34 MODEL AVIATION
by Roy Day WACO 10
To rig the top wing of a biplane, you need a
jig to hold the wing at the proper incidence
and height above the bottom wing and
position it forward of the lower wing.
I’VE ALWAYS LIKED biplanes,
and I particularly admire those that
WACO built. Years ago I designed
and built a glow-powered model of
the UPF-7. I flew it for many years
and thought it one was of the bestflying
models I had designed. A
construction article of the UPF-7
was published in the February 1995
MA; it’s plans set 778.
A 1920s
classic
for
electric
power
07sig2.QXD_00MSTRPG.QXD 5/24/11 8:18 AM Page 34
July 2011 35
The landing gear is made from music wire and
attached with nylon bolts to the plywood landing
gear plate. Note the openings, which save weight
and provide cooling vents.
The hatch allows ad equate room for th e A123 four-cell
battery or a 3S1P LiPo.
07sig2.QXD_00MSTRPG.QXD 5/24/11 8:34 AM Page 35
Photos by the author
Super magnets, to hold the interplane struts, are mounted
on the top surface of the bottom wing and on the bottom
of the top wing. You can cover them and they will still hold
the struts firmly.
Above right: The top wing has no dihedral so it can be built
flat on your building board. All of the ribs are identical for
both wings, which is a time saver.
The basic truss structure of the fuselage is built from 3/16-
inch-square balsa. Assemble the fuselage upside down,
allowing the firewall to hang over the building board.
After you have built both bottom wing panels, pin one panel down and jig the other panel up 1.6 inches at the tip rib to give 2.5° of
dihedral. Now epoxy the plywood wing brace and clamp it securely.
WACO built a series of open-cockpit and cabin biplanes from the
1920s until World War II. In 1927 the company manufactured the
first model 10: a straight-wing, three-place, open-cockpit design
powered by the 90-horsepower Curtiss OX-5 engine.
More than 1,100 10s were sold in the next three years. And
during that time period, WACO began building variants of the 10
with different engines—mostly radials.
Except for the forward fuselage, which was redesigned to
accommodate the radial power plants, the new airplanes were
identical to the original WACO 10. They were designated the 125,
DSO, ASO, and BSO. The company had found a successful design
and stuck with it.
Also during that time period, WACO built a few aircraft with
tapered wings instead of the straight configuration of the 10 and with
more-powerful engines. Those “taperwings” were popular for
barnstorming at air shows.
The information in this sidebar and the 1927 photo of the WACO
10 were taken from the book Waco Aircraft Production, 1923-1942
by Raymond H. Brandly, published in 1986. MA
Roy Day
[email protected]
WACO 10 Biplane
36 MODEL AVIATION
07sig2.QXD_00MSTRPG.QXD 5/24/11 8:36 AM Page 36
WACO 10
Prepare the firewall for your particular motor mounting before
you glue it in the fuselage.
The cowl is vacuum-formed plastic. It is held to the firewall with
two magnets mounted in a frame around the inside back of the
cowl.
This is my homemade tail wheel, which gives about one half of the
deflection of the rudder. With this arrangement, the shortcoupled
WACO is easy to handle on the runway.
The tail assembly is bolted on or removed with a socket wrench
inserted through an opening in the bottom of the fuselage. The
whole assembly is quite rigid and allows for removal if needed for
adjustment or transport.
Now that the correct positions of the cabanes have been
determined, you can drill their holes in the plywood support blocks.
Type: RC electric sport scale
Skill level: Intermediate builder; intermediate pilot
Wingspan: 44 inches
Wing area: 600 square inches
Length: 30 inches
Weight: 55 ounces
Power system: Himax HC3522-700; three-cell, 2100
mAh li-Poly or four-cell A123 2300 mAh battery
Construction: Balsa and plywood
Finish: UltraCote iron-on film covering
July 2011 37
07sig2.QXD_00MSTRPG.QXD 5/24/11 8:38 AM Page 37
38 MODEL AVIATION
The WACO 10 is somewhat simpler in
design, with nearly identical straight wings and
a truss-design fuselage. This electric-powered
version also flies well and is relatively easy to
build.
CONSTRUCTION
Wings: The top and bottom wings are nearly
identical; they have the same ribs, spars, center
sheeting, and wingtips. However, the span of
the bottom wing is slightly shorter than that of
the top; the bottom has 21/2° of dihedral and
ailerons; the top wing has no dihedral.
Begin by making the 28 ribs. Use
templates of 1/8 plywood with blanks of 1/16
balsa sheet for the ribs. Rough-shape the ribs
with a band saw, hand-sand them to final form,
and cut notches for the spar caps.
Start with either the right or left panel of
the bottom wing. Lay the forward and aft
bottom basswood spar caps and the TE sheet.
Glue the ribs in position.
Adhere the top basswood spar caps and the
LE. Cut the aileron bottom sheet with the three
ribs and add end rib tips.
Add a plywood block for the aileron horn
before sheeting the top of the aileron. Face the
aileron LE and ends with 1/16 balsa sheet. Glue
a balsa fill block for the wing hold-down bolts
before sheeting the top TE.
The interplane wing struts are not
functional; they are held in with magnets. Add
the wing-strut attachment blocks (for magnets)
on the top side of the bottom wing, even with
the top surface.
Glue on the laminated wingtip. Epoxy the
plywood dihedral brace for this panel. For a
stronger and faster build, use one-piece spar
caps (long enough for both panels) and bend
them at the center as required.
Remove the panel from the building board
and add the top and bottom 1/8 x 1/4 subspars.
Block up the completed wing panel 1.6 inches
at the tip rib (which gives the required
dihedral), and fasten the bottom spar caps of
the other panel to your building board.
Build the second panel of the bottom wing
exactly as you did the first. Epoxy the
plywood dihedral brace to the spar of the
second panel.
Before proceeding further, build the aileron
servo supports and string the servo leads
through holes in the ribs to the wing center.
You can now apply the center sheeting, along
with the rib capstrips, the shear webbing, and
the wingtip. After a bit of sanding, you have
completed the bottom wing.
The top wing is easier to construct than the
bottom wing. There is no dihedral, so you can
lay the entire wing flat on your building board.
With the center sheeting, top and bottom, it is
strong enough without a plywood dihedral
brace.
Glue in the ribs on the bottom spar caps.
Add the LE, top spar caps, and subspars.
Sheet the TE, both top and bottom, and add
the wingtips. Don’t forget to put in plywood
attachment blocks for the cabanes on the
bottom of the wing, as shown on the plans.
You also need to add balsa attachment blocks
for the magnets that hold the interplane struts
on the bottom side of the wing.
Before we go further, I have a few words
for you about applying magnets on the WACO
10. Throughout the design I have used 1/4-
inch-diameter, 1/4-inch-long rare earth
neodymium magnets from Amazing Magnets.
For the interplane struts I merely drilled a 1/4-
inch hole in the balsa support blocks and glued
in the magnets with CA.
It is unnecessary to have magnets on the
ends of the struts; simply glue on a small steel
washer to interface with the magnet. Be sure
you don’t use aluminum washers.
In a similar way, these magnets are used to
hold on the cowl and the hatch. They have
been satisfactory and are inexpensive.
You can apply the wing covering directly
over the magnets. They are strong enough to
snap the struts in place even with the covering
there.
Fuselage: The basic truss structure is built
using 3/16 square balsa. Construct the sides
directly over the plans, but leave out the
diagonals until assembly; it’s easier to bend
the sides without them.
The only use of plywood in the fuselage is
for the landing-gear plate, the wing holddown,
a lamination on the firewall, and the
hard points for the cabane supports.
Prepare the firewall (F1) for your particular
motor mount before mounting it to the
fuselage.
Assemble the fuselage structure upsidedown
on your building board, allowing the
firewall to hang over the edge. Cover the
cockpit area with 1/16 sheet, and make the
cutouts using templates from the plans.
The WACO 10 is a three-place airplane,
which explains why the forward cockpit is
larger than the aft. I used 1/8-inch-diameter
rubber tubing from an auto-parts store for the
cockpit coaming.
Build the hatch in place and make
provisions for a forward peg and magnets on
the rear corners. Glue in the plywood supports
for the cabanes, but don’t drill the holes at this
time.
Landing Gear: The basic landing gear is not
difficult to fashion using a wire bender.
However, the strut extending up to the cabane
support blocks is slightly more difficult to
solder at the right angle and proper length.
I learned a trick during the build. Don’t
make the slot for the strut or drill the holes for
the cabanes until you have made those items.
That will ensure that you have an accurate fit.
In the case of the cabane holes, that means you
should wait until you rig the top wing; I will
cover that later.
The WACO 10 is relatively short-coupled,
so it is best to have a tail wheel assembly that
is not directly coupled to the rudder; if it is, the
model might be difficult to steer on takeoff.
I designed the tail wheel assembly using
springs, brass strip, and music wire. It gives
the tail wheel deflection approximately half
that of the rudder. Ground handling is
excellent. You can use a commercial tail wheel
assembly, such as those that Du-Bro sells.
Cowl: This piece is vacuum-formed plastic; I
have used both PETG (clear) and ABS. The
plastic is formed over a balsa pattern called a
plug.
I reinforced the back edge of the finished
07sig2.QXD_00MSTRPG.QXD 5/24/11 8:41 AM Page 38
40 MODEL AVIATION
cowl with a balsa frame where I glued two of
the same magnets I have used elsewhere. You
can obtain cowls from me.
Tail Surfaces: Most builders know the
importance of fabricating lightweight tail
surfaces. For many years I have used a
technique that employs a sheet center core,
false ribs, and doublers.
It’s easy to build any shape of tail. I attach
the vertical and horizontal tails with a single
nylon bolt, which allows them to be removed
for transport or adjustments to the tail; e.g., a
change to the stabilizer incidence.
The vertical and horizontal tails are
aligned with pegs and held firmly in place by
a 10 x 32 nylon bolt inserted through the
bottom of the fuselage and threaded into the
base of the vertical fin.
Rigging the Top Wing: The cabanes are
made from music wire and attached to the top
wing with landing-gear straps and nylon
bolts. I have had the best results with both
wings set at 0° incidence.
Make a fixture from wood or foam that
rests on the top of the fuselage, to position the
top wing at the correct height, angle, and
forward position relative to the bottom wing.
Check this with an incidence meter to ensure
that the top and bottom wings match. Mark
where the cabane ends touch the support
plywood blocks and drill holes there.
Remove the fixture supporting the top
wing, and check the incidence one more time
to be sure it matches the bottom wing. If they
are within 1/2° of each other, you are finished.
Final Touches: I do like to include a pilot
figure; I hate to see a scale model fly without
one.
You can dress up the cockpit with a
photograph of an instrument panel. Scan a
picture of one into your computer and size it
to fit. You can find some pictures of
instrument panels on the Internet.
