The Gougeon Brothers on Boat Construction - WEST SYSTEM Epoxy

Chapter 27 – Deck Construction 339
Figure 27-1 Web frames and deck beams in a set-up.
which allows you to develop and maintain overall
fairness as you are approaching the final sheer line
measurement markings.
Once you have established the sheer line, you can
further define the deck by shaping all of the bulkhead
tops to the exact profile. You may have preshaped the
bulkhead deck profiles from the lofting before you
installed them in the set-up. In this case, they only need
to be final faired with the sheer and other bulkheads.
With some boats, especially those with plywood web
frames, it is practical to make the deck beams a unitized
Figure 27-2 <strong>The</strong> same deck beams with stringers in place,
ready for decking.
part of the frame before installing the frame in the setup.
<strong>The</strong>n, after you turn the hull upright, you need
only to final fair the precut deck beams before installing
further framework such as longitudinal stringers. (See
Figure 27-1 and 27-2.)
Developing Deck Camber
All decks are curved, or have camber, so that rain or
boarding seas will easily run off. Usually, this camber is
given in the plans as so many inches of height for the
widest deck beam. Using only these two dimensions,
we usually make up a deck tram to lay out the deck
curvature mechanically for the largest deck beam and
then each succeeding smaller beam. Figure 27-3 shows
this process in detail.
Point C represents the lofted
or projected deck centerline
Hold both battens tight
against the nails at A and B
<strong>The</strong> battens should be long
enough that each batten
will reach from A to B
Pencil
Figure 27-3 Laying out deck camber with a tram. Lay out the
length of the largest deck beam (points A and B) on the lofting
board or other suitable surface, such as a sheet of plywood.
Draw a baseline between the two points for reference.
Measured up from center of this baseline, mark the maximum
deck height (point C). Typically this is 3" to 6" (75mm to
150mm) on a 10' (3m) wide boat. Drive a nail into the board
at Points A and B. Make two straight-edged battens, each at
least 12" (300mm) longer than the widest deck beam. Lay the
battens on the layout with their ends meeting at Point C and
their middles resting against the nails at Points A and B. Join
the two battens at the center with a plywood gusset, leaving a
small gap at the apex for use as a pencil guide. Holding a
pencil in the gap, slide the tram from side to side against the
nails drawing an arc the full width of the beam. As the beam
widths (nail spacing) get smaller, the tram will always draw
arcs in exact proportion to each other.