About this Plan
Hoppity. Control line autogyro model.
Quote: "Try an Autogyro! Hoppity, by WI Barrett. Offers a change for 2.5 cc engines. Ideal for display work and fun flying.
HOPPITY was designed as a novelty item for club flying displays, with a semi-scale outline similar to many modern light helicopters - definitely no relationship with James Bond's Little Nelly!
Building the model is straightforward, provided that the correct sequence is carried out. The engine bearers, undercarriage and bellcrank assembly build up to the primary unit, after which the fuselage sides are added.
The wing is made very simply from 1/16 sheet balsa, the upper surface curve being formed by steaming. Drop the lower surface into position, cutting where necessary to clear the bellcrank and push-rod assembly. Then add the ribs, feeding the port ones over the lead out wires. When dry, cement and strap on the upper, cambered, surfaces, and fit the tips.
Make up the tailplane and elevator, and cement to the fuselage, then position the elevator horn in conjunction with the push rod. Sheet the under surface of the fuselage, not forgetting the tailskid. Now add all the formers. Some soft block behind the lower half of the nose former will allow the rectangular section of the fuselage to be faired into a circular section. Carefully fit the rotor wire, with the correct amount of 'backsweep at the top to give a 12° rotor axis angle.
Slot in the stringers, and sheet in the sides with 1/16 balsa. Add the tip fins, pre-cementing the joint. If desired, an instrument panel can be stuck to former F2, and a pilot inserted in the cockpit, before fixing the windscreen.
The prototype model was fitted with an acetate cowling, held in position with snap dress fasteners secured to the cowling and engine bearers by Araldite. A similar cowling could be built from sheet balsa. Cut out suitable holes for the needle valve and exhaust gases.
With the model structure complete, all that remains is the rotor. Select some medium hard springy balsa for the blades, and make two identical (not opposite hand). Build up the hub as shown in the sketch. A sound plan is to cover the inner third of each blade, including the hub, with glass fibre cloth, coating the whole of the blades with the resin. When dry, rub smooth and balance carefully. Screw in the bearing bush, and retain on the rotor spindle by sweating on a short length of brass tubing.
Cover the model with lightweight tissue, and decorate to choice. The finished model should bal-ance on the wing leading edge.
Flying is straightforward, and the model will hold out on 50 ft. lines in calm conditions. A third line throttle-controlled engine would enable power-on landings to be made. As flying speed rapidly falls once the engine stops, it is advisable to fly low towards the end of the engine run, so that the model may be 'wheeled on' with sufficient elevator control to keep it level.
One last word - the model is an Autogyro, not a helicopter, but just try explaining that to all the spectators you will have watching!"
Hoppity, Aeromodeller, December 1967.
Direct submission to Outerzone.
Supplementary file notes
Article pages, thanks to RFJ.
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