The Texas Firefly is a gap staged 18mm kit from Semroc. This kit exemplifies everything I love about Semroc: high quality, wide selection, low price, outstanding customer service.
The rocket stands 14.3in and 1.34in diameter (ST-13 is slightly larger than BT-55 tubing). The total weight is 2.1oz.
The assembly is so utterly straightforward that it hardly merits description. The instructions were flawless: clear, detailed, and completely unnecessary given the elegance and simplicity of this design.
The booster motor mount is standard except that the centering rings have holes cut throughout them to allow rear venting of ejection gases to facilitate the gap staging. The sustainer motor mount is standard, with Kevlar® string attached for the recovery device.
The fins are laser cut balsa. I beveled these to a symmetric airfoil shape and sealed with Elmer's Fill 'n' Finish, which was also used to fill tiny tube spirals and the balsa nose cone.
The tail nozzle is a double wrap of stiff paper. This was not sturdy enough in my opinion. I gave it several coatings of CA on both inside and out to achieve better stiffness. I also omitted the rods on the fin tips because I didn't want to be constantly repairing them.
Two heavy washers are affixed to the nose to ensure stability with all those rearward motors. The chute is a standard tiny plastic Semroc style.
I finished mine in purple and gold and used most of the waterslide decals. The decals went on without problem except that some darker ones didn't show up too well against dark paint. Wal-mart clear spray paint went over the top of everything.
Construction Rating: 5 out of 5
The first launch was on a beautiful day on the prairie with only a slight breeze. I suspect that B6-0/C6-7 motor combination would be an ideal motor combination for this kit. Unfortunately, I'd used up my cache of B6-0 motors. Thus, I tried the slightly unusual combination of C6-0/B4-4. It seemed like the only reasonable combination available at the only hobby shop open the morning we drove to the launch. I figured that the relatively slow-burn B4 would partially compensate for its short delay. I was afraid of losing the rocket with a C to C motor combination because it is so light. (Semroc projects 1650 feet on a pair of C motors!)
The Texas Firefly buzzed off the pad on the C6-0 booster. Boost was absolutely straight and stable. With a loud pop the booster separated. Staging was perfect and the flight path continued straight with the sustainer. The sustainer absolutely ripped through the sky on its B4.
I took my eyes off the sustainer for a moment to check on the booster. It was tumbling downward with the most amazing tumble action I had ever seen. The booster was spinning blurringly fast and gently settled to the ground without even a scratch. What a fabulous design!
By the time I scanned upward with the binoculars again, the chute had opened. I think ejection was about right, perhaps a bit early. In the warm prairie air, the sustainer drifted around for several minutes before touching down in the grass next to a cactus in bloom. No damage. The rocket and booster were in mint condition and ready to launch again.
Flight Rating: 5 out of 5
This kit would be an excellent choice for anyone trying their first 2-stage kit. It is easy to build and introduces the gap-staging concept. The parts are high quality and fit together seamlessly. It is also easy to fly on almost any 18mm motor combination with the motors popping easily in and out of separate tubes with motor hooks. For skilled builders who think they've done and seen it all, the Texas Firefly is also a great choice, because you can admire a kit so clean and elegant in its concept and execution that it is a real joy to build and fly. A classic!
Overall Rating: 5 out of 5