The Gougeon Brothers on Boat Construction - WEST SYSTEM Epoxy

196 First Production Steps
Figure 17-7 Bonding cheek pieces to a permanent bulkhead.
Figure 17-8 Building a laminated transom with cheek pieces.
We find that it’s best to laminate the cheek piece, bond
it to the bulkhead, and then put both pieces in the setup
as a unit. If the cheek piece is on the changeover
side of the bulkhead, make it larger than the controlling
edge so that there will be enough material after beveling
for a good joint. If possible, however, bond cheek
pieces to the non-control side of a member so they
will be somewhat easier to bevel.
Problems with Rough Fairing
Permanent Frame Items
In the first stage of fairing, where you place the battens
over frames that have not yet been beveled, a difficulty
arises when permanent frames are included in the setup.
When there are mold frames only, all of which are
of the same thickness of material, the non-controlling
edges are all in the same relative position to their corresponding
controlling edges, and so the rough fairing
works rather well. In other words, if the mold material
is, say, 5 ⁄8" (15mm) thick, the non-controlling edges will
all be more or less in line with the controlling edges
and 5 ⁄8" from them. <strong>The</strong> controlling and non-controlling
edges of permanent frames also will be in line with
each other, but they may be something other than 5 ⁄8"
apart. If this is so, fairing over non-control edges is
much more difficult.
<strong>The</strong> solution to this, in the case of pieces that are
thicker than the mold frame material, is to do a preliminary
bevel. Assume, for example, that a bulkhead
together with its cheek piece is 2" (50mm) thick and
that the mold frames are 5 ⁄8" thick. <strong>The</strong> technique is to
draw a line on the bulkhead-cheek piece 5 ⁄8" from its
controlling edge so that the fairing batten can rest on
the line. All of the material being removed is material
that would have to come off eventually anyway, so the
operation will cost little in time. Because the piece will
now have its 5 ⁄8" line exposed to contact with the batten,
you can rough fair the piece in with the rest of the
frames in the set-up.
Pieces that are less than the thickness of the mold frame
materials—and thankfully there will be few, if any, of
them—have to be shimmed to a thickness equal to that
of the other frames. Suppose the piece is 3 ⁄8" (9mm)
while the mold frames are 5 ⁄8" (15mm). You will have
to find or mill something that is 1 ⁄4" (6mm) and apply it
to the piece’s non-controlling edge to build it out to 5 ⁄8"
(15mm). A movable piece, applied with two clamps
that you can shift around as you shift the batten, is
probably the best.
Precoating and Prefinishing
It’s easier to fabricate parts on the shop floor than inside
a hull. Accordingly, we suggest as much prefabrication
as possible. If you are working on a bulkhead, for
example, you might cut and frame companionways
before installing them in the set-up. Precoating with
WEST SYSTEM epoxy, as discussed in Chapter 15, is
usually quicker and the results are generally better than
coating after a piece is in place and the hull planked. Do
all the jobs you can before the piece goes into the set-up.
We have difficulty convincing builders of the merits of
precoating and prefinishing, and we think that this is
because prefinishing does not work in other boatbuilding