132 MODEL AVIATION
SINCE THIS IS the first column for me, I
would like to welcome all readers. We
share this great passion of flying, and I
hope this will be a fun place to share what
we have all learned throughout the years.
I will try to keep topics as open and
varied as possible. For me Scale Aerobatics
is everything from the 40% Edge to
aerobatics in a small sport Cub, perfecting
a Rolling Circle to the simple loop, how to
compete and how to do your first roll. It’s
all about fun and the learning experience.
More important, it’s about flying.
I have spent most of my modeling
career competing. At last count that’s
almost 30 years. I have been fortunate to
have enjoyed some success, traveling
around the world, and so on, but I love to
fly and can be found fooling around doing
touch-and-gos simply for the fun of it.
Let’s face it: greasing one in for a great
landing is a kick whether you’re a beginner
or a seasoned pro.
There is a level that fits everyone’s time
and ambitions, but I think we can agree that
getting a tip that helps you improve any
part of your hobby is rewarding at any level. That’s why we are
here; I am an open book with no secrets, and I am open to learn
from others and share here.
There are so many great Scale Aerobatics topics. Servos are
extremely important because they are the final link and can have a
large influence on how your model flies. Other than CG and
throws, probably the biggest change you can make is in the servos.
Servo choice is extremely important. I cannot tell you how often I
have seen an aircraft compromised, lost, or at the very least have its
performance greatly affected by using the wrong servo. This is
generally caused by a lack of understanding during the selection
process, so let’s get to it.
Always start with the manufacturers’ recommendations for servos,
and it certainly won’t hurt to exceed the minimums suggested. As I
like to say, you cannot buy a servo that is too fast or too powerful.
To help you pick servos, let’s review what those “specs” really
mean.
The author kicks off his first column writing about servos
[[email protected]]
Radio Control Scale Aerobatics Dave Patrick
Dave’s setup for Dave Patrick Models (DPM) full-wing Cub and
AXI 5330/F3A motor with new Futaba MZ14. Even with a mildmannered
Cub, using coreless servos and optimizing system as
shown can make a big difference.
Dave Patrick with his 1/4-scale Clipped Wing Super Cub. Correctly trimmed, even a highwing
pleasure model can be aerobatic and provide good performance.
Dave’s throw setup for a FuntanaX. Almost all available
movement is used to maximize resolution and power from servos.
Even throttle has much throw and coreless motor.
This little Futaba gem could be the greatest thing in servo
technology. It uses a brushless motor and is expected to enhance
power and speed dramatically.
April 2007 133
DPM Clipped Wing Cub uses Hacker C-50 14XL motor, APC 22 x
10 propeller, and Duralite 10S EVO 20 battery to produce 20
pounds of static thrust.
The FuntanaX 100 is practical and versatile for practicing Scale
Aerobatics. To prevent flutter, high-power servos with stiff metal
gears perform best on models with oversized control surfaces.
• Speed: Faster is better. Speed, or transit time, is usually measured in
the time it takes to move 60°. The faster the better, even on large
models. Any servo with a transit time of less than 0.1 is extremely
fast, and almost all the servos I own are. A time of 0.15 second is still
considered fast, but that is as slow as I would recommend.
Some modelers prefer fewer bigger but slower (0.15-0.20) servos
on large models, and they are used quite successfully. But I would still
choose faster servos, even if it meant more servos needed to get the
torque needed. If you don’t believe me, try a test on your model.
• Torque: Usually given in inch-ounce, this is simply the amount of
push or pull. If your servo claims 100 inch-ounce, with a 1-inch arm,
it will lift 100 ounces. It’s easy.
When looking at the torque specs, refer to the voltage mentioned.
If you plan on using 4.8 volts, which most systems use, and specs
show 6.0 volts, the servo torque will be significantly less. I usually
choose 6.0 volts for the higher torque.
And be careful; some servos are not designed to operate at the
higher voltages and will not only operate improperly, but could fail.
• Type of Motor:
1) Pole: These are usually three- or five-pole power plants; the
five-pole motor is typically better. A pole motor is generally cheaper
but can be reliable and durable.
