Issue link: https://www.e-digitaleditions.com/i/1197609
be a project worth pursuing, so fast for- ward 11 years to July 2018. At the WSMC held in Poland, the entire U.S. Junior and Senior teams flew models with rotors con- structed this way. Our best finish was from former NAR national contest board chair- man Steve Humphrey who placed 4th in the flyoff with nine other competitors, just missing being on the medal stand. And at the recent 2019 U.S. team selection flyoff, every S9 entry was made this way. By the 2010 WSMC, the blade's shape had become very close to what it still is today. The widest portion with the most pitch is near the hub and drives the rota- tion. The width gradually tapers to the tips, which are level with no pitch. In the early years the rotor unit was pushed out of the body with an ejection plug and the shock cord was mounted internal. The bodies were made with a steep 8-degree tapered tailcone which allowed for 11.25" long blades to fit in a minimum length body, by FAI rules. At the 2011 U.S. team flyoff, the mod- el's popularity was growing. About half of the entries had curled blades. It was at that meet when Katherine Humphrey (Steve's daughter) flew a model with a long nose cone shoulder that acted as a piston to pull the rotor unit out of the body when ejection gases pressurized the tube. This solved the problem of breaking the fragile blades at ejection, and quickly led to using the normal S3/S6 body having a 5 degree tapered tailcone with a more aerodynamic shape. Now, longer 13.5" blades that ex- tend down to the motor tube fit in the min- imum length body. These changes made for higher boosts and longer descent times. At the 2012 WSMC, half of the U.S. competitors flew models with these inno- vations, and another, mounting the shock cord externally. This system came about as a method of deploying the antennae of a Walston tracking transmitter from where it was coiled up in the body during boost. Tim VanMilligan of Apogee Compo- nents published some very good articles in his Peak of Flight newsletter about mak- ing the curled blades, and on developing a hub with laser cut parts that are easier for young modelers to assemble. That hub is used in his Rotary Revolution FAI S9 com- petition kit. Tim and his daughters contin- ued to experiment with blade design for the basis of several NARAM Research and Development competition projects. Numerous other R&D projects about the design have been made, and it was even scaled up and successfully flown by Alan Stokker in the G Helicopter Duration event at NARAM-59. Undoubtedly, the design's highest hon- or was taken at the 2014 WSMC in Bul- garia when Senior S9 team member Trip Barber took home an individual bronze medal. Doug Hillson has done a wonderful job drafting Trip's model. Those plans can SPORT ROCKETRY JANUARY/FEBRUARY 2020 17 Photo 3. Wet S9 blades taped to mandrel (top) and wrapped with cloth strips (bottom). Photo 4. Set of dry S9 formed blades (with some more soaking in ammonia solution in background).