Brief:
I designed the "Cosmic Thunder" as essentially an ARF 2-stager to entice my wife into completing her NARTREK Bronze. It merges the Quest Thunder ARF as the sustainer stage with the 2-piece glue-together fin can of the Estes Cosmic Cobra to yield a nifty and cool looking 2 stage model that is ready to fly as shown in the photo in 10 minutes from the boxes.

Modifications:
All that is required for the Cosmic Cobra fin can is to assemble it according to the directions -- omitting the entire rest of the rocket (hey, the parts will come in useful for other projects). I used 5-minute epoxy to glue the two halves together.

The fit between this component and the Quest Thunder aft end is amazing -- needs only a couple of wraps of masking tape to make it a perfect fit. A real bonus is the screw-lock motor retention system Estes provides with the kit. It is perfect for 2-stage loading. The Quest Thunder fin can is not glued to the body tube, and it can be slid back to make the fit even better once the taped together motor assembly is loaded. See attached photo.

Construction:
The Cosmic Cobra fin can fits into the aft section of the Quest Thunder like it was made for it -- perfect fit. All that is required for the Quest Thunder is to snip off the motor hook, and to glue on (5-min. epoxy) a 3/16" launch lug tube 1" above its plastic fin can.

The only thing additional thing you need to do is to dab some 5-minute epoxy around the aft motor ring of the Quest Thunder sustainer, for added strength -- it seems to be attached at the factory with only a little hot-melt glue. And..you're done! Cosmic Thunder is ready to fly.

Flight:
Flight is really only satisfactory with a C6-0 as the booster, but a variