MSC 132/134 Fishing Gear Technology I

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MSC 132/134Fishing Gear Technology I II

• Calculating and Cutting Netting Tapers

Excerpts from Calculations for Fishing Gear
Designs, A.L. Fridman, Fishing News Books Ltd.,
Surrey, England. 1986 FAO Catalogue of Small
Scale Fishing Gear, Edited by C. Nedelec, Fishing
News Books Ltd. Whitefriars Press Ltd.,
London, England. 1975 Fishermans Workbook,
Compiled by J. Prado, Fishing News Books, Oxford,
England. 1990 How to Make Set Nets, John
Garner, Fishing News Books Ltd., Surrey, England.
1986.
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Machine Made Netting
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Cutting and Shaping Netting

1. The number of meshes at the start of the cut.
2. The number of meshes required at the end of the
   cut.
3. The length or depth in meshes of the section to
   be cut.

All Points or Siders E2 Depth (90º) Normal
Direction
All Meshes or Transverse E1 Length (0º) Base
of right angle
All Bars 45 degree angle
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Resultant Angles for Net Tapers
Assuming Meshes Are Hung At 71
E1 Value of 50
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Common Cutting Rates Taper Ratios
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Cuts Netting Example
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Body TapersGuidelines and Formula

1. You can only cut or calculate a cut by evaluating
   one side of the intended shape or piece of
   netting .
2. Always establish which way your E values are
   oriented.
3. The body taper is only used if the material to be
   cut is less than the depth of the netting.

2 x Cut Depth - Cut
Bars Points
Body Taper

Bottom - Top
Cut
2
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Body Taper Calculations
180 meshes
E1
2 Cut 2 x 20 40 4
bars Depth Cut 30 20 10 1
points
30 mesh
140 meshes
2 x Cut Depth - Cut
Bars Points
Body Taper

Bottom - Top
Cut
2
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Body TapersCalculating the Cut

1. For calculation purposes when applying the cut
   formula, always assume the bottom of the netting
   piece is represented by the larger mesh count.
2. When using the cut formula - if only one side of
   the netting piece will be cut, do not divide by 2.

Bottom - Top
Cut
2
180 meshes
CUT
CUT
30 meshes
180 140 40 20 2 2
E1
140 meshes
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Body Taper Cuts

• When using the cut formula - if only one side of
  the netting piece will be cut, do not divide by 2.

140 meshes
60 mesh
E1
Cut 180 140 40 40
180 meshes
2 Cut 2 x 40 80 8
bars Depth Cut 60 40 20 2
points
2 x Cut Depth - Cut
Bars Points
Body Taper

Bottom - Top
Cut
2
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Body Taper Cuts
140 meshes

• The body taper is only used if the material to be
  cut is less than the depth of the netting.

30 mesh
E1
Cut 180 140 40 40
180 meshes
2 Cut 2 x 40 80 8
bars Depth Cut 30 40 -10 -1
points
2 x Cut Depth - Cut
Bars Points
Body Taper

Bottom - Top
Cut
2
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3P2B
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Body Tapers Calculations
3P2B
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Body Tapers Calculations
200 M
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Body Tapers Calculations
Body Taper 2 Cut Depth Cut
Bars Points

200 M
Cut Top Bottom 2 340 100 2
120 Body Taper 2 x 120 200 120 240
Bars 80 Points 3
Bars 1 Point
Body Taper 3 Bars 1 Point however, even
tapers are easier and neater to sew. A 6 Bar to
2 Point Body Taper (4B1P, 2B1P) is the same as a
3Bar to 1Point taper.
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Body Taper Examples
3 Bars 1 Point
2 Bars 1 Point
4 Bars 1 Point
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Jib TapersGuidelines and Formula

1. You can only cut or calculate a cut by evaluating
   one side of the intended shape or piece of
   netting .
2. Always establish which way your E values are
   oriented.
3. The jib taper is only used if the material to be
   cut is greater than the depth of the netting.
4. Length replaces the cut on jib tapers.

(2 x Depth) - 2 Length -Depth 1
Bars Meshes
Jib Taper

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Jib Tapers Calculations
The base length of the right triangle represents
the cut length.
20 P
E1
38 Meshes
(2 x 20) 2 38 2 bars 38 20
1 19 1 mesh

(2 x Depth) - 2 Length -Depth 1
Bars Meshes
Jib Taper

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Jib Tapers Calculations
(2 x Depth) - 2 Length -Depth 1
Jib Taper
Bars Mesh

(2 x 36.5) 2 73 2 71 73 36.5
1 36.5 1 37.5

1.89 Bars 2 1 Mesh 1

Tapers do not always work out perfectly. Your
critical thinking skills are essential to
properly apply various tapers and/or cutting
rates.
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All Bar TapersGuidelines and Formula

1. You can only cut or calculate a cut by evaluating
   one side of the intended shape or piece of
   netting .
2. Always establish which way your E values are
   oriented.
3. If the cut or length is equal to the depth of
   the netting you would have an all bar (AB)
   taper.
4. If statement 3 is true there are no calculations
   necessary.

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Tapers Calculations
Prove the Taper which is indicated on the
circled panel shown in the trawl plans (A15) to
the right.
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31M
35M
AB
31M
7P2B
62M
4M
2 Cut Depth Cut
Body Taper
Cut Top Bottom 66 62 4
2 x 4 31 4
8 Bars 27 Pts.
2 Bars 6.75 Pts.
2 Bars 7 Points
Body Taper

• Keys to Finding and/or Proving the Taper
• You can only cut and/or calculate a cut by
  evaluating one side of the intended shape or
  piece of netting at a time.
• An All Bar (AB) taper will yield a 45 degree
  angle, which means the Cut is equal to the
  Depth of the netting.

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Taper Examples
Cutting Rate 1N 2B (1 Point 2 Bars)
Cutting Rate 1T 2B (1 Mesh 2 Bars)
Cutting Rate 1N 2T (1 Point 2 Meshes)
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Drop Tapers
5 Meshes to 7 Meshes or 1 1 1 1 1
2 1 2
Drop Loops Added
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Identify the Tapers Shown Below
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CUT LOSS