Chapter Three Derivatives of Elementary Weaves These weaves are constructed by means of developing elementary weaves. They are derived by changing the floats, number of shift, direction of diagonal lines, from plain, twill, and sateen/satin weaves, and retain their structural features.

The derivatives of elementary weaves include: 3.1 Plain weave derivatives 3.2 Twill weave derivatives 3.3 Satin/sateen derivatives

3.1 Plain weave derivatives. 3.1.1 Rib weaves 3.1.2 Hopsack weaves

3.1.1 Rib weaves Rib weaves are obtained by extending the plain weave in either warp or weft direction. Two kinds of rib weave: warp rib weaves weft rib weaves

1. Warp rib weaves Warp ribs are constructed by inserting several picks in succession into the same shed of an ordinary plain weave. This forms a rib effect across the fabric. (see Fig. 3.1)

● Regular warp rib The same number of picks are inserted in each successive rib, giving the fabric a regular appearance. See Fig. 3.3 This figure shows 3 picks are inserted into each shed

● Irregular warp rib A variation in the width of rib is achieved by inserting different numbers of picks into each successive shed. See Fig. 3.4.

● The warp rib weave diagram is drawn as the following steps. 1) Calculating the weft repeat Ry : Ry = numerator + denominator Ro = 2 2) Drawing the first end according to the fraction given. 3) Drawing the second end opposite to the first one. ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Example: 2/1 irregular warp rib

2. Weft rib weaves Weft ribs are constructed with several warp threads used as one when interlacing with each pick in succession. They form a vertical rib effect in the fabric. (See Fig. 3.5 two ends are used as one)

● Regular weft rib An regular number of ends are used to form each rib, giving the fabric a regular appearance. See Fig.3.6

Irregular weft rib A variation in the width of the rib is achieved by varying the number of ends in each successive rib, as shown in Fig. 3.7.

● The weft rib weave diagram is drawn as following 1) Calculating the warp repeat Ro. Ro = numerator + denominator Ry = 2 2) Drawing the first pick according to the fraction given. 3) Drawing the second pick opposite to the first one. ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Example: 2/1 Irregular weft rib

Notes: Warp rib weaves produce ribs running weft-way Shown in Fig.3.1 Weft rib weaves produce ribs running warp-way Shown in Fig.3.5

● Applications Rib gives a more flexible cloth than plain weave and has many applications. Fabrics are woven in silk, cotton, wool and man-made fibers. Their end uses range from dress fabrics, coats, suits, millinery, ribbons and wedding to upholstery and drapery.

3.1.2 Hopsack weaves Hopsack weaves are constructed by extending the plain weave both vertically and horizontally. See Fig. 3.8

● Regular hopsack Regular hopsacks are woven with the same number of ends and picks and the same yarn count. Equal warp floats exchange with equal weft floats. See Fig. 3.9

● Irregular hopsack Different units of hopsack are arranged in one repeat, with the distribution of warp or weft floats being equal or a predominance of either. See Fig. 3.10

● The irregular hopsack diagram is draw in following steps. 1) Calculating the repeat: Ro = Ry = sum of the numerator +sum of the denominator 2) Drawing the first end and first pick based on the fraction. 3) Based on the first pick, drawing the ends which have warp float same to first end. 4) Drawing the other ends opposite to the first one.

●Applications Hopsack weave fabrics are less stiff than plain due to its fewer intersections, and they have smooth and lustrous surface. Hopsacks are suitable for Apparel, drapery, and are often used for selvedge of other fabrics. Regular hopsack sample Irregular hopsack sample

Home works: Drawing the weave diagrams 1. 2/2 warp rib; 2. 2/2 weft rib; 3. 2/2 hopsack; 4. 3/3 hopsack; 5. warp rib 6. 3/1 weft rib, 7. hopsack 8. hopsack