished by a prime ("'") designation.

As is well known to those skilled in trawl fabrication and use, extending along the length of the trawl 20' illustrated in FIG. 5 from the front thereof to the back are a front-end 22 ' , a mid-portion 24' and a back-end 26' . Included in the trawl 20' are a top panel 32', a bottom panel 34' and two (2) side panels 36'. The side panels 36 respectively extend between the top panel 32 ' and the bottom panel 34 ' along corners 38' of the trawl 20' where the side panels 36' respectively seam to the top and bottom panels 32', 34 '. Frontropes 42', located at the leading edge of the panels, 32', 34' and 36', include a headline 44 ' , a footrope 46' and two (2) breastlines 48 ' respectively located at leading edges of the side panels 36' . As stated previously, netting meshes located in the front-end 22' of the trawl 20' are larger in mesh size than netting meshes located in the mid-portion 24 ' of the trawl 20'. Correspondingly, netting meshes of the mid-portion 24' are larger in size than netting meshes located in the back-end 26' of the trawl 20 ^■ .

It is extremely important to maintain the trawl 20, 20' of the present invention open and fishing during an entire tow. The reason is that should the trawl 20, 20' collapse, sometimes referred to as "closing, " the fish catching features of the trawl 20, 20' operate improperly and fish become inadvertently gilled and not caught, and more marine mammals may die. The collapse of a trawl 20, 20' frequently occurs in the back-end 26 in a manner that the trawler towing the trawl 20, 20 ' cannot easily or readily detect. Disclosed herein is an improved construction for the corners 38 of a trawl 20, 20'.

The top plan view of the trawl 20 illustrated in FIG. 1 depicts additional constructional characteristics and features of the corners 38 of the trawl 20 in greater detail than that provided by the illustration of the trawl 20' in FIG. 5. Preferably, all four (4) corners 38 of the trawl 20, i.e the corner 38 respectively between opposite lateral edges of the top panel 32 and the side panels 36 and between opposite lateral edges of the bottom panel 34 and the side panels 36, employ the characteristics and features disclosed herein.

Similar to the trawl 20' depicted in FIG. 5, the trawl 20 depicted in FIG. 1 includes a front-end 22, a mid-portion 24 and a back-end 26. For the trawl 20 depicted in FIG. 1, the front-end 22 extends from forward ends 52 of mini-bridles 54 rearward to a juncture 56 with the first row of netting meshes that are less than eight meters (8.0 m) long. The mid-portion 24 of the trawl 20 extends rearward from the first row of netting meshes that are less than eight meters (8.0 m) long through rows of netting meshes that are larger than six-hundred millimeters (600 mm) to and including a row of netting meshes that are six-hundred millimeters (600 mm) long. In the illustration of FIG. 1, the mid-portion 24 begins at the juncture 56 and extends rearward to a forward point 62 of back-end riblines 64. The back-end 26 of the trawl 20 extends from rows of netting meshes that are less than six-hundred millimeters (600 mm) long, i.e. the forward point 62 of the back-end riblines 64, rearward to a juncture 66 between the trawl 20 and a packer tube and/or codend 68.

The corners 38 of the front-end 22 of the trawl 20, the corners 38 of the mid-portion 24 and the corners 38 of the back-end 26 are formed differently, though there are important similarities. Specifically, corners 38 of the front-end 22 and mid-portion 24 of the trawl 20 are formed using elastic linear elements disposed alongside less elastic linear element where the less elastic linear elements are longer than the elastic linear elements. Specifically, corners 38 are formed using highly elastic riblines 72, highly elastic selvedge mesh 74, and relatively inelastic stop lines 76. For corners 38 of the front-end 22, when highly elastic selvedge mesh 74 are used in the front-end 22, the highly elastic riblines 72 may be omitted because the highly elastic selvedge mesh 74 can be arranged to provide sufficient strength equivalent to that of the highly elastic riblines 72. Eliminating the highly elastic riblines 72 in this way allows for reduced construction expense, some increase in opening of the trawl 20 and some drag reduction. For the purpose of this disclosure and claims herein, selvedges and/or selvedge mesh having strength equivalent to that of a ribline shall be understood to constitute or to be equivalent to a ribline.

