关键词: 尺度, 模数, 足材, 栱长, 南禅寺大殿

Abstract: The main hall of Nanchan Temple, as an ancient wooden architectural structure, has important historical significance when studying its scale rules. This article provides an explanation of its scale rules based on the Zu-cai modulus unit. It emphasized the importance of the Gong-chang (length of arch) index in scale research, enabling its research potential to be fully realised. Issues such as building bays, rafters, outriggers, corner structures, and facade proportions were comprehensively explained through the bracket length scale.
　　The width, depth, and height of the wooden framework of the main hall could be explained by the combination relationship of the Zu-cai modulus. After scales of various indicators were converted into modular expressions by the Zu-cai modulus, several concise geometric relationships—which were obtained based on plotting in previous studies—could be interpreted in a modular manner.
　　The findings were as follows. On the facade of the main hall, the double-layered square timbers formed two prominent horizontal stripes and this horizontal continuity was protected by the concealed Man-gong (the second horizontal). The scattered San-dou (small bracket) between the upper and lower square timbers, in correspondence to the concealed Man-gong, created a uniform rhythm. The Xiao-dou, which was supported by the concealed wing-shaped arc in Xinjian Bujian, just offset the Man-gong intervals caused by the Xinjian expansion, thus maintaining rhythmic continuity. The widths of each bay, lengths of the (concealed) Man-gong, and the spacing between the San-dou (small brackets) all showed multiple accurate relationships. The configuration of the Ying-gong (facade of brackets and arches) reflected the connection between the length of the arch, spatial scale, and facade image effect. 
　　Because the outer eaves protrude halfway from the Man-gong, the configuration of the above Ying-gong (façade of brackets and arches) could be extended to the façade of the large wooden frame from the left to the right eaves, or to the profile of the large wooden frame from front to rear eaves. This demonstrated that the length of the arch became a fundamental element in the space composition and visual composition of the whole large wooden frame. It also reflected the systematic utility of the Zu-cai modulus system in terms of components, structural relationships, spatial relationships, and visual control.
　　The Zu-cai modulus calculation of space width, rafter length, and pillar height in the main hall of the Nanchan Temple enabled a comparison of the degree of arithmetic fitting with existing points, which demonstrated equal accuracy. Additionally, the control of the Zu-cai modulus agreed with the Dougong scale, frame pillar height, protrusion, and even the basic scale of the entire 3D wooden frame. Furthermore, it agreed with the visual effect of the Ying-gong configuration on the facade, forming a simple large-scale proportional relationship. Since this study presents more structural information about arithmetic and geometric relationships than previous studies, the research conclusions provide a valuable reference on the difference between original data and new measurement data. This study lays a positive and open foundation for follow-up studies.

Key words: scale, modulus, Zu-cai, length of arch, main hall of the Nanchan Temple