THIS IS the 43rd
monthly column in
which I try to give
you the best
possible answers to
questions you have
written or E-mailed
to me. Each new
inquiry is given a
sequential number
for future reference.
Many questions
and answers have
been posted to the AMA Web site at www.modelaircraft.org/
mag/faq/index.asp. Unfortunately that posting stopped in August
2005 and will not continue until this section of the AMA Web
site is revamped. In the meantime, if you can’t find the subject
matter you are interested in, drop me an E-mail or letter and I
will try to assist you.
Q316: “I’ve read a lot recently on the various model nets and
forums about replacing Ni-Cd and NiMH RC transmitter batteries
with lithium batteries. Is this technically possible? Would I benefit
by doing this?”
A316: It is certainly possible from a technical standpoint. I suspect
that many RC manufacturers will be switching to Lithium-type
batteries with their next-generation equipment.
At full charge Ni-Cd and NiMH eight-cell battery packs provide
approximately 10.5 volts. The built-in transmitter low-voltage
alarms generally go off at roughly 8.8 volts. A three-cell Li-Poly
battery will supply 11.1 volts (nominal) at full charge.
The slight extra voltage shouldn’t be a problem for most RC
transmitters, but if you go this route you might check with your
particular RC-system manufacturer. You might also consider using
Li-Ion cells such as the A123.
With the Li-Ion cells you can obtain close to 10 volts at full
charge (3.3 volts with three cells). The alarm’s going off at 8.8
volts (if it does!) will still prevent your Lithium cells from being
discharged to less than recommended limits.
Your biggest considerations are going to be how to fit the
Lithium battery pack into your transmitter and how to charge it. If
you use a 2100 mAh-capacity Li-Poly battery, it would normally be
charged at 1C, or 2.1 amps.
Many RC-transmitter internal charging circuits have a fuse,
which might blow at that amount of current. Therefore, I suggest
that you charge the Lithium battery externally to the transmitter.
As you can see in a photo, I removed the rear batterycompartment
cover on my Hitec Optic 6 transmitter and swapped
in a three-cell ParkZone 2100 mAh Li-Poly battery pack, which is
attached with Velcro tape.
The main power leads are connected directly to the transmitter
connector. (You should be able to obtain a mating connector from
the RC manufacturer.) The balanced charger connector on the pack
is easily accessible when it comes time to charge, allowing for
direct charging of the battery (not through the transmitter circuit).
Because of the size of the particular Li-Poly battery I selected, it
is impossible to use the battery-compartment cover. But since the
pack remains almost flush with the case, I didn’t see that as a
problem.
From a cost standpoint, a replacement eight-cell, 1700 mAh Ni-
Cd battery pack would cost me approximately $35 with a
Using Lithium batteries in your RC transmitter
October 2007 89
? Frequently Asked Questions Bob Aberle | [email protected]
Also included in this column:
• What to do when only half the
wing is shown on the plans
• A motor timer for FF
applications
• Micro indoor RC models now
available as RTFs
Newly installed three-cell Li-Poly battery pack held in place with
Velcro tape. Battery-compartment cover is no longer used. FMA
Direct Cellpro 4S (A) charges pack at 4.0 amps (roughly 2C rate),
which can fully charge this battery in roughly 30 minutes.
Rear of Hitec Optic 6 RC transmitter showing batterycompartment
cover and standard eight-cell, 600 mAh Ni-Cd
battery pack removed.
10sig3.QXD 8/23/07 2:51 PM Page 89
90 MODEL AVIATION
Components of electric power system for
FF model. Total weight is 1.75 ounces
including two-cell, 300 mAh Li-Poly battery
pack. This system would be ideal for flying
approximately 5-ounce (1/2A size) Nostalgia
FF model.
If full-size plans show only half the wing, turn them over and apply a thin coat of mineral oil.
It will make the plans translucent so the other wing panel can be accurately constructed.
New E-flite Park 180 brushless outrunner
motor is perfect for an FF model. It weighs
8.5 grams and is being sold with companion
ESC for only $42.
Unique 2-gram Z Tron timer provides timer
control of motors, making it possible to fly
FF model aircraft using electric power.
Cox Hobby Distributors’ indoor RC Playboy Senior (classic Old-Timer) RTF. It is electric
powered. A dummy Cox Tee Dee .010 engine is mounted in the nose for added realism.
connector. I’ve found three-cell, 2100 mAh
Li-Poly packs for as little as $40. You will
have to purchase and attach the necessary
mating transmitter connector, but the
difference in price is almost negligible.
