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 TM 5-684/NAVFAC MO-200/AFJMAN 32-1082
(2) Loss of strength. Hollow heart exists to
some extent in almost all poles; it may be only from
the butt up, or from the top down, or go all the way
through. The load-supporting ability is reduced in
proportion to the hollow area, just as it is for surface
rot (as shown in figure C-3). However, due to the
location of the affected area, the reduction of
strength in bending is less than for surface rot.
Because it is hidden, the uncertainty as to the ex-
tent of hollow heart may lead to dangerous condi-
4in
tions. If the hollow heart shown in figure C-3 is
combined with the surface deterioration of figure
C-2 (and this does happen), there is no remaining
strength.
Figure C-3. Twelve-inch (300-millimeter) pole with 4-inch (100-
centimeter) radial heart-rot
C-4
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