146 MODEL AVIATION
ELECTRIC-POWERED FF has been
around for almost 50 years. In the 1959-61
Model Aeronautic Year Book by Frank
Zaic, Fred Militky described his electric
experiments from 1940 to 1959. After
almost 20 years of experimentation he
finally achieved a successful flight with his
Silentius: a 30-inch-span model that
weighed 5 ounces.
If I remember correctly, some variation
of that design was later kitted by Graupner,
for which Fred was the designer. In the
early 1970s Mattel introduced its Super
Star foam RTF electric-powered FF model
that featured programmable flight using
cams.
Although electric power offered a quiet,
easy-starting, no-mess alternative to glowignition
power, it never seemed to catch on
as an event in FF. Batteries were heavy,
and high-revving motors needed gears to be
effective.
The two AMA electric FF events have
been lightly supported, with only a few
modelers, such as Charles Groth, willing to
spend the necessary research time to
develop electric power systems (motor,
gearing, propeller, and battery) and
compatible models.
However, in RC electric has become a
popular power source for models ranging
from park flyers to sailplanes. The strong
interest and large market have made a
variety of electric motors, batteries, and
propellers available at reasonable prices.
Interest in developing an FAI class
began growing a few years ago. The idea
was to create an event that would offer
some of the excitement of F1C without the
noise and the grace of F1B without the cost
of rubber.
The rules were thrashed out informally
via E-mail by a group that included Aram
Schlosberg, Ross Jahnke, Charles Groth,
Dan Tracy, and Tapio Linkosalo. Their
proposal was approved in March 2005.
In creating the rules for any FF event,
the most important question is how best to
limit performance. The climb phase of the
flight can be limited by reducing power
(e.g., by limiting the displacement of the
engine, the weight of the rubber motor, or
the length and elasticity of the towline) or,
in the case of internal-combustion engines,
by limiting the motor run.
The rate of sink in the glide phase can
be increased by enlarging the wing loading
or total surface loading of the model (as in
F1A, F1B, and F1C) by limiting its
wingspan (as in P-30) or requiring a
minimum aircraft weight. (Model weight
also affects climb; heavier models with the
same power don’t fly as high.)
The new FAI F1Q electric-powered FF event is explained
[[email protected]]
Free Flight Duration Louis Joyner
Charles Groth’s new, smaller model shows the removable cone which contains the
motor, extension shaft, and propeller. Dental bands hold the cone in place.
Charles Groth’s AMA electric-powered Big Red design would be a good starting place for
the new FAI F1Q electric FF event. Drawing by Jim O’Reilly.
The more restrictive the rules are, the
more a premium is placed on model design
and construction and the fewer the
available optimum design choices.
Categories such as F1A Towline, F1B
Wakefield Rubber, and F1C Power, which
have strictly written rules for total surface
area and weight, have each evolved into an
event in which the aircraft are similar in
design and use carbon-fiber composite
construction.
On the other hand, the F1G Coupe rules
specify only rubber motor weight and total
model weight. The result is a much wider
variety of model sizes, design approaches,
and construction methods.
Coupe wings can range from as small as
120 square inches to well in excess of 250
square inches. Construction can be
conventional balsa and tissue, carbon
composite, or almost any combination in
between.
In developing the rules for F1Q, the
decision was to keep things simple. The
battery weight is limited to a maximum of 125 grams for Ni-Cd
and NiMH and a maximum of 90 grams for Li-Ion/Poly batteries.
The maximum motor run is 25 seconds. There are no model area
or weight restrictions. As in F1A, F1B, and F1C, F1Q is flown in
seven rounds with 180-second maxes.
You can find complete rules for the F1Q event on the National
Free Flight Society Web site (http://freeflight.org) or the FAI
Web site (www.fai.org/aeromodelling/documents/sc4.asp).
The two AMA electric events also have simple rules; the only
limitation is on the batteries. A maximum of 1.5 volts per cell is
allowed. Class A models use six cells or less and Class B models
use more than six cells.
With an event such as F1Q in which there are no restrictions
on airplane size or weight, the big question is where to start.
“I’m starting from the electric motor and designing a model
around it,” says Aram Schlosberg. But what motor?
I asked Charles Groth, who is perhaps the most experienced
FF electric modeler in the country, for his suggestions. (His Natswinning
electric-powered Big Red was voted a Model of the Year
and featured in the 2004 NFFS Symposium.) He said:
February 2006 147
Big Red’s RC electric propeller blades are mounted in machined Delrin hub. Rubber
bands hold blades in folded position; centrifugal force opens them when the motor starts.
