Flexwings (aka Para-Wings) Article & Plans
May/June 1963 American Modeler

May/June 1963 American Modeler Table of Contents These pages from vintage modeling magazines like Flying Aces, Air Trails, American Modeler, American Aircraft Modeler, Young Men, Flying Models, Model Airplane News, R/C Modeler, captured the era. All copyrights acknowledged.

"The flex-wing is now frequently referred to as the 'Rogallo Wing' and the name will probably stick." That quote is from a 1963 edition of American Modeler - nearly 50 years ago!. Author Scholefield certainly was correct in predicting that the "Rogallo Wing" moniker will stick. There have been quite a few articles for such R/C models since then, and I've seen at least one company advertise a "Rogallo Wing" kit, but if you're interested, the info here should do just fine.

Flexwings

R/C Flexwing by Scholefield

TWO APPROACHES:

1. Simple Radio Control

2. Ready-to-Free-Fly

The construction of the flexwing, as shown in the sketches opposite, requires a minimum expenditure of time and money while at the same time allows the adventurous modeler to explore a new realm of flight.

Salient points in construction are the selection of materials. The keel and outriggers should be as stiff as possible. The first wing used 1/4" dia. hardwood dowels. These proved fairly successful, but later wings employing aluminum tubing held their shape better under flight loads.

The sail material can be purchased at any dime store. I used medium weight sheet plastic (sold by the yard in 54" widths). The biggest problem here was finding a material with a pattern other than roses, ivy, or designs for the discriminating housewife. I finally found a simple blue and white stripe that didn't look too much like a tablecloth.

The shroud line material should be selected for maximum strength. I used nylon lacing cord. Also all knots should be glued. A broken shroud line will cause a crash that would do credit to any multi-ship.

The fuselage can be any old rudder - only with .15 to .19 power (Esquire, Charger, Cub, etc.). I connected all shroud lines directly to the pylon mounting platform so as to keep the flexwing independent of the fuselage. Strap the pylon to the fuselage with rubber bands in the conventional manner. Due to the extremely slow flying speed, I would recommend a generous amount of rudder control. Some flight trim, in addition to shroud adjustment, may be achieved using elevator shims as required.

Flight characteristics of the present version of the flex wing leave little to be desired in the area of stability. In fact, this is probably the most "novice proof" ship ever put into the air.

Scholefield's easily-duplicated R/C flexwing.

The author/designer says any rudder-only job will do.

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Former National air-model champion Henry Struck with experimental "Wing Thing."

John Worth, newly elected president of the Academy of Model Aeronautics, is seen (left behind simulated rocket section and below starting R/C plane engine) with NASA flexwing experimental models.

Experimental military drone made by Ryan; took off and landed from jeep platform under radio control (above).

Prototype of Gilbert's "Wing Thing" with 36" main spar; Gilbert·7 engine.

ROG's are a snap. In fact, the ship has never failed one (in spite of me). Jim Hoover, a fellow member of the Endicott Aero Guidance Society, ROG'd and flew the same ship at the October Jersey meet with only 5 minutes of verbal instruction prior to leaving Endicott. One final virtue of the flexwing is its dual role of sunshade and umbrella! - C. Scholefield, Binghamton, N. Y.

"Tech Talk" by Bill Effinger

Some may call it "Para-wing," or "Para-glider," but it all adds up to a brand new type of flying that is the biggest new idea in model aviation since Jim Walker introduced "U-Control."

For me it started two years ago when A. C. Gilbert's new products planners wanted a glider kite with some form of power for maneuverability.

Here was a challenge that could not be met with orthodox design. Henry Struck and I kicked around ideas for several weekends. Being old balsa butchers, we knew that there were several approaches that offered possibilities, but the weight of ready-to-fly plastic models was the big drawback.

The NASA flexible wing experiments using a flex-wing in combination with a "Custom Cavalier" made us consider this possibility. (The original "Cavalier" was designed by Ben Shereshaw in 1935; I redesigned it as the "Custom Cavalier" in 1941.) NASA Technical Note D-629 by Rodger Maeseth was the beginning of a long period of "trial and error" test and research, culminating in Gilbert's new ready-to-fly "Wing Thing" which should interest everybody as the starting point in flex-wing flying. Model builders will find new and interesting variations of flex-wing flying, all the way from indoor competition through radio control.

What have we been able to do with just one airplane? Here is a list of repeatedly conducted successful flights without structural damage of any kind:

TOWLINE GLIDER: Takes off without assistance. Tows much easier than high aspect ratio gliders. Sinking speed depends on loading, which can be kept extremely light.

KIT: Has been flown for hours by a 5-year-old. Somebody wisecracked, "The best place to store Wing Thing is in the air, nobody can step on it then." About 15-mph steady wind is needed for good kite operations. It is the only kite that glides when the wind dies down.

FREE FLIGHT: Hand-launched or Rise-Off Ground. Four have been lost to date. Two of them straight up in thermals.

