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[...] The measurements of the ribs seem to suggest that the curvatures of the upper part of the oval ribs are the same in all of them. That could mean that the upper part of the big diagonal rib could swing backwards, from point 1 to 2 and, that way, on and on up to attain the height of all the boss stones. The pivot point would occur in the tangent point between the upper arc and the lower one; in other words, it is placed at a point where the tas-de-charges reach their highest level. If these comments were correct, the entire vault could be built with only one arc, the central part of the diagonal arc (photo 4).
The figure shows the tas-de-charges‘ volume, whose shape is the result of the cluster of the lower part of the oval ribs, and also, the insertion point of the ovals’ upper part, all of them equal; their different tilting are practically imperceptible (photo 5).
Once determined the geometry of all the ribs, the full scale drawing of the vault, following medieval procedures, was drawn on the wall of the workshop room. This drawing allowed to manage the construction of the vault, to obtain the accurate measurements and to check the right execution of the pieces of which the vault is composed (photo 6, 7).
Due to the standardization of the vault, all voussoirs are alike and, consequently, can be carved using just one bebel: the one built with the curvature of the upper part of the diagonal oval’s rib. Finally, we can see, on the table, the main arc already carved (photo 8, 9). [....]
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