The Hacker A20 outrunner-style motor mounts to an aluminum
plate at the rear of the balsa cone, providing easy access.
Frank’s model uses a Hyperion Z2213-24 outrunner motor turning
an 11 x 6 folding propeller. Timer mounted below wing controls
auto functions.
Frank Ivers modified a 6-foot-span electric sailplane for FF. It has a
two-piece wing for easy transport. Robert Sisson photo.
The best combination for the serious
beginner at this time is probably different
from my [geared] system because of the
advent of a type of motor we call the
outrunner, which appears to make gears
unnecessary. Both static tests on a
dynamometer and flight tests show great
promise.”
The power package Charles suggests for a
starting point is a Hacker A20 34S motor,
Graupner 8 x 4.5 folding blades, a Phoenix-
10 brushless motor controller, and six SR
Batteries 190 Series Ni-Cd cells. He uses an
electronic timer of his own design for motor
run and dethermalizing. He also machined
the hub for the folding propeller from Delrin.
The total weight of the power package is
just less than 4 ounces. The battery weight is
approximately 60 grams, which is well below
the allowable 125 grams.
The cost breakdown is motor, $60;
battery, $33; controller, $60; and blades,
roughly $9. Charles makes and sells the
electronic timer and propeller hubs. For
information E-mail him at flodyn@
yahoo.com.
What about the model? A good rule of
thumb is that the airframe weight should be
equal to the power-package weight. That
would result in a model that would weigh
approximately the same as an F1B Wakefield
or a 1/2A Gas model with a wing area of 250-
350 square inches.
However, there are a variety of options.
Aram Schlosberg saidNippert modified a gas kit, while Dick Ivers
has bought an RC electric-powered model
and flies it as a Free Flight. Others—Dick
and some Finns—have started from a
Wakefield.
“However, a Wakefield might be underarea
given the battery/controller/motor
weight. My approach was to build something
like a Power model from the 1960s.”
Aram suggests Ernö Frigyes’ Taltos F1C
design, which won the 1963 World
Championships. The 61-inch-span model
uses a modified Benedek B-8353b airfoil.
There are three-view drawings in the 1964-
65 Model Aeronautic Year Book.
Frank Zaic did a detailed analysis of the
model’s climb characteristics in his Circular
Airflow and Model Aircraft. (The Taltos was
one of the first winning deigns to use auto
stabilizer and auto rudder to control the flight
path under power.) The Zaic Year Books are
available from AMA.
Using a larger motor and the maximum
allowable battery weight is basically what
Charles Groth has done with his Natswinning
Big Red. In its six-cell Class A
configuration it meets the 125-gram
maximum battery weight and has an all-up
weight of 18.5 ounces. The wing area is 615
square inches.
The model uses a geared motor to swing
a 16-inch-diameter propeller. A nose
extension prevents a folded blade from
hitting the wing. (Using the higher-torque
outrunner type of motor would eliminate the
need for gears and allow a smaller propeller
and slightly shorter nose. But the geared
motor may have a slight edge in
performance.)
Dick Ivers’ model is an Omega 1.8E Poly
RC electric-powered sailplane from
Northeast Sailplane Products. It spans 72
inches, has a wing area of 455 square inches,
and uses an SD 7036 airfoil. The wingconstruction uses a carbon-fiber D-box.
Power is a Hyperion Z2213-24 brushless
outrunner turning an Aeronaut 11 x 6
propeller with folding blades. The battery is a
Thunder Power ProLite Li-Poly weighing
88.7 grams with connectors. All-up weight is
roughly 19 ounces. To control the power
pattern Dick uses timer-activated auto
stabilizer and auto rudder. He said:
“The stabilizer and rudder move a few
seconds after motor shutdown. The model is
moving too fast to move the auto surfaces
during the motor run.
“These airplanes are closer to F1C or F1J
than to F1B. Of course you could start with a
lighter battery, with less power, and scale
down the model size. I tried the approach of a
Wakefield conversion with only modest
success. The airfoil is wrong for the speed
involved.”
(Wakefield Rubber models typically have
higher-camber wing airfoils than Power
models.)
With the wide variety of design options,
the availability of motors, and the challenge
of breaking new ground, F1Q should be an
exciting event. The reduced noise should
allow models to be flown on some close-in
fields that would not allow gas-powered
models. Get building. MA
Sources:
Hacker motors
www.hackerbrushless.com
SR Batteries batteries
www.srbatteries.com
Castle Creations Phoenix-10 controller
www.castlecreations.com
Omega 1.8E Poly sailplane
Edition: Model Aviation - 2006/02
Page Numbers: 146,147,148,149
Edition: Model Aviation - 2006/02
Page Numbers: 146,147,148,149
146 MODEL AVIATION
ELECTRIC-POWERED FF has been
around for almost 50 years. In the 1959-61
Model Aeronautic Year Book by Frank
Zaic, Fred Militky described his electric
experiments from 1940 to 1959. After
almost 20 years of experimentation he
finally achieved a successful flight with his
Silentius: a 30-inch-span model that
weighed 5 ounces.
