IT’S HARD TO think of Christmas when it’s the end of August
and the temps here in North Carolina have been hovering in the
high 90s or at 100° for the last couple weeks. Then again, it’s
refreshing to think that it will be much cooler by the time you read
this.
I hope everyone has a great holiday season and that the new
year brings you all the toys that make life so much fun. Thanks for
your support this year; I hope we have another great one.
Farewell to a Friend: Awhile back I
mentioned working on an Approach
Engineering Cobra conversion kit for my
Swift helicopter. James Linder founded
Approach Engineering in Utah, and I’m
extremely sad to report that he was killed in
August in an Apache crash.
James was a full-time instructor pilot for
the Utah National Guard and, more
importantly, a loving husband, father, and
good friend to many people. He and I were
collaborating on adapting his new Apache kit
to fit the Quick QJ-10 airframe I had just sent
him. He was a talented designer and an
incredibly smart engineer by trade.
I’m at a loss for how to express my
feelings to his family and the rest of his
friends. I hope someone will buy his kit line
and continue it, but there is no way to make
up for the loss of James and his friendship.
On the Soapbox: I want to remind everyone
about the purpose of the last few “Electrics”
columns and the lessons within. They were
intended to be guidelines showing how to
plan a power system.
A farewell to James Linder
December 2007 123
Electrics Greg Gimlick | [email protected]
Also included in this column:
• A look at electric airplane
performance-simulation
programs
• Li-Poly discharging clarification
James Linder with his partially framed-up electric-powered
Cobra in front of the beautiful Utah countryside.
An Approach Engineering Cobra fitted to a Quick EP-8. The Approach
kits are of all-built-up construction and perfectly engineered. The
company’s future is in limbo since James Linder’s premature death.
Greg’s newest data-acquisition system is the Seagull unit. It is the best affordable system he
has found. Wireless transmission sends data to a module mounted on a radio, in real time.
124 MODEL AVIATION
Below: MotoCalc generates this report
with all the parameters charted at
various airspeeds and full throttle. If this
is confusing, choose “Opinion” for a
written explanation.
Bottom: You’ll get to MotoCalc’s main
window when you complete the
MotoWizard. From here you can
generate the report and see the
equipment for your setup.
Left: The MotoWizard window is the
place to start if you’re learning
MotoCalc. It will take you through the
setup step by step.
I’ve taken some heat for the August issue, in which I showed
how to figure out amp minutes and divide by current, etc. to make
decisions regarding duration. Some readers took me to task for
planning on discharging Li-Poly batteries to their full capacity.
Those were exercises to show you how to do the calculations
without regard to efficiency, battery type, etc. I thought I made that
clear, but apparently not. I am not advocating complete discharge.
It’s all relative in planning, though; if you get more duration
from one setup than another, it will still be so when you figure in
efficiency or reduce the discharge to 70% of capacity. The purpose
is to understand the steps involved.
Electric Airplane Performance-Simulation Programs: One thing is
without question in my mind: owning one of the simulation
programs will save you more money than it costs in the long run and
teach you more than you will learn in hours surfing the Internet.
Are they perfect? No, but they are a lot more accurate than you
will be with your pencil, paper, and calculator. These programs
contain databases and algorithms to consider all the parameters and
can be updated with ease.
I believe that the top two programs are ElectriCalc and MotoCalc.
I’m going to touch on each of them briefly this month and next, but I
won’t pretend to do them justice since that would require a full feature
article for each.
MotoCalc (Mcalc) is the brainchild of
Stefan Vorkoetter of Capable Computing, Inc.
He has been around the electric-flight world
for a long time and can be found on many
RCGroups forums.
Right off the bat you’ll appreciate the Web
support the company provides for this
simulation. You can download a full-featured
version for a trial period before you buy it, so
there’s no risk.
MotoCalc has often been described as
difficult to learn, and it probably does have a
slightly steeper learning curve than ElectriCalc
for a beginner. Don’t let that influence your
decision, though, until you’ve gone through
the tutorials, both online and off.
The tutorials will carry you step by step
through the whole planning process. Most
questions I’ve gotten about MotoCalc through
the years could have been answered had the
user taken some time to read the manual or try
the tutorials. They will teach you more than
any book on the market.
