August 2003 97
HELLO MICRO FANS, and greetings from Central Virginia.
Spring has almost sprung in my area, and I have actually gotten some
decent flying days. Of course, being retired from a 7-4 job does
improve the situation when it comes to grabbing the moment.
This column will probably make it out before the big meet in
Waterford, Michigan (May 31-June 1), so I will look forward to
seeing some of you there. The Toledo show is just a few weeks away
as I write this, and I am looking forward to the show itself and the
flying session Saturday night at the Bowling Green State University
field house. Travel safely and get plenty of rest if you are coming; I
was wiped after last year’s session.
I have only made it to one indoor flying session in recent months,
and that was at the National Building Museum in Washington DC. If
you are within a reasonable distance of this great site, I highly
recommend that you come to the sessions. The DC Maxecuters club
organizes the flying, and it does a superb job. The Web site address to
keep up with this activity is www.his.com/~tschmitt/
comingattractions.html. There is plenty of other great stuff on this
Web site.
At the event there was a slightly enlarged Punkin II of my design
that Jay Stargel of Woodbine, Maryland, built. There were two of
these models in identical colors, but I missed the other builder’s name.
Both models were splendid fliers and well suited to this facility.
On a number of occasions I have been asked about a suitable model
choice for someone who is entering the field of micro-flying, indoors
or out. Shown is a Lockheed Electra profile model built from a DJ
Aerotech kit.
This company has a wide series of models (all profile) under the
Dave Robelen
M i c r o - F l y i n g
Route 4, Box 369, Farmville VA 23901; E-mail: [email protected]
Author’s Beechcraft Duchess serves as a spin-tunnel model.
This Lockheed Electra is one of DJ Aerotech’s Roadkill series.
Jay Stargel built this “slightly enlarged” Punkin II.
This Bumble Bee prototype micro UAV spans 8 inches.
08sig4.QXD 5.23.03 1:02 pm Page 97
98 MODEL AVIATION
name of the “Roadkill” series. Check www.djaerotech.com for the
complete line. I have seen everything from bombers to Cubs, with
World War II fighters in between.
Besides featuring some of the nicest laser-cut balsa I have seen,
these kits come complete with the required power unit(s) and
propeller(s). Many—probably most—are set up with aileron and
rudder control with some clever linkage. None of these models are
what I would call difficult to pilot, but the high-wing lightplanes are
a little more forgiving.
In addition to a great line of kits, Don Stackhouse and Joe Hahn
have a section on the DJ Aerotech Web site labeled “Ask J & D,”
which is downright informative. Tell ’em I sent you.
Several years ago when the micro-Unmanned Aerial Vehicle
(UAV) scene was emerging, there were some specifications for
small vehicles and a message that the Department of Defense would
be interested in small-business involvement.
Since the models don’t come much smaller than what I build, I
took an interest in seeing what could be done with the commercial
equipment of the times. I had a Cannon microsystem that was way
ahead of its time in features and several Cox .010 engines with
which to work.
The Bumble Bee (shown) has flown with at least 10 different
wings to look at airfoil and wingspan effects. The one in the picture
has an 8-inch wingspan, and even loaded with the relatively heavy
Cannon gear, it was decent to fly.
One interesting thing was the dihedral effect as I shortened the
wing. The shorter the span, the more pronounced the roll was with
the rudder. Besides being completely flat, this wing has a pair of
plastic fins on the bottom of the tips to further reduce this effect.
The Cox engine showed a great deal of potential as I developed a
carburetor that could be manually set, along with modified porting.
The result was adequate power to fly the relatively high wing
loadings and excellent fuel economy. Flights lasting 10 minutes
became commonplace with the little model with just the tank on the
back of the engine.
No group of government officials was knocking my door down
to spend money on this work, and I could not find anyone who
was interested. Even so, I learned quite a bit about micro air
Carl Miller’s chart shows a performance comparison of various propellers.