Preferably, the highly elastic riblines 72 and the highly elastic selvedge mesh 74 are made from tightly braided high tenacity nylon, polyester, Danline or Kraftrope with minimal constructional elongation. However, other elastic materials may be used for the highly elastic riblines 72 and the highly elastic selvedge mesh 74 such,as pre-stretched and/or pre-heat- set version of the preceding materials. Preferably, the relatively inelastic stop lines 76 are made from braided High Molecular Weight Polyethylene (¹¹HMWPE") or Ultra High Molecular Weight Polyethylene ("UHMWPE") material, such as materials sold under the brand names Spectra and Dyneema . Analogous to the materials that are useful for making the highly elastic riblines 72 and the highly elastic selvedge mesh 74, other inelastic materials may be used for the relatively inelastic stop lines 76 such as pre-stretched and/or pre-heat-set version of the preceding materials.

While the same types of materials are used for the corners

38 of both the front-end 22 and the mid-portion 24, there exist differences between the constructions used for the corners 38 of the front-end 22 and used for the corners 38 of the mid-portion 24.

The first difference in construction used for the corners 38 of the front-end 22 and used for the corners 38 of the mid-portion 24 is the percentage of negative hang on the relatively inelastic stop lines 76. In the front-end 22 of the trawl 20, the percentage of negative hang on the relatively inelastic stop lines 76 at the corners 38 exceeds the percentage of negative hang on the relatively inelastic stop lines 76 at the corners 38 of the mid-portion 24. The amount of negative hang on the relatively inelastic stop lines 76 at corners 38 of the front-end 22 is preferably between two percent (2.0%) and fifteen percent (15%), i.e. the hang is -2% to -15%. Alternatively, the amount of negative hang on the relatively inelastic stop lines 76 at corners 38 of the mid-portion 24 is preferably between zero percent (0%) and three percent (3%), i.e. the hang is from 0% to -3%.

The construction used for the highly elastic riblines 72 at the corners 38 of the front-end 22 and the mid-portion 24 is a positive hang. The hang of these highly elastic riblines 72 is preferably set at a positive value such as positive five percent (5%) or positive three percent (3%) , depending upon the resistance to elongation of the material being used for the highly elastic riblines 72 in relation to a trawler's ability, during normal towing operations as contrasted with haul -back operations, to stretch the highly elastic riblines 72 to a hang percentage that causes the length of the highly elastic riblines 72 to match the length of the relatively inelastic stop lines 76. FIG. 1 illustrates the trawl 20 at rest, i.e. with the tension removed from the corners 38 to permit depicting differences between lengths of the highly elastic riblines 72 and highly elastic selvedge mesh 74 and the relatively inelastic stop lines 76. As mentioned previously, preferably the relatively inelastic stop lines 76 of the front-end 22 have a hang of from negative two percent (-2%) to negative fifteen percent (-15%) . That is, the relatively inelastic stop lines 76 are constructed and configured so as to be from two percent

(2%) to fifteen percent (15%) longer than the length when measured fore to aft of the stretch measure of netting meshes that are included in the front -end 22 of the trawl 20 and are juxtaposed with the relatively inelastic stop lines 76. A negative hang of two percent (2%) to seven percent (7%) is most generally applicable for the relatively inelastic stop lines 76. However, a negative hang of two percent (2%) to five percent (5%) for the relatively inelastic stop lines 76 of the front-end 22 is presently considered optimal depending upon: 1. elasticity differences of the highly elastic selvedge mesh 74 and/or highly elastic riblines 72 in relation to the relatively inelastic stop lines

76; as well as

2. the design and configuration of the geometrical arrangement of the meshes forming the front -end 22 of the trawl 20.

Fig. IA shows the trawl 20 with tension applied to the corners 38 such as occurs during normal towing and fishing operations. However, in reality the highly elastic riblines 72 and relatively inelastic stop lines 76 become so tightly pressed together when under high tension as to appear as one line. Consequently, to permit visualizing the highly elastic riblines 72 and the relatively inelastic stop lines 76 in the illustration of FIG. IA, the highly elastic riblines 72 and the relatively inelastic stop lines 76 are artificially displaced from one another to permit depicting lashings 82 that connect the relatively inelastic stop lines 76 to the highly elastic riblines 72 and also to the highly elastic selvedge mesh 74, as is preferably done at selvedge mesh points 84. The mini -bridles 54 are preferably formed of highly elastic braided lines. The mini-bridles 54 may also have a stop line attached to them at a negative five percent (5%) to negative twenty percent (20%) hang, i.e. -5% to -20% longer than the length of the selvedge mesh points 84.

