10
Framing the
Plank-on-Bulkhead Hull
1. Bending Wood
Building a P-O-B hull requires bending
some wood without distorting its
desired position (doing so stresses glue
joints and fasteners). Although the term
steam bent
is used to identify the
process, there are three ways to do it.
Steam bending
: Hold the piece over a
kettle of boiling water and bend. Hold
the wood in position until it cools. It
should remain in that position, but may
spring back slightly.
Soaking
: Submerge the piece in warm
water for several hours. Try adding a lit-
tle household or pure ammonia. This
speeds up the soaking process and
makes the fibers slippery so the wood is
easier to bend. After soaking, hold the
piece in position with a fixture and let it
dry completely.
Soldering iron
: Large soldering irons
with a tubular end are ideal. Clamp the
iron upright in a vise. While the iron
heats, soak the strip of wood in tap
water. Some modelers prefer bending
around the tube near the handle (it's not
as hot), while others use the shank.
Move the strip back and forth against
the iron. Its heat turns water into steam
and drives it into the wood. The trick is
to wait until you feel the wood wanting
to yield before starting the bend. Begin
too soon or apply too much pressure
and the strip will break.
Wood dries rapidly, so take care to avoid
scorching. Resoak and reapply it to the
iron until the desired shape is achieved.
Once the piece is formed, it can go direct-
ly on the model. Because the wood's
memory was permanently altered, it will
never spring back to its former shape,
meaning no stress on any timber or fas-
teners. Spend some time acquainting
yourself with this method and you'll
never bother with fixtures again.
Model Expo sells an electric plank bender
(MS7205). It is designed for controlled heat.
2. Center Keel Assembly
The first step in constructing the hull is
to assemble the three laser-cut center
keel pieces. With a sharp pencil, mark
the reference line and bulkhead stations
on both sides of the center keel. Be criti-
cal and measure from several points on
the plans when marking the reference
line. It is a key to proper alignment and
locates Bulkheads
A
through
Q
.
Lay a sheet of waxed paper or plastic
wrap over a flat building board or table,
and place the center keel pieces on top.
Affix the joints with white or woodwork-
er's glue. Use a steel or aluminum straight-
edge to align the reference line. If neces-
sary, add weights to hold down the parts.
Let the adhesive dry at least overnight,
preferably 24 hours (Figure 1-1).
3. Installing the Keel,
Stem, and Sternpost
Add the keel, stem, and sternpost.
Before installing, taper the stem as
shown on the plans. Align and hold the
pieces with dowels (Figure 1-2).
4. Cutting the Rabbet
The
rabbet
is the glue line separating the
keel, stem, and sternpost from the cen-
ter keel. The
bearding line
is the intersec-
tion of the center keel with the inside of
hull planks. Measure the bearding line's
location from the P-O-B plans, then
mark it on both sides of the center keel.
At the stern and bow, cut a 1/16" deep
rabbet with a #11 hobby knife. Cut on
or slightly above the glue joint. Next,
start the rabbet cut at the bearding line.
Use a 1/8" wide chisel and cut toward
the rabbet. The 1/16" thick hull plank-
ing must lie flush against this cut area.
To judge the angle of the rabbet, posi-
tion a scrap piece of plank against the
keel as you cut. The angle changes near
amidships (Figure 1-3).
5. Installing the Bulkheads
The laser-cut bulkheads include tim-
berheads. These extend above the deck
to form bulwark stanchions. Compare
the bulkheads with the patterns on
Sheet 1, determine which is which, and
label them
A
through
Q
. Test each to
make sure it slides into the correct cen-
ter keel slot. If the fit is too tight, sand
the slot. Bulkheads should fit snugly
with a little tolerance for glue.
STAGE 1
Fig 1-1 Assembling the Center Keel
Fig 1-2 Installing Stem, Keel, and Sternpost
Baseboard (or table)
Add pins or
dowels as required
Center keel
Glue
Glue
Glue joint
let dry 24 hours
Wax paper or plastic wrap
Weight
Straight edge to align
reference line
