Подпись: Figure 3.17 Circular forms—inflated gym balls. Photography by Jim Postell, 2006. Inflated therapy balls (gym balls) are simple curvilinear forms (Figure 3.17). Gym balls have neither front nor side, unless implied by surface treatment, seams, or branding logos. They offer a practical, inexpensive, and healthful means of sitting.

Подпись: Figure 3.18 Drawing overlay of PK 9 chair, designed by Poul Kjsrholm (1959-1961), manufactured by Fritz Hansen. Drawing by Mette McLean and Sigurdur Stefansson, DKDS students. Courtesy of Jens Overbye, Lecturer, DKDS, Copenhagen. Подпись: Figure 3.19 PK 9 chair designed by Poul Kjsrholm (1959-1961), upholstered in leather over a fiberglass shell, supported by three brushed stainless steel legs. Photography by Jim Postell, 2006.

Compound curves are curvilinear shapes that bend in two or more directions. Poul Kjsrholm’s PK 9 is composed of a compound curved fiberglass seat cov­ered with leather, with curved steel supports, as seen in the overlay drawings in Figure 3.18. The chair’s pro­file created an exceptional challenge regarding its compound curve in order to apply leather to the chair’s form. The solution came about by making a fiberglass mold and applying the leather over the mold after getting the leather wet and stretch-fitted over a wooden model. The leather then was applied to the fiberglass mold loosely to react to the shifting weight of the user. The side profile was edged with a modest border on the chair’s backside. Designed between 1959 and 1961, the chair has been fabricated by Fritz Hansen since 1982 (Figure 3.19).

Подпись: Figure 3.20 Dondolo rocker, designed by Cesare Leonardi and Franca Stagi (1967), manufactured by Elco-Bellato. 15% inches wide; 69 inches deep; 30% inches high (40 cm wide; 175 cm deep; 78 cm high). Photography: copyright © William A. Yokel, 2005. Cesare Leonardi and Franca Stagi designed the Dondolo rocker in 1967. It is made from molded fiberglass-reinforced polyester strength­ened by incorporating ribbing, and has an unusual curvilinear shape, which relies on the posture and weight of the user to function properly (Figure 3.20).