When you open the program you’re
greeted with a “tip window”; it’s wise to keep
that activated while you learn your way. The
next screen is the MotoWizard, which will
walk you through each step of a model from
start to finish.
I plugged in a Sig LT-25 and made choices
along the way as it worked across the screen.
Following are the steps and selections I
entered.
• Performance: Sport
• Model: Wingspan, area, and weight without
motor, battery, and ESC
• Airfoil type: Basic info such as flatbottomed,
semi-symmetrical, etc.
• Thickness: You are given diagrams and you
pick thin, fat, etc.
• Field: Elevation; I left it at sea level.
• Motor: Your choice; brushless, brushed,
either. I chose brushless.
• Gear & Prop: I chose direct or geared and a
maximum propeller size of 14 x 10.
• Battery: You can choose “any” and let it
pick, but I selected A123 cells in a six-cell
pack.
• Results: You will be given a list of motors to
select from with ratings to let you know
Mcalc’s best choice. I chose the
recommendation of a Neu 2215/1.5Y.
When you complete these steps and hit
“Accept,” the program will take you to the
main window. From there you can select
“Compute Report” and you’ll be presented
with a window full of information.
This is where many people get confused
and discouraged, but there is a not-so-hidden
gem you’ll learn to love: the “Opinion” button.
When you hit this you’re presented with an
easy-to-read opinion of your setup. Following
was my result.
“MotOpinion—Sig LT-25
“Sea Level, 29.92inHg, 59°F
“Motor: Neu 2215/1.5Y BAM; 1020rpm/V;
1.6A no-load; 0.004 Ohms.
“Battery: A123 ANR26650 M1 (30C); 6 cells;
2300mAh @ 3.3V; 0.016 Ohms/cell.
“Speed Control: Castle Creations Phoenix 60;
0.0012 Ohms; High rate.
“Drive System: Generic 14x9in Prop w/2.5:1
Gearbox; 14x9 (Pconst=1.17; Tconst=1)
geared 2.5:1 (Eff=92%).
“Airframe: Sig LT-25; 724sq.in; 104.8oz
RTF; 20.8oz/sq.ft; Cd=0.059; Cl=0.6;
Clopt=0.67; Clmax=1.24.
“Stats: 83 W/lb in; 72 W/lb out; 21mph stall;
29mph opt @ 57% (32:06, 66°F); 30mph level
@ 59% (31:10, 66°F); 1450ft/min @ 35.1°; -
244ft/min @ -5.5°.
“Possible Power System Problems:
“• The full-throttle motor current at the
best lift-to-drag ratio airspeed (31.6A) is
lower than the motor’s maximum efficiency
current (81.8A). A higher current level
would improve system efficiency.
“• Current can be increased by using more
cells, a larger diameter or higher pitched
propeller, a lower gear ratio, or some
combination of these methods.
“Power System Notes:
“• The voltage (16.6V) exceeds 12V. Be
sure the speed control is rated for at least
the number of cells specified above.
“Aerodynamic Notes:
“• The static pitch speed (57mph) is within the
range of approximately 2.5 to 3 times the
model’s stall speed (21mph), which is
considered ideal for good performance.
“• With a wing loading of 20.8oz/sq.ft, a model
of this size will have trainer-like flying
characteristics. It would make an ideal
trainer, for use in calm to light wind
conditions.
“• The static thrust (94.7oz) to weight
(104.8oz) ratio is 0.9:1, which will result in
very short take-off runs, no difficulty taking off
from grass surfaces (assuming sufficiently
large wheels), and steep climb-outs.
“• At the best lift-to-drag ratio airspeed, the
excess-thrust (58.6oz) to weight (104.8oz)
ratio is 0.56:1, which will give steep climbs
and excellent acceleration. This model should
be able to do consecutive loops, and has
sufficient in-flight thrust for almost any
aerobatic maneuver.
“General Notes:
“• This analysis is based on calculations that
take motor heating effects into account.
