Free Flight: Duration
Bob Meuser
SINGING of swans. My May column was supposed to have been my last. Then I got this frantic call from Associate Editor Ross McMullen asking where the heck is my column for the July issue? Anyhow, this is it. Seventeen years, almost continuously, counting Model Aviation's precursor American Aircraft Modeler.
Chuck Broadhurst got me into it. I had four days to put that first column together from a standing start. It even had an inked perspective cutaway drawing in it.
It has been hard work, fun, frustration, and satisfaction all rolled up into one, big, loppy-sided ball of wax. I do greatly appreciate the help I've gotten from a great many of you in the way of contributions of newsletters, photographs, and material of various sorts. And I'm grateful for the opportunity to have met many of you through correspondence, if not on the flying field.
But I seem to have more to do, less time to do it in, and a lower production rate than in previous years. And so something must go; this is my swan song. Nothing is forever.
Gyros
Gyros. Some five years ago I was all hot on setting all available indoor and outdoor autogyro records. I did set one or two of the outdoor ones, got done in on another via a fluke of the rules, and didn't quite get around to the indoor part of the caper.
The lift was provided by two side-by-side rigid rotors. The concept worked nicely. Flight duration—still air—was typically just under two minutes, about half that of a similar fixed-wing model. I figured that wasn't too bad, considering the inherent inefficiencies of a gyro.
However, it recently occurred to me that I might have been way off base. A fixed rotor, such as I had been using (nothing teeters or cones, just freewheels like windmills) has to be the most inefficient device the mind of man could invent. The blade on the side that's moving forward does all the lifting; the blade on the other side might be doing worse than nothing.
The obvious (it only took me five years to figure it out, so it must be obvious) solution is to teeter the rotors, as is done on most small, man-carrying gyros—Benson and the like. There are two blades on the rotor, and they are rigidly connected to each other; not hinged to the hub as with the Cierva-type unit. The two-blade unit is hinged about a chordwise axis. The forward-moving blade, then, teeters up until the backward-moving blade is moving downward so fast that it generates an equal amount of lift. Since both blades are generating equal amounts of lift, the setup should be a lot more efficient despite the fact that the two sides of the rotor are going through the air at different velocities.
Crystal clear, eh?
Binoculars
Binoculars. The NFFS Digest recently ran a story by Hermann Anderson, which originally appeared in the Phoenix MAC newsletter. If you are thinking of getting a pair of binocs, you might wish to check out Consumer Reports at your library, too. A couple of years ago they did an in-depth report on binoculars.
Walter Erbach suggests checking out the 3.5 x 50 field glasses (they are not true prism binoculars) at K-Mart stores. The regular price is $10 to $12, but he found them on sale for $9. At that price, you can probably afford to leave a pair in the glove compartment or model flying box without worrying a lot about them getting swiped. You might not be satisfied with the narrow field of view, however.
Safety tips
Safety tips from Terry Thorkildsen in The Satellite. If you are using a commercial radial mount for a 1/2A engine—the kind that goes between the crankcase and backplate—and you experience a crash, best check the mount thoroughly for cracks. Terry has had several come apart with the engine running many flights later following a crash. Also, if you don't use the spring starter on the smaller Cox engines, remove it from the engine. Terry got a nasty cut from one when flip-starting the engine.
Dethermalizers on full-size aircraft
Dethermalizers on full-size aircraft. Some time back, I mentioned that something close to that was, in fact, being explored. Ed Whitten recently sent me a clipping from a 1983 issue of the New York Times showing a Schweizer 1-36 sailplane that had been equipped with a pop-up tail dethermalizer by Dale Reed. Reed was also contemplating using the device on an aircraft that was to have been flown in the thin atmosphere of Mars, a project that is now in limbo. The article mentions the application to free flight models.
Reed, who was on the early Space Shuttle program, is a modeler and usually builds flying models of the concepts he is working on, as he did with the proposed wingless, lifting-body concept.
Benton gearboxes
Those Benton gearboxes come on the noses of some all-foam, almost-ready-to-fly rubber-power models—and some stick-and-tissue wonders to boot—and in two sizes, both with a max gear-up (prop revs to motor revs) of 21:1. The gearboxes can be bought separately, by mail, from AHC if not at your local model shoppe.
Using them on the noses of small models—say, up to 30-in. span—is straightforward; that's what they were intended for. But how about using such a device as the "back gears" in order to put two rubber motors in series, so to speak? The 2:1 ratio boggles the mind a little, but it should all work out.
Replace the prop shaft with a motor hook coming out the "back" of the unit, which ultimately becomes the front. Hook that to the motor that goes directly to the prop. Use a fatter motor on the other hook, the "slow" side. Crystal clear again, eh? I hope not! You think I'm going to tell you all of my terrific ideas? Try it; you'll hate me!
Making fiberglass cloth behave
If you have had trouble with the edges of the cloth unraveling and have had difficulty cutting it to the shape you want, you might try this tip by Walt Rozelle which appeared in Plane Talk. Walt got the idea from Rex Hinson of Florida.
Spread out some newspapers, some waxed paper on top, and finally the glass cloth over that. Hold down the edges with weights of some sort, and shuffle it around until the cloth is smooth and square. Then spray the cloth with nitrate dope. When it dries, you can roll it up, draw outlines on it with a felt-tip pen, or cut it freehand or with a straightedge.
The cloth can be applied to pre-doped surfaces by using thinner, just as you would when covering with tissue. I imagine the scheme would work with silk, too, which is almost as miserable to work with as fiberglass.
