SEAMS AND KNOTS

A variety of seams and knots are presented in the following text.

HAND-SEWN SEAMS

This is the age of great technological advancements and man has come to rely heavily on the conveniences that technology provides. As you know, almost everything you do involves the use of a machine. From the housewife with her automatic dishwasher and the computer that pays you regularly twice each month to the sewing machine you use to repair articles made from fabric, technology is involved. Very few people in our society have the opportunity to use hand skills; therefore, they search for hobbies, such as model aircraft building, carpentry, and leather crafts to satisfy this desire.

You are fortunate because your job involves using both hand and machine skills. Very few people get the opportunity to work with raw and finished materials and have creating, fabricating, and repairing as part of their job. In your particular situation, not only do you use your hands for tying knots and packing life rafts, but you also use your hands to take the place of a sewing machine. By now you have seen that sewing is perhaps the most useful skill the fabrication and parachute specialist should develop. Few fabric maintenance jobs are performed without some kind of sewing. Although, from your experience, you know that most sewing is done with a machine; you also know there are occasions when machine sewing is impractical or impossible because the design of the article may be such that using a machine would not meet the seam specification. Not only may some jobs be better done with hand sewing than with a machine, but also hand sewing is specified by technical order for certain jobs.

Some of the hand stitches you will use are basting stitch, running stitch, hidden stitch, overthrow stitch, and baseball stitch. You should use the one that best suits the particular job. To use these stitches properly, you should first become acquainted with the applicable definitions and general procedures.

A stitch is a unit of thread formation. A seam consists of a series of stitches (hand- or machinesewn) joining two or more pieces of material. All seams should possess strength, elasticity, durability, and a good appearance. The strength of a seam depends upon the type of stitch used, type of thread used, number of stitches per inch, tightness of seam, construction of seam, and size and type of needle used. The appearance of a seam depends on how the seam is made. Even though you desire a good appearance, your first considerations should be elasticity, durability, and strength.

The elasticity desired in a seam is determined by the material being sewn. If the material possesses an elastic quality, the seam should also possess this same quality. If the seam does not possess the same elastic quality as the material, the stitches may break when stress is applied. A seam should be as durable as the material it joins. Tightly woven fabrics are more durable and have a smoother finish; therefore, they tend to slide on one another. To prevent this sliding, set the stitches tight and deep enough into the material to reduce wear caused by their rubbing on other surfaces.

When hand sewing cloth, turn under one-half inch of the material as reinforcement and insert the needle through both plies. When hand sewing thick materials, such as leather and felt, do not turn the edges under.

To hand sew any seam, you must know how to prepare for the job. Select the proper needle and thread. Choose a thread that matches the thread of the material as nearly as possible. Use the smallest size needle that allows the thread to pass easily through the eye of the needle. To thread the needle, pass one end of the thread through the eye and continue to pull it through until the ends meet. The resulting double thread should be no longer than an arm's length. Tie a binder's knot at the end of the doubled thread.

For sewing seams that require only one thread, pull only about 6 inches of thread through the eye, and then tie an overhand knot in the other end of the thread. Again, use no more than an arm's length of thread.

The overhand knot is the simplest knot made. It is important because it forms a part of the many other knots. To practice making this knot, get a short piece of cord and make a loop in it. Then pass the end through the loop and pull the loop tight. If two pieces of thread side by side are formed in a loop, the resulting knot is called a binder's knot. This knot is identical to the overhand knot except that two threads are used.

Most permanent hand-sewn seams in fabrics should be locked with two half hitches at intervals of 6 inches. These half hitches prevent any break in the seam from going past an interval. Lock all seams at the end with two half hitches, a square knot, or a surgeon's knot. A half hitch is simply an overhand knot whose loop passes around another item, such as a thread or an edge of material. To tie the square knot, tie a simple overhand knot. You then tie another overhand knot in the opposite direction, locking the first knot. The surgeon's knot is a modified form of the square knot. It is the same as the square knot with the exception of the first overhand knot, which is a double turn. This double turn keeps the cord from slipping while the last overhand knot is made.

Yellow beeswax is applied to hand sewing thread to prevent fraying and untwisting. Use only pure beeswax, since the impurities in other waxes may cause oil or grease spots, which deteriorate the thread. Beeswax preserves cotton thread; be sure to use it.

Other wax used in the survival equipment shop is made up of one part beeswax and one part paraffin. It is blended in a wax melting pot. If you are required to perform the task of waxing an entire spool of thread, place the wax pot on a wide, level surface. Place the electric cord of the wax pot so that you, or other personnel in your section, will not walk into it. Gently lower the thread into the hot, molten wax; don't let the thread rest on the bottom of the pot. How long you keep the thread in the wax pot is determined by the size and type of thread you are using. Follow these directions carefully to prevent the thread from burning or weakening because of overcooking.

When sewing, hold the needle between your thumb, index, and middle fingers. Push it forward with the thimble on your fourth finger. Keep your fourth finger about two-thirds bent. Three fingers are needed to guide the needle accurately and swiftly from right to left. Hold the material in such a manner that you do not tire easily; crossing your legs and resting the material on them is helpful. Never point the needle outward at arm's length, because you may injure a passerby.

Purposes and Characteristics of the Basting Stitch

The basting stitch is used only for holding plies of material together temporarily, before machine sewing. This stitch is particularly helpful when you install a patch to a flight suit or a cover. Basting stitches are removed after making the machine seam.

Two types of needles can be used for basting-either the straight or the creed. Use the curved needle for hard-to-get-at areas, such as basting a patch on a cover; otherwise, the job can be done with a straight needle. Make the basting stitch as follows. Thread the needle with a sufficient length of 16-4 thread, single or waxed. Tie an overhand knot in the end of the single thread. Turn under the material edge one-half inch, unless specified otherwise in the technical order. Make each stitch one-fourth inch in length and one-eighth inch from the folded edge of the material. At the end of the row of basting stitches, lock the last stitch with two half hitches. Cut the thread one-fourth inch from the knot. Figure 10-25 illustrates the formation of the basting stitch.