2) Coreless: These are more expensive but quite a bit better
because of their much lower rotating mass.
When you ask a servo to move, the motor has to accelerate, go
where it was told to go, and stop. This means accelerating and
braking.
If the motor is heavy, the engineers have to design extra time for it
to ramp up to speed and slow. If the timing is incorrect, the servo will
stop before it reaches its position, overshoot, or even wobble back and
forth. If the servo motor is light, such as the coreless variety, it will get
to speed much more easily and can wait until the last moment to brake
the motor to a stop.
Don’t confuse this with transit time or deadband. The result is a
much tighter feel and precision in control.
3) Brushless: Shhhhh; these are a secret. They haven’t even been
released yet, but they are coming.
• Gears
1) Plastic: There is nothing wrong with this kind of gear; if
properly made, they are probably the tightest and most accurate of all
types. They can also be extremely long-lasting and are a bit lighter.
2) Metal: These are normally used when extra strength is needed.
The only negative to metal gears is that they wear more quickly. Some
servos use a combination of metal and plastic for the extra strength
and long life.
• Analog: There is a big rush to buy digital servos, but consider the
analog type before you do for the following reasons.
1) They are generally less expensive.
2) It can be argued that they are more precise because the
movement is not divided into steps. There is, in fact, an infinite number
of positions an analog servo can be asked to go to—not so with digital
servos.
3) They are faster. There is no processor delay in an analog servo.
• Digital: Following are points to think about when considering this
kind of servo.
1) Some digital servos can be programmed. This is a huge feature
for me. I would love to see all digital servos be programmable.
2) “Holding power” is a term for how a digital servo can ramp up
its power rapidly just off position. This is true. This seems helpful in
certain applications, such as helicopters, but because breakout forces
on aerodynamic surfaces are low on airplanes, the benefit is minimal, if
any.
3) Today’s modern digital servos have high clock rates; they update
rapidly. But that is still “in addition to time,” whereas an analog servo
has no such lapse.
When the analog servo gets a signal to change position, it does. A
digital servo has to do a short computation. This takes little time, but
it’s in addition to the response time the analog servo needs to start
moving.
• Voltage: Servos are optimized for a certain voltage. Generally, 4.8
volts or four Ni-Cds in series has been the standard, but five cells or
6.0 volts makes for a faster and more powerful servo. I typically use
6.0 volts.
When you have a fully charged pack vs. a partly charged pack,
there will be a difference in servo speed and torque that can be felt in
certain models. A good way to eliminate this is to use a voltage
regulator. I like to use 6.0 volts and a 5.8 regulator.
Some servos will be damaged by using 6.0 volts. Check with the
manufacturer before doing so.
• Deadband: This is how much you move the stick before the servo
moves. Today’s servos have little deadband, but they all have some.
The amount of deadband is determined by the mechanical slop in gears
because nothing is perfect.
A simple test to find out what I mean is by using the trim. Slowly
move trim in one direction, then go the other direction. The best servos
might move the other way on one beep, and some might even take two
or three.
Hot News! Brushless is a new type of motor that will be appearing in
new high-end servos, and I was told that it will take speed to a new
level. I heard Futaba is close to testing in the
field.
Following are tips for getting the best from
what you have.
1) Set the transmitter to at least 85% of the
available throw. On a Futaba the throw can be
set at 140%; 85% of 140% is 119%. On a JR
it’s 150% x 85%, or 128%. This alone could
make a huge difference in performance.
By starting with a lower value on the
transmitter, you dramatically reduce system
accuracy and available power from servos.
This cannot be overstated.
2) Use the longest control arm that is
practical on a control surface, such as elevator
aileron, and use the outer hole. Now find the
correct servo arm to get the desired throw.
And don’t start with those 3-D rates; work
your way up to it.
3) Make sure there is no slop or friction
anywhere. This is hard to do; perfect is
impossible, but strive for it. You can have the
best equipment and poor performance
because of a sloppy installation.
4) Follow the manufacturers’ directions.
Yes, servos really do make a difference. I
was in California for a trade show and a
vendor asked if I would make the first test
flights on a prototype 33% CAP 232.