In the illustrations of FIGs. 1 and IA, secondary- selvedges 92 traverse diagonally through the front -end 22 of the trawl 20, following a diagonal row of mesh bars from the juncture 56 between the front-end 22 and the mid-portion 24 forward to an intersection 94 with the headline 44 of the trawl 20.

FIG. 2 shows an alternative construction for the relative- Iy inelastic stop lines 76 and highly elastic riblines 72 described above with reference to FIGs. 1 and IA. Specifically, depicted in FIG. 2 is a one piece line 102 fabricated to exhibit negative hang that replaces the highly elastic riblines 72 and the relatively inelastic stop lines 76. The one piece line 102 is formed with an inner core 104 of highly elastic linear elements enclosed within less elastic linear elements that form a woven and/or braided sheath 106. The woven and/or braided sheath 106 is formed of highly inelastic filaments and bundles of filaments, including yarns and plaits, that are woven and/or braided together in a way that permits a relatively large amount of constructional elongation. Specifically, the woven and/or braided sheath 106 permits an amount of constructional elongation corresponding to the desired amount of negative hang of the relatively inelastic stop lines 76 provided in the description of FIGs. 1 and IA. The inner core 104 may be formed by bundled yarns 108 of high tenacity pre- stretched Kraftrope and/or Danline, and the woven and/or braided sheath 106 can be formed of plaits of Dyneema. To resist easily damaging the loosely woven and/or braided sheath 106 made from Dyneema, the one piece line 102 preferably includes a tightly wrapped woven coverbraid 112 of nylon enclosing the woven and/or braided sheath 106.

Construction of the corners 38 of the back-end 26 of the trawl 20 differs from the corners 38 both of the front-end 22 and of the mid-portion 24. In the back-end 26, where netting mesh sizes are 400 mm or larger, the relatively inelastic stop lines 76 are preferably hung at negative one percent (-1%) . As netting mesh size decreases, and more particularly as the corners 38 of the back-end 26 approach nearer and nearer to the juncture 66 of the trawl 20 with the packer tube and/or codend 68, relatively inelastic stop lines 76 of the back-end 26 are hung with a gradually increasing positive values. Thus, where netting mesh sizes are less than 200 mm and especially equal to or within 25% of the mesh size of netting used in the permanent fish retaining portion of the packer tube and/or codend 68, relatively inelastic stop lines 76 are hung at a positive value up to positive ten percent (10%) . The construction of the corners 38 of the back-end 26 of the trawl 20 further differs from the corners 38 both of the front -end 22 and the mid-portion 24 in the construction and use of gore seams. Properties of the gore seams are very important to the function of the corners 38 in the back-end 26 of the trawl 20.

Consider now the construction of corners 38 of the back-end 26 in relation to netting mesh 116 in the back-end 26 of the trawl 20 where the mesh size is from 100 mm to 200 mm, for example the corner 38 in the bottom panel 34 of the back-end 26 that is schematically illustrated in FIG. 3. The schematic diagram of the corner 38 appearing in FIG. 3 includes the relatively inelastic stop line 76, the highly elastic ribline 72 and a gore seam 122. Beneath the gore seam 122, FIG. 3 appears a row of netting mesh 116 that have been pulled taught in the fore to aft direction to measure, under a specified tension, the stretch measure length of the netting's meshes 116. FIG. 3 further schematically depicts binding together the relatively inelastic stop line 76, the highly elastic ribline 72, and the gore seam 122 with lashings 82. The stretch measure of the meshes 116 measured at hand tension or 5 kg establishes a length for zero percent (0%) hang. That is, stretch measure by definition equals a zero percent (0%) hang. The stretch measure is preferably taken at the center of the panel 22, 24 or 26 of the pertinent netting panel. The relatively inelastic stop line 76 is the next longest item illustrated in FIG. 3, and it has a hang in this instance of two percent (2%) . That is, the relatively inelastic stop line 76 has a length that is two percent (2%) shorter than the length of the stretch measure obtained for the meshes

116. The gore seam 122 is the next longest item having a length that is approximately two percent (2%) to ten percent

(10%) shorter than the length of the stretch measure obtained for the meshes 116 when both are measured at approximately 10 kg tension. The shortest item is the highly elastic ribline

72 that, in the instant example of FIG. 3, is a 24 mm to 40 mm diameter high tenacity polyester tightly braided rope of minimal constructional elongation. This particular highly elastic ribline 72 has a hang of five percent (5%) to ten percent (10%) depending upon the vessel's power. Danline or Kraftrope are also useful for the highly elastic ribline 72^' as are nylon ropes. Forming the gore seam 122 begins with bundling the meshes 116 as the gore seam 122 is formed of bundled meshes 116. Then, the highly elastic ribline 72 is connected to the gore seam 122, and finally the relatively inelastic stop line 76 is connected to the highly elastic ribline 72 by lashings 82.

Ideally, the highly elastic ribline 72 and the relatively inelastic stop line 76 are measured at a predetermined tension, and their hang accounted for in relation to always being measured at that tension.

In securing together the linear elements of varying lengths that form the corner 38 of the back-end 26, first the gore seam 122 and the highly elastic ribline 72 must be stretched until they reach the same length as that of the relatively inelastic stop line 76. Then the lines are marked relative to one another, relaxed, and lashed together. The highly elastic ribline 72 is secured immovably relative to the gore seam 122 by frequent lashings, say every 100 mm. The relatively inelastic stop line 76 can be secured to the highly elastic ribline 72 at one connection per distance corresponding to the bundles of netting knots that results from gathering together the mesh 116 when forming the gore seam 122. Referring now to FIG. 4, the gore seams 122 are preferably formed of bunched meshes 126 that are very tightly bound to one another with lacings 132 forming hitch knots 134, including full hitches and half hitches, so that the gore seams 122 assume an hour-glass shape 136 as shown in FIG. 4. The hitches preferably are situated aside the bundled knots 138 for each zone of knots in the netting (or aside the intersections in the case of knotless netting), and also between adjacent pairs of bundled knots 138, i.e. half way along the bundled netting mesh 116 as illustrated in FIG. 4 by a hitch-knot lacing 142.

For mesh sizes of 500 mm and smaller, each gore seam 122 preferably includes at least eleven (11) mesh 116 and their associated knots, at least fifteen (15) mesh 116 being more preferred, at least twenty (20) mesh 116 being highly preferred and with at least twenty-five (25) mesh 116 being most preferred. The number of meshes including within each gore seam 122, the diameter of the meshes 116, and lacing tightness establishes the hour-glass shape 136 shown in FIG. 4 which retains its shape despite applying a predetermined tension, for example 100 kg, to the gore seam 122. For mesh sizes of 200 mm and smaller, of 152 mm and smaller, and of 114 mm and smaller, it is extremely important that when measured under 25 Kg of tension, and preferably under 50 Kg of tension, and better yet under 100 Kg of tension, that the length of the gore seam 122 is 2% shorter than the stretch measure of the corresponding netting panel measured at its center, and is at least 1% or at least 0.5% shorter. Preferably yet, the length of the gore seam 122 is at least 3% shorter than the stretch measure of the corresponding netting panel measured at its center. Gores 122 having a between knot bunches diameter (i.e. midpoint along each mesh bar) exceeding 20 mm, exceeding 25 mm, and exceeding 30 mm when measured under 25 Kg of tension are preferred, and exceeding 40 mm diameter measured at such tension are yet more preferred.

The corners of codends, such as the four riblined codends standard in the Alaska Pollock fishery, are preferably formed in the same way as described herein for forming the corners 38 of the back-end 26, except that a very thick, very strong highly elastic ribline is used and put in at a hang of about positive fifteen (15%) , while the inelastic stop line has a positive hang of about from seven percent (7%) to ten percent

(10%) . Such a construction of corners forming the codend's corners ensures that the codend can remain open during fishing operations, while at the same time is able to be stretched during haulback so as to assume a smaller, and more manageable diameter than its larger diameter during towing. A codend fabricated in this way tends to remain open, permits discharge ramp functioning and, in general, answers a long felt need in the industry for a codend construction that fills up very easily yet assumes a small enough diameter to permit easy on-deck handling. Preferably, all riblines used in the trawl 20 or 20' that include splices, such as spliced eyes, have their eye splice braid zones pre-stretched prior to being incorporated into the trawl 20, 20' .