The author made this micro diesel prototype and parts.
The author built this spin tunnel which he
uses to conduct numerous tests.
vehicles along the way, so all was not lost.
Just to show that I was slow to give up, I decided to build a small
engine for future work. Shown is the tiny diesel with some spare
parts that I hacked out with my Hobby Lobby lathe and accessories.
It was becoming an exercise in futility as I began to go over the fuel
08sig4.QXD 5.23.03 1:02 pm Page 98
requirements and general lack of literature
on such tiny engines.
Meanwhile, the micromodel movement
had gotten underway and there was a
decent selection of small electric motors, so
I benched the little diesel as I moved into
electric-powered microflight.
Since I am doing a sort of show-andtell,
I might as well go a bit further. For a
number of years my work at NASA
involved testing models in wind tunnels,
and many of those were free-flying,
dynamically scaled aircraft.
Dynamically scaled? It means that not
only is the model pure in the scaled shape
of the full-scale machine, but the weight
and moments of inertia are scaled to the
prototype. The shape of the model is
reduced by a factor of, say, 10, but the
weight is reduced by the scale factor cubed
and the inertias are reduced by the factor to
the fifth power. It’s all very scientific.
One of the more specialized categories
is the spin-tunnel models. These miniatures
are launched into a rising airstream that
supports them as they spin, then the
controls are moved via radio control to
evaluate the potential recovery
characteristics. I was so taken with this
method of model testing that I decided to
try it at home.
One of my models—a Beechcraft
Duchess—is shown sitting on the scales.
The controls are held in the recovery
position with tiny springs while thin threads
pull them into the pro-spin position. A
single-channel CETO receiver along with a
BIRD actuator are used to move the
controls from pro-spin to recovery. All of
this is powered by a pair of watch batteries.
A spin model without a spin tunnel is
not much more than a display piece, so I
built my own vertical spin tunnel, which is
shown. The model is prerotated with a
launcher near the bottom of the chamber,
then the fan at the top is spun up to
establish the correct airflow. Then when the
steady spin is obtained, a signal is sent to
move the controls and the recovery is
measured.
By repeating this process several times
with different control combinations and a
variety of loading conditions, it is possible
to predict with reasonable accuracy how
easy or difficult it would be to recover the
full-scale machine from a spin.
Although I never was able to get any
contracts with private industries for spin
studies, I have learned a great deal, and, as
a bonus, the spin tunnel in the picture is
portable and is a big hit at air shows and
such, where the public has never seen this
sort of equipment.
There is still another side to owning a
wind tunnel: I can study other things as
well. Last season I put together a rig to run
propeller tests with a GWS 180 motor and
LiteStik gearbox. The chart, courtesy of
August 2003 99
Carl Miller, shows a comparison of some
hand-cut propellers, a GWS 9 x 7, and one
of Carl’s ARC propellers.
I was pleased to see that the propeller
design I have been using for a long time
will perform not only as well, but better
than a commercial propeller. The neat part
is that the design I am using has been in the
Free Flight literature for at least 60 years.
Go figure!
I better drift off now and charge up some
of those neat new Lithium-Polymer
batteries so I can get a flight or two in
tomorrow. Take care. MA
TIRED OF PAYING
$1.29 FOR 6 SCREWS?
Our 4-40x1/2 socket
caps sell for $4.35/100
for alloy steel, or
$6.65/100 stainless, or $7.50/50 aluminum.
For fair prices on sensible quantities of the fasteners
you need for model building, call, write or
fax for our free catalog!
Micro Fasteners 800-892-6917
24 Cokesbury Rd., Suite 2 908-236-8120
Lebanon, NJ 08833 fax 908-236-8721
e-mail: [email protected] Internet: http://microfasteners.com
08sig4.QXD 5.23.03 1:02 pm Page 99
Edition: Model Aviation - 2003/08
Page Numbers: 97,98,99
Edition: Model Aviation - 2003/08
Page Numbers: 97,98,99
August 2003 97
HELLO MICRO FANS, and greetings from Central Virginia.
Spring has almost sprung in my area, and I have actually gotten some
decent flying days. Of course, being retired from a 7-4 job does
improve the situation when it comes to grabbing the moment.
This column will probably make it out before the big meet in
Waterford, Michigan (May 31-June 1), so I will look forward to
seeing some of you there. The Toledo show is just a few weeks away
as I write this, and I am looking forward to the show itself and the
flying session Saturday night at the Bowling Green State University
field house. Travel safely and get plenty of rest if you are coming; I
was wiped after last year’s session.
I have only made it to one indoor flying session in recent months,
and that was at the National Building Museum in Washington DC. If
you are within a reasonable distance of this great site, I highly
recommend that you come to the sessions. The DC Maxecuters club
organizes the flying, and it does a superb job. The Web site address to
keep up with this activity is www.his.com/~tschmitt/
comingattractions.html. There is plenty of other great stuff on this
Web site.
At the event there was a slightly enlarged Punkin II of my design
that Jay Stargel of Woodbine, Maryland, built. There were two of
these models in identical colors, but I missed the other builder’s name.
Both models were splendid fliers and well suited to this facility.
On a number of occasions I have been asked about a suitable model
choice for someone who is entering the field of micro-flying, indoors
or out. Shown is a Lockheed Electra profile model built from a DJ
Aerotech kit.
This company has a wide series of models (all profile) under the
Dave Robelen
M i c r o - F l y i n g
Route 4, Box 369, Farmville VA 23901; E-mail: [email protected]
Author’s Beechcraft Duchess serves as a spin-tunnel model.
This Lockheed Electra is one of DJ Aerotech’s Roadkill series.
Jay Stargel built this “slightly enlarged” Punkin II.
This Bumble Bee prototype micro UAV spans 8 inches.
08sig4.QXD 5.23.03 1:02 pm Page 97
98 MODEL AVIATION
name of the “Roadkill” series. Check www.djaerotech.com for the
complete line. I have seen everything from bombers to Cubs, with
World War II fighters in between.
Besides featuring some of the nicest laser-cut balsa I have seen,
these kits come complete with the required power unit(s) and
propeller(s). Many—probably most—are set up with aileron and
rudder control with some clever linkage. None of these models are
what I would call difficult to pilot, but the high-wing lightplanes are
a little more forgiving.
In addition to a great line of kits, Don Stackhouse and Joe Hahn
have a section on the DJ Aerotech Web site labeled “Ask J & D,”
which is downright informative. Tell ’em I sent you.
Several years ago when the micro-Unmanned Aerial Vehicle
(UAV) scene was emerging, there were some specifications for
small vehicles and a message that the Department of Defense would
be interested in small-business involvement.
Since the models don’t come much smaller than what I build, I
took an interest in seeing what could be done with the commercial
equipment of the times. I had a Cannon microsystem that was way
ahead of its time in features and several Cox .010 engines with
which to work.
The Bumble Bee (shown) has flown with at least 10 different
wings to look at airfoil and wingspan effects. The one in the picture
has an 8-inch wingspan, and even loaded with the relatively heavy
Cannon gear, it was decent to fly.
One interesting thing was the dihedral effect as I shortened the
wing. The shorter the span, the more pronounced the roll was with
the rudder. Besides being completely flat, this wing has a pair of
plastic fins on the bottom of the tips to further reduce this effect.
The Cox engine showed a great deal of potential as I developed a
carburetor that could be manually set, along with modified porting.
The result was adequate power to fly the relatively high wing
loadings and excellent fuel economy. Flights lasting 10 minutes
became commonplace with the little model with just the tank on the
back of the engine.
No group of government officials was knocking my door down
to spend money on this work, and I could not find anyone who
was interested. Even so, I learned quite a bit about micro air
Carl Miller’s chart shows a performance comparison of various propellers.
