July 2008 149
AS I OUTLINED in the April column, the
2008 CL Navy Carrier Nats will be flown
during three days. The schedule is as
follows.
• Wednesday July 16: AMA Profile Carrier,
Navy Carrier Society (NCS) Sportsman
Profile Carrier
• Thursday July 17: AMA Class I, Class II
Navy Carrier
• Friday July 18: .15 Carrier (glow and
electric combined), Sig Skyray Carrier
(glow and electric combined), Nostalgia
Carrier (Profile, Class I, Class II), Electric
Carrier (Profile, Class I, Class II)
Sponsorship for the unofficial events is
provided by the NCS, the North Coast
Control Line Club
of Cleveland, Sig
Manufacturing
Company, and some
of your fellow
Carrier modelers.
Peter Mazur is
seeking sponsors for
the electric-power
Schedule for Carrier action at the upcoming AMA Nats
[[email protected]]
Control Line Navy Carrier Dick Perry
The eLogger can provide data for analyzing
electric-flight performance. It is small, light
(roughly 1 x 2 inches), and can fit
conveniently into most models.
Pete Mazur’s electric Skyray installation puts all the electronics and wiring inside the wing.
Openings at the LE and TE provide cooling airflow.
Also included in this column:
• Electric power for Carrier
• A new model by Gary Hull
Gary Hull’s Short Seamew during
construction last winter. It should
have competed by the time you
read this.
Li-Poly Battery
Data Logger
ESC
Arming Plug
events, and I’ll announce that information in
the next column as well as in the Nats
reporting. Ted Kraver has volunteered to
serve as our event director for the official
flying days.
There is still quite a bit of experimentation
going on in the electric-powered Carrier
events. I hope to have more information to
report following the Nats about exactly what
type of equipment is being used, battery
voltages and capacities, motor specifications,
ESC current capacities, and any other bits of
useful information to help us settle in on
workable equipment combinations.
Pete Mazur has used electronic datalogging
capabilities, and I have also acquired
the appropriate equipment. We are using the
eLogger from Eagle Tree Systems.
This device provides time-based recording
capability for voltage and current in its basic
form. Additional data recording is available
through plug-in modules for temperature,
rpm, servo data, altitude, and airspeed.
The eLogger can provide real-time
readouts to a computer during ground-testing
or recorded data following a flight. The
computer program calculates power and
battery capacity used, and it displays the
recorded data channels.
One of the first questions someone who is
planning for any electric Carrier events asks
involves the power needed for adequate
performance. The majority of
experimentation is in Skyray and .15 Carrier.
Because those are speed-limit events, power
requirements are arbitrarily limited along with
the speed. The difference between a 70 or 75
mph model’s power requirements and those
of a model flying at 95 mph are considerably
greater than many would think.
The power a model requires is determined
by multiplying drag and speed. Since drag is
already dependent on speed and varies with
the square of the speed (all else remaining
constant), the power required increases as a
cube function of speed, rising dramatically as
speed increases.
If one starts with the power required to fly
at 75 mph and wants to increase speed to 95
mph, one would need to provide more than
twice the power to gain the additional 20
mph. Adding 30 mph requires nearly three
times the power.
Pete Mazur’s electric-powered Skyray
requires approximately 750-800 watts of
input power to achieve a 75 mph high-speed
score. For comparison purposes, 1
horsepower is equal to approximately 750
watts.
Pete is currently flying with a 4S Li-Poly
battery pack with a nominal voltage of 14.4
and a capacity of 3300 mAh. Smaller
batteries did not have the capacity to last
through a good low speed.
The specifications for most motors include
limits on continuous and short-duration power
or current. Battery packs are typically rated
for maximum continuous current and usually
specify peak current for a limited period of
time.
This is all convenient for sizing equipment
if an estimated power requirement is known,
because the physicists have conveniently
defined power in electrical applications as the
product of current in amperes and voltage.
There are numerous losses and inefficiencies
between the battery and the propeller, but it
suffices to use input power (battery voltage
multiplied by current) as the equivalent of
total system power.