If I remember correctly, some variation
of that design was later kitted by Graupner,
for which Fred was the designer. In the
early 1970s Mattel introduced its Super
Star foam RTF electric-powered FF model
that featured programmable flight using
cams.
Although electric power offered a quiet,
easy-starting, no-mess alternative to glowignition
power, it never seemed to catch on
as an event in FF. Batteries were heavy,
and high-revving motors needed gears to be
effective.
The two AMA electric FF events have
been lightly supported, with only a few
modelers, such as Charles Groth, willing to
spend the necessary research time to
develop electric power systems (motor,
gearing, propeller, and battery) and
compatible models.
However, in RC electric has become a
popular power source for models ranging
from park flyers to sailplanes. The strong
interest and large market have made a
variety of electric motors, batteries, and
propellers available at reasonable prices.
Interest in developing an FAI class
began growing a few years ago. The idea
was to create an event that would offer
some of the excitement of F1C without the
noise and the grace of F1B without the cost
of rubber.
The rules were thrashed out informally
via E-mail by a group that included Aram
Schlosberg, Ross Jahnke, Charles Groth,
Dan Tracy, and Tapio Linkosalo. Their
proposal was approved in March 2005.
In creating the rules for any FF event,
the most important question is how best to
limit performance. The climb phase of the
flight can be limited by reducing power
(e.g., by limiting the displacement of the
engine, the weight of the rubber motor, or
the length and elasticity of the towline) or,
in the case of internal-combustion engines,
by limiting the motor run.
The rate of sink in the glide phase can
be increased by enlarging the wing loading
or total surface loading of the model (as in
F1A, F1B, and F1C) by limiting its
wingspan (as in P-30) or requiring a
minimum aircraft weight. (Model weight
also affects climb; heavier models with the
same power don’t fly as high.)
The new FAI F1Q electric-powered FF event is explained
[[email protected]]
Free Flight Duration Louis Joyner
Charles Groth’s new, smaller model shows the removable cone which contains the
motor, extension shaft, and propeller. Dental bands hold the cone in place.
Charles Groth’s AMA electric-powered Big Red design would be a good starting place for
the new FAI F1Q electric FF event. Drawing by Jim O’Reilly.
The more restrictive the rules are, the
more a premium is placed on model design
and construction and the fewer the
available optimum design choices.
Categories such as F1A Towline, F1B
Wakefield Rubber, and F1C Power, which
have strictly written rules for total surface
area and weight, have each evolved into an
event in which the aircraft are similar in
design and use carbon-fiber composite
construction.
On the other hand, the F1G Coupe rules
specify only rubber motor weight and total
model weight. The result is a much wider
variety of model sizes, design approaches,
and construction methods.
Coupe wings can range from as small as
120 square inches to well in excess of 250
square inches. Construction can be
conventional balsa and tissue, carbon
composite, or almost any combination in
between.
In developing the rules for F1Q, the
decision was to keep things simple. The
battery weight is limited to a maximum of 125 grams for Ni-Cd
and NiMH and a maximum of 90 grams for Li-Ion/Poly batteries.
The maximum motor run is 25 seconds. There are no model area
or weight restrictions. As in F1A, F1B, and F1C, F1Q is flown in
seven rounds with 180-second maxes.
You can find complete rules for the F1Q event on the National
Free Flight Society Web site (http://freeflight.org) or the FAI
Web site (www.fai.org/aeromodelling/documents/sc4.asp).
The two AMA electric events also have simple rules; the only
limitation is on the batteries. A maximum of 1.5 volts per cell is
allowed. Class A models use six cells or less and Class B models
use more than six cells.
With an event such as F1Q in which there are no restrictions
on airplane size or weight, the big question is where to start.
“I’m starting from the electric motor and designing a model
around it,” says Aram Schlosberg. But what motor?
I asked Charles Groth, who is perhaps the most experienced
FF electric modeler in the country, for his suggestions. (His Natswinning
electric-powered Big Red was voted a Model of the Year
and featured in the 2004 NFFS Symposium.) He said:
February 2006 147
Big Red’s RC electric propeller blades are mounted in machined Delrin hub. Rubber
bands hold blades in folded position; centrifugal force opens them when the motor starts.