Add 1/8-inch fairings to the cabanes and
landing-gear struts, to improve their looks.
Paint them your favorite color.
Power System: I chose a 400-watt Himax
HC3522-0700 outrunner brushless motor,
which I purchased from Maxx Products
International. A 300-watt power plant would
have been quite adequate; I wanted the power
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loading to be 70-75 watts per pound. The
Himax is satisfactory power for leisure flight
and some aerobatics, borne out by flight tests.
I could have used a battery of three A123
cells, saving 3 ounces, with a larger propeller,
but the model had insufficient ground
clearance. In addition, to use a three-cell
A123 pack I would choose a motor with
roughly 1,000 kV instead of the 700 kV of the
motor I used.
Using a three-cell Li-Poly battery would
produce essentially the same power as the
four-cell A123 battery that I employed and
save close to 6 ounces in weight. However,
that would likely produce a balance problem,
which would require you to add several
ounces of lead to the firewall.
I have flown using A123 battery packs for
more than a year and prefer them to Li-Poly,
except for in extraordinarily light aircraft. And
there are smaller A123 cells (1100 mAh),
which are lighter. I have yet to try them.
The A123 cells with their metal cases are
rugged, charge faster than their Li-Poly
counterparts, have no safety issues, have more
charge cycles, and cost nearly the same or less
than Li-Polys.
Flight Tests: Before the first flight I had a
few last-minute checks to make in the shop.
The balance was correct with the four-cell
A123 battery pack forward against the
firewall; no lead was needed.
An incidence check of right and left wing
panels showed the right top panel to have a
tad greater incidence (less than 1°) than the
left. That would mean a tendency to turn left,
so I put in a bit of right trim.
I checked the control surfaces for correct
direction, and the amplitude looked all right.
My son, Michael, was visiting at the time,
and I asked him to make the maiden flight.
Beforehand we conducted a range test and
determined that we had no interference.
Michael did some taxi tests on the runway,
and we adjusted the tail wheel to give a
straight run. The 2:1 gearing of the rudder-totail
wheel deflection made for an easy takeoff
run. The WACO climbed out with authority
and required only minor trim adjustments for
straight-and-level flight.
Loops and rolls were easy and stalls were
straight ahead, with no falloffs on the wing.
After a flight of approximately five
minutes, Michael brought the airplane in for a
smooth landing; I was incredibly pleased with
its performance.
If you like biplanes, the WACO 10 will
give you many pleasurable flights. MA
Roy Day
[email protected]
Sources:
Amazing Magnets
(888) 727-3327
www.amazingmagnets.com
Maxx Products International
(800) 416-6299
www.maxxprod.com
Du-Bro
(800) 848-9411
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07sig2.QXD_00MSTRPG.QXD 5/24/11 8:42 AM Page 40
Edition: Model Aviation - 2011/07
Page Numbers: 34,35,36,37,38,40
Edition: Model Aviation - 2011/07
Page Numbers: 34,35,36,37,38,40
34 MODEL AVIATION
by Roy Day WACO 10
To rig the top wing of a biplane, you need a
jig to hold the wing at the proper incidence
and height above the bottom wing and
position it forward of the lower wing.
I’VE ALWAYS LIKED biplanes,
and I particularly admire those that
WACO built. Years ago I designed
and built a glow-powered model of
the UPF-7. I flew it for many years
and thought it one was of the bestflying
models I had designed. A
construction article of the UPF-7
was published in the February 1995
MA; it’s plans set 778.
A 1920s
classic
for
electric
power
07sig2.QXD_00MSTRPG.QXD 5/24/11 8:18 AM Page 34
July 2011 35
The landing gear is made from music wire and
attached with nylon bolts to the plywood landing
gear plate. Note the openings, which save weight
and provide cooling vents.
The hatch allows ad equate room for th e A123 four-cell
battery or a 3S1P LiPo.
07sig2.QXD_00MSTRPG.QXD 5/24/11 8:34 AM Page 35
Photos by the author
Super magnets, to hold the interplane struts, are mounted
on the top surface of the bottom wing and on the bottom
of the top wing. You can cover them and they will still hold
the struts firmly.
Above right: The top wing has no dihedral so it can be built
flat on your building board. All of the ribs are identical for
both wings, which is a time saver.
The basic truss structure of the fuselage is built from 3/16-
inch-square balsa. Assemble the fuselage upside down,
allowing the firewall to hang over the building board.
After you have built both bottom wing panels, pin one panel down and jig the other panel up 1.6 inches at the tip rib to give 2.5° of
dihedral. Now epoxy the plywood wing brace and clamp it securely.
WACO built a series of open-cockpit and cabin biplanes from the
1920s until World War II. In 1927 the company manufactured the
first model 10: a straight-wing, three-place, open-cockpit design
powered by the 90-horsepower Curtiss OX-5 engine.
More than 1,100 10s were sold in the next three years. And
during that time period, WACO began building variants of the 10
with different engines—mostly radials.
Except for the forward fuselage, which was redesigned to
accommodate the radial power plants, the new airplanes were
identical to the original WACO 10. They were designated the 125,
DSO, ASO, and BSO. The company had found a successful design
and stuck with it.
Also during that time period, WACO built a few aircraft with
tapered wings instead of the straight configuration of the 10 and with
more-powerful engines. Those “taperwings” were popular for
barnstorming at air shows.
The information in this sidebar and the 1927 photo of the WACO
10 were taken from the book Waco Aircraft Production, 1923-1942
by Raymond H. Brandly, published in 1986. MA
Roy Day
[email protected]
WACO 10 Biplane
36 MODEL AVIATION
07sig2.QXD_00MSTRPG.QXD 5/24/11 8:36 AM Page 36
WACO 10
Prepare the firewall for your particular motor mounting before
you glue it in the fuselage.
The cowl is vacuum-formed plastic. It is held to the firewall with
two magnets mounted in a frame around the inside back of the
cowl.
This is my homemade tail wheel, which gives about one half of the
deflection of the rudder. With this arrangement, the shortcoupled
WACO is easy to handle on the runway.
The tail assembly is bolted on or removed with a socket wrench
inserted through an opening in the bottom of the fuselage. The
whole assembly is quite rigid and allows for removal if needed for
adjustment or transport.
Now that the correct positions of the cabanes have been
determined, you can drill their holes in the plywood support blocks.
Type: RC electric sport scale
Skill level: Intermediate builder; intermediate pilot
Wingspan: 44 inches
Wing area: 600 square inches
Length: 30 inches
Weight: 55 ounces
Power system: Himax HC3522-700; three-cell, 2100
mAh li-Poly or four-cell A123 2300 mAh battery
Construction: Balsa and plywood
Finish: UltraCote iron-on film covering
July 2011 37
07sig2.QXD_00MSTRPG.QXD 5/24/11 8:38 AM Page 37
38 MODEL AVIATION
The WACO 10 is somewhat simpler in
design, with nearly identical straight wings and
a truss-design fuselage. This electric-powered
version also flies well and is relatively easy to
build.
CONSTRUCTION
Wings: The top and bottom wings are nearly
identical; they have the same ribs, spars, center
sheeting, and wingtips. However, the span of
the bottom wing is slightly shorter than that of
the top; the bottom has 21/2° of dihedral and
ailerons; the top wing has no dihedral.
Begin by making the 28 ribs. Use
templates of 1/8 plywood with blanks of 1/16
balsa sheet for the ribs. Rough-shape the ribs
with a band saw, hand-sand them to final form,
and cut notches for the spar caps.
Start with either the right or left panel of
the bottom wing. Lay the forward and aft
bottom basswood spar caps and the TE sheet.
Glue the ribs in position.
Adhere the top basswood spar caps and the
LE. Cut the aileron bottom sheet with the three
ribs and add end rib tips.
Add a plywood block for the aileron horn
before sheeting the top of the aileron. Face the
aileron LE and ends with 1/16 balsa sheet. Glue
a balsa fill block for the wing hold-down bolts
before sheeting the top TE.
The interplane wing struts are not
functional; they are held in with magnets. Add
the wing-strut attachment blocks (for magnets)
on the top side of the bottom wing, even with
the top surface.
Glue on the laminated wingtip. Epoxy the
plywood dihedral brace for this panel. For a
stronger and faster build, use one-piece spar
caps (long enough for both panels) and bend
them at the center as required.
Remove the panel from the building board
and add the top and bottom 1/8 x 1/4 subspars.
Block up the completed wing panel 1.6 inches
at the tip rib (which gives the required
dihedral), and fasten the bottom spar caps of
the other panel to your building board.
Build the second panel of the bottom wing
exactly as you did the first. Epoxy the
plywood dihedral brace to the spar of the
second panel.
Before proceeding further, build the aileron
servo supports and string the servo leads
through holes in the ribs to the wing center.
You can now apply the center sheeting, along
with the rib capstrips, the shear webbing, and
the wingtip. After a bit of sanding, you have
completed the bottom wing.
The top wing is easier to construct than the
bottom wing. There is no dihedral, so you can
lay the entire wing flat on your building board.
With the center sheeting, top and bottom, it is
strong enough without a plywood dihedral
brace.
Glue in the ribs on the bottom spar caps.
Add the LE, top spar caps, and subspars.
Sheet the TE, both top and bottom, and add
the wingtips. Don’t forget to put in plywood
attachment blocks for the cabanes on the
bottom of the wing, as shown on the plans.
You also need to add balsa attachment blocks
for the magnets that hold the interplane struts
on the bottom side of the wing.
Before we go further, I have a few words
for you about applying magnets on the WACO
10. Throughout the design I have used 1/4-
inch-diameter, 1/4-inch-long rare earth
neodymium magnets from Amazing Magnets.
For the interplane struts I merely drilled a 1/4-
inch hole in the balsa support blocks and glued
in the magnets with CA.
It is unnecessary to have magnets on the
ends of the struts; simply glue on a small steel
washer to interface with the magnet. Be sure
you don’t use aluminum washers.
In a similar way, these magnets are used to
hold on the cowl and the hatch. They have
been satisfactory and are inexpensive.
You can apply the wing covering directly
over the magnets. They are strong enough to
snap the struts in place even with the covering
there.
Fuselage: The basic truss structure is built
using 3/16 square balsa. Construct the sides
directly over the plans, but leave out the
diagonals until assembly; it’s easier to bend
the sides without them.
The only use of plywood in the fuselage is
for the landing-gear plate, the wing holddown,
a lamination on the firewall, and the
hard points for the cabane supports.
Prepare the firewall (F1) for your particular
motor mount before mounting it to the
fuselage.
Assemble the fuselage structure upsidedown
on your building board, allowing the
firewall to hang over the edge. Cover the
cockpit area with 1/16 sheet, and make the
cutouts using templates from the plans.