I did find several three-cell Li-Poly
packs that were configured to fit into a
transmitter so the compartment cover
would fit in place. If you go that route I
still recommend that you access the battery
and charge it directly.
One of the advantages of using a Li-
Poly battery is that it is charged at a 1C
rate, which should take only an hour to
bring a depleted pack to full charge. I use a
new FMA Direct Cellpro 4S (4 amp)
balanced charger that allows me to use a
2C (4 amp) charge current that requires
only 30 minutes for a full charge. That
means it would take little time to get the
transmitter ready for a flight session.
In addition, the Lithium batteries’
extremely low self-discharge rate means a
charged pack will remain that way for a
few months, although for long-term
storage the packs should only be at
roughly half charge (half capacity).
I like using Lithium batteries on RC
transmitters that have an LCD screen; it
continually displays the transmitter
voltage with a digital readout. That way I
always know where I am with respect to
10sig3.QXD 8/23/07 2:30 PM Page 90
the minimum recommended discharge
voltage of approximately 3.0 per cell.
As I mentioned, RC manufacturers
will soon be adapting their transmitter
battery compartments to accept Li-Poly
and Li-Ion. Internal charging circuits will
have to be adapted to the higher current
levels.
Improved battery safety, thanks to
balanced charging, should make it
possible and safe to charge the Lithium
packs when they are located inside an RC
transmitter. I believe this is the way we
will be going in the future.
Q317: “I purchased a set of full size plans
from a hobby publication and was
disappointed to see only half of the wing
shown. How am I supposed to build the
other wing panel that is not shown?”
A317: Since I’ve designed and had
published more than 50 models in the past
35 years, I can give you some insight into
this situation and provide a suggestion.
When I show only half a wing on my
plans, it isn’t because I’m lazy!
The larger the full-size plans, the more
that set of plans costs. That being the
case, I often draw only half the wing to
keep the size of the plans to the minimum.
But how do you build the half of the
wing that is not shown? Surely you can’t
build two right wing panels!
I turn the plans over and rub mineral
oil onto them with paper towels. (This
type of oil is available at almost every
pharmacy in the country.) Almost
immediately the plans paper turns
translucent, showing the reverse image
you need to build the other panel.
After oiling the plans I position
parchment paper (which you can find by
the roll in supermarkets) over them. This
prevents the wood from sticking to the
plans and prevents what is left of the
mineral oil from getting on the wood.
The nice thing about mineral oil is that
it dries quickly, leaving the plans almost
like new for storage purposes and later
use. I found that vegetable oils and olive
oil did not work as well and that the
residue practically ruins the plans.
Q318: “I’ve seen several of the new, very
small and lightweight brushless outrunner
motors. The prices seem to be continually
coming down making them quite
attractive. But I’m a free flight modeler
and was wondering if these new motors
can be adapted to aircraft that don’t
employ RC control?”
A318: In one of last year’s columns I
wrote about motors and CL use. For that
application electric-power expert Sergio
Zigras, who operates the company Z
Tron, developed a timer control.
I have learned that Sergio has
developed and is now manufacturing a
motor timer for FF applications. The
device costs $30 and weighs only 2
grams. It will work with brushed and
brushless motors and their respective
speed controllers.
Motor run time can be adjusted to
between one and 63 seconds in onesecond
increments. The motor speed
control can be varied from full off to full
on in 63 steps. And if that weren’t
enough, you can hook up a microservo to
operate a DT (like a pop-up stabilizer),
which can be set from .25 to 15 minutes.
I made a power package using either a
BSD Micro RC Mighty Midget 13/4/15T
brushless outrunner motor or the new
Horizon E-flite Park 180 motor and a
Phoenix-10 brushless ESC, the Z Tron
timer, a Blue Arrow 2.5-gram servo (to
operate the DT), and an FMA Direct
Cellpro two-cell, 300 mAh Li-Poly
battery.
All those components resulted in a
total airborne weight of 1.75 ounces. An
.049-powered (1/2A) FF model typically
weighs 5 ounces.
Here is your chance to build a
Nostalgia FF design, such as the Fubar
36, the Mini-Hogan 34, or the Baby
Phoenix, and power it with electric. Being
able to limit the motor-run duration and
power level, along with a DT, allows you
to fly it easily in a small field or school
yard. With quiet electric power you can
even fly at dawn and no one will know
you are doing it.
