CHAPTER 10

FABRICATION AND MANUFACTURE

Learning Objective: Upon completion of this chapter, you will be able to identify and understand the tools, equipment, and procedures used to cut, layout, and fabricate specified projects.

As an Aircrew Survival Equipmentman, you need to know what materials are best suited for the job at hand if you are to be considered a master craftsman of your trade. Therefore, to lay the groundwork to aid you in becoming a skilled PR, this chapter discusses the textile materials, tapes, webbing, thread, cards, knots, and seams you will use.

Many of the repairs you will be required to make can be accomplished by replacing missing or worn hardware. There are occasions when minor repairs require hand sewing because machine sewing is impractical or impossible. For instance, it might be advisable to make minor repairs to aircraft upholstery by hand sewing the repair in the aircraft rather than by bringing the item to the shop. On the other hand, most sewing is done by a sewing machine. A seam is usually constructed faster, and is more durable, when a sewing machine is used. The use of a sewing machine gives the seam a better appearance. To do your job right, you must know the types of handmade and machine-made seams and how to make them.

TEXTILE MATERIALS, TERMS, AND MEANINGS

When a PR talks about warp, he doesn't mean something's out of shape; and when he talks about filling, he isn't referring to teeth. He's using terms textile manufacturers use, terms that are standard throughout the textile industry. The Navy uses these standardized textile terms to identify and classify materials on Navy stock lists. Aircrew Survival Equipment Changes and Bulletins also contain some of these terms. To comply with these repair instructions, you must first understand the terms used in them.

FIBER AND FILAMENT

Fiber is the basic unit used in the fabrication of textile yarns and fabrics. Vegetable, animal, and mineral fibers are natural fibers; nylon, dacron, and rayon are synthetic fibers. A filament is an individual strand of material, and can be any length. Filament is also another word for fiber, usually used when indicating or referring to synthetic fibers. A fiber, or filament, is the smallest unit in any type of cloth. An example is a silk filament, which may vary in length from 300 to 1,000 yards. Synthetic filaments may be several miles long.

Staple

The staple is the smallest unit of a naturally occurring fiber, or a synthetic filament cut in short lengths to be combined with other fibers in the manufacture of a variety of materials. When used in reference to the naturally occurring fibers, it denotes quality or fineness, such as "long staple" cotton.

Yam

Yarns are continuous strands of textile fibers or filaments, in a form suitable for manufacturing textile materials. The strength of the yarn is influenced by fiber strength, size, and length; size of the yarn; and tightness of twist. The strength of textile fabrics is determined by yarn strength and weight. You may form yarn by any of the following processes: a number of fibers twisted together, a number of filaments laid together without twisting, or a number of filaments twisted together. Yarns formed by twisting a number of filaments together are referred to as multifilament (many filament) yarns. Ply yarn is two or more single yarns twisted together.

Figure 10-1.-Textile terms.

Selvage and Raw Edges

The selvage edges of material, as shown in figure 10-1, are the edges of cloth, tape, or webbing that are woven to prevent raveling. When the material is cut, the resulting edge at the cut is referred to as a raw edge.

Warp

There are threads that run lengthwise of the cloth parallel to the selvage edge. If there is a difference in the strength of the warp and filling threads, the warp threads are usually stronger, because they form the framework for the material and support most of the strain during the weaving process. Figure 10-1 shows both warp and filling threads.

Filling

Filling is also referred to as a woof, weft, or pick. It is the threads that run crosswise to the cloth as it comes from the loom. This term is not to be confused with filling in the sense of sizing, which means the addition of substances that give body or decrease porosity of the material. Warp and filling threads must be determined in pattern layout because patterns (unless otherwise stated) are always cut with the warp and filling.

Weave

The weave is an interlacing of two sets of threads (warp and filling) to form a specific pattern. The manner in which the material is woven or constructed affects many of the cloth properties, such as tensile strength, air permeability, and elongation.

Bias

A bias is a diagonal line of a cut, a fold, or a seam across a piece of textile material at an angle of 45 degrees to the direction of the filling threads in the material. Bias construction is used to save material, prevent tearing between sections, and provide elasticity where it is a requirement for a satisfactory performance of the article. The bias direction of the fabric has a greater stretching quality than the straight direction. A bias cut is shown in figure 10-1.

Tensile Strength

The force required to break a material is called tensile strength. The tensile strength of a fabric is stated in pound-per-inch width for warp and filling. The tensile strength of webbings and tapes is stated for the full width.