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
Cord Assume 80 cubic feet of solid wood due to air space
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’
Historic Local Form Classes Appalachian Central States Softwoods: White Pine FC=80Hemlock FC=78Spruces FC=78 Hardwoods: White Oak FC=78Red oaks FC=78Yellow Poplar FC=78Cherry FC=82Basswood FC=78Walnut FC=78Beech FC=82Maples FC=79Birches FC=78Upland ashes FC=82Red & black gum FC=80Hickories FC=78Cottonwood & willow FC=78Other hardwoods FC=78 Softwoods: • White Pine FC=79Hemlock FC=78Spruces FC=82Cypress FC=78 Hardwoods: • White Oak FC=78Red oaks FC=78Yellow Poplar FC=78Cherry FC=82Basswood FC=80Walnut FC=78Beech FC=84Maples FC=79Birches FC=78Upland ashes FC=82Red & black gum FC=78Hickories FC=78Cottonwood & willow FC=78Other hardwoods FC=78
Geometric forms of portions of tree Newton’s Formula: V = h/6(Ab + 4Am + Au)
Tree Volume Tables – Doyle (FC=78) Basically used by everyone except the US Government
Change the form class a little… Rule of Thumb: Change of one form class = ~3% volume change
Derivation of Merchantable tree volume See how form class defines the volume estimates for upper logs Refer to previous slide
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