Issue link: https://www.e-digitaleditions.com/i/1197609
26 JANUARY/FEBRUARY 2020 SPORT ROCKETRY ter which blade is positioned up. Out of balance blades will make the unit descend with a revolving motion, instead of staying positioned on its vertical central axis. The same symptom will occur if the blades have differing pitch. If you built consistently, using jigs, they should have the same pitch, however changing humid- ity will affect balsa wood and will often need minor adjustments. Holding the cen- tral shaft upright, rotate the unit to inspect the pitch of the blades at the tips. If they are slightly off, twist them by hand to give them a temporary set. Flying the Model Fold the rotor blades together, pull the Kevlar line taught around the tip of one blade and up the side as you insert the unit straight into the rocket body. The line needs to be straight up the inside of the tube, out the top of the body and straight down to the end of the tube with no twist- ing (see Photo 9). Insert a motor, secure the Kevlar line around the motor where it meets the tube and tape the motor, line, and tube together (see Photo 10). Use a motor with an appro- priate ejection delay time so the ejection is close to or short of apogee. Fortunately Estes A3-4T motors work very well, since they are the only lightweight NAR safety certified motors allowed for current con- test use in the United States. At ejection the rotor unit is forced out, the blades deploy, and when the line is fully extended, the body will be pulled around backward. This swinging action of the body absorbs the excess energy of ejec- tion and prevents damaging any part of the model. The Kevlar cord easily handles the heat of the ejection charge from dozens of flights and it is more likely that you will lose the model before you need to change a scorched and weakened cord. As a mat- ter of fact I have lost four models out of my last six contest flights, so my present challenge with this decade old design is to develop a lightweight and reliable de-ther- malizer system. Which just goes to show that flying these FAI events year after year never gets boring, only more challenging. So if this sounds interesting to you, start building, flying and experimenting. And good luck in future U.S. team flyoffs! Keith loads his S9 model on into a tower at the 2019 U.S. team tryouts. www.siriusrocketry.com motors - chutes - tools - adhesives - parts - great kits from the finest manufacturers - and so much more in our secure online store! It's now time to have some serious fun with rocketry, visit us today! The Sirius Rocketry Eradicator is the newest kit in our Transition Series of kits, rockets that fly comfortably on F & G motors and are built to fly on an H when you're ready for your level one! From model to High Power, we're serious about rocketry! Transition into fun!