The Gougeon Brothers on Boat Construction - WEST SYSTEM Epoxy

Mold Frames and Permanent Frames
<strong>The</strong> material in this chapter and the next are related, and reading the two together will help clarify some of
the more complicated concepts presented below. With a few minor exceptions, this chapter is unchanged
from the original edition.
Boat construction begins when lofting is complete. <strong>The</strong>
first steps, building frames for each lofted station and
setting them up on a foundation, are discussed here
and in Chapter 18. Since you may wish to approach
these jobs simultaneously, we recommend that you read
through both chapters before you start. As you do this,
note that most wood composite boats, even very large
ones, are built keel up and sheer down.
Although we refer to station frames and assume that
you are placing your frames along the station lines, you
may in fact use any regularly spaced lines along your
hull. We use station lines because they are already
drawn in the lofting and are therefore convenient. In
cases where a permanent frame is close to a station, you
may use it instead of a station frame and add an extra
mid-station mold frame to support planking. If at any
time in the set-up process you decide to add a mold
frame, draw it into your lofting as you would a station
line. An auxiliary grid with only a few lines is a good
place to do this sort of special work.
<strong>The</strong>re are two basic types of frames. Mold frames are
assembled to make a form over which to bend the
planking or stringers of a mold or hull. Mold frames are
removed from the finished hull and so are sometimes
referred to as temporary or dummy frames. Permanent
frames, on the other hand, are attached to the hull
skin during the manufacturing process. <strong>The</strong>y are incorporated
into the finished hull and are not used to
construct molds. Bulkheads, ribs, and other components
that are installed in the set-up are considered
permanent frames.
Some hulls are built over mold frames only and the
ribs, bulkheads, and other transverse pieces are fitted
and installed afterwards. Other boats are built over
permanent frames only. Quite often, however, combinations
of mold and permanent frames are used. Many
hulls built using WEST SYSTEM ® Brand epoxy and
CHAPTER
17
laminating techniques do not have enough transverse
structural members to constitute a mold and some
temporary mold frames have to be used. We always aim
to build as many transverse elements as practical into
the mold frame set-up. This requires less labor than
installing the items after the hull skin has been formed,
and the results are usually better.
Planning Permanent Frames
With careful planning, you can substitute many permanent
parts for temporary mold frames. Among the
transverse pieces to be permanently installed in a hull
are such things as bulkheads, sides of lockers, supports
for berths, ribs for engine bed support, laminated floors
for through-bolting ballast keels—any pieces that run
athwartship or at right angles to planking or stringers.
Make a list of all such items while your project is still in
the planning stage and judge which ones can reasonably
be jigged into the set-up and how. You will
probably find that few, if any, of the pieces are
positioned on a station line, so you will have to loft
most, if not all, as extra stations. However, they may
have to be lofted anyway, whether you put them into
the set-up or fit them after you lay the planking.
Full bulkheads are probably the easiest parts to include
in a set-up because they outline the entire hull perimeter,
just like a full mold frame. If the bulkhead happens to
be reasonably close to a station, you can omit the mold
frame for that station if you judge that the planking
will be properly supported and will form fairly. If the
bulkhead is more or less dead center between two
stations, then you will probably have to include the
mold frames for both stations.
As you plan permanent frames, give some thought to
jigging design. All pieces in the set-up—permanent or
temporary—will be supported by vertical legs. Your job