Attached
Grain angle refers to the direction of the wood elements such as fibers relative to the
axis of the tree or longitudinal edges of individual pieces of timber. Grain has shown to
affect strength properties and therefore it affects the utilization of timber for structural
applications.
Experiments were carried out to investigate within tree and between tree variations of
grain angles in Pinus caribaea and Eucalyptus graudis.
Five trees of similar aged Pinus caribaea planted in 1980 and Eucalyptus grandis
planted at 1965 were selected. Specimens were taken from pith to bark at breast height,
20°0 of the total height, 40% of the total height, 60% of the total height, 80% of the total
height both in Pinus caribaea and Eucalyptus grandis . Grain angle and the specific
gravity of the samples were measured. Grain angle was measured using gain scribe;
when the needle of the equipment is pulled along a timber piece, it followed the
direction of the grain.
Grain angle values varied at a broader range ( 2.00
- 3.50
)in Pinus caribaea compared
with Eucalyptus grandis ( 2.20
- 2.80
), indicating the prominent grain angle variation in
softwood timber. Grain angle varied significantly ( p S 0.05) between different height
levels in both Pinus caribaea and Eucalvptus grandis. However the variation of the
grain angle between trees of both Pill us curibaea and Eucalyptus grandis was not
significant (p S 0.05).
Grain angles of all the trees in both in Pinus caribaea and Eucalyptus grandis varied
only at a narrower range (2.0° - 3.5° ). This indicates that utilization of these tree species
i not affected by the grain angle variation.
Grain angle increased from pith towards the bark, and this radial variation pattern was
consistent for all trees of Pinus caribaea and Eucalyptus grandis. This suggest that
there is an inherent of this property that can be associated with cambial aging.
