What Is Scratch Model Building?

Scratch building is the art of constructing structures and other models from raw materials such as plastic, wood sheets or strips, glue, paper, cardboard, etc. Some beautiful structures, locomotives, and railcars can be constructed for little cost and in less time than it takes to assemble and paint a kit.

Planning Your Construction From Scratch

So, how do you accomplish this? How is a model building constructed from scratch? …

First, you must plan:

What kind of model structure do you intend to construct and why?

  • How will it fit into your design’s motif, time, and setting?
  • Will it be modeled after a specific prototype?
  • How much room is available for it?
  • What are the measurements?

Motives

The motives of hobbyists who construct from scratch vary. Frequently, a requested model is unavailable in kit form or altogether nonexistent in the necessary scale. Occasionally, a hobbyist may be unsatisfied with available kits’ accuracy or level of detail. Seldom will an enthusiast choose scratch building for the challenge. 

Less typically do hobbyists build from scratch for economic reasons, as the raw ingredients frequently cost less than a bundled commercial kit.

Scratch building is an enjoyable pastime yet is also one of the most feared by those who have no idea where to begin. 

How To Start

 

If you have the answers to the following questions above, sketch the model building on paper or, if you have a CAD program, use it.

Label the drawing with the appropriate dimensions in the scale used

If the model you are scratch building is based on a prototype, ensure that you have multiple photographs of the original structure, as well as the prototype’s exact dimensions, so that you may make the model as realistic as possible. 

The actual dimensions of the structure can be transformed to the desired scale with relative ease. 

For a HO scale model, divide the prototype dimensions by 87; for an N scale model, divide by 160; for an O scale model, divide by 48; and so on. Once you have the measurements, you may use graph paper to draw out the structure and account for other elements such as downpipes, brick detailing, and overlaps.

After selecting or designing a structure on paper or a computer, you can construct it using the materials and scratch building procedures.

Construction Materials

 

Styrene is probably the most widely utilized material for a scratch building to construct the substructure. 

Additionally, you might use mat board (the material used for photo framing), gel foam, or balsa wood. The latter materials are less difficult to cut than polystyrene but probably not as durable. 

The wood might be more appropriate for larger scales, such as S and O. Laser board is gaining popularity as a more realistic material for scratch building buildings.

Styrene plastic (also known as polystyrene) is one of the main materials used to construct models from scratch. This plastic is simple to cut and glue, is available in various thicknesses, and even comes in modified forms and textured panels.

The materials needed to start can be purchased for $10 or less at any hobby store.

  • Always use a sharp, new blade with your hobby knife. It’s ideal for accurate measurements and straight cuts and a perfect instrument for marking and cutting styrene. 
  • A glue made specifically for styrene will produce superior results.
  • Keep a selection of fine grades of sandpaper on hand.
  • Compass or French curve: This tool is only required when cutting curves or circles.

Marking Your Cuts

 

The most crucial aspect of styrene cutting does not involve a knife. As with any material, the key to precise cutting is accurate measuring and careful planning.

Using a scale ruler, arrange your cuts and double-check each measurement. The “0” mark on most rulers is not placed precisely on the edge to maintain a clean measurement. 

Make your cutting marks using the ruler’s markings, not its edge.

Utilize a sharp pencil to mark the polystyrene. Since most styrene products are white, it is easy to spot blemishes.

Curved lines may be drawn using a compass or French Curve. If you’re too smart, you can try a Challenging Model Kits for Very Smart People.

Cutting Styrene

After markings have been created, it is time to cut. 

Based on the thickness of the styrene, you may be able to cut through the material in one or two passes, but the fundamental recommended practices remain the same:

  1. Place a sharp, new blade in your hobby knife. A new blade may make an enormous difference.
  2. Align a straightedge made of metal along the cutting line. Use the edge on the opposite side of the measurement markings to avoid damaging the edge and scratching the markings.
  3. Firmly hold the straightedge, and begin by making a very light cut along the straightedge’s side. This will provide a path for the blade to follow as pressure increases in successive passes.
  4. To score the styrene, make additional passes at a slightly increased pressure. Maintain a relatively mild pressure, and avoid forcing the cut since this can cause the blade to be stray.
  5. Unless the styrene is extremely thin (.010 or less), it will likely not be entirely cut through. This is acceptable; simply score the plastic with three or four light passes and proceed to the next step.

Break the Styrene

When working with thicker styrene, the hobby knife will not entirely penetrate it. Thankfully, you do not have to. Step two is to split the styrene board. If you’ve ever worked with drywall, you’ll recognize this method immediately.

After lightly scoring the styrene with the hobby knife, you can bend it away from the score to break along the line cleanly.

A second snap in the opposite direction may force the pieces to entirely separate, or you can hold the styrene piece at an angle and use the hobby knife to cut a clean line along the scoreline on the backside.

Tips

When making many cuts in plastic, it is often easier to make multiple little cuts and remove each piece separately.

Removing two or more sides for windows and doors may be essential.

Typically, a little quantity of mild bending is sufficient to shatter even these minor wall pieces without damaging most of the wall.

Before cutting the walls from a larger sheet of styrene, the window and door openings must be eliminated.

Sand the Trimmed Edges

 

Once the cut is complete, finish the edge with a couple of fast passes of fine-grit sandpaper across the cut edge. Also effective are emery boards, sanding blocks, and sanding ribbons.

When sanding, ensure that the cut remains square (unless you are trying to get a beveled edge.) As you gain experience and hone your skills, cutting a bit longer is frequently easier and then sanding to a uniform finish. As your measuring and cutting abilities improve, you will be able to cut more precisely, requiring less sanding.

A coarse grit of sandpaper can be used to scratch a rough plastic surface. This is useful if you wish to replicate wood grain or create other effects.

Using styrene solvent glue, you can quickly assemble the model once the pieces have been cut.

Gluing Styrene

Modeling glue is another important material you must not miss. To properly glue styrene, you need some knowledge and the proper adhesive because it is possible for styrene to melt if the incorrect adhesive is used.

Different Styrene Adhesives

You have an option between the following specific glues for styrene:

  • Polyurethane foam is a plastic adhesive foam that can connect polystyrene to polystyrene, as well as various other materials and material combinations. This unique adhesive for Styrofoam has the distinct advantage of being designed for both absorbent and non-absorbent surfaces. The respective variation may be selected at will. It adheres to styrene permanently and damage-free.
  • Acrylic Adhesive: An excellent acrylic adhesive is useful for bonding applications on nonabsorbent surfaces. This material is resistant to UV radiation and aging. There are both one-component and two-component acrylic adhesives. In most cases, the one-component form is sufficient for bonding polystyrene. Before bonding, a flash-off period is required for these adhesives.
  • Epoxy Resin Glue: epoxy resin adhesives are identical to acrylic adhesives. Also available in two-component and one-component configurations. Nonetheless, this glue typically does not require a flash-off time.
  • Water-Based Dispersion Adhesive: Dispersion adhesives are ideal for non-absorbent surfaces. As curing is caused by the evaporation of the water contained in the adhesive, a flash-off period must also be observed when employing them. Spray dispersion adhesives are also available on the market. Consequently, they are perfect for broad surfaces.