The Hacker A20 outrunner-style motor mounts to an aluminum
plate at the rear of the balsa cone, providing easy access.
Frank’s model uses a Hyperion Z2213-24 outrunner motor turning
an 11 x 6 folding propeller. Timer mounted below wing controls
auto functions.
Frank Ivers modified a 6-foot-span electric sailplane for FF. It has a
two-piece wing for easy transport. Robert Sisson photo.
The best combination for the serious
beginner at this time is probably different
from my [geared] system because of the
advent of a type of motor we call the
outrunner, which appears to make gears
unnecessary. Both static tests on a
dynamometer and flight tests show great
promise.”
The power package Charles suggests for a
starting point is a Hacker A20 34S motor,
Graupner 8 x 4.5 folding blades, a Phoenix-
10 brushless motor controller, and six SR
Batteries 190 Series Ni-Cd cells. He uses an
electronic timer of his own design for motor
run and dethermalizing. He also machined
the hub for the folding propeller from Delrin.
The total weight of the power package is
just less than 4 ounces. The battery weight is
approximately 60 grams, which is well below
the allowable 125 grams.
The cost breakdown is motor, $60;
battery, $33; controller, $60; and blades,
roughly $9. Charles makes and sells the
electronic timer and propeller hubs. For
information E-mail him at flodyn@
yahoo.com.
What about the model? A good rule of
thumb is that the airframe weight should be
equal to the power-package weight. That
would result in a model that would weigh
approximately the same as an F1B Wakefield
or a 1/2A Gas model with a wing area of 250-
350 square inches.
However, there are a variety of options.
Aram Schlosberg saidNippert modified a gas kit, while Dick Ivers
has bought an RC electric-powered model
and flies it as a Free Flight. Others—Dick
and some Finns—have started from a
Wakefield.
“However, a Wakefield might be underarea
given the battery/controller/motor
weight. My approach was to build something
like a Power model from the 1960s.”
Aram suggests Ernö Frigyes’ Taltos F1C
design, which won the 1963 World
Championships. The 61-inch-span model
uses a modified Benedek B-8353b airfoil.
There are three-view drawings in the 1964-
65 Model Aeronautic Year Book.
Frank Zaic did a detailed analysis of the
model’s climb characteristics in his Circular
Airflow and Model Aircraft. (The Taltos was
one of the first winning deigns to use auto
stabilizer and auto rudder to control the flight
path under power.) The Zaic Year Books are
available from AMA.
Using a larger motor and the maximum
allowable battery weight is basically what
Charles Groth has done with his Natswinning
Big Red. In its six-cell Class A
configuration it meets the 125-gram
maximum battery weight and has an all-up
weight of 18.5 ounces. The wing area is 615
square inches.
The model uses a geared motor to swing
a 16-inch-diameter propeller. A nose
extension prevents a folded blade from
hitting the wing. (Using the higher-torque
outrunner type of motor would eliminate the
need for gears and allow a smaller propeller
and slightly shorter nose. But the geared
motor may have a slight edge in
performance.)
Dick Ivers’ model is an Omega 1.8E Poly
RC electric-powered sailplane from
Northeast Sailplane Products. It spans 72
inches, has a wing area of 455 square inches,
and uses an SD 7036 airfoil. The wingconstruction uses a carbon-fiber D-box.
Power is a Hyperion Z2213-24 brushless
outrunner turning an Aeronaut 11 x 6
propeller with folding blades. The battery is a
Thunder Power ProLite Li-Poly weighing
88.7 grams with connectors. All-up weight is
roughly 19 ounces. To control the power
pattern Dick uses timer-activated auto
stabilizer and auto rudder. He said:
“The stabilizer and rudder move a few
seconds after motor shutdown. The model is
moving too fast to move the auto surfaces
during the motor run.
“These airplanes are closer to F1C or F1J
than to F1B. Of course you could start with a
lighter battery, with less power, and scale
down the model size. I tried the approach of a
Wakefield conversion with only modest
success. The airfoil is wrong for the speed
involved.”
(Wakefield Rubber models typically have
higher-camber wing airfoils than Power
models.)
