Romancing the S.E.5a - 2009/05

May 2009 19
by Gary A. Ritchie
Electric conversion and scale-up
of the great Flair Models kit
A COUPLE OF years ago, I scratch-built
a 1/8-scale British Royal Aircraft Factory
S.E.5a World War I fighter. After flying
this little airplane with a motor for roughly
two years, I became so fond of it that I
decided to build an S.E.5a for a .40-size
engine (approximately 1/6 scale) and
convert it to electric power.
Left: The serial number C6457 S.E.5a on
display in the “Personal Courage Wing” of
the Museum of Flight in Seattle WA.
The S.E.5a passes overhead
during the maiden flight.
05sig1.QXD 3/25/09 9:28 AM Page 19
20 MODEL AVIATION
Gary’s early work on the model’s fuselage shows where the
battery tray, with Velcro strips, and aluminum cabane struts are
located.
The S.E.5a’s “springs” are made from bungee cords that wrap
around the axles. They are highly effective during takeoff and
landing.
Spruce tie-down blocks are embedded for wing wires in the wings
before covering. In this case, the block also serves as a mount for
the metal wing-strut tab.
The author hand-painted the insignia with latex house paint that
was mixed to match the authentic WW I British colors.
Wing struts attach to steel straps embedded in the
wing. The pitot tube details include rubber couplers to
the metal tubing.
Gary fashioned the motor cover and details from thin brass sheets. The
piano hinges are simulated, and rivets are made using wood glue.
Photos by the author
05sig1.QXD 3/25/09 10:17 AM Page 20
May 2009 21
Looking up from beneath the nose, it is possible to see the
simulated spark plugs and some forward fuselage details.
Right: A bellcrank mounted in the rear
fuselage controls both the pull-pull rudder
and the pull-pull tail skid. Four Hitec HS-
81MG servos are used.
A Lewis machine gun rests on its rack. Thin aluminum tubes
running down the wings imitate overflow pipes from the wingmounted
internal gas tank.
The AstroFlight 25 brushed motor is test-fitted before being
attached with two cable ties. The battery tray and Velcro
fasteners are visible behind the motor.
Fabric tie-down twine, shown on the bottom of the upper wing, is
simulated with thin glue strips. Pinked fabric covers were doped
over these tie-downs.
Aileron cables are produced from wires that slide in and out of a
piece of brass tubing that is embedded in the wing.
For this project, I selected the version
that Flair Models produces in the United
Kingdom and Radical RC markets in the
US. This is a kit—not an ARF.
A significant modeling advantage that
the S.E.5a has over many WW I fighters is
that it has a relatively long nose. This
provides ample room for a motor and a
battery pack.
Other attractive WW I biplanes, such
as the Sopwith, Spad, and Nieuport, have
short noses, making them difficult to
05sig1.QXD 3/25/09 9:37 AM Page 21
22 MODEL AVIATION
balance on the CG without adding lots of
weight to the nose. I don’t like to add
weight to an aircraft if I don’t have to.
I enjoy converting a simple kit-built
airplane to a realistic, scalelike airplane.
This includes adding many details:
authentic color-and-markings, weapons,
cockpit, pilot, etc. With most WW I
fighters, you can add wing wires, realistic
landing gear, open cockpits, and exposed
engine details to that list.
I’ll take you through some of the issues
Left: The flying wires are double-stranded.
An Aldis gun sight is aimed to account for
the high-mounted Lewis and Vickers guns. A
long exhaust pipe was a comfort to pilots.
With a grand lake view as the backdrop, you can appreciate the detail of the
empennage showing the cable brace attachments, rudder pull-pull cable, and
elevator cable. Fuselage “stitching” is also visible.
Flair Models S.E.5a Specifications
Type: Sport Scale vintage
Building skill level: Expert
Flying skill level: Intermediate to expert
Wingspan: 51 inches
Length: 39 inches
Wing area: 1,025 square inches
Flying weight: 6.9 pounds
CG position: 11cm back from top-wing LE
Power system: AstroFlight 25 motor with Superbox, Castle Creations Griffin-40
ESC, 15 x 10E APC propeller, Tanic 5S 15-20C 3650 mAh Li-Poly battery
Radio: Futaba 9CAP transmitter, Hitec 555 receiver, four Hitec HS-81MG servos
Engine: .35-.45 two-stroke or .40-.60 four-stroke
05sig1.QXD 3/25/09 10:26 AM Page 22
I had to confront while converting the
Flair Models S.E.5a to a scale-looking,
electric-powered model.
To build a scale model, you must
decide what full-scale subject you want
and then develop a documentation package
for that airplane. I selected a beautiful
S.E.5a replica (serial number C6457) that
is located in the “Personal Courage Wing”
of the Museum of Flight in Seattle,
Washington.
I wanted to replicate this airplane as
closely as I could. A good friend and
fellow modeler, who is a docent at the
museum, provided me with an opportunity
to take many close-up photographs of the
S.E.5a as the basis for my documentation.
The Flair Models S.E.5a is your basic,
old-fashioned, die-cut balsa-and-plywood
kit—nothing fancy. It contains strip and
sheet wood, precut wing ribs and formers,
glow engine-mounting hardware, hardware
pack, plans, and instructions.
The plans are excellent; the instructions
would benefit from illustrations and a few
more details. The die-cutting was
generally good, but I had to do some razor
blade work on several of the plywood
parts. The wood quality was fair.
Electric Power-System Design: The fullscale
S.E.5a’s top speed, with the
Wolseley Viper V8 engine, was 138 mph.
This translates to a 1/6-scale top speed in
the neighborhood of only 23 mph. So I
was not interested in a hopped-up motor
configuration to deliver high power
loadings; I wanted only to replicate scale
speed as closely as possible.
I had to make some educated guesses. I
reckoned that if I could design a power
system that would generate roughly 70-80
watts per pound, I would probably achieve
scalelike flight with this high-drag
airplane.
I estimated the model’s all-up weight,
including a Li-Poly battery pack, to be
6.5-7.0 pounds. A scale propeller would
be approximately 16 inches long. I had a
surplus AstroFlight 25 motor with a 3.1:1-
geared Superbox that I wanted to use.