Honored by being asked and curious about
this new airplane, off we went to the
beautiful Chino RC field on a near-perfect
day. We did the preliminary checks. All
looked well, and we proceeded with the
testing.
The model flew okay, but it wasn’t
great. It felt kind of like the wing was
heavy, yet it wasn’t. It wasn’t really
locked. So I landed the CAP. I wanted a
closer look.
The manufacturer had the best five-pole
motor servos in it—not coreless. After
some more trimming I could easily see that
this model would never see greatness with
these servos. I asked the owner to try it,
and he thought it was fine since he was a
sport flier.
I strongly suggested that he replace all
the servos with the same brand, but
coreless, with the same size, speed, and
torque.
The next day we met at Chino again
and the weather was a carbon copy. The
new servos had virtually the same speed
and torque, and setup was exactly the
same.
After a quick preflight we were rolling.
When the CAP 232 lifted, I could instantly
feel the difference. This model had totally
improved overnight. I was delighted and
had a great time.
When I handed the owner the sticks, his
first comment was “Wow! I would have never
believed it.”
This was a huge difference with a CAP
232, so there would definitely be a difference
with an airplane such as a Cub. Try it
someday!
I hope this outline helps you understand
some servo lingo and helps you match servos
to your application. Fly safely and enjoy! MA
Edition: Model Aviation - 2007/04
Page Numbers: 132,133,134
Edition: Model Aviation - 2007/04
Page Numbers: 132,133,134
132 MODEL AVIATION
SINCE THIS IS the first column for me, I
would like to welcome all readers. We
share this great passion of flying, and I
hope this will be a fun place to share what
we have all learned throughout the years.
I will try to keep topics as open and
varied as possible. For me Scale Aerobatics
is everything from the 40% Edge to
aerobatics in a small sport Cub, perfecting
a Rolling Circle to the simple loop, how to
compete and how to do your first roll. It’s
all about fun and the learning experience.
More important, it’s about flying.
I have spent most of my modeling
career competing. At last count that’s
almost 30 years. I have been fortunate to
have enjoyed some success, traveling
around the world, and so on, but I love to
fly and can be found fooling around doing
touch-and-gos simply for the fun of it.
Let’s face it: greasing one in for a great
landing is a kick whether you’re a beginner
or a seasoned pro.
There is a level that fits everyone’s time
and ambitions, but I think we can agree that
getting a tip that helps you improve any
part of your hobby is rewarding at any level. That’s why we are
here; I am an open book with no secrets, and I am open to learn
from others and share here.
There are so many great Scale Aerobatics topics. Servos are
extremely important because they are the final link and can have a
large influence on how your model flies. Other than CG and
throws, probably the biggest change you can make is in the servos.
Servo choice is extremely important. I cannot tell you how often I
have seen an aircraft compromised, lost, or at the very least have its
performance greatly affected by using the wrong servo. This is
generally caused by a lack of understanding during the selection
process, so let’s get to it.
Always start with the manufacturers’ recommendations for servos,
and it certainly won’t hurt to exceed the minimums suggested. As I
like to say, you cannot buy a servo that is too fast or too powerful.
To help you pick servos, let’s review what those “specs” really
mean.
The author kicks off his first column writing about servos
[[email protected]]
Radio Control Scale Aerobatics Dave Patrick
Dave’s setup for Dave Patrick Models (DPM) full-wing Cub and
AXI 5330/F3A motor with new Futaba MZ14. Even with a mildmannered
Cub, using coreless servos and optimizing system as
shown can make a big difference.
Dave Patrick with his 1/4-scale Clipped Wing Super Cub. Correctly trimmed, even a highwing
pleasure model can be aerobatic and provide good performance.
Dave’s throw setup for a FuntanaX. Almost all available
movement is used to maximize resolution and power from servos.
Even throttle has much throw and coreless motor.
This little Futaba gem could be the greatest thing in servo
technology. It uses a brushless motor and is expected to enhance
power and speed dramatically.
April 2007 133
DPM Clipped Wing Cub uses Hacker C-50 14XL motor, APC 22 x
10 propeller, and Duralite 10S EVO 20 battery to produce 20
pounds of static thrust.
