Issue link: https://www.e-digitaleditions.com/i/1197609
Introduction The rocketeers that make up the U.S. Spacemodeling team love to fly the FAI events. FAI is the sanctioning body for in- ternational rocket competitions and hosts its World Spacemodeling Championships (WSMC) in the summer of the even num- bered years. The NAR hosts the U.S. team selection flyoff as part of the Annual Rock- etry Festival in the odd numbered years. Last July the 2019 flyoff was held in Mun- cie, Indiana. Since the FAI events seldom change we are given the challenge to con- tinually work to perfect a design over a long period of time. For the S9 Helicopter Dura- tion event the ba- sic rules and mo- tor class has not changed in 15 years. This article is about one such design, which was primar- ily made to be a simple approach to this compli- cated event. Its helicopter re- covery rotor unit fits in the same 40 mm diameter FAI style bodies used for the S3 parachute and S6 streamer duration events. Build- ing the bodies has been covered in other Sport Rocketry articles, and links to de- tailed building instructions and a video can be found on the NAR website's Spacemodeling page. The Model's History Preparing for the 2007 U.S. team se- lection flyoff my choice of models to fly in S9 was limited. At that time the state- of-the-art design was George Gassaway's "flop-rotor" which has long thin flat bal- sa blades that fold in the middle. For me, these were a lot of work to build, prep, and deploy reliably. I knew I needed a simpler design so I tried something I saw the Euro- pean fliers doing and I managed to put six single rotor blades in a 40mm tube! They had to be thin, curled, and arranged to un- fold like the petals of a flower. Using only three blades still proved to be best, but this curled blade's shape improved their struc- tural strength which allowed them to be made from thin balsa which needed no air- foils sanded in them. Wow, a shortcut in building time, better reliability, and a lot of performance from less material! This could 16 JANUARY/FEBRUARY 2020 SPORT ROCKETRY Photo 1. Keith holding an original version of the S9 Gyrocopter design in 2008. Photo by George Gassaway. Photo 2 (Insert). S9 model in flight. by Keith "Herby" Vinyard NAR 24568 Give this S9 a Whirl Wanna Fly FAI? Wanna Fly FAI?