Timbers Flashcards
Soft wood examples
Redwood
Pine
Yew
Spruce
Cedar
Douglas fir
Larch
Soft wood
- 5-10 years to mature
- mostly from northern hemisphere
- known as conifers/evergreens
- fast growing, sustainable as can be regrown in a life time
- straight trunks
- careful forest management ensures worldwide demand is met
- pine like leaves
- produces cones
FSC
forestry stewardship council
Hard wood examples
Birch
Beech
Oak
Mahogany
Ash
Maple
Walnut
Balsa
Cherry
Mangrove
Acacia
Holly
Hardwood
- 150+ years to mature
- grown across the world
- broadleaves, deciduous
- more durable than soft woods
- variety of colour and texture, ebony-ash
- slow growing
- more expensive than soft woods
- tighter grain
- nuts and berries
- holly is an exception as it is evergreen with broad leaves
Faults in wood
Grain
Knots
Cupping
Bowing
Twisting
Knots
Not stable
Very dense
Cupping
Not dried properly or from heart wood
Bowing
Not supported correctly
Twisting
Not stacked correctly
Biological attack
Insects: woodlice, death watch beetle, wood worm
Fungi: wet rot (stays at submerged area), dry rot (moves up walls, not enough air)
Conversion
Process of sawing logs into commercially viable timber.
Slab sawn
Wide planks
Easy manufacture
All timber used
Cupping, unstable
Cost effective
Fast
Radial/Quarter sawn
Thiner planks
More expensive
Very stable
Time consuming
Cutting results in a good grain pattern
Seasoning
- process of removing excess water and much of the bound moisture from the cell walls.
- Reduced to 20%
- immune to rot and decay
Kiln seasoning
Put in a steam oven
Steam cures timber
Vacuum draws water out
Takes 24hrs
Quick and cheap
Natural air seasoning
Roof, no walls, air circulates
Every 25mm takes one year to season
Expensive
High quality and very stable
Manufactured boards and types
Chip board
MDF
Plywood
Lamin board
Block board
Thermosetting plastic holds boards together. Not recyclable or sustainable but is cost effective
MDF
Medium density fibre board
Plywood
Strong, layers at 90 degrees
Odd numbers so grain runs the same way
More than 5 layers becomes multiply
Advantages of manufactured boards
- large standard sized sheets
- uniform thickness
- stable in most atmospheric conditions
- grained boards have good strength to weight ratio
- thin sheets can be easily bent
Disadvantages of manufactured boards
- difficult to join
- exposed edges often need to be hidden
- thin sheets become easily distorted, unless held in a frame
- adhesives can blunt cutting tools quickly