Internal-combustion engines vary in
torque throughout each revolution. The power
stroke lasts for less than one-third of each
revolution, followed by a period of coasting
during the intake/exhaust period and then a
deceleration of the propeller during
compression.
Because the nearly constant torque a
motor applies is considerably smoother than
the cyclic power variation of a two-stroke
engine, electric propellers can be thinner and
lighter than glow propellers. Electrics can
certainly use glow propellers, and glow
propellers may provide a wider range of
performance to tune power output for
optimum performance.
As with our internal-combustion engines,
there are electric propellers designed for
either direction of rotation. Reverse-rotation
(pusher) propellers come in a much smaller
selection of diameters, pitches, and blade
areas—either glow or electric.
Some Carrier modelers greatly prefer a
pusher propeller and reverse-rotation engines.
With glow power, the handling advantages
are small and the choice is largely a matter of
personal preference and availability of more
options for performance tuning with
conventional rotation.
Power input to the propeller is a product
of torque and rotational speed. High-revving,
low-torque glow engines can’t have too much
of an adverse effect on a properly trimmed
model in slow flight.
Motors, especially outrunners, produce
considerably more torque at a lower rpm for a
given power output. The high torque can roll
a model toward the center of the circle quite
easily, making reverse (left-hand) rotation all
but essential for outrunners or geared motors.
The good part of all this is that brushless
motors can run in either direction by
reversing two of the three input wires.
I’ve received little information on new
models that were built during the winter.
Gary Hull sent me a photo of his new
Short Seamew for Profile Carrier, which will
be flying as you read this. He stretched the
fuselage and wing chord, but the Seamew still
looks close to scale, and there is no question
at all what it is. I’m looking forward to seeing
it fly.
I’d like to see what you are flying this
summer. You can send photos for publication
to the address in the column heading. MA
Sources:
Eagle Tree Systems
(425) 614-0450
www.eagletreesystems.com
Edition: Model Aviation - 2008/07
Page Numbers: 149,150
Edition: Model Aviation - 2008/07
Page Numbers: 149,150
July 2008 149
AS I OUTLINED in the April column, the
2008 CL Navy Carrier Nats will be flown
during three days. The schedule is as
follows.
• Wednesday July 16: AMA Profile Carrier,
Navy Carrier Society (NCS) Sportsman
Profile Carrier
• Thursday July 17: AMA Class I, Class II
Navy Carrier
• Friday July 18: .15 Carrier (glow and
electric combined), Sig Skyray Carrier
(glow and electric combined), Nostalgia
Carrier (Profile, Class I, Class II), Electric
Carrier (Profile, Class I, Class II)
Sponsorship for the unofficial events is
provided by the NCS, the North Coast
Control Line Club
of Cleveland, Sig
Manufacturing
Company, and some
of your fellow
Carrier modelers.
Peter Mazur is
seeking sponsors for
the electric-power
Schedule for Carrier action at the upcoming AMA Nats
[[email protected]]
Control Line Navy Carrier Dick Perry
The eLogger can provide data for analyzing
electric-flight performance. It is small, light
(roughly 1 x 2 inches), and can fit
conveniently into most models.
Pete Mazur’s electric Skyray installation puts all the electronics and wiring inside the wing.
Openings at the LE and TE provide cooling airflow.
Also included in this column:
• Electric power for Carrier
• A new model by Gary Hull
Gary Hull’s Short Seamew during
construction last winter. It should
have competed by the time you
read this.
Li-Poly Battery
Data Logger
ESC
Arming Plug
events, and I’ll announce that information in
the next column as well as in the Nats
reporting. Ted Kraver has volunteered to
serve as our event director for the official
flying days.
There is still quite a bit of experimentation
going on in the electric-powered Carrier
events. I hope to have more information to
report following the Nats about exactly what
type of equipment is being used, battery
voltages and capacities, motor specifications,
ESC current capacities, and any other bits of
useful information to help us settle in on
workable equipment combinations.
