MSC 134 Fishing Gear Technology IIcfcc.edu/blogs/srowe/files/2015/07/Calculating-Cutting... ·...
Transcript of MSC 134 Fishing Gear Technology IIcfcc.edu/blogs/srowe/files/2015/07/Calculating-Cutting... ·...
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
Fisherman’s 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 (0º)
Base of right angle
All Points or “Siders”
E2 = Depth (90º)
Normal Direction
All Bars
45 degree angle
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
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
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) - 2
Length -Depth + 1
Bars
Meshes=
Jib Tapers: Calculations
Jib Taper = (2 x Depth) - 2
Length -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)