The Gougeon Brothers on Boat Construction - WEST SYSTEM Epoxy

Chapter 16 – Lofting 183
Perpendiculars are various station perpendiculars
Degree stick
Mark the degrees using the straightedge over the bevel
board. Be sure to note the proper control edge and station
spacing.
Figure 16-12 A master bevel board.
stick that will reach diagonally across the square. Draw
in and label the lines every 5°. Because this bevel board
will be permanent, use a ballpoint pen.
<strong>The</strong> side of the square that goes from the center to the
0° mark will be the baseline. Mark off the station
spacing from the center along the baseline, and at that
point construct a perpendicular line. Draw the line
in, using light pencil. Next, mill a piece of wood that
is longer than the greatest distance between station
sections on the body plan, making it about 1 ⁄8" (3mm)
thick and the exact width of the thickness of planking
that will go on the boat. Lay this stick on your bevel
board so that one edge touches the vertical station line
and the bottom of the stick touches the baseline. Use a
couple of small tacks to hold it in place. Using a small
straightedge, transfer all of the angular lines across the
stick and label them. Be sure to mark the edge of the
stick that is touching the station line.
Take the stick to the body plan as shown in Figure 16-
13. Let’s say you want to deduct the planking thickness
from station 4 at a point on the topsides. Lay the stick
so that its base touches station 4 at this point and it is
projecting at right angles to station 4, and read the
degree line closest to station line 3. Let’s say that it is
20°. Now, place the base of the stick on station 4 so
that it is projecting at right angles and read the degree
line closest to station 5. Let’s say it is 14°. <strong>The</strong> bevel at
that point on station 2 would be the average of these
two readings, 17°. <strong>The</strong> planking thickness deducted
would be the distance measured across the stick at that
17° angle. (Remember, the stick is the same width as
the planking.) Figure 16-14 shows two methods of
subtracting this dimension.
In the first method, we adjust a compass to the distance
and swing an arc off at the labeled bevel as along
stations 1 and 2 in our example. In the second method,
we rotate the stick as we mark the bevels and carefully
tick off the distance using the stick itself as shown on
station 4. <strong>The</strong> measurement, of course, is made at right
angles to the section line.
If two station sections are close to parallel all the way
from the sheer to the keel, you can subtract the same
Bevel from station 4 to station 3 is 20°.
Bevel from station 4 to station 5 is 14°.
Mean angle for these two is 17°.
This would be the bevel for the
station 4 mold at this point.
<strong>The</strong>se bevels should be taken at 90° to the section.
Figure 16-13 Determining mold bevels using a degree stick.