Log and Lumber Volumes
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Transcript Log and Lumber Volumes
Wood 120 – Lumber Volume
Lab #1 - 2011
1
Lumber volume
• In sawmilling, lumber is most often
measured by the “board foot” or “fbm”
(Foot Board Measure).
1fbm = 1 foot x 1 foot x 1 inch
A thousand fbm is written “Mfbm”
A million fbm is written as “MMfbm”
2
Log Scaling in Cubic
• Logs in BC are usually measure in cubic
meters
• Smalian’s Formula is the standard used in
BC
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Au
Smalian’s Formula
Vol = h/2 (Ab + Au)
Where:
H = Height
Ab = cross section area at base
Au = cross section are at top
Area (Ab or Au)=(d² x 3.14)/4
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h
Ab
Excel Example
Log Volume Estimation using Smalian's Formula
sed
led
length
Imperial
7.0 inches
9.0 inches
16.0 feet
Metric
17.8 cm
22.9 cm
4.9 meters
Ab
Au
0.2673 ft
0.4418 ft2
2
0.0248 m
0.0410 m 2
2
Vol
5.67 ft3
0.1606 m 3
Area (Ab or Au)=(d² x 3.14)/4
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Foot Board Measure
12 inches
1 inch
Board foot = 12 inches wide, 12 inches long, 1 inch thick
= 1/12 ft3
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• Largest sawmill production capacity
600 MMfbm (Houston, BC)
• Average BC sawmill capacity
approx. 150-200 MMfbm
• Price of softwood lumber
$250-275/Mfbm
• Price of hardwood lumber
e.g. sugar maple $4/board foot
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Quick conversion factors
•
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Millimeters to Inches
Inches to Millimeters
Meters to Feet
Feed to Meters
Square Meters to Square feet
Square Feet to Square Meters
Cubic Meters to Board Footage
Board footage to Cubic Meters
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multiply by 0.03937
multiply by 25.4
multiply by 3,281
multiply by 0.3048
multiply by 10.764
multiply by 0.0929
multiply by 423.79
multiply by 0.0023596
Volume of lumber - Conversion
• When calculating board footage from metric sizes, it is
necessary to convert the metric size to imperial measure
before you begin the calculation
• Example: 10 pieces - 27mm thick - 105mm wide - 3 meter
long
• 1 mm = 0.039937 in, ; 1 meter = 3.281 ft.
10 pieces x 27 x 0.03937 x 105 x 0.03937 x 3 x 3.281
12
= 36 board feet
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Lumber Recovery Factor (LRF)
• Definition: LRF is how many board feet of
green/rough sawn lumber are produced out of
one cubic meter of wood.
• The units of LRF are board feet per cubic meter.
LRF typically ranges between 200 to 300 board
feet per cubic meter.
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Lumber Recovery Factor (LRF)
LRF depends on:
Size of logs entering the mill
Quality of log – defects, grade
Equipment used in a mill
318
296
275
254
FBM/m3
233
212
Recovery % 50 55 60 65 70 75
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3
Average LRF (bf/m )
British Columbia Sawmill
Lumber Recovery Factors
320
Leading Mills
300
271
280
260
240
231
BC Mills +17%
220
200
1990
1992
1994
1996
1998
2000
2002
2004
Years
(BC MoF,12
2005)
Standard Thicknesses
Nominal size (in inches)
2
4
6
8
10
1.5
3.5
5.5
7.25
9.25
Actual size (in inches)
13
Target Thickness
Minimum dimension required to achieve desired final size given
unavoidable reductions in size during manufacture.
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Fibre Recovery - Percentage
Finished lumber (kds4s)
Chips
Sawdust & chip fines
Shrinkage
Shavings
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47%
34%
9%
4%
6%
Lab Assignment
Sawing – LRF – Log Volume
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Lab Tasks - Sawing
• Calculate the log volume of the sample log (m3)
• Make 2 horizontal reference cuts
#1
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#2
Lab Task - Sawing
• Rotate log 90°, cut reference cut, saw boards
#3
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#4
Lab Task - Sawing
• Cut the log into 2” thick boards
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Lab Tasks - Sawing
• Rip each individual board to 4” wide
components
Wane
• Grade each board (No wane, no loose knots, no end splits
longer than 2”, no center board)
• Calculate the volume (in bf) of the 2/4 material recovered
• Calculate the LRF in %
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Document your findings of the lab
• Write a brief report describing all of your findings
of the lab and explain what caused the fairly low
LRF. Please be specific!
• Submit all of your calculations as required
• Due date:
• Group 1: 1st December 2011
• Group 2: 8th December 2011
• Please e-mail your report to Max Cosen
E-Mail: [email protected]
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