Whirlaway (oz13495)

About this Plan

Whirlaway. Free flight rubber helicopter model.

Quote: "Whirlaway, by Paul Del Gatto. PICTURE WHIRLING blades, the ability to hover, fly straight up, make spot landings, and you get some idea of why we like helicopters. A rubber-powered type, like this, is the best model to start with. It costs no more than a movie ticket, and it's easy to build.

Study the plans and the scale carefully; then assemble the materials in the parts list. Begin construction with the fuselage. Following the side view in the drawing, make two separate fuselage sides. Measure all parts on the inches scale; then pin down the longerons, and cement them and the cross-braces. Let the sides dry for one hour. Using the fuselage top view as a guide, connect the two sides by cementing in the necessary top and bottom crossbraces. Then join the ends. For best alignment, put in the longest crossbraces first.

Having completed the fuselage frame, install the landing gear aiientbly. As the drawing inset shows, the nose strut and them:lin landing gear strut are bent from .040 diameter wire ceitt.ntd and bound to a piece of 3/32 sheet balsa. Make the 1 in diameter wheels of balsa or purchase the light-pla.itic kind at a hobby shop.

What may seem the most difficult part of the model is the construction of the motor tube. Actually, it's simple to make. Notice that the top rotor vane is attached to a drive shaft that runs through a piece of metal tubing and then into the balsa motor tube. This drive shaft is fastened to the rubber motor. The lower rotor vane is different in that it is fastened to the metal tubing which in turn is fastened to the balsa motor tube. The detail (lower left in the drawing) shows exactly how to fasten the metal tubing to the top of the motor tube and how to fix the winding hook to the bottom of the motor tube.

Now when the rubber motor is wound and released it rotates, causing the top vane to rotate in the same direction. At the same time, the motor sets up an opposite force, causing the balsa motor tube and the lower vane to rotate in the opposite direction.

The motor tube is made of 1/16 medium sheet balsa, sanded to reduce weight. The bearing plugs are made of three pieces of 1/16 sheet balsa cemented so that the wood grain crisscrosses. The two bottom bearing plugs are removable so the rubber motor can be pulled out and wound (lower right on diagram) .

Cut out four rotor vanes from 1/16 medium sheet balsa to specifications on the plan. Sand them to get the right airfoil curve shown in the blade section. Cut rotor hubs from 1/4 x 3/8 hard balsa, 2-1/4 in long, and slot them with the correct pitch angle for the vanes. The top vane slants 20° one way and the bottom vane slants 30° the other way (upper left in the drawing). Cement vanes into hub slots.

Next comes the drive assembly. Get a piece of thin-wall metal tubing just large enough in diameter to run the .040 shaft wire through it freely. Slit one end of the tube, bend it over, and cement it beneath the top bearing plug. Washers are soldered to the metal tube to prevent it from slipping into the motor.

The bottom rotor vane is cemented and bound with thread permanently on the metal tubing. To install the top rotor vane, force the wire shaft through the hub and bend it into a thin metal plate cemented on the hub. Place several small washers on the drive shaft beneath the hub and insert the shaft into the metal tubing. Bend the end of the shaft to form the motor hook. Assemble the bottom removable bearing and plug unit as shown. Use six to eight strands of 1/4 brown rubber for the motor. It should have enough tension to hold the bottom plug in place. After the motor is hooked up, cement the top plug lightly for easy removal.

Install the rudder made of 1/16 medium soft balsa and cover the fuselage with tissue paper. Dampen it with a cloth to shrink it; then apply a coat or two of clear dope."

Direct submission to Outerzone.

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