I estimated, from experience, that I
would need 18-20 volts from the battery
pack. Using these figures, I ran some
simulations with ElectriCalc (electricpower
software). According to the runs,
using a 16 x 10 APC electric propeller
with this motor and battery pack, I could
expect to draw 44 amps and generate close
to 81 watts of power per pound of model.
Dropping back to a 15 x 10 propeller
would reduce the current draw to roughly
40 amps and power to 75 watts per pound.
I decided to go with the 15 x 10, and I was
aware that switching propellers later if
needed would be simple.
Detailing the S.E.5a: Both wings and the
tail feathers went together easily. The ribs
cut from plywood were quite strong. I
used a square to align all of the parts as I
built them over the plans using pins.
I used a glue that is new to me and that
I highly recommend: Titebond’s Molding
and Trim Wood Glue. It is an aliphatic
glue but is thicker than traditional
carpenter’s glue and sets up rapidly. The
hardware store had to special-order it for
me.
Rather than using the nylon control
horns the kit provided, I made scalelike
control horns from 1/16-inch circuit-board
material. I glued several predrilled spruce
blocks into the wings, to serve as strong
fastening points for the wing wires.
I used cyanoacrylate hinges
throughout, rather than the hinges
included with the kit. I glued a 1/16 balsa
strip on the upper center of the upper wing
to later serve as a mounting plate for the
Lewis machine gun. To improve the scale
appearance, I added a partial wing rib to
the LE between each existing rib.
Rather than use one centrally mounted
servo with pushrods and bellcranks for the
ailerons, I installed a Hitec HS-81MG
servo in each wing. Servo extensions ran
through the wings, exiting at the center
where they engaged the aileron Y
connector.
The S.E.5a contains a maze of wires
running among struts, the fuselage,
cabanes, and tail sections. Just sorting
them all and identifying them was a
challenge. I would not have been able to
do it without the museum photos.
I began by sketching the wires on
paper. Then, before covering the wings
and fuselage, I embedded a 1/2-inch square
hardwood block at each point at which a
wire was connected. Each block was
predrilled with a 1/16-inch hole. Before
painting the model, I poked a small hole in
the covering at each attachment point to
mark its location.
With the fuselage, a challenge was
mounting the battery pack and motor.
With a monoplane, I would normally
construct a removable hatch forward of the
canopy to create a battery compartment.
That was out of the question with this
biplane, owing to the location of the
cabane struts and support wires.
Therefore, I decided to make a
removable nose that would slide into the
fuselage from the front and provide access
to the motor and the battery tray. I
mounted the motor with cable ties fastened
around two metal bolts in the lower nose.
The full-scale S.E.5a’s turtledeck has
several shorter stringers just aft of the
cockpit. I added these using basswood
strips. I mounted the servos just aft of the
cockpit and a Hitec Micro 555 receiver
beneath it. A removable 1/16 plywood belly
plate screws to the bottom of the fuselage
to conceal these components.
The elevator is actuated with a metal
rod that protrudes down into the rear of the
fuselage from the elevator torsion bar to
engage the pushrod. I installed fake cables
on the elevator to simulate the cable
arrangement.
The rudder works with a pull-pull cable
system. The rudder servo turns a bellcrank
inside the fuselage just forward of the
rudder. To this bellcrank I attached two
sets of pull-pull wires: one serving the
rudder the other serving the steerable tail
skid.
Landing gear was constructed from 1/8-
inch-diameter steel wire faired with 1/4
hard balsa. Springs were made from
bungee cord wrapped around the axle and
strut, to give a spring effect upon landing.
The 41/2-inch-diameter scale wheels are
from Williams Brothers.
The full-scale S.E.5a’s nose is mostly
metal and wood, and the fuselage aft of
the cockpit is fabric-covered stringers.
Wings and tail surfaces are covered with
fabric.
On the model, I made the nose portions
of the fuselage from either #250 brass
sheet or 1/16 balsa sheeting. I covered the
balsa with GM (gas model)-grade Silkspan
and covered it several times with nitrate
dope to smooth the grain.
I covered the aft fuselage, wings, and
empennage with Nelson Hobby
Specialties’ LiteFAB Natural iron-on
fabric. As on the full-scale S.E.5a and
many other WW I airplanes, the fabric was
bound to the ribs using twine. The ribs
were then covered with strips of pinked
fabric.
The twine was simulated using lines of
wood glue applied with a syringe with a
1/8-inch-diameter brass tube in its nose; I
also simulated the many fuselage rivets
with this method. Each line ran across the
rib cover, spaced 1/2 inch apart.
I applied this technique to the top and
bottom of both wings and tail surfaces.
Then I overlaid the rib covers with 1/2-
inch-wide pinked fabric strips, available
from F&M Enterprises.
The entire model was sealed with
several coats of nontautening nitrate dope
from Aerodyne. The full-scale S.E.5a was
painted with a color known as PC-10,
while the undersides of both wings and
elevator were doped fabric. PC-10 is a
green drab color that airplane painters
often made on-site; there is no specific
formula for it.
To simulate PC-10, I took some of my
photos of the full-scale S.E.5a to a
Benjamin Moore paint store to have the
color matched. It turned out nearly perfect,
and I had a quart of interior latex eggshell
paint of the color made.
I thinned it at roughly 9:1 paint to
water and applied three coats with a
paintbrush, trying to replicate a rough,
hand-painted surface. (They didn’t use
airbrushes in WW I.)
Wing markings were a challenge. I had
ordered roundel decals from an Internet
source but realized that I could not apply
them because of the roughness of the
fabric cover strips and ties. Fortunately I
had not yet applied the PC-10 to the
wings, so I drew the roundels on the
doped fabric with a pencil and painted
them by hand using thinned latex paint.
I painted the wings after applying the
roundels. On the underside of the bottom
wings, I hand-painted the roundels over
the doped fabric.
Final Touches: Someone once said that
an S.E.5a viewed from the front looked
like a farm tractor with wings. The
Wolseley Viper V8’s valve covers and
exhaust manifolds protrude from the nose.
Exhaust pipes connect to the manifold and
extend aft to beneath the cockpit opening.
