Modular rockeTs Building Baffles - National Association of Rocketry

Figure 2.specific flight missions. In 2008 I adaptedthis rocket to test a compressed air ejectionsystem that I built.The next type of modular rocket thatI will discuss is the semi-modular. Thistype of rocket cannot be completely disassembled,but the major components canbe removed, including the fins and motormount. My TARC team used this conceptin our rocket design. In the past when afin would break, we were done flying forthe day. Then we had to go home, dig outall the fin material stuck between the bodytube and motor mount, and glue in a newfin. The semi-modular rocket allowed us tochange a fin within a few minutes right onthe field with nothing but a screwdriver.A semi-modular rocket is a better optionfor a rocket designed for a specific purposewhere full modularity would be unnecessary.The rocket my TARC team used in the2009 competition featured a removableFigure 3.Figure 2. How the tail sectioninternal assembly slides into thetail section tube.Figure 3. The inverted coupler atthe top of the tail section. The holesin the bulkhead allow ejectiongases to pass through.Figure 4. The nose cone wasscratch-built from cardstockand fiberglass.Figure 4.motor mount assembly, removable fins,carbon fiber fin attachments, and an ejectionbaffle (Figure 7). For the 2008 competitionwe used a similar design, but thefin attachments were metal. The metal wasvery hard to bend properly and ended upadding unnecessary weight to the rocket.For the 2009 model we improved our designwith carbon fiber fin attachments.These fin attachments are glued onto thefiberglass motor mount. There is a slot inthe rear of the fin and a hole in the front.This way, only the front screw needs tobe removed in order to remove the fin.Three screws attach the motor mount assemblyto the body tube. Nuts are gluedonto the backside of the tube coupler for22 MAY/JUNE 2010 Sport Rocketry