Letters to the Editor
All letters will be carefully considered, those of general interest used. Send to Model Aviation, 815 15th St., N.W., Washington, D.C. 20005.
Quickie
An interesting article, but of no possible use to a model builder. It belongs in Air Progress or similar. If it showed the C.G. I could "fake it." If you follow up with an R.C. construction article and make plans available, I'll happily forgive you for the overly verbose report on the subject aircraft.
Never could understand why the canard concept had not been pursued. My first (glider) "Aircraft" (about 1926) was made from whittled shingles and slices of automobile inner tubes to hold the wings in place. Flown as a canard it flew very well. With the wing forward, nose weight (plenty) had to be added and performance suffered.
If I have offended thee — it is intentional. Sorry!
Walter Wirths Harrington Park, NJ
Better late than never — here's that C.G. position. People seem to be building models of the Quickie. A quarter-scale R/C version at the local field spans only 4 1/4 ft., yet has a 60 engine! See Meuser this month for a highly interesting canard item — Joyce's record cargo model with two .010's. Canards were popular about 45 years ago but a common fault at the time was a tendency to meander all over the landscape — troublesome with an indoor model.
Book Wanted
If you can give me any assistance in locating a copy of "They Fought for the Sky," by Quinten Reynolds, Jr., it would be greatly appreciated. I have been looking for a copy for years without any luck.
B. L. Thomas Valco 10055 N. Wayne Ave. P.O. Box 15177 Cincinnati, OH 45215
Bigger is Safer?
I am a member of the Southern Tier Aero Radio Society, Inc. (S.T.A.R.S.) and recently have become involved in large size R/C models. As most aspects of involvement in this larger size model are new or novel, I am often asked questions pertaining to them. I am a Mechanical Engineer by profession, and have been somewhat amazed as to the misconceptions that are held by many in regards to model aircraft. The following graph and explanation may be of interest to modelers and others in this regard.
Models are only as safe as the flyers that fly them. There is no substitute for safe practices in regards to any R/C model. The large models generally exhibit better than average flying ability. Many articles have been written on this, and my own experiences agree with them.
For the most part, the large models have come about by the scale modelers who wish to fly a scale model at a scale-like speed. The smaller size scale ship must fly faster-than-scale speed to attain stable operation. I am sure an aeronautical engineer can explain this but general observation can prove this point. Anyone who has witnessed the flight of a large model can attest to this. Large models generally fly at a much lower speed than current popular R/C models.
In explaining the safety aspect of any model, we must consider two aspects of a model: 1) the ability to control the craft, and 2) the damage that can be expected if an accident occurs.
The purpose of this letter is an explanation of the second aspect, as the first has often been mentioned and I feel it is generally understood and accepted.
The second aspect is basically the energy of a moving body. This energy is called kinetic energy and is a function of its weight and its speed. Damage occurs when this energy is transmitted from the moving body to another body, be it ground, person, or thing. The mathematical equation for this energy is E = 1/2 MV^2; E = energy in foot pounds; M = mass, which is weight in pounds divided by the gravitational constant 32.2, and V = velocity in feet per second. Putting this equation into a more meaningful form, we can say: KE = WV^2. That is, kinetic energy is proportional to weight, in pounds, times velocity, in miles per hour squared. The exact energy can then be compared to an existing value.
It should also be pointed out that, though large models often use larger engines with regard to displacement, the horsepower developed is generally less than that produced by new high-speed Schnuerle-ported engines because the large model generally requires a large propeller and rpm at the shaft is purposely reduced to accommodate the propeller. Sometimes this reduction is accomplished by the use of a geared engine. In this way a larger engine develops lower rpm and more torque.
Letters to the Editor
Most modelers are familiar with. The chart shows the relative energy levels of several common types of aircraft. A five pound (racer), an eight pound (pattern) ship and other large models; comparison of energy levels indicate the large model is well within the energy level of these current types.
It should also be pointed out that even though the large models often use a larger engine in regards to displacement, the horsepower developed is generally less than that produced by the new high speed Schnuerle-ported engines. This is because the large model generally requires a large propeller and the rpm of the shaft is purposely reduced to accommodate it. A geared engine is one way to accomplish this. other.
It can also be pointed out that the speed of a model is proportional to the cube root of power and wing area so that for a given horsepower, the speed of a large model must be slower than for a smaller model. It is therefore safer to use higher horsepower in flying a larger model than it is to make a smaller model go faster.