The WACO 10 is a three-place airplane,
which explains why the forward cockpit is
larger than the aft. I used 1/8-inch-diameter
rubber tubing from an auto-parts store for the
cockpit coaming.
Build the hatch in place and make
provisions for a forward peg and magnets on
the rear corners. Glue in the plywood supports
for the cabanes, but don’t drill the holes at this
time.
Landing Gear: The basic landing gear is not
difficult to fashion using a wire bender.
However, the strut extending up to the cabane
support blocks is slightly more difficult to
solder at the right angle and proper length.
I learned a trick during the build. Don’t
make the slot for the strut or drill the holes for
the cabanes until you have made those items.
That will ensure that you have an accurate fit.
In the case of the cabane holes, that means you
should wait until you rig the top wing; I will
cover that later.
The WACO 10 is relatively short-coupled,
so it is best to have a tail wheel assembly that
is not directly coupled to the rudder; if it is, the
model might be difficult to steer on takeoff.
I designed the tail wheel assembly using
springs, brass strip, and music wire. It gives
the tail wheel deflection approximately half
that of the rudder. Ground handling is
excellent. You can use a commercial tail wheel
assembly, such as those that Du-Bro sells.
Cowl: This piece is vacuum-formed plastic; I
have used both PETG (clear) and ABS. The
plastic is formed over a balsa pattern called a
plug.
I reinforced the back edge of the finished
07sig2.QXD_00MSTRPG.QXD 5/24/11 8:41 AM Page 38
40 MODEL AVIATION
cowl with a balsa frame where I glued two of
the same magnets I have used elsewhere. You
can obtain cowls from me.
Tail Surfaces: Most builders know the
importance of fabricating lightweight tail
surfaces. For many years I have used a
technique that employs a sheet center core,
false ribs, and doublers.
It’s easy to build any shape of tail. I attach
the vertical and horizontal tails with a single
nylon bolt, which allows them to be removed
for transport or adjustments to the tail; e.g., a
change to the stabilizer incidence.
The vertical and horizontal tails are
aligned with pegs and held firmly in place by
a 10 x 32 nylon bolt inserted through the
bottom of the fuselage and threaded into the
base of the vertical fin.
Rigging the Top Wing: The cabanes are
made from music wire and attached to the top
wing with landing-gear straps and nylon
bolts. I have had the best results with both
wings set at 0° incidence.
Make a fixture from wood or foam that
rests on the top of the fuselage, to position the
top wing at the correct height, angle, and
forward position relative to the bottom wing.
Check this with an incidence meter to ensure
that the top and bottom wings match. Mark
where the cabane ends touch the support
plywood blocks and drill holes there.
Remove the fixture supporting the top
wing, and check the incidence one more time
to be sure it matches the bottom wing. If they
are within 1/2° of each other, you are finished.
Final Touches: I do like to include a pilot
figure; I hate to see a scale model fly without
one.
You can dress up the cockpit with a
photograph of an instrument panel. Scan a
picture of one into your computer and size it
to fit. You can find some pictures of
instrument panels on the Internet.
Add 1/8-inch fairings to the cabanes and
landing-gear struts, to improve their looks.
Paint them your favorite color.
Power System: I chose a 400-watt Himax
HC3522-0700 outrunner brushless motor,
which I purchased from Maxx Products
International. A 300-watt power plant would
have been quite adequate; I wanted the power
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It’s back, new and improved. Now capable of 8.4volts,
the new DC-UP can be implemented anywhere in your
Flight System. NEW LED light bar shows voltages from
8.4 down to 4, and read real time.
• Light bar captures lowest voltage in flight.
• 1.25 Farads of Capacitance.
• Brilliant Blue lights above 5 volts and Red below
5 volts.
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Proudly built by us,
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www. f romeco.org
$28.00
Fromeco’s Cricket
NEW from Fromeco. Cricket is a voltage monitoring
device. Meant to be mounted in a conspicuous area on
your Aircraft. LED light bar configured in a half round dial
configuration. Mount in cockpit floor or behind dash for a
realistic gauge look.
• Light bar captures lowest voltage in flight.
• Brilliant Blue lights above 5 volts and Red below
5 volts.
loading to be 70-75 watts per pound. The
Himax is satisfactory power for leisure flight
and some aerobatics, borne out by flight tests.
I could have used a battery of three A123
cells, saving 3 ounces, with a larger propeller,
but the model had insufficient ground
clearance. In addition, to use a three-cell
A123 pack I would choose a motor with
roughly 1,000 kV instead of the 700 kV of the
motor I used.
Using a three-cell Li-Poly battery would
produce essentially the same power as the
four-cell A123 battery that I employed and
save close to 6 ounces in weight. However,
that would likely produce a balance problem,
which would require you to add several
ounces of lead to the firewall.
I have flown using A123 battery packs for
more than a year and prefer them to Li-Poly,
except for in extraordinarily light aircraft. And
there are smaller A123 cells (1100 mAh),
which are lighter. I have yet to try them.
The A123 cells with their metal cases are
rugged, charge faster than their Li-Poly
counterparts, have no safety issues, have more
charge cycles, and cost nearly the same or less
than Li-Polys.
Flight Tests: Before the first flight I had a
few last-minute checks to make in the shop.
The balance was correct with the four-cell
A123 battery pack forward against the
firewall; no lead was needed.
An incidence check of right and left wing
panels showed the right top panel to have a
tad greater incidence (less than 1°) than the
left. That would mean a tendency to turn left,
so I put in a bit of right trim.
I checked the control surfaces for correct
direction, and the amplitude looked all right.
My son, Michael, was visiting at the time,
and I asked him to make the maiden flight.
Beforehand we conducted a range test and
determined that we had no interference.
Michael did some taxi tests on the runway,
and we adjusted the tail wheel to give a
straight run. The 2:1 gearing of the rudder-totail
wheel deflection made for an easy takeoff
run. The WACO climbed out with authority
and required only minor trim adjustments for
straight-and-level flight.
Loops and rolls were easy and stalls were
straight ahead, with no falloffs on the wing.
After a flight of approximately five
minutes, Michael brought the airplane in for a
smooth landing; I was incredibly pleased with
its performance.
If you like biplanes, the WACO 10 will
give you many pleasurable flights. MA
Roy Day
[email protected]
Sources:
Amazing Magnets
(888) 727-3327
www.amazingmagnets.com
Maxx Products International
(800) 416-6299
www.maxxprod.com
Du-Bro
(800) 848-9411
TIRED OF PAYING
$1.29 FOR 6 SCREWS?
Our 4-40x1/2 socket
caps sell for $4.35/100
for alloy steel, or
$6.65/100 stainless, or $7.50/50 aluminum.
For fair prices on sensible quantities of the fasteners
you need for model building, call, write or
fax for our free catalog!
Micro Fasteners 800-892-6917
24 Cokesbury Rd., Suite 2 908-236-8120
Lebanon, NJ 08833 fax 908-236-8721
e-mail: [email protected] Internet: http://microfasteners.com
07sig2.QXD_00MSTRPG.QXD 5/24/11 8:42 AM Page 40
Edition: Model Aviation - 2011/07
Page Numbers: 34,35,36,37,38,40
34 MODEL AVIATION
by Roy Day WACO 10
To rig the top wing of a biplane, you need a
jig to hold the wing at the proper incidence
and height above the bottom wing and
position it forward of the lower wing.
I’VE ALWAYS LIKED biplanes,
and I particularly admire those that
WACO built. Years ago I designed
and built a glow-powered model of
the UPF-7. I flew it for many years
and thought it one was of the bestflying
models I had designed. A
construction article of the UPF-7
was published in the February 1995
MA; it’s plans set 778.
A 1920s
classic
for
electric
power
07sig2.QXD_00MSTRPG.QXD 5/24/11 8:18 AM Page 34
July 2011 35
The landing gear is made from music wire and
attached with nylon bolts to the plywood landing
gear plate. Note the openings, which save weight
and provide cooling vents.
The hatch allows ad equate room for th e A123 four-cell
battery or a 3S1P LiPo.
07sig2.QXD_00MSTRPG.QXD 5/24/11 8:34 AM Page 35
Photos by the author
Super magnets, to hold the interplane struts, are mounted
on the top surface of the bottom wing and on the bottom
of the top wing. You can cover them and they will still hold
the struts firmly.
Above right: The top wing has no dihedral so it can be built
flat on your building board. All of the ribs are identical for
both wings, which is a time saver.
The basic truss structure of the fuselage is built from 3/16-
inch-square balsa. Assemble the fuselage upside down,
allowing the firewall to hang over the building board.
After you have built both bottom wing panels, pin one panel down and jig the other panel up 1.6 inches at the tip rib to give 2.5° of
dihedral. Now epoxy the plywood wing brace and clamp it securely.
WACO built a series of open-cockpit and cabin biplanes from the
1920s until World War II. In 1927 the company manufactured the
first model 10: a straight-wing, three-place, open-cockpit design
powered by the 90-horsepower Curtiss OX-5 engine.
More than 1,100 10s were sold in the next three years. And
during that time period, WACO began building variants of the 10
with different engines—mostly radials.
Except for the forward fuselage, which was redesigned to
accommodate the radial power plants, the new airplanes were
identical to the original WACO 10. They were designated the 125,
DSO, ASO, and BSO. The company had found a successful design
and stuck with it.
Also during that time period, WACO built a few aircraft with
tapered wings instead of the straight configuration of the 10 and with
more-powerful engines. Those “taperwings” were popular for
barnstorming at air shows.
The information in this sidebar and the 1927 photo of the WACO
10 were taken from the book Waco Aircraft Production, 1923-1942
by Raymond H. Brandly, published in 1986. MA
Roy Day
[email protected]
WACO 10 Biplane
36 MODEL AVIATION
07sig2.QXD_00MSTRPG.QXD 5/24/11 8:36 AM Page 36
WACO 10
Prepare the firewall for your particular motor mounting before
you glue it in the fuselage.
The cowl is vacuum-formed plastic. It is held to the firewall with
two magnets mounted in a frame around the inside back of the
cowl.
This is my homemade tail wheel, which gives about one half of the
deflection of the rudder. With this arrangement, the shortcoupled
WACO is easy to handle on the runway.
The tail assembly is bolted on or removed with a socket wrench
inserted through an opening in the bottom of the fuselage. The
whole assembly is quite rigid and allows for removal if needed for
adjustment or transport.
Now that the correct positions of the cabanes have been
determined, you can drill their holes in the plywood support blocks.
Type: RC electric sport scale
Skill level: Intermediate builder; intermediate pilot
Wingspan: 44 inches
Wing area: 600 square inches
Length: 30 inches
Weight: 55 ounces
Power system: Himax HC3522-700; three-cell, 2100
mAh li-Poly or four-cell A123 2300 mAh battery
Construction: Balsa and plywood
Finish: UltraCote iron-on film covering
July 2011 37
07sig2.QXD_00MSTRPG.QXD 5/24/11 8:38 AM Page 37
38 MODEL AVIATION
The WACO 10 is somewhat simpler in
design, with nearly identical straight wings and
a truss-design fuselage. This electric-powered
version also flies well and is relatively easy to
build.
