Kit
Contents
Nose
Cone
Decal
(51k)
Display
After
Repair
Flight #3
Flight #11
The Custom Aztec is your basic BT-50-based 3FNC two-stager. The construction is simple and straight-forward, the limited decals are two-color and somewhat pointless and/or uninspired, and you could easily clone the kit from Estes parts. (Why is this page black? The manufacturer's graphic at right looked like crap on a white background, that's all.)
For some reason, though, I really like this bird; perhaps because she reminds me of my favorite Estes kit, the Mark. She's the basic double we all grew up with, and would be a great first two stager for a young rocketeer. She's got enough size that a little imagination could make it look great, and the streamer recovery lets her come back quickly and safely. At $9, she's a great one-evening project.
My kit had all the parts, and they're all of high quality. The pre-stamped balsa appears to be good "B" grade stuff, stiff enough for fins, but sandable. Its thick, 0.105", almost requiring a bevel. The stamping isn't terrific, but not bad enough to cause any problems. The streamer is long; too long, really, 3 cm wide by 50 inches in length, well beyond the "ideal" ratio of 10:1. The tubes are high-quality vellum with little to no groove, easily finished. The thrust ring is thin, but the centering rings are dimensionally equivalent to other manufacturers', as are the tubes. Parts fit was loose, but not annoyingly so, and things went together without a hitch. The instructions are clear and easy to follow, if printed an odd order/orientation. The fin guide isn't the wrap-around kind I like, but printing one up from VCP was quick and easy, and I used the same one for both fin sets. I did extend the ~12 inch long, 1/8th inch wide elastic shock cord with a short piece of 300# Kevlar mounted around the thrust ring, thereby avoiding the Estes-style mount, but other than that, I made no modifications.
My highest praise goes to the nose cone, though. I've always had a problem with the attachment points on small Estes nose cones; they're large enough, but poorly designed, being jammed right up against the body tube when the nose cone is installed. The Custom unit, which is remarkably like the PNC-50K found on the Alpha, solves this by having two; one for the shock cord and one for the recovery device. You can compare the two versions in the photo at left, the Custom unit is on the right. Its rounded tip (with a bluffness ratio of ~20%) makes it shorter by an 1/8".
The complex paint scheme could be improved, and I chose a different one for my bird. First I sealed the fins with light weight spackle, then rough primed with Kilz, both sanded with 280 grit. The white primer coat was sanded with 400 grit, them a coat of Krylon Gloss White on the sustainer, and a store brand red on the booster and nose cone. I sanded the color coats with 1500 grit and applied the decals. I considered a clear coat, and it might have improved her weight enough to run the recommended motors, but I skipped it.
Custom's claim of "flights over 2,000 feet" can be done with a full C6 stack, though this little thing would be very hard to track at that altitude. In fact, just about any C motor at all takes her beyond the range of the unaided eye. Not listed as a recommended sustainer motor is the A8-5, which isn't surprising, they weren't available when I bought this kit. Now that they're back, I've included one in her matrix.
Her first flight was on a Quest A6-4, and while the inside of the tube got pretty sooty, the flight was perfect. Not a mark on the long streamer, and she was ready for her first two stage effort. The next weekend I loaded her with a B6/A8 stack and she flew fine. The sky was completely cloud-covered, and while she didn't come close to them, everybody lost the mostly white sustainer after burn-out. Two of us heard the deployment, but she was within a hundred feet of the ground before I picked her back up. Both stages were recovered intact, but I'll wait to fly her against a blue sky in the future.
Her next effort was the B6 stack and the sustainer failed to ignite. The bird recovered with the booster still attached, so I'm glad it didn't. The resultant lawn dart shoved the nose into the body tube, so she needs some repair. Boy, am I glad I scanned those decals.
