MODELLING+MATERIALS





=**__CARDBOARD.__**=

Cardboard is an excellent material for sketch models. It is easy to cut and bend, and can be glued together to make thick sections or joints. Cardboard can be painted or sprayed to colour it. You can draw on it with marker pens, felt-tips or coloured pencils to indicate joints and surface details such as ribs or switches. All these qualities make it ideal for simple models and flat shapes. There are lots of different types of card available. They range in quality from strawboard, which is usually grey, to high quality art boards with a good surface and choice of colour. Corrugated boards can be useful for their texture as well as strength.

=**__FOAMED PLASTICS.__**=

Foamed plastics are very useful for building sketch models, especially those that have curved shapes. There are several different types and grades of foamed plastic.

Expanded polystyrene is a coarse-grained, white material available in block or sheet form. It is suitable only for sketch models because of its grain. This tends to crumble and makes it difficult to achieve a good surface finish. This material can be cut quite successfully with a hot wire or knife, but a saw will give a very crumbly finish. The surface can be filled with a water-based filler such as plaster of paris, and sealed with a water-based paint. Many house hold paints are suitable for this, including emulsion paint.

Styrofoam is a fine-cell expanded polystyrene foam, usually white but sometimes blue. It is available in a standard or high density grade. High density styrofoam is more closely packed, but both have a very fine grain structure. This makes styrofoam far less crumbly than polystrene, so it is much better for making models. It can be painted with water-soluble paints and glued with PVA adhesive. (Like polystyrene, styrofoam is best cut with a hot wire of knife. but unlike polystyrene it can also be cut with a band-saw or hacksaw to give an acceptable finish.)
 * WARNING:- Cutting expanded polystyrene and styrofoam with a hot wire generates toxic styrene fumes. It should be carried out in a well-ventilated room, and the wire should be set to operate below red heat.*

=**__WOOD AND WOOD PRODUCTS.__**=

Wood is a strong and durable material useful for building sketch models, particularly those that are large or need to last a long while. It is also useful for building more precise block models that have large curved shapes, as it can be built up into thick sections and these curves shaped easily. Wood can be bonded together with a variety of adhesives. The type you choose depends on how permanent a joint you need. wooden dowels can be inserted across the joint to strengthen it. this stops the pieces slipping when they are clamped together. The most suitable types of wood for model-making purposes, and the easiest to cut and shape, are those that are soft and hane a straight grain, such as **jelutong**. Once shaped, the surface of the wood can be primed and filled and a very smooth surface can be achieved. It is possible to simulate even a high gloss of a plastic moulding. However, to produce such a finish is very time consuming, and wood should only be considered for this type of finished model if the shape is too difficult to produce in an engineering material. MDF (medium density fibreboard) is a flat, compressed board available in several thicknesses. It does not warp and is easy to cut and shape. This makes it ideal as a material to use for quick models. Being so soft and porous, however, means that it damages easily. As with wood, although it is possible to produce a good surface finish it will take alot of patient work.

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