Construction: Bestetti-Nardi BN.1 - 2012/07

By the late 1930s, Italy held many world aviation records,
most famously the absolute world speed record for
seaplanes with the Macchi MC.72. Yet the country’s
vainglorious dictator, Benito Mussolini, wanted more,
particularly sport airplane records, then held primarily by
Germany.
Engineer Pierre Luigi Nardi designed an unusual twinby
Mark Fineman
[email protected]
The BN.1 uses construction techniques familiar to most
modelers. The propeller blades were made by tracing a
template at an angle on a yogurt container.
fuselage light aircraft to be powered by two inverted Alfa
Romeo 115 engines, built by the Bestetti  rm, and ultimately
to be designated as the Bestetti-Nardi BN.1.
The shoulder-wing, single-spar aircraft was of conventional
construction: primarily plywood with fabric covering. It could
be operated from either of the two cockpits.
Flight tests, which began in 1940, revealed instability that
necessitated redesigning the tail, after which it proved to be
dependable in the air. By that time, World War II had begun
and any hope of making record flights was dashed. After scores
of flights by Bestetti-Nardi, the airplane was handed over to
the military, but proved unsuitable for a military role.
The aircraft was likely destroyed in 1943. The BN.1 carried a
civil color scheme of overall dark blue aft of the firewall, with
aluminum trim. Rudders were the regulation green, white, and
red Italian tricolor.
The BN.1, with its excellent proportions and long nose
moment, is well-suited to a rubber-powered flying model.
The model was created for Flying Aces Club Jumbo Scale
Competition and has slightly more than a 36-inch span.
The construction techniques should be familiar to most
Scale modelers. In some cases, it was necessary to make
educated guesses about various protuberances on the full-scale
airplane, because documentation was limited. Some of the
construction techniques are similar to those of Czech-designed
models, particularly the closely spaced sliced wing ribs, which
produce a strong, but lightweight, structure. Note that the two
fuselages are identical.
Fuselages
The trapezoidal cross-section of the fuselage eventually
tapers to a rectangular one at the tail. The fuselage is flat sided,
with stringers only on the rounded formers, top and bottom.
For each fuselage, make two identical side structures of 3/32-
inch balsa stock. Build one side and then the other directly on
top of the first, separated by plastic kitchen wrap. At this point
in construction, the two sides are glued together only at the
rearmost tail post.
Add the crossmembers G, F, and E, in that order, starting at
the widest part. Refer to the individual cross-section drawings
to measure the crossmembers. Once the basic frame has been
completed, add the top and bottom formers and lay in the 1/16
square stringers.
The nose block was cut from a balsa block constructed of
cross-laminated 1/8-inch sheets for strength and then hollowed
out with a motor tool. The various air intakes on the nose
block were either inset with the motor tool or simulated with
black tissue after the nose block was painted.
Although the nose block was originally glued directly onto
the station A structures, this proved to be impractical because
of the narrow opening and high thrustline. Eventually this
was converted into a removable nose block arrangement using
three pairs of small, rare earth magnets and two alignment
strips (see the plans and accompanying photo).
This arrangement is reliable in operation and allows easy
access to the rubber motor.
Wing and Tail Surfaces
The wingtips, stabilizer tips, and rudder outline are built up
of laminated layers of 1/32 x 1/16-or 1/32 x 1/8-inch balsa. For each
laminated structure, draw or photocopy the innermost line of
the laminations, then transfer or glue this outline to a piece of
heavy card stock and cut along the outline. Coat the cardboard
with wax rubbed on from a candle, which will act as a parting
agent.
The cardboard is securely pinned to the building board
with waxed paper underneath. For each laminated structure
you will need three balsa lamination strips. These are
steamed for 10 to 15 minutes using an ordinary vegetable
steamer within a closed pot, which will make the laminations
pliable.
Brush a thinned mixture of white glue, such as 60/40 glueto-
water, between the laminations, and pin them to the form
with straight pins. Allow these to dry overnight. A laminated
tip can then be removed from the board and carefully
trimmed with a sharp hobby knife or razor.