You can purchase the Z Tron FF timer
from BSD Micro RC for $30. Bob Selman
has the complete Z Tron instruction sheet
posted to his Web site at www.bsdmicro
rc.com/pdfs/Products/FF_Timer.pdf.
Q319: “I saw several references recently
to RTF models that are now being made
available expressly for indoor RC flying.
Is this becoming a trend? Should I expect
to see more and more micro RTF RC
indoor models coming on the hobby
market?”
A319: Yes! Plantraco in Canada was one
of the first to offer a complete RTF indoor
RC model package, which included the
RC and power system. It has been
reported about favorably in the modeling
press.
In a recent FAQ column I mentioned
the 18-gram ParkZone Cessna 210
Centurion that Horizon Hobby is selling.
Another new entry, which was shown at
the 2007 WRAM Show in New York and
the Toledo Show, is Cox Hobby
Distributors’ Lil Playboy.
The replica Old-Timer design has an
18-inch wingspan and weighs 45 grams
(1.6 ounces). A 135 mAh Li-Poly battery
can provide eight-minute flights on a
charge. The street price is expected to be
$39, and the model will initially be
available at www.coxmodels.com.
If you are already a sport RC flier and
want more details about indoor RC flying,
read “Intro to Indoor RC Guide” at
www.cloud9rc.com/indoorflying.asp.
Edition: Model Aviation - 2007/10
Page Numbers: 89,90,92
Edition: Model Aviation - 2007/10
Page Numbers: 89,90,92
THIS IS the 43rd
monthly column in
which I try to give
you the best
possible answers to
questions you have
written or E-mailed
to me. Each new
inquiry is given a
sequential number
for future reference.
Many questions
and answers have
been posted to the AMA Web site at www.modelaircraft.org/
mag/faq/index.asp. Unfortunately that posting stopped in August
2005 and will not continue until this section of the AMA Web
site is revamped. In the meantime, if you can’t find the subject
matter you are interested in, drop me an E-mail or letter and I
will try to assist you.
Q316: “I’ve read a lot recently on the various model nets and
forums about replacing Ni-Cd and NiMH RC transmitter batteries
with lithium batteries. Is this technically possible? Would I benefit
by doing this?”
A316: It is certainly possible from a technical standpoint. I suspect
that many RC manufacturers will be switching to Lithium-type
batteries with their next-generation equipment.
At full charge Ni-Cd and NiMH eight-cell battery packs provide
approximately 10.5 volts. The built-in transmitter low-voltage
alarms generally go off at roughly 8.8 volts. A three-cell Li-Poly
battery will supply 11.1 volts (nominal) at full charge.
The slight extra voltage shouldn’t be a problem for most RC
transmitters, but if you go this route you might check with your
particular RC-system manufacturer. You might also consider using
Li-Ion cells such as the A123.
With the Li-Ion cells you can obtain close to 10 volts at full
charge (3.3 volts with three cells). The alarm’s going off at 8.8
volts (if it does!) will still prevent your Lithium cells from being
discharged to less than recommended limits.
Your biggest considerations are going to be how to fit the
Lithium battery pack into your transmitter and how to charge it. If
you use a 2100 mAh-capacity Li-Poly battery, it would normally be
charged at 1C, or 2.1 amps.
Many RC-transmitter internal charging circuits have a fuse,
which might blow at that amount of current. Therefore, I suggest
that you charge the Lithium battery externally to the transmitter.
As you can see in a photo, I removed the rear batterycompartment
cover on my Hitec Optic 6 transmitter and swapped
in a three-cell ParkZone 2100 mAh Li-Poly battery pack, which is
attached with Velcro tape.
The main power leads are connected directly to the transmitter
connector. (You should be able to obtain a mating connector from
the RC manufacturer.) The balanced charger connector on the pack
is easily accessible when it comes time to charge, allowing for
direct charging of the battery (not through the transmitter circuit).
Because of the size of the particular Li-Poly battery I selected, it
is impossible to use the battery-compartment cover. But since the
pack remains almost flush with the case, I didn’t see that as a
problem.
