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 which are commercially available which do a very good job.
Every modeler should have a fixture which 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 wing 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 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, 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.