The stabilizer is a combination of straight stock and
laminated tips. You may want to add 1/32-inch thick cap strips
to both sides of the spar and crossmembers for added strength.
The cap strips add little weight and prevent warps.
The vertical tails can be built as shown on the plans and
do not require cap strips. The simulated counterweights will
be described later. The wing consists of a rectangular center
section with tapered outer panels. The dihedral breaks are
between these.
Lay down the LEs, TEs, and wingtips, gluing everything
together except where the outer panels will join the center
section. The sliced rib template, shown on the plans, is glued to
a piece of 1/16-inch thick plywood and carefully cut out.
Making sliced ribs is simple: Cut a rectangle of  rm 1/16-inch
balsa sheet roughly 3 x 61/8 inches. The grain must run parallel
to the longer dimension, which corresponds to the LE to TE
dimension.
Hold the template against the balsa sheet and smoothly cut
along the curved outline. Move the template down 1/16 inch and
cut again. There’s the rib. Repeat until you’ve manufactured at
least 45 ribs. Make a few extra ones, just in case.
With the outline structures pinned in place, glue in
1/16-square sticks against the plans at every rib location. The
three spars for the center section are untapered, but the
outer section spars are tapered to the dimensions given on the
plans.
After the 1/16-square lengths are glued into position, glue the
spars in place. It is important that these be perfectly upright at
right angles to the surface of the building board. Check these
frequently with a small right-angle triangle as you glue and pin
them into position against the 1/16-square lengths.
Now glue in the curved, sliced top strips. For the moment,
leave off the two top strips where the dihedral break occurs.
Where the wing tapers, always shorten the sliced top strips by
cutting away at the TE of the top strips, never from the LE.
This goes together quickly. When everything has thoroughly
dried, leave the center section in place, but remove the tapered
outer panels from the building board. Raise the tip of one
outer panel 2 inches above the building board and run a long,
straight sanding stick across the LEs, TEs, and spars.
Carefully sand in the correct dihedral angle so that the outer
panel will properly join with the center section. Repeat this
procedure with the other outer wing panel. When the outer
panels are raised the requisite 2 inches, they should align
perfectly with the edges and spars of the  at center section.
They can now be glued into place and curved top strips can be
added. It is a good idea to add triangular gussets to reinforce
the wing joint.
Covering and Assembly
Each of the  nished structures is covered with dark blue
tissue except for the front of each fuselage (former D
forward) and the rudder of the vertical tail surfaces. Shrink
the tissue with a mist of rubbing alcohol.
Apply two coats of clear nitrate dope or lacquer. The
rudders are left white so that strips of green and red tissue
can be doped over them to create the tricolor rudder stripes.
A small House of Saxony shield insignia is glued to the outer
white stripes.
The white forward fuselage and the nose block should
be misted with a coat of light gray dope. If you engrave the
engine inlets into the nose blocks, increase the illusion of
depth with black paint or tissue inside the inlets.
Photos show no conventional exhaust pipes, but rather
an arrangement of  ve shutters on each side of the engines.
Sometimes these appeared open in the photographs and
sometimes they were closed. My model simulated closed
engine shutters with strips of heavy paper sprayed the same
gray color, glued to the tissue as shown on the plans.
Small structures, perhaps counterweights, also appear in
drawings and pictures of the airplane and are simulated on the
model with black or silver paper cutouts folded over .010 music
wire that is carefully inserted into the tail structures and glued
in place. The tail skids are made of  ne music wire and scrap.
Assembly
Carefully align the fuselages with the wing. Check and
double-check that they are in the correct locations and that
everything is square. Glue the fuselages in place against
the wing. The headrest is made of hollowed balsa or foam,
smoothly sanded and painted to match the blue fuselages.
A headrest is glued in place on top of former H. Now the
canopies can be added. The cockpit side formers are delicate
1/16-sheet structures that are glued in place atop the wing,  ush
with the headrest.