From a cost standpoint, a replacement eight-cell, 1700 mAh Ni-
Cd battery pack would cost me approximately $35 with a
Using Lithium batteries in your RC transmitter
October 2007 89
? Frequently Asked Questions Bob Aberle | [email protected]
Also included in this column:
• What to do when only half the
wing is shown on the plans
• A motor timer for FF
applications
• Micro indoor RC models now
available as RTFs
Newly installed three-cell Li-Poly battery pack held in place with
Velcro tape. Battery-compartment cover is no longer used. FMA
Direct Cellpro 4S (A) charges pack at 4.0 amps (roughly 2C rate),
which can fully charge this battery in roughly 30 minutes.
Rear of Hitec Optic 6 RC transmitter showing batterycompartment
cover and standard eight-cell, 600 mAh Ni-Cd
battery pack removed.
10sig3.QXD 8/23/07 2:51 PM Page 89
90 MODEL AVIATION
Components of electric power system for
FF model. Total weight is 1.75 ounces
including two-cell, 300 mAh Li-Poly battery
pack. This system would be ideal for flying
approximately 5-ounce (1/2A size) Nostalgia
FF model.
If full-size plans show only half the wing, turn them over and apply a thin coat of mineral oil.
It will make the plans translucent so the other wing panel can be accurately constructed.
New E-flite Park 180 brushless outrunner
motor is perfect for an FF model. It weighs
8.5 grams and is being sold with companion
ESC for only $42.
Unique 2-gram Z Tron timer provides timer
control of motors, making it possible to fly
FF model aircraft using electric power.
Cox Hobby Distributors’ indoor RC Playboy Senior (classic Old-Timer) RTF. It is electric
powered. A dummy Cox Tee Dee .010 engine is mounted in the nose for added realism.
connector. I’ve found three-cell, 2100 mAh
Li-Poly packs for as little as $40. You will
have to purchase and attach the necessary
mating transmitter connector, but the
difference in price is almost negligible.
I did find several three-cell Li-Poly
packs that were configured to fit into a
transmitter so the compartment cover
would fit in place. If you go that route I
still recommend that you access the battery
and charge it directly.
One of the advantages of using a Li-
Poly battery is that it is charged at a 1C
rate, which should take only an hour to
bring a depleted pack to full charge. I use a
new FMA Direct Cellpro 4S (4 amp)
balanced charger that allows me to use a
2C (4 amp) charge current that requires
only 30 minutes for a full charge. That
means it would take little time to get the
transmitter ready for a flight session.
In addition, the Lithium batteries’
extremely low self-discharge rate means a
charged pack will remain that way for a
few months, although for long-term
storage the packs should only be at
roughly half charge (half capacity).
I like using Lithium batteries on RC
transmitters that have an LCD screen; it
continually displays the transmitter
voltage with a digital readout. That way I
always know where I am with respect to
10sig3.QXD 8/23/07 2:30 PM Page 90
the minimum recommended discharge
voltage of approximately 3.0 per cell.
As I mentioned, RC manufacturers
will soon be adapting their transmitter
battery compartments to accept Li-Poly
and Li-Ion. Internal charging circuits will
have to be adapted to the higher current
levels.
Improved battery safety, thanks to
balanced charging, should make it
possible and safe to charge the Lithium
packs when they are located inside an RC
transmitter. I believe this is the way we
will be going in the future.
Q317: “I purchased a set of full size plans
from a hobby publication and was
disappointed to see only half of the wing
shown. How am I supposed to build the
other wing panel that is not shown?”
A317: Since I’ve designed and had
published more than 50 models in the past
35 years, I can give you some insight into
this situation and provide a suggestion.
When I show only half a wing on my
plans, it isn’t because I’m lazy!
The larger the full-size plans, the more
that set of plans costs. That being the
case, I often draw only half the wing to
keep the size of the plans to the minimum.
But how do you build the half of the
wing that is not shown? Surely you can’t
build two right wing panels!
I turn the plans over and rub mineral
oil onto them with paper towels. (This
type of oil is available at almost every
pharmacy in the country.) Almost
immediately the plans paper turns
translucent, showing the reverse image
you need to build the other panel.
After oiling the plans I position
parchment paper (which you can find by
the roll in supermarkets) over them. This
prevents the wood from sticking to the
plans and prevents what is left of the
mineral oil from getting on the wood.
The nice thing about mineral oil is that
it dries quickly, leaving the plans almost
like new for storage purposes and later
use. I found that vegetable oils and olive
oil did not work as well and that the
residue practically ruins the plans.
Q318: “I’ve seen several of the new, very
small and lightweight brushless outrunner
motors. The prices seem to be continually
coming down making them quite
attractive. But I’m a free flight modeler
and was wondering if these new motors
can be adapted to aircraft that don’t
employ RC control?”