The alternative embodiment trawl 20' depicted in FIG. 5 advantageously reduces drag and manufacturing cost. As illustrated in FIG. 5, trawl 20' includes main panel tension separator frontropes 152 that divide the main panels of the trawl 20' into two portions, i.e. a forward portion and an aft portion. That is, dividing the panels 32 ', 34' and 36' of the trawl 20' into forward and aft portions that respectively correspond to the front-end 22 ' for the forward portion and to the combined mid-portion 24' and back-end 26' for the aft portion. Since the trawl 20' is a four sided trawl having four corners 38', the main netting panels of the trawl 20' are the top panel 32', bottom panel 34' and the side panels 36'. However, in general a trawl my have any number of sides, with two sides being considered the minimum number, i.e. a two panel trawl also known as a "two seam" trawl. A two panel trawl may have one panel much shorter than the other, and for such a trawl usually the bottom panel is much shorter than the top panel with the footrope positioned aft of the headrope .

As illustrated in FIG. 5, the tension separator frontropes 152 includes tension separator headline 154, tension separator footrope 156 and tension separator breastlines 158, each connecting directly to the respective corners 38' of the trawl 20'. The purpose of the tension separator frontropes 152 is to bear the tensions transmitted from netting portions aft of the tension separator frontropes 152 and transmit those tensions either entirely or mainly to those portions of corners 38' located in the front-end 22' of the trawl 20' . In this way the tension separator frontropes 152 either mainly or entirely separates netting meshes forming the front-end 22 ' of the trawl 20' from the tensions originating in netting forming both the mid-portion 24' and back-end 26' of the trawl 20'. Consequently, due to lesser tension in the front-end 22 ^■ of the trawl 20' the meshes forming the front-end 22' of the trawl 20' can have significantly reduced material bulk. Significantly reducing the material of the front-end 22' results at least in reduced manufacture cost, reduced drag and reduced fuel consumption, as well as facilitating opening and performance of the trawl 20 '.

Ideally, netting meshes forming the front-end 22' of the trawl 20' connect to the tension separator frontropes 152 so that under normal operating conditions tensions transmitted to the tension separator frontropes 152 from netting meshes located aft of the tension separator frontropes 152 are unable to elongate netting meshes in the front-end 22' to the point of breaking. Yet more preferably, netting meshes in the front-end 22' of the trawl 20' at the planned opening of the trawl are either slack or mainly slack in comparison to the tension usually present in netting meshes of the front-end 22' of a midwater trawl that, lacking the tension separator frontropes 152, connect directly to netting meshes in the mid-portion 24' and back-end 26' of the trawl 20'.

It is extremely important to connect the trawl 20, 20' to any packer tube and/or codend 68 at juncture 66, 66' in such a way that the packer tube and/or codend 68 always remains open. This is so whether the trawl of the present invention is connected to a standard four riblined Alaska Pollock codend, or to a non-riblined brailer bag type codend that is also used in fishing for pelagic and semi -pelagic fish. Otherwise, the passage of fish to the permanent fish retaining portions of the codend is inhibited, resulting in gilling of the Pollock, and poor catches. As trawlers shall not use a trawl that poorly catches the intended specie, e.g. Alaska Pollock, capelin, herring, blue whiting, mackeral, pearlside, etc., the construe- tion for a illustrated in Fig. 6, 6A and 6B is highly advantageous when used with the trawl 20, 20'.

FIG. 6 depicts a rectangularly or square shaped codend spreader and connector 162 that is useful for connecting the back-end 26, 26' of the four cornered trawl 20, 20' to the packer tube and/or codend 68, though circular shapes are also useful. The codend spreader and connector 162 may also be used for connecting:

1. packer tubes to codends,- and 2. codends to other portions of codends.

The codend spreader and connector 162 has four corners 164, each having a master link 166 respectively welded at each of the corners 164. As best illustrated in FIG. 6B, the master links 166 are constructed and configured to be adapted to receive shackles, Ghooks and the like that are attached to the aft end of each of the back-end riblines 64 at the juncture 66 the trawl 20, 20', and also to the forward end of each of four riblines of a packer tube and/or codend 68, or the like.

The codend spreader and connector 162 includes a codend top panel spreader bar 172, two codend side spreader bars 174 and a codend bottom panel spreader bar 176. The codend spreader and connector 162 is sized to match the planned opening of the codend to be used with the trawl 20, 20' . The codend top panel spreader bar 172 preferably has an I-beam construction as the codend top panel spreader bar 172 bears most of the constrictive forces applied to the codend in a midwater trawl. The spreader bars 172, 174 and 176 are all preferably formed of hardened steel, and are welded together at the corners 164. The leading and trailing edges and the general profile of the spreader bars 172, 174 and 176 is preferably as streamlined as practicable.