With the wide variety of design options,
the availability of motors, and the challenge
of breaking new ground, F1Q should be an
exciting event. The reduced noise should
allow models to be flown on some close-in
fields that would not allow gas-powered
models. Get building. MA
Sources:
Hacker motors
www.hackerbrushless.com
SR Batteries batteries
www.srbatteries.com
Castle Creations Phoenix-10 controller
www.castlecreations.com
Omega 1.8E Poly sailplane
Edition: Model Aviation - 2006/02
Page Numbers: 146,147,148,149
146 MODEL AVIATION
ELECTRIC-POWERED FF has been
around for almost 50 years. In the 1959-61
Model Aeronautic Year Book by Frank
Zaic, Fred Militky described his electric
experiments from 1940 to 1959. After
almost 20 years of experimentation he
finally achieved a successful flight with his
Silentius: a 30-inch-span model that
weighed 5 ounces.
If I remember correctly, some variation
of that design was later kitted by Graupner,
for which Fred was the designer. In the
early 1970s Mattel introduced its Super
Star foam RTF electric-powered FF model
that featured programmable flight using
cams.
Although electric power offered a quiet,
easy-starting, no-mess alternative to glowignition
power, it never seemed to catch on
as an event in FF. Batteries were heavy,
and high-revving motors needed gears to be
effective.
The two AMA electric FF events have
been lightly supported, with only a few
modelers, such as Charles Groth, willing to
spend the necessary research time to
develop electric power systems (motor,
gearing, propeller, and battery) and
compatible models.
However, in RC electric has become a
popular power source for models ranging
from park flyers to sailplanes. The strong
interest and large market have made a
variety of electric motors, batteries, and
propellers available at reasonable prices.
Interest in developing an FAI class
began growing a few years ago. The idea
was to create an event that would offer
some of the excitement of F1C without the
noise and the grace of F1B without the cost
of rubber.
The rules were thrashed out informally
via E-mail by a group that included Aram
Schlosberg, Ross Jahnke, Charles Groth,
Dan Tracy, and Tapio Linkosalo. Their
proposal was approved in March 2005.
In creating the rules for any FF event,
the most important question is how best to
limit performance. The climb phase of the
flight can be limited by reducing power
(e.g., by limiting the displacement of the
engine, the weight of the rubber motor, or
the length and elasticity of the towline) or,
in the case of internal-combustion engines,
by limiting the motor run.
The rate of sink in the glide phase can
be increased by enlarging the wing loading
or total surface loading of the model (as in
F1A, F1B, and F1C) by limiting its
wingspan (as in P-30) or requiring a
minimum aircraft weight. (Model weight
also affects climb; heavier models with the
same power don’t fly as high.)
The new FAI F1Q electric-powered FF event is explained
[[email protected]]
Free Flight Duration Louis Joyner
Charles Groth’s new, smaller model shows the removable cone which contains the
motor, extension shaft, and propeller. Dental bands hold the cone in place.
Charles Groth’s AMA electric-powered Big Red design would be a good starting place for
the new FAI F1Q electric FF event. Drawing by Jim O’Reilly.
The more restrictive the rules are, the
more a premium is placed on model design
and construction and the fewer the
available optimum design choices.
Categories such as F1A Towline, F1B
Wakefield Rubber, and F1C Power, which
have strictly written rules for total surface
area and weight, have each evolved into an
event in which the aircraft are similar in
design and use carbon-fiber composite
construction.
On the other hand, the F1G Coupe rules
specify only rubber motor weight and total
model weight. The result is a much wider
variety of model sizes, design approaches,
and construction methods.
Coupe wings can range from as small as
120 square inches to well in excess of 250
square inches. Construction can be
conventional balsa and tissue, carbon
composite, or almost any combination in
between.
In developing the rules for F1Q, the
decision was to keep things simple. The
battery weight is limited to a maximum of 125 grams for Ni-Cd
and NiMH and a maximum of 90 grams for Li-Ion/Poly batteries.
The maximum motor run is 25 seconds. There are no model area
or weight restrictions. As in F1A, F1B, and F1C, F1Q is flown in
seven rounds with 180-second maxes.
You can find complete rules for the F1Q event on the National
Free Flight Society Web site (http://freeflight.org) or the FAI
Web site (www.fai.org/aeromodelling/documents/sc4.asp).
The two AMA electric events also have simple rules; the only
limitation is on the batteries. A maximum of 1.5 volts per cell is
allowed. Class A models use six cells or less and Class B models
use more than six cells.
With an event such as F1Q in which there are no restrictions
on airplane size or weight, the big question is where to start.
“I’m starting from the electric motor and designing a model
around it,” says Aram Schlosberg. But what motor?
I asked Charles Groth, who is perhaps the most experienced
FF electric modeler in the country, for his suggestions. (His Natswinning
electric-powered Big Red was voted a Model of the Year
and featured in the 2004 NFFS Symposium.) He said:
February 2006 147
Big Red’s RC electric propeller blades are mounted in machined Delrin hub. Rubber
bands hold blades in folded position; centrifugal force opens them when the motor starts.