CONSTRUCTION
Wings: The top and bottom wings are nearly
identical; they have the same ribs, spars, center
sheeting, and wingtips. However, the span of
the bottom wing is slightly shorter than that of
the top; the bottom has 21/2° of dihedral and
ailerons; the top wing has no dihedral.
Begin by making the 28 ribs. Use
templates of 1/8 plywood with blanks of 1/16
balsa sheet for the ribs. Rough-shape the ribs
with a band saw, hand-sand them to final form,
and cut notches for the spar caps.
Start with either the right or left panel of
the bottom wing. Lay the forward and aft
bottom basswood spar caps and the TE sheet.
Glue the ribs in position.
Adhere the top basswood spar caps and the
LE. Cut the aileron bottom sheet with the three
ribs and add end rib tips.
Add a plywood block for the aileron horn
before sheeting the top of the aileron. Face the
aileron LE and ends with 1/16 balsa sheet. Glue
a balsa fill block for the wing hold-down bolts
before sheeting the top TE.
The interplane wing struts are not
functional; they are held in with magnets. Add
the wing-strut attachment blocks (for magnets)
on the top side of the bottom wing, even with
the top surface.
Glue on the laminated wingtip. Epoxy the
plywood dihedral brace for this panel. For a
stronger and faster build, use one-piece spar
caps (long enough for both panels) and bend
them at the center as required.
Remove the panel from the building board
and add the top and bottom 1/8 x 1/4 subspars.
Block up the completed wing panel 1.6 inches
at the tip rib (which gives the required
dihedral), and fasten the bottom spar caps of
the other panel to your building board.
Build the second panel of the bottom wing
exactly as you did the first. Epoxy the
plywood dihedral brace to the spar of the
second panel.
Before proceeding further, build the aileron
servo supports and string the servo leads
through holes in the ribs to the wing center.
You can now apply the center sheeting, along
with the rib capstrips, the shear webbing, and
the wingtip. After a bit of sanding, you have
completed the bottom wing.
The top wing is easier to construct than the
bottom wing. There is no dihedral, so you can
lay the entire wing flat on your building board.
With the center sheeting, top and bottom, it is
strong enough without a plywood dihedral
brace.
Glue in the ribs on the bottom spar caps.
Add the LE, top spar caps, and subspars.
Sheet the TE, both top and bottom, and add
the wingtips. Don’t forget to put in plywood
attachment blocks for the cabanes on the
bottom of the wing, as shown on the plans.
You also need to add balsa attachment blocks
for the magnets that hold the interplane struts
on the bottom side of the wing.
Before we go further, I have a few words
for you about applying magnets on the WACO
10. Throughout the design I have used 1/4-
inch-diameter, 1/4-inch-long rare earth
neodymium magnets from Amazing Magnets.
For the interplane struts I merely drilled a 1/4-
inch hole in the balsa support blocks and glued
in the magnets with CA.
It is unnecessary to have magnets on the
ends of the struts; simply glue on a small steel
washer to interface with the magnet. Be sure
you don’t use aluminum washers.
In a similar way, these magnets are used to
hold on the cowl and the hatch. They have
been satisfactory and are inexpensive.
You can apply the wing covering directly
over the magnets. They are strong enough to
snap the struts in place even with the covering
there.
Fuselage: The basic truss structure is built
using 3/16 square balsa. Construct the sides
directly over the plans, but leave out the
diagonals until assembly; it’s easier to bend
the sides without them.
The only use of plywood in the fuselage is
for the landing-gear plate, the wing holddown,
a lamination on the firewall, and the
hard points for the cabane supports.
Prepare the firewall (F1) for your particular
motor mount before mounting it to the
fuselage.
Assemble the fuselage structure upsidedown
on your building board, allowing the
firewall to hang over the edge. Cover the
cockpit area with 1/16 sheet, and make the
cutouts using templates from the plans.
The WACO 10 is a three-place airplane,
which explains why the forward cockpit is
larger than the aft. I used 1/8-inch-diameter
rubber tubing from an auto-parts store for the
cockpit coaming.
Build the hatch in place and make
provisions for a forward peg and magnets on
the rear corners. Glue in the plywood supports
for the cabanes, but don’t drill the holes at this
time.
Landing Gear: The basic landing gear is not
difficult to fashion using a wire bender.
However, the strut extending up to the cabane
support blocks is slightly more difficult to
solder at the right angle and proper length.
I learned a trick during the build. Don’t
make the slot for the strut or drill the holes for
the cabanes until you have made those items.
That will ensure that you have an accurate fit.
In the case of the cabane holes, that means you
should wait until you rig the top wing; I will
cover that later.
The WACO 10 is relatively short-coupled,
so it is best to have a tail wheel assembly that
is not directly coupled to the rudder; if it is, the
model might be difficult to steer on takeoff.
I designed the tail wheel assembly using
springs, brass strip, and music wire. It gives
the tail wheel deflection approximately half
that of the rudder. Ground handling is
excellent. You can use a commercial tail wheel
assembly, such as those that Du-Bro sells.
Cowl: This piece is vacuum-formed plastic; I
have used both PETG (clear) and ABS. The
plastic is formed over a balsa pattern called a
plug.
I reinforced the back edge of the finished
07sig2.QXD_00MSTRPG.QXD 5/24/11 8:41 AM Page 38
40 MODEL AVIATION
cowl with a balsa frame where I glued two of
the same magnets I have used elsewhere. You
can obtain cowls from me.
Tail Surfaces: Most builders know the
importance of fabricating lightweight tail
surfaces. For many years I have used a
technique that employs a sheet center core,
false ribs, and doublers.
It’s easy to build any shape of tail. I attach
the vertical and horizontal tails with a single
nylon bolt, which allows them to be removed
for transport or adjustments to the tail; e.g., a
change to the stabilizer incidence.
The vertical and horizontal tails are
aligned with pegs and held firmly in place by
a 10 x 32 nylon bolt inserted through the
bottom of the fuselage and threaded into the
base of the vertical fin.
Rigging the Top Wing: The cabanes are
made from music wire and attached to the top
wing with landing-gear straps and nylon
bolts. I have had the best results with both
wings set at 0° incidence.
Make a fixture from wood or foam that
rests on the top of the fuselage, to position the
top wing at the correct height, angle, and
forward position relative to the bottom wing.
Check this with an incidence meter to ensure
that the top and bottom wings match. Mark
where the cabane ends touch the support
plywood blocks and drill holes there.
Remove the fixture supporting the top
wing, and check the incidence one more time
to be sure it matches the bottom wing. If they
are within 1/2° of each other, you are finished.
Final Touches: I do like to include a pilot
figure; I hate to see a scale model fly without
one.
You can dress up the cockpit with a
photograph of an instrument panel. Scan a
picture of one into your computer and size it
to fit. You can find some pictures of
instrument panels on the Internet.
Add 1/8-inch fairings to the cabanes and
landing-gear struts, to improve their looks.
Paint them your favorite color.
Power System: I chose a 400-watt Himax
HC3522-0700 outrunner brushless motor,
which I purchased from Maxx Products
International. A 300-watt power plant would
have been quite adequate; I wanted the power
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$68.00
Price in ad does not include Deans
Connector
DC-UP MRK IICricket
Fromeco’s DC-UP Mark II
It’s back, new and improved. Now capable of 8.4volts,
the new DC-UP can be implemented anywhere in your
Flight System. NEW LED light bar shows voltages from
8.4 down to 4, and read real time.
• Light bar captures lowest voltage in flight.
• 1.25 Farads of Capacitance.
• Brilliant Blue lights above 5 volts and Red below
5 volts.
$35.00
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HERE!
WE ARE THE BEST
503.715.0020
www. f romeco.org
$28.00
Fromeco’s Cricket
NEW from Fromeco. Cricket is a voltage monitoring
device. Meant to be mounted in a conspicuous area on
your Aircraft. LED light bar configured in a half round dial
configuration. Mount in cockpit floor or behind dash for a
realistic gauge look.
• Light bar captures lowest voltage in flight.
• Brilliant Blue lights above 5 volts and Red below
5 volts.
loading to be 70-75 watts per pound. The
Himax is satisfactory power for leisure flight
and some aerobatics, borne out by flight tests.
I could have used a battery of three A123
cells, saving 3 ounces, with a larger propeller,
but the model had insufficient ground
clearance. In addition, to use a three-cell
A123 pack I would choose a motor with
roughly 1,000 kV instead of the 700 kV of the
motor I used.
Using a three-cell Li-Poly battery would
produce essentially the same power as the
four-cell A123 battery that I employed and
save close to 6 ounces in weight. However,
that would likely produce a balance problem,
which would require you to add several
ounces of lead to the firewall.
I have flown using A123 battery packs for
more than a year and prefer them to Li-Poly,
except for in extraordinarily light aircraft. And
there are smaller A123 cells (1100 mAh),
which are lighter. I have yet to try them.
The A123 cells with their metal cases are
rugged, charge faster than their Li-Poly
counterparts, have no safety issues, have more
charge cycles, and cost nearly the same or less
than Li-Polys.
Flight Tests: Before the first flight I had a
few last-minute checks to make in the shop.
The balance was correct with the four-cell
A123 battery pack forward against the
firewall; no lead was needed.
An incidence check of right and left wing
panels showed the right top panel to have a
tad greater incidence (less than 1°) than the
left. That would mean a tendency to turn left,
so I put in a bit of right trim.
I checked the control surfaces for correct
direction, and the amplitude looked all right.
My son, Michael, was visiting at the time,
and I asked him to make the maiden flight.
Beforehand we conducted a range test and
determined that we had no interference.
Michael did some taxi tests on the runway,
and we adjusted the tail wheel to give a
straight run. The 2:1 gearing of the rudder-totail
wheel deflection made for an easy takeoff
run. The WACO climbed out with authority
and required only minor trim adjustments for
straight-and-level flight.
Loops and rolls were easy and stalls were
straight ahead, with no falloffs on the wing.
After a flight of approximately five
minutes, Michael brought the airplane in for a
smooth landing; I was incredibly pleased with
its performance.
If you like biplanes, the WACO 10 will
give you many pleasurable flights. MA
Roy Day
[email protected]
Sources:
Amazing Magnets
(888) 727-3327
www.amazingmagnets.com
Maxx Products International
(800) 416-6299
www.maxxprod.com
Du-Bro
(800) 848-9411
TIRED OF PAYING
$1.29 FOR 6 SCREWS?