Attach black tissue to the top of the wing between the side
formers to give the cockpit area greater depth. The canopy
frames can be laminated, much as the flying surface tips were,
or they can be bent from bamboo.
Glue the three canopy frames in their proper locations along
the canopy side formers. Create most of the canopy with thin
acetate sheets glued to the canopy frames. Only the front
section of the canopy has a compound curve that requires the
piece to be plunged or vacuum-formed.
A single main wheel on each fuselage is depicted in the
retracted position. I created a single wheel, turned on a drill,
from which sections were cut to represent both retracted
wheels. It can be made from hollowed balsa or foam
and painted flat black before being glued to the fuselage
undersides.
Simple wing fillets are made from doped bond paper. To
make the nose block removable, the small, powerful magnets
must be carefully located and recessed flush with the surfaces
to be mated. They can then be glued in position.
The spinners were turned on a drill. You may want to use
commercial plastic propellers, but built-up or carved ones are
more efficient. The propellers are made to turn in opposite
directions (toward the wingtips, viewed from the front) in
order to minimize torque effects.
The blades were cut from plastic yogurt containers, affixed
to bamboo spars, and then glued into a brass tube. That tube
had first been drilled at its center to accept a smaller-diameter
brass tube with a simple ramp-type freewheeler filed into it.
The tubes were soldered together.
The angle of the spar-and-blade assembly, relative to the
cross-tube, was determined with a simple fixture, and then
cemented permanently into the cross-tube with instant CA
glue. The ramp freewheeler pokes through the end of the
spinner. It works well.
Flying
Other than a slight amount of downthrust and nose
weight, the model required no additional adjustments. Its first
flight was more than a minute! Its second flight—nearly 11/2
minutes—was at the 2010 FAC Nationals, which was good
enough for second place in the Jumbo Scale event.
My BN.1 took first place at the Fall Wawayanda, New York,
meet. Each motor currently consists of two 28-inch loops of
1/8-inch FAI Super Sport rubber, but a more robust motor of
three loops of 3/32 is planned for next flying season. The weight
of the airframe, without rubber, is 75 grams.

By the late 1930s, Italy held many world aviation records,
most famously the absolute world speed record for
seaplanes with the Macchi MC.72. Yet the country’s
vainglorious dictator, Benito Mussolini, wanted more,
particularly sport airplane records, then held primarily by
Germany.
Engineer Pierre Luigi Nardi designed an unusual twinby
Mark Fineman
[email protected]
The BN.1 uses construction techniques familiar to most
modelers. The propeller blades were made by tracing a
template at an angle on a yogurt container.
fuselage light aircraft to be powered by two inverted Alfa
Romeo 115 engines, built by the Bestetti  rm, and ultimately
to be designated as the Bestetti-Nardi BN.1.
The shoulder-wing, single-spar aircraft was of conventional
construction: primarily plywood with fabric covering. It could
be operated from either of the two cockpits.
Flight tests, which began in 1940, revealed instability that
necessitated redesigning the tail, after which it proved to be
dependable in the air. By that time, World War II had begun
and any hope of making record flights was dashed. After scores
of flights by Bestetti-Nardi, the airplane was handed over to
the military, but proved unsuitable for a military role.
The aircraft was likely destroyed in 1943. The BN.1 carried a
civil color scheme of overall dark blue aft of the firewall, with
aluminum trim. Rudders were the regulation green, white, and
red Italian tricolor.
The BN.1, with its excellent proportions and long nose
moment, is well-suited to a rubber-powered flying model.
The model was created for Flying Aces Club Jumbo Scale
Competition and has slightly more than a 36-inch span.
The construction techniques should be familiar to most
Scale modelers. In some cases, it was necessary to make
educated guesses about various protuberances on the full-scale
airplane, because documentation was limited. Some of the
construction techniques are similar to those of Czech-designed
models, particularly the closely spaced sliced wing ribs, which
produce a strong, but lightweight, structure. Note that the two
fuselages are identical.
Fuselages
The trapezoidal cross-section of the fuselage eventually
tapers to a rectangular one at the tail. The fuselage is flat sided,
with stringers only on the rounded formers, top and bottom.
For each fuselage, make two identical side structures of 3/32-
inch balsa stock. Build one side and then the other directly on
top of the first, separated by plastic kitchen wrap. At this point
in construction, the two sides are glued together only at the
rearmost tail post.
Add the crossmembers G, F, and E, in that order, starting at
the widest part. Refer to the individual cross-section drawings
to measure the crossmembers. Once the basic frame has been
completed, add the top and bottom formers and lay in the 1/16
square stringers.
The nose block was cut from a balsa block constructed of
cross-laminated 1/8-inch sheets for strength and then hollowed
out with a motor tool. The various air intakes on the nose
block were either inset with the motor tool or simulated with
black tissue after the nose block was painted.
Although the nose block was originally glued directly onto
the station A structures, this proved to be impractical because
of the narrow opening and high thrustline. Eventually this
was converted into a removable nose block arrangement using
three pairs of small, rare earth magnets and two alignment
strips (see the plans and accompanying photo).
This arrangement is reliable in operation and allows easy
access to the rubber motor.
Wing and Tail Surfaces
The wingtips, stabilizer tips, and rudder outline are built up
of laminated layers of 1/32 x 1/16-or 1/32 x 1/8-inch balsa. For each
laminated structure, draw or photocopy the innermost line of
the laminations, then transfer or glue this outline to a piece of
heavy card stock and cut along the outline. Coat the cardboard
with wax rubbed on from a candle, which will act as a parting
agent.
The cardboard is securely pinned to the building board
with waxed paper underneath. For each laminated structure
you will need three balsa lamination strips. These are
steamed for 10 to 15 minutes using an ordinary vegetable
steamer within a closed pot, which will make the laminations
pliable.
Brush a thinned mixture of white glue, such as 60/40 glueto-
water, between the laminations, and pin them to the form
with straight pins. Allow these to dry overnight. A laminated
tip can then be removed from the board and carefully
trimmed with a sharp hobby knife or razor.
The stabilizer is a combination of straight stock and
laminated tips. You may want to add 1/32-inch thick cap strips
to both sides of the spar and crossmembers for added strength.
The cap strips add little weight and prevent warps.
The vertical tails can be built as shown on the plans and
do not require cap strips. The simulated counterweights will
be described later. The wing consists of a rectangular center
section with tapered outer panels. The dihedral breaks are
between these.
Lay down the LEs, TEs, and wingtips, gluing everything
together except where the outer panels will join the center
section. The sliced rib template, shown on the plans, is glued to
a piece of 1/16-inch thick plywood and carefully cut out.
Making sliced ribs is simple: Cut a rectangle of  rm 1/16-inch
balsa sheet roughly 3 x 61/8 inches. The grain must run parallel
to the longer dimension, which corresponds to the LE to TE
dimension.
Hold the template against the balsa sheet and smoothly cut
along the curved outline. Move the template down 1/16 inch and
cut again. There’s the rib. Repeat until you’ve manufactured at
least 45 ribs. Make a few extra ones, just in case.
With the outline structures pinned in place, glue in
1/16-square sticks against the plans at every rib location. The
three spars for the center section are untapered, but the
outer section spars are tapered to the dimensions given on the
plans.
After the 1/16-square lengths are glued into position, glue the
spars in place. It is important that these be perfectly upright at
right angles to the surface of the building board. Check these
frequently with a small right-angle triangle as you glue and pin
them into position against the 1/16-square lengths.
Now glue in the curved, sliced top strips. For the moment,
leave off the two top strips where the dihedral break occurs.
Where the wing tapers, always shorten the sliced top strips by
cutting away at the TE of the top strips, never from the LE.
This goes together quickly. When everything has thoroughly
dried, leave the center section in place, but remove the tapered
outer panels from the building board. Raise the tip of one
outer panel 2 inches above the building board and run a long,
straight sanding stick across the LEs, TEs, and spars.