Floats, not illustrated in any of the FIGs., may be used advantageously for neutralizing the weight in water of the codend spreader and connector 162. Such floats may be connect- ed:

1. entirely to the codend ' s riblines in a usual way for floats attached thereto;

2. to the codend spreader and connector 162; or 3. divided between the codend's riblines and the codend spreader and connector 162.

The plan view of FIG. 6A depicts the codend top panel spreader bar 172 of the codend spreader and connector 162. The codend top panel spreader bar 172 is pierced by holes 178, as well as in the other spreader bars 174, 176, to which flymesh, sippers and/or other mesh can be sewn.

The elevational view of FIG. 6B depicts one of the codend side spreader bars 174 of the codend spreader and connector 162. As illustrated in FIG. 6b, the master links 166 have forward and aft eyes and/or other apertures 182, 184 adapted for receiving shackles, G-hooks or other connectors.

Using the codend spreader and connector 162 to connect a trawl 20, 20', or any trawl having corners formed with riblines, to a standard two or four riblined midwater mackeral or Alaska Pollock codend requires:

1. the aft end of each of the two or four back-end riblines 64 forming the four corners 38 of the back-end 26, 26' of the trawl 20, 20' attach to the forward eyes and/or other apertures 182; and

2. the forward ends of each of the two or four riblines forming the codend attach to the aft eyes and/or other apertures 184.

Then, the codend's flymesh are sewn into the holes 178 in such a way as to maintain horizontal stretch measure of the netting panels. Ideally, the number of holes 178 on the top, bottom and sides of the codend spreader and connector 162 matches the flymesh for the codend's top, bottom and side panels, respectively, while the width of the top, bottom and side spreader bars 172, 176 and 174 matches the planned dimensions of the codend so as to maintain maximal planned opening of the codend at its connection to the aft of the trawl 20, 20' . Upon retrieving the trawl 20, 20' and codend, the trawl 20, 20' is hauled up and wound upon a net drum of the trawler, not illus- trated in any of the FIGs., until the codend spreader and connector 162 arrives at the stern ramp, or otherwise is further hauled aboard inside a chute of the trawler, not illustrated in any of the FIGs. Then, either the codend spreader and connector 162 may be picked up with a picking boom and hook of the trawler, not illustrated in any of the FIGs., while the codend is strapped with another picking boom and hook and gillson line of the trawler, not illustrated in any of the FIGs. Then the codend is pulled upward and the tension on the trawl 20, 20 ' is relaxed thereby making it possible for the trawler's crew to easily disconnect the codend spreader and connector 162 from the codend as well as from the trawl 20, 20'. Alternatively, the codend spreader and connector 162 may be left in place attached to the back-end 26 of the trawl 20, 20' and to the codend while the codend is emptied and the trawl 20, 20' and codend reset.

Advantageously, the codend side spreader bars 174 may be hinged at their center so the centers of the codend side spreader bars 174 may fold inward toward each other, not illustrated in any of the FIGs. In this embodiment, the codend side spreader bars 174 are temporarily locked during setting out of the trawl 20, 20' , and after hauling back the trawl 20, 20' when the codend side spreader bars 174 reach the vessel unlocked and folded inward thus facilitate rolling up the codend spreader and connector 162 on a net drum.

A procedure similar to that described for attaching a trawl 20, 20' and codend to opposite sides of the codend spreader and connector 162 is used when using the codend spreader and connector 162 for connecting the trawl 20, 20", or any trawl having corners formed with riblines, to a brailer bag type codend that lacks riblines, including a brailer bag type codend having T90 mesh. However:

1. the entire codend spreader and connector 162 must be used; and

2. due to the absence of riblines in the brailer bag type codend, the step of connecting the forward ends of each of the codend ' s four riblines to the aft eyes and/or other apertures 184 is omitted. Rather, with a brailer bag type codend the aft eyes and/or other apertures 184 are unused, or used for a different purpose, such as connecting a safety line, while meshes and/or flymeshes of the brailer bag type codend are sewn to the holes 178, again in such a fashion as to maintain stretch measure of the brailer bag type codend. During haulback, disconnecting the codend spreader and connector 162 often proves unnecessary when pumping fish. Rather, the codend spreader and connector 162 can be immobilized or held by a pitching boom, hook or line .

In fact, it is highly preferred and highly advantageous to use the codend spreader and connector 162 for connecting any type of midwater trawl having riblines to brailer bag type codends having no riblines. Thus, the codend spreader and connector 162 answers a need long felt in the industry.