Our 4-40x1/2 socket
caps sell for $4.35/100
for alloy steel, or
$6.65/100 stainless, or $7.50/50 aluminum.
For fair prices on sensible quantities of the fasteners
you need for model building, call, write or
fax for our free catalog!
Micro Fasteners 800-892-6917
24 Cokesbury Rd., Suite 2 908-236-8120
Lebanon, NJ 08833 fax 908-236-8721
e-mail: [email protected] Internet: http://microfasteners.com
07sig2.QXD_00MSTRPG.QXD 5/24/11 8:42 AM Page 40
Edition: Model Aviation - 2011/07
Page Numbers: 34,35,36,37,38,40
34 MODEL AVIATION
by Roy Day WACO 10
To rig the top wing of a biplane, you need a
jig to hold the wing at the proper incidence
and height above the bottom wing and
position it forward of the lower wing.
I’VE ALWAYS LIKED biplanes,
and I particularly admire those that
WACO built. Years ago I designed
and built a glow-powered model of
the UPF-7. I flew it for many years
and thought it one was of the bestflying
models I had designed. A
construction article of the UPF-7
was published in the February 1995
MA; it’s plans set 778.
A 1920s
classic
for
electric
power
07sig2.QXD_00MSTRPG.QXD 5/24/11 8:18 AM Page 34
July 2011 35
The landing gear is made from music wire and
attached with nylon bolts to the plywood landing
gear plate. Note the openings, which save weight
and provide cooling vents.
The hatch allows ad equate room for th e A123 four-cell
battery or a 3S1P LiPo.
07sig2.QXD_00MSTRPG.QXD 5/24/11 8:34 AM Page 35
Photos by the author
Super magnets, to hold the interplane struts, are mounted
on the top surface of the bottom wing and on the bottom
of the top wing. You can cover them and they will still hold
the struts firmly.
Above right: The top wing has no dihedral so it can be built
flat on your building board. All of the ribs are identical for
both wings, which is a time saver.
The basic truss structure of the fuselage is built from 3/16-
inch-square balsa. Assemble the fuselage upside down,
allowing the firewall to hang over the building board.
After you have built both bottom wing panels, pin one panel down and jig the other panel up 1.6 inches at the tip rib to give 2.5° of
dihedral. Now epoxy the plywood wing brace and clamp it securely.
WACO built a series of open-cockpit and cabin biplanes from the
1920s until World War II. In 1927 the company manufactured the
first model 10: a straight-wing, three-place, open-cockpit design
powered by the 90-horsepower Curtiss OX-5 engine.
More than 1,100 10s were sold in the next three years. And
during that time period, WACO began building variants of the 10
with different engines—mostly radials.
Except for the forward fuselage, which was redesigned to
accommodate the radial power plants, the new airplanes were
identical to the original WACO 10. They were designated the 125,
DSO, ASO, and BSO. The company had found a successful design
and stuck with it.
Also during that time period, WACO built a few aircraft with
tapered wings instead of the straight configuration of the 10 and with
more-powerful engines. Those “taperwings” were popular for
barnstorming at air shows.
The information in this sidebar and the 1927 photo of the WACO
10 were taken from the book Waco Aircraft Production, 1923-1942
by Raymond H. Brandly, published in 1986. MA
Roy Day
[email protected]
WACO 10 Biplane
36 MODEL AVIATION
07sig2.QXD_00MSTRPG.QXD 5/24/11 8:36 AM Page 36
WACO 10
Prepare the firewall for your particular motor mounting before
you glue it in the fuselage.
The cowl is vacuum-formed plastic. It is held to the firewall with
two magnets mounted in a frame around the inside back of the
cowl.
This is my homemade tail wheel, which gives about one half of the
deflection of the rudder. With this arrangement, the shortcoupled
WACO is easy to handle on the runway.
The tail assembly is bolted on or removed with a socket wrench
inserted through an opening in the bottom of the fuselage. The
whole assembly is quite rigid and allows for removal if needed for
adjustment or transport.
Now that the correct positions of the cabanes have been
determined, you can drill their holes in the plywood support blocks.
Type: RC electric sport scale
Skill level: Intermediate builder; intermediate pilot
Wingspan: 44 inches
Wing area: 600 square inches
Length: 30 inches
Weight: 55 ounces
Power system: Himax HC3522-700; three-cell, 2100
mAh li-Poly or four-cell A123 2300 mAh battery
Construction: Balsa and plywood
Finish: UltraCote iron-on film covering
July 2011 37
07sig2.QXD_00MSTRPG.QXD 5/24/11 8:38 AM Page 37
38 MODEL AVIATION
The WACO 10 is somewhat simpler in
design, with nearly identical straight wings and
a truss-design fuselage. This electric-powered
version also flies well and is relatively easy to
build.
CONSTRUCTION
Wings: The top and bottom wings are nearly
identical; they have the same ribs, spars, center
sheeting, and wingtips. However, the span of
the bottom wing is slightly shorter than that of
the top; the bottom has 21/2° of dihedral and
ailerons; the top wing has no dihedral.
Begin by making the 28 ribs. Use
templates of 1/8 plywood with blanks of 1/16
balsa sheet for the ribs. Rough-shape the ribs
with a band saw, hand-sand them to final form,
and cut notches for the spar caps.
Start with either the right or left panel of
the bottom wing. Lay the forward and aft
bottom basswood spar caps and the TE sheet.
Glue the ribs in position.
Adhere the top basswood spar caps and the
LE. Cut the aileron bottom sheet with the three
ribs and add end rib tips.
Add a plywood block for the aileron horn
before sheeting the top of the aileron. Face the
aileron LE and ends with 1/16 balsa sheet. Glue
a balsa fill block for the wing hold-down bolts
before sheeting the top TE.
The interplane wing struts are not
functional; they are held in with magnets. Add
the wing-strut attachment blocks (for magnets)
on the top side of the bottom wing, even with
the top surface.
Glue on the laminated wingtip. Epoxy the
plywood dihedral brace for this panel. For a
stronger and faster build, use one-piece spar
caps (long enough for both panels) and bend
them at the center as required.
Remove the panel from the building board
and add the top and bottom 1/8 x 1/4 subspars.
Block up the completed wing panel 1.6 inches
at the tip rib (which gives the required
dihedral), and fasten the bottom spar caps of
the other panel to your building board.
Build the second panel of the bottom wing
exactly as you did the first. Epoxy the
plywood dihedral brace to the spar of the
second panel.
Before proceeding further, build the aileron
servo supports and string the servo leads
through holes in the ribs to the wing center.
You can now apply the center sheeting, along
with the rib capstrips, the shear webbing, and
the wingtip. After a bit of sanding, you have
completed the bottom wing.
The top wing is easier to construct than the
bottom wing. There is no dihedral, so you can
lay the entire wing flat on your building board.
With the center sheeting, top and bottom, it is
strong enough without a plywood dihedral
brace.
Glue in the ribs on the bottom spar caps.
Add the LE, top spar caps, and subspars.
Sheet the TE, both top and bottom, and add
the wingtips. Don’t forget to put in plywood
attachment blocks for the cabanes on the
bottom of the wing, as shown on the plans.
You also need to add balsa attachment blocks
for the magnets that hold the interplane struts
on the bottom side of the wing.
Before we go further, I have a few words
for you about applying magnets on the WACO
10. Throughout the design I have used 1/4-
inch-diameter, 1/4-inch-long rare earth
neodymium magnets from Amazing Magnets.
For the interplane struts I merely drilled a 1/4-
inch hole in the balsa support blocks and glued
in the magnets with CA.
It is unnecessary to have magnets on the
ends of the struts; simply glue on a small steel
washer to interface with the magnet. Be sure
you don’t use aluminum washers.
In a similar way, these magnets are used to
hold on the cowl and the hatch. They have
been satisfactory and are inexpensive.
You can apply the wing covering directly
over the magnets. They are strong enough to
snap the struts in place even with the covering
there.
Fuselage: The basic truss structure is built
using 3/16 square balsa. Construct the sides
directly over the plans, but leave out the
diagonals until assembly; it’s easier to bend
the sides without them.
The only use of plywood in the fuselage is
for the landing-gear plate, the wing holddown,
a lamination on the firewall, and the
hard points for the cabane supports.
Prepare the firewall (F1) for your particular
motor mount before mounting it to the
fuselage.
Assemble the fuselage structure upsidedown
on your building board, allowing the
firewall to hang over the edge. Cover the
cockpit area with 1/16 sheet, and make the
cutouts using templates from the plans.
The WACO 10 is a three-place airplane,
which explains why the forward cockpit is
larger than the aft. I used 1/8-inch-diameter
rubber tubing from an auto-parts store for the
cockpit coaming.
Build the hatch in place and make
provisions for a forward peg and magnets on
the rear corners. Glue in the plywood supports
for the cabanes, but don’t drill the holes at this
time.
Landing Gear: The basic landing gear is not
difficult to fashion using a wire bender.
However, the strut extending up to the cabane
support blocks is slightly more difficult to
solder at the right angle and proper length.
I learned a trick during the build. Don’t
make the slot for the strut or drill the holes for
the cabanes until you have made those items.
That will ensure that you have an accurate fit.
In the case of the cabane holes, that means you
should wait until you rig the top wing; I will
cover that later.
The WACO 10 is relatively short-coupled,
so it is best to have a tail wheel assembly that
is not directly coupled to the rudder; if it is, the
model might be difficult to steer on takeoff.
I designed the tail wheel assembly using
springs, brass strip, and music wire. It gives
the tail wheel deflection approximately half
that of the rudder. Ground handling is
excellent. You can use a commercial tail wheel
assembly, such as those that Du-Bro sells.
Cowl: This piece is vacuum-formed plastic; I
have used both PETG (clear) and ABS. The
plastic is formed over a balsa pattern called a
plug.
I reinforced the back edge of the finished
07sig2.QXD_00MSTRPG.QXD 5/24/11 8:41 AM Page 38
40 MODEL AVIATION
cowl with a balsa frame where I glued two of
the same magnets I have used elsewhere. You
can obtain cowls from me.
Tail Surfaces: Most builders know the
importance of fabricating lightweight tail
surfaces. For many years I have used a
technique that employs a sheet center core,
false ribs, and doublers.
It’s easy to build any shape of tail. I attach
the vertical and horizontal tails with a single
nylon bolt, which allows them to be removed
for transport or adjustments to the tail; e.g., a
change to the stabilizer incidence.
The vertical and horizontal tails are
aligned with pegs and held firmly in place by
a 10 x 32 nylon bolt inserted through the
bottom of the fuselage and threaded into the
base of the vertical fin.
Rigging the Top Wing: The cabanes are
made from music wire and attached to the top
wing with landing-gear straps and nylon
bolts. I have had the best results with both
wings set at 0° incidence.
Make a fixture from wood or foam that
rests on the top of the fuselage, to position the
top wing at the correct height, angle, and
forward position relative to the bottom wing.
