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### Transcript of MSC 134 Fishing Gear Technology .2015-12-03 · MSC 132/134 Fishing Gear Technology I & II...

• MSC 132/134

Fishing Gear Technology I & II

Calculating and Cutting Netting TapersExcerpts 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.

• 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 Meshes or Transverse

E1 = Length (0)

Base of right angle

All Points or Siders

E2 = Depth (90)

Normal Direction

All Bars

45 degree angle

• Resultant Angles for Net Tapers

Assuming Meshes Are Hung At 71% E1 Value of 50%

• Common Cutting Rates & Taper Ratios

• Cuts: Netting Example

• Body Tapers

Guidelines and Formula1. 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.

Body Taper =2 x Cut

Depth - Cut=

Bars

Points

Cut = Bottom - Top2

• Body Taper: Calculations

Body Taper =2 x Cut

Depth - Cut=

Bars

Points

Cut = Bottom - Top2

180 meshes

140 meshes

30 mesh

2 Cut = 2 x 20 = 40 = 4 bars

Depth Cut 30 20 10 1 points

E1

• Body Tapers

Calculating 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.

Cut =Bottom - Top

2 180 meshes

140 meshes

30

meshes

E1CUT CUT

180 140 = 40 = 202 2

• Body Taper: Cuts

Body Taper =2 x Cut

Depth - Cut=

Bars

Points

Cut = Bottom - Top2

2 Cut = 2 x 40 = 80 = 8 bars

Depth Cut 60 40 20 2 points

E1

180 meshes

140 meshes

60 mesh

Cut = 180 140 = 40 = 40

When using the cut formula - if

only one side of the netting piece

will be cut, do not divide by 2.

• Body Taper: Cuts

Body Taper =2 x Cut

Depth - Cut=

Bars

Points

Cut = Bottom - Top2

2 Cut = 2 x 40 = 80 = 8 bars

Depth Cut 30 40 -10 -1 points

E1

180 meshes

140 meshes

30 mesh The body taper is only used if

the material to be cut is less

than the depth of the netting.

Cut = 180 140 = 40 = 40

• Body Tapers: Calculations

• Body Tapers: Calculations

200 M

• Body Tapers: Calculations

200 M

Body Taper = 2 Cut

Depth Cut

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.

=Bars

Points

• Body Taper Examples

3 Bars

1 Point

2 Bars

1 Point 4 Bars

1 Point

• Jib Tapers

Guidelines and Formula1. 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.

Jib Taper = (2 x Depth) - 2Length -Depth + 1

Bars

Meshes=

• Jib Tapers: Calculations

Jib Taper = (2 x Depth) - 2Length -Depth + 1

Bars

Meshes=

20 P

38 Meshes

E1

The base length of the right triangle represents the cut length.

(2 x 20) 2 38 2 bars

38 20 + 1 19 1 mesh= =

• Jib Tapers: Calculations

Tapers do not always work out perfectly. Your critical thinking skills are

essential to properly apply various tapers and/or cutting rates.

(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

= =

=

• All Bar Tapers

Guidelines and Formula1. 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.

• Prove the Taper which is

indicated on the circled

panel shown in the trawl

plans (A15) to the right.

Tapers: Calculations

• 31M

35M

62M

4M

31M

2 Cut

Depth Cut

2 x 4

31 4

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.

Cut = Top Bottom = 66 62 = 4Body Taper =

Body Taper =8 Bars

27 Pts.

2 Bars

6.75 Pts.

2 Bars

7 Points= = =

• 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)

• Drop Tapers

5 Meshes to 7 Meshes

or

1 1 1 1

1 2 1 2