“• These calculations are based on
mathematical models that may not account for
all limitations of the components used. Always
consult the power system component
manufacturers to ensure that no limits
(current, rpm, etc.) are being exceeded.”
This should be enough to get you over the
initial hump of looking at the opening screens
and wondering what to do next. From this
point you can tweak the setups by changing all
the parameters as much as you please. You
can set up filters to assess only propellers
within a certain range or gear ratios, etc. It’s
extremely versatile.
You can hit the “Opinion” button anytime
you don’t fully understand the results, and it
will spit out a report, as shown, along with
recommendations.
I’ve mentioned before that data-gathering
tools are essential if you want to get into
tweaking and experimenting with electrics.
I’ve been using the Micro Power from Eagle
Tree Systems, and it does everything most
modelers will want to do.
I recently obtained the Seagull system from
Eagle Tree, complete with wireless data
transfer. This is the pro-level unit, and now I
can monitor the two motors I have ganged to
an Inner Demon Gearbox in my giant-scale
Pitts. A full article about this incredible system
is to come!
I hate that space has run out. Next time I will
look at ElectriCalc and how to get going with
it. Again, all electric-power fliers should own
at least one of these programs, especially as
they’re learning. If you don’t want to play
engineer, you don’t have to; just copy
someone else and have fun at the field. MA
Sources:
MotoCalc
(519) 638-5470
www.motocalc.com
Edition: Model Aviation - 2007/12
Page Numbers: 123,124,125
Edition: Model Aviation - 2007/12
Page Numbers: 123,124,125
IT’S HARD TO think of Christmas when it’s the end of August
and the temps here in North Carolina have been hovering in the
high 90s or at 100° for the last couple weeks. Then again, it’s
refreshing to think that it will be much cooler by the time you read
this.
I hope everyone has a great holiday season and that the new
year brings you all the toys that make life so much fun. Thanks for
your support this year; I hope we have another great one.
Farewell to a Friend: Awhile back I
mentioned working on an Approach
Engineering Cobra conversion kit for my
Swift helicopter. James Linder founded
Approach Engineering in Utah, and I’m
extremely sad to report that he was killed in
August in an Apache crash.
James was a full-time instructor pilot for
the Utah National Guard and, more
importantly, a loving husband, father, and
good friend to many people. He and I were
collaborating on adapting his new Apache kit
to fit the Quick QJ-10 airframe I had just sent
him. He was a talented designer and an
incredibly smart engineer by trade.
I’m at a loss for how to express my
feelings to his family and the rest of his
friends. I hope someone will buy his kit line
and continue it, but there is no way to make
up for the loss of James and his friendship.
On the Soapbox: I want to remind everyone
about the purpose of the last few “Electrics”
columns and the lessons within. They were
intended to be guidelines showing how to
plan a power system.
A farewell to James Linder
December 2007 123
Electrics Greg Gimlick | [email protected]
Also included in this column:
• A look at electric airplane
performance-simulation
programs
• Li-Poly discharging clarification
James Linder with his partially framed-up electric-powered
Cobra in front of the beautiful Utah countryside.
An Approach Engineering Cobra fitted to a Quick EP-8. The Approach
kits are of all-built-up construction and perfectly engineered. The
company’s future is in limbo since James Linder’s premature death.
Greg’s newest data-acquisition system is the Seagull unit. It is the best affordable system he
has found. Wireless transmission sends data to a module mounted on a radio, in real time.
124 MODEL AVIATION
Below: MotoCalc generates this report
with all the parameters charted at
various airspeeds and full throttle. If this
is confusing, choose “Opinion” for a
written explanation.
Bottom: You’ll get to MotoCalc’s main
window when you complete the
MotoWizard. From here you can
generate the report and see the
equipment for your setup.
Left: The MotoWizard window is the
place to start if you’re learning
MotoCalc. It will take you through the
setup step by step.
I’ve taken some heat for the August issue, in which I showed
how to figure out amp minutes and divide by current, etc. to make
decisions regarding duration. Some readers took me to task for
planning on discharging Li-Poly batteries to their full capacity.
Those were exercises to show you how to do the calculations
without regard to efficiency, battery type, etc. I thought I made that
clear, but apparently not. I am not advocating complete discharge.
