RIGGING AN OPEN-cockpit biplane’s wings
intimidates some builders. Rigging for cabin aircraft
is simple; apply the techniques you use for low-wing
and high-wing models, ensuring that the top and
bottom wing incidences are the same. With an opencockpit
biplane, that upper wing supported by
cabane struts is more difficult to construct and align
properly.
The cabane struts can be built in a variety of
ways; one of the more popular methods uses music
wire. This technique requires some knowledge of
wire bending, but the advantage is that it survives all
but the most severe crashes.
Correctly rigging the top wing on a typical opencockpit
biplane is determined by four measurements.
• Gap: The vertical distance between the chord
lines of the lower and upper wings. It
determines how high the upper wing sits above
the fuselage and is an essential dimension of
the cabane struts.
• Stagger: The horizontal distance of the top
wing from the bottom wing.
• Incidence: The angle of each wing relative to
a reference line on the fuselage. Sometimes
biplanes’ upper and lower wings have different
incidences. I have obtained the best stability by
putting both wings at 0°.
• Leveling the wings: The vertical distance
between the wings should be the same on the
right and left.
model’s wings straight
Above: Use a block of foam or balsa to make a
fixture that will support the top wing at the proper
distance above the fuselage (gap). Using the rib
template, cut a saddle in the fixture to the shape
of the bottom of the top wing.
42 MODEL AVIATION
Biplane
Rig a
by Roy Day
Right: Use an incidence meter (Robart shown) to
block up the model until the lower wing reads 0°.
You can make the incidence checks at any angle.
Both are the same in this case. The fuselage angle
is measured with a carpenter’s level. If the fuselage
does not match the lower wing’s incidence, shim
the foam block as necessary.
The included photos show a simple method
you can employ to rig your biplane. Start with
the center cabanes. When finished with those,
you can move on to the wing struts, if they are
required.
Have fun! MA
Roy Day
[email protected]
Sources:
K&S Engineering
(773) 586-8503
www.ksmetals.com
Simple steps to get your
Robart Manufacturing
(877) 584-3400
www.robart.com
07sig2.QXD 5/26/09 9:56 AM Page 42
July 2009 43
Above: Drill holes in mounts and mount
the top wing. Check the incidence one
more time. If you drill mounting holes
before cabane struts are completed, any
inaccuracy in the wire bending or
soldering will prevent the struts from
engaging the holes in the plywood mounts.
Photos by the author
Diagonal cabane strut must be soldered
in place to ensure accuracy. With both
cabane struts completed and the top
wing still in position, mark where cabane
struts will be inserted into hard-point
plywood mounts.
Build the cabane struts with music
wire fastened to the bottom of the
top wing with landing gear straps
and nylon bolts. The cabane struts
will terminate in plywood mounts
built into the fuselage. The musicwire
diagonal cabane strut is
patterned using a soft wire (coat
hanger).
Right: Secure cabane struts inside the
fuselage with wheel collars. The wire can
be dressed with wooden fairings or
painted, to match the final scheme and
prevent corrosion.
Place the foam fixture on the fuselage top so that the wing LE
will be at the distance of the stagger, as the plans specify. Tape
the fixture securely to the fuselage.
Use the incidence meter to confirm the wing incidence.
Shim the top wing fixture to get the desired result if
required. The temporary struts are still in place.
Place the top wing on the foam fixture. Measure to ensure that
the right and left distances between the wings are equal, and
brace the wings with a temporary strut. Double-check to make
sure that the wings’ stagger is correct.
model’s wings straight
07sig2.QXD 5/22/09 1:43 PM Page 43
Edition: Model Aviation - 2009/07
Page Numbers: 42,43
Edition: Model Aviation - 2009/07
Page Numbers: 42,43
RIGGING AN OPEN-cockpit biplane’s wings
intimidates some builders. Rigging for cabin aircraft
is simple; apply the techniques you use for low-wing
and high-wing models, ensuring that the top and
bottom wing incidences are the same. With an opencockpit
biplane, that upper wing supported by
cabane struts is more difficult to construct and align
properly.
The cabane struts can be built in a variety of
ways; one of the more popular methods uses music
wire. This technique requires some knowledge of
wire bending, but the advantage is that it survives all
but the most severe crashes.
Correctly rigging the top wing on a typical opencockpit
biplane is determined by four measurements.
• Gap: The vertical distance between the chord
lines of the lower and upper wings. It
determines how high the upper wing sits above
the fuselage and is an essential dimension of
the cabane struts.
• Stagger: The horizontal distance of the top
wing from the bottom wing.
• Incidence: The angle of each wing relative to
a reference line on the fuselage. Sometimes
biplanes’ upper and lower wings have different
incidences. I have obtained the best stability by
putting both wings at 0°.
• Leveling the wings: The vertical distance
between the wings should be the same on the
right and left.
model’s wings straight
Above: Use a block of foam or balsa to make a
fixture that will support the top wing at the proper
distance above the fuselage (gap). Using the rib
template, cut a saddle in the fixture to the shape
of the bottom of the top wing.
42 MODEL AVIATION
Biplane
Rig a
by Roy Day
Right: Use an incidence meter (Robart shown) to
block up the model until the lower wing reads 0°.
You can make the incidence checks at any angle.
Both are the same in this case. The fuselage angle
is measured with a carpenter’s level. If the fuselage
does not match the lower wing’s incidence, shim
the foam block as necessary.
The included photos show a simple method
you can employ to rig your biplane. Start with
the center cabanes. When finished with those,
you can move on to the wing struts, if they are
required.
Have fun! MA
Roy Day
[email protected]
Sources:
K&S Engineering
(773) 586-8503
www.ksmetals.com
Simple steps to get your
Robart Manufacturing
(877) 584-3400
www.robart.com
07sig2.QXD 5/26/09 9:56 AM Page 42
July 2009 43
Above: Drill holes in mounts and mount
the top wing. Check the incidence one
more time. If you drill mounting holes
before cabane struts are completed, any
inaccuracy in the wire bending or
soldering will prevent the struts from
engaging the holes in the plywood mounts.
Photos by the author
Diagonal cabane strut must be soldered
in place to ensure accuracy. With both
cabane struts completed and the top
wing still in position, mark where cabane
struts will be inserted into hard-point
plywood mounts.
Build the cabane struts with music
wire fastened to the bottom of the
top wing with landing gear straps
and nylon bolts. The cabane struts
will terminate in plywood mounts
built into the fuselage. The musicwire
diagonal cabane strut is
patterned using a soft wire (coat
hanger).
Right: Secure cabane struts inside the
fuselage with wheel collars. The wire can
be dressed with wooden fairings or
painted, to match the final scheme and
prevent corrosion.
Place the foam fixture on the fuselage top so that the wing LE
will be at the distance of the stagger, as the plans specify. Tape
the fixture securely to the fuselage.
Use the incidence meter to confirm the wing incidence.
Shim the top wing fixture to get the desired result if
required. The temporary struts are still in place.
Place the top wing on the foam fixture. Measure to ensure that
the right and left distances between the wings are equal, and
brace the wings with a temporary strut. Double-check to make
sure that the wings’ stagger is correct.
model’s wings straight
07sig2.QXD 5/22/09 1:43 PM Page 43