Schlingrippen des Gewölbes der Erasmuskapelle im Berliner Schloss - Konzept einer möglichen Rekonstruktion

Winding ribs of the vault of the "Erasmuskapelle" (Erasmus Chapel) in the "Berliner Schloss" (Berlin Castle) - concept for a possible reconstruction.

The winding ribs of vaults from the late Gothic period are double curved ribs, i.e. they follow a circular curvature in the ground plan as well as in the elevation of the arch design. Therefore, they differ from the curve of a cylindrical spiral, or helix, in their height development, where the uncoiled representation of the spiral depicts a linear mathematical function, whilst the twined rib progression also displays an arch-shaped i.e. mathematically degressive function in the uncoiled arch design. The actual vault masonry was carried out directly on top of these ribs, as a spatial mould and temporary construction load transfer. This vault construction technique, which is found especially in Saxon-Bohemian and Bavarian-Austrian areas in the period from the mid-15th century to the second half of the 16th century, is historically derived from only 2 planes and can therefore hardly be explained with our modern-day three dimensional understanding body definition. The derivation of bodies and spatial models from only two planes is comprehensively explained by Albrecht Dürer in his "Unterweysung der Messung mit dem Zirkel und Richtscheit" (Instruction on measurement with compass and ruler), Nurnberg 1525, and by Charles de Bouelles in his "Geometrie Practique" (Practical geometry), Paris 1555, and this knowledge was handed down, thus making it possible today to understand this kind of mathematical geometrical derivation for the workmanship of twined rib vaults, and also to be able to emulate these in the field of historical reconstructions.