TETHER: Yes, the fellow who wants to operate on the end of a string in his back yard can fly Wing Thing on a 15 to 25' tether line.

SLOPE SOARING: If you are lucky enough to live on a hill, you can use it as a hand launched glider, too!

CAPTIVE FLIGHT: Truly the most sensational new concept in model flying. Catapulted take-off, towing up to 350 feet on light kite string, steered in flight at the end of the line, then finally allowed to return to the ground as a guided glider. Not until you have a line on the model do you realize how high up 350 feet really is.

When the project got under way, NASA Reports were used as design criteria and the parameters set up proved out in model size. Investigation of past experiments show that the idea started with the George Wanner Patent No. 2,537,560. Although Mr. Rogallo is given credit for the flexwing by NASA, the Rogallo Patent No. 2,546,078 differs considerably from the flexwing that is now being test flown full-scale. I sure would like to see George Wanner, whose Baby ROG's started so many of us in model building in the late 1920's, be given some credit for the basic idea. The flex-wing is now frequently referred to as the "Rogallo Wing" and the name will probably stick. (The basic Wanner patent is now the property of the A. C. Gilbert Co.)

At the very beginning of the test flying, Struck experienced difficulty with recovery from stalls. The flexwing as originally designed was intended for use as a kite and had no means for recovery from a dive once the wings became deflated. In other words, once zero lift occurred, lift would remain at zero until it made a neat hole in the ground. The FAA had found out about this and put out warnings as far as full scale planes are concerned. Experimenters who didn't flight test with models first could learn the hard way with their lives!

A "bull session" between Hank and myself resulted in the forward stabilizer. This has solved the stall recovery problem. The stabilizer has sufficient moment to pull the nose up in any dive. It has the further advantage of holding the airstream over the flexwing at high angles of attack, similar to a wing slot on a conventional wing.

From this point on, it was a matter of continual flight testing to check the possibilities of this new type of flying. Our first models were tractors. We used .020 engines for development work because we could build this size model faster. Tractor engines gave us trouble in starting because the tow bridle got into the way. The pusher configuration gave us ease in handling. The rear rudder was added primarily to provide a place to hold the model when the engine was running. It also gave a good tripod point for R.O.G. flying.

Flex-wings have so light wing loading that very little power is required for flying. One 8 1/2 ounce version with a Cox .020 had no trouble climbing to the end of a 250-foot towline on 3/4 of a standard tank of fuel. We found that too much torque and thrust were a big problem to handle in light tractor models. They would either loop or spin in. Weight of about 2 to 3 ounces for each .01 cubic inch displacement makes a good sport flying airplane. No doubt contest flyers will be able to pack in the power and get tight spiral climbs, but it will take skill and experience.

The flex-wing is quite critical on c.g. location, more so than conventional models. A movable weight for trimming is incorporated in the ready-to-fly Wing Thing and is recommended for any home-built designs.

COVER MODEL

A not-so-miniature scale job! Half-size Nieuport 17-C-1 control liner is by Bob Hawk, 21, of 1821 Florida Ave., N.E., Albuquerque, N.M. Bellcrank is 18"; home-made fiberglass engine cowl; 2 1/2-hp Lawson 4-cycle engine (was auxiliary generator in WW-Two bomber) swings 3' prop, also home-made. Span 11-ft, length 8 1/2-ft, height 3 1/2 ft, weight 85-lbs. Fuselage of white pine, fir and fir plywood; covering is unbleached muslin. Sliver aircraft dope finish. Six months to build.

A general layout of the basic design will get you started if you want to build your own model. Design parameters should be followed fairly closely as they have been determined after considerable experimentation. Gilbert's Wing Thing should be available at your local dealer by May 1st. It makes a wonderful model for a son or younger brother to start free-flight flying. At least, you can use it as an excuse to have a lot of fun yourself with a ready-to-fly.

Mail Bag. I will be glad to answer any of your letters on anything that appears in this column. Just write to me, Bill Effinger, c/o American Modeler Magazine, Conde Nast, 420 Lexington Ave., New York 17, N. Y.

I had a "hot" letter from Bud Tenny, the editor of Indoor News and Views, shouting that I was against Indoors. Believe me, about the only thing I am against that flies is the African Tsetse Fly. Unfortunately, I think a lot of the indoor boys have been bitten by it. I hope they wake up to the fact that we will shortly have enclosed baseball and football fields in many of the big cities. We will need new events if we want to get enough people interested to use them for flying.

I had a "nice" letter from George Dabrowsky of Edmonton, Alberta. He likes what I said about current" contest events and proposed a special "Research and Development" Event.

Actually, I am hoping we can get model builders throughout the country to form an organized R & D group willing to take specific test assignments. A future column will cover some of my experiences with airfoil R & D and how little is really known about airfoils for models.

Posted November 24, 2012