The Gougeon Brothers on Boat Construction - WEST SYSTEM Epoxy

184 First Production Steps
Mark the proper bevels on your
stations in the body plan. Set a
compass for the distance along
the appropriate bevel on your
degree stick. Swing arcs on the
corresponding bevel marks in the
body plan.
While marking the
bevels on the body plan,
carefully rotate the degree stick
until the appropriate bevel on the
stick is perpendicular to the point being
measured. Tick off this dimension on the
body plan. In this example, the stick is
rotated for the 17° bevel on station 4.
Figure 16-14 Two methods for subtracting planking
thickness for.
thickness from the station everywhere. Otherwise, in
just about every hull shape, a calculation made for
planking thickness subtraction about every 6" (150mm)
is adequate. In the few midships sections, you will find
the bevel angle so low that there is very little difference
between true planking thickness and the amount that
has to be subtracted, so most loftsmen don’t bother to
calculate extra planking thickness deduction at very low
bevel angles in the midships sections. You can write the
bevel angles down on the stations at the same time that
you do the planking thickness deduction work. After
you have finished marking the planking thickness
deduction from the station, place a batten on the tick
marks and draw in the reduced station shape.
Subtracting the planking thickness from the stem is
slightly trickier. At this point, if you are subtracting
planking thickness before the longitudinals are faired,
you need to draw a buttock on the body plan 6"
(150mm) from the centerline and pick up the distances
for the forward third of this buttock. <strong>The</strong>n lay it out on
6" Buttock shown in
profile view
Fair the
inner stem profile
Project the 6" buttock up from the
Half breadth plan
Half width of
stem face
Marking stick witness
marks should be 6"
(or same as buttock
spacing)
Figure 16-15 Determining bevels and planking thickness
deduction for the inner stem.
the profile view. If you are subtracting planking thickness
after having faired all the hull lines, this buttock is
most easily projected up off the half breadth plan. (See
Figure 16-15.) Draw a line at right angles from the
profile stem at a point where the stem intersects a waterline,
extending the line aft to the point where it intersects
the profile of the 6" buttock (as in detail A). Draw a line
perpendicular to this first line at the point where it
intersects the buttock. Measure out 6" and make a mark
(as in detail B). At the point where the first line and the
stem intersect, measure out the half width of the stem
at right angles and put a mark (see detail C). Connect
this mark with the upper mark. You should now have a
reasonably accurate sectional view of the stem. If you
lay the stick that is equal in width to the thickness of
the planking beside this line and draw a parallel line,
you will have the shape of the stem minus the planking
thickness. (See detail D.)
Next, fair a profile line for the new inner stem, using
the points established in the stem section views you
have just completed. (See detail E.) If you are
subtracting planking thickness before fairing the hull
lines, you will now have a view of the inner stem to
which you can fair the waterlines.