R/C hobby has so many facets that sometimes it can become
overwhelming to take it all in. Recent advances in technology
have allowed many of us to enjoy the hobby without being skilled
in all aspects of it. I would not likely have become such
a model aircraft enthusiast if it were not for the ARF (Almost
Ready to Fly) design. Although I learned to repair before
I could fly, I am still only moderately skilled in most areas
of building, finishing, and detailing a model.
we can learn almost anything about R/C from the Web. We have
on-line communities, clubs, cliques, forums, marketing, and
sales. With the click of a mouse button, we can easily spend
our entire R/C budget for the season!
the past, R/C information was transferred through club members
or at trade shows and flying events. Many of the early hobbyists
were engineers, machinists, experimenters, and tinkerers that
had a real passion for model aviation. Some focused on the
engineering problems of the era like radio, servo, and engine
design while others were drawn to the replication of full
scale aircraft into smaller free-flight and R/C models. These
so-called modelers were highly skilled at making exact duplicates
of full size aircraft and could create a model from a set
of plans on paper or just a few photos. My friend, Paul Weigand
(AMA 76011), has been a modeler for over 50 years and has
taught me many things about aviation in the last decade. Paul
is a retired Automation Mechanic from Kodak and originally
learned many of his modeling skills from Don Steeb (AMA 2163).
Don was the founder of Don Steeb Inc. Precision Model Equipment
which manufactured Atlas Servos in the 1950's & 60's era
of R/C. He has been a mentor for many modelers in this hobby.
Even Don still comes to the local R/C shows after 52 years
and loves the advances he sees in the hobby.
this months issue of AMP'D, we'll see how electric flight
has improved the performance and appearance of several scale
aircraft. Although once originally flown using glow engines,
these beautifully detailed planes are now scale electric conversions.
Messerschmitt Me. 163 Komet
in 1995, Paul decided he would replicate the Messerschmitt
Me. 163 "Komet". The Internet back then was not
what it is today so you had to use specifications from books
or drawings to create your model. Photos were often hard to
find. Since the Komet had a small prop in the nose that was
actually used to power a generator, he decided that a slightly
larger prop for the glow engine would not detract from its
is shown on the right posing with his model in 1995 that was
originally built from Dennis Bryant plans. The plans came
from Bob Holman with a fiberglass fuselage.
the forefront of aeronautical production throughout the world,
the Messerschmitt Me. 163 Komet marked the beginning of a
new phase in air warfare. In fact, this revolutionary interceptor
was the first aircraft in the world to be powered by a rocket
engine, and, had it arrived in the WWII conflict a year earlier,
it would certainly have altered the balance between the adversaries.
This small and fast combat plane's first mission took place
on May 13th, 1944, Piloted by Wolfgang Spate, Commander of
test unit 16.
Early Me 163 A V4 prototype, 1941
Komet was the result of two great aeronautical technicians.
The first was Alexander Lippisch, who started to work on developing
all-wing gliders in 1926. Many of these concepts were used
by Jack Northrop in his series of flying wings. The second
was Helmuth Walter, who designed the first rocket engine fed
by combustible liquids. The Me. 163 was simply a glider which
used the revolutionary form of propulsion for only a few minutes
which included the time for take-off, ascent, attack, and
escape maneuvers. The aircraft was made of steel and aluminum
with fabric-covered control surfaces. The pilot, fuel, and
engine were all housed in the fuselage while the armament
was in the wing root.
Me 163 replica, 1994
Komet took off on a releasable undercarriage and landed on
an hydraulically cushioned, extendible, steel skid. With it's
16,000 ft./min. climb, it could intercept bomber formations
from above within two minutes. By comparison of the day, it
took an Me. 109 almost twenty minutes (or 10 times) to reach
the same altitude.
were several shortcomings to the design. The liquid fuel was
very dangerous and caused many accidents. Engine runtime was
only 5 minutes which gave it 2 minutes to seek out an enemy
after first reaching altitude. This made it very vulnerable
during its retreat as it made a long glide back to base.
volatile fuel could dissolve flesh in just seconds so the
pilot's flight suit, boots, underwear, and gloves were made
of a non-organic, nylon-like material.
shortcoming of the Komet was that its speed became a disadvantage
during attack due to the short range cannon that could only
be fired from 500 yards away from the target. At 450mph, the
pilot had only 2 to 3 seconds to aim and score a hit before
breaking off to avoid a collision.
test pilot, Heini Dettmar, recorded a level flight speed of
623mph (Mach .85) in 1941, which was 155mph above the world
speed record at the time. It was kept secret until the end
of the war.
flight characteristics of the Komet are still seen today with
each flight of the Space Shuttle. It is also a delta-shaped
flying wing that gets rocket-powered to altitude, and then
glides back to earth when its mission is completed.
