Sport Rocketry

22 MAY/JUNE 2022 SPORT ROCKETRY Every once in a while I'll meet a fellow rocketeer who has their doubts about baf- fles. Sometimes they're just uninformed, other times just skeptical about their re- liability. I'm a big fan of baffles and have been using them for over 20 years. Every rocket I own, size BT-20 or larger, uses a baffle. And they have proven very re- liable. Club records show that for our 2019 launch season, I had 75 launches of which 72 were successful. Take away the back-to- back catos and the one tangled chute, and it's 72 for 72. And all of them used some sort of baffle. ere are two types of baffles that I particularly like. I've named them flute-and-strainer, and flute-and-sprocket (Figure 1). ey're my favorites for three main reasons: First, they're remarkably efficient and well ventilated. My simple reduction cal- culations show that perhaps less than 1.25% of the fiery ejection particles ever get through to the payload. A visual in- spection of the shock cord and payload section shows just how well they work. Aer many flights, the cords and payload areas still look new and clean. No signs of charring or singeing. And both have excel- lent ventilation. Each matches or exceeds my venting requirements so under or over pressurization is never an issue. Not only that, they never seem to get clogged. Just a few shakes of the rocket rightside-up and upside-down gets the gunk out. Second, they offer great protection for your payload contents. Figure 2 shows a flute-and-strainer baffle that survived a cato that blew up my Estes Executioner in a fireball that spewed debris all over the range. e circular burn marks on the inside of the section of peeled-away body tube are from the flute's vent holes! e motor side of the baffle and the inside of the flute are pretty well charred too. But look at the clean payload side in Figure 3. My Apogee Components parachute and Jolly Logic Chute Release escaped un- scathed. at's $150 in components spared from destruction. And most recently, a cato blew out both ends of my Atlas V-541 on its maiden flight. Figure 4 shows the af- termath. ere's not much le of the flute- and-sprocket baffle, but the shock cord and silky parachute are just fine. Look closely and you can see that the rubber band on the Chute Release is still intact and holding the chute. at's pretty good protection, especially considering that nei- ther flight used any wadding. ird, these baffles are economical and easy to build. Either can be built for less than $2.00. All you need are two lite-ply centering rings, 2.25" of tubing, a small cardboard or balsa bulkhead, and an en- gine block. is keeps them lightweight, ranging from just 3.9 to 13.3 grams. And if you're pressed for space, either can be built inside a coupler book-ended by the rings. ey're also a great spot to anchor the teth- ering harness. Flute-and-strainer baffles are ideal for BT-70 and BT-80 rockets since there's ample room for the vent holes on the strainer ring. But things get a little tight on BT-55 and BT-60 rockets. Drilling the needed holes into a BT-55 or BT-60 cen- tering ring won't fit without splintering or weakening the ring. So here's where the flute-and-sprocket type comes in handy. Larger semicircles can be cut in from the The Flute -and- Sprocket Baffle by Mike Moran NAR 216855 Figure 1. A flute-and-strainer baffle with two flute-and-sprocket baffles in the background. The Flute -and- The Flute -and- Sprocket Baffle Sprocket Baffle

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