Timber Flashcards
What are softwoods and some of their uses/advantages?
Generall evergreen tree species
Used for general structural purposes
They are easy to work with, cheap and fast-growing
What are hardwoods and some of their uses?
Mainly deciduous tree species
Used for exposed structural elements such as marine (harbour) works
In order out from the centre of a log, name the timber parts
Pith, Heart Wood, Sap Wood, Growth Layer, Inner Bark, Outer Bark
What shape are wood cells, typically?
Hexagonal
What range of diameters do wood cells typically have?
Fractions of a millimetre
Which wood cells are thin/thick-walled and why?
Thin: Storage & Conduction - to allow the largest possible amount of water, glucose etc. to pas into the cell
Thick: Support - to create a greater strength
What is a shake in wood and what are 3 types?
A point in the wood where there is a naturally occurring split
Types: Star -Cracks propagating radially toward the centre, Cup - Cracks along the annual rings, Radial - Cracks along the wood grain
What is a wood knot?
A point where the wood has grown up around an old branch causing a dense region in the wood with perpendicular grain
What is the difference in the reaction of deciduous and coniferous wood to wind loading?
Deciduous: Reaction wood is high in cellulose and forms at the side of the trunk on which the wind is blowing - strongest in tension
Coniferous: Reaction wood is rich in lignin and forms opposite the wind - strongest in compression
What is one of the most useful ways to divide a log into planks and why?
Radial Sawing as it keeps the most uniformity in the wood grain and hence the properties of the plank are much more predictable
In which grain direction is timber strongest?
Parallel to the grain
What is seasoning?
The process of removing moisture or sap from freshly cut timber is known as seasoning of timber.
What is the fibre saturation point?
The point at which all free water has been removed from the wood, approximately 27% of the total water should remain
What are the two most common methods of reaching the fibre saturation point?
Air - leaving the timber in a sun & wind-sheltered, well-ventilated area, can take 2-3 months to reach fsp
Kiln - Placing the timber in a heated, enclosed space to evaporate out the water, takes 4-5 days on average
What can sometimes result from seasoning?
Drying of wood reduces density and hence can cause shrinkage in the wood. This shrinkage can result in the timber planks curling
