Scratch-built models can be simple or complex--it’s up to you. They can take any shape or form you desire. Many modeling experts construct their own kits as miniature of something in real life.

Scale modeling means that the size and dimensions of the model must be in direct accord with the prototype. Determining the size of the model requires that you know the dimensions of the real thing, which you can learn from specifications in books and training manuals. Or, if the prototype is nearby, take a tape measure (if the object is small enough) and get the actual dimensions yourself.

Scratch-built models made from your imagination don’t have to be so exact or to scale, and they are ideal for first attempts. Before you tackle the immense job of making your own miniature prototype, try assembling a nonscale model from various extra parts and stock plastic. Don’t be afraid to cut parts the size and shape you want. Small parts may be easier to mount if you use tube cement, or better still, 5-minute epoxy.

A conversion means that you take the basic model as presented in the kit and change it here and there as you think necessary. An example of a conversion is shown in Figure 8-5. The model on the left shows the plane as it came from the box. The model on the right shows the conversion.

Converting kits is not extremely difficult, but it does require you to think ahead and to know the kinds of things that are required to make the changes work. If you cut too much from a part, it may not fit with another, and you’ll end up throwing your mistakes into the trash.

The basic tools and supplies required for kit conversion are reference materials, a hobby knife, saw, file, sandpaper, and cement or epoxy. An accurate ruler or gauge helps you measure parts; you want to be sure that the parts are the proper scale.

Some conversions entail using parts from other kits. That’s why you should always keep the extra parts from models you finish for use in your conversions. The average avid model builder has a chest full of extra parts left over from the dozens of models he or she has assembled.

To make it easier to find things fast when you need them, separate your extra parts into categories, such as airplane fuselage parts, tank parts, that sort of thing. Some modeling pros like parts of different scales in separate bins. It’s considered taboo, not to mention awkward-looking, to mount a 1/24-scale tank cannon on a 1/72-scale fighter jet.

A few experts use plastic stock for their conversions. The stock is available in various sizes and shapes at the hobby store, like those in Figure 8-6, and is the same styrene plastic used in the kit. You can cut it, saw it, heat it, and cement it to fit your needs. Many conversions are relatively minor, such as:

Turning the front wheels of a car or truck at an angle

Making the canopy of an airplane slide back and forth

Hinging the flaps, ailerons, rudder, and stabilizer in an airplane

Opening the commander’s hatch in a tank

But some conversions are more complex and require a greater degree of patience and skill:

Changing a hardtop coupe into a convertible

Shortening or lengthening the wingspan of an airplane

Cutting the outer shell of the model to reveal the inner workings, such as a cockpit, engine, or the interior of a submarine

If you are interested in kit conversions, you should practice cutting, filing, and assembling scrap parts. After you get the hang of it, you can attempt your first minor conversions.

Vacuum-forming is one way to provide kits for unusual models. The molds for vacuum-forming aren’t nearly as expensive as those for injection-molding. Some vacuum-formed kits use the same high-impact styrene plastic as the injection-molded kits, so you can assemble them with the same cement, putty, and other supplies. But before building a vacuum-formed kit, read the instructions. If the plastic is not styrene, a special type of cement and putty may be required.

The technique of vacuum-forming is not complicated; in fact, you can do it in your own home. You need a vacuum-forming machine, plastic, and molds. You can even construct your own models if you can’t find what you need. With a vacuum-former, you can build your own models from scratch or replace parts of a kit that have been lost or damaged. See your hobby dealer for more information on vacuum-forming machines.

An airbrush used compressed air (and sometimes non-flammable gas) to propel the paint out of the canister and onto your model. You can adjust the flow of the air so that the paint goes on thick or thin. By holding the airbrush just right, you can obtain all sorts of unique and interesting painting effects, which cannot be duplicated by either spray painting or brush painting.

An airbrush is ideally suited for painting small parts already attached to the model and when painting camouflage colors over the model. These are only two examples of how an airbrush can be used effectively; there are countless others.

The basic airbrush setup consists of the airbrush, a paint bottle (or cup), and an air supply. Hobby airbrushes often use cans of compressed gas as the propellant. (Actually, the cans are filled with a compressed, non-toxic, non-flammable liquid; the liquid vaporizes when it comes out of the can.) Professional airbrushes use air tanks and compressors.

The air supply is connected to the brush by a hose. You control the air through the brush by pressing a trigger button. When you press down, the air flows through the brush. When you release the button, the air stops. Paint is sucked through the brush when air flows through it.

The paint bottles are removable so you can change colors quickly. To change from red to blue paint, for example, remove the canister filled with red paint and replace it with the one filled with blue paint. The last bit of red paint still in the brush is expelled the moment you push the button. That’s why you should always spray the first squirt of paint onto a towel after each color change.

Your airbrush can use paint that comes in bottles, but is must be thinned to the proper consistency first. For best results, a special airbrush thinner should be used. If the paint is too thick, it will clog up the brush. If it is too thin, it won’t cover the model well and will be splotchy and unattractive.

Airbrushing is an art, and it takes many hours to get used to it. If you want to learn to use the airbrush, practice first on some scrap artboard. Fill the brush with a color, attach the air supply, and squirt away. Practice holding the brush at just the right angle and be sure to move it back and forth while spraying. Airbrushing is much too involved to be adequately covered in this book. See your library for additional books that offer more details on how to airbrush.

Since the tree is the same plastic (even the same color) as the parts, you can use it for your model. The kind of plastic used in model kits becomes soft when heated, and when it is soft you can form it into all sorts of shapes.

The best heat source for working with tree is an ordinary candle. To heat the tree, hold a piece in both hands and swirl it quickly around the tip of the flame. If you get the plastic too close to the fire, it will turn black and may be ruined. Be sure that the plastic does not actually catch fire. When plastic burns, it gives off a strong odor. If a piece of tree you are working with accidentally catches on fire, douse it in a can of water (keep the water nearby just in case) and air out the room. Avoid breathing the fumes of the burned plastic.

Once the plastic softens, you can gently pull it apart to make fine plastic thread or even bend the tree to make angled pipes or cables. With practice, you’ll learn how to work the tree to get just the result you want. Don’t expect to get it right the first time around.

Once common use for tree includes making the guy wires in older airplanes. You’re probably familiar with the guy wires in World War I planes that connected the two (sometimes three) wings. Antennae were used in airplanes during World War II and the Korean War. These wires often stretched from the canopy to the rudder or stabilizer. Another common use for tree is for making cables and tubing, for airplane cockpits and engines, even the umbilical cord for astronauts working outside the Space Shuttle.

Once the tree has cooled, you can cement and paint it just like any other plastic part. Use only a tiny bit of glue or use white glue. If the tree piece is large enough, you can sand and file it to just about any shape.

This chapter will introduce you to a number of techniques used by the pros, those who consider model building both an art and a science--not to mention a challenge. use the techniques in the following pages as ideas to stimulate you and to get you thinking like a modeling expert. If you care to learn more about how the pros build models, look in your local library for additional books and periodicals on the subject of plastic model building.