Wood as engineering material. Presentation for secondary students. Spanshi curriculum 2º ESO (13-14 yr)

1. Woods
Departamento de Tecnología
Miguel Sáenz de Santa María 2007-2016

2. Wood as Engineering Material
 Wood is composed of cellulose, lignin,
hemicelluloses, and minor amounts of
extraneous materials contained in a cellular
structure.
 Wood has been used as a natural material for
homes and other structures, furniture, tools,
vehicles, decorative objects, shipbuilding,
bridges, cooperage, barn timbers, farm
implements, railroad cross-ties, fence posts,
and flooring.

3. Where do we get wood?
 Traditionally, wood has been extracted from
the trunks of the trees, but nowadays we can
get profit from branches and roots, used to
obtain wood derivatives.
 Parts of the trunk:
– Bark
– Cambium
– Sapwood
– Heartwood
– Pith

4. Woods
Natural Woods (obtained directly from the
trees)
Manufactured Boards (obtained processing
branches, shavings, sawdust and fibres)

5. Natural Woods
Hardwoods, they usually grow slowly, 25 year
or more.
Softwoods, grow fast, 5-15 years
Exotic woods (tropical woods), can be hard or
soft and they come from tropical climates.
Other trees, used to obtain materials other
than wood

6. Natural Woods
Hardwoods
(Maderas Duras)
Oak (Roble)
Chestnut (Castaño)
Ash (Fresno)
Walnut (Nogal)
Olive (Olivo)
Beech (Haya)
Softwoods
(Maderas Blandas)
Poplar (Chopo)
Pine (Pino)
Fir (Abeto)
Cedar (Cedro)

7. Exotic Woods
Mahogany (Caoba)
Ebony (Ébano)
Sapelle (Sapelli)
Teak (Teca)
African Teak (Iroko)
Gaboon or okoumé (Okume)
Brazilian Cherry (Jatobá)
Balsa

8. Other trees
Cork Oak (Alcornoque), used to obtain cork.
Eucalyptus (Eucalipto), used to obtain pulpwood, the
basis of paper manufacturing.

9. Process
Cutting
Drying
Shaping

10. Drying
 Natural drying or air drying: The technique of
air drying consists mainly of making a
stack of sawn timber in a clean, cool, dry
and shady place. It is a slow process.
 Arificial drying or kiln drying: artificial or 'oven'
drying consists basically of introducing
heat. Timber is stacked in chambers,
which are fitted with equipment to control
atmospheric temperature, relative humidity
and circulation rate.
 Mixed drying: This is a combination of the
two methods: first natural drying is used to
reach about a 20% of humidity, then
artificial drying is used to complete the
process.
Edward Stojakovic

11. Manufactured boards
Natural woods can't be used to obtain large
pieces, almost larger than the trunk of the
tree.
Great amount of material is obtained from the
branches and in the process of sawing.
Some technologies make possible to obtain
large layers of fine wood.

12. Chipboard
(Aglomerado)
It's made from saw dust and chips,
mixed and pressed with resins and
additives.
It can have two layers of fine
natural wood or plastic.
Sometimes the edges are covered
with the same material, after the
cutting.

13. Plywood
Plywood is composed of thin sheets of natural
wood (veneers), glued in layers to form a
panel.
Plywood always has an odd number of veneers
with the fiber alternatively oriented
(Contrachapado)

14. Fiberboard
Made from wood fibres
glued under heat and
pressure
There are three types:
Medium density (MDF)
High density (HDF)
Low density (“Tablex”)

15. Measures of the boards I
244 cm
122 cm
Strange measures, aren’t they?

16. Measures of the boards II
8 ft = 244 cm
4 ft = 122 cm
Not in British units!

17. Tools for Carpentry
 Marking & Measuring: Carpenter’s pencil, ruler,
compass, gauge (gramil), try square, scratch
awl.
 Cutting & Carving: Chisel (formón), gouge
(gubia), mallet (mazo).
 Sawing & Shaping: Saw, hacksaw, handsaw,
jigsaw, copysaw, circular saw, files.
 Drilling: Gimlet, carpenter’s brace, drill, drillbits.
 Planning & Sanding: Plane, sandpaper,
sander.