performance of wood

Question 1

How does grain affect a woods workability?

Answer 1

• can increase the price

- tight and fine grains make them easy to turn [beech]

Question 2

How is wood structured?

Answer 2

• wood fibres are hollow straw-like cells held by lignin [tracheid]
• tracheid carry water and nutrients from the roots to the leaves

Question 3

how is the grain distinguished?

Answer 3

• direction of the rays
• wood splits in the direction of the rays
• planning with the grain avoids the wood tearing

Question 4

why is cutting across the grain easier than along it?

Answer 4

Fibers are shorter and hold together yet are easier to overcome so let go sooner

because wood splits along the grain so the wood would continue to split after it was cut

Question 5

what is the definition of Anisotropic?

Answer 5

the grain giving wood different physical properties in different directions
-natural wood is stronger along the grain not across it

Question 6

are manufactured boards anisotropic?

Answer 6

no

Question 7

what defects can occur to wood?

Answer 7

• Knotts can fall out as wood shrinks
• machining can leave marks of the wooden surface
• damage can occur from insects, rot and disease

Question 8

what term best describes waters sponge-like qualities?

Answer 8

hygroscopic [absorbs moisture which causes swelling]

Question 9

what prevents timber distorting?

Answer 9

seasoning

Question 10

what causes wood to distort?

[evaporation]

Answer 10

• water evaporates from freshly felled timber causing shrinkage
• if it evaporates too quickly or unevenly it can; twist, warp, bow, cup or split

Question 11

the process of seasoning - air dried and kiln dried

Answer 11

air dried
- stored undercover and left outside to acclimatize naturally
Kiln dried
- uses steam to artificially dry the wood which speeds up the process

Question 12

why is wood seasoned?

Answer 12

To make wood stable to prevent warpage, shrinkage and splitting. This makes it less likely to change during manufacture

Question 13

why is outdoor seasoned timber best suited for external projects?

Answer 13

it was acclimatized to outdoor conditions so is stable in that environment

Question 14

what are the differences between kiln drying and air drying wood ?

Answer 14

• air drying is naturally done with limited control over the process
• it takes longer than a kiln

Question 15

what properties does seasoned timber have?

Answer 15

• stronger [stable]
• less likely to decay/rot
• less likely to corrode ferrous metals
• absorbs preservatives better

Question 16

what are the 3 shrinkages and why does it occur?

Answer 16

• wood swells and shrinks with the seasons due to moisture levels
• diamond shape [square sections]
• cup [u shaped]
• uniform shrinkage

Question 17

where does shrinkage occur?

Answer 17

• most around the year rings
• radial shrinkage between 2-8%
• less shrinkage along the length

Question 18

advantages and disadvantages of joining wood

Answer 18

• woods with high oil contents are hard to glue [teak]
• acidic woods can corrode metal fixtures
• ash and beech glue well as they have a big cell structure

Question 19

what is forming?

Answer 19

additive and wasting processes along with manipulation

Question 20

what are wasting processes?

Answer 20

carving, turning, milling and routing

Question 21

what is steam bending?

Answer 21

uses heat and moisture to make wood pliable

[open pore structures are easier to steam]

Question 22

steam bending process

Answer 22

• heat is applied to make the wood bend without breaking
• held in a former to cool and dry in shape
• open pore structures are better to steam bend like ash and beech
• steam bending maintains the longitudinal strength of the wood

Question 23

machining qualities of wood

Answer 23

• natural wood is difficult to machine as it is hard and tough
• density of wood is less predictable
• oil can clog up tools
• manufactured boards have uniform quality and density so they are predictable to work with

Question 24

what is laminating?

Answer 24

combines wood and adhesives for different purposes

Question 25

why is the laminating process used?

Answer 25

• used to create curves using areoply and flexiply
• used to get larger wider wooden sections
• melamine formaldehyde or wood veneer can be added to enhance surface properties

Question 26

how do insects affect wood and how can it be prevented?

Answer 26

• insects are attracted to the starch and sugars in wood
• insects lay larvae inside the wood which hatch and burrow out
• dry, varnished or painted wood with high oil content reduces the risk

Question 27

fungal attacks

Answer 27

• damp or poorly ventilated conditions allow fungi to attack
• fungal spores attach to the wood and feed of its nutrients that causes rot
• dry rot makes the timber weak, dry and brittle
• wet rot allows fungi to be seen
• dry wood is better protected

Question 28

how is wood made moisture resistant?

Answer 28

• oily woods [teak and redwood] can endure wet conditions
• marine ply is made from water- resistant hardwood veneers and waterproof adhesive to withstand wet conditions
• paint, varnish and oil can be pressure treated to increase moisture resistance

Question 29

what conditions do toxic trees cause?

Answer 29

wood dust and sap can cause; irritation to the skin, respiratory problems, nausea and affect vision
-cedar can cause migraines, stomach problems and effect the nervous system

Question 30

what regulations are in place by Control of Substances Hazardous to Health (COSHH) for toxic woods?

Answer 30

• wood dust is limited to 5mg per cubic metre
  extraction and ventilation systems
  -PPE must be provided
  -beech and bamboo are food safe and used for kitchen utensils and toys

Question 31

what are grain patterns?

Answer 31

how the wood is cut up

Question 32

what is warpage?

Answer 32

wood has swelled and moved

Question 33

What woods are toxic?

Answer 33

akasha wood, oak, seeder, teflon, eucaliptus

Question 34

What are machining qualities?

Answer 34

how easy the wood is to work with

Question 35

what 2 factors cause wood to split?

Answer 35

heat and movement

Question 36

what is the end grain of wood?

Answer 36

pattern at the end of a piece of wood

Question 37

how are knots formed ?

Answer 37

branches snap so resin fills the whole and seals it off to form the knot

Question 38

Is wood weak or strong if the grain is in different directions?

Answer 38

weak due to different forces

Question 39

Why is kiln dried wood better for indoors?

Answer 39

there is absolutely no water inside