Letters to the Editor
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. Reprints of the originals are still available.
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 Free Flight Duration column (pages 134–135) presents a description of a neat little battery box for starting 1/2A engines. I believe the description is in error.
The writer states: “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, 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 holders 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 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 at 14,000 rpm.
Compared to the RCV58 (10,000 rpm), my HP VT49 would swing the same 12 x 6 Master Airscrew prop 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 believe, were offset by the fixed timing of the glow ignition and 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 reproduced in the U.S.
Lee Eckert Buffalo Grove, Illinois
#### Response — Joe Wagner
Lee Eckert is correct in stating that four-stroke 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 WWII.
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 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 full-scale 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 at 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 each other.
- 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
(Continued on page 102)
Transcribed from original scans by AI. Minor OCR errors may remain.