Check this with an incidence meter to ensure
that the top and bottom wings match. Mark
where the cabane ends touch the support
plywood blocks and drill holes there.
Remove the fixture supporting the top
wing, and check the incidence one more time
to be sure it matches the bottom wing. If they
are within 1/2° of each other, you are finished.
Final Touches: I do like to include a pilot
figure; I hate to see a scale model fly without
one.
You can dress up the cockpit with a
photograph of an instrument panel. Scan a
picture of one into your computer and size it
to fit. You can find some pictures of
instrument panels on the Internet.
Add 1/8-inch fairings to the cabanes and
landing-gear struts, to improve their looks.
Paint them your favorite color.
Power System: I chose a 400-watt Himax
HC3522-0700 outrunner brushless motor,
which I purchased from Maxx Products
International. A 300-watt power plant would
have been quite adequate; I wanted the power
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NEW from Fromeco. Cricket is a voltage monitoring
device. Meant to be mounted in a conspicuous area on
your Aircraft. LED light bar configured in a half round dial
configuration. Mount in cockpit floor or behind dash for a
realistic gauge look.
• Light bar captures lowest voltage in flight.
• Brilliant Blue lights above 5 volts and Red below
5 volts.
loading to be 70-75 watts per pound. The
Himax is satisfactory power for leisure flight
and some aerobatics, borne out by flight tests.
I could have used a battery of three A123
cells, saving 3 ounces, with a larger propeller,
but the model had insufficient ground
clearance. In addition, to use a three-cell
A123 pack I would choose a motor with
roughly 1,000 kV instead of the 700 kV of the
motor I used.
Using a three-cell Li-Poly battery would
produce essentially the same power as the
four-cell A123 battery that I employed and
save close to 6 ounces in weight. However,
that would likely produce a balance problem,
which would require you to add several
ounces of lead to the firewall.
I have flown using A123 battery packs for
more than a year and prefer them to Li-Poly,
except for in extraordinarily light aircraft. And
there are smaller A123 cells (1100 mAh),
which are lighter. I have yet to try them.
The A123 cells with their metal cases are
rugged, charge faster than their Li-Poly
counterparts, have no safety issues, have more
charge cycles, and cost nearly the same or less
than Li-Polys.
Flight Tests: Before the first flight I had a
few last-minute checks to make in the shop.
The balance was correct with the four-cell
A123 battery pack forward against the
firewall; no lead was needed.
An incidence check of right and left wing
panels showed the right top panel to have a
tad greater incidence (less than 1°) than the
left. That would mean a tendency to turn left,
so I put in a bit of right trim.
I checked the control surfaces for correct
direction, and the amplitude looked all right.
My son, Michael, was visiting at the time,
and I asked him to make the maiden flight.
Beforehand we conducted a range test and
determined that we had no interference.
Michael did some taxi tests on the runway,
and we adjusted the tail wheel to give a
straight run. The 2:1 gearing of the rudder-totail
wheel deflection made for an easy takeoff
run. The WACO climbed out with authority
and required only minor trim adjustments for
straight-and-level flight.
Loops and rolls were easy and stalls were
straight ahead, with no falloffs on the wing.
After a flight of approximately five
minutes, Michael brought the airplane in for a
smooth landing; I was incredibly pleased with
its performance.
If you like biplanes, the WACO 10 will
give you many pleasurable flights. MA
Roy Day
[email protected]
Sources:
Amazing Magnets
(888) 727-3327
www.amazingmagnets.com
Maxx Products International
(800) 416-6299
www.maxxprod.com
Du-Bro
(800) 848-9411
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07sig2.QXD_00MSTRPG.QXD 5/24/11 8:42 AM Page 40
Edition: Model Aviation - 2011/07
Page Numbers: 34,35,36,37,38,40
34 MODEL AVIATION
by Roy Day WACO 10
To rig the top wing of a biplane, you need a
jig to hold the wing at the proper incidence
and height above the bottom wing and
position it forward of the lower wing.
I’VE ALWAYS LIKED biplanes,
and I particularly admire those that
WACO built. Years ago I designed
and built a glow-powered model of
the UPF-7. I flew it for many years
and thought it one was of the bestflying
models I had designed. A
construction article of the UPF-7
was published in the February 1995
MA; it’s plans set 778.
A 1920s
classic
for
electric
power
07sig2.QXD_00MSTRPG.QXD 5/24/11 8:18 AM Page 34
July 2011 35
The landing gear is made from music wire and
attached with nylon bolts to the plywood landing
gear plate. Note the openings, which save weight
and provide cooling vents.
The hatch allows ad equate room for th e A123 four-cell
battery or a 3S1P LiPo.
07sig2.QXD_00MSTRPG.QXD 5/24/11 8:34 AM Page 35
Photos by the author
Super magnets, to hold the interplane struts, are mounted
on the top surface of the bottom wing and on the bottom
of the top wing. You can cover them and they will still hold
the struts firmly.
Above right: The top wing has no dihedral so it can be built
flat on your building board. All of the ribs are identical for
both wings, which is a time saver.
The basic truss structure of the fuselage is built from 3/16-
inch-square balsa. Assemble the fuselage upside down,
allowing the firewall to hang over the building board.
After you have built both bottom wing panels, pin one panel down and jig the other panel up 1.6 inches at the tip rib to give 2.5° of
dihedral. Now epoxy the plywood wing brace and clamp it securely.
WACO built a series of open-cockpit and cabin biplanes from the
1920s until World War II. In 1927 the company manufactured the
first model 10: a straight-wing, three-place, open-cockpit design
powered by the 90-horsepower Curtiss OX-5 engine.
More than 1,100 10s were sold in the next three years. And
during that time period, WACO began building variants of the 10
with different engines—mostly radials.
Except for the forward fuselage, which was redesigned to
accommodate the radial power plants, the new airplanes were
identical to the original WACO 10. They were designated the 125,
DSO, ASO, and BSO. The company had found a successful design
and stuck with it.
Also during that time period, WACO built a few aircraft with
tapered wings instead of the straight configuration of the 10 and with
more-powerful engines. Those “taperwings” were popular for
barnstorming at air shows.
The information in this sidebar and the 1927 photo of the WACO
10 were taken from the book Waco Aircraft Production, 1923-1942
by Raymond H. Brandly, published in 1986. MA
Roy Day
[email protected]
WACO 10 Biplane
36 MODEL AVIATION
07sig2.QXD_00MSTRPG.QXD 5/24/11 8:36 AM Page 36
WACO 10
Prepare the firewall for your particular motor mounting before
you glue it in the fuselage.
The cowl is vacuum-formed plastic. It is held to the firewall with
two magnets mounted in a frame around the inside back of the
cowl.
This is my homemade tail wheel, which gives about one half of the
deflection of the rudder. With this arrangement, the shortcoupled
WACO is easy to handle on the runway.
The tail assembly is bolted on or removed with a socket wrench
inserted through an opening in the bottom of the fuselage. The
whole assembly is quite rigid and allows for removal if needed for
adjustment or transport.
Now that the correct positions of the cabanes have been
determined, you can drill their holes in the plywood support blocks.
Type: RC electric sport scale
Skill level: Intermediate builder; intermediate pilot
Wingspan: 44 inches
Wing area: 600 square inches
Length: 30 inches
Weight: 55 ounces
Power system: Himax HC3522-700; three-cell, 2100
mAh li-Poly or four-cell A123 2300 mAh battery
Construction: Balsa and plywood
Finish: UltraCote iron-on film covering
July 2011 37
07sig2.QXD_00MSTRPG.QXD 5/24/11 8:38 AM Page 37
38 MODEL AVIATION
The WACO 10 is somewhat simpler in
design, with nearly identical straight wings and
a truss-design fuselage. This electric-powered
version also flies well and is relatively easy to
build.
CONSTRUCTION
Wings: The top and bottom wings are nearly
identical; they have the same ribs, spars, center
sheeting, and wingtips. However, the span of
the bottom wing is slightly shorter than that of
the top; the bottom has 21/2° of dihedral and
ailerons; the top wing has no dihedral.
Begin by making the 28 ribs. Use
templates of 1/8 plywood with blanks of 1/16
balsa sheet for the ribs. Rough-shape the ribs
with a band saw, hand-sand them to final form,
and cut notches for the spar caps.
Start with either the right or left panel of
the bottom wing. Lay the forward and aft
bottom basswood spar caps and the TE sheet.
Glue the ribs in position.
Adhere the top basswood spar caps and the
LE. Cut the aileron bottom sheet with the three
ribs and add end rib tips.
Add a plywood block for the aileron horn
before sheeting the top of the aileron. Face the
aileron LE and ends with 1/16 balsa sheet. Glue
a balsa fill block for the wing hold-down bolts
before sheeting the top TE.
The interplane wing struts are not
functional; they are held in with magnets. Add
the wing-strut attachment blocks (for magnets)
on the top side of the bottom wing, even with
the top surface.
Glue on the laminated wingtip. Epoxy the
plywood dihedral brace for this panel. For a
stronger and faster build, use one-piece spar
caps (long enough for both panels) and bend
them at the center as required.
Remove the panel from the building board
and add the top and bottom 1/8 x 1/4 subspars.
Block up the completed wing panel 1.6 inches
at the tip rib (which gives the required
dihedral), and fasten the bottom spar caps of
the other panel to your building board.
Build the second panel of the bottom wing
exactly as you did the first. Epoxy the
plywood dihedral brace to the spar of the
second panel.
Before proceeding further, build the aileron
servo supports and string the servo leads
through holes in the ribs to the wing center.
You can now apply the center sheeting, along
with the rib capstrips, the shear webbing, and
the wingtip. After a bit of sanding, you have
completed the bottom wing.
The top wing is easier to construct than the
bottom wing. There is no dihedral, so you can
lay the entire wing flat on your building board.
With the center sheeting, top and bottom, it is
strong enough without a plywood dihedral
brace.
Glue in the ribs on the bottom spar caps.
Add the LE, top spar caps, and subspars.
Sheet the TE, both top and bottom, and add
the wingtips. Don’t forget to put in plywood
attachment blocks for the cabanes on the
bottom of the wing, as shown on the plans.
You also need to add balsa attachment blocks
for the magnets that hold the interplane struts
on the bottom side of the wing.
Before we go further, I have a few words
for you about applying magnets on the WACO
10. Throughout the design I have used 1/4-
inch-diameter, 1/4-inch-long rare earth
neodymium magnets from Amazing Magnets.
For the interplane struts I merely drilled a 1/4-
inch hole in the balsa support blocks and glued
in the magnets with CA.
It is unnecessary to have magnets on the
ends of the struts; simply glue on a small steel
washer to interface with the magnet. Be sure
you don’t use aluminum washers.
