assume the correct functioning of the cradle. In practice, however, many
cradles “lock up” (because of inadequate clearance, poor construction, or
overgenerous use of glue in assembly), causing the type of damage typi-
cally exhibited by functioning cradled panels—although the damage is
often more severe.Modifying the cradle
The type and amount of stress and damage from the factors discussed
above will determine the degree of intervention required. Decisions about
intervention are made on the basis of experience rather than of analysis. It
may be possible to remove the sliding battens from the cradle safely and,
by observing the change in curvature, make an assessment of the amount
of stress within the panel. The difficulty of removal and the abrupt change
in curvature can make this a hazardous procedure, one requiring consider-
able care and experience. After the removal of the battens, it is important
to monitor the movement of the panel through several cycles of low and
high RH. It may take some days, depending on the RH required, for the
panel to reach an initial equilibrium, such as that shown in Figure 3b.
Some thinned, cradled panels show no signs of obvious damage.
Even if it has caused washboarding, a cradle may not appear to have pro-
moted further damage. It may be sufficient (and, indeed, prudent) to
ensure the free movement and function of the cradle by one ofthe follow-
ing means: removing the sliding battens and sanding them to achieve a
looser fit; reducing the thickness of the battens even further to increase
their flexibility, atechnique that allows the cradle and panel to achieve a
degree of curvature, as seen in Figure 4a–d (the relationship betweenA F U A S 373abcdFigure 4a–d
Side elevations and end views of sliding bat-
tens and cradled panels showing reduction in
thickness by four methods: (a) the battens
relieved on the back face at their tips, a tech-
nique that increases cradle flexibility at the
outer edges; (b) the battens relieved on the
front face at their tips, a technique that
increases their flexibility and allows an imme-
diate unrestrained increase in panel curvature
at the outer edges; (c) the battens slightly
reduced in thickness, a technique that ensures
their free movement and the basic functioning
of the cradle, with very little increase in cradle
flexibility; (d) the battens significantly reduced
in thickness, and the consequent gaps in the
glued members filled with packing spacers, a
technique that increases cradle flexibility.