The Gougeon Brothers on Boat Construction - WEST SYSTEM Epoxy

322 Later Production Steps
Materials
We often use plywood for interior construction because
of its light weight and excellent strength and stiffness. It
takes much less time to cut parts from large plywood
panels than it does to piece them together from many
small pieces of sawn stock. Most of our interiors have
been built with 1 ⁄4" (6mm) to 1 ⁄2" (12mm) thick ply.
Except for bulkheads in larger boats, there is no reason
to use thicker panels; in many cases, 1 ⁄4" plywood will
work if it has adequate supporting framework. We have
also used much thinner plywood for making sandwich
panels with a honeycomb core.
Nowhere is the use of prefinished plywood more
important than in building interiors. <strong>The</strong> labor hour
savings alone are well worthwhile, and a much higher
quality finish is usually the added bonus. We have
found it beneficial to precoat whole sheets of plywood,
usually on both sides, rather than to prefinish
individual parts. (See Chapter 15.) You can coat large
panels more efficiently and save lots of time in sanding.
Smaller parts usually have to be hand sanded so as not
to sand through the coating around the edges, but you
can machine sand large panels very quickly. <strong>The</strong> disadvantage
of prefinishing whole panels is some waste of
the prefinished panel. However, this must be weighed
against the labor savings. In some situations, it may be
best to cut out the parts first before prefinishing. In all
cases, however, you should attempt to prefinish the
parts prior to installation rather than coat and sand the
finished interior joinery after it has been installed.
When you are sawing parts out of plywood panels,
sawing can chip out the upper face of the plywood
edges, causing some unsightly scars which will show
up in a natural finish. Using a band saw minimizes the
chipping problem because it cuts downward and at a
higher rate of speed. <strong>The</strong> more commonly used saber
saw presents a problem. You can tape over the cutting
line with clear cellophane tape or scribe a line with a
sharp knife to minimize wood chipping. Using a sharp,
hollow-ground saber saw blade with no set is also
helpful. Generally, a precoated panel will not chip as
badly as an uncoated panel.
Measuring
Before moving a completed hull from the set-up, we
always mark a true waterline on its exterior and also, if
possible, at various places on the interior. (When using
the mold method, you might have to use a marked
sheer line as the reference line.) With a clearly marked
exterior waterline, you can turn the hull over and then
reposition it easily on its lines so that the interior layout
can begin.
Before you install any interior items, you must set the
hull on its lines in both the fore and aft and
athwartship dimensions so that proper measurements
can be made. This is true whether the hull is in the
upright or inverted position. With the hull plumb on
its lines, you can use the level as the major tool to
position interior layout dimensions accurately. With the
waterline position known on the inside of the hull, you
can measure all further interior dimensions either up or
down from this reference line. <strong>The</strong> only other dimension
to determine is the fore and aft reference from the
station lines.
Making Templates
Fitting interior parts is one of the more difficult jobs of
boatbuilding. Besides the normal curves that must be
fitted to, a typical interior has numerous obstructions
such as bulkheads, keel, frames, and sheer clamps
which a part must be fitted around. <strong>The</strong> normal
complexity of this problem requires the use of
templates to define the final dimensions for a part most
efficiently. Trying to fit the part itself usually causes too
much waste of material.
If your boat was developed with computer-assisted
design (CAD) software, you may be able to have the
program produce templates for any given points along
the inside of the hull. Better still, a CNC router can be
used to cut the plywood to shape for you. <strong>The</strong> time
saved can be profound, so the method is worth investigating.
If you do not have these pattern-making devices
available, the information below will serve you well.
Any thin material that can be easily shaped is adequate
for template material. We regularly use scrap pieces of
plywood or veneer, which we temporarily fasten
together with staples to quickly fashion a rough
template that is as close to the desired final dimensions