Timbers Flashcards
Properties of softwood
- they mainly grow in cooler climates
- they are cone baring - therefore coniferous
- they have a looser grain structures
- they are often used as a building material
- usually softer and easier to work with
- they grow tall and straight - makes it easier for the manufacturer to cut long straight planks of wood
- they are evergreen meaning that they don’t loose their leafs in the winter
- they grow faster so therefore are cheaper
Properties of hardwood
- most hardwood trees are deciduous which loose their leaves in the winter
- tend to have a tighter grain structure
- they can be very expensive as they take a long time to grow
- they are usually quite hard
- there are evergreen hardwood trees that are found in tropical or sub-tropical countries such as South America
- they are broad leaf trees it’s seeds are enclosed in the fruit that the tree produces
- they generally grow in temperate climates
- around 100 years to grow fully
Properties of manufacturing board
- boards are available in many thicknesses
- boards are inexpensive so are often used instead of real woods
- they have been developed mainly for industrial production as they can be made in very large sheets of consistent quality
What are manufacturing boards and how are they made?
Manufacturing boards are timber sheets which are produced by gluing wood layers or wood fibres together
What are manufactured boards mainly made out of ?
Manufactured boards are mainly made out of waste wood
What’s a veneer ?
A veneer is a thin layer of real wood that is usually placed over manufacturing boards to improve their appearance or properties
Name some softwoods
Larch
Pine
Redwood
Spruce
Cedar
Douglas fir
Name some hardwoods
Oak
Ash
Beech
Balsa
Birch
Mahogany
Teak
Name some manufactured boards
Plywood
Marine plywood
Aeroply
Flexible plywood
Chipboard
Medium density fibreboard (MDF)
Veneers and melamine formaldehyde laminates
Name the performance characteristics of woods
- Grain pattern
- Grain direction
- Surface defects
- Warpage
- Shrinkage
- Splitting
- Joining
- Forming
- Steam bending
- Laminating
- Machining qualities
- Resistance to decay
- Moisture resistance
- Toxicity
Name the stock forms of timber
- rough sawn ( not smooth )
- lots of different sizes, planks and strips
- PSE ( planed square edge ) smooth all round
- PAR ( planed all round ) all the sides and edges are planed square, straight and level, leaving a smooth finish and ready to use
- natural timber
- manufactured boards
- mouldings - skirting boards, frames
- veneers - thin cuts of wood glued onto other materials
What happens if wood rots in landfill or is burned?
It releases greenhouse gases which contribute to climate change
What do trees do to carbon ?
Trees act as ‘carbon sinks’ that absorb the gases
Approximately 25% of the fresh weight of timber is carbon
What does using recycled timber products do ?
Using recycled timber products reduces deforestation and retains the locked-in carbon
What is seasoning
Seasoning is the process of removing excess moisture from freshly cut trees
What are the 2 types of seasoning ?
- Natural seasoning ( air seasoning )
- kiln seasoning
What are the advantages / disadvantages of natural seasoning ?
Advantages:
- cheap
- Some say the timber is stronger than kiln seasoned
Disadvantages:
- Very slow ( year per inch thickness )
- Bugs and fungus survive
- Water content hard to control accurately
- Ends of planks can split
Advantages and Disadvantages of kiln seasoning
Advantages:
- Accurate water content achieved
- 12% or lower moisture content achievable
- Kills bugs and fungus
- Fast
Disadvantages:
- Expensive
What is Splitting ( Timber defect ) ?
Where does it occur? What can you do stop/help it ?
- Usually occurs at the end of a plank
- Ends are cut off to remove splits
- Generally an unavoidable problem
- Painting the ends of planks can help slow down the drying of the ends
What are knots (timber defect) ?
Knots are where a branch was attached to a tree
Live knots are okay and can be decorative
Dead knots need to be avoided
What is Dry Rot ( timber defect )
What is it caused by ?
- Serious problem caused by incorrect seasoning or poor building maintenance
- Dry rot is caused by timber being over 20% moisture content and not ventilated
What is Woodworm ? And what is a sign of woodworm ?
The common furniture beetle lays eggs on timber
The larvae eat the wood for a year and then emerge as adult beetles
‘Frass’ or wood dust is a sure sign of woodworm
Name some physical characteristics of oak and what is oak usually used in ?
Strong, hard, heavy and dense with a tight grain structure
Very resistant to fungal infestations and insect infestations
Oak is commonly used for furniture, joinery, flooring, panelling, decking and veneers.
Oak is the sturdiest material you can use when woodworking - it is good/bad because its very heavy
What are the physical properties of Beech and what is beech used in ?
Beech is a hard wood, moderately heavy and solid, with good mechanical properties. It has particularly high resistance to compression, though less so to bending or tension because of its short fibres. Very fine texture. It has a tendency to warp substantially when exposed to changes in humidity.
Beech timber is suitable for a variety of purposes, including fuel, furniture, cooking utensils, tool handles and sports equipment
What are the physical properties of Ash and what are the uses for Ash ?
Ash wood is strong, dense, lighter in colour than oak and smooth to the touch. It takes gluing, stains and polishes well, making it popular for woodworking projects. Less prized than oak and more physically appealing than beechwood, Ash is a great middle-ground for many tasks.
Ash wood is susceptible to insects and fungus when exposed to soil. This makes the material unsuitable for outdoor furniture pieces.