A318: In one of last year’s columns I
wrote about motors and CL use. For that
application electric-power expert Sergio
Zigras, who operates the company Z
Tron, developed a timer control.
I have learned that Sergio has
developed and is now manufacturing a
motor timer for FF applications. The
device costs $30 and weighs only 2
grams. It will work with brushed and
brushless motors and their respective
speed controllers.
Motor run time can be adjusted to
between one and 63 seconds in onesecond
increments. The motor speed
control can be varied from full off to full
on in 63 steps. And if that weren’t
enough, you can hook up a microservo to
operate a DT (like a pop-up stabilizer),
which can be set from .25 to 15 minutes.
I made a power package using either a
BSD Micro RC Mighty Midget 13/4/15T
brushless outrunner motor or the new
Horizon E-flite Park 180 motor and a
Phoenix-10 brushless ESC, the Z Tron
timer, a Blue Arrow 2.5-gram servo (to
operate the DT), and an FMA Direct
Cellpro two-cell, 300 mAh Li-Poly
battery.
All those components resulted in a
total airborne weight of 1.75 ounces. An
.049-powered (1/2A) FF model typically
weighs 5 ounces.
Here is your chance to build a
Nostalgia FF design, such as the Fubar
36, the Mini-Hogan 34, or the Baby
Phoenix, and power it with electric. Being
able to limit the motor-run duration and
power level, along with a DT, allows you
to fly it easily in a small field or school
yard. With quiet electric power you can
even fly at dawn and no one will know
you are doing it.
You can purchase the Z Tron FF timer
from BSD Micro RC for $30. Bob Selman
has the complete Z Tron instruction sheet
posted to his Web site at www.bsdmicro
rc.com/pdfs/Products/FF_Timer.pdf.
Q319: “I saw several references recently
to RTF models that are now being made
available expressly for indoor RC flying.
Is this becoming a trend? Should I expect
to see more and more micro RTF RC
indoor models coming on the hobby
market?”
A319: Yes! Plantraco in Canada was one
of the first to offer a complete RTF indoor
RC model package, which included the
RC and power system. It has been
reported about favorably in the modeling
press.
In a recent FAQ column I mentioned
the 18-gram ParkZone Cessna 210
Centurion that Horizon Hobby is selling.
Another new entry, which was shown at
the 2007 WRAM Show in New York and
the Toledo Show, is Cox Hobby
Distributors’ Lil Playboy.
The replica Old-Timer design has an
18-inch wingspan and weighs 45 grams
(1.6 ounces). A 135 mAh Li-Poly battery
can provide eight-minute flights on a
charge. The street price is expected to be
$39, and the model will initially be
available at www.coxmodels.com.
If you are already a sport RC flier and
want more details about indoor RC flying,
read “Intro to Indoor RC Guide” at
www.cloud9rc.com/indoorflying.asp.
Edition: Model Aviation - 2007/10
Page Numbers: 89,90,92
THIS IS the 43rd
monthly column in
which I try to give
you the best
possible answers to
questions you have
written or E-mailed
to me. Each new
inquiry is given a
sequential number
for future reference.
Many questions
and answers have
been posted to the AMA Web site at www.modelaircraft.org/
mag/faq/index.asp. Unfortunately that posting stopped in August
2005 and will not continue until this section of the AMA Web
site is revamped. In the meantime, if you can’t find the subject
matter you are interested in, drop me an E-mail or letter and I
will try to assist you.
Q316: “I’ve read a lot recently on the various model nets and
forums about replacing Ni-Cd and NiMH RC transmitter batteries
with lithium batteries. Is this technically possible? Would I benefit
by doing this?”
A316: It is certainly possible from a technical standpoint. I suspect
that many RC manufacturers will be switching to Lithium-type
batteries with their next-generation equipment.
At full charge Ni-Cd and NiMH eight-cell battery packs provide
approximately 10.5 volts. The built-in transmitter low-voltage
alarms generally go off at roughly 8.8 volts. A three-cell Li-Poly
battery will supply 11.1 volts (nominal) at full charge.
The slight extra voltage shouldn’t be a problem for most RC
transmitters, but if you go this route you might check with your
particular RC-system manufacturer. You might also consider using
Li-Ion cells such as the A123.
