Wood Flashcards
how much % of world’s wood comes from North America?
1/3
t or f wood takes less energy to produce than that of steel, cement, copper and aluminum
true
what is the most economical choice for building materials
wood
what is wood technically?
- dead or dying cells below the cambium layer
- made of small fibres that are long and narrow
what strength is wood strong in?
tension
what bonds the cells (cellulose) together in wood?
lignin
what % makes up wood?
- 60% cellulose ; small long narrow cells
- 28% lignin; glue that holds all together
- 12% sugars and extracts
what are characteristics of hardwoods?
- dicotelydons
- oak, maples, birch ect
- cells thicker, denser and stronger
what are characteristics of softwoods?
- conifers/ evergreen
- spruce pine fir and cedar
- cells are thin, less dense and weaker
what is the pith of the tree
- centre, where earliest growth occurs
what is the heartwood?
dead portion of the tree located towards the centre
-provides structural support, more resistant to rot
what is the sapwood?
-contains the living portion of the tree: sap
what is the cambium ?
growth area of the tree
what is the springwood ?
rapid growth, thin walled cells
what is the summerwood?
slow growth, thick walled cells
when does the growth year start/ stop of a tree?
-stops when tree drops leaves and goes dormant, starts when new leaf development
t or f, all trees have growth rings
-false; only occurs when climate limits growth part of the year
characteristics of cedar
-tannins, resists rot, easy to work with, food look, colour and aroma
uses of spruce ?
- farming, must have preservatives for outdoor use
- good availability
uses of pine?
- good availability
- needs preservatives for outdoor uses
what is the hardest softwood?
fir
characteristics of hemlock
-good rot resistance, poor availability, hard to work with
characteristics of fir?
-even grain, needs preservatives for outdoor use
redwood characteristics
-good for structure, rot resistant, poor availability= expensive
characteristics of hardwoods?
-good for furniture, expensive, will rot and doesnt receive preservatives well