Plate 21
[Figure 78] shows the relation of the spectator to three types of mouldings at A, B, and C. The top or crown (A) is to be seen from below. On a large project the angle of the mouldings with the body of the object should be approximately 45 degrees. The intermediate moulding (B) is lighter than the crown and forms a transitional link that may be seen from either above or below. The lower or base moulding (C) is the widest member of the group as demanded by our sense of stability. It is seen from above. Both for sanitary and structural reasons it projects but slightly from the base. With this grouping in mind it is needless to say that a faulty moulding is one, some portion of which, hidden by intervening moulding, cannot be seen by the spectator.
Architectural design and history have formulated a series of curves, geometric in character, that are regarded as standards in the Industrial Arts. Some of the more prominent curves with their constructions are shown in [Figure 79]. The horizontal divisions are analyzed in accordance with Rules 2a and 2b. It is noticed that the Scotia possesses a curve having the shape of the curve of force, while the two Cymas are saved from monotonous division by means of their reversed curves, illustrating the contrast of direction. The curves of [Figure 80] are excellent lines for freehand practice in designing mouldings and will develop the principle of continuity of curvature or the smooth transition of one curve into the next.
Continuity and Contrast
To keep this continuity from the monotony of a Marcel Wave it is customary to break continuous curves by a fillet such as a straight line as shown at D, [Figures 81], [82], and [83]. When the desired outside diameter has been reached, contrast of direction is necessary and pleasing as a return, [Figure 82]. A glance at the curves so far considered will quickly determine whether they are fitted for the crown, intermediate or base mouldings. A curve should join a straight line with either a tangential or right angle junction, which makes for positiveness in contour expression.
Grouping of Curves
Application of these curves to outline enrichment for wood turning projects is to be governed by a strict adherence to Rules 2a or 2b, otherwise confusion and lack of unity will result. [Figure 83] shows a major grouping under Rule 2b with the subdivisions and minor curves arranged under Rules 2a and 2b. [Figure 84] shows a disregard for rules and the result is an undesirable monotony of contour. If smooth and even continuity of curvature is given considerable thought, together with that for systematic grouping and variety, a pleasing result from wood turning (a much abused but pleasing form of outline enrichment) may be secured. Figures [85] and [86] are illustrations from the industrial field with moulding curves grouped, following and supporting the structural lines of the object. The columns in [Figure 86] might, however, be advantageously reversed.