I carved the pipes from balsa, added tiny
brass bolts, and simulated spark plugs to
the valve covers.
When the model was fully assembled, I
attached the wing and tail wires using
0.014-inch fine braided beading wire from
the Soft Flex Company. I connected the
wires to the wood attachment blocks using
spring clasp connecting tabs (item FI104-
G) from Shipwreck Beads.
The clasps were screwed into the
wooden block using #2 x 3/8-inch buttonhead
screws. The wire ends were passed
through the tabs and swaged together
using 0.033 Mason Connector Sleeves
from Thorn Brothers that I bound with a
crimping tool.
After adding a few final details, such
as the wing-mounted Lewis machine gun
and rack, homemade pitot tube, Aldis gun
sight, instrument panel, scale propeller,
and windshield, the model was finished.
Static Testing: I performed a static test
on the power system using a 5S 3650 Li-
Poly battery and a 15 x 8E APC propeller.
At full throttle, the system drew 30 amps
of current and produced 600 watts of
power with the propeller spinning at 4,590
rpm.
The S.E.5a’s all-up weight was 6.94
pounds, so the power loading was 86 watts
per pound. By moving the battery tray all
the way forward, I achieved a CG that was
right on the mark: 11 centimeters (4.3
inches) back from the upper wing’s LE,
without adding weight.
I set the control throws so that the
aileron had 20mm up and 10mm down,
the elevator had roughly 15mm, and the
rudder had approximately 20mm. I used
only low rates and dialed in close to 35%
exponential on each control surface.
Flying: Uncertain of how the S.E.5a
would perform in the air, I waited for a
warm, relatively calm spring day for the
maiden flight. Our grass field is quite
bumpy, but the model rolled over it at a
good clip, hardly bouncing around at all. I
attribute this to the effective bungee
springs on the landing gear.
The airplane lifted off easily and
smoothly and, following a touch of downtrim,
flew gracefully as I made shallow
turns and slow passes around the field. I
handed the transmitter to my flying buddy,
Bob Benjamin, who brought it around for
a few low passes while I clicked away
with my Canon Rebel SLR camera.
With the shooting finished, I retrieved
the controls and brought the S.E.5a in for
a slow, power-off landing. A touch of
power at the end prevented it from
flipping over in the grass. The first flight
revealed that the airplane was a bit
underpowered, so I replaced the 15 x 8
propeller with a 15 x 10, which helped
somewhat.
As of this writing, I have nearly 50
successful flights on my model. It
performs extremely smoothly and with
great authority—similar to a full-scale
S.E.5a.
Turns are more scalelike if they are
initiated with the rudder and a touch of
down-elevator. It is important that the CG
is set properly; the airplane becomes a
beast when it’s even slightly tail-heavy.
Flair Again? This project required almost
three years to complete but was well worth
the considerable effort. It is absolutely
beautiful, exhilarating to fly, and took first
place in a local scale contest last summer.
The many advantages of electric power
are apparent with models such as this.
There is no protruding cylinder head or
muffler to spoil the lovely nose detail. Can
you imagine what a mess it would be to
clean the glow-engine oil out of the
cockpit, wing wires, machine guns, and
other scale details? And keeping the
lifelike fabric pilot dry would be
impossible.
Add to all that the ease of starting and
restarting the motor, the ability to use
water-based paint on the fabric, the total
lack of vibration, and, oh yes, the low
noise-impact flight. Electric power is a
great way to go with scale! MA
Gary A. Ritchie
[email protected]
Sources:
Flair Models Ltd.
www.flairmodels.co.uk
Radical RC
(937) 256-7727
www.radicalrc.com
AstroFlight
(310) 821-6242
www.astroflight.com
Williams Brothers Model Products
(512) 352-9346
www.williamsbrothersmodelproducts.com
Nelson’s Hobby
(817) 431-9898
www.nelsonhobby.com
F&M Enterprises
(817) 279-8045
www.stits.com
Aerodyne
www.freeflightmodels.com
Soft Flex Company
(800) 925-FLEX
www.softflexcompany.com
Shipwreck Beads
(800) 950-4232
www.shipwreckbeads.com
Thorn Brothers
(763) 572-3782
www.thornebros.com

May 2009 19
by Gary A. Ritchie
Electric conversion and scale-up
of the great Flair Models kit
A COUPLE OF years ago, I scratch-built
a 1/8-scale British Royal Aircraft Factory
S.E.5a World War I fighter. After flying
this little airplane with a motor for roughly
two years, I became so fond of it that I
decided to build an S.E.5a for a .40-size
engine (approximately 1/6 scale) and
convert it to electric power.
Left: The serial number C6457 S.E.5a on
display in the “Personal Courage Wing” of
the Museum of Flight in Seattle WA.
The S.E.5a passes overhead
during the maiden flight.
05sig1.QXD 3/25/09 9:28 AM Page 19
20 MODEL AVIATION
Gary’s early work on the model’s fuselage shows where the
battery tray, with Velcro strips, and aluminum cabane struts are
located.
The S.E.5a’s “springs” are made from bungee cords that wrap
around the axles. They are highly effective during takeoff and
landing.
Spruce tie-down blocks are embedded for wing wires in the wings
before covering. In this case, the block also serves as a mount for
the metal wing-strut tab.
The author hand-painted the insignia with latex house paint that
was mixed to match the authentic WW I British colors.
Wing struts attach to steel straps embedded in the
wing. The pitot tube details include rubber couplers to
the metal tubing.
Gary fashioned the motor cover and details from thin brass sheets. The
piano hinges are simulated, and rivets are made using wood glue.
Photos by the author
05sig1.QXD 3/25/09 10:17 AM Page 20
May 2009 21
Looking up from beneath the nose, it is possible to see the
simulated spark plugs and some forward fuselage details.
Right: A bellcrank mounted in the rear
fuselage controls both the pull-pull rudder
and the pull-pull tail skid. Four Hitec HS-
81MG servos are used.
A Lewis machine gun rests on its rack. Thin aluminum tubes
running down the wings imitate overflow pipes from the wingmounted
internal gas tank.
The AstroFlight 25 brushed motor is test-fitted before being
attached with two cable ties. The battery tray and Velcro
fasteners are visible behind the motor.