It is significant that when the trawl 20' depicted in FIG. 5 is used in conjunction with the codend spreader and connector 162 of the present invention, that the bulk and strength of the meshes forming the mid-portion 24 and also forming the back-end 26 of the trawl 20' can be much reduced, as the tensions of the codend couple directly to the corners 38 of the trawl 20' . Therefore, when the trawl 20' has both the tension separator frontropes 152 as well as the codend spreader and connector 162, the bulk and strength of the netting forming the mesh portions of the trawl 20' not including the packer tube and/or codend are reduced dramatically.

The plan view of FIG. 7 depicts an alternative embodiment of the four sided trawl 20, 20' . Those elements depicted in FIG. 7 that are common to the midwater trawl 20, 20' illustrated in FIGs. 1, IA and 5 carry the same reference numeral distinguished by a double prime (^»»») designation. The illustration of FIG. 7 depicts any one of four (4) identical panels 32", 34", 36" included in the four (4) sided trawl 20" so the trawl 20" has four symmetrical sides. FIG. 7 illustrates disconnected front part corners 192 that lack a fixed connection to netting included in the front -end 22" of the trawl 20", i.e. netting included in the top panel 32", bottom panel 34" and the side panels 36" of the front-end 22". For the trawl 20" depicted in FIG. 7, the disconnected front part corners 192 extend reward within the front-end 22" to the tension separator frontropes 152" at separated corners 38 of the trawl 20" where the tension separator frontropes 152" and the corners 38" intersect with netting of the front-end 22" surrounding and enveloping the disconnected front part corners 192. The forward end of each of the disconnected front part corners 192 may alternatively connect directly to: 1. a forward end of the mini -bridles 54";

2. towing warps 196 depending from the trawler, that is not illustrated in any of the FIGs., ahead of a connection between the towing warps 196 and trawl doors 198, only one of which appears in FIG. 7; or 3. may connect directly to the trawl doors 198.

Industrial Applicability

Collectively, when assembled for catching fish the towing warps 196, the trawl doors 198, the trawl 20, 20', 20" and the packer tube and/or codend 68 form a trawl system. While the corners 38, 38' and 38" and their construction have been disclosed in the context of the four (4) sided trawl 20, 20' and 20", the disclosures apply as well to any and all corners of any trawl that connect to and/or correspond to back-end riblines, and/or packer tube and/or codend riblines.

Although the present invention has been described in terms of the presently preferred embodiment, it is to be understood that such disclosure is purely illustrative and is not to be interpreted as limiting. Consequently, without departing from the spirit and scope of the disclosure, various alterations, modifications, and/or alternative applications of the disclosure will, no doubt, be suggested to those skilled in the art after having read the preceding disclosure. Accordingly, it is intended that the following claims be interpreted as encompass- ing all alterations, modifications, or alternative applications as fall within the true spirit and scope of the disclosure.

Claims

The ClaimsWhat is claimed is:

1. A trawl (20, 20', 20") comprising riblines (76) having a negative hang.

2. The trawl (20, 20', 20") of claim 1 wherein riblines (76) are formed as a sheath (106) of linear elements surrounding a more elastic inner core (104) of linear elements.

3. The trawl (20, 20', 20") of claim 1 further comprising riblines (72) having a positive hang.

4. The trawl (20, 20', 20") of claim 3 wherein the riblines (72) having positive hang are formed from a material having a greater elasticity than material forming the riblines

(76) having a negative hang.

5. The trawl (20, 20', 20") of any one of claims 1 through 4 wherein the riblines connect to a codend spreader and connector (162) .

6. The trawl (20, 20', 20") of any one of claims 1 through 4 further comprises a codend (68) , and a portion of the trawl having riblines includes the codend (68) .

