In order for a model to track
straight on its intended path, the fuselage must be straight, which is to
say that the fuselage contour must be symmetrical about the center reference
line. Many kits provide locking tabs on the formers to maintain the correct
alignment during assembly. This is an effort by the kit manufacturers to
help modelers but this is not always the best solution. If a modeler is
scratch building from plans, he needs a way of keeping everything straight.
There are fixtures that are commercially available that do a very good
job. Every modeler should have a fixture that helps in construction of a
wide variety of fuselage styles and sizes.
The fuselage jig that is shown
here is easy to build from readily available materials using common tools.
The skills required to construct this fuse jig are well within those of many
beginners. It is easy to assemble and use and works with any fuselage that
has relatively flat sides.
Bill of Materials
Materials listed are for one (1) complete assembly
3/4" x 12" x 48" Plywood
1/8" x 3 3/4" x 4" Hardboard
1/4" x 1/2" x 3 3/4" Plywood
1/4-20 X 5" Carriage Bolt
1/4" Flat Washer
1/4-20 Wing nut
Construction begins with obtaining
the materials required. There is nothing critical about the items listed.
A straight, flat 1 x 12 board can be substituted for the 3/4" plywood base.
The clamping bars can be made of 1/8" plywood instead of hardboard.
The stock pieces are first
cut to length. The ¼" holes for the carriage bolts are drilled in the
base plate. The working surface of the base plate is sanded with 320-grit
sandpaper and finished if desired. The guide lines are then applied. Any
desired method can be used. The recommended method is to use a Sharpie Extra
Fine Point permanent marker to draw the lines. Inserting the carriage bolts
through the appropriate holes completes the construction of the base plate.
The pieces for the side clamps
are cut next. It is recommended that these pieces be cut on a table saw
that has a rip fence so that each piece will be the same size and all corners
square. The pieces should be glued with a good wood glue such as Titebond
and clamped and left to cure overnight. Foam insulation tape (1/2") can
be added to one of the 3 3/4" edges to protect the balsa fuselage parts during
assembly. Finally, the side clamps are placed over the carriage bolts and
the washers and wing nuts are added and the fuselage assembly fixture is
ready for use.
The fuselage assembly fixture
is relatively simple to use. All fuselage side doublers and motor mounts
should be in place before the assembly is started. The location of the formers
must be marked on the fuselage sides and a vertical centerline is marked
on each former. The side clamps are moved back so that the fuselage parts
can be set in position. The fuselage sides are placed between the side clamps.
The formers are placed in position with the center mark of the former aligned
with the centerline of the base plate and with the formers aligned with the
location mark on the fuselage sides. The side clamps are moved inward so
the fuselage sides contact the formers. The side clamps are adjusted
so that the formers are centered on the base plate and parallel with the
crosswise grid lines of the base plate. If CA is being used to join the
fuselage, it can be applied at this point. Otherwise, the side clamps of
one side only are loosened, glue is applied to the components, which
are then returned to the appropriate position, and then the loose side clamps
are returned to the clamping position. The fuselage can be removed when
the glue has cured sufficiently. It can be left in position while top or
bottom pieces are added to ensure that no warpage occurs during subsequent
steps of construction.
This fixture will greatly
improve the symmetry of the fuselage and can also speed construction.