With the Li-Ion cells you can obtain close to 10 volts at full
charge (3.3 volts with three cells). The alarm’s going off at 8.8
volts (if it does!) will still prevent your Lithium cells from being
discharged to less than recommended limits.
Your biggest considerations are going to be how to fit the
Lithium battery pack into your transmitter and how to charge it. If
you use a 2100 mAh-capacity Li-Poly battery, it would normally be
charged at 1C, or 2.1 amps.
Many RC-transmitter internal charging circuits have a fuse,
which might blow at that amount of current. Therefore, I suggest
that you charge the Lithium battery externally to the transmitter.
As you can see in a photo, I removed the rear batterycompartment
cover on my Hitec Optic 6 transmitter and swapped
in a three-cell ParkZone 2100 mAh Li-Poly battery pack, which is
attached with Velcro tape.
The main power leads are connected directly to the transmitter
connector. (You should be able to obtain a mating connector from
the RC manufacturer.) The balanced charger connector on the pack
is easily accessible when it comes time to charge, allowing for
direct charging of the battery (not through the transmitter circuit).
Because of the size of the particular Li-Poly battery I selected, it
is impossible to use the battery-compartment cover. But since the
pack remains almost flush with the case, I didn’t see that as a
problem.
From a cost standpoint, a replacement eight-cell, 1700 mAh Ni-
Cd battery pack would cost me approximately $35 with a
Using Lithium batteries in your RC transmitter
October 2007 89
? Frequently Asked Questions Bob Aberle | [email protected]
Also included in this column:
• What to do when only half the
wing is shown on the plans
• A motor timer for FF
applications
• Micro indoor RC models now
available as RTFs
Newly installed three-cell Li-Poly battery pack held in place with
Velcro tape. Battery-compartment cover is no longer used. FMA
Direct Cellpro 4S (A) charges pack at 4.0 amps (roughly 2C rate),
which can fully charge this battery in roughly 30 minutes.
Rear of Hitec Optic 6 RC transmitter showing batterycompartment
cover and standard eight-cell, 600 mAh Ni-Cd
battery pack removed.
10sig3.QXD 8/23/07 2:51 PM Page 89
90 MODEL AVIATION
Components of electric power system for
FF model. Total weight is 1.75 ounces
including two-cell, 300 mAh Li-Poly battery
pack. This system would be ideal for flying
approximately 5-ounce (1/2A size) Nostalgia
FF model.
If full-size plans show only half the wing, turn them over and apply a thin coat of mineral oil.
It will make the plans translucent so the other wing panel can be accurately constructed.
New E-flite Park 180 brushless outrunner
motor is perfect for an FF model. It weighs
8.5 grams and is being sold with companion
ESC for only $42.
Unique 2-gram Z Tron timer provides timer
control of motors, making it possible to fly
FF model aircraft using electric power.
Cox Hobby Distributors’ indoor RC Playboy Senior (classic Old-Timer) RTF. It is electric
powered. A dummy Cox Tee Dee .010 engine is mounted in the nose for added realism.
connector. I’ve found three-cell, 2100 mAh
Li-Poly packs for as little as $40. You will
have to purchase and attach the necessary
mating transmitter connector, but the
difference in price is almost negligible.
I did find several three-cell Li-Poly
packs that were configured to fit into a
transmitter so the compartment cover
would fit in place. If you go that route I
still recommend that you access the battery
and charge it directly.
One of the advantages of using a Li-
Poly battery is that it is charged at a 1C
rate, which should take only an hour to
bring a depleted pack to full charge. I use a
new FMA Direct Cellpro 4S (4 amp)
balanced charger that allows me to use a
2C (4 amp) charge current that requires
only 30 minutes for a full charge. That
means it would take little time to get the
transmitter ready for a flight session.
In addition, the Lithium batteries’
extremely low self-discharge rate means a
charged pack will remain that way for a
few months, although for long-term
storage the packs should only be at
roughly half charge (half capacity).
I like using Lithium batteries on RC
transmitters that have an LCD screen; it
continually displays the transmitter
voltage with a digital readout. That way I
always know where I am with respect to
10sig3.QXD 8/23/07 2:30 PM Page 90
the minimum recommended discharge
voltage of approximately 3.0 per cell.
As I mentioned, RC manufacturers
will soon be adapting their transmitter
battery compartments to accept Li-Poly
and Li-Ion. Internal charging circuits will
have to be adapted to the higher current
levels.
