ENCYCLOPEDIA OF WOOD

FROM LOG TO LUMBER

B

etween the standing tree and the boards you pick off the rack at the lumberyard stands a complex process that requires many people to apply enor­mous skill at every step. Undetected defects in the standing tree, damage
caused during felling, poor judgment in bucking or inattentive sawing at the mill can sabotage the value of a tree and raise the sawmill’s—and the wood­buying consumer’s—costs. Although power saws have replaced muscle-driven
pit saws in the forest and at the mill, and cuts are now guided by laser beams and computer technology instead of chalk lines, no replacement has been devised for the practiced eye of an experienced lumberman.

A tractor-like skidder hauls a hitch of logs from the forest.

 

A logger (left) makes his undercut in a mighty Douglas-fir tree in the rainforests of British Columbia, Canada. Felling these behemoths was once the work of two men pushing and pulling a huge felling saw; today, a chain saw reduces felling to a quick one-man job.

 

FROM LOG TO LUMBER

FROM LOG TO LUMBER

A hydraulic log loader dispenses its contents onto a truck.

 

Selecting the trees

A tree’s journey to the lumberyard begins in the woods, when a forester or timber cruiser evaluates the trees for cutting. Not all cut trees will be earmarked for the saw mill; some will be used for pulp or firewood. These lower-grade trees are deliberately harvested to give the residual stock better access to nutrients and more room to grow, thus increasing the tim­ber stand’s value. The very best trees will be reserved for veneer.

Since most of the highest-grade lum­ber will come from the area just under the bark, the forester must be able to detect at a glance clues that betray defects
in this area. Knots, for example, can be particularly troublesome, depending on where they are located. In the bot­tom part of the tree, where they are usu­ally indicated by a slight disfiguration of the bark, knots may be so deeply over­grown that they will not affect the value of the outer wood. But further up, where they are typically indicated by concen­tric circles or even bumps in the bark, knots pose more serious problems in terms of quality.

The ability to distinguish between dif­ferent types of fungi is another impor­tant skill in tree evaluation. All fungi cause some damage, but certain species
are rapacious: In beech and hard maple, for example, a single body of false tinder fungus on the outside of a tree may signal the presence of a 12- to 14-foot-long column of decay within. If the decay were confined to the center of the tree, this would be less of a problem, but many fungi infest the most valuable outer wood. Any scarring of the bark is thus suspicious, since even the tiniest opening makes a tree susceptible to fungal infection.

Bird damage—specifically peckholes made by the yellow-bellied sapsucker— also affects a tree’s commercial value. Unlike its woodpecker cousins, which
eat wood-boring insects that infest dead wood, the yellow-bellied sapsucker feasts on the sap, wood cells, and inner bark of live trees. Persistent feeding results in long streaks of stain that effectively ren­der the wood worthless.

Felling and bucking

Trees are cut with three passes of a chain saw. The first two cuts remove a wedge about one-third of the diameter of the tree, facing the intended direction of fall. The tree is felled by the third cut, or backcut, made opposite to and a few inches above the wedge. As the tree falls, its direction is controlled by a “hinge”
of wood between the wedge and back - cut. Expert fellers consider many factors before making the cuts—the condition of the felling site, wind direction, the lean of the tree, and the presence of dead branches in adjacent trees, aptly called “widowmakers.”

Once the limbs have been removed, the tree is skidded to a staging area, or landing, where it is bucked into logs. To ensure that the wood is cut to the high­est possible grade, the bucker—like the forester or tree cruiser beforehand—has to “read” the tree for signs of defects before setting to work. Bulges in the bark indicate knots that are close to the sur­
face; large-diameter rotting branches point to decay within the tree trunk. While the optimal length for hardwood logs is 16 feet (8 feet for veneer-quality logs), cutting logs to this length is not always possible. Sometimes the bucker cuts 8-foot and 12-foot logs to avoid defects that would render a larger log worthless.

Transporting the logs

In some parts of North America, espe­cially the Pacific Northwest where trees are exceptionally large, bucking is done at the felling site before the logs are trans­ported to a central yard. Steeply sloping

Although a variety of methods have been used to move logs to the lumber mill, from river runs to draft horses, trucking remains the most common method of transport in North America.

FROM LOG TO LUMBER

 

The narrow kerf of a band saw produces less waste than a circular saw. Here, a worker at a Vermont mill removes a 38-foot-long band saw blade for sharpening.

 

FROM LOG TO LUMBER

terrain may require the logs to be gath­ered in from the forest floor using a series of cables. One such system is known as high-lead logging. Two main cables— one called a haulback and the other a mainline—are rigged to the top of a tall mast. Several other cables, called chok­ers, dangle from the mainline. Trees are felled so they land with their butt sec­tions pointing uphill; crewmen wrap each choker around the butt section of a bucked-up log, signal the head opera­tor, and the logs are reeled up the hill to the central pile, usually located next to a lumber road. When the logs have been detached, the haulback cable is used to pull the mainline and its chokers for another load. No matter how they are moved from the felling site or when they
are bucked, logs are loaded onto trucks with a hydraulic grapple hook for the trip to the sawmill.

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ENCYCLOPEDIA OF WOOD

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