Hoppicopter (oz12632)

About this Plan

Hoppicopter. Rubber indoor helicopter model.

Quote: "Make this indoor helicopter in an evening for a novel contest in the clubroom. Hoppicopter, by FG Boreham.

TAKING ITS name from a tiny single-seater co-axial American helicopter the 'Hoppicopter' is a tiny framework of fun that calls for a few strips of balsa, some cane or reed, two beads, 20 swg wire, a scrap of tinplate and some writing paper.

All set? Lets start with the 5 in long paper tube, which we make by wrapping cement coated writing bond around a suitable 3/8 in dia dowel. Noseblock and plug, and the two rotor hubs are shaped from 3/16 in sheet, then the writing paper rotor blades are attached to cane leading edges.

Now we can assemble the working parts, fitting a dowel motor peg in the tube and making up the 20-gauge top rotor shaft. Plug the blades into their respective hubs, making each droop at the trailing edge to get a pitch angle, and slip four strands of -1 in. rubber between shaft and peg for power. We can now experiment with the basic helicopter, adding the 'fuselage' frame later.

Wind up the motor and release, pointing vertically. If the 'copter has a wavy, unstable flightpath, slide the lower rotor down the tube and try again. If you slide it too far down, the reaction might be to make the whirly-bird go head first into the ground. The medium position gives a true vertical ascent. This little demonstration illustrates the importance of the CG position relative to the centre of pressure, and when the fuselage is added, the lower CG acts as a stabiliser, enabling the rotors to go closer together.

Why not have a 'Race to the ceiling' contest on your next club night?"

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