cambium layer
annular rings
medullary rays
heart wood
0°
30°
45°
90°
has good strength along the panel only
can be spilt in the plane of the panel
has greater impact resistance to blows than ordinary wood
cannot be bent more easily than ordinary wood of same thickness
5%
15%
25%
35%
less than one year
1 to 5 years
5 to 10 years
more than 10 years