The author made this micro diesel prototype and parts.
The author built this spin tunnel which he
uses to conduct numerous tests.
vehicles along the way, so all was not lost.
Just to show that I was slow to give up, I decided to build a small
engine for future work. Shown is the tiny diesel with some spare
parts that I hacked out with my Hobby Lobby lathe and accessories.
It was becoming an exercise in futility as I began to go over the fuel
08sig4.QXD 5.23.03 1:02 pm Page 98
requirements and general lack of literature
on such tiny engines.
Meanwhile, the micromodel movement
had gotten underway and there was a
decent selection of small electric motors, so
I benched the little diesel as I moved into
electric-powered microflight.
Since I am doing a sort of show-andtell,
I might as well go a bit further. For a
number of years my work at NASA
involved testing models in wind tunnels,
and many of those were free-flying,
dynamically scaled aircraft.
Dynamically scaled? It means that not
only is the model pure in the scaled shape
of the full-scale machine, but the weight
and moments of inertia are scaled to the
prototype. The shape of the model is
reduced by a factor of, say, 10, but the
weight is reduced by the scale factor cubed
and the inertias are reduced by the factor to
the fifth power. It’s all very scientific.
One of the more specialized categories
is the spin-tunnel models. These miniatures
are launched into a rising airstream that
supports them as they spin, then the
controls are moved via radio control to
evaluate the potential recovery
characteristics. I was so taken with this
method of model testing that I decided to
try it at home.
One of my models—a Beechcraft
Duchess—is shown sitting on the scales.
The controls are held in the recovery
position with tiny springs while thin threads
pull them into the pro-spin position. A
single-channel CETO receiver along with a
BIRD actuator are used to move the
controls from pro-spin to recovery. All of
this is powered by a pair of watch batteries.
A spin model without a spin tunnel is
not much more than a display piece, so I
built my own vertical spin tunnel, which is
shown. The model is prerotated with a
launcher near the bottom of the chamber,
then the fan at the top is spun up to
establish the correct airflow. Then when the
steady spin is obtained, a signal is sent to
move the controls and the recovery is
measured.
By repeating this process several times
with different control combinations and a
variety of loading conditions, it is possible
to predict with reasonable accuracy how
easy or difficult it would be to recover the
full-scale machine from a spin.
Although I never was able to get any
contracts with private industries for spin
studies, I have learned a great deal, and, as
a bonus, the spin tunnel in the picture is
portable and is a big hit at air shows and
such, where the public has never seen this
sort of equipment.
There is still another side to owning a
wind tunnel: I can study other things as
well. Last season I put together a rig to run
propeller tests with a GWS 180 motor and
LiteStik gearbox. The chart, courtesy of
August 2003 99
Carl Miller, shows a comparison of some
hand-cut propellers, a GWS 9 x 7, and one
of Carl’s ARC propellers.
I was pleased to see that the propeller
design I have been using for a long time
will perform not only as well, but better
than a commercial propeller. The neat part
is that the design I am using has been in the
Free Flight literature for at least 60 years.
Go figure!
I better drift off now and charge up some
of those neat new Lithium-Polymer
batteries so I can get a flight or two in
tomorrow. Take care. MA
TIRED OF PAYING
$1.29 FOR 6 SCREWS?
Our 4-40x1/2 socket
caps sell for $4.35/100
for alloy steel, or
$6.65/100 stainless, or $7.50/50 aluminum.
For fair prices on sensible quantities of the fasteners
you need for model building, call, write or
fax for our free catalog!
Micro Fasteners 800-892-6917
24 Cokesbury Rd., Suite 2 908-236-8120
Lebanon, NJ 08833 fax 908-236-8721
e-mail: [email protected] Internet: http://microfasteners.com
08sig4.QXD 5.23.03 1:02 pm Page 99
Edition: Model Aviation - 2003/08
Page Numbers: 97,98,99
August 2003 97
HELLO MICRO FANS, and greetings from Central Virginia.
