The Gougeon Brothers on Boat Construction - WEST SYSTEM Epoxy

166 First Production Steps
Hull Lines Drawings
<strong>The</strong> lines drawings will show three different views of
the boat. Figure 16-2 shows a simple set of lines. <strong>The</strong>
profile is the shape of the boat from a side view. <strong>The</strong>
half breadth plan is the top view from the deck. <strong>The</strong>
body plan is the end view of the boat from either bow
or stern.
Both the designer’s hull
lines plan and the builder’s
lofting are orthographic
projections of the boat
hull.
Figure 16-1 <strong>The</strong> lines show three different views of the boat.
<strong>The</strong> amateur builder will find the building project much easier
if he takes the time to study the plans and attempts to see the
boat in the lines.
<strong>The</strong>re are four types of lines in the drawings: the station
lines, buttock lines, waterlines, and diagonal lines.
Together they form a three-dimensional grid. Each line
represents an imaginary plane passing through the hull.
Station lines: <strong>The</strong> imaginary planes of the station lines
run vertically and athwartship. <strong>The</strong> shapes of the
stations are shown stacked atop each other in the body
plan view, half on one side of the centerline, half on the
other. Station lines are almost always numbered.
Buttock lines: <strong>The</strong> imaginary planes of the buttocks
pass through the boat vertically, fore and aft. <strong>The</strong> planes
are spaced, generally at regular distances, off the centerplane
that divides the hull in half. <strong>The</strong> centerplane is
seen as the profile.
Waterlines: For these lines, the planes pass through
the hull horizontally, at certain distances from the
baseline.
Diagonal lines: <strong>The</strong> imaginary planes of the diagonals
always run fore and aft, but are neither vertical nor
horizontal. <strong>The</strong> intersection of a diagonal with the
profile plane forms a line that is parallel to and some
specified distance above the baseline. <strong>The</strong> height and
the angle are chosen by the designer to facilitate fairing
of the hull and usually intersect the body plan station
lines at angles as close to 90° as possible.
For any set of lines, in at least two views, the station
lines, buttocks, waterlines, and diagonals are represented
as straight lines, and this forms the grid. On the
third view, these lines are shown as curved or sectional
views which represent the intersection of the plane with
the surface of the hull.
<strong>The</strong> profile view will include the sheer line, keel, and
stem. <strong>The</strong> buttocks appear on the profile view as
section views of the boat in the same plane at specific
distances away from the centerline. In the half breadth
plan appear the deck line and all the waterline sections.
<strong>The</strong> diagonal sections also appear on this view. <strong>The</strong>
body plan is made up of section views of the areas of
the hull that the station lines intersect. <strong>The</strong> section from
the bow to the widest point amidships will show up on
one side of the centerline, and from the stern to the
widest point amidships will be the other side.
Because most boat hulls are symmetrical, you only need
to loft one half of the boat. However, some multihull
designs have asymmetrical hulls, and, in these cases,
obviously, you would have to lay out both sides of the
hull.
<strong>The</strong> Table of Offsets
<strong>The</strong> table of offsets provides the dimensions needed to
loft the hull lines. It is arrived at by the designer by
measuring the hull lines drawings with a scale rule.
Above the table of offsets will be noted the units of
measurement employed, for example, “offsets in feet,
inches and eighths.” A plus or minus will indicate a
measurement slightly over or under that indicated, for
instance, 1 ⁄16". Thus, 1-8-5 in the table in Figure 16-3
would be 1' 8 5 ⁄8". <strong>The</strong> offsets for the profile view will be
shown in heights above baseline or, in some cases,
below baseline. Included in these offsets will be the
profile view of the boat, which would be the keel,
stem, and sheer line, and the profile view of the