Micro-Flying - 2003/02

GREETINGS FROM Central Virginia.
This month I have several items of interest
to write about, including new products and
a new competition.
I have applied for a sanction to hold the
“Radio Control [RC] Indoor Nationals” at
the Lakehurst dirigible hangar at Lakehurst
Naval Air Station in Lakehurst, New
Jersey. The paperwork is still “in the mill”
as of this writing, but there is little reason
to anticipate problems. The proposed dates
are June 21-22, 2003, or the third weekend
in June.
Events will include Scale, aerobatics,
pylon racing, duration, cargo, and possibly
others. The various event rules are still
being “massaged” at this writing, but some
basic items have been established. It is very
important that all models flown in the
Lakehurst facility have a weight limit of 10
ounces gross; this applies to all events.
The Scale event will follow the rules
established for Sport Scale in the rule book,
with the necessary adjustments for indoor
operation. A suitable indoor Scale model
would be my Vagabond (shown). With a
wingspan of 34 inches and an area of 200
square inches, the weight is 4 ounces with a
Ni-Cd battery and could be considerably
less with a Lithium-Polymer battery.
The drive is a WES-Technik 7.5:1 DC5-
2.4 motor spinning an 8 x 4 propeller, and
the radio control is a GWS R4P receiver
with two WES-Technik 3.0 servos and a
Pixie Light ESC. Built like a Free Flight
Rubber model, it is covered with RA
Microlite plastic film. Watch for it in RC
MicroFlight.
The aerobatic event is designed to
follow the rules established for the outdoor
Pattern event using the Sportsman pattern,
February 2003 65
Dave Robelen
M i c r o - F l y i n g
Route 4, Box 369, Farmville VA 23901; E-mail: [email protected]
The author’s Vagabond weighs 4 ounces and has a 34-inch
wingspan.
The Turbo Sport model has a transmitter from the Turbo Twin blimp control system.
The author’s Megatech X-EC Diversion uses motor thrust control.
with model specifications modified for
indoor flying. The proposed specifications
include a maximum voltage of 9.6 to the
motor(s) or a maximum of 30 watts static.
The maximum weight would be 6 ounces.
One possibility would be a model like my
Flap Jack (published in RC MicroFlight).
The pylon racing rules are still being
refined at this point, but previous
experience points to a limit of a six-cell 120
mAh Ni-Cd battery and a single-surface,
undercambered wing. The most popular
drive motors come from the GWS family.
All of the event rules will be firmed up by
the time this column reaches print.
The endurance category is the AMA
rule-book event for Indoor Electric
Duration. The cargo-event rules are still
under development, but the concept will
involve a scoring system that is a ratio of
the airplane weight to the cargo weight.
The flight requirements will include a
takeoff and landing, along with circling
flight that could fit in a gymnasium.
Rob Romash ([856] 985-6849) is
president of the local club and a good
source for lodging suggestions. He pointed
out to me that motels in the immediate
02sig3.QXD 11.21.02 1:46 pm Page 65
neighborhood of Lakehurst will have higher
rates because of their proximity to a resort
area, and selecting lodging a few miles
inland could result in substantial savings.
A variety of vendors carry suitable kits
and supplies. The following list is by no
means complete but includes firms with
which I have had dealings: Sky Hooks and
Rigging (kits, supplies), (905) 257-2101,
Web site: www.microrc.com; Todd’s
Models (kits, supplies), (425) 888-8580 (5
p.m.-8 p.m. Monday-Thursday, Pacific
time), Web site: www.toddsmodels.com/;
David Lewis (kits, supplies), (407) 856-
6245, Web site: www.homefly.com/.
Sig Manufacturing also carries a line of
indoor Scale kits. My apologies to all those
whom I have left out. For additional
sources, check the vendor links at
www.rcmicroflight.com.
Put this date on your calendar, and bring
some models looking for a good time.
Since I last wrote about the new ultra
micro 1.5-gram servo, I have had an
opportunity to work with one of the
preproduction samples. The source of these
little gems is Dave Burley, 1801 N.W.
Johnson Rd., Portland OR 07281; Tel.:
(503) 621-6928. I installed the unit in my
Punkin II model. A close-up of this little
jewel can be seen in the cabin and the tailmounted
sensor.
As of this writing, I have flown with this
servo controlling the rudder in my little
biplane with a large throw, and it continues
to be at least as smooth as any servo
employing conventional feedback. The
feedback on the Burley unit involves a tiny
magnet mounted on the control surface
moving next to a hall effect sensor. With no
physical contact, this feedback system will
really shine in the lifespan department.
Operating on 4.8 volts, the servo has an
impressive force and speed. It would
compare favorably with other linear servos
on the market. It is likely that John Worth
(of Cloud 9 Micro RC) will be the jobber
for these little gems. If you are looking for
The Flap Jack II could be used in the indoor aerobatics event.
The 1.5-gram servo mounted in the Punkin II’s cabin.
Feedback sensor for tiny servo mounted on Punkin II.
The author’s Punkin II RC model has the 1.5-gram servo.
66 MODEL AVIATION
02sig3.QXD 11.21.02 1:47 pm Page 66
the smallest in motor-driven servos, this
one could meet your needs.
In 1996 I developed a model design called
the Turbo Sport (shown), which was
published in Model Aviation in mid-1996,
in response to a design contest for model
airplanes using the inexpensive
(approximately $25) blimp control system
called the Turbo Twin. This neat little
system included all the RC controls and a
pair of drive motors in a plastic strap-on
package for small, lighter-than-air craft.
Removing the receiver and motors
from the plastic housing provided a
compact and light control system on 27
MHz. The cute little transmitter is
powered with a single 9.0-volt battery.
When the receiver antenna was left to
dangle straight down from the model, the
range was adequate for outdoor flying.
There are limitations, such as the
output transistors which kept the current to
the motors to a modest value, but this also
served to add to the flight time. I was able
to fly for at least five minutes with a threecell
50 mAh Ni-Cd battery. With the new
Lithium-Polymer cells, this time could be
extended considerably without a weight
penalty. Adding gearing to the motors for
larger, more efficient propellers is also a
desirable enhancement.
There are probably quite a few of these
Turbo Twin units on shelves or still at
dealers. Why not pick one up and try a
different dimension of control?
Did I hear you ask what brought up the
subject of the Turbo Twin? Between trade
shows, shopping at the toy department at
large stores, and following the magazine
reviews, it seems that I have given the
industry the concept of using motor-thrust
control as a control scheme. The Megatech
X-EC Diversion in the photo is an
example of the commercial offerings. It
worked quite well for me, and it seems to
be gaining popularity with the industry.
Give it a try.
One of the most important items in all of
our electric-powered models is the battery
supply, and some good news is coming
along; the Lithium-Polymer battery
developed for cell phones has proven to be
extremely well suited to our needs with
the smaller models. With a considerably
greater capacity for the weight than Ni-
Cds or NiMH cells, Lithium-Polymer cells
are proving to be rugged and easy to use.
The best part is that there seems to be a
“price war” among several suppliers with
us customers as the beneficiaries. FMA
Direct is the exclusive dealer for the
Kokum brand, and a variety of other
dealers handle different brands. Keep an
eye on the ads for some great deals.
Considering that this is supposed to be
“your” column, I sure could use some
input on your projects, techniques, etc.
Come on and share with us.
You all take care. MA