7. The trawl (20, 20', 20") of claim 3 further comprises a codend (68), and the codend (68) includes riblines.

8. A trawl (20, 20', 20") that from front to back thereof comprises: a. a front-end (22) providing at a front of said front-end (22) a mouth for the trawl (20, 20', 20"), the front-end (22) including at least two (2) panels

(32, 34, 36) of netting, opposite lateral edges of each of the netting panels (32, 34, 36) being seamed to an opposite lateral edge of a different netting panel of the front-end (22) along a corner (38) of the trawl (20, 20', 20"); b. a mid-portion (24) that at a front thereof mates with an aft end of said front-end (22) , the mid-portion (24) including at least two (2) panels

(32, 34, 36) of netting, opposite lateral edges of each of the netting panels (32, 34, 36) being seamed to an opposite lateral edge of a different netting panel of the mid-portion (24) along a corner (38) of the trawl (20, 20', 20"); and c. a backend (26) that: i . at a front thereof mates with an aft end of said mid-portion (24) ; and ii. at an aft end of said backend (26) is adapted for mating with a fish collecting device selected from a group consisting of: A. a codend (68) ;

B . a packer tube ; and

C. a brailer bag, the backend (26) including at least two (2) panels (32, 34, 36) of netting, opposite lateral edges of each of the netting panels (32, 34, 36) being seamed to an opposite lateral edge of a different netting panel of the backend (26) along a corner (38) of the trawl (20, 20', 20"), the trawl (20, 20', 20") further comprising along at least one of the corners (38) of the trawl (20, 20', 20") a highly elastic ribline (72) and a relatively inelastic stop line (76) .

9. A trawl (20, 20', 20") that from front to back thereof comprises: a. a front -end (22) providing at a front of said front-end (22) a mouth for the trawl (20, 20', 20"), the front-end (22) including at least two (2) panels

(32, 34, 36) of netting, opposite lateral edges of each of the netting panels (32, 34, 36) being seamed to an opposite lateral edge of a different netting panel of the front -end (22) along a corner (38) of the trawl (20, 20', 20"); b. a mid-portion (24) that at a front thereof mates with an aft end of said front-end (22) , the mid-portion (24) including at least two (2) panels

(32, 34, 36) of netting, opposite lateral edges of each of the netting panels (32, 34, 36) being seamed to an opposite lateral edge of a different netting panel of the mid-portion (24) along a corner (38) of the trawl (20, 20 ', 20"); and c. a backend (26) that: i . at a front thereof mates with an aft end of said mid-portion (24) ; and ii. at an aft end of said backend (26) is adapted for mating with a fish collecting device selected from a group consisting of: A. a codend (68) ;

B . a packer tube ; and

C. a brailer bag, the backend (26) including at least two (2) panels (32, 34, 36) of netting, opposite lateral edges of each of the netting panels (32, 34, 36) being seamed to an opposite lateral edge of a different netting panel of the backend (26) along a corner (38) of the trawl (20, 20' , 20") , the trawl (20, 20', 20") further comprising along at least one of the corners (38) of the trawl (20, 20 ', 20") at least one ribline (72, 76) formed by a one piece line (102) that includes a highly elastic inner core (104) enclosed within a sheath (106) that includes highly inelastic filaments.

10. A trawl (20, 20', 20") that from front to back thereof comprises: a. a front-end (22) providing at a front of said front-end (22) a mouth for the trawl (20, 20', 20"), the front -end (22) including at least two (2) panels

B. a packer tube; and

C. a brailer bag, the backend (26) including at least two (2) panels (32, 34, 36) of netting, opposite lateral edges of each of the netting panels (32, 34, 36) being seamed to an opposite lateral edge of a different netting panel of the backend (26) along a corner (38) of the trawl (20, 20 ' , 20") , the trawl (20, 20', 20") further comprising: d. along at least one of the corners (38) of the trawl

(20, 20', 20") at least one ribline (72, 76); and e. tension separator frontropes (152) coupled to the netting panels (32, 34, 36) of the mid-portion (24) of the trawl (20, 20', 20") where the mid-portion (24) mates with the front-end (22) of the trawl (20,

20 ' , 20") .

11. The trawl (20, 20', 20") of claim 10 wherein the trawl (20, 20', 20") further comprises at least a pair of disconnected front part corners (192) that: i. at an aft end each of the disconnected front part corners (192) , respectively attach to separated corners (38) of the trawl (20, 20',

20") where the tension separator frontropes

(152) and the corners (38) intersect; ii. extend forward within and surrounded by the front-end (22) of the trawl (20, 20', 20") disconnected from the netting panels (32, 34, 36) of the front-end (22) ; and iii. at a forward end of each of the disconnected front part corners (192) , respectively attach directly to separated trawl system components selected from a group consisting of: A. a forward points of mini-bridles (54) located at the front of the trawl (20, 20', 20"); B. towing warps (196) ahead of a connection between the respective towing warps (196) and separated trawl doors (198) ; and C. the trawl doors (198) .