For more historical information
on the Me. 163 Komet, read Schiffer Military History Volumes
20 and 57
Proof of Scale
1/6th scale Me. 163B Komet won the best sport scale at the CNYMAA
Symposium in 1996, when this show was big enough to use a NY
State Fair Grounds building.
entering a scale competition, a "Proof of Scale"
booklet is often used by the competitor to validate the specifications
of the model.
are comparisons of specs between the real prototype Komet
and the 1/6th scale model:
Wing root cord
Wing tip cord
------------------20 sq. inches
-------------------25.6 oz/sq ft
Scale Master Conversion
original model used a Super Tigre .61 ABC glow engine with
a MAC's tuned pipe and an 11x8 APC glow prop. The engine used
16oz of fuel. The cowl side was mostly removed for the cylinder
head to protrude. This non-scale appearance was greatly improved
from the conversion to electric power.
of the detail work was left unchanged, including the releasable
undercarriage that is ejected just after take-off.
new electric power system used the following components:
power level measured 1650 Watts at 68.7 amps which provided
12,300 RPMs and 203 w/lb.
off weight is 9 pounds with the 14oz gear so the flying weight
with an 8s 3850mAh pack is 8lbs 2oz. This was about 10 ounces
less than with the glow power system!
Test Flying the Komet
new electric-powered Komet was Ready-To-Fly at 8.25 lbs without
two decades after he first built the Komet, Paul does a final
inspection on the new electric-powered model. Not only does
the cowl look more scale but the Komet can now glide quietly
while the "generator" prop free spins in the air.
conceived in 1941, by the time the twin-engine Grumman F7F
Tigercat hit the streets, it never saw action in WWII. The
XF7F prototypes first flew in December 1943, and the first
production models were delivered to the Marines in April 1944.
Some F7F-3N and -3Ps did deploy to Okinawa during the very
end of the war but never tangled with the Japanese. It was
fast and powerful and would have been a formidable foe to
enemy aircraft. Although the F7F was too late for the "Big
One", it did see serious action some five years later
in Korea. (Ted Carlson/Flight Journal Magazine)
Model Products (or KMP) Tigercat was a beautiful fiberglass
ARF model of the Grumman F7F Tigercat. Although the kit came
with retracts, they were typically discarded due to their
weakness. Often the best part about these fiberglass KMP ARFs
was the shell itself. By combining this beautiful shell fuselage
and sheeted wings with some skilled craftsmanship and new
electric technology, the result can be a very special electric
by Paul Weigand and funded and flown by Ron McGrath, this
KMP F7F Tigercat is a beautiful scale replica of the Grumman
twin-engine piston fighter.
weak (for a 30lb model) stock KMP landing gear was replaced
with much stronger retracts from the giant scale specialist,
Giant. Owner, Darrel Tenny custom CNC's these retracts
for this specific model. They are a very strong, beautiful
looking, scale landing gear.
nose gear retract was modified to include a steering servo.
Tigercat conversion used two E-flight Power
160 Outrunner Motor's, two Castle
Creations HV-85 ESC's, and two sets of ThunderPower eXtreme
V2 5AH Lipo packs.
combined 10AH pack feeds both ESC's in parallel. On the advice
of Castle Creations Tech Support, Paul added 6 capacitors
for the long battery leads.
full throttle current draw was 140-amps for the whole system.
This provided 2465 watts from each motor when using 19x10
10-amp, 6-volt VR6010
High-Current Voltage Regulator installs between a model aircraft's
battery and receiver to deliver a constant 6V to the receiver
and servos. The regulator has a fail-safe On/Off switch and
is also sold under the Spektrum brand name. Ron used two of
these regulators for redundancy.
stock wing tube sockets were replaced with new fiberglass
tube sockets to use carbon fiber wing tubes. The stabilizer
halves were also made removable with servos mounted inside.
The Tigercat used two JR R922
9-channel receivers, one in the wing, and one in the fuse.
