MYP Design Woods and Timber Notes

Hardwood and Softwood Describe the Tree, Not the Hardness

1. A hardwood comes from a broadleaved tree that drops its leaves each autumn, such as oak, beech or ash.
2. A softwood comes from a cone-bearing evergreen with needles, such as pine, spruce or cedar.
3. The split is botanical, so it says nothing directly about how hard the timber feels under a chisel.
4. Balsa is the proof: it is classed as a hardwood, yet you can press a thumbnail into it, which is why model aircraft are built from it.
5. Yew is a softwood that is denser and tougher than several hardwoods, which is why English longbows were cut from it.
6. As a working rule, hardwoods grow slowly and cost more, softwoods grow fast and stock the cheap end of the timber rack.

Five Timbers Worth Knowing by Name

1. Oak is heavy, strong and open grained, used for flooring and furniture, but its acid attacks steel screws and leaves blue-black stains.
2. Beech is close grained, pale and hard wearing, which is why it turns up as chopping boards, chair frames and workshop mallets.
3. Ash bends and absorbs shock without splitting, so it becomes hammer handles, hockey sticks and steam-bent chair backs.
4. Pine is cheap, light and easy to cut, but knots wander through it and blunt a chisel edge or wreck a clean cut line.
5. Cedar contains natural oils that fight rot and insects, so it survives outdoors as cladding and shed roofs with no treatment at all.

Manufactured Boards Trade Character for Consistency

1. Solid timber comes in narrow planks and moves with the weather, so factories break wood down and rebuild it as a flat sheet.
2. That sheet is a manufactured board, and it behaves almost the same in every direction because the original grain has been chopped up or crossed over.
3. MDF is wood fibres and resin pressed into a dense board with a smooth face, perfect for painting and for laser cutting at 3 mm or 6 mm.
   1. Its edges drink paint and its dust is fine enough to need extraction and a mask.
4. Plywood is thin veneers glued in odd-numbered layers with each layer turned 90 degrees to the one below, giving strength both ways.
5. Chipboard is wood chips glued into a coarse board, cheap and heavy, used under kitchen worktops where nobody sees it.
   1. It swells and crumbles once water gets in, so it fails fast in a bathroom.
6. Boards come in large sheets, typically 2440 mm by 1220 mm, so a whole product can be cut from one piece with no joints.

Grain Direction Decides Where a Part Breaks

1. Wood fibres run like a bundle of drinking straws glued side by side, strong along their length and weak when pulled apart sideways.
2. Timber is several times stronger along the grain than across it, so a thin leg cut across the grain snaps under a load a long-grain leg carries easily.
3. Short grain is the classic failure: a narrow part where the grain runs across the short dimension, such as the thin bridge above a keyhole slot.
4. Plan your cutting list so the grain runs down the length of every leg, rail and handle.
5. Planing against the grain tears the surface into rough flakes, so read the grain direction before the first pass.

Wood Keeps Moving Until You Season It

1. Freshly cut timber, called green wood, can be more than half water by mass.
2. As that water leaves, the wood shrinks, and it shrinks more around the growth rings than along the length, which pulls boards out of shape.
3. Uneven shrinking gives you the named defects: cupping across the width, bowing along the length, twisting like a propeller and splitting at the ends.
4. Seasoning dries timber down to a stable moisture content before you use it, roughly 10 to 12 per cent for indoor furniture.
   1. Air seasoning stacks boards outdoors with spacers between them and takes about a year for every 25 mm of thickness.
   2. Kiln seasoning does the same job in a heated chamber in days, costs more, and also kills insects in the wood.
5. Seasoned wood still breathes with the room, so store your project flat and away from a radiator between lessons.

Wood Is Renewable Only If Someone Replants It

1. Timber stores carbon taken from the air while the tree grew, and that carbon stays locked in the furniture rather than in the atmosphere.
2. That only works if the forest is replanted, so felling faster than regrowth turns a renewable material into a disappearing one.
3. The FSC label, from the Forest Stewardship Council, marks timber traced back to a forest managed under agreed environmental and social rules.
4. Softwoods such as pine reach usable size in 25 to 30 years, while an oak takes over a century, which is most of why oak costs what it does.
5. Locally grown timber avoids shipping a heavy, water-filled material across an ocean.
6. Boards made from recycled chips and offcuts use wood that would otherwise be burned, which is a genuine point to argue in Evaluating.

Choosing Between Solid Timber and Board

1. Pick solid timber when the grain is part of the look, when the part is narrow and loaded, or when it will be jointed traditionally.
2. Pick a board when you need a wide flat surface, a painted finish, repeat parts cut on a laser or router, or a lower cost.
3. Many good projects mix both: a pine or ash frame carrying the load, with 6 mm MDF or plywood panels filling it.