The FuntanaX 100 is practical and versatile for practicing Scale
Aerobatics. To prevent flutter, high-power servos with stiff metal
gears perform best on models with oversized control surfaces.
• Speed: Faster is better. Speed, or transit time, is usually measured in
the time it takes to move 60°. The faster the better, even on large
models. Any servo with a transit time of less than 0.1 is extremely
fast, and almost all the servos I own are. A time of 0.15 second is still
considered fast, but that is as slow as I would recommend.
Some modelers prefer fewer bigger but slower (0.15-0.20) servos
on large models, and they are used quite successfully. But I would still
choose faster servos, even if it meant more servos needed to get the
torque needed. If you don’t believe me, try a test on your model.
• Torque: Usually given in inch-ounce, this is simply the amount of
push or pull. If your servo claims 100 inch-ounce, with a 1-inch arm,
it will lift 100 ounces. It’s easy.
When looking at the torque specs, refer to the voltage mentioned.
If you plan on using 4.8 volts, which most systems use, and specs
show 6.0 volts, the servo torque will be significantly less. I usually
choose 6.0 volts for the higher torque.
And be careful; some servos are not designed to operate at the
higher voltages and will not only operate improperly, but could fail.
• Type of Motor:
1) Pole: These are usually three- or five-pole power plants; the
five-pole motor is typically better. A pole motor is generally cheaper
but can be reliable and durable.
2) Coreless: These are more expensive but quite a bit better
because of their much lower rotating mass.
When you ask a servo to move, the motor has to accelerate, go
where it was told to go, and stop. This means accelerating and
braking.
If the motor is heavy, the engineers have to design extra time for it
to ramp up to speed and slow. If the timing is incorrect, the servo will
stop before it reaches its position, overshoot, or even wobble back and
forth. If the servo motor is light, such as the coreless variety, it will get
to speed much more easily and can wait until the last moment to brake
the motor to a stop.
Don’t confuse this with transit time or deadband. The result is a
much tighter feel and precision in control.
3) Brushless: Shhhhh; these are a secret. They haven’t even been
released yet, but they are coming.
• Gears
1) Plastic: There is nothing wrong with this kind of gear; if
properly made, they are probably the tightest and most accurate of all
types. They can also be extremely long-lasting and are a bit lighter.
2) Metal: These are normally used when extra strength is needed.
The only negative to metal gears is that they wear more quickly. Some
servos use a combination of metal and plastic for the extra strength
and long life.
• Analog: There is a big rush to buy digital servos, but consider the
analog type before you do for the following reasons.
1) They are generally less expensive.
2) It can be argued that they are more precise because the
movement is not divided into steps. There is, in fact, an infinite number
of positions an analog servo can be asked to go to—not so with digital
servos.
3) They are faster. There is no processor delay in an analog servo.
• Digital: Following are points to think about when considering this
kind of servo.
1) Some digital servos can be programmed. This is a huge feature
for me. I would love to see all digital servos be programmable.
2) “Holding power” is a term for how a digital servo can ramp up
its power rapidly just off position. This is true. This seems helpful in
certain applications, such as helicopters, but because breakout forces
on aerodynamic surfaces are low on airplanes, the benefit is minimal, if
any.
3) Today’s modern digital servos have high clock rates; they update
rapidly. But that is still “in addition to time,” whereas an analog servo
has no such lapse.
When the analog servo gets a signal to change position, it does. A
digital servo has to do a short computation. This takes little time, but
it’s in addition to the response time the analog servo needs to start
moving.
• Voltage: Servos are optimized for a certain voltage. Generally, 4.8
volts or four Ni-Cds in series has been the standard, but five cells or
6.0 volts makes for a faster and more powerful servo. I typically use
6.0 volts.
When you have a fully charged pack vs. a partly charged pack,
there will be a difference in servo speed and torque that can be felt in
certain models. A good way to eliminate this is to use a voltage
regulator. I like to use 6.0 volts and a 5.8 regulator.
Some servos will be damaged by using 6.0 volts. Check with the
manufacturer before doing so.