Spring has almost sprung in my area, and I have actually gotten some
decent flying days. Of course, being retired from a 7-4 job does
improve the situation when it comes to grabbing the moment.
This column will probably make it out before the big meet in
Waterford, Michigan (May 31-June 1), so I will look forward to
seeing some of you there. The Toledo show is just a few weeks away
as I write this, and I am looking forward to the show itself and the
flying session Saturday night at the Bowling Green State University
field house. Travel safely and get plenty of rest if you are coming; I
was wiped after last year’s session.
I have only made it to one indoor flying session in recent months,
and that was at the National Building Museum in Washington DC. If
you are within a reasonable distance of this great site, I highly
recommend that you come to the sessions. The DC Maxecuters club
organizes the flying, and it does a superb job. The Web site address to
keep up with this activity is www.his.com/~tschmitt/
comingattractions.html. There is plenty of other great stuff on this
Web site.
At the event there was a slightly enlarged Punkin II of my design
that Jay Stargel of Woodbine, Maryland, built. There were two of
these models in identical colors, but I missed the other builder’s name.
Both models were splendid fliers and well suited to this facility.
On a number of occasions I have been asked about a suitable model
choice for someone who is entering the field of micro-flying, indoors
or out. Shown is a Lockheed Electra profile model built from a DJ
Aerotech kit.
This company has a wide series of models (all profile) under the
Dave Robelen
M i c r o - F l y i n g
Route 4, Box 369, Farmville VA 23901; E-mail: [email protected]
Author’s Beechcraft Duchess serves as a spin-tunnel model.
This Lockheed Electra is one of DJ Aerotech’s Roadkill series.
Jay Stargel built this “slightly enlarged” Punkin II.
This Bumble Bee prototype micro UAV spans 8 inches.
08sig4.QXD 5.23.03 1:02 pm Page 97
98 MODEL AVIATION
name of the “Roadkill” series. Check www.djaerotech.com for the
complete line. I have seen everything from bombers to Cubs, with
World War II fighters in between.
Besides featuring some of the nicest laser-cut balsa I have seen,
these kits come complete with the required power unit(s) and
propeller(s). Many—probably most—are set up with aileron and
rudder control with some clever linkage. None of these models are
what I would call difficult to pilot, but the high-wing lightplanes are
a little more forgiving.
In addition to a great line of kits, Don Stackhouse and Joe Hahn
have a section on the DJ Aerotech Web site labeled “Ask J & D,”
which is downright informative. Tell ’em I sent you.
Several years ago when the micro-Unmanned Aerial Vehicle
(UAV) scene was emerging, there were some specifications for
small vehicles and a message that the Department of Defense would
be interested in small-business involvement.
Since the models don’t come much smaller than what I build, I
took an interest in seeing what could be done with the commercial
equipment of the times. I had a Cannon microsystem that was way
ahead of its time in features and several Cox .010 engines with
which to work.
The Bumble Bee (shown) has flown with at least 10 different
wings to look at airfoil and wingspan effects. The one in the picture
has an 8-inch wingspan, and even loaded with the relatively heavy
Cannon gear, it was decent to fly.
One interesting thing was the dihedral effect as I shortened the
wing. The shorter the span, the more pronounced the roll was with
the rudder. Besides being completely flat, this wing has a pair of
plastic fins on the bottom of the tips to further reduce this effect.
The Cox engine showed a great deal of potential as I developed a
carburetor that could be manually set, along with modified porting.
The result was adequate power to fly the relatively high wing
loadings and excellent fuel economy. Flights lasting 10 minutes
became commonplace with the little model with just the tank on the
back of the engine.
No group of government officials was knocking my door down
to spend money on this work, and I could not find anyone who
was interested. Even so, I learned quite a bit about micro air
Carl Miller’s chart shows a performance comparison of various propellers.
The author made this micro diesel prototype and parts.
The author built this spin tunnel which he
uses to conduct numerous tests.
vehicles along the way, so all was not lost.
Just to show that I was slow to give up, I decided to build a small
engine for future work. Shown is the tiny diesel with some spare
parts that I hacked out with my Hobby Lobby lathe and accessories.
It was becoming an exercise in futility as I began to go over the fuel
08sig4.QXD 5.23.03 1:02 pm Page 98
requirements and general lack of literature
on such tiny engines.
Meanwhile, the micromodel movement
had gotten underway and there was a
decent selection of small electric motors, so
I benched the little diesel as I moved into
electric-powered microflight.
Since I am doing a sort of show-andtell,
I might as well go a bit further. For a
number of years my work at NASA
involved testing models in wind tunnels,
and many of those were free-flying,
dynamically scaled aircraft.
Dynamically scaled? It means that not
only is the model pure in the scaled shape
of the full-scale machine, but the weight
and moments of inertia are scaled to the
prototype. The shape of the model is
reduced by a factor of, say, 10, but the
weight is reduced by the scale factor cubed
and the inertias are reduced by the factor to
the fifth power. It’s all very scientific.
One of the more specialized categories
is the spin-tunnel models. These miniatures
are launched into a rising airstream that
supports them as they spin, then the
controls are moved via radio control to
evaluate the potential recovery
characteristics. I was so taken with this
method of model testing that I decided to
try it at home.
One of my models—a Beechcraft
Duchess—is shown sitting on the scales.
The controls are held in the recovery
position with tiny springs while thin threads
pull them into the pro-spin position. A
single-channel CETO receiver along with a
BIRD actuator are used to move the
controls from pro-spin to recovery. All of
this is powered by a pair of watch batteries.
A spin model without a spin tunnel is
not much more than a display piece, so I
built my own vertical spin tunnel, which is
shown. The model is prerotated with a
launcher near the bottom of the chamber,
then the fan at the top is spun up to
establish the correct airflow. Then when the
steady spin is obtained, a signal is sent to
move the controls and the recovery is
measured.
By repeating this process several times
with different control combinations and a
variety of loading conditions, it is possible
to predict with reasonable accuracy how
easy or difficult it would be to recover the
full-scale machine from a spin.
Although I never was able to get any
contracts with private industries for spin
studies, I have learned a great deal, and, as
a bonus, the spin tunnel in the picture is
portable and is a big hit at air shows and
such, where the public has never seen this
sort of equipment.
There is still another side to owning a
wind tunnel: I can study other things as
well. Last season I put together a rig to run
propeller tests with a GWS 180 motor and
LiteStik gearbox. The chart, courtesy of
August 2003 99
Carl Miller, shows a comparison of some
hand-cut propellers, a GWS 9 x 7, and one
of Carl’s ARC propellers.
I was pleased to see that the propeller
design I have been using for a long time
will perform not only as well, but better
than a commercial propeller. The neat part
is that the design I am using has been in the
Free Flight literature for at least 60 years.
Go figure!
I better drift off now and charge up some
of those neat new Lithium-Polymer
batteries so I can get a flight or two in
tomorrow. Take care. MA
TIRED OF PAYING
$1.29 FOR 6 SCREWS?
Our 4-40x1/2 socket
caps sell for $4.35/100
for alloy steel, or
$6.65/100 stainless, or $7.50/50 aluminum.
For fair prices on sensible quantities of the fasteners
you need for model building, call, write or
fax for our free catalog!
Micro Fasteners 800-892-6917
24 Cokesbury Rd., Suite 2 908-236-8120
Lebanon, NJ 08833 fax 908-236-8721
e-mail: [email protected] Internet: http://microfasteners.com
08sig4.QXD 5.23.03 1:02 pm Page 99