It’s all relative in planning, though; if you get more duration
from one setup than another, it will still be so when you figure in
efficiency or reduce the discharge to 70% of capacity. The purpose
is to understand the steps involved.
Electric Airplane Performance-Simulation Programs: One thing is
without question in my mind: owning one of the simulation
programs will save you more money than it costs in the long run and
teach you more than you will learn in hours surfing the Internet.
Are they perfect? No, but they are a lot more accurate than you
will be with your pencil, paper, and calculator. These programs
contain databases and algorithms to consider all the parameters and
can be updated with ease.
I believe that the top two programs are ElectriCalc and MotoCalc.
I’m going to touch on each of them briefly this month and next, but I
won’t pretend to do them justice since that would require a full feature
article for each.
MotoCalc (Mcalc) is the brainchild of
Stefan Vorkoetter of Capable Computing, Inc.
He has been around the electric-flight world
for a long time and can be found on many
RCGroups forums.
Right off the bat you’ll appreciate the Web
support the company provides for this
simulation. You can download a full-featured
version for a trial period before you buy it, so
there’s no risk.
MotoCalc has often been described as
difficult to learn, and it probably does have a
slightly steeper learning curve than ElectriCalc
for a beginner. Don’t let that influence your
decision, though, until you’ve gone through
the tutorials, both online and off.
The tutorials will carry you step by step
through the whole planning process. Most
questions I’ve gotten about MotoCalc through
the years could have been answered had the
user taken some time to read the manual or try
the tutorials. They will teach you more than
any book on the market.
When you open the program you’re
greeted with a “tip window”; it’s wise to keep
that activated while you learn your way. The
next screen is the MotoWizard, which will
walk you through each step of a model from
start to finish.
I plugged in a Sig LT-25 and made choices
along the way as it worked across the screen.
Following are the steps and selections I
entered.
• Performance: Sport
• Model: Wingspan, area, and weight without
motor, battery, and ESC
• Airfoil type: Basic info such as flatbottomed,
semi-symmetrical, etc.
• Thickness: You are given diagrams and you
pick thin, fat, etc.
• Field: Elevation; I left it at sea level.
• Motor: Your choice; brushless, brushed,
either. I chose brushless.
• Gear & Prop: I chose direct or geared and a
maximum propeller size of 14 x 10.
• Battery: You can choose “any” and let it
pick, but I selected A123 cells in a six-cell
pack.
• Results: You will be given a list of motors to
select from with ratings to let you know
Mcalc’s best choice. I chose the
recommendation of a Neu 2215/1.5Y.
When you complete these steps and hit
“Accept,” the program will take you to the
main window. From there you can select
“Compute Report” and you’ll be presented
with a window full of information.
This is where many people get confused
and discouraged, but there is a not-so-hidden
gem you’ll learn to love: the “Opinion” button.
When you hit this you’re presented with an
easy-to-read opinion of your setup. Following
was my result.
“MotOpinion—Sig LT-25
“Sea Level, 29.92inHg, 59°F
“Motor: Neu 2215/1.5Y BAM; 1020rpm/V;
1.6A no-load; 0.004 Ohms.
“Battery: A123 ANR26650 M1 (30C); 6 cells;
2300mAh @ 3.3V; 0.016 Ohms/cell.
“Speed Control: Castle Creations Phoenix 60;
0.0012 Ohms; High rate.
“Drive System: Generic 14x9in Prop w/2.5:1
Gearbox; 14x9 (Pconst=1.17; Tconst=1)
geared 2.5:1 (Eff=92%).
“Airframe: Sig LT-25; 724sq.in; 104.8oz
RTF; 20.8oz/sq.ft; Cd=0.059; Cl=0.6;
Clopt=0.67; Clmax=1.24.
“Stats: 83 W/lb in; 72 W/lb out; 21mph stall;
29mph opt @ 57% (32:06, 66°F); 30mph level
@ 59% (31:10, 66°F); 1450ft/min @ 35.1°; -
244ft/min @ -5.5°.