Improved battery safety, thanks to
balanced charging, should make it
possible and safe to charge the Lithium
packs when they are located inside an RC
transmitter. I believe this is the way we
will be going in the future.
Q317: “I purchased a set of full size plans
from a hobby publication and was
disappointed to see only half of the wing
shown. How am I supposed to build the
other wing panel that is not shown?”
A317: Since I’ve designed and had
published more than 50 models in the past
35 years, I can give you some insight into
this situation and provide a suggestion.
When I show only half a wing on my
plans, it isn’t because I’m lazy!
The larger the full-size plans, the more
that set of plans costs. That being the
case, I often draw only half the wing to
keep the size of the plans to the minimum.
But how do you build the half of the
wing that is not shown? Surely you can’t
build two right wing panels!
I turn the plans over and rub mineral
oil onto them with paper towels. (This
type of oil is available at almost every
pharmacy in the country.) Almost
immediately the plans paper turns
translucent, showing the reverse image
you need to build the other panel.
After oiling the plans I position
parchment paper (which you can find by
the roll in supermarkets) over them. This
prevents the wood from sticking to the
plans and prevents what is left of the
mineral oil from getting on the wood.
The nice thing about mineral oil is that
it dries quickly, leaving the plans almost
like new for storage purposes and later
use. I found that vegetable oils and olive
oil did not work as well and that the
residue practically ruins the plans.
Q318: “I’ve seen several of the new, very
small and lightweight brushless outrunner
motors. The prices seem to be continually
coming down making them quite
attractive. But I’m a free flight modeler
and was wondering if these new motors
can be adapted to aircraft that don’t
employ RC control?”
A318: In one of last year’s columns I
wrote about motors and CL use. For that
application electric-power expert Sergio
Zigras, who operates the company Z
Tron, developed a timer control.
I have learned that Sergio has
developed and is now manufacturing a
motor timer for FF applications. The
device costs $30 and weighs only 2
grams. It will work with brushed and
brushless motors and their respective
speed controllers.
Motor run time can be adjusted to
between one and 63 seconds in onesecond
increments. The motor speed
control can be varied from full off to full
on in 63 steps. And if that weren’t
enough, you can hook up a microservo to
operate a DT (like a pop-up stabilizer),
which can be set from .25 to 15 minutes.
I made a power package using either a
BSD Micro RC Mighty Midget 13/4/15T
brushless outrunner motor or the new
Horizon E-flite Park 180 motor and a
Phoenix-10 brushless ESC, the Z Tron
timer, a Blue Arrow 2.5-gram servo (to
operate the DT), and an FMA Direct
Cellpro two-cell, 300 mAh Li-Poly
battery.
All those components resulted in a
total airborne weight of 1.75 ounces. An
.049-powered (1/2A) FF model typically
weighs 5 ounces.
Here is your chance to build a
Nostalgia FF design, such as the Fubar
36, the Mini-Hogan 34, or the Baby
Phoenix, and power it with electric. Being
able to limit the motor-run duration and
power level, along with a DT, allows you
to fly it easily in a small field or school
yard. With quiet electric power you can
even fly at dawn and no one will know
you are doing it.
You can purchase the Z Tron FF timer
from BSD Micro RC for $30. Bob Selman
has the complete Z Tron instruction sheet
posted to his Web site at www.bsdmicro
rc.com/pdfs/Products/FF_Timer.pdf.
Q319: “I saw several references recently
to RTF models that are now being made
available expressly for indoor RC flying.
Is this becoming a trend? Should I expect
to see more and more micro RTF RC
indoor models coming on the hobby
market?”
A319: Yes! Plantraco in Canada was one
of the first to offer a complete RTF indoor
RC model package, which included the
RC and power system. It has been
reported about favorably in the modeling
press.
In a recent FAQ column I mentioned
the 18-gram ParkZone Cessna 210
Centurion that Horizon Hobby is selling.
Another new entry, which was shown at
the 2007 WRAM Show in New York and
the Toledo Show, is Cox Hobby
Distributors’ Lil Playboy.
The replica Old-Timer design has an
18-inch wingspan and weighs 45 grams
(1.6 ounces). A 135 mAh Li-Poly battery
can provide eight-minute flights on a
charge. The street price is expected to be
$39, and the model will initially be
available at www.coxmodels.com.
If you are already a sport RC flier and
want more details about indoor RC flying,
read “Intro to Indoor RC Guide” at
www.cloud9rc.com/indoorflying.asp.