A sphere also can be cut into equal meridian sections
called lunes, and these developed as if they were
sections of cylinders (view B).
The surfaces of prisms and cylinders are parallel
elements or elements that can be treated as parallel
elements. Figure 14-41 shows the steps in developing
a rectangular prism. You should refer to it as you read
the following section.
1. To determine the length of all the edges of the
prism, draw the front and top views in
orthographic projection (view A).
2. Draw the development to one side of the front
Figure 14-39.--Surface development. A. Parallel
view so dimensions of vertical elements on that
development. B. Radial development. C. Development
view can be projected to the development (view
cylinders (fig. 14-39, view A). Radial development is
3. Transfer the dimensions of other elements from
for surfaces such as cones and pyramids (view B).
the top view (view C). Mark all bend lines with
Triangulation is for surfaces that do not lend themselves
crosses near their ends to distinguish them from
to either of the other two methods (view C).
Double-curved surfaces, such as a sphere, may be
4. To check the drawing, measure the edges that
developed approximately by the same methods as those
are to join (view D). Such edges must
used for map projecting. A sphere can be cut into
horizontal sections or zones that may be considered and
Figure 14-42 shows the following steps in the
developed as frustrums of cones (fig. 14-40, view A).
development of a truncated hexagonal prism:
Figure 14-41.--Parallel development of a rectangular plane.
Figure 14-40.--Development of double-curved surfaces.