“Possible Power System Problems:
“• The full-throttle motor current at the
best lift-to-drag ratio airspeed (31.6A) is
lower than the motor’s maximum efficiency
current (81.8A). A higher current level
would improve system efficiency.
“• Current can be increased by using more
cells, a larger diameter or higher pitched
propeller, a lower gear ratio, or some
combination of these methods.
“Power System Notes:
“• The voltage (16.6V) exceeds 12V. Be
sure the speed control is rated for at least
the number of cells specified above.
“Aerodynamic Notes:
“• The static pitch speed (57mph) is within the
range of approximately 2.5 to 3 times the
model’s stall speed (21mph), which is
considered ideal for good performance.
“• With a wing loading of 20.8oz/sq.ft, a model
of this size will have trainer-like flying
characteristics. It would make an ideal
trainer, for use in calm to light wind
conditions.
“• The static thrust (94.7oz) to weight
(104.8oz) ratio is 0.9:1, which will result in
very short take-off runs, no difficulty taking off
from grass surfaces (assuming sufficiently
large wheels), and steep climb-outs.
“• At the best lift-to-drag ratio airspeed, the
excess-thrust (58.6oz) to weight (104.8oz)
ratio is 0.56:1, which will give steep climbs
and excellent acceleration. This model should
be able to do consecutive loops, and has
sufficient in-flight thrust for almost any
aerobatic maneuver.
“General Notes:
“• This analysis is based on calculations that
take motor heating effects into account.
“• These calculations are based on
mathematical models that may not account for
all limitations of the components used. Always
consult the power system component
manufacturers to ensure that no limits
(current, rpm, etc.) are being exceeded.”
This should be enough to get you over the
initial hump of looking at the opening screens
and wondering what to do next. From this
point you can tweak the setups by changing all
the parameters as much as you please. You
can set up filters to assess only propellers
within a certain range or gear ratios, etc. It’s
extremely versatile.
You can hit the “Opinion” button anytime
you don’t fully understand the results, and it
will spit out a report, as shown, along with
recommendations.
I’ve mentioned before that data-gathering
tools are essential if you want to get into
tweaking and experimenting with electrics.
I’ve been using the Micro Power from Eagle
Tree Systems, and it does everything most
modelers will want to do.
I recently obtained the Seagull system from
Eagle Tree, complete with wireless data
transfer. This is the pro-level unit, and now I
can monitor the two motors I have ganged to
an Inner Demon Gearbox in my giant-scale
Pitts. A full article about this incredible system
is to come!
I hate that space has run out. Next time I will
look at ElectriCalc and how to get going with
it. Again, all electric-power fliers should own
at least one of these programs, especially as
they’re learning. If you don’t want to play
engineer, you don’t have to; just copy
someone else and have fun at the field. MA
Sources:
MotoCalc
(519) 638-5470
www.motocalc.com
Edition: Model Aviation - 2007/12
Page Numbers: 123,124,125
IT’S HARD TO think of Christmas when it’s the end of August
and the temps here in North Carolina have been hovering in the
high 90s or at 100° for the last couple weeks. Then again, it’s
refreshing to think that it will be much cooler by the time you read
this.
I hope everyone has a great holiday season and that the new
year brings you all the toys that make life so much fun. Thanks for
your support this year; I hope we have another great one.
Farewell to a Friend: Awhile back I
mentioned working on an Approach
Engineering Cobra conversion kit for my
Swift helicopter. James Linder founded
Approach Engineering in Utah, and I’m
extremely sad to report that he was killed in
August in an Apache crash.
James was a full-time instructor pilot for
the Utah National Guard and, more
importantly, a loving husband, father, and
good friend to many people. He and I were
collaborating on adapting his new Apache kit
to fit the Quick QJ-10 airframe I had just sent
him. He was a talented designer and an
incredibly smart engineer by trade.
I’m at a loss for how to express my
feelings to his family and the rest of his
friends. I hope someone will buy his kit line
and continue it, but there is no way to make
up for the loss of James and his friendship.
On the Soapbox: I want to remind everyone
about the purpose of the last few “Electrics”
columns and the lessons within. They were
intended to be guidelines showing how to
plan a power system.