The Hacker A20 outrunner-style motor mounts to an aluminum
plate at the rear of the balsa cone, providing easy access.
Frank’s model uses a Hyperion Z2213-24 outrunner motor turning
an 11 x 6 folding propeller. Timer mounted below wing controls
auto functions.
Frank Ivers modified a 6-foot-span electric sailplane for FF. It has a
two-piece wing for easy transport. Robert Sisson photo.
The best combination for the serious
beginner at this time is probably different
from my [geared] system because of the
advent of a type of motor we call the
outrunner, which appears to make gears
unnecessary. Both static tests on a
dynamometer and flight tests show great
promise.”
The power package Charles suggests for a
starting point is a Hacker A20 34S motor,
Graupner 8 x 4.5 folding blades, a Phoenix-
10 brushless motor controller, and six SR
Batteries 190 Series Ni-Cd cells. He uses an
electronic timer of his own design for motor
run and dethermalizing. He also machined
the hub for the folding propeller from Delrin.
The total weight of the power package is
just less than 4 ounces. The battery weight is
approximately 60 grams, which is well below
the allowable 125 grams.
The cost breakdown is motor, $60;
battery, $33; controller, $60; and blades,
roughly $9. Charles makes and sells the
electronic timer and propeller hubs. For
information E-mail him at flodyn@
yahoo.com.
What about the model? A good rule of
thumb is that the airframe weight should be
equal to the power-package weight. That
would result in a model that would weigh
approximately the same as an F1B Wakefield
or a 1/2A Gas model with a wing area of 250-
350 square inches.
However, there are a variety of options.
Aram Schlosberg saidNippert modified a gas kit, while Dick Ivers
has bought an RC electric-powered model
and flies it as a Free Flight. Others—Dick
and some Finns—have started from a
Wakefield.
“However, a Wakefield might be underarea
given the battery/controller/motor
weight. My approach was to build something
like a Power model from the 1960s.”
Aram suggests Ernö Frigyes’ Taltos F1C
design, which won the 1963 World
Championships. The 61-inch-span model
uses a modified Benedek B-8353b airfoil.
There are three-view drawings in the 1964-
65 Model Aeronautic Year Book.
Frank Zaic did a detailed analysis of the
model’s climb characteristics in his Circular
Airflow and Model Aircraft. (The Taltos was
one of the first winning deigns to use auto
stabilizer and auto rudder to control the flight
path under power.) The Zaic Year Books are
available from AMA.
Using a larger motor and the maximum
allowable battery weight is basically what
Charles Groth has done with his Natswinning
Big Red. In its six-cell Class A
configuration it meets the 125-gram
maximum battery weight and has an all-up
weight of 18.5 ounces. The wing area is 615
square inches.
The model uses a geared motor to swing
a 16-inch-diameter propeller. A nose
extension prevents a folded blade from
hitting the wing. (Using the higher-torque
outrunner type of motor would eliminate the
need for gears and allow a smaller propeller
and slightly shorter nose. But the geared
motor may have a slight edge in
performance.)
Dick Ivers’ model is an Omega 1.8E Poly
RC electric-powered sailplane from
Northeast Sailplane Products. It spans 72
inches, has a wing area of 455 square inches,
and uses an SD 7036 airfoil. The wingconstruction uses a carbon-fiber D-box.
Power is a Hyperion Z2213-24 brushless
outrunner turning an Aeronaut 11 x 6
propeller with folding blades. The battery is a
Thunder Power ProLite Li-Poly weighing
88.7 grams with connectors. All-up weight is
roughly 19 ounces. To control the power
pattern Dick uses timer-activated auto
stabilizer and auto rudder. He said:
“The stabilizer and rudder move a few
seconds after motor shutdown. The model is
moving too fast to move the auto surfaces
during the motor run.
“These airplanes are closer to F1C or F1J
than to F1B. Of course you could start with a
lighter battery, with less power, and scale
down the model size. I tried the approach of a
Wakefield conversion with only modest
success. The airfoil is wrong for the speed
involved.”
(Wakefield Rubber models typically have
higher-camber wing airfoils than Power
models.)