Fabric tie-down twine, shown on the bottom of the upper wing, is
simulated with thin glue strips. Pinked fabric covers were doped
over these tie-downs.
Aileron cables are produced from wires that slide in and out of a
piece of brass tubing that is embedded in the wing.
For this project, I selected the version
that Flair Models produces in the United
Kingdom and Radical RC markets in the
US. This is a kit—not an ARF.
A significant modeling advantage that
the S.E.5a has over many WW I fighters is
that it has a relatively long nose. This
provides ample room for a motor and a
battery pack.
Other attractive WW I biplanes, such
as the Sopwith, Spad, and Nieuport, have
short noses, making them difficult to
05sig1.QXD 3/25/09 9:37 AM Page 21
22 MODEL AVIATION
balance on the CG without adding lots of
weight to the nose. I don’t like to add
weight to an aircraft if I don’t have to.
I enjoy converting a simple kit-built
airplane to a realistic, scalelike airplane.
This includes adding many details:
authentic color-and-markings, weapons,
cockpit, pilot, etc. With most WW I
fighters, you can add wing wires, realistic
landing gear, open cockpits, and exposed
engine details to that list.
I’ll take you through some of the issues
Left: The flying wires are double-stranded.
An Aldis gun sight is aimed to account for
the high-mounted Lewis and Vickers guns. A
long exhaust pipe was a comfort to pilots.
With a grand lake view as the backdrop, you can appreciate the detail of the
empennage showing the cable brace attachments, rudder pull-pull cable, and
elevator cable. Fuselage “stitching” is also visible.
Flair Models S.E.5a Specifications
Type: Sport Scale vintage
Building skill level: Expert
Flying skill level: Intermediate to expert
Wingspan: 51 inches
Length: 39 inches
Wing area: 1,025 square inches
Flying weight: 6.9 pounds
CG position: 11cm back from top-wing LE
Power system: AstroFlight 25 motor with Superbox, Castle Creations Griffin-40
ESC, 15 x 10E APC propeller, Tanic 5S 15-20C 3650 mAh Li-Poly battery
Radio: Futaba 9CAP transmitter, Hitec 555 receiver, four Hitec HS-81MG servos
Engine: .35-.45 two-stroke or .40-.60 four-stroke
05sig1.QXD 3/25/09 10:26 AM Page 22
I had to confront while converting the
Flair Models S.E.5a to a scale-looking,
electric-powered model.
To build a scale model, you must
decide what full-scale subject you want
and then develop a documentation package
for that airplane. I selected a beautiful
S.E.5a replica (serial number C6457) that
is located in the “Personal Courage Wing”
of the Museum of Flight in Seattle,
Washington.
I wanted to replicate this airplane as
closely as I could. A good friend and
fellow modeler, who is a docent at the
museum, provided me with an opportunity
to take many close-up photographs of the
S.E.5a as the basis for my documentation.
The Flair Models S.E.5a is your basic,
old-fashioned, die-cut balsa-and-plywood
kit—nothing fancy. It contains strip and
sheet wood, precut wing ribs and formers,
glow engine-mounting hardware, hardware
pack, plans, and instructions.
The plans are excellent; the instructions
would benefit from illustrations and a few
more details. The die-cutting was
generally good, but I had to do some razor
blade work on several of the plywood
parts. The wood quality was fair.
Electric Power-System Design: The fullscale
S.E.5a’s top speed, with the
Wolseley Viper V8 engine, was 138 mph.
This translates to a 1/6-scale top speed in
the neighborhood of only 23 mph. So I
was not interested in a hopped-up motor
configuration to deliver high power
loadings; I wanted only to replicate scale
speed as closely as possible.
I had to make some educated guesses. I
reckoned that if I could design a power
system that would generate roughly 70-80
watts per pound, I would probably achieve
scalelike flight with this high-drag
airplane.
I estimated the model’s all-up weight,
including a Li-Poly battery pack, to be
6.5-7.0 pounds. A scale propeller would
be approximately 16 inches long. I had a
surplus AstroFlight 25 motor with a 3.1:1-
geared Superbox that I wanted to use.
I estimated, from experience, that I
would need 18-20 volts from the battery
pack. Using these figures, I ran some
simulations with ElectriCalc (electricpower
software). According to the runs,
using a 16 x 10 APC electric propeller
with this motor and battery pack, I could
expect to draw 44 amps and generate close
to 81 watts of power per pound of model.
Dropping back to a 15 x 10 propeller
would reduce the current draw to roughly
40 amps and power to 75 watts per pound.
I decided to go with the 15 x 10, and I was
aware that switching propellers later if
needed would be simple.
Detailing the S.E.5a: Both wings and the
tail feathers went together easily. The ribs
cut from plywood were quite strong. I
used a square to align all of the parts as I
built them over the plans using pins.
I used a glue that is new to me and that
I highly recommend: Titebond’s Molding
and Trim Wood Glue. It is an aliphatic
glue but is thicker than traditional
carpenter’s glue and sets up rapidly. The
hardware store had to special-order it for
me.
Rather than using the nylon control
horns the kit provided, I made scalelike
control horns from 1/16-inch circuit-board
material. I glued several predrilled spruce
blocks into the wings, to serve as strong
fastening points for the wing wires.
I used cyanoacrylate hinges
throughout, rather than the hinges
included with the kit. I glued a 1/16 balsa
strip on the upper center of the upper wing
to later serve as a mounting plate for the
Lewis machine gun. To improve the scale
appearance, I added a partial wing rib to
the LE between each existing rib.
Rather than use one centrally mounted
servo with pushrods and bellcranks for the
ailerons, I installed a Hitec HS-81MG
servo in each wing. Servo extensions ran
through the wings, exiting at the center
where they engaged the aileron Y
connector.
The S.E.5a contains a maze of wires
running among struts, the fuselage,
cabanes, and tail sections. Just sorting
them all and identifying them was a
challenge. I would not have been able to
do it without the museum photos.
I began by sketching the wires on
paper. Then, before covering the wings
and fuselage, I embedded a 1/2-inch square
hardwood block at each point at which a
wire was connected. Each block was
predrilled with a 1/16-inch hole. Before
painting the model, I poked a small hole in
the covering at each attachment point to
mark its location.
