The Gougeon Brothers on Boat Construction - WEST SYSTEM Epoxy

Chapter 16 – Lofting 171
Secure pivot point
Cleats nailed to the floor
trued and leveled with
transit if possible.
Pivot this arm
to tension cable
Figure 16-5 An arrangement for tightening the baseline
cable.
To place the locating cable, we anchor it flush to the
floor at one end with a heavy nail or screw and run it
over cleats to a lever at the other end of the floor. This
lever—a flat board—pivots horizontally on a screw that
passes through it and into the floor, and we anchor the
cable on the underside of the lever between the pivot
and free end. Using the free end as a handle, we then
pull the lever until the cable is in about 500 pounds
tension and nail the free end securely to the floor to
maintain tension. (See Figure 16-5.)
We transfer the location of the cable to the lofting
floor using the small tool in Figure 16-6. This tool is
designed so that the thin ( 1 ⁄32") tongue slips under the
wire without disturbing it and the raised portion butts
into the wire. We put a pencil tick at the end of the
tongue on the lofting, repeating this every few feet.
Station lines: <strong>The</strong> next step is to draw in the station
lines. In laying these out, you will want the first and
last stations about equal distance from the ends of the
lofting floor so that you have some working room at
each end of your lofting. Using a full length steel tape,
mark and label in light pencil all the station points on
the baseline.
We distrust the first inch of a steel tape. To be sure of
accurate measurements, we slide the tape to its 1" mark
and tick the surface at the 5" mark. Retract the tape so
that its 4" mark lines up with the tick on the board.
Everything is again at zero. Some people slide the tape
to the 1" mark and add the inch to all dimensions, but
we have managed to saw things an inch too short too
many times using this system.
Jig for marking baseline
off the cable
Jig
Do not slide the jig along
the wire – just set it lightly
against the wire every foot
or so.
Figure 16-6 A jig or gauge for transferring the baseline to
the lofting board.
Because an accurate lofting depends on the accuracy
with which you lay out the foundation or grid, always
double check grid dimensions before going on to the
next step. It is important to note at this time that you
must lay down all of the grid dimensions, i.e., station
spacing, waterline spacing, buttock spacing, etc.,
exactly as the designer specifies. <strong>The</strong>y might be hard
to scale from the lines drawing, but the designer generally
specifies the distances between all of these lines
somewhere on the plans.
Next, erect the station lines perpendicular to the points
you have marked on the baseline. We use the following
procedure. Construct a perpendicular line at the forward
station, using a bar compass. Work to as high a degree
of accuracy as possible. (See Figure 16-4.) Using the
straightedge, draw the line in ink and extend it a few
inches above the highest point of the boat to be lofted.
Using the square and a pencil, lightly draw the station
line at the opposite end of the lofting. Extend it a few
inches above the boat’s highest point. Measure from the
baseline up these two station lines to the height of the
boat plus a few inches so that you have a point of equal
distance from the baseline on each station line, now, of
course, parallel to the baseline. Starting at the station
line which was geometrically constructed and drawn in
ink, run a steel tape parallel to the string and mark the
locations of the upper points of the station lines.