The Gougeon Brothers on Boat Construction - WEST SYSTEM Epoxy

Chapter 16 – Lofting 179
To summarize, it is just a matter of drawing a perpendicular
to locate the part which you want to develop
and then picking up distances from the centerline or
baseline to the waterlines, diagonals, and buttocks
which will best help develop the shape of the part.
Developing an Angled
Flat Transom or Bulkhead
If the boat has a flat transom or bulkhead that is at an
angle from the vertical, you have to take a few extra
steps to develop the shape of such a part. Figure 16-10
shows the revolution and development of a flat raked
transom, but it could represent an angled bulkhead for
chainplates or stay tangs.
<strong>The</strong> first step is to locate the intersection of the waterlines,
sheer, and keel with the transom in the profile
view. Using a big square, project the lines at right angles
to the transom profile at the points (a,b,c). It is a good
idea to check the spacing for accuracy at the outboard
end of these projections, which you can do quickly and
easily with a pick-up stick.
Using the transom profile (or a line parallel to it, as in
Figure 16-10) as a centerline, draw in lines to represent
Half breadth dimensions
of waterlines at transom
Figure 16-10 Developing a raked flat transom.
buttocks as they appear in the body plan grid (Buttock
spacing R). You will now have a grid that resembles the
body plan, with the waterline spacing expanded.
Now pick up the distances from the centerline out to
the intersection of the waterlines (and sheer) and the
transom line (A, B, C). <strong>The</strong>se measurements can be
made on either the half breadth (as shown) or body
plan views. Set off the measurements on the corresponding
waterlines in the transom grid (A�, B�, C�).
Next locate the intersections of the buttock lines and
transom in the profile view. Project perpendiculars from
these points on the transom profile out to where they
intersect their corresponding buttocks in the expanded
transom view. Take care to project these points
accurately.
You will now have a set of points (a�, b�, c�, d�, e�, f�,
g�) that describe the true size of the transom. Pick up
the flexible batten that you used for the other station
sections and, using weights or small nails, make it touch
all the points marked on the temporary grid. <strong>The</strong> profile
point at the keel will be where the special station line
intersects the profile line. Slight inaccuracies may have
crept in during the development of the section, in which
Grid spacing of
buttocks lines