Origo (oz7682)


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About this Plan

Origo. Rado control sport model. Wingspan 38 in, wing area 252 sq in.

Quote: "Progress has been made in the fields of Radio Control during the past years. Especially on the equipment sector, new outfits are coming up rapidly, literally flooding the market. Almost all of the systems provide multiple channels which make it possible for the modeler to control his aircraft model with far more functions than those required for flight maneuvering of the model.

As a consequence, the trend of radio control models has been inclining toward large and heavy designs powered with big engines in order to be able to make use of existing control opportunities. These machines are undoubtedly realistic both on the ground and in the air. In flight, their maneuverabilities are limited only by the imagination of the modeler.

However, this category of models necessitates a substantial investment both in money and in time. Thus, an accident or a crash will cause the modeler a noticeable loss.

With these thoughts in mind, the Origo was constructed. The basic idea of the design was to provide a compact model with attractive looks intended primarily to be flown using a simple radio system. The design would also be furnished with an elevator in addition to rudder and motor control. This may seem unnecessary for small models. However, since elevator control always means better increased flying maneuverability and may be included without much extra cost, it has been employed in the design.

A considerable amount of care was laid on the appearance of the model. A scale machine was out of the question in view of the size and powerplant of the model. A low-winger was thought too tricky to be handled safely without ailerons so this type of design was also eliminated. The best solution in this case would certainly be a high-wing cabin sportster. This idea was discarded, however, because I feel that this typical radio design is too common. The shoulder-wing design was finally chosen. This design configuration was selected because it offered a somewhat out-of-rut style and a realistic appearance in combination with good rudder-only stability.

In the design approach, attempts were carried out to lessen the ballooning tendency small models make when en-tering and recovering from a turn. To accomplish this, the tail moment was lengthened to gain longitudinal stability. Similarly, wing dihedral was reduced to an angle which proved a satisfactory compromise as far as lateral stability was concerned. To further insure good flight stability, the horizontal tail was liberally dimensioned, making flight set-tings less critical.

The Origo features easy and straight-forward construction methods. Structurally, the design is rugged enough to withstand the impacts when we miss every now and then. Once properly trimmed, the model possesses a constant stable flying performance which is as it should be for a machine designed mainly for fun-flying.

The two-wheel landing gear shown permits nice take-offs into the wind. Cross wind take-off would be a different matter because ground loop can be the rule rather than exception so never do it. This two-wheel type of gear was employed because it is simple and can absorb a lot of abuse from rough landings which, by the way, may not be the case with a trike gear. Also, I imagine that many flights will be hand-launched, particularly if you operate from grass field.

The Origo measures 38 inches in wingspan and 252 square inches in area. Suitable powerplant would be engines around half-A size. Even an engine of .09 capacity is conceivable if you are an experienced flyer. Radio outfit may be any single-channel set up to a light-weight Galloping Ghost system. Incidentally, a Galloping Ghost system in combination with a .09 engine would bring about performance capabilities with this model similar to the large proportional aerobatic jobs.

The prototype is powered by a .06 diesel engine and equipped with a single-channel super-regenerative receiver with a Babcock Compound escapement for rudder and up-elevator on third signal. As the source for electric power, durable DEAC nickel cads are used. This radio set-up is clearly shown in the photograph.

As you will notice, I did not specify any particular radio installation on the plan. This has been left out intentionally in view of the many suitable radio systems that can be used in this model. In any case, I believe that no space problems should be encountered in the accommodation of the is comprised of two chambers, the small one in the front part of the body being used to house the batteries.

You can see on the plan that materials specified often have generous dimensions. This has been done because I feel that it is easier and more rewarding to work with light oversize wood than harder and thinner materials. Therefore, it is important that you spend a little extra time at the balsa medium or medium-soft balsa wood should be selected in order to keep the weight down to a reasonable level.

Before starting the construction, I should like to touch a little on the cement that is to be used during the building sequences of the model. I have found that white glue is superior for all joints where strength is essential. However, this type of glue is heavy so apply it with consideration and avoid it on less critical points. White glue should be avoided on external surfaces because it never really hardens and therefore makes any sanding quite irregular.

CONSTRUCTION: Make the wing first, which is built in two separate halves, joined at the proper dihedral angle when ready for balsa sheet covering. After cutting the ribs and spars, pin the unshaped leading edge and standard triangular trailing edge pieces on the plan over wax paper. Be sure that the notches are already cut in the trailing edge. Incidentally, when cutting these notches..."

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