BEFORE YOU conclude that this is a modelof a helicopter, take another look. It's a modelplane with a spinning wing, or rotor, that wind-mills in the slip stream of a conventional pro-peller to provide the lift necessary for flight. Therotor is self-spinning and that's where the auto-giro or gyroplane, as it is now called, differsfrom the airplane and the helicopter in appear-ance, in flying characteristics and also in con-struction. And on the end of a control line itis a new experience for model-plane fans.

Control-line gyros have been built, of course,and flown with fair success. But none could beconsidered spectacular performers. Some showeda persistent tendency to roll up in the controllines and some that performed satisfactorilyotherwise developed an arm-shaking vibration.This appears to have been largely due to use of arigid motor which tended to develop a conditionof unbalance while in flight. The rocker-type, orseesaw, rotor used in this model starts spinningquickly and easily and the gyro lifts off and fliessmoothly without dipping, diving or rolling. Itpulls hard, but not too hard, on the control linesand settles as lightly as an autum leaf when themotor fades.

The fuselage is simply an elongated balsa boxmade mostly from 3/32-in. material except thebulkheads, A, B and C, and the stabilizer which

Mount engine on the fire wall with four small bolts,using washers under left mounting to provide offset

Remember thespinning-wing

autogiro?By ROY L. CLOUGH, JR.

are 1/8-,in. stock. Although the over-all size ofthe bulkhead, C, is given, you may have to dosome fitting of this member to assure a true fair-ing of the fuselage sides and top piece. The fuse-lage is fitted with a conventional engine, pro-peller, landing gear and a standard control-lineelevator for controlling the gyro in flight. Therotor mast centers 4-1/4 in from the forward endof the fuselage. In assembly it passes through thebottom of the fuselage, the bend at the end beingseated and cemented in a notch cut in the bottomof the fuselage. Note that it also passes throughthe control strut and the bell crank. Washersare soldered above and below the crank, per-mitting the latter to swing freely on the mast.After installing the controls and the reinforcingstrips at the forward end of the fuselage, cementthe fuselage top pieces in place, then the pilot'shead and the fairing.

Study the rotor drawing closely. Note thatthe blades operate at a negative pitch and thatthe rotor, although stiff from tip to tip, is pivotedat the center to permit a seesaw motion. Stops on

the hub pivot limit vertical motion so that theblades won't strike the tail. This type of rotormount allows the blades to rock without trans-ferring motion to the fuselage, yet keeps therotor tracking evenly.

Give the model a coat or two of sealer beforeapplying pigmented dope. Make certain thateverything runs freely, and that the center ofgravity is either right on, or just ahead of thecontrol crank or bell-crank axis. If the center ofgravity (CG) is behind the control-crank axis,the model may not pull hard enough on the linesto give good control.

After you get the feel of it, you can make jumptakeoffs by letting the model roll about 6 ft.,giving it full up and dumping the elevator quicklyto bring it into a normal flight attitude. Inciden-tally, that machine-gun-like popping you hearin flight is common to all rotor craft. It's causedby the rotor blades running into their own tipvortices.