With the fuselage, a challenge was
mounting the battery pack and motor.
With a monoplane, I would normally
construct a removable hatch forward of the
canopy to create a battery compartment.
That was out of the question with this
biplane, owing to the location of the
cabane struts and support wires.
Therefore, I decided to make a
removable nose that would slide into the
fuselage from the front and provide access
to the motor and the battery tray. I
mounted the motor with cable ties fastened
around two metal bolts in the lower nose.
The full-scale S.E.5a’s turtledeck has
several shorter stringers just aft of the
cockpit. I added these using basswood
strips. I mounted the servos just aft of the
cockpit and a Hitec Micro 555 receiver
beneath it. A removable 1/16 plywood belly
plate screws to the bottom of the fuselage
to conceal these components.
The elevator is actuated with a metal
rod that protrudes down into the rear of the
fuselage from the elevator torsion bar to
engage the pushrod. I installed fake cables
on the elevator to simulate the cable
arrangement.
The rudder works with a pull-pull cable
system. The rudder servo turns a bellcrank
inside the fuselage just forward of the
rudder. To this bellcrank I attached two
sets of pull-pull wires: one serving the
rudder the other serving the steerable tail
skid.
Landing gear was constructed from 1/8-
inch-diameter steel wire faired with 1/4
hard balsa. Springs were made from
bungee cord wrapped around the axle and
strut, to give a spring effect upon landing.
The 41/2-inch-diameter scale wheels are
from Williams Brothers.
The full-scale S.E.5a’s nose is mostly
metal and wood, and the fuselage aft of
the cockpit is fabric-covered stringers.
Wings and tail surfaces are covered with
fabric.
On the model, I made the nose portions
of the fuselage from either #250 brass
sheet or 1/16 balsa sheeting. I covered the
balsa with GM (gas model)-grade Silkspan
and covered it several times with nitrate
dope to smooth the grain.
I covered the aft fuselage, wings, and
empennage with Nelson Hobby
Specialties’ LiteFAB Natural iron-on
fabric. As on the full-scale S.E.5a and
many other WW I airplanes, the fabric was
bound to the ribs using twine. The ribs
were then covered with strips of pinked
fabric.
The twine was simulated using lines of
wood glue applied with a syringe with a
1/8-inch-diameter brass tube in its nose; I
also simulated the many fuselage rivets
with this method. Each line ran across the
rib cover, spaced 1/2 inch apart.
I applied this technique to the top and
bottom of both wings and tail surfaces.
Then I overlaid the rib covers with 1/2-
inch-wide pinked fabric strips, available
from F&M Enterprises.
The entire model was sealed with
several coats of nontautening nitrate dope
from Aerodyne. The full-scale S.E.5a was
painted with a color known as PC-10,
while the undersides of both wings and
elevator were doped fabric. PC-10 is a
green drab color that airplane painters
often made on-site; there is no specific
formula for it.
To simulate PC-10, I took some of my
photos of the full-scale S.E.5a to a
Benjamin Moore paint store to have the
color matched. It turned out nearly perfect,
and I had a quart of interior latex eggshell
paint of the color made.
I thinned it at roughly 9:1 paint to
water and applied three coats with a
paintbrush, trying to replicate a rough,
hand-painted surface. (They didn’t use
airbrushes in WW I.)
Wing markings were a challenge. I had
ordered roundel decals from an Internet
source but realized that I could not apply
them because of the roughness of the
fabric cover strips and ties. Fortunately I
had not yet applied the PC-10 to the
wings, so I drew the roundels on the
doped fabric with a pencil and painted
them by hand using thinned latex paint.
I painted the wings after applying the
roundels. On the underside of the bottom
wings, I hand-painted the roundels over
the doped fabric.
Final Touches: Someone once said that
an S.E.5a viewed from the front looked
like a farm tractor with wings. The
Wolseley Viper V8’s valve covers and
exhaust manifolds protrude from the nose.
Exhaust pipes connect to the manifold and
extend aft to beneath the cockpit opening.
I carved the pipes from balsa, added tiny
brass bolts, and simulated spark plugs to
the valve covers.
When the model was fully assembled, I
attached the wing and tail wires using
0.014-inch fine braided beading wire from
the Soft Flex Company. I connected the
wires to the wood attachment blocks using
spring clasp connecting tabs (item FI104-
G) from Shipwreck Beads.
The clasps were screwed into the
wooden block using #2 x 3/8-inch buttonhead
screws. The wire ends were passed
through the tabs and swaged together
using 0.033 Mason Connector Sleeves
from Thorn Brothers that I bound with a
crimping tool.
After adding a few final details, such
as the wing-mounted Lewis machine gun
and rack, homemade pitot tube, Aldis gun
sight, instrument panel, scale propeller,
and windshield, the model was finished.
Static Testing: I performed a static test
on the power system using a 5S 3650 Li-
Poly battery and a 15 x 8E APC propeller.
At full throttle, the system drew 30 amps
of current and produced 600 watts of
power with the propeller spinning at 4,590
rpm.
The S.E.5a’s all-up weight was 6.94
pounds, so the power loading was 86 watts
per pound. By moving the battery tray all
the way forward, I achieved a CG that was
right on the mark: 11 centimeters (4.3
inches) back from the upper wing’s LE,
without adding weight.
I set the control throws so that the
aileron had 20mm up and 10mm down,
the elevator had roughly 15mm, and the
rudder had approximately 20mm. I used
only low rates and dialed in close to 35%
exponential on each control surface.
Flying: Uncertain of how the S.E.5a
would perform in the air, I waited for a
warm, relatively calm spring day for the
maiden flight. Our grass field is quite
bumpy, but the model rolled over it at a
good clip, hardly bouncing around at all. I
attribute this to the effective bungee
springs on the landing gear.
The airplane lifted off easily and
smoothly and, following a touch of downtrim,
flew gracefully as I made shallow
turns and slow passes around the field. I
handed the transmitter to my flying buddy,
Bob Benjamin, who brought it around for
a few low passes while I clicked away
with my Canon Rebel SLR camera.