With the wide variety of design options,
the availability of motors, and the challenge
of breaking new ground, F1Q should be an
exciting event. The reduced noise should
allow models to be flown on some close-in
fields that would not allow gas-powered
models. Get building. MA
Sources:
Hacker motors
www.hackerbrushless.com
SR Batteries batteries
www.srbatteries.com
Castle Creations Phoenix-10 controller
www.castlecreations.com
Omega 1.8E Poly sailplane
Edition: Model Aviation - 2006/02
Page Numbers: 146,147,148,149
146 MODEL AVIATION
ELECTRIC-POWERED FF has been
around for almost 50 years. In the 1959-61
Model Aeronautic Year Book by Frank
Zaic, Fred Militky described his electric
experiments from 1940 to 1959. After
almost 20 years of experimentation he
finally achieved a successful flight with his
Silentius: a 30-inch-span model that
weighed 5 ounces.
If I remember correctly, some variation
of that design was later kitted by Graupner,
for which Fred was the designer. In the
early 1970s Mattel introduced its Super
Star foam RTF electric-powered FF model
that featured programmable flight using
cams.
Although electric power offered a quiet,
easy-starting, no-mess alternative to glowignition
power, it never seemed to catch on
as an event in FF. Batteries were heavy,
and high-revving motors needed gears to be
effective.
The two AMA electric FF events have
been lightly supported, with only a few
modelers, such as Charles Groth, willing to
spend the necessary research time to
develop electric power systems (motor,
gearing, propeller, and battery) and
compatible models.
However, in RC electric has become a
popular power source for models ranging
from park flyers to sailplanes. The strong
interest and large market have made a
variety of electric motors, batteries, and
propellers available at reasonable prices.
Interest in developing an FAI class
began growing a few years ago. The idea
was to create an event that would offer
some of the excitement of F1C without the
noise and the grace of F1B without the cost
of rubber.
The rules were thrashed out informally
via E-mail by a group that included Aram
Schlosberg, Ross Jahnke, Charles Groth,
Dan Tracy, and Tapio Linkosalo. Their
proposal was approved in March 2005.
In creating the rules for any FF event,
the most important question is how best to
limit performance. The climb phase of the
flight can be limited by reducing power
(e.g., by limiting the displacement of the
engine, the weight of the rubber motor, or
the length and elasticity of the towline) or,
in the case of internal-combustion engines,
by limiting the motor run.
The rate of sink in the glide phase can
be increased by enlarging the wing loading
or total surface loading of the model (as in
F1A, F1B, and F1C) by limiting its
wingspan (as in P-30) or requiring a
minimum aircraft weight. (Model weight
also affects climb; heavier models with the
same power don’t fly as high.)
The new FAI F1Q electric-powered FF event is explained
[[email protected]]
Free Flight Duration Louis Joyner
Charles Groth’s new, smaller model shows the removable cone which contains the
motor, extension shaft, and propeller. Dental bands hold the cone in place.
Charles Groth’s AMA electric-powered Big Red design would be a good starting place for
the new FAI F1Q electric FF event. Drawing by Jim O’Reilly.
The more restrictive the rules are, the
more a premium is placed on model design
and construction and the fewer the
available optimum design choices.
Categories such as F1A Towline, F1B
Wakefield Rubber, and F1C Power, which
have strictly written rules for total surface
area and weight, have each evolved into an
event in which the aircraft are similar in
design and use carbon-fiber composite
construction.
On the other hand, the F1G Coupe rules
specify only rubber motor weight and total
model weight. The result is a much wider
variety of model sizes, design approaches,
and construction methods.
Coupe wings can range from as small as
120 square inches to well in excess of 250
square inches. Construction can be
conventional balsa and tissue, carbon
composite, or almost any combination in
between.
In developing the rules for F1Q, the
decision was to keep things simple. The
battery weight is limited to a maximum of 125 grams for Ni-Cd
and NiMH and a maximum of 90 grams for Li-Ion/Poly batteries.
The maximum motor run is 25 seconds. There are no model area
or weight restrictions. As in F1A, F1B, and F1C, F1Q is flown in
seven rounds with 180-second maxes.
You can find complete rules for the F1Q event on the National
Free Flight Society Web site (http://freeflight.org) or the FAI
Web site (www.fai.org/aeromodelling/documents/sc4.asp).
The two AMA electric events also have simple rules; the only
limitation is on the batteries. A maximum of 1.5 volts per cell is
allowed. Class A models use six cells or less and Class B models
use more than six cells.
With an event such as F1Q in which there are no restrictions
on airplane size or weight, the big question is where to start.
“I’m starting from the electric motor and designing a model
around it,” says Aram Schlosberg. But what motor?
I asked Charles Groth, who is perhaps the most experienced
FF electric modeler in the country, for his suggestions. (His Natswinning
electric-powered Big Red was voted a Model of the Year
and featured in the 2004 NFFS Symposium.) He said:
February 2006 147
Big Red’s RC electric propeller blades are mounted in machined Delrin hub. Rubber
bands hold blades in folded position; centrifugal force opens them when the motor starts.