I cut off the 2¼ inches of damaged body tube, but instead of replacing it I added a four inch long payload bay from the Quest spare parts kit (I think its from their Gamma Ray Payloader) that'll hold my altimeter. I cut off the bottom of the nose cone and added a one inch long balsa bulkhead from Rogue. I attached the shock cord and streamer to it with a screw eye. I repainted the nose cone and added a length of white Pactra trim tape instead of the wrap-around decal, which I now really didn't have room for. The body tube still has more than enough room to hold the recovery system.
Her third flight was with the B6 stack again and with the PerfectFlite microAlt 4600 altimeter in the new payload bay. The booster failed to separate, spitting the motor instead, and its motor mount tube got burnt away by the upper stage motor. Recovery was too fast for the payload, and the shock off landing caused the battery to jar loose long enough to reset the altimeter.
I did a few test shots with the sustainer with B6-6s while the booster was under repair with different nose cones in place of the payload bay to see how they affected recovery times. Note I did not say altitude; while the noses were vastly different in shape and may have affected altitude somewhat, they were also vastly different in mass and that affected recovery speed in a very unusual way. The lighter nose cone, a very long conical unit, had the shortest recovery at 28 seconds. The medium-length and -weight tangent ogive had the best time @ 40 seconds, and the shorter and heavier Alpha nose cone with about 7 grams of clay nose weight recovered in about 36 seconds.
The medium tan-ogive balanced the drag of the twin streamers with its weight perfectly, letting the body fall at or near its terminal velocity. Since it was tied to the nose with a length of shock cord, it fell nearly vertical, which lowered that velocity a lot, and the bird came down very slowly. The same effect can be had by attaching the shock cord externally at the body's balance point and bringing the body down vertically at any speed. The lighter conical nose let the body fall fins-down, and the heavier Alpha nose made the body orient fins-up, decreasing the body/fin drag and therefore recovery times as well. This was just for grins, though, and it did give me some predicted times to work with.
After the booster was repaired, I fitted her with a 12 inch Rogue nylon 'chute and reflew her on the B6/A8 stack twice with the altimeter. Both flights were failures; on the first, the booster spit its motor, the shock cord broke and the sustainer recovered without a 'chute. No damage was done, but the altimeter failed to register and repairs were needed. After replacing the elastic with a length of ¼ inch stuff and adding a snap swivel, I flew her again in the same configuration. This time, though, I mistakenly used an A8-3 in the sustainer, and ejection was very early. The shock caused the altimeter and nose cone to separate from the payload bay and free fall. The altimeter dropped its battery and may have further damage, but the bird itself seemed unharmed. The booster kept the motor this time, though the sustainer's did push out about half its length.
I flew her with the Alpha nose cone from the recovery times tests in a predicted duration event, but again failed to install the correct motor. The B6-4 I used caused an early ejection and she only spent 28 seconds in the air, a lot less than my predicted 35. I hope I can start picking the right motors and mounting them correctly, I really don't want to have to repair this bird again.
I did manage to do so on her next flight, which was the B6/C6 stack, her most powerful to date. Man, what a mover! She cocked a bit off the rod, but not seriously so. At staging, the booster took such a kick that it sailed off into the weeds a good 30 yards from the pad. The sustainer lit right away and flew straight and true to an awesome altitude. A great sky that day let me see that ejection was just past apogee, and her twin streamers let us track her all the way down. Winds were about 10 MPH, but she still landed a good 200 yards downwind despite her weathercock, and another rocketeer actually found her. Both motors were spit because I didn't friction fit them with tape. (It was darn cold and I didn't want to bother warming the tape in the truck, dealing with the goo, etc.) This may be the way to go, though; other than the spits, the flight was flawless.
Her eleventh flight wa a demo for my Model Rocketry class @ Live Oaks, and was on the B6/A8 stack. She spit both motors again, but did not eject the streamers, landed hard and popped the eye hook out of the balsa bulkhead. No damage otherwise, so I'll just do the standard repair.
| Statistic | Claimed | Actual |
|---|---|---|
| Length | 15.25 in. | 15.22 in. |
| Diameter | 0.976 in. | 0.976 in. |
| Weight | 1.4 oz. | 1¼ oz. |
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