Forest Engineering

It is a fibrous substance that composes the trunk and the branches of a tree that lies between the pith and the bark; high demand in almost all types of construction.

Wood

It is the term applied to wood after it has been sawed or sliced into boards, planks, timber, etc.

Lumber

It is the term applied to unplaned or undressed limber. In short, lumber with rough surfaces.

Rough Lumber

These are dressed lumber wherein the number connotes the smooth sides. For instance, S2s means lumber having two smooth sides and S4s with four sides.

S2s and S4s

It is a kind of rough lumber cut tangent to the annual rings running through the full length of the log containing at least one flat surface.

slab

It is a planed lumber having at least one smooth side.

surface or dressed lumber

It is a piece of lumber five inches (5”) or larger in its smallest dimension.

timber

It is a wide piece of lumber from four to five inches thick (4”-5”).

plank

It is a piece of lumber less than four centimeters (4 cm) thick with at least ten centimeters wide (10 cm).

board

It is a thick piece of lumber.

flitch

When the annual rings are small, the grain or marking which separates the adjacent rings is said to be fine grained. When large, it is called Coarse Grained.

fine grained

It is a term used when the direction of the fibers are nearly parallel with the side and edges of the board.

straight grained

It is lumber taken from a crooked tree.

crooked or cross grained

Wood that are used in building constructions are those which grows larger by addition of a layer on the outer surface each year

exogens

These are those outwards growing trees preferred for lumbering.

exogenous

These are those trees that grows from the inside. These kind of trees as a soft center core and are not preferred for lumbering.

indigenous

comes from gymnosperms—typically conifers—and lacks vessel elements (pores). Instead, they have tracheids and resin canals, contributing to their relatively uniform grain and lighter weight.

softwood

originates from angiosperms—flowering deciduous trees—and features a more complex cellular structure with vessels, fibers, and rays, resulting in denser, often more durable timber.

hardwood

classification of wood with respect to grain:

(a) straight (b) cross (c) fine (d) coarse

classification of wood with respect to the nature of surface when sawed :

(a) plain (b) grained (c) figured or marked

It occurs at the starting point of a limb or branch of the tree

knots

These are radical cracks in wood originating from the heart of the logs. Commonly found in old trees

heart shakes

These are cracks or breaks across the annual rings of the wood during its growth caused by excessive bending of the tree due to strong winds.

wind shakes or cup shakes

These are composed of several heart shakes radiating from the center of the log in a star-like manner.

star shakes

It is caused by fungi in a seasoned lumber due to the presence of moisture

dry rot

It takes place sometime in the growth of the tree caused by water saturation.

wet rot

Defects in wood due to deterioration:

(a) dry rot (b) wet rot

Defects in wood due to abnormal growth:

(a) heart shakes (b) wind or cup shakes (c) star shakes (d) knots

It is considered as one of the best method used in seasoning of wood although the period involved in relatively longer.

Natural Sunlight or Air-seasoning Process

It is a process where lumbers are stacked in a drying kiln and then exposed to steam and hot air. Under this method, lumber undergoes a quick drying process.

artificial seasoning

Seasoning of lumber:

(a) natural sunlight or air-seasoning (b) artificial seasoning

Artificial drying methods:

(a) by forced air drying (b) by kiln drying (c) by radio frequency dielectric drying

Common Causes of Decay in Wood:

(a) alternate moisture and dryness (b) fungi or molds (c) insects and worms (d) heat and confined air

"Process of Preserving Wood: The wood is coated with preservatives applied as paint

to penetrate the fibers of the wood."

external process

"Process of Preserving Wood: A chemical compound is impregnated at a prescribed

pressure to permeate the wood thoroughly."

internal process

is the unit of measure used in computing the volume of lumber.

board foot

Light in weight and strong. Thickness available from 1/8 3/4 in.; standard length and width are 8 ft x 4 ft, respectively.

veneer and plywood

These are pressed wood made from wood chips exploded into fibers under high-pressured steam.

hardboard

Manufactured from wood chips, curls, fibers, flakes, strands, shaving, etc. bound together and pressed into sheets and other molded shapes; formed by hot press process with adhesive.

particle board

is the moisture content below which the physical and mechanical properties of wood begin to change. It is usually taken as 30% moisture content on oven-dry basis.

fiber saturation point

it occurs when the wood loses its moisture. With respect to shrinkage characteristics,wood is anisotropic

shrinkage

Wood shrinks ______ in the direction of the growthrings (tangential)

most

is a measure of the rate of heat flow through one unit thickness of a materialsubjected to temperature gradient.

thermal conductivity

it is the uniqueness of the mechanical properties n the direction of the three mutually perpendicular axes: longitudinal, tangential, and radial.

orthotropicity

it implies that deformations produced by low stress are completely recoverable after loadsare removed.

elasticity

the ratio of traverse strain to axial strain

Poission's ratio

It is defined as the ability of a member to sustain stress without failure.

strength

It is the resistance to denting and wear.

hardness

it is the resistance to deflection and bending when loaded.

stiffness

It is the resistance to shock loading.

toughness

is the twisting, bending or bowingdistortions shown by some woods. It was greatly affected by themethod of sawing and curing.

warping

It is the ease in sawing, shaping and nailing. It is moreevident in soft, low-density woods than for hardwoods, but usuallythey cannot be given a high polish

workability

Resistance of woods to decay caused by extremeenvironmental conditions and termites is a good criteria of the strength of wood.

natural decay resistance

Hardwoods:

narra, maple, oak, mahogany, acacia, yakal, rosewood, teak

Softwoods:

pine, ash, cedar, birch, fir, spruce, redwood

is necessary to enable the wood to dry quickly enough to avoid decay and insect damage and to permit the preservative to penetrate satisfactorily

peeling