Civil Engineering Reference
In-Depth Information
Those caused by imperfect manufacture include the following:
Imperfect machining
Wane
Machine burn
Checks and splits from imperfect drying
Heart shakes
(see Figure 2-10) are radial cracks that are wider
at the pith of the tree than at the outer end. This defect is more
commonly found in old trees rather than in young vigorous saplings.
It occurs frequently in hemlock.
STAR SHAKE
HEART SHAKE
WIND OR CUP
SHAKE
ANNUAL LAYERS
BULGING OUTWARD
TO COVER BREAK
LIVE BRANCH
BROKEN BRANCH
Figure 2-10 The causes of some lumber defects are found in
the natural log.
A
wind shake
or
cup shake
is a crack following the line of the
porous part of the annual rings and is curved by a separation of
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