• Deadband: This is how much you move the stick before the servo
moves. Today’s servos have little deadband, but they all have some.
The amount of deadband is determined by the mechanical slop in gears
because nothing is perfect.
A simple test to find out what I mean is by using the trim. Slowly
move trim in one direction, then go the other direction. The best servos
might move the other way on one beep, and some might even take two
or three.
Hot News! Brushless is a new type of motor that will be appearing in
new high-end servos, and I was told that it will take speed to a new
level. I heard Futaba is close to testing in the
field.
Following are tips for getting the best from
what you have.
1) Set the transmitter to at least 85% of the
available throw. On a Futaba the throw can be
set at 140%; 85% of 140% is 119%. On a JR
it’s 150% x 85%, or 128%. This alone could
make a huge difference in performance.
By starting with a lower value on the
transmitter, you dramatically reduce system
accuracy and available power from servos.
This cannot be overstated.
2) Use the longest control arm that is
practical on a control surface, such as elevator
aileron, and use the outer hole. Now find the
correct servo arm to get the desired throw.
And don’t start with those 3-D rates; work
your way up to it.
3) Make sure there is no slop or friction
anywhere. This is hard to do; perfect is
impossible, but strive for it. You can have the
best equipment and poor performance
because of a sloppy installation.
4) Follow the manufacturers’ directions.
Yes, servos really do make a difference. I
was in California for a trade show and a
vendor asked if I would make the first test
flights on a prototype 33% CAP 232.
Honored by being asked and curious about
this new airplane, off we went to the
beautiful Chino RC field on a near-perfect
day. We did the preliminary checks. All
looked well, and we proceeded with the
testing.
The model flew okay, but it wasn’t
great. It felt kind of like the wing was
heavy, yet it wasn’t. It wasn’t really
locked. So I landed the CAP. I wanted a
closer look.
The manufacturer had the best five-pole
motor servos in it—not coreless. After
some more trimming I could easily see that
this model would never see greatness with
these servos. I asked the owner to try it,
and he thought it was fine since he was a
sport flier.
I strongly suggested that he replace all
the servos with the same brand, but
coreless, with the same size, speed, and
torque.
The next day we met at Chino again
and the weather was a carbon copy. The
new servos had virtually the same speed
and torque, and setup was exactly the
same.
After a quick preflight we were rolling.
When the CAP 232 lifted, I could instantly
feel the difference. This model had totally
improved overnight. I was delighted and
had a great time.
When I handed the owner the sticks, his
first comment was “Wow! I would have never
believed it.”
This was a huge difference with a CAP
232, so there would definitely be a difference
with an airplane such as a Cub. Try it
someday!
I hope this outline helps you understand
some servo lingo and helps you match servos
to your application. Fly safely and enjoy! MA
Edition: Model Aviation - 2007/04
Page Numbers: 132,133,134
132 MODEL AVIATION
SINCE THIS IS the first column for me, I
would like to welcome all readers. We
share this great passion of flying, and I
hope this will be a fun place to share what
we have all learned throughout the years.
I will try to keep topics as open and
varied as possible. For me Scale Aerobatics
is everything from the 40% Edge to
aerobatics in a small sport Cub, perfecting
a Rolling Circle to the simple loop, how to
compete and how to do your first roll. It’s
all about fun and the learning experience.
More important, it’s about flying.
I have spent most of my modeling
career competing. At last count that’s
almost 30 years. I have been fortunate to
have enjoyed some success, traveling
around the world, and so on, but I love to
fly and can be found fooling around doing
touch-and-gos simply for the fun of it.
Let’s face it: greasing one in for a great
landing is a kick whether you’re a beginner
or a seasoned pro.
There is a level that fits everyone’s time
and ambitions, but I think we can agree that
getting a tip that helps you improve any
part of your hobby is rewarding at any level. That’s why we are
here; I am an open book with no secrets, and I am open to learn
from others and share here.
There are so many great Scale Aerobatics topics. Servos are
extremely important because they are the final link and can have a
large influence on how your model flies. Other than CG and
throws, probably the biggest change you can make is in the servos.