A farewell to James Linder
December 2007 123
Electrics Greg Gimlick | [email protected]
Also included in this column:
• A look at electric airplane
performance-simulation
programs
• Li-Poly discharging clarification
James Linder with his partially framed-up electric-powered
Cobra in front of the beautiful Utah countryside.
An Approach Engineering Cobra fitted to a Quick EP-8. The Approach
kits are of all-built-up construction and perfectly engineered. The
company’s future is in limbo since James Linder’s premature death.
Greg’s newest data-acquisition system is the Seagull unit. It is the best affordable system he
has found. Wireless transmission sends data to a module mounted on a radio, in real time.
124 MODEL AVIATION
Below: MotoCalc generates this report
with all the parameters charted at
various airspeeds and full throttle. If this
is confusing, choose “Opinion” for a
written explanation.
Bottom: You’ll get to MotoCalc’s main
window when you complete the
MotoWizard. From here you can
generate the report and see the
equipment for your setup.
Left: The MotoWizard window is the
place to start if you’re learning
MotoCalc. It will take you through the
setup step by step.
I’ve taken some heat for the August issue, in which I showed
how to figure out amp minutes and divide by current, etc. to make
decisions regarding duration. Some readers took me to task for
planning on discharging Li-Poly batteries to their full capacity.
Those were exercises to show you how to do the calculations
without regard to efficiency, battery type, etc. I thought I made that
clear, but apparently not. I am not advocating complete discharge.
It’s all relative in planning, though; if you get more duration
from one setup than another, it will still be so when you figure in
efficiency or reduce the discharge to 70% of capacity. The purpose
is to understand the steps involved.
Electric Airplane Performance-Simulation Programs: One thing is
without question in my mind: owning one of the simulation
programs will save you more money than it costs in the long run and
teach you more than you will learn in hours surfing the Internet.
Are they perfect? No, but they are a lot more accurate than you
will be with your pencil, paper, and calculator. These programs
contain databases and algorithms to consider all the parameters and
can be updated with ease.
I believe that the top two programs are ElectriCalc and MotoCalc.
I’m going to touch on each of them briefly this month and next, but I
won’t pretend to do them justice since that would require a full feature
article for each.
MotoCalc (Mcalc) is the brainchild of
Stefan Vorkoetter of Capable Computing, Inc.
He has been around the electric-flight world
for a long time and can be found on many
RCGroups forums.
Right off the bat you’ll appreciate the Web
support the company provides for this
simulation. You can download a full-featured
version for a trial period before you buy it, so
there’s no risk.
MotoCalc has often been described as
difficult to learn, and it probably does have a
slightly steeper learning curve than ElectriCalc
for a beginner. Don’t let that influence your
decision, though, until you’ve gone through
the tutorials, both online and off.
The tutorials will carry you step by step
through the whole planning process. Most
questions I’ve gotten about MotoCalc through
the years could have been answered had the
user taken some time to read the manual or try
the tutorials. They will teach you more than
any book on the market.
When you open the program you’re
greeted with a “tip window”; it’s wise to keep
that activated while you learn your way. The
next screen is the MotoWizard, which will
walk you through each step of a model from
start to finish.
I plugged in a Sig LT-25 and made choices
along the way as it worked across the screen.
Following are the steps and selections I
entered.
• Performance: Sport
• Model: Wingspan, area, and weight without
motor, battery, and ESC
• Airfoil type: Basic info such as flatbottomed,
semi-symmetrical, etc.
• Thickness: You are given diagrams and you
pick thin, fat, etc.
• Field: Elevation; I left it at sea level.
• Motor: Your choice; brushless, brushed,
either. I chose brushless.
• Gear & Prop: I chose direct or geared and a
maximum propeller size of 14 x 10.
• Battery: You can choose “any” and let it
pick, but I selected A123 cells in a six-cell
pack.
• Results: You will be given a list of motors to
select from with ratings to let you know
Mcalc’s best choice. I chose the
recommendation of a Neu 2215/1.5Y.
When you complete these steps and hit
“Accept,” the program will take you to the
main window. From there you can select
“Compute Report” and you’ll be presented
with a window full of information.
