Registration

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Once the keystones were located in space (perhaps using
a nail as an exact marker, as in Figure 25), the formworks
would be filled in with curved profiles to receive the voussoirs
of the ribs (or in the case of prismatic vaults, the
bricks forming the folds in the vault). If the vault were
designed according to the Prinzipalbogen, the pieces of
the curved profiles could be shaped to the same radius en
masse, and simply cut to the correct length (sweep of arc)
when incorporated into the formwork (Figure 26). Planed
lumber was readily available in Late Gothic times, even
from water-powered sawmills on barges which could be
towed along rivers. In Dr. Wendland’s experience, cutting
these with a hand-axe, which was likely the tool of choice
at the time, posed little difficulty. Furthermore, this formwork
system would have been easily recyclable, carried
from project to project until finally being used for firewood.
Actually building the vault confirmed another hypothesis:
that once the ribs or folds of the vault were defined,
effectively establishing a network of arches, the masonry
vault surface between the ribs could effectively be constructed
freehand. Early during construction, it seemed
as though it might be possible to construct the whole
vault in this way, using the formwork only as a guide—until
the masonry was noted to have settled snugly against
the formwork overnight (Figure 27).
Byera Hadley Travelling Scholarships Journal Series