Each receiver had 3 satellites, for a total of 8 receivers,
and is fed by two separate 10-amp regulators. Talk about redundancy!
using a separate receiver system in the wing, it greatly reduces
the connections to the fuselage. All you really need is a
the power and air connections can be made after the wing is
bolted down. Custom
made motor mounts and Top Flite dummy engines were used. The
E-flite Power 160 outrunners were made to look like the F7F
prototype's gear boxes.
Ron McGrath and builder Paul Weigand carry the 30lb F7F Tigercat
to the flying field for testing.
Test Flying the F7F Tigercat
The All Up Weight (AUW) of the F7F Tigercat was 30lbs, 5ozs,
which gave a wing loading of 72 ounces/sq. ft. Although they
were not installed for the initial test flights, the idea
was to change to Mejzlik 18x10 3-bladed props for better scale
The video shows just how much power the F7F Tigercat had on
take-off. Ron never went above half-throttle except when performing
a loop. The rock solid retracts from Sierra Giant proved their
worth when landing the 30lb model.
we can learn almost anything about R/C from the Web. We
have on-line communities, clubs, cliques, forums, marketing,
and sales. Recent advances in technology have allowed many
of us to enjoy the hobby without being skilled in all aspects
of it. These advances in Lithium batteries, spread spectrum
radios, and brushless motors, when combined with ARF (Almost
Ready to Fly) designs, have created exciting new opportunities
in model aviation by once again expanding the scope of R/C
through electric flight.
this months issue of AMP'D, we saw how electric flight has
improved the performance and appearance of several scale
aircraft. By using both on-line and local community resources,
we can learn a great deal about our hobby. When combining
the building skills of the past with the latest technology,
older existing designs and new ARF models alike can all
become beautifully scaled electric conversions.
you fly electric, fly clean, fly quiet, and fly safe!
Special thanks for contributions
"Papa Jeff" Ring, Paul Weigand, Ron McGrath
section of AMP'D cover some of the questions that our
readers have sent in and I thought would be interesting
I'm writing you in regards to your Part
III article on the Hangar 9 33% Edge 540 E-Conversion.
I am currently working on a program which will
be characterizing several carbon epoxy props as
they relate to a particular aero body in a wind
tunnel. The best way to accurately control/characterize
the props are to mount them on an electric motor
(don't want fuel fumes in a wind tunnel). We have
decided to use the AXI Gold 5330/20 Double and
2 Jeti Advanced Plus 90 Opto Speed controllers
(same as in your article) for reasons relating
to required speed and power. I'm particularly
interested in the AXI 5330/20 Brushless Motor
connections as they relate to the electronic speed
controllers and the receiver.
I'm in a wind tunnel I will not be using batteries,
just a single rack mounted power supply. I will
not be driving/controlling any servos for ailerons,
rudder and elevators...only the throttle. Your schematic
shows a Discharge Protection Module (DPM) in between
the Battery Packs and each ESC. Is the DPM there
to protect the batteries or the ESC? Since I'm running
the motors from a power supply and not from batteries
do you think I need the DPMs? The second question...did
you use a simple "Y" connection between
the receiver and the two ESCs or is there more to
it than that.
in advance for your help.
DPMs are there to protect the batteries so you
won't need them. The concept of DPMs was not very
popular in the market even though it protected
your expensive batteries. The cost, weight, and
complexity was too much for non-engineering type
simple Y-harness between the two ESC control lines
and the receiver throttle channel is all you need.
Remember to extend the three motor wires, if needed,
and keep the wires from the ESC to your power
supply 18" or less. This will allow most
any ESC to compensate for motor inductance changes
and prevent a blowout. The wire length between
the motor and ESC can be very long (like up to
10'). If you need to run power supply wires longer
than 18" then add some 220uF-330uF capacitors
(or similar) with a proper voltage rating using
the technique shown on the Schulze
Tigre has been well known and liked for their glow
engines for many years. They have now released a brand
new line of electric power systems designed to provide
modelers with that same dependable quality at a very
only is this new line of electric power products an
excellent value, they come with a 100% quality guarantee
that is backed by the full support and service that
modelers have come to expect from Great Planes.
the items are matched to work together and there is
NO SOLDERING REQUIRED! The 3-cell Lithium Polymers packs
come with a Great Planes ElectriFly compatible charge
connector and a separate discharge connector that mate
to the Electronic Speed Controllers (ESCs).