The formula for this is: V = K √ P/A
where V equals velocity, K equals a constant depending on type of aircraft, P equals horsepower, and A equals wing area.
The purpose of this letter is to point out that most large models do not generate any more energy than current popular types, and therefore do not represent any more of a hazard.
Robert Dunn Olean, NY
How Fast?
In your February 1978 "For Openers" you point out that the new RC glider speed record exceeds the power speed record by nearly 30 mph. This is an amazing difference and deserves an explanation but the reason attributed... is ridiculous. "The airplane outruns the engine." If the prop "disk" actually acts as a brake then an airplane in a power drive should increase its speed if it cut the engine and feathered the prop!
An engine turning a 13" pitch prop at 20,000 rpm would not start to brake the airplane until the speed exceeds 246 mph. If a prop is braking then it simply is of too low a pitch.
Kit Bays Downers Grove, IL
We checked a qualified person who gives the opinion that the 246 mph figure mentioned in Bays' letter is reasonable. Incidentally, the statement that "The airplane outruns the engine" was ours (we stand by it), and was only an editorial comment added after mention of a conversation with Maynard Hill. The words were not Maynard's. We note that Kit questions that the prop disc would behave as a brake, and that the plane would go faster if the prop could be feathered. But we know of a flyer saying after an RC Power Speed attempt on the world record, that he wished he could rid of the engine! And, too, we note Kit used these words: "...would not start to brake . . ." If we concede that the prop is of too low a pitch, we have to ask if the engine would turn a higher pitch at a necessary rpm—or is a more powerful higher rpm engine (than the one used) required. The question is too complex for a blithe answer. Only a few people in the world may know the answer, and are familiar with the many related factors, including, the airplane itself.
Backyard Circus
I enjoyed the article by Leo Vartanian on his indoor electric very much—I have also used the Monogram unit with good results in a Super Star with Ace R/O. With two "AA" nicads it could do five minutes and about 400' altitude, very satisfying performer.
I have been flying a small field plane I designed, and I'm sending you some pictures of it. It is setting on a teacup in the Kodak photos, which gives you an idea of its size. It is 24" span, 12 oz. with an Astro 020 and Ace Baby R/O. I have also flown it with the Cannon Super Mini two channel quite successfully. The really outstanding feature of the Electro Flea is its rapid climb—I designed and built it to fly out of a vacant lot next to where I lived, and it does that beautifully. It gets above the power lines, trees, roof tops, etc. in less than a minute, and gets up to about 500', for five minute flights. Once the motor
Letters to the Editor
drops out (batteries discharged) it comes in like it had spoilers, steep steady descent, easy to get right back into that tight little lot it climbed out of! It also is not bothered by wind, there is no problem even in wind up to 15 mph. However, it isn't a particularly fast flier, about 25-30 mph, beginners can fly it.
Mitch Poling Seattle, WA
Smallest CL Plane
I am trying to locate plans to the smallest recorded control line plane ever flown. Could you please tell me where I would have to send to get such information. The reason I am doing this is because my friend and I are going to try to fly the smallest or smaller. I would appreciate it if you could help.
Randy Patterson Roscommon, MI
We don't think anyone knows for sure who built the smallest CL model, but you'll find something interesting on page 61 of the April issue of Model Aviation. If you keep it light and use a wider chord for more area, you probably could make it smaller—perhaps keep clipping the wing a tiny bit at a time, you will arrive at the smallest thing that will fly. But don't fall into the old trap that smaller wings must make a plane faster. Speed fliers went that way many years ago, learning that a ship which had to assume an angle of attack to generate enough lift to remain airborne, just flew slower. There must be enough area for the thing to "get on the step."
Help Wanted
I am in the process of building my first radio control model and would like to get in touch with any local clubs that there may be in the area south and west of the city of Boston. I know that there are clubs in Framingham and in Bridgewater, Massachusetts. The one in Framingham is called, I believe, the Charles River Club. However, I do not know the name of the contact person.
If you could send me this information or give this letter to someone who could I would appreciate it very much. Before closing I must say that Model Aviation is a very superior publication and you have every right to be proud of it. The April issue must qualify as one of the best issues of any magazine in the field ever published. As a member of AMA I appreciate your skilled efforts on behalf of myself and all the other members.
Fred E. Bellows, Jr. 165 N. Main St. Sharon, MA 02067
We have included Mr. Bellows' full address so some helpful reader may write him. No such club appears in the AMA club roster.
Transcribed from original scans by AI. Minor OCR errors may remain.