Pete Mazur has used electronic datalogging
capabilities, and I have also acquired
the appropriate equipment. We are using the
eLogger from Eagle Tree Systems.
This device provides time-based recording
capability for voltage and current in its basic
form. Additional data recording is available
through plug-in modules for temperature,
rpm, servo data, altitude, and airspeed.
The eLogger can provide real-time
readouts to a computer during ground-testing
or recorded data following a flight. The
computer program calculates power and
battery capacity used, and it displays the
recorded data channels.
One of the first questions someone who is
planning for any electric Carrier events asks
involves the power needed for adequate
performance. The majority of
experimentation is in Skyray and .15 Carrier.
Because those are speed-limit events, power
requirements are arbitrarily limited along with
the speed. The difference between a 70 or 75
mph model’s power requirements and those
of a model flying at 95 mph are considerably
greater than many would think.
The power a model requires is determined
by multiplying drag and speed. Since drag is
already dependent on speed and varies with
the square of the speed (all else remaining
constant), the power required increases as a
cube function of speed, rising dramatically as
speed increases.
If one starts with the power required to fly
at 75 mph and wants to increase speed to 95
mph, one would need to provide more than
twice the power to gain the additional 20
mph. Adding 30 mph requires nearly three
times the power.
Pete Mazur’s electric-powered Skyray
requires approximately 750-800 watts of
input power to achieve a 75 mph high-speed
score. For comparison purposes, 1
horsepower is equal to approximately 750
watts.
Pete is currently flying with a 4S Li-Poly
battery pack with a nominal voltage of 14.4
and a capacity of 3300 mAh. Smaller
batteries did not have the capacity to last
through a good low speed.
The specifications for most motors include
limits on continuous and short-duration power
or current. Battery packs are typically rated
for maximum continuous current and usually
specify peak current for a limited period of
time.
This is all convenient for sizing equipment
if an estimated power requirement is known,
because the physicists have conveniently
defined power in electrical applications as the
product of current in amperes and voltage.
There are numerous losses and inefficiencies
between the battery and the propeller, but it
suffices to use input power (battery voltage
multiplied by current) as the equivalent of
total system power.
Internal-combustion engines vary in
torque throughout each revolution. The power
stroke lasts for less than one-third of each
revolution, followed by a period of coasting
during the intake/exhaust period and then a
deceleration of the propeller during
compression.
Because the nearly constant torque a
motor applies is considerably smoother than
the cyclic power variation of a two-stroke
engine, electric propellers can be thinner and
lighter than glow propellers. Electrics can
certainly use glow propellers, and glow
propellers may provide a wider range of
performance to tune power output for
optimum performance.
As with our internal-combustion engines,
there are electric propellers designed for
either direction of rotation. Reverse-rotation
(pusher) propellers come in a much smaller
selection of diameters, pitches, and blade
areas—either glow or electric.
Some Carrier modelers greatly prefer a
pusher propeller and reverse-rotation engines.
With glow power, the handling advantages
are small and the choice is largely a matter of
personal preference and availability of more
options for performance tuning with
conventional rotation.
Power input to the propeller is a product
of torque and rotational speed. High-revving,
low-torque glow engines can’t have too much
of an adverse effect on a properly trimmed
model in slow flight.
Motors, especially outrunners, produce
considerably more torque at a lower rpm for a
given power output. The high torque can roll
a model toward the center of the circle quite
easily, making reverse (left-hand) rotation all
but essential for outrunners or geared motors.
The good part of all this is that brushless
motors can run in either direction by
reversing two of the three input wires.
I’ve received little information on new
models that were built during the winter.
Gary Hull sent me a photo of his new
Short Seamew for Profile Carrier, which will
be flying as you read this. He stretched the
fuselage and wing chord, but the Seamew still
looks close to scale, and there is no question
at all what it is. I’m looking forward to seeing
it fly.
I’d like to see what you are flying this
summer. You can send photos for publication
to the address in the column heading. MA
Sources:
Eagle Tree Systems
(425) 614-0450
www.eagletreesystems.com