Lab #1 - 2011
1

• 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

• Logs in BC are usually measure in cubic meters
• Smalian’s Formula is the standard used in
BC
Robert Fürst – Wood 120

Vol = h/2 (Ab + Au)
Where:
H = Height
Ab = cross section area at base
Au = cross section are at top
Area (A b or A u
)=(d² x 3.14)/4
Robert Fürst – Wood 120 h
A u
A b

Log Volume Estimation using Smalian's Formula sed led length
Ab
Au
Imperial
7.0 inches
9.0 inches
16.0 feet
0.2673 ft
2
0.4418 ft
2
Metric
17.8 cm
22.9 cm
4.9 meters
0.0248 m
2
0.0410 m
2
Vol 5.67 ft
3
0.1606 m
3
Area (Ab or Au)=(d² x 3.14)/4
Robert Fürst – Wood 120

12 inches
1 inch
Board foot = 12 inches wide, 12 inches long, 1 inch thick
= 1/12 ft 3
6

• 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
7

• 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 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
Robert Fürst – Wood
120

• 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
Robert Fürst – Wood
120

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.
10

Lumber Recovery Factor (LRF)
LRF depends on:
Size of logs entering the mill
Quality of log – defects, grade
Equipment used in a mill
FBM/m 3
212
233
254
275
296
318
Recovery % 50 55 60 65 70 75
11

British Columbia Sawmill
Lumber Recovery Factors
320
300
280
260
240
220
200
231
Leading Mills
271
BC Mills +17%
1990 1992 1994 1996 1998 2000 2002 2004
Years

Nominal size (in inches)
2 4 6
1.5
3.5
Actual size (in inches)
5.5
8
7.25
10
9.25
13

Minimum dimension required to achieve desired final size given unavoidable reductions in size during manufacture.
14

Finished lumber (kds4s) 47%
Chips
Sawdust & chip fines
34%
9%
Shrinkage
Shavings
4%
6%
Robert Fürst – Wood 120

Sawing – LRF – Log Volume
Robert Fürst – Wood
120

• Calculate the log volume of the sample log (m3)
• Make 2 horizontal reference cuts
#1
Robert Fürst – Wood 120
#2

• Rotate log 90°, cut reference cut, saw boards
#4
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#3

• Cut the log into 2” thick boards
Robert Fürst – Wood 120

• 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 %
Robert Fürst – Wood 120

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: mclosen@interchange.ubc.ca
Robert Fürst – Wood
120