Plans
Now, for the average modeler interested
in building and flying a 40 inch diameter Geobat.
The 40” diameter model has wing cambers
that are symmetrical above and below the common horizontal plane.
This means the wing cambers and circular leading edge must be
accurately positioned above the work surface and glued in place.
This is probably the most challenging aspect of this design.
The construction booklet covers this procedure and other building
techniques to ensure a solid, symmetrical structure. While GFSA
has taken every effort to describe to the builder how to create
a very precise, clean, balsa structure, it should be noted that
this design is stable even when imperfections are introduced
into the design through builder error or structural damage. This
simply means: if your a horrible craftsman but capable of making
the control surfaces work, you will be able to fly and enjoy
the Geobat by simply adjusting and trimming the control surfaces.
Engine selection is actually determined
more by prop location and prop diameter. The engine must be mounted
so that the prop is positioned safely in the1 1/4” x 11”
rectangular slot, not to close to the forward and rear edges.
This means the length of the engine is very important relative
to prop position. The distance from the firewall to the center
of the rectangular slot is exactly 3 7/16”. The propeller
tips, though, actually are designed to fit flush with the left
and right edges of the slot, which is why 11” prop diameters
are possible.
Larger engines can be used, but modifications
to the plans must be made to ensure that the prop is safely positioned.
Tests were conducted with .40 Fox and .46 O.S. engines using
the present plans.
Carbon fiber is used to create the curved
spars and to reinforce certain parts of the plane.
Two 4 oz. tanks are used because of the
space limitations between the fire wall and leading edge.
The two circular portholes (Plexiglas)
over the tanks allow the modeler to see the tanks filling so
as to prevent fuel from reaching the piston via the exhaust port.
The support ring (the circular structure
located about the spinner) is made of fiberglass. This structure
is optional. It is designed to add strength to the wing and protect
the mid wing ailerons when applying an electric starter to the
spinner.
The landing gear is not shown in the above
photos. The plans require that you bend 5/32" piano wire
for this design.
Can be covered with any type of covering
material although monokote was used for the 40” diameter
prototypes. |
