Pattern sheets,

what are they good for?

A short tutorial on their use.

By

John Miller

Back in the “good old days”,when building from plans, scratch builders often found it  necessary to jump through hoops to get patterns of the parts they needed . In the days  Before the wide spread use of copy machines, it meant they had to trace the parts off the plans. This practice was laborious, and only as accurate as the trace, and cutting skills of the builder.

With copy machines, a copy of the plan would be made, and the parts cut out to be used as patterns. At times, depending on the design, and plan layout, it might take multiple copies to generate patterns of all the parts.

Until the late 80’s or early 90’s, virtually all model plans were hand drawn. If pattern sheets were produced, they may or may not be totally accurate. It depended on the skill and patience of the draftsman, as well as the accuracy of the blue print copying machines. Some methods introduced a linear legnthening.

Unlike other uses for mechanical drawings, model plans must be as accurate as possible because the part shapes are taken directly off them.

Computer Aided Drafting, commonly known as CAD.

The use of Cad for model plans started showing up in the hobby during the late 80’s as more hobbyists received training in these systems. The accuracy inherent in these digital plans also were directly applicable to CNC, and other forms of shaping operations. This has led to the growing use of “Laser cutting”,  to replace die cutting in kit making.

A happy side effect of the laser revolution in kit making is that laser cut files can be printed out, and used as patterns for the scratch builder.

A question comes to mind at this point. “Why would one want to scratch build when laser cut parts are available?”

I can answer that question, with “I can save some of my money in exchange for some of my time. I can also maintain control over an important aspect of model building, wood selection, for weight, and grain type for the use intended.”

Pattern sheets, when available, have taken much of the drudgery from creating parts from plans, and turned a formerly tedious process into a pleasant task.

The process

Most pattern sheets are laid out over representative sheets of material, balsa, and plywood, in our cases.

Our first task is to cut out these representative sheets and sort them according to types, sizes, and thickness.

Gather up, or produce, the types and sizes of materials that match these patterns. Most patterns call out the type and size, and number of sheets to be used. It makes this step a rather simple task.

Next. we want to attach these cut paper patterns to our materials. We don’t want to glue them so tightly to the wood that we have difficulty removing the paper later, so consider the following method.

I prefer to use 3M brand spray glue for this purpose. I use the following method to apply it.

Lay out the materials. I place all the wood spaced tightly with as few gaps as possible on top of a covered table. Place the paper patterns, face down on top of the materials, also tightly spaced.

We will direct the spray a foot or so above the surface and spray quickly, and lightly, letting the glue settle onto the surface. We just want a dusting on the exposed paper. After we’ve done this, carefully remove the patterns, and do the same thing to the wood.

In the cases where multiple sheets are called out, we use the same method, and lightly glue the sheets together before applying the paper pattern.

Let the glue set about 5 minutes or so, and we’re ready to stick the paper patterns to the matching wooden parts.

This next picture shows the patterns attached to the wood.  

We are now ready to cut out the parts. How we do this depends on the tools available, from an Exacto knife, to a band saw.

My preference is an electric scroll saw for most cutting. I’ll use a table top band saw for harder or thicker parts. A drill is handy when a part has a hole in it.

Chose your tools, and cut out the parts. Remember, it’s not necessary, or preferable, to cut to the line in most cases. It’s better to stay about 1/16” from the line. We’ll use a sander, or sanding block to bring the part to size.

The final step, is to sort the parts as to where they will be used, and place them into baggies. or containers of some sort. This keeps all the parts, and especially small parts grouped, together and helps prevent loss or breakage.

There you have it. A complete kit produced in just a few hours, of what was actually pleasant work. The proper wood for the use was under my control. The best model, for the use, should be possible with the use of these parts.