Volume Determination

Definitions

Log = 8 or more feet long (usually 16 feet)

Bolt or Stick = less than 8 feet long

Scaling = the process of estimating or measuring wood volume

Board Foot

How many board feet in a cubic foot?

Board Foot Anomaly

1 board foot equals 144 in2 1 cubic foot equals 12 board feet However, if timber is scaled in cubic feet

–12 board foot per cubic foot isn’t realized in lumber This is due to…

Kerf Slabs Trim waste

Kerf – wood lost as sawdust

Why 12 board foot of lumber isn’t actually what a cubic foot of wood yields

Bored Feet

Cubic Feet

Cord

Assume 80 cubic feet of solid wood due to air space

Roughly Half a Cord of Firewood

Stem Form

Girard Form Class

Ratio of the inside-bark diameter at the top of the first 16 ft. log to dbh. Defines the rate of taper in a tree.

Stump height (1 ft.) and a trim allowance (0.3 ft.) are factored in, making the upper measurement at 17.3 ft. above ground.

Example: diameter inside bark at 17.3 feet: 14.3 inches dbh: 17.8 inches Girard Form Class: (14.3 / 17.8) = 0.803, or 80 percent

drawback: getting the inside-bark diameter at 17.3 feet. Can measure bark thickness, double it and subtract from DOB at 17.3’

Girard Form Class

Diameter inside bark (DIB) @ 17.3 feet Divided by Diameter Breast Height (DBH) (outside bark @ 4.5 feet) times 100

DIBtop

------- X 100 = FC

DBH

Extrapolate Top Diameter Given a Bark thickness, DBH and FC,

you can calculate Diameter Outside Bark @17.3 feet.

FC/100 = DIB/DBH DIB + 2XBark = DOB

If bark = .5”, DBH = 20”, and FC = 80 DOBtop = 17

Common Local Form Classes

Historic Local Form Classes

Appalachian

Softwoods:

White PineFC=79HemlockFC=78SprucesFC=82CypressFC=78

Hardwoods:

White OakFC=78Red oaksFC=78Yellow Poplar

FC=78Cherry

FC=82BasswoodFC=80Walnut

FC=78Beech

FC=84Maples

FC=79Birches

FC=78Upland ashes

FC=82Red & black gumFC=78HickoriesFC=78Cottonwood & willow FC=78Other hardwoodsFC=78

Central States

Softwoods:

White PineFC=80HemlockFC=78SprucesFC=78

Hardwoods:

White OakFC=78Red oaksFC=78Yellow Poplar

FC=78Cherry

FC=82BasswoodFC=78Walnut

FC=78Beech

FC=82Maples

FC=79Birches

FC=78Upland ashes

FC=82Red & black gumFC=80HickoriesFC=78Cottonwood & willow FC=78Other hardwoodsFC=78

Factors affecting tree volume

Geometric forms of portions of tree

Newton’s Formula: V = h/6(Ab + 4Am + Au)

Standing Tree Volume Formulas

Tree Volume Tables – Doyle (FC=78)Dbh(inches)

Number of 16-Foot Logs

1/2 1 1-1/2 2 2-1/2 3 3-1/2 4

Board Feet

12 20 30 40 50 60      

14 30 50 70 80 90 100    

16 40 70 100 120 40 160 180 190

18 60 100 130 160 200 220 40 160

20 80 130 180 220 260 300 320 360

22 100 170 230 280 340 380 420 460

24 130 220 290 360 430 490 540 600

26 160 260 360 440 520 590 660 740

28 190 320 430 520 620 710 800 880

30 230 380 510 630 740 840 940 1,040

32 270 440 590 730 860 990 1,120 1,220

34 300 510 680 850 1,000 1,140 1,300 1,440

36 350 580 780 970 1,140 1,310 1,480 1,640

38 390 660 880 1,100 1,290 1,480 1,680 1,860

40 430 740 990 1,230 1,450 1,660 1,880 2,080

Basically used by everyone except the US Government

Tree Volume Tables – International (FC=78)

Dbh(inches)

Number of 16-Foot Logs

1/2 1 1-1/2 2 2-1/2 3 3-1/2 4

Board Feet

12 30 60 80 100 120      

14 40 80 110 140 160 180    

16 60 100 150 180 210 250 280 310

18 70 140 190 240 280 320 360 400

20 90 170 240 300 350 400 450 500

22 110 210 290 360 430 490 560 610

24 130 250 350 430 510 590 660 740

26 160 300 410 510 600 700 790 880

28 190 350 480 600 700 810 920 1,020

30 220 410 550 690 810 930 1,060 1,180

32 260 470 640 790 940 1,080 1,220 1,360

34 290 530 730 900 1,060 1,220 1,380 1,540

36 330 600 820 1,010 1,200 1,380 1,560 1,740

38 370 670 910 1,130 1,340 1,540 1,740 1,940

40 420 740 1,010 1,250 1,480 1,700 1,920 2,160

Change the form class a little…

Rule of Thumb: Change of one form class = ~3% volume change

Derivation of Merchantable tree volume

Refer to previous slide

See how form class defines the volume estimates for upper logs

Tree Volume Tables - Scribner

Dbh(inches)

Number of 16-Foot Logs

1/2 1 1-1/2 2 2-1/2 3 3-1/2 4

Board Feet

12 28 48 66 78 89  100  108  

14 40 70 96 116 141 160  170  178

16 54 93 129 158 191 224 248 263

18 72 122 168 207 248 292 325 355

20 90 156 212 262 317 366 415 450

22 111 194 262 328 392 450 510 560

24 137 236 319 400 470 550 620 690

26 165 281 381 480 565 650 740 820

28 195 331 450 560 670 760 860 960

30 227 383 520 650 770 890 1,000 1,110

32 260 440 600 740 890 1,020 1,150 1,280

34 294 500 680 840 1,010 1,160 1,300 1,460

36 330 565 770 960 1,140 1,310 1,480 1,650

38 365 630 860 1,070 1,270 1,470 1,660 1,840

40 405 700 950 1,180 1,400 1,630 1,850 2,050

Contrasting Tree Scaling Rules

Scaling Timber by Weight

Sometimes trees are sold by weight instead of volume. Certain species, uses, and regions specifically.

Weights are subject to influence by multiple factors. Some of these include species, logging practices (how long it stays in the field after felling), season, climatic conditions, growth conditions, age, live/dead, etc.

Example – salvage cuts, ‘fire break’ cuts, clear cuts, where all trees are to be removed regardless. Saves time/money – don’t have to scale trees before cut.

Development of Weight Factors

When selling by weight, a weight to gross cubic volume factor must be determined.

Weight factors must be specific to species or species groups.

At least 10 observations with < 15% sampling error at the 95% confidence level.

Traditional Log Scaling

Historical information (species and product of load, gross cubic volumes, net load weights) from traditionally scaled logs

Xylodensimeter

the mean of at least 3 heartwood cores are taken at DBH, must be analyzed before losing moisture

Chunk Scaling

<8’ pieces volume calculated with Smalian’s formula and weight recorded to develop factor, chunks summed for each tree

Large Chunk Scaling – 1st piece is stump to DBH, other are 8’ pieces, whole tree volume and weight used for factor