This is where many people get confused
and discouraged, but there is a not-so-hidden
gem you’ll learn to love: the “Opinion” button.
When you hit this you’re presented with an
easy-to-read opinion of your setup. Following
was my result.
“MotOpinion—Sig LT-25
“Sea Level, 29.92inHg, 59°F
“Motor: Neu 2215/1.5Y BAM; 1020rpm/V;
1.6A no-load; 0.004 Ohms.
“Battery: A123 ANR26650 M1 (30C); 6 cells;
2300mAh @ 3.3V; 0.016 Ohms/cell.
“Speed Control: Castle Creations Phoenix 60;
0.0012 Ohms; High rate.
“Drive System: Generic 14x9in Prop w/2.5:1
Gearbox; 14x9 (Pconst=1.17; Tconst=1)
geared 2.5:1 (Eff=92%).
“Airframe: Sig LT-25; 724sq.in; 104.8oz
RTF; 20.8oz/sq.ft; Cd=0.059; Cl=0.6;
Clopt=0.67; Clmax=1.24.
“Stats: 83 W/lb in; 72 W/lb out; 21mph stall;
29mph opt @ 57% (32:06, 66°F); 30mph level
@ 59% (31:10, 66°F); 1450ft/min @ 35.1°; -
244ft/min @ -5.5°.
“Possible Power System Problems:
“• The full-throttle motor current at the
best lift-to-drag ratio airspeed (31.6A) is
lower than the motor’s maximum efficiency
current (81.8A). A higher current level
would improve system efficiency.
“• Current can be increased by using more
cells, a larger diameter or higher pitched
propeller, a lower gear ratio, or some
combination of these methods.
“Power System Notes:
“• The voltage (16.6V) exceeds 12V. Be
sure the speed control is rated for at least
the number of cells specified above.
“Aerodynamic Notes:
“• The static pitch speed (57mph) is within the
range of approximately 2.5 to 3 times the
model’s stall speed (21mph), which is
considered ideal for good performance.
“• With a wing loading of 20.8oz/sq.ft, a model
of this size will have trainer-like flying
characteristics. It would make an ideal
trainer, for use in calm to light wind
conditions.
“• The static thrust (94.7oz) to weight
(104.8oz) ratio is 0.9:1, which will result in
very short take-off runs, no difficulty taking off
from grass surfaces (assuming sufficiently
large wheels), and steep climb-outs.
“• At the best lift-to-drag ratio airspeed, the
excess-thrust (58.6oz) to weight (104.8oz)
ratio is 0.56:1, which will give steep climbs
and excellent acceleration. This model should
be able to do consecutive loops, and has
sufficient in-flight thrust for almost any
aerobatic maneuver.
“General Notes:
“• This analysis is based on calculations that
take motor heating effects into account.
“• These calculations are based on
mathematical models that may not account for
all limitations of the components used. Always
consult the power system component
manufacturers to ensure that no limits
(current, rpm, etc.) are being exceeded.”
This should be enough to get you over the
initial hump of looking at the opening screens
and wondering what to do next. From this
point you can tweak the setups by changing all
the parameters as much as you please. You
can set up filters to assess only propellers
within a certain range or gear ratios, etc. It’s
extremely versatile.
You can hit the “Opinion” button anytime
you don’t fully understand the results, and it
will spit out a report, as shown, along with
recommendations.
I’ve mentioned before that data-gathering
tools are essential if you want to get into
tweaking and experimenting with electrics.
I’ve been using the Micro Power from Eagle
Tree Systems, and it does everything most
modelers will want to do.
I recently obtained the Seagull system from
Eagle Tree, complete with wireless data
transfer. This is the pro-level unit, and now I
can monitor the two motors I have ganged to
an Inner Demon Gearbox in my giant-scale
Pitts. A full article about this incredible system
is to come!
I hate that space has run out. Next time I will
look at ElectriCalc and how to get going with
it. Again, all electric-power fliers should own
at least one of these programs, especially as
they’re learning. If you don’t want to play
engineer, you don’t have to; just copy
someone else and have fun at the field. MA
Sources:
MotoCalc
(519) 638-5470
www.motocalc.com