Skywrap, revisited
Since my previous column, John Oldenkamp has put his act together and is now President, General Manager, and Chief Shipping Clerk of the Skywrap Division of Skybox Enterprises (or something like that). His one-sheet brochures tell all about how to use the stuff; hints on building structures to be covered with it; adhesives; coloring; and so forth.
At only 0.64 grams per square foot, it is light enough for covering about anything you can imagine and tough enough to use for covering big, outdoor rubber-power models, too. Whether it would stand up on a 1/2A gas model, I'm not sure—but I bet it would be OK on the tips and tailfeathers.
John also suggests using it as a "finish coat" on things like rolled-tube fuselages, HL glider wings, props, and the like. Hmmm. How about inside of a rolled tube before it is rolled?
Suitable adhesives range from CR/5C to white glue to spray adhesives. Coloring can be done with Pactra "Namel" spray before or after covering. John says that Mylar-film drafting ink works, too. I've used it a little, and it seems to accept waterproof felt markers OK, giving a translucent (albeit somewhat anemic) effect.
That opens the possibility of using a technique I've tried on tissue and condenser paper. Saw the end off the felt marker and remove the soggy entrails. Soak them in water thinner, squeeze the vital body juices into a container, then spray it on. It should be lighter than enamel. Masking can be done using wet newspapers; I sure wouldn't try masking tape unless it is used in such a way that only a narrow strip of tape is stuck to the film—you have to mask the masking tape!
Build light but stiff structures—lots of drag—as the stuff adds little stiffness. The possibilities are endless.
- Prices: $3.50 for five 20 x 22-in. sheets; $7.50 for 12; $14 for 30—postpaid.
- Add 6% tax for California residents.
- Order from Skybox, 3331 Adams Ave., San Diego, CA 92116.
Book report: Free Flight Experts' Forum
This is a collection of articles presented at this year's Model Engineer Exhibition in England and is published by the Society of Model Aeronautical Engineers (England's AMA). Proceeds from sales of the publication go to fund the British Indoor & Outdoor FF teams flying in Europe and World Championships. That's important: it isn't the same in England as it is here. There, they are expected to pay their own way. Perhaps sales of these reports will be a small step, at least, toward getting able modelers who don't happen to be specially well-heeled onto the British teams. Free Flight cannot be allowed to become a rich-man's sport, especially on the international level.
Fortunately, British modelers are better modelers than they are bookbinders, for my review copy lacked pages one through 16—and had enough pages 17 and 18 to supply an army. I'm certain they'll get that sorted out. So, I missed the first two articles; one on the application of Larrabee's prop-design methods to free flight props, and another about etherless fuels for diesel engines.
Martyn Presnell, well-known to readers of the NFFS Symposium Reports, applies the wind-tunnel data on model-aircraft airfoils to the design of A-1 and A-2 towline gliders, Wakefield, and Coupe d'Hiver rubber-powered models. His curves indicate optimum aspect ratios of about 25 to 30 for A-1 gliders, 15 to 20 for A-2s, 18 to 22 for Wakefields, and eight to 12 for Coupes. The least that can be said about his presentation is that it has a touch of real class!
John O'Donnell, Britain's "Mr. Free Flight" for many decades, tells all about the pros and cons of covering materials (Mylar films, Melinex, in England), plus gives a lot of useful data about using the stuff.
B. J. Hunt presents non-copy-protected microcomputer programs for predicting or analyzing the performance of indoor models. His results are enlightening and seem to square with experience, which isn't a bad thing to say about any theory. By using his programs one could do a lot of "building" and "flying" on paper before committing oneself to a lot of actual building and the foggy, foggy dew. He also presents plans for one of those strange, star-shaped, sausage-wing models which, if built to the stated dimensions, is supposed to be down-safe rather than really competitive.
S. R. Philpott presents a nifty expose on the hotting-up of CO2 motors and applying them to the engine-room chores of a free flight model.
C. H. Edge presents a whole bunch of interesting and useful material on the application of "composite" materials—fiberglass, carbon, boron, etc.—to free flight models; their potentials; their limitations.
Stafford Screen, well-known to FAI Power fliers, presents an incisive, brief analysis of the development of the class, including his most recent experiences and developments.
Mike Farthing, whose name pops up in every British model mail I see, presents an enlightening discussion of the relationships between forces, structural design, and the occasional failure of the latter under the influence of the former.
If the publication of such things were a competitive activity, it would seem as if those blokes were trying to give us in the colonies a run for our money. The price, however, isn't all that great — £5.50 airmail or £4.75 surface, which at today's exchange rate amounts to $8.36 and $7.22 in real money, respectively.
The books are 8½ x 12 inches, 75 pages, and have soft covers. You can get a check made out in British funny-money from your bank. Make said checks payable to SMAE F/F Team Travel Fund and send to Martin Dilly, 20 Links Road, West Wickham, Kent BR4 0QW, England.
And oh, by the way, while I have you on the line... There was also a 1985 report of a similar nature with articles by Ian Kaynes, Martin Gregorie, Stafford Screen, Mike Farthing, and Ron Pollard. Prices for this one are: airmail, $5.00; surface, $4.25; same source. I haven't seen it, but I'll wager it's pretty good.
So, that's it. Farewell, friends. Remember to treat my successor as well as you've treated me (maybe better) and to keep him snowed under with photos, sketches, comments, ideas, and general gas. Just remember that I'm not dead, and I'd still love to hear from you folks — but I may not always have time to answer. Harry Murphy will continue next month (and every other month for entries to come), as he's been doing for some time now. Don't forget to send him photos, news items, etc., too.
Bob Meuser 4200 Gregory St. Oakland, CA 94619
Bill Hartill will be in the "Free Flight Duration" chair in September. Watch for it.
Transcribed from original scans by AI. Minor OCR errors may remain.
