The Gougeon Brothers on Boat Construction - WEST SYSTEM Epoxy

202 First Production Steps
Setting Up
<strong>The</strong> process of setting up frames has four objectives: 1)
to locate the controlling edges of the frames over the
corresponding station lines marked on the strongback
or floor, 2) to make the centerlines of the frames
plumb, fore and aft and athwartship, 3) to line up the
centerlines on the frames to the centering cable and 4)
to locate waterlines on the mold frames at specific
heights above the cable.
You either need two spirit levels or one spirit level and
one plumb bob to do a set-up. <strong>The</strong> plump bob and
level method is the more accurate and should be used
on any boat large enough to have accommodations.
With small boats, two levels can be used.
Three-foot (1m) levels are long enough, but you should
check them for accuracy and compensate for any error.
To check a level for horizontal accuracy, place it against
a wall, with the bubble between the reticles, and draw a
line the length of the instrument along its edge. <strong>The</strong>n
turn the level end-for-end and place it back along the
line. If the bubble is still in the reticles, the level is
accurate. If not, move the level until the bubble comes
into position and draw a second line along the edge of
the level. This line will intersect the first and the error
is one half the angle of the intersection. In other words,
if the lines are 1 ⁄4" apart 3' from the intersection, the
error is 1 ⁄8" for 3'. If you continue to use such a level,
write the amount of error and its direction on the
instrument itself. Check vertical accuracy in a similar
manner, but do not turn the instrument end-for-end.
Instead, just flop it over so that one side is against the
wall, and then check it again. If a level has several spirit
tubes, check each one. One or two may be accurate and
you can mask any inaccurate ones.
Some levels have adjustable spirit tubes. To make these
accurate, draw the two lines as above and then adjust
the bubble into the reticles on a line that bisects the
angle formed by the original lines.
Use a straightedge to measure the heights of the mold
frames during set-up. It can be quite light, but it should
not be easily bent. In most cases, 11 ⁄2" � 1 ⁄2" (38mm �
12mm) stock is adequate. <strong>The</strong> straightedge must be
long enough to reach from the highest point in the
set-up to the centering cable. A little excess length is
desirable, but more than an extra 1 ⁄4" (6mm) or
so—however much the cable clears the floor or
strongback —gets in the way as you work.
To set up the heights of the mold frames, you need the
waterlines on the mold frames and the centering cable
on the foundation as reference points. Take all of these
points off the lofting body plan. If you have not drawn
the cable location on the lofting floor, do so now. Place
the straightedge along the centerline of the body plan
and mark it for the cable location and the waterlines.
Because all of the mold frames may not have the same
waterline as a reference point, you need to mark the
straightedge with all the waterlines that come into play.
To set up the first station, clamp the straightedge 1 ⁄8"
(3mm) to the side of and parallel to the centerline of
the mold frame face. <strong>The</strong>n adjust the straightedge up
and down until the appropriate waterline mark on the
straightedge is aligned with the reference waterline on
the frame.
Spring clamps are handy and effective for holding the
straightedge to the frame. Apply the clamps at the
vertex of the frame and at the spall. If the straightedge
is put on the control face, you will have to put a shim
of scrap mold frame material between the straightedge
and the spall as a spacer to hold the straightedge
parallel to the control surface. If the straightedge is put
on the opposing non-control surface, you will need a
shim of scrap spall material to fill a space between the
straightedge and the vertex so that the straightedge is
parallel with the controlling edge.
In Chapter 17 we suggested that you install the spalls
so that their edges are the reference waterline. If this
has been done, recheck the edges for straightness. An
alternative to using the edge of the spall is to stretch
a string, held by spring clamps, across the waterline
marks on the frame and to adjust the straightedge
mark to the string.
Putting up the Frames
In constructing the frames, you have already cut the
legs to a uniform height or marked this distance. When
you set up the frames, the cable and its corresponding
mark on the straightedge will be very close to the same
height as soon as the mold station is set into position.