Sport Rocketry

since I was not sure how the coating was going to go with the three large ns, I want- ed extra. is time, I used a 2 liter plastic paint tub for mixing (Figure 11). Because of the size of the sustainer and amount of epoxy that needed to be poured, I gured this was going to be a two-person job. So I enlisted my wife to pour the mixed epoxy as I coated it over the sustainer with both hands. I kept the sustainer free of the rota- tor while spreading the epoxy and turned it manually as needed. I did not want to put too much resistance on the motor and have it burn out. Once the sustainer was coated, I hooked it up to the rotator and got it revolving. I used the heat gun, going back and forth several times. Aer about 12 hours, it was cured enough to stop the rotating and I let it sit overnight. e coating on all three sections is not perfectly uniform, nor free of imperfec- tions. You can see some champagne bub- bles and an unlucky y caught in one of the ns in Figures 12 and 13, as well as some waviness. You can also see some waviness in the sustainer in Figure 14. is did not occur on any of the smaller rockets I clear- coated. e epoxy added 3 lbs. to the Hy- perLoc 1600 and pushed the CG back 4.25 inches. RockSim now calculated 3600 for the epoxied, fully loaded HyperLoc with a CTI K555WH motor, knocking 680 . o the non-epoxied predicted apogee. It was ready to launch. As it turned out, because of weath- er and my schedule, I was not able to launch the newly epoxy-coated 1600 at NARAM-62 that summer. So the Hyper- Loc was wrapped up again for the winter. It nally did make a launch in July 2022 at a CMRMC launch in northern Vermont. e 1600 performed very well on the CTI K555WH, with a straight ight, arching over at apogee. It reached 3432' (average of Perfect Flight HiAlt45 and RRC2+ altim- eters), well within the margin of error for RockSim. It is wrapped up again to wait for its next ight, but I no longer have to worry about fading and fraying. ere was another project thrown into the middle of this all. I also used the meth- od to repair a berglass payload tube that had been cracked during a recovery mal- function. e rocket was a 4" in diameter, 66" long, and assembled from sections that were literally headed for a dumpster. I res- cued them and gave them a second life— short as it was since it made only one ight. e launch was on Lake Winnipesaukee with the Lake Winnipesaukee HPR club. e rocket was set up for dual deploy and all worked well except when the nose cone ejected at the pre-set altitude, it did not pull out the chute. Lake Winnipesaukee ice is unforgiving and the only sections to survive were the electronics bay, which was not damaged, and the payload tube which had a few signicant cracks, each several inches long at one end (Figure 15). I decid- ed to repair the payload bay by just coat- ing it with epoxy and in the process give it some color (Figure 16). Now I just need a sustainer and nose cone! OK, so what are the takeaways from all of this? e use of ball bearings and a strong axel clearly is the key to extend- ing the epoxy-coating technique to larger, heavier rockets; and I'm condent that the technique will work with even larger rock- ets than the HyperLoc 1600. Although the coating on the 1600 does have some imper- fections (e.g., champagne bubbles, some unevenness, and a embedded y), I'm condent they can be corrected with prac- tice. However, epoxy does add signicant weight to a large rocket, and if your goal is maximum altitude or speed this is not for you. But if you are willing to forego some performance, then this is a good method to put a protective glossy nish on pretty much any rocket. 46 MAY/JUNE 2023 SPORT ROCKETRY A berglass payload section, repaired and epoxy coated with alcohol inks to add color.

• Cover