The Hacker A20 outrunner-style motor mounts to an aluminum
plate at the rear of the balsa cone, providing easy access.
Frank’s model uses a Hyperion Z2213-24 outrunner motor turning
an 11 x 6 folding propeller. Timer mounted below wing controls
auto functions.
Frank Ivers modified a 6-foot-span electric sailplane for FF. It has a
two-piece wing for easy transport. Robert Sisson photo.
The best combination for the serious
beginner at this time is probably different
from my [geared] system because of the
advent of a type of motor we call the
outrunner, which appears to make gears
unnecessary. Both static tests on a
dynamometer and flight tests show great
promise.”
The power package Charles suggests for a
starting point is a Hacker A20 34S motor,
Graupner 8 x 4.5 folding blades, a Phoenix-
10 brushless motor controller, and six SR
Batteries 190 Series Ni-Cd cells. He uses an
electronic timer of his own design for motor
run and dethermalizing. He also machined
the hub for the folding propeller from Delrin.
The total weight of the power package is
just less than 4 ounces. The battery weight is
approximately 60 grams, which is well below
the allowable 125 grams.
The cost breakdown is motor, $60;
battery, $33; controller, $60; and blades,
roughly $9. Charles makes and sells the
electronic timer and propeller hubs. For
information E-mail him at flodyn@
yahoo.com.
What about the model? A good rule of
thumb is that the airframe weight should be
equal to the power-package weight. That
would result in a model that would weigh
approximately the same as an F1B Wakefield
or a 1/2A Gas model with a wing area of 250-
350 square inches.
However, there are a variety of options.
Aram Schlosberg saidNippert modified a gas kit, while Dick Ivers
has bought an RC electric-powered model
and flies it as a Free Flight. Others—Dick
and some Finns—have started from a
Wakefield.
“However, a Wakefield might be underarea
given the battery/controller/motor
weight. My approach was to build something
like a Power model from the 1960s.”
Aram suggests Ernö Frigyes’ Taltos F1C
design, which won the 1963 World
Championships. The 61-inch-span model
uses a modified Benedek B-8353b airfoil.
There are three-view drawings in the 1964-
65 Model Aeronautic Year Book.
Frank Zaic did a detailed analysis of the
model’s climb characteristics in his Circular
Airflow and Model Aircraft. (The Taltos was
one of the first winning deigns to use auto
stabilizer and auto rudder to control the flight
path under power.) The Zaic Year Books are
available from AMA.
Using a larger motor and the maximum
allowable battery weight is basically what
Charles Groth has done with his Natswinning
Big Red. In its six-cell Class A
configuration it meets the 125-gram
maximum battery weight and has an all-up
weight of 18.5 ounces. The wing area is 615
square inches.
The model uses a geared motor to swing
a 16-inch-diameter propeller. A nose
extension prevents a folded blade from
hitting the wing. (Using the higher-torque
outrunner type of motor would eliminate the
need for gears and allow a smaller propeller
and slightly shorter nose. But the geared
motor may have a slight edge in
performance.)
Dick Ivers’ model is an Omega 1.8E Poly
RC electric-powered sailplane from
Northeast Sailplane Products. It spans 72
inches, has a wing area of 455 square inches,
and uses an SD 7036 airfoil. The wingconstruction uses a carbon-fiber D-box.
Power is a Hyperion Z2213-24 brushless
outrunner turning an Aeronaut 11 x 6
propeller with folding blades. The battery is a
Thunder Power ProLite Li-Poly weighing
88.7 grams with connectors. All-up weight is
roughly 19 ounces. To control the power
pattern Dick uses timer-activated auto
stabilizer and auto rudder. He said:
“The stabilizer and rudder move a few
seconds after motor shutdown. The model is
moving too fast to move the auto surfaces
during the motor run.
“These airplanes are closer to F1C or F1J
than to F1B. Of course you could start with a
lighter battery, with less power, and scale
down the model size. I tried the approach of a
Wakefield conversion with only modest
success. The airfoil is wrong for the speed
involved.”
(Wakefield Rubber models typically have
higher-camber wing airfoils than Power
models.)
With the wide variety of design options,
the availability of motors, and the challenge
of breaking new ground, F1Q should be an
exciting event. The reduced noise should
allow models to be flown on some close-in
fields that would not allow gas-powered
models. Get building. MA
Sources:
Hacker motors
www.hackerbrushless.com
SR Batteries batteries
www.srbatteries.com
Castle Creations Phoenix-10 controller
www.castlecreations.com
Omega 1.8E Poly sailplane