With the shooting finished, I retrieved
the controls and brought the S.E.5a in for
a slow, power-off landing. A touch of
power at the end prevented it from
flipping over in the grass. The first flight
revealed that the airplane was a bit
underpowered, so I replaced the 15 x 8
propeller with a 15 x 10, which helped
somewhat.
As of this writing, I have nearly 50
successful flights on my model. It
performs extremely smoothly and with
great authority—similar to a full-scale
S.E.5a.
Turns are more scalelike if they are
initiated with the rudder and a touch of
down-elevator. It is important that the CG
is set properly; the airplane becomes a
beast when it’s even slightly tail-heavy.
Flair Again? This project required almost
three years to complete but was well worth
the considerable effort. It is absolutely
beautiful, exhilarating to fly, and took first
place in a local scale contest last summer.
The many advantages of electric power
are apparent with models such as this.
There is no protruding cylinder head or
muffler to spoil the lovely nose detail. Can
you imagine what a mess it would be to
clean the glow-engine oil out of the
cockpit, wing wires, machine guns, and
other scale details? And keeping the
lifelike fabric pilot dry would be
impossible.
Add to all that the ease of starting and
restarting the motor, the ability to use
water-based paint on the fabric, the total
lack of vibration, and, oh yes, the low
noise-impact flight. Electric power is a
great way to go with scale! MA
Gary A. Ritchie
[email protected]
Sources:
Flair Models Ltd.
www.flairmodels.co.uk
Radical RC
(937) 256-7727
www.radicalrc.com
AstroFlight
(310) 821-6242
www.astroflight.com
Williams Brothers Model Products
(512) 352-9346
www.williamsbrothersmodelproducts.com
Nelson’s Hobby
(817) 431-9898
www.nelsonhobby.com
F&M Enterprises
(817) 279-8045
www.stits.com
Aerodyne
www.freeflightmodels.com
Soft Flex Company
(800) 925-FLEX
www.softflexcompany.com
Shipwreck Beads
(800) 950-4232
www.shipwreckbeads.com
Thorn Brothers
(763) 572-3782
www.thornebros.com

May 2009 19
by Gary A. Ritchie
Electric conversion and scale-up
of the great Flair Models kit
A COUPLE OF years ago, I scratch-built
a 1/8-scale British Royal Aircraft Factory
S.E.5a World War I fighter. After flying
this little airplane with a motor for roughly
two years, I became so fond of it that I
decided to build an S.E.5a for a .40-size
engine (approximately 1/6 scale) and
convert it to electric power.
Left: The serial number C6457 S.E.5a on
display in the “Personal Courage Wing” of
the Museum of Flight in Seattle WA.
The S.E.5a passes overhead
during the maiden flight.
05sig1.QXD 3/25/09 9:28 AM Page 19
20 MODEL AVIATION
Gary’s early work on the model’s fuselage shows where the
battery tray, with Velcro strips, and aluminum cabane struts are
located.
The S.E.5a’s “springs” are made from bungee cords that wrap
around the axles. They are highly effective during takeoff and
landing.
Spruce tie-down blocks are embedded for wing wires in the wings
before covering. In this case, the block also serves as a mount for
the metal wing-strut tab.
The author hand-painted the insignia with latex house paint that
was mixed to match the authentic WW I British colors.
Wing struts attach to steel straps embedded in the
wing. The pitot tube details include rubber couplers to
the metal tubing.
Gary fashioned the motor cover and details from thin brass sheets. The
piano hinges are simulated, and rivets are made using wood glue.
Photos by the author
05sig1.QXD 3/25/09 10:17 AM Page 20
May 2009 21
Looking up from beneath the nose, it is possible to see the
simulated spark plugs and some forward fuselage details.
Right: A bellcrank mounted in the rear
fuselage controls both the pull-pull rudder
and the pull-pull tail skid. Four Hitec HS-
81MG servos are used.
A Lewis machine gun rests on its rack. Thin aluminum tubes
running down the wings imitate overflow pipes from the wingmounted
internal gas tank.
The AstroFlight 25 brushed motor is test-fitted before being
attached with two cable ties. The battery tray and Velcro
fasteners are visible behind the motor.
Fabric tie-down twine, shown on the bottom of the upper wing, is
simulated with thin glue strips. Pinked fabric covers were doped
over these tie-downs.
Aileron cables are produced from wires that slide in and out of a
piece of brass tubing that is embedded in the wing.
For this project, I selected the version
that Flair Models produces in the United
Kingdom and Radical RC markets in the
US. This is a kit—not an ARF.
A significant modeling advantage that
the S.E.5a has over many WW I fighters is
that it has a relatively long nose. This
provides ample room for a motor and a
battery pack.
Other attractive WW I biplanes, such
as the Sopwith, Spad, and Nieuport, have
short noses, making them difficult to
05sig1.QXD 3/25/09 9:37 AM Page 21
22 MODEL AVIATION
balance on the CG without adding lots of
weight to the nose. I don’t like to add
weight to an aircraft if I don’t have to.
I enjoy converting a simple kit-built
airplane to a realistic, scalelike airplane.
This includes adding many details:
authentic color-and-markings, weapons,
cockpit, pilot, etc. With most WW I
fighters, you can add wing wires, realistic
landing gear, open cockpits, and exposed
engine details to that list.
I’ll take you through some of the issues
Left: The flying wires are double-stranded.
An Aldis gun sight is aimed to account for
the high-mounted Lewis and Vickers guns. A
long exhaust pipe was a comfort to pilots.
With a grand lake view as the backdrop, you can appreciate the detail of the
empennage showing the cable brace attachments, rudder pull-pull cable, and
elevator cable. Fuselage “stitching” is also visible.
Flair Models S.E.5a Specifications
Type: Sport Scale vintage
Building skill level: Expert
Flying skill level: Intermediate to expert
Wingspan: 51 inches
Length: 39 inches
Wing area: 1,025 square inches
Flying weight: 6.9 pounds
CG position: 11cm back from top-wing LE
Power system: AstroFlight 25 motor with Superbox, Castle Creations Griffin-40
ESC, 15 x 10E APC propeller, Tanic 5S 15-20C 3650 mAh Li-Poly battery
Radio: Futaba 9CAP transmitter, Hitec 555 receiver, four Hitec HS-81MG servos
Engine: .35-.45 two-stroke or .40-.60 four-stroke
05sig1.QXD 3/25/09 10:26 AM Page 22
I had to confront while converting the
Flair Models S.E.5a to a scale-looking,
electric-powered model.
