Timber and Wood-based Products

Comprehensive practice flashcards covering vocabulary from the timber and wood-based products lecture, including tree structure, defects, seasoning, and preservation methods.

Timber

Wood that is suitable for building or engineering purposes, specifically applied to trees measuring not less than $0.6\,m$ in girth.

Standing timber

The timber available in a living tree.

Green timber

Freshly felled tree which has not lost its moisture or still contains free water in its cells.

Converted timber

Timber that has been sawn into various market sizes such as beams, battens, and planks.

Clear timber

Timber that is free from defects and blemishes such as stains.

Exogenous trees

Trees that grow outwards by forming successive annual rings on the outside under the bark; they provide timber used for engineering purposes.

Endogenous trees

Trees that grow inwards or endwards, such as Bamboos and Palms, which are usually too flexible for most engineering works.

Conifers

Evergreen trees with needle-pointed leaves that yield soft woods, are generally light in weight, resinous, and show distinct annual rings.

Deciduous trees

Broad-leaf trees that shed leaves in autumn and yield hardwoods that are close-grained, strong, heavy, and durable.

Pith

The innermost central portion of a tree, consisting of cellular tissues, usually about $12.5\,mm$ in diameter.

Heartwood

The inner annual rings surrounding the pith that are compact, strong, durable, and dark in colour; it provides the best timber for engineering.

Sapwood

The outer annual rings (alburnum) between heartwood and the cambium layer that carries sap and is more liable to decay or insect attack.

Cambium layer

A thin layer below the bark responsible for the circumferential growth of the tree; if removed, the tree dies.

Annual rings

Concentric circles of cellular tissue and woody fibre formed annually, used to indicate the age of a tree in temperate and tropical climates.

Medullary rays

Thin radial fibres extending from pith to cambium layer that store and conduct food material radially through the interior of the tree.

Girdling

A process of rounding the butt end of hardwood trees $2$ to $3$ years before felling to prevent sap formation and assist moisture evaporation.

Heartshakes

Splits or cracks widest at the centre of the tree and diminishing toward the outside, often caused by shrinkage of heartwood.

Star shakes

Radial splits or cracks widest at the circumference and diminishing toward the centre, mostly confined to sapwood.

Cupshakes

Defects formed by the rupture of tissues in a circular direction along the annual rings.

Rind galls

Abnormal curved swellings formed on a tree body caused by layers growing over wounds left by improperly cut branches.

Upsets

Deformation of fibres due to crushing caused by unskilful felling or violent winds.

Knots

The roots of small branches embedded in the tree that disturb wood homogeneity and reduce structural strength.

Seasoning

The process of removing moisture or sap from freshly felled timber under controlled conditions to reduce shrinking and warping.

Casehardening

A seasoning defect where the outer wood layers compress and harden while the inner portion remains in tension due to rapid drying.

Dry rot

Decomposition of felled timber by fungi into a dry powdery condition, occurring in poorly ventilated and warm areas.

Wet rot

Decomposition of timber tissue caused by dampness and alternate wetting and drying, not caused by fungal attack.

Ascue

A water-borne preservative powder composed of $1$ part arsenic pentoxide, $3$ parts hydrated copper sulphate, and $4$ parts sodium or potassium dichromate.

Creosoting

A preservation method where creosote oil is pumped into wood at $9\,bar$ pressure and $50\,^{\circ}C$ to prevent rot and termite attack.

Full cell process

Also known as the Bethel process, it uses an initial vacuum to expel air from wood before injecting preservatives under pressure.

Rueping process

An empty cell pressure treatment that uses initial air pressure to ensure desired absorption using less preservative.

Veneers

Thin sheets of superior quality wood, varying in thickness from $0.4\,mm$ to $6\,mm$, used for plywood and aircraft construction.

Plywood

A wood product made by cementing together an odd number of veneers (usually $3$ to $9$) with grains crossing each other.

Lamin board

A board with a core made of strips not exceeding $7\,mm$ in thickness glued face-to-face between outer veneers.

Block board

A board with a core of timber blocks up to $25\,mm$ in width cemented edge-to-edge between outer plies.

Batten board

A board having a core made of strips of wood usually $80\,mm$ wide glued between two or more outer veneers.

Fibre boards

Rigid boards manufactured from exploded wood or vegetable fibres subjected to heat and high hydraulic pressure.

Density of Deodar

The average weight of this soft wood is $5450\,N/m^3$ at $12$ percent moisture content.