Materials - woods Flashcards
What are the general properties of hardwoods?
-deciduous
-slow growing
-harder and stronger than softwoods
-close grain structure
-generally more expensive
What are the general properties of softwoods?
-coniferous
-generally quicker growing
-needle like leaves
-not as durable
Why are softwoods considered more sustainable?
Because of their fast growth rate.
Is oak softwood or hardwood?
Hardwood
Is mahogany softwood or hardwood?
Hardwood
Is beech softwood or hardwood?
Hardwood
Is balsa hardwood or softwood?
Hardwood
Is teak hardwood or softwood?
Hardwood
Is pine hardwood or softwood?
Softwood
Is cedar softwood or hardwood?
Softwood
Is redwood a hardwood or softwood?
Softwood
What are the advantages of oak?
Quite strong
Tough
Attractive grain pattern
Hard
Large supply
What are the disadvantages of oak?
Blights easily
Very heavy
Difficult to work with powertools
Uses of oak
Indoor and outdoor furniture
Structural timber for buildings
Flooring
Advantages of beech
Very hard
Water resistant
Non toxic
Durable
Straight even close grain
Disadvantages of beech
The colour changes over time
Heavy
Loses its durability
Very hard and heavy
Uses of beech
Furniture
Toys
Tool handles
Advantages of mahogany
Hard
Rot resistant
Straight grain
Strong
Tough
Disadvantages of mahogany
Poor workability
Dark colour shows dirt
Expensive
Very slow growing
Unstable
Uses of mahogany
Veneers, furniture, floorboards
Advantages of balsa
Lightweight
Buoyant
Natural insulator
Great strength to weight ratio
Disadvantages of balsa
Highly flammable
Not waterproof
Weak
High import costs
Not resistant to moisture or attack
Uses of balsa
Model bridge tests and buildings
Model aircraft
Advantages of teak
Strong
Ease of workability
Attractive grain
Very durable
Resists warping
Disadvantages of teak
Heavy, does not float in water
Oily nature makes it difficult to glue well.
Uses of teak
Outdoor furniture
Boat building
Exterior construction
Advantages of redwood
Lightweight
Good strength to weight ratio
Resistant to shrinking
Easy to cut and shape due to softness
Disadvantages of redwood
Rots if not treated
Warps if gets wet
Coarse texture
It needs a lot of maintenance
Prone to denting due to softness
Has knots
Uses of redwood
Furniture
Constructional members
Veneers
Good for decking due to straight grain
Advantages of cedar
Hard
Durable
Resistant to rot
Low density
High quality finish
Straight grain
Disadvantages of cedar
Susceptible to insect attack
Easily damaged
Uses of cedar
Roof tiles
Cladding
Ship building
Outdoor carving
Advantages of pine
Relatively straight grain
Easy to work
Quite high strength to weight ratio
Disadvantages of pine
Very knotty which makes it difficult to work
Not durable without treatments
Uses of pine
Construction
Roof joists
Floorboards and furniture
What are the two ways of drying timber?
Air drying
Kiln drying
What is air drying?
The planks are stacked outside with wooden spacers between them to allow air flow around the timber
Moisture is evaporated and the timber is dried out.
Disadvantages of air drying.
It is a very slow method - 1 inch thickness of timber takes around a year
Moisture content cannot be controlled as circulating air varies on time of year and weather
What is kiln drying?
The timber is mounted on a trolley and wheeled into a fully enclosed kiln with steam being fed into it.
Steam drives out the moisture
Advantages of kiln drying.
Atmosphere and temperature can be controlled
Moisture can be reduced to around 8% - suitable for furniture
Quick process
Disadvantages of kiln drying
Less environmentally friendly as is powered by fossil fuels.
Quite expensive
What is shrinkage?
If not seasoned correctly, newly felled timber will dry out in and uncontrolled way and then warp, twist and cup/bow.
What are the two main methods of converting timber?
Through and through sawn
Quarter sawn
Disadvantages of quarter sawn over through and through sawn.
More expensive
More wastage
Advantages of quarter sawn over through and through sawn.
More decorative
Less prone to cup or distort.