Servo choice is extremely important. I cannot tell you how often I
have seen an aircraft compromised, lost, or at the very least have its
performance greatly affected by using the wrong servo. This is
generally caused by a lack of understanding during the selection
process, so let’s get to it.
Always start with the manufacturers’ recommendations for servos,
and it certainly won’t hurt to exceed the minimums suggested. As I
like to say, you cannot buy a servo that is too fast or too powerful.
To help you pick servos, let’s review what those “specs” really
mean.
The author kicks off his first column writing about servos
[[email protected]]
Radio Control Scale Aerobatics Dave Patrick
Dave’s setup for Dave Patrick Models (DPM) full-wing Cub and
AXI 5330/F3A motor with new Futaba MZ14. Even with a mildmannered
Cub, using coreless servos and optimizing system as
shown can make a big difference.
Dave Patrick with his 1/4-scale Clipped Wing Super Cub. Correctly trimmed, even a highwing
pleasure model can be aerobatic and provide good performance.
Dave’s throw setup for a FuntanaX. Almost all available
movement is used to maximize resolution and power from servos.
Even throttle has much throw and coreless motor.
This little Futaba gem could be the greatest thing in servo
technology. It uses a brushless motor and is expected to enhance
power and speed dramatically.
April 2007 133
DPM Clipped Wing Cub uses Hacker C-50 14XL motor, APC 22 x
10 propeller, and Duralite 10S EVO 20 battery to produce 20
pounds of static thrust.
The FuntanaX 100 is practical and versatile for practicing Scale
Aerobatics. To prevent flutter, high-power servos with stiff metal
gears perform best on models with oversized control surfaces.
• Speed: Faster is better. Speed, or transit time, is usually measured in
the time it takes to move 60°. The faster the better, even on large
models. Any servo with a transit time of less than 0.1 is extremely
fast, and almost all the servos I own are. A time of 0.15 second is still
considered fast, but that is as slow as I would recommend.
Some modelers prefer fewer bigger but slower (0.15-0.20) servos
on large models, and they are used quite successfully. But I would still
choose faster servos, even if it meant more servos needed to get the
torque needed. If you don’t believe me, try a test on your model.
• Torque: Usually given in inch-ounce, this is simply the amount of
push or pull. If your servo claims 100 inch-ounce, with a 1-inch arm,
it will lift 100 ounces. It’s easy.
When looking at the torque specs, refer to the voltage mentioned.
If you plan on using 4.8 volts, which most systems use, and specs
show 6.0 volts, the servo torque will be significantly less. I usually
choose 6.0 volts for the higher torque.
And be careful; some servos are not designed to operate at the
higher voltages and will not only operate improperly, but could fail.
• Type of Motor:
1) Pole: These are usually three- or five-pole power plants; the
five-pole motor is typically better. A pole motor is generally cheaper
but can be reliable and durable.
2) Coreless: These are more expensive but quite a bit better
because of their much lower rotating mass.
When you ask a servo to move, the motor has to accelerate, go
where it was told to go, and stop. This means accelerating and
braking.
If the motor is heavy, the engineers have to design extra time for it
to ramp up to speed and slow. If the timing is incorrect, the servo will
stop before it reaches its position, overshoot, or even wobble back and
forth. If the servo motor is light, such as the coreless variety, it will get
to speed much more easily and can wait until the last moment to brake
the motor to a stop.
Don’t confuse this with transit time or deadband. The result is a
much tighter feel and precision in control.
3) Brushless: Shhhhh; these are a secret. They haven’t even been
released yet, but they are coming.
• Gears
1) Plastic: There is nothing wrong with this kind of gear; if
properly made, they are probably the tightest and most accurate of all
types. They can also be extremely long-lasting and are a bit lighter.
2) Metal: These are normally used when extra strength is needed.
The only negative to metal gears is that they wear more quickly. Some
servos use a combination of metal and plastic for the extra strength
and long life.
• Analog: There is a big rush to buy digital servos, but consider the
analog type before you do for the following reasons.
1) They are generally less expensive.
2) It can be argued that they are more precise because the
movement is not divided into steps. There is, in fact, an infinite number
of positions an analog servo can be asked to go to—not so with digital
servos.