In a similar way, these magnets are used to
hold on the cowl and the hatch. They have
been satisfactory and are inexpensive.
You can apply the wing covering directly
over the magnets. They are strong enough to
snap the struts in place even with the covering
there.
Fuselage: The basic truss structure is built
using 3/16 square balsa. Construct the sides
directly over the plans, but leave out the
diagonals until assembly; it’s easier to bend
the sides without them.
The only use of plywood in the fuselage is
for the landing-gear plate, the wing holddown,
a lamination on the firewall, and the
hard points for the cabane supports.
Prepare the firewall (F1) for your particular
motor mount before mounting it to the
fuselage.
Assemble the fuselage structure upsidedown
on your building board, allowing the
firewall to hang over the edge. Cover the
cockpit area with 1/16 sheet, and make the
cutouts using templates from the plans.
The WACO 10 is a three-place airplane,
which explains why the forward cockpit is
larger than the aft. I used 1/8-inch-diameter
rubber tubing from an auto-parts store for the
cockpit coaming.
Build the hatch in place and make
provisions for a forward peg and magnets on
the rear corners. Glue in the plywood supports
for the cabanes, but don’t drill the holes at this
time.
Landing Gear: The basic landing gear is not
difficult to fashion using a wire bender.
However, the strut extending up to the cabane
support blocks is slightly more difficult to
solder at the right angle and proper length.
I learned a trick during the build. Don’t
make the slot for the strut or drill the holes for
the cabanes until you have made those items.
That will ensure that you have an accurate fit.
In the case of the cabane holes, that means you
should wait until you rig the top wing; I will
cover that later.
The WACO 10 is relatively short-coupled,
so it is best to have a tail wheel assembly that
is not directly coupled to the rudder; if it is, the
model might be difficult to steer on takeoff.
I designed the tail wheel assembly using
springs, brass strip, and music wire. It gives
the tail wheel deflection approximately half
that of the rudder. Ground handling is
excellent. You can use a commercial tail wheel
assembly, such as those that Du-Bro sells.
Cowl: This piece is vacuum-formed plastic; I
have used both PETG (clear) and ABS. The
plastic is formed over a balsa pattern called a
plug.
I reinforced the back edge of the finished
07sig2.QXD_00MSTRPG.QXD 5/24/11 8:41 AM Page 38
40 MODEL AVIATION
cowl with a balsa frame where I glued two of
the same magnets I have used elsewhere. You
can obtain cowls from me.
Tail Surfaces: Most builders know the
importance of fabricating lightweight tail
surfaces. For many years I have used a
technique that employs a sheet center core,
false ribs, and doublers.
It’s easy to build any shape of tail. I attach
the vertical and horizontal tails with a single
nylon bolt, which allows them to be removed
for transport or adjustments to the tail; e.g., a
change to the stabilizer incidence.
The vertical and horizontal tails are
aligned with pegs and held firmly in place by
a 10 x 32 nylon bolt inserted through the
bottom of the fuselage and threaded into the
base of the vertical fin.
Rigging the Top Wing: The cabanes are
made from music wire and attached to the top
wing with landing-gear straps and nylon
bolts. I have had the best results with both
wings set at 0° incidence.
Make a fixture from wood or foam that
rests on the top of the fuselage, to position the
top wing at the correct height, angle, and
forward position relative to the bottom wing.
Check this with an incidence meter to ensure
that the top and bottom wings match. Mark
where the cabane ends touch the support
plywood blocks and drill holes there.
Remove the fixture supporting the top
wing, and check the incidence one more time
to be sure it matches the bottom wing. If they
are within 1/2° of each other, you are finished.
Final Touches: I do like to include a pilot
figure; I hate to see a scale model fly without
one.
You can dress up the cockpit with a
photograph of an instrument panel. Scan a
picture of one into your computer and size it
to fit. You can find some pictures of
instrument panels on the Internet.
Add 1/8-inch fairings to the cabanes and
landing-gear struts, to improve their looks.
Paint them your favorite color.
Power System: I chose a 400-watt Himax
HC3522-0700 outrunner brushless motor,
which I purchased from Maxx Products
International. A 300-watt power plant would
have been quite adequate; I wanted the power
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Flight System. NEW LED light bar shows voltages from
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• Light bar captures lowest voltage in flight.
• 1.25 Farads of Capacitance.
• Brilliant Blue lights above 5 volts and Red below
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Fromeco’s Cricket
NEW from Fromeco. Cricket is a voltage monitoring
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realistic gauge look.
• Light bar captures lowest voltage in flight.
• Brilliant Blue lights above 5 volts and Red below
5 volts.
loading to be 70-75 watts per pound. The
Himax is satisfactory power for leisure flight
and some aerobatics, borne out by flight tests.
I could have used a battery of three A123
cells, saving 3 ounces, with a larger propeller,
but the model had insufficient ground
clearance. In addition, to use a three-cell
A123 pack I would choose a motor with
roughly 1,000 kV instead of the 700 kV of the
motor I used.
Using a three-cell Li-Poly battery would
produce essentially the same power as the
four-cell A123 battery that I employed and
save close to 6 ounces in weight. However,
that would likely produce a balance problem,
which would require you to add several
ounces of lead to the firewall.
I have flown using A123 battery packs for
more than a year and prefer them to Li-Poly,
except for in extraordinarily light aircraft. And
there are smaller A123 cells (1100 mAh),
which are lighter. I have yet to try them.
The A123 cells with their metal cases are
rugged, charge faster than their Li-Poly
counterparts, have no safety issues, have more
charge cycles, and cost nearly the same or less
than Li-Polys.
Flight Tests: Before the first flight I had a
few last-minute checks to make in the shop.
The balance was correct with the four-cell
A123 battery pack forward against the
firewall; no lead was needed.
An incidence check of right and left wing
panels showed the right top panel to have a
tad greater incidence (less than 1°) than the
left. That would mean a tendency to turn left,
so I put in a bit of right trim.
I checked the control surfaces for correct
direction, and the amplitude looked all right.
My son, Michael, was visiting at the time,
and I asked him to make the maiden flight.
Beforehand we conducted a range test and
determined that we had no interference.
Michael did some taxi tests on the runway,
and we adjusted the tail wheel to give a
straight run. The 2:1 gearing of the rudder-totail
wheel deflection made for an easy takeoff
run. The WACO climbed out with authority
and required only minor trim adjustments for
straight-and-level flight.
Loops and rolls were easy and stalls were
straight ahead, with no falloffs on the wing.
After a flight of approximately five
minutes, Michael brought the airplane in for a
smooth landing; I was incredibly pleased with
its performance.
If you like biplanes, the WACO 10 will
give you many pleasurable flights. MA
Roy Day
[email protected]
Sources:
Amazing Magnets
(888) 727-3327
www.amazingmagnets.com
Maxx Products International
(800) 416-6299
www.maxxprod.com
Du-Bro
(800) 848-9411
TIRED OF PAYING
$1.29 FOR 6 SCREWS?
Our 4-40x1/2 socket
caps sell for $4.35/100
for alloy steel, or
$6.65/100 stainless, or $7.50/50 aluminum.
For fair prices on sensible quantities of the fasteners
you need for model building, call, write or
fax for our free catalog!
Micro Fasteners 800-892-6917
24 Cokesbury Rd., Suite 2 908-236-8120
Lebanon, NJ 08833 fax 908-236-8721
e-mail: [email protected] Internet: http://microfasteners.com
07sig2.QXD_00MSTRPG.QXD 5/24/11 8:42 AM Page 40
Edition: Model Aviation - 2011/07
Page Numbers: 34,35,36,37,38,40
34 MODEL AVIATION
by Roy Day WACO 10
To rig the top wing of a biplane, you need a
jig to hold the wing at the proper incidence
and height above the bottom wing and
position it forward of the lower wing.
I’VE ALWAYS LIKED biplanes,
and I particularly admire those that
WACO built. Years ago I designed
and built a glow-powered model of
the UPF-7. I flew it for many years
and thought it one was of the bestflying
models I had designed. A
construction article of the UPF-7
was published in the February 1995
MA; it’s plans set 778.
A 1920s
classic
for
electric
power
07sig2.QXD_00MSTRPG.QXD 5/24/11 8:18 AM Page 34
July 2011 35
The landing gear is made from music wire and
attached with nylon bolts to the plywood landing
gear plate. Note the openings, which save weight
and provide cooling vents.
The hatch allows ad equate room for th e A123 four-cell
battery or a 3S1P LiPo.
07sig2.QXD_00MSTRPG.QXD 5/24/11 8:34 AM Page 35
Photos by the author
Super magnets, to hold the interplane struts, are mounted
on the top surface of the bottom wing and on the bottom
of the top wing. You can cover them and they will still hold
the struts firmly.
Above right: The top wing has no dihedral so it can be built
flat on your building board. All of the ribs are identical for
both wings, which is a time saver.
The basic truss structure of the fuselage is built from 3/16-
inch-square balsa. Assemble the fuselage upside down,
allowing the firewall to hang over the building board.
After you have built both bottom wing panels, pin one panel down and jig the other panel up 1.6 inches at the tip rib to give 2.5° of
dihedral. Now epoxy the plywood wing brace and clamp it securely.
WACO built a series of open-cockpit and cabin biplanes from the
1920s until World War II. In 1927 the company manufactured the
first model 10: a straight-wing, three-place, open-cockpit design
powered by the 90-horsepower Curtiss OX-5 engine.
More than 1,100 10s were sold in the next three years. And
during that time period, WACO began building variants of the 10
with different engines—mostly radials.
Except for the forward fuselage, which was redesigned to
accommodate the radial power plants, the new airplanes were
identical to the original WACO 10. They were designated the 125,
DSO, ASO, and BSO. The company had found a successful design
and stuck with it.
Also during that time period, WACO built a few aircraft with
tapered wings instead of the straight configuration of the 10 and with
more-powerful engines. Those “taperwings” were popular for
barnstorming at air shows.
The information in this sidebar and the 1927 photo of the WACO
10 were taken from the book Waco Aircraft Production, 1923-1942
by Raymond H. Brandly, published in 1986. MA
Roy Day
[email protected]
WACO 10 Biplane
36 MODEL AVIATION
07sig2.QXD_00MSTRPG.QXD 5/24/11 8:36 AM Page 36
WACO 10
Prepare the firewall for your particular motor mounting before
you glue it in the fuselage.
The cowl is vacuum-formed plastic. It is held to the firewall with
two magnets mounted in a frame around the inside back of the
cowl.
This is my homemade tail wheel, which gives about one half of the
deflection of the rudder. With this arrangement, the shortcoupled
WACO is easy to handle on the runway.
The tail assembly is bolted on or removed with a socket wrench
inserted through an opening in the bottom of the fuselage. The
whole assembly is quite rigid and allows for removal if needed for
adjustment or transport.
