Letters to the Editor - 2004/03

Correction
The caption on the bottom of page 62 in
the January 2004 Model Aviation reads that
Andy Kunz of FlyingHobbies.com built the
warbird-style Python. Actually, Edgardo
Catalano built that model.
Our apologies for the error.
—MA staff
Paper Models
In the January 2004 issue of Model
Aviation a letter from Jim Moss [on page 9]
writes about the paper airplanes from the ’40s
using a penny in the nose. These paper
airplanes were offered by Wheaties and were
called Jack Armstrong packets. There are still
available reprints of the originals.
A few months ago I bought a P-51,
Fw 190, P-39 Airacobra, and a
Grumman Wildcat. They are available from
Paper Models International at
www.papermodels.net/. I believe Kellogg’s
PEP cereal also offered some since I
remember eating a lot of cereal I hated just to
get the models.
Ted Stockert
Bismarck, North Dakota
Uncrossing the Wires
In the January 2004 edition of Model
Aviation, the column on Free Flight Duration
presents (pages 134 and 135) a description of
a neat little battery box for starting 1⁄2A
engines. I believe the description is in error.
The writer states that: “Norm and Tom
sized the box to fit around a RadioShack
battery holder that accepts two D cells.” The
RadioShack battery holders that accept two
cells place the cells in series configuration,
thus delivering 3.0 volts. This voltage will
burn out or shorten the life of a glow plug.
The correct description, I believe, should
have been “Norm and Tom sized the box to fit
around two RadioShack battery holders that
each hold a D cell; the two cells were wired in
a parallel configuration to provide 1.5 volts.”
The picture of the little box on page 134
seems to confirm that there are two boxes
with two red wires attached to one jack and
the two black wires routed through the switch
to the other jack, thus creating a parallel
configuration of the batteries and a potential
of 1.5 volts across the jacks.
This is contrary to the writer’s description
of the wiring: “One wire goes from one of the
battery-box connections to a jack. Another
wire goes from the other battery-box
connection to the rocker switch. From there, a
third wire connects the switch to the second
jack.”
Most of us old modeling hacks who began
the hobby 50 years or more ago will know
how to connect two batteries in parallel to still
get 1.5 volts. However, some youngsters on
tight budgets might burn out expensive glow
plugs if they follow the description as
presented.
Model Aviation is a great magazine. I can
hardly wait for each new issue to arrive. My
favorite parts are “Focal Point,” which
presents four pages of pictures of models and
builders, and articles that deal with the basics
of model construction and radio control.
Don Bills
Beaverton, Oregon
Not New Technology?
I am writing to call attention to an
oversight in the January 2004 Engine Shop
column by Joe Wagner. Joe did a nice job
describing the RCV58 rotary valve engine.
However, Joe’s article, as well as another
recent magazine review of the RCV, treat this
engine as if the technology employed is
totally new and novel. It is not.
The RCV58 cleverly integrates a rotary
valve into the rotating cylinder, but the basics
of this, in model engines, were established
over 20 years ago in the HP VT21 and VT49.
Clarence Lee reviewed these engines circa
1983/84.
Reprints of those reviews appear in his
1984 publication on four-stroke model
engines. The HP VTs, though quite heavy for
their displacement (the VT49 weighed
approximately 21 or 22 ounces as I recall),
used a rotating valve in the head, driven by
the crankshaft via a vertical shaft at the rear of
the engine.
As Joe mentioned for the RCV58, there
were no reciprocating parts in the HP VT
series either, other than the piston/connecting
rod assembly. That is not to say that RCV has
not improved the species, made it more
compact, etc. However, it did not invent the
species.
I owned a VT49 about four years ago and
found it to be a smooth-running, but not
especially powerful, engine. From my dyno
testing, mine developed its torque peak at
higher rpm than traditional four-stroke
engines, at approximately 11,000 rpm. Peak
horsepower was approximately 14,000 rpm.
Compared to the RCV58 (10,000 rpm),
my HP VT49 would swing the same 12 x 6
Master Airscrew propeller at 9,300 rpm. It
was happier at 11,600 with an 11 x 6 Master
Airscrew and would swing a 10 x 6 at 13,100.
This was on 10% nitro, 20% oil (50/50
castor/synthetic).
The advantages of a rotary valve design to
run at higher rpm, I believed, were offset by
the fixed timing of the glow ignition and
intake and exhaust ports, which seem to limit
the overall efficiency and power output. The
glow plug is only exposed to the mixture for a
brief duration as the port rotates past the plug.
Those engines, originally produced by HP
in Austria, are presently still available from
RJL and are produced in the US.
Lee Eckert
Buffalo Grove, Illinois
Lee Eckert is correct in stating that fourstroke
engines with rotary valves are far from
new. The concept goes back a long way. For
example, rotary sleeve valve engines powered
thousands of British combat airplanes in WW
II.
However, the RCV design is indeed an
innovation. No model engine quite like it has
been manufactured before. The HP VT types
use a separate shaft-driven rotary valve in the
head. RCVs have only one more moving part
than a two-stroke engine: the rotating sleeve
which performs all the “valving” functions.
Joe Wagner
Ozark, Alabama
Tape’s a Winner
I was asked to give a talk on RC modeling
to a local ham radio club. Richard Hanson
(vice president of District X) gave me a VCR
tape to show the group. Not having an
opportunity to preview the tape, I hoped it
wasn’t a 25-minute commercial for AMA.
I am not sure who was more pleasantly
surprised, me or the audience. They could not
believe that they were looking at model
airplanes in the scale sequence and not fullscale
aircraft. They were also amazed at the
Combat and Control Line sequences. I am
sure it brought back fond memories to many
ex-model enthusiasts in the crowd.
The tape is titled All Because of Model
Airplanes. I would recommend it to all AMA
clubs to show to new members and
membership drives—it’s a winner.
Raymond P. Wisniewski
Scottsdale, Arizona
Industry Standardization
Radio control aviation has made great
strides both technically and commercially
during, say, the last 20 years. Unfortunately,
the game lacks one basic feature characteristic
of a mature industry: standardization. There
are many examples of non-standard features.
A few follow.
Radio equipment where connectors from
various manufacturers will not play nicely
with others. Servo output shaft configurations
differ to the point where servo arms from one
manufacturer will not properly mate with
servo output shafts of another.
Mounting bolt drill patterns from engines
of the same size differ to the point where,
more often than not, one cannot change
Model Aviation, 5161 E. Memorial Dr., Muncie IN 47302
Letters to the Editor
March 2004 9
Continued on page 102