The Cyclone is a BT-20 medium-sized model rocket that uses a "unicopter" recovery system based on the dynamics of a maple seed. These plans are derived from the final version of the rocket, which has been extensively flight tested. The model is easy to fly and works reliably. As usual, you should be careful whenever you launch any rocket. A BT-5 version was also built, but is harder to see and easy to lose due to its small size. Therefore only the plans for the easy-to-see and easy-to-find BT-20 version are listed. Still, the BT-20 version can take up to 20 seconds to descend in light winds. Launch it on a very windy day and you could lose it. Be especially careful to follow the directions exactly when you build Cyclone. The weight distribution, the spin unit's fin angle,and its structure are critical for correct unicopter operation. The design is also interesting because the spin and stabilizing units are stable when connected together, but highly unstable individually. The instability in each is what causes them to spin, each in a different way, to the ground, without the need for extra fins or canted fins (as in the Estes® Tornado and Estes® Twister). Therefore, making changes to this design can result in flights that are hazardous to the builder and spectators. Undertake design modifications and subsequent flight testing very cautiously. The rocket is composed of two units. The parts list and assembly instructions are given for each:After building each unit, paint or decorate it according to your preference. This painting scheme emphasizes the flat rotation of the spin unit (painted BT-5 Mini-Cyclone shown). Assembling the Cyclone for Launch is accomplished by inserting an A3-4T mini-engine into the stabilizer unit. The two units are then joined by attaching the stabilizer unit's coupler to the spin unit (BT-20 Cyclone shown).
Attach an igniter and a launch plug to the mini-engine, then place the rocket on the launch rod. Make sure your launch controller is safed, then attach the mini-clips. Insert the key into the controller, give a 5-4-3-2-1-Launch! countdown, and send Cyclone up! You will hear the rocket whistle during its ascent (due to the exhaust gas vent), then at apogee it willl separate into the spin and stabilizer units. The stabilizer unit will fall back quickly, while the spin unit will take up to 20 seconds to return, appearing to hover in the sky. You might add chrome tape to the spin unit and see if anybody reports seeing a flashing UFO!
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