To build a scale model, you must
decide what full-scale subject you want
and then develop a documentation package
for that airplane. I selected a beautiful
S.E.5a replica (serial number C6457) that
is located in the “Personal Courage Wing”
of the Museum of Flight in Seattle,
Washington.
I wanted to replicate this airplane as
closely as I could. A good friend and
fellow modeler, who is a docent at the
museum, provided me with an opportunity
to take many close-up photographs of the
S.E.5a as the basis for my documentation.
The Flair Models S.E.5a is your basic,
old-fashioned, die-cut balsa-and-plywood
kit—nothing fancy. It contains strip and
sheet wood, precut wing ribs and formers,
glow engine-mounting hardware, hardware
pack, plans, and instructions.
The plans are excellent; the instructions
would benefit from illustrations and a few
more details. The die-cutting was
generally good, but I had to do some razor
blade work on several of the plywood
parts. The wood quality was fair.
Electric Power-System Design: The fullscale
S.E.5a’s top speed, with the
Wolseley Viper V8 engine, was 138 mph.
This translates to a 1/6-scale top speed in
the neighborhood of only 23 mph. So I
was not interested in a hopped-up motor
configuration to deliver high power
loadings; I wanted only to replicate scale
speed as closely as possible.
I had to make some educated guesses. I
reckoned that if I could design a power
system that would generate roughly 70-80
watts per pound, I would probably achieve
scalelike flight with this high-drag
airplane.
I estimated the model’s all-up weight,
including a Li-Poly battery pack, to be
6.5-7.0 pounds. A scale propeller would
be approximately 16 inches long. I had a
surplus AstroFlight 25 motor with a 3.1:1-
geared Superbox that I wanted to use.
I estimated, from experience, that I
would need 18-20 volts from the battery
pack. Using these figures, I ran some
simulations with ElectriCalc (electricpower
software). According to the runs,
using a 16 x 10 APC electric propeller
with this motor and battery pack, I could
expect to draw 44 amps and generate close
to 81 watts of power per pound of model.
Dropping back to a 15 x 10 propeller
would reduce the current draw to roughly
40 amps and power to 75 watts per pound.
I decided to go with the 15 x 10, and I was
aware that switching propellers later if
needed would be simple.
Detailing the S.E.5a: Both wings and the
tail feathers went together easily. The ribs
cut from plywood were quite strong. I
used a square to align all of the parts as I
built them over the plans using pins.
I used a glue that is new to me and that
I highly recommend: Titebond’s Molding
and Trim Wood Glue. It is an aliphatic
glue but is thicker than traditional
carpenter’s glue and sets up rapidly. The
hardware store had to special-order it for
me.
Rather than using the nylon control
horns the kit provided, I made scalelike
control horns from 1/16-inch circuit-board
material. I glued several predrilled spruce
blocks into the wings, to serve as strong
fastening points for the wing wires.
I used cyanoacrylate hinges
throughout, rather than the hinges
included with the kit. I glued a 1/16 balsa
strip on the upper center of the upper wing
to later serve as a mounting plate for the
Lewis machine gun. To improve the scale
appearance, I added a partial wing rib to
the LE between each existing rib.
Rather than use one centrally mounted
servo with pushrods and bellcranks for the
ailerons, I installed a Hitec HS-81MG
servo in each wing. Servo extensions ran
through the wings, exiting at the center
where they engaged the aileron Y
connector.
The S.E.5a contains a maze of wires
running among struts, the fuselage,
cabanes, and tail sections. Just sorting
them all and identifying them was a
challenge. I would not have been able to
do it without the museum photos.
I began by sketching the wires on
paper. Then, before covering the wings
and fuselage, I embedded a 1/2-inch square
hardwood block at each point at which a
wire was connected. Each block was
predrilled with a 1/16-inch hole. Before
painting the model, I poked a small hole in
the covering at each attachment point to
mark its location.
With the fuselage, a challenge was
mounting the battery pack and motor.
With a monoplane, I would normally
construct a removable hatch forward of the
canopy to create a battery compartment.
That was out of the question with this
biplane, owing to the location of the
cabane struts and support wires.
Therefore, I decided to make a
removable nose that would slide into the
fuselage from the front and provide access
to the motor and the battery tray. I
mounted the motor with cable ties fastened
around two metal bolts in the lower nose.
The full-scale S.E.5a’s turtledeck has
several shorter stringers just aft of the
cockpit. I added these using basswood
strips. I mounted the servos just aft of the
cockpit and a Hitec Micro 555 receiver
beneath it. A removable 1/16 plywood belly
plate screws to the bottom of the fuselage
to conceal these components.
The elevator is actuated with a metal
rod that protrudes down into the rear of the
fuselage from the elevator torsion bar to
engage the pushrod. I installed fake cables
on the elevator to simulate the cable
arrangement.
The rudder works with a pull-pull cable
system. The rudder servo turns a bellcrank
inside the fuselage just forward of the
rudder. To this bellcrank I attached two
sets of pull-pull wires: one serving the
rudder the other serving the steerable tail
skid.
Landing gear was constructed from 1/8-
inch-diameter steel wire faired with 1/4
hard balsa. Springs were made from
bungee cord wrapped around the axle and
strut, to give a spring effect upon landing.
The 41/2-inch-diameter scale wheels are
from Williams Brothers.
The full-scale S.E.5a’s nose is mostly
metal and wood, and the fuselage aft of
the cockpit is fabric-covered stringers.
Wings and tail surfaces are covered with
fabric.
On the model, I made the nose portions
of the fuselage from either #250 brass
sheet or 1/16 balsa sheeting. I covered the
balsa with GM (gas model)-grade Silkspan
and covered it several times with nitrate
dope to smooth the grain.
