Cloth Weight

The cloth weight is the weight of a cloth, or fabric, in ounces per square yard. All fabrics have a designated cloth weight. For instance, a square yard of cotton duck may weigh 8 ounces; therefore, it is called 8-ounce duck.

CONSTRUCTION FEATURES AND USES OF VARIOUS TEXTILE MATERIALS

If a cigar ash burns a hole in your tweed jacket, you will not patch it with a piece of velvet material. If a life raft needs repair, you will not use tweed fabric to repair it. Or, if an NES 12 canopy needs repair, you won't use 7.25-ounce nylon duck. If a repair is to make an item usable,

must use like material.

In the not too distant past we were limited to natural fibers as a source for our fabrics and associated materials; but today, with the advent of synthetic fibers, we can enjoy their improvements in some respects over the natural fiber. Currently the natural and synthetic fibers have their respective advantages and disadvantages. Because you cannot use synthetic or natural fiber materials exclusively, you must decide which one best serves your purpose. There

Figure 10-2.-Basic weaves.

are many, many different types of fabrics, or cloth. When we say cloth, we mean any textile material over 12 inches wide from selvage to selvage.

The construction of cloth is determined by many factors, such as tightness of yarn twist, number of threads per inch, porosity of the yarns, and the type of weave used in its formation. The weave is one of the most important factors. The two basic weaves are plain and twill (as shown in figure 10-2). The plain weave is the simplest method of weaving and gives the smoothest surface of the fabric. It consists of the filling threads passing over one warp thread and under the next warp thread. The twill weave is a more complicated weave in which the filling threads pass over and under more than one warp thread, thereby producing a surface on the fabric that is generally recognized as a diagonal pattern.

Cotton

Cotton is a natural plant fiber, usually white. The fibers or "staples" are between 3/8 and 2 inches in length. Chemically, it is almost pure cellulose. Cotton fabrics, webbing, and tapes absorb water readily unless treated. They dry more slowly than the synthetic fabrics and are more susceptible to mildew and fungus growth. One should never ignore the presence of mildew because it seriously affects the tensile strength of cotton and other fabrics. Heat is less damaging to cotton than to the synthetics. Insect damage should, however, always be considered because cotton is a food for certain cellulose-eating insects, and cotton makes good nesting or cocoonspinning material for rodents and insects.

Nylon

This is a synthetic fiber of extreme toughness and elasticity. It absorbs very little water, dries quickly, is mildewproof, and is not affected by most ordinary oils, greases, or cleaning fluids. It is also mothproof. It is sensitive to some chemical fumes, excessive heat, and direct rays of sunlight. Nylon melts and drips when it is subjected to fire. This characteristic requires that precautions be taken when nylon is worn where there is a risk of fire. Melted nylon on the skin can cause the most serious of burns.

NOMEX Fabric

NOMEX is the trade name for a fabric that is used in the construction of flight suits. NOMEX fabric is a high-temperature resistant and inherently flame-retardant synthetic fabric. This fabric has no melt point or drip characteristics when it is subjected to fire. NOMEX material is light in weight, does not support combustion, but begins to char at 700 to 800 F. The fabric, similar to nylon, is abrasion resistant, and is also nonabsorbent.

Duck

This is a comparatively firm, coarse, plainweave, cotton fabric with weight per square yard from 6 to 50 ounces. Duck is frequently called canvas. It is primarily used in the construction of protective covers because of its durability and wearing characteristics.

Rubber and rubberized fabrics are used in the manufacture of exposure suits and flotation equipment because they are watertight. Rubberized materials are susceptible to deterioration if subjected to heat and mildew. Foam rubber is thick and resilient and is used for padding in upholstery and aircraft crash pads.

Leather

Cowhide or horsehide may be used for reinforcing patches where heavy wear occurs. It is used for reinforcing patches for grommets and chafing strips on seat belts. Artificial leather has replaced the natural product, and is used to a large extent for seat pad, crash pad, and upholstery covering.

Vinyl

Vinyl is a plastic material and is used in many instances in the fabric shop. Vinyl is available in various thicknesses, depending on its intended use. It may be used for seat covers or ventilating clothing. The type used for ventilating clothing consists of two layers of flexible vinyl film. Vinyl is vaportight and has a smooth surface. Soap and water can be used to clean it. Do not use ammonia detergents for cleaning because this bleaches the vinyl.

WEBBINGS AND TAPES

You already know that cloth is fabric wider than 12 inches. Any fabric less than 12 inches, from selvage to selvage edge, is called webbing or tape. The dividing line between webbing and tape is determined by the respective weight.

Webbings

The heavier of the two is webbing. Webbing weighs over 15 ounces per square yard and is less than 12 inches wide. As you would expect, webbings are used for the toughest holding and reinforcing jobs. Slings, harnesses, safety belts, reinforcing and securing straps are made of nylon, with a wide variety of tensile strength. The personnel parachute harness has a tensile strength range of 6,000 to 8,700 pounds. Some nylon webbings are of tubular construction, which makes them very strong. Tubular webbings are 1/2 to 1 inch wide, with tensile strengths ranging from 1,000 to 4,000 pounds.

Tapes

In addition to webbings, there are the lightweight tapes of a twill weave construction. You can use tapes for reinforcement on many types of fabric covers. Tapes can weigh up to 15 ounces per square yard. Cloth tapes are woven in the same manner as fabric. Some are bias, which, because of the bias cut or construction, aid the binding of curved edges where stretching qualities are desired. These bias tapes are sometimes referred to as binding tapes.

Velcro tape is commonly used in many shops as a fastening or closing device. Velcro tape consists of two parts-the hook and the pile or loop tape. The hook tape is made of nylon, which consists of a series of small hooks. The nylon pile or loop tape has many small loops. When the two parts of the tape are joined, the hooks engage with the loops holding the two tapes together.