Timbers

Question 1

Seasoning

Answer 1

A tree is about 85% water. Seasoning is the drying of timber down to 10-12%

Means that they wont warp or crack and means they wont expand and shrink so if needed for a product it will always fit together. They are stronger and more resistant to decaying.

Question 2

Use of stock materials

Answer 2

Sold in standard sizes

Means the manufacturer doesn’t have to spend time recutting wood and saves a lot of wasted timber, it is also mass produced so is cheaper

Question 3

Cause of tree death

Answer 3

Hurricanes and storms blow trees over and they take a long time to grow back so reduces supply

Disease can kill trees such as ash dieback so also reduces supply

Question 4

Treatments

Answer 4

It can be pressure treated with a preservative which forces the chemicals deep into the wood and makes it resistant to rotting. An example is tanalith E

It can be pressure treated with fire retardants that reduce its ability to burn. Reduces damage and gives people more time to escape and also increases the time to stop the fire.

Question 5

Built in product obsolescence

Answer 5

Manufacturer’s purposefully make a product to only last a certain length of time. This means people by products more often and therefore they increase their profits.

However this massively increases the waste produced as people have to dispose of it rather than try to fix it

Question 6

Forces

Answer 6

Compression- a squishing force

Tension - a pulling force

Shear - two forces acting in opposite directions

Question 7

Frame structure

Answer 7

Square is a useful shape but isn’t very strong

Can be strengthened by:

Adding struts across each corner
Adding a thin panel through the center
Adding a strut from one corner to another

Question 8

Natural forces in wood

Answer 8

When a tree grows due to wind it can lean over - compresses the wood so when it is cut down and the force is released it can cause the wood to warp

Question 9

Pre stressed beams

Answer 9

When a beam is initially put under pressure it will bend and become less strong

If it is pre tensioned when it is used in construction it will bend less making it stronger

Question 10

Lamination

Answer 10

Laminate - thin layer of material

Thin layers are glued and bent to produce much larger curves than steaming

Question 11

Braces and tie bars

Answer 11

A brace is a bar that is added to a frame to strengthen it. They are usually diagonal to make triangles. Because it cant stretch it holds the beam in place

Question 12

Embedding composite materials

Answer 12

A composite material can be added to a wooden beam such as fibreglass to make it water proof. Steel fibres can be embedded during lamination to improve the tensile strength

Question 13

Regular sections

Answer 13

Standard sized timber that is square

Question 14

Mouldings

Answer 14

Length if timber that has been routed into decorative shapes - skirting boards

Question 15

Dowels

Answer 15

Wooden rods that are round

Question 16

Sheets

Answer 16

Manufactured boards that come in wide thin sheets - 2440x1220 mm

Question 17

Planed all round (PAR)

Answer 17

All four edges have been planed and the edges have been slightly rounded - better for handling and construction when the design uses standard sizes - sold by sawn size so PAR wood is usually 6mm smaller than actual dimensions given

Question 18

Planed square edge (PSE)

Answer 18

Two faces have been planed but edges are left square allowing the manufacturer to change their size if standard sizes aren’t used without having to spend extra all dimensions are 3mm smaller than given dimensions

Question 19

Use of a bag press

Answer 19

To hold laminates in place during moulding

• stops the layers slighting as it encloses the hole thing - reduces off cuts and waste so reduces cost
• applies equal pressure so creates a smooth curve

Question 20

Lamination

Answer 20

Multiple layers of wood adhered together eg. Plywood
Odd numbers if layers so bottom and top grain are same direction
Layers at 90 degrees to each other to give uniform strength
Bonded with epoxy resin or urea formaldehyde

Question 21

Lamin board

Answer 21

Thin strips stacked between veneers on either side

Question 22

Block board

Answer 22

25mm wide
Strips placed edge to edge and placed between two veneers
Thicker than normal boards
Used for doors

Question 23

Flexiply

Answer 23

Ply but all the wood grain is in the same direction so it can bend in one direction
Used with formers and then laminated to form large curves
The former applies and even pressure to ensure a smooth curve

Question 24

Why wood decays

Answer 24

Rot both dry and wet
Insect attack eat the wood
Mould cause the wood to break down
Vermin eat the wood

Question 25

Wood is anisotropic

Answer 25

Means that depending on the direction with which you work it, it has different physical properties depending on the direction of the cut

Question 26

Surface defects

Answer 26

Knots look nice but are at different densities so can fall out when the wood expands/shrinks and therefore reduces strength Can be damaged by insects, rot or machining

Question 27

Different types of seasoning

Answer 27

Kiln dried: Pros- faster, cheaper wood 6 weeks per cm of wood Cons- fast drying can cause warping and cracking Air dried: Pros- no warping and cracking Cons- slow and expensive wood 1 year per cm of wood Better for outside as that is where it dries and wood is placed on spacers to increase airflow

Question 28

Manufactured board

Answer 28

1220x2440 mm

Question 29

Rough sawn

Answer 29

Very cheap and is used for palettes and roofing