I covered the aft fuselage, wings, and
empennage with Nelson Hobby
Specialties’ LiteFAB Natural iron-on
fabric. As on the full-scale S.E.5a and
many other WW I airplanes, the fabric was
bound to the ribs using twine. The ribs
were then covered with strips of pinked
fabric.
The twine was simulated using lines of
wood glue applied with a syringe with a
1/8-inch-diameter brass tube in its nose; I
also simulated the many fuselage rivets
with this method. Each line ran across the
rib cover, spaced 1/2 inch apart.
I applied this technique to the top and
bottom of both wings and tail surfaces.
Then I overlaid the rib covers with 1/2-
inch-wide pinked fabric strips, available
from F&M Enterprises.
The entire model was sealed with
several coats of nontautening nitrate dope
from Aerodyne. The full-scale S.E.5a was
painted with a color known as PC-10,
while the undersides of both wings and
elevator were doped fabric. PC-10 is a
green drab color that airplane painters
often made on-site; there is no specific
formula for it.
To simulate PC-10, I took some of my
photos of the full-scale S.E.5a to a
Benjamin Moore paint store to have the
color matched. It turned out nearly perfect,
and I had a quart of interior latex eggshell
paint of the color made.
I thinned it at roughly 9:1 paint to
water and applied three coats with a
paintbrush, trying to replicate a rough,
hand-painted surface. (They didn’t use
airbrushes in WW I.)
Wing markings were a challenge. I had
ordered roundel decals from an Internet
source but realized that I could not apply
them because of the roughness of the
fabric cover strips and ties. Fortunately I
had not yet applied the PC-10 to the
wings, so I drew the roundels on the
doped fabric with a pencil and painted
them by hand using thinned latex paint.
I painted the wings after applying the
roundels. On the underside of the bottom
wings, I hand-painted the roundels over
the doped fabric.
Final Touches: Someone once said that
an S.E.5a viewed from the front looked
like a farm tractor with wings. The
Wolseley Viper V8’s valve covers and
exhaust manifolds protrude from the nose.
Exhaust pipes connect to the manifold and
extend aft to beneath the cockpit opening.
I carved the pipes from balsa, added tiny
brass bolts, and simulated spark plugs to
the valve covers.
When the model was fully assembled, I
attached the wing and tail wires using
0.014-inch fine braided beading wire from
the Soft Flex Company. I connected the
wires to the wood attachment blocks using
spring clasp connecting tabs (item FI104-
G) from Shipwreck Beads.
The clasps were screwed into the
wooden block using #2 x 3/8-inch buttonhead
screws. The wire ends were passed
through the tabs and swaged together
using 0.033 Mason Connector Sleeves
from Thorn Brothers that I bound with a
crimping tool.
After adding a few final details, such
as the wing-mounted Lewis machine gun
and rack, homemade pitot tube, Aldis gun
sight, instrument panel, scale propeller,
and windshield, the model was finished.
Static Testing: I performed a static test
on the power system using a 5S 3650 Li-
Poly battery and a 15 x 8E APC propeller.
At full throttle, the system drew 30 amps
of current and produced 600 watts of
power with the propeller spinning at 4,590
rpm.
The S.E.5a’s all-up weight was 6.94
pounds, so the power loading was 86 watts
per pound. By moving the battery tray all
the way forward, I achieved a CG that was
right on the mark: 11 centimeters (4.3
inches) back from the upper wing’s LE,
without adding weight.
I set the control throws so that the
aileron had 20mm up and 10mm down,
the elevator had roughly 15mm, and the
rudder had approximately 20mm. I used
only low rates and dialed in close to 35%
exponential on each control surface.
Flying: Uncertain of how the S.E.5a
would perform in the air, I waited for a
warm, relatively calm spring day for the
maiden flight. Our grass field is quite
bumpy, but the model rolled over it at a
good clip, hardly bouncing around at all. I
attribute this to the effective bungee
springs on the landing gear.
The airplane lifted off easily and
smoothly and, following a touch of downtrim,
flew gracefully as I made shallow
turns and slow passes around the field. I
handed the transmitter to my flying buddy,
Bob Benjamin, who brought it around for
a few low passes while I clicked away
with my Canon Rebel SLR camera.
With the shooting finished, I retrieved
the controls and brought the S.E.5a in for
a slow, power-off landing. A touch of
power at the end prevented it from
flipping over in the grass. The first flight
revealed that the airplane was a bit
underpowered, so I replaced the 15 x 8
propeller with a 15 x 10, which helped
somewhat.
As of this writing, I have nearly 50
successful flights on my model. It
performs extremely smoothly and with
great authority—similar to a full-scale
S.E.5a.
Turns are more scalelike if they are
initiated with the rudder and a touch of
down-elevator. It is important that the CG
is set properly; the airplane becomes a
beast when it’s even slightly tail-heavy.
Flair Again? This project required almost
three years to complete but was well worth
the considerable effort. It is absolutely
beautiful, exhilarating to fly, and took first
place in a local scale contest last summer.
The many advantages of electric power
are apparent with models such as this.
There is no protruding cylinder head or
muffler to spoil the lovely nose detail. Can
you imagine what a mess it would be to
clean the glow-engine oil out of the
cockpit, wing wires, machine guns, and
other scale details? And keeping the
lifelike fabric pilot dry would be
impossible.
Add to all that the ease of starting and
restarting the motor, the ability to use
water-based paint on the fabric, the total
lack of vibration, and, oh yes, the low
noise-impact flight. Electric power is a
great way to go with scale! MA
Gary A. Ritchie
[email protected]
Sources:
Flair Models Ltd.
www.flairmodels.co.uk
Radical RC
(937) 256-7727
www.radicalrc.com
AstroFlight
(310) 821-6242
www.astroflight.com
Williams Brothers Model Products
(512) 352-9346
www.williamsbrothersmodelproducts.com
Nelson’s Hobby
(817) 431-9898
www.nelsonhobby.com
F&M Enterprises
(817) 279-8045
www.stits.com
Aerodyne
www.freeflightmodels.com
Soft Flex Company
(800) 925-FLEX
www.softflexcompany.com
Shipwreck Beads
(800) 950-4232
www.shipwreckbeads.com
Thorn Brothers
(763) 572-3782
www.thornebros.com