The Gougeon Brothers on Boat Construction - WEST SYSTEM Epoxy

246 Hull Construction Methods
of 3 ⁄8" to 1 ⁄2" (9mm to 12mm) plywood, although for
smaller, heavily curved hulls they may be as thin as 1 ⁄4"
(6mm). Our sanding blocks are designed for economical
use of 11" � 71 ⁄2" (279mm � 190mm) sheets of
sandpaper: we cut them in multiples of 11", up to 44"
(1116mm) long. <strong>The</strong> width of the blocks is anywhere
from 3" to 33 ⁄4" (75mm to 95mm) to fit a sheet of
sandpaper cut in half lengthwise, and depends on
whether we want to attach paper to the block with
staples on the edge or with feathering disc adhesive on
the flat area. We prefer to use adhesive because more of
the sandpaper surface is exposed for use and it’s a little
faster to change paper. While a 44" block may not be
necessary in many cases, the 33" (840mm) block is a
minimum for achieving overall fairness on hulls 15'
(4.5m) and up.
If you plan to clear coat your hull, you will want to
avoid any deep sandpaper scratches, which may show
on its surface. When you get to the point where you
seem close to a final fairness, switch over to finer grit
paper. Begin to direct your sanding strokes in the
direction of the grain rather than across it. When you
are satisfied with your work, do final sanding with a
shorter block. Work in the direction of the grain to
remove any cross-grain scratches.
Even within a species of wood, sanding can be done
at different rates. Lower density wood can be sanded
a little easier than higher density wood, and a single
piece of flat grain wood has hard and soft areas, which
can end up rippled after sanding. <strong>The</strong>se factors can
contribute to slight, yet difficult-to-remedy, variations in
final fairing. Continued sanding sometimes only makes
matters worse, as it removes material from softer areas
and leaves slight “dishing” in the wood. When this
happens, the best solution is to sand with sharp paper,
changing it often, and to make liberal use of a block
plane with a sharp, fine-set blade. You can usually
avoid this whole problem, however, by choosing good,
uniform, edge-grain veneers for the last layer of a
laminated hull.
Removing the Hull from the Mold
Before you turn over the hull, make the cradles in which
it will sit. To fit cradles perfectly, cover the hull with
polyethylene and use it as a mold over which to laminate
veneer, plywood, or fiberglass. This is a very good use
of scrap veneer. Form two cradle seats, each 4" to 8"
Figure 21-24 A molded hull being lifted from a ribband mold.
<strong>The</strong> protective plastic sheet can be seen on the stern of the
mold.
Figure 21-25 <strong>The</strong> hull is in a cradle and immediately trued up
with the waterlines. Temporary bracing at the sheer stabilizes
the shape of the hull while interior joinery is installed. <strong>The</strong>
ladder at the open transom provides easy access to the
interior of the hull.