Now that the correct positions of the cabanes have been
determined, you can drill their holes in the plywood support blocks.
Type: RC electric sport scale
Skill level: Intermediate builder; intermediate pilot
Wingspan: 44 inches
Wing area: 600 square inches
Length: 30 inches
Weight: 55 ounces
Power system: Himax HC3522-700; three-cell, 2100
mAh li-Poly or four-cell A123 2300 mAh battery
Construction: Balsa and plywood
Finish: UltraCote iron-on film covering
July 2011 37
07sig2.QXD_00MSTRPG.QXD 5/24/11 8:38 AM Page 37
38 MODEL AVIATION
The WACO 10 is somewhat simpler in
design, with nearly identical straight wings and
a truss-design fuselage. This electric-powered
version also flies well and is relatively easy to
build.
CONSTRUCTION
Wings: The top and bottom wings are nearly
identical; they have the same ribs, spars, center
sheeting, and wingtips. However, the span of
the bottom wing is slightly shorter than that of
the top; the bottom has 21/2° of dihedral and
ailerons; the top wing has no dihedral.
Begin by making the 28 ribs. Use
templates of 1/8 plywood with blanks of 1/16
balsa sheet for the ribs. Rough-shape the ribs
with a band saw, hand-sand them to final form,
and cut notches for the spar caps.
Start with either the right or left panel of
the bottom wing. Lay the forward and aft
bottom basswood spar caps and the TE sheet.
Glue the ribs in position.
Adhere the top basswood spar caps and the
LE. Cut the aileron bottom sheet with the three
ribs and add end rib tips.
Add a plywood block for the aileron horn
before sheeting the top of the aileron. Face the
aileron LE and ends with 1/16 balsa sheet. Glue
a balsa fill block for the wing hold-down bolts
before sheeting the top TE.
The interplane wing struts are not
functional; they are held in with magnets. Add
the wing-strut attachment blocks (for magnets)
on the top side of the bottom wing, even with
the top surface.
Glue on the laminated wingtip. Epoxy the
plywood dihedral brace for this panel. For a
stronger and faster build, use one-piece spar
caps (long enough for both panels) and bend
them at the center as required.
Remove the panel from the building board
and add the top and bottom 1/8 x 1/4 subspars.
Block up the completed wing panel 1.6 inches
at the tip rib (which gives the required
dihedral), and fasten the bottom spar caps of
the other panel to your building board.
Build the second panel of the bottom wing
exactly as you did the first. Epoxy the
plywood dihedral brace to the spar of the
second panel.
Before proceeding further, build the aileron
servo supports and string the servo leads
through holes in the ribs to the wing center.
You can now apply the center sheeting, along
with the rib capstrips, the shear webbing, and
the wingtip. After a bit of sanding, you have
completed the bottom wing.
The top wing is easier to construct than the
bottom wing. There is no dihedral, so you can
lay the entire wing flat on your building board.
With the center sheeting, top and bottom, it is
strong enough without a plywood dihedral
brace.
Glue in the ribs on the bottom spar caps.
Add the LE, top spar caps, and subspars.
Sheet the TE, both top and bottom, and add
the wingtips. Don’t forget to put in plywood
attachment blocks for the cabanes on the
bottom of the wing, as shown on the plans.
You also need to add balsa attachment blocks
for the magnets that hold the interplane struts
on the bottom side of the wing.
Before we go further, I have a few words
for you about applying magnets on the WACO
10. Throughout the design I have used 1/4-
inch-diameter, 1/4-inch-long rare earth
neodymium magnets from Amazing Magnets.
For the interplane struts I merely drilled a 1/4-
inch hole in the balsa support blocks and glued
in the magnets with CA.
It is unnecessary to have magnets on the
ends of the struts; simply glue on a small steel
washer to interface with the magnet. Be sure
you don’t use aluminum washers.
In a similar way, these magnets are used to
hold on the cowl and the hatch. They have
been satisfactory and are inexpensive.
You can apply the wing covering directly
over the magnets. They are strong enough to
snap the struts in place even with the covering
there.
Fuselage: The basic truss structure is built
using 3/16 square balsa. Construct the sides
directly over the plans, but leave out the
diagonals until assembly; it’s easier to bend
the sides without them.
The only use of plywood in the fuselage is
for the landing-gear plate, the wing holddown,
a lamination on the firewall, and the
hard points for the cabane supports.
Prepare the firewall (F1) for your particular
motor mount before mounting it to the
fuselage.
Assemble the fuselage structure upsidedown
on your building board, allowing the
firewall to hang over the edge. Cover the
cockpit area with 1/16 sheet, and make the
cutouts using templates from the plans.
The WACO 10 is a three-place airplane,
which explains why the forward cockpit is
larger than the aft. I used 1/8-inch-diameter
rubber tubing from an auto-parts store for the
cockpit coaming.
Build the hatch in place and make
provisions for a forward peg and magnets on
the rear corners. Glue in the plywood supports
for the cabanes, but don’t drill the holes at this
time.
Landing Gear: The basic landing gear is not
difficult to fashion using a wire bender.
However, the strut extending up to the cabane
support blocks is slightly more difficult to
solder at the right angle and proper length.
I learned a trick during the build. Don’t
make the slot for the strut or drill the holes for
the cabanes until you have made those items.
That will ensure that you have an accurate fit.
In the case of the cabane holes, that means you
should wait until you rig the top wing; I will
cover that later.
The WACO 10 is relatively short-coupled,
so it is best to have a tail wheel assembly that
is not directly coupled to the rudder; if it is, the
model might be difficult to steer on takeoff.
I designed the tail wheel assembly using
springs, brass strip, and music wire. It gives
the tail wheel deflection approximately half
that of the rudder. Ground handling is
excellent. You can use a commercial tail wheel
assembly, such as those that Du-Bro sells.
Cowl: This piece is vacuum-formed plastic; I
have used both PETG (clear) and ABS. The
plastic is formed over a balsa pattern called a
plug.
I reinforced the back edge of the finished
07sig2.QXD_00MSTRPG.QXD 5/24/11 8:41 AM Page 38
40 MODEL AVIATION
cowl with a balsa frame where I glued two of
the same magnets I have used elsewhere. You
can obtain cowls from me.
Tail Surfaces: Most builders know the
importance of fabricating lightweight tail
surfaces. For many years I have used a
technique that employs a sheet center core,
false ribs, and doublers.
It’s easy to build any shape of tail. I attach
the vertical and horizontal tails with a single
nylon bolt, which allows them to be removed
for transport or adjustments to the tail; e.g., a
change to the stabilizer incidence.
The vertical and horizontal tails are
aligned with pegs and held firmly in place by
a 10 x 32 nylon bolt inserted through the
bottom of the fuselage and threaded into the
base of the vertical fin.
Rigging the Top Wing: The cabanes are
made from music wire and attached to the top
wing with landing-gear straps and nylon
bolts. I have had the best results with both
wings set at 0° incidence.
Make a fixture from wood or foam that
rests on the top of the fuselage, to position the
top wing at the correct height, angle, and
forward position relative to the bottom wing.
Check this with an incidence meter to ensure
that the top and bottom wings match. Mark
where the cabane ends touch the support
plywood blocks and drill holes there.
Remove the fixture supporting the top
wing, and check the incidence one more time
to be sure it matches the bottom wing. If they
are within 1/2° of each other, you are finished.
Final Touches: I do like to include a pilot
figure; I hate to see a scale model fly without
one.
You can dress up the cockpit with a
photograph of an instrument panel. Scan a
picture of one into your computer and size it
to fit. You can find some pictures of
instrument panels on the Internet.
Add 1/8-inch fairings to the cabanes and
landing-gear struts, to improve their looks.
Paint them your favorite color.
Power System: I chose a 400-watt Himax
HC3522-0700 outrunner brushless motor,
which I purchased from Maxx Products
International. A 300-watt power plant would
have been quite adequate; I wanted the power
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loading to be 70-75 watts per pound. The
Himax is satisfactory power for leisure flight
and some aerobatics, borne out by flight tests.
I could have used a battery of three A123
cells, saving 3 ounces, with a larger propeller,
but the model had insufficient ground
clearance. In addition, to use a three-cell
A123 pack I would choose a motor with
roughly 1,000 kV instead of the 700 kV of the
motor I used.
Using a three-cell Li-Poly battery would
produce essentially the same power as the
four-cell A123 battery that I employed and
save close to 6 ounces in weight. However,
that would likely produce a balance problem,
which would require you to add several
ounces of lead to the firewall.
I have flown using A123 battery packs for
more than a year and prefer them to Li-Poly,
except for in extraordinarily light aircraft. And
there are smaller A123 cells (1100 mAh),
which are lighter. I have yet to try them.
The A123 cells with their metal cases are
rugged, charge faster than their Li-Poly
counterparts, have no safety issues, have more
charge cycles, and cost nearly the same or less
than Li-Polys.
Flight Tests: Before the first flight I had a
few last-minute checks to make in the shop.
The balance was correct with the four-cell
A123 battery pack forward against the
firewall; no lead was needed.
An incidence check of right and left wing
panels showed the right top panel to have a
tad greater incidence (less than 1°) than the
left. That would mean a tendency to turn left,
so I put in a bit of right trim.
I checked the control surfaces for correct
direction, and the amplitude looked all right.
My son, Michael, was visiting at the time,
and I asked him to make the maiden flight.
Beforehand we conducted a range test and
determined that we had no interference.
Michael did some taxi tests on the runway,
and we adjusted the tail wheel to give a
straight run. The 2:1 gearing of the rudder-totail
wheel deflection made for an easy takeoff
run. The WACO climbed out with authority
and required only minor trim adjustments for
straight-and-level flight.
Loops and rolls were easy and stalls were
straight ahead, with no falloffs on the wing.
After a flight of approximately five
minutes, Michael brought the airplane in for a
smooth landing; I was incredibly pleased with
its performance.
If you like biplanes, the WACO 10 will
give you many pleasurable flights. MA
Roy Day
[email protected]
Sources:
Amazing Magnets
(888) 727-3327
www.amazingmagnets.com
Maxx Products International
(800) 416-6299
www.maxxprod.com
Du-Bro
(800) 848-9411
TIRED OF PAYING
$1.29 FOR 6 SCREWS?
Our 4-40x1/2 socket
caps sell for $4.35/100
for alloy steel, or
$6.65/100 stainless, or $7.50/50 aluminum.
For fair prices on sensible quantities of the fasteners
you need for model building, call, write or
fax for our free catalog!
Micro Fasteners 800-892-6917
24 Cokesbury Rd., Suite 2 908-236-8120
Lebanon, NJ 08833 fax 908-236-8721
e-mail: [email protected] Internet: http://microfasteners.com
07sig2.QXD_00MSTRPG.QXD 5/24/11 8:42 AM Page 40