Ron and Taylor Pacheco's Space Derby Tips
- Inner Surface: Operating under the assumption that the faster we can make the propeller spin then the faster the rocket will go, we sanded the inside surface of the rocket---the area where the rubber bands spin---before gluing it together. In the unassembled kit, the inner surface is very rough; lots of small splinters and rough surfaces that could slow the rubber band as it unwinds. We sanded it smooth with the finest sandpaper we could find---1000 grit from a hobby shop---and then coated the entire inner surface with powdered graphite.
- Body: Both this year and last year Taylor was entirely responsible for the shape of the rocket, using a rough sandpaper to shape it, and then ultimately making the balsa surface almost shine with the extra fine sandpaper. I suggested that he work toward a round and skinny body, but he preferred it more square. I did trim 5mm of wood from each side of the rocket before he started, so even though the final rocket he created could have been more aerodynamic, it was very light and the surface was incredibly smooth.
- Paint: We noticed last year that paint can add a lot of weight to the rocket. This year we used high gloss model rocket spray paint, and put on only a single coat. Taylor did the paint job himself. He also used some black high gloss model rocket paint to put lightning bolts on the sides of the rocket. Overall, I think the paint job actually helped the rocket, because it smoothed the surface even more but added virtually no weight.
- Fins: Dad did the fins. Last year we had large fins, but this year we went for small ones. Since the rockets fly by hanging from tight wires, only the barest minimum of stabalization from fins should be necessary, and smaller fins mean less weight. I also ran the front edges of the fins through a knife sharpener and then smoothed them with sandpaper. The fin material is just under 1mm thick, but still presents a vertical surface if not sharpened. I have no idea if sharpening the front edges of the fins made a difference or not, but I guarantee we'll be doing it next year anyway.
- Propeller: As it comes in the kit, the propeller has a lot of rough edges and spots to it; things that could cause air friction and slow it down, as the propeller is very light. We used the extra fine sandpaper to smooth all the rough spots off the propeller, hoping to make the prop cut through the air with as little resistance as possible. Finally, we used powdered graphite to lubricate all the places where two surfaces might touch.
- Hanger Mounting: Last year we mounted the hanger so that the rocket was perfectly balanced. This year, we mounted the hanger so that the rocket was slightly front heavy. The thought is that as the propeller turns, it lifts the front of the rocket, and so with the hanger mounted further back, the rocket should be better balanced during flight when balance actually matters.
- Rubber Bands: All competitors are required to use two official rubber bands and all rockets get the same number of winds on the rubber band, so there's not a lot to mention here, but we did learn one important thing: you must use a liquid lubricant on the rubber bands. We broke two sets before our first race because we tried using powdered graphite only; it just didn't coat the rubber bands enough, and as they wound tight, the friction apparently caused uneven stretching, and so they broke at weak spots. After that we started spraying the rubber bands with a liquid teflon lubricant, and we never broke another set.