The Gougeon Brothers on Boat Construction - WEST SYSTEM Epoxy

Chapter 9 – Buying Wood 73
board than typically survives commercial planing. Boat
lumber prices are often quoted for rough sawn, with an
extra charge for surfacing.
Quality—What To Look For
<strong>The</strong>re is no formal grading system for boat lumber.
Standard markings and descriptions refer to surface,
dimensions, and sawing techniques, but not to quality.
While it is assumed that only clear, properly sawn
lumber is acceptable for boatbuilding, high-quality
wood commands high prices, creating some incentive
for unscrupulous dealers to substitute lower grades.
<strong>The</strong> best defense against this is to inspect wood pieceby-piece
before buying it and to accept only highquality
lumber. If you order by mail, be sure to deal
with a company that has a reputation for honest
business practices. We have ordered from many firms
and have rarely found wood quality misrepresented.
Some top quality wood is quarter sawn and sold as
vertical grain lumber, labeled VG. Quarter sawn wood
is far superior to slab sawn wood because it has greater
dimensional stability, it is less liable to internal stressing,
and it is easier to machine. Vertical grain stock is easy
to inspect: the end grain can be “read” to determine
overall quality. In a true vertical grain board, growth
rings run perpendicular to the flat surfaces. Lower
quality quarter sawn planks may have rings that run
as much as 45° off the vertical.
You can saw your own vertical grain planks from thicker
stock. See Figure 9-1. Use a table saw to cut 2" or 3"
(50mm or 75mm) stock down to 2" � 2" (50mm �
From flat-sawn stock
Edge grained strips
From vertical-sawn stock
Figure 9-1 Alternate methods for cutting your own vertical
grain planks.
50mm) boards. Turn the squared planks and saw the
faces that show the most consistent vertical grain in the
dimensions you need. Stringers and other boat parts
that are less than 2" thick can often be cut from 2" slab
sawn stock, so they will have vertical grain. For more
information on preparing planking for stripper canoes,
see Chapter 23.
In many boards, general grain direction is not exactly
parallel to board surfaces. With grain run-out, grain
may typically run more or less parallel to the board
and then, marking the spot of a branch in the standing
tree, curve radically toward one end. Grain run-out
is not a serious problem until the angle of difference
between the board and its grain exceeds 4°. Boards with
severe grain run-out should be used for less structurally
demanding parts.
Knots are obvious major flaws. More difficult to deal
with, however, are the radical grain changes within a
board caused by the proximity of a knot in the tree.
Grain that grew within 2" of a knot can vary 20° to
30° from the general run of the grain, and this can lead
to extreme weakening. Look at all four sides to be sure
that you have not missed other grain distortions.
Avoid planks that have combinations of heartwood and
sapwood. <strong>The</strong>se two types of wood dry at different rates
and can set up internal stresses in a board. You can
usually see this situation in distinct color changes, since
heartwood is generally slightly darker than sapwood.
Pith, the wood from the very center of the tree, tends
to have burled grain, which is difficult to work, so avoid
it as well. Some species, such as Douglas fir, are more
likely than others to develop pitch pockets. Pockets that
are large enough to cause significant weakening are
usually plainly visible.
Even with careful selection, some of the planks you buy
will be better than others. When the wood is delivered,
inspect it again and separate it into two or three groups
by quality. We usually identify deck and hull stringers
and other components with high structural requirements
and save the best stock for them. Use lower quality
lumber for items like joining cleats, where grain is not
particularly important. Every boat has many areas that
require short pieces, so saw around flaws and use the
cut-up lumber for them. Careful planning and efficient
use of available lumber are necessary, but it’s possible
to safely use lesser quality wood without making structural
compromises.