considered in relation to potential stresses, whether a panel is restrained
statically or allowed to move more freely.
Common sense should dictate precautions in handling. People
with experience in panel structural work tend to rely on a “sense of feel”
when handling a panel or judging its strength. This sense is probably a
combination of experience, touch, and a keen attention to and awareness
ofthe physical nature ofthe object. Inexperienced or careless handlers
may be overconfident or, conversely, too cautious.
Therefore, when larger panels are moved, it is better to have at least
one person present who is experienced in handling such objects. Two or
more people are needed to move larger panels any distance. Coordination
is important, because it is difficult to sense and maintain a constant share of
th e weight. A person on one corner of the panel may allow that side to
droop, thereby causing a dangerous bend or twist.
Most wood is much weaker in the cross-grain direction. Strength
in axial tension is up to fifty times greater than in tension perpendicular to
the grain (Tsoumis 1991:162). If a panel is moved toward the horizontal,
its weight should not be supported only at the side-grain edges^16 or only at
the middle of the end-grain edges. In the first situation, the weight causes
sagging of the middle. In the second, the sides sag. In both cases, the panel
must be structurally sound (i.e., no major defects) to withstand cross-grain
bending safely. To support and balance weight better in the stronger axial-
grain direction, greater support should be given along the end-grain edges,
primarily atabout one-quarter to one-third the distance from each corner.
Further support may help decrease stress.
Panels in a vertical position are usually handled by the sides,
which are usually the longitudinal-grain edges. This happens with larger
panels because people must usually stand at the sides to lift. If the panel is
tipped to lie horizontally, then the grip can be shifted to a better position
at the end-grain edges to avoid the bending stresses discussed above.
If it is necessary to move a large panel from one edge to another,
it is safer to lower it to a horizontal position and then to raise it again ontoP A S C L P P 453a
bcFigure 6a–c
Peter Paul Rubens, The Adoration of the Magi,
seventeenth century. Oil on oak panel, 3280 3
2465 mm; original thickness unknown. King’s
College, Cambridge. Front (a); one ofthree
vertical battens of the original auxiliary sup-
port (b); and an original iron cleat (c). Note
the channel cut in the batten (c) to allow
panel movement across the grain (vertically);
the upper horizontal line is a joint. The panel
has been maintained in a large interior space
under relatively stable conditions. Disjoins
along the side edges extend relatively short
distances inward and stop near or at the first
vertical battens. They had been treated with
inserts or bridges. The battens, which are of
relatively small rectangular section, do not
appear to have caused excessive restraint,
since the nailed cleats remain relatively
unaffected.