The Gougeon Brothers on Boat Construction - WEST SYSTEM Epoxy

Chapter 9 – Buying Wood 77
Veneers are graded like lumber into various quality groupings
and the trade standards generally adhered to are those of the
American Plywood Association. <strong>The</strong>re are six veneer grades.
Grade N—Smooth surface “natural finish” veneer; select, all
heartwood or all sapwood; free of open defects; not more
than six repairs (of wood only) per 4' � 8' panel, made
parallel to grain and well matched for grain and color.
Grade A—Smooth, paintable; not more than 18 neatly-made
repairs of the boat, sled or router type, and parallel to grain;
may be used for natural finish in less demanding applications.
Grade B—Solid surface; shims, circular repair plugs and tight
knots to 1" across grain permitted; some minor splits
permitted.
Grade C—Tight knots to 1 1 ⁄2"; knot holes to 1" across
grain and some to 1 1 ⁄2" if total width of knots and knot
holes is within specified limits; both synthetic and wood
repairs permitted; discoloration and sanding defects not
affecting strength permitted; limited splits allowed.
Grade C Plugged—Improved C veneer with splits
limited to 1 ⁄8" in width, and knot holes and borer holes
limited to 1 ⁄4" � 1 ⁄2"; some broken grain; synthetic repairs
permitted.
Grade D—Knots and knot holes to 2 1 ⁄2" width across grain and
up to 3" within specified limits; limited splits permitted.
Figure 9-3 Veneer grades for plywood panels manufactured
in the United States.
Grading and marking systems differ from country to
country, so ask questions when you purchase imported
plywood. Most panels brought into the United States
fall into the American Plywood Association’s MARINE
grade, and some are of higher quality. Waterproof
adhesive is usually used in imported plywood, but
you should boil a sample as described above if you
have any doubts.
We do not recommend oriented strand board (OSB) for
anything on or in a boat, but it may be your most costeffective
choice for patterns, molds, and other tooling
applications. It will shrink and swell, so use it carefully.