Wood 120 – Lumber Volume

Wood 120 – Lumber Volume

Lab #1 - 2013

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2

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”

Robert Fürst – Wood 120

Log Scaling in Cubic

• Logs in BC are usually measure in cubic meters

• Smalian’s Formula is the standard used in BC

Robert Fürst – Wood 120

Smalian’s Formula

Ab

Au

h

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

Robert Fürst – Wood 120

Excel Example

sed 7.0 inches 17.8 cmled 9.0 inches 22.9 cmlength 16.0 feet 4.9 meters

Ab 0.2673 ft2 0.0248 m2

Au 0.4418 ft2 0.0410 m2

Vol 5.67 ft3 0.1606 m3

Imperial Metric

Log Volume Estimation using Smalian's Formula

Area (Ab or Au)=(d² x 3.14)/4

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Foot Board Measure

12 inches12

inch

es

1 inch

Board foot = 12 inches wide, 12 inches long, 1 inch thick

= 1/12 ft3

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• Largest sawmill production capacity600 MMfbm (Houston, BC)

• Average BC sawmill capacityapprox. 150-200 MMfbm

• Price of softwood lumber

$250-275/Mfbm

• Price of hardwood lumbere.g. sugar maple $4/board foot

Robert Fürst – Wood 120

Quick conversion factors

• Millimeters to Inches multiply by 0.03937• Inches to Millimeters multiply by 25.4• Meters to Feet multiply by 3,281• Feed to Meters multiply by 0.3048• Square Meters to Square feet multiply by 10.764• Square Feet to Square Meters multiply by 0.0929• Cubic Meters to Board Footage multiply by 423.79• Board footage to Cubic Meters multiply by 0.0023596

Robert Fürst – Wood 120

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 3.28112

= 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

50 55 60 65 70 75Recovery %

212

233

254

275

296

318

FBM/m3

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British Columbia Sawmill British Columbia Sawmill Lumber Recovery FactorsLumber Recovery Factors

200

220

240

260

280

300

320

1990 1992 1994 1996 1998 2000 2002 2004

Years

BC Mills +17%

Leading Mills

Ave

rag

e L

RF

(b

f/m

)

3

231

271

(BC MoF, 2005)(BC MoF, 2005)

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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)

14

Target ThicknessMinimum dimension required to achieve desired final size given unavoidable reductions in size during manufacture.

Robert Fürst – Wood 120

Fibre Recovery - Percentage

Finished lumber (kds4s)      47%Chips                                 34%Sawdust & chip fines           9%Shrinkage                            4%Shavings                              6%

Robert Fürst – Wood 120

Lab Assignment Sawing – LRF – Log Volume

Robert Fürst – Wood 120

Lab Tasks - Sawing

• Calculate the log volume of the sample log (m3)

• Make 2 horizontal reference cuts

#1 #2

Robert Fürst – Wood 120

Lab Task - Sawing

• Rotate log 90°, cut reference cut, saw boards

#3 #4

Robert Fürst – Wood 120

Lab Task - Sawing

• Cut the log into 2” thick boards

Robert Fürst – Wood 120

Lab Tasks - Sawing

• Rip each individual board to 4” wide

components

• 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 %

Wane

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: 28th November 2013• Group 2: 5th December 2013 • Please e-mail your report to Mr. Sheng Xie

E-Mail: xiesheng@gmail.com