Carefully sand in the correct dihedral angle so that the outer
panel will properly join with the center section. Repeat this
procedure with the other outer wing panel. When the outer
panels are raised the requisite 2 inches, they should align
perfectly with the edges and spars of the  at center section.
They can now be glued into place and curved top strips can be
added. It is a good idea to add triangular gussets to reinforce
the wing joint.
Covering and Assembly
Each of the  nished structures is covered with dark blue
tissue except for the front of each fuselage (former D
forward) and the rudder of the vertical tail surfaces. Shrink
the tissue with a mist of rubbing alcohol.
Apply two coats of clear nitrate dope or lacquer. The
rudders are left white so that strips of green and red tissue
can be doped over them to create the tricolor rudder stripes.
A small House of Saxony shield insignia is glued to the outer
white stripes.
The white forward fuselage and the nose block should
be misted with a coat of light gray dope. If you engrave the
engine inlets into the nose blocks, increase the illusion of
depth with black paint or tissue inside the inlets.
Photos show no conventional exhaust pipes, but rather
an arrangement of  ve shutters on each side of the engines.
Sometimes these appeared open in the photographs and
sometimes they were closed. My model simulated closed
engine shutters with strips of heavy paper sprayed the same
gray color, glued to the tissue as shown on the plans.
Small structures, perhaps counterweights, also appear in
drawings and pictures of the airplane and are simulated on the
model with black or silver paper cutouts folded over .010 music
wire that is carefully inserted into the tail structures and glued
in place. The tail skids are made of  ne music wire and scrap.
Assembly
Carefully align the fuselages with the wing. Check and
double-check that they are in the correct locations and that
everything is square. Glue the fuselages in place against
the wing. The headrest is made of hollowed balsa or foam,
smoothly sanded and painted to match the blue fuselages.
A headrest is glued in place on top of former H. Now the
canopies can be added. The cockpit side formers are delicate
1/16-sheet structures that are glued in place atop the wing,  ush
with the headrest.
Attach black tissue to the top of the wing between the side
formers to give the cockpit area greater depth. The canopy
frames can be laminated, much as the flying surface tips were,
or they can be bent from bamboo.
Glue the three canopy frames in their proper locations along
the canopy side formers. Create most of the canopy with thin
acetate sheets glued to the canopy frames. Only the front
section of the canopy has a compound curve that requires the
piece to be plunged or vacuum-formed.
A single main wheel on each fuselage is depicted in the
retracted position. I created a single wheel, turned on a drill,
from which sections were cut to represent both retracted
wheels. It can be made from hollowed balsa or foam
and painted flat black before being glued to the fuselage
undersides.
Simple wing fillets are made from doped bond paper. To
make the nose block removable, the small, powerful magnets
must be carefully located and recessed flush with the surfaces
to be mated. They can then be glued in position.
The spinners were turned on a drill. You may want to use
commercial plastic propellers, but built-up or carved ones are
more efficient. The propellers are made to turn in opposite
directions (toward the wingtips, viewed from the front) in
order to minimize torque effects.
The blades were cut from plastic yogurt containers, affixed
to bamboo spars, and then glued into a brass tube. That tube
had first been drilled at its center to accept a smaller-diameter
brass tube with a simple ramp-type freewheeler filed into it.
The tubes were soldered together.
The angle of the spar-and-blade assembly, relative to the
cross-tube, was determined with a simple fixture, and then
cemented permanently into the cross-tube with instant CA
glue. The ramp freewheeler pokes through the end of the
spinner. It works well.
Flying
Other than a slight amount of downthrust and nose
weight, the model required no additional adjustments. Its first
flight was more than a minute! Its second flight—nearly 11/2
minutes—was at the 2010 FAC Nationals, which was good
enough for second place in the Jumbo Scale event.
My BN.1 took first place at the Fall Wawayanda, New York,
meet. Each motor currently consists of two 28-inch loops of
1/8-inch FAI Super Sport rubber, but a more robust motor of
three loops of 3/32 is planned for next flying season. The weight
of the airframe, without rubber, is 75 grams.