3) They are faster. There is no processor delay in an analog servo.
• Digital: Following are points to think about when considering this
kind of servo.
1) Some digital servos can be programmed. This is a huge feature
for me. I would love to see all digital servos be programmable.
2) “Holding power” is a term for how a digital servo can ramp up
its power rapidly just off position. This is true. This seems helpful in
certain applications, such as helicopters, but because breakout forces
on aerodynamic surfaces are low on airplanes, the benefit is minimal, if
any.
3) Today’s modern digital servos have high clock rates; they update
rapidly. But that is still “in addition to time,” whereas an analog servo
has no such lapse.
When the analog servo gets a signal to change position, it does. A
digital servo has to do a short computation. This takes little time, but
it’s in addition to the response time the analog servo needs to start
moving.
• Voltage: Servos are optimized for a certain voltage. Generally, 4.8
volts or four Ni-Cds in series has been the standard, but five cells or
6.0 volts makes for a faster and more powerful servo. I typically use
6.0 volts.
When you have a fully charged pack vs. a partly charged pack,
there will be a difference in servo speed and torque that can be felt in
certain models. A good way to eliminate this is to use a voltage
regulator. I like to use 6.0 volts and a 5.8 regulator.
Some servos will be damaged by using 6.0 volts. Check with the
manufacturer before doing so.
• Deadband: This is how much you move the stick before the servo
moves. Today’s servos have little deadband, but they all have some.
The amount of deadband is determined by the mechanical slop in gears
because nothing is perfect.
A simple test to find out what I mean is by using the trim. Slowly
move trim in one direction, then go the other direction. The best servos
might move the other way on one beep, and some might even take two
or three.
Hot News! Brushless is a new type of motor that will be appearing in
new high-end servos, and I was told that it will take speed to a new
level. I heard Futaba is close to testing in the
field.
Following are tips for getting the best from
what you have.
1) Set the transmitter to at least 85% of the
available throw. On a Futaba the throw can be
set at 140%; 85% of 140% is 119%. On a JR
it’s 150% x 85%, or 128%. This alone could
make a huge difference in performance.
By starting with a lower value on the
transmitter, you dramatically reduce system
accuracy and available power from servos.
This cannot be overstated.
2) Use the longest control arm that is
practical on a control surface, such as elevator
aileron, and use the outer hole. Now find the
correct servo arm to get the desired throw.
And don’t start with those 3-D rates; work
your way up to it.
3) Make sure there is no slop or friction
anywhere. This is hard to do; perfect is
impossible, but strive for it. You can have the
best equipment and poor performance
because of a sloppy installation.
4) Follow the manufacturers’ directions.
Yes, servos really do make a difference. I
was in California for a trade show and a
vendor asked if I would make the first test
flights on a prototype 33% CAP 232.
Honored by being asked and curious about
this new airplane, off we went to the
beautiful Chino RC field on a near-perfect
day. We did the preliminary checks. All
looked well, and we proceeded with the
testing.
The model flew okay, but it wasn’t
great. It felt kind of like the wing was
heavy, yet it wasn’t. It wasn’t really
locked. So I landed the CAP. I wanted a
closer look.
The manufacturer had the best five-pole
motor servos in it—not coreless. After
some more trimming I could easily see that
this model would never see greatness with
these servos. I asked the owner to try it,
and he thought it was fine since he was a
sport flier.
I strongly suggested that he replace all
the servos with the same brand, but
coreless, with the same size, speed, and
torque.
The next day we met at Chino again
and the weather was a carbon copy. The
new servos had virtually the same speed
and torque, and setup was exactly the
same.
After a quick preflight we were rolling.
When the CAP 232 lifted, I could instantly
feel the difference. This model had totally
improved overnight. I was delighted and
had a great time.
When I handed the owner the sticks, his
first comment was “Wow! I would have never
believed it.”
This was a huge difference with a CAP
232, so there would definitely be a difference
with an airplane such as a Cub. Try it
someday!
I hope this outline helps you understand
some servo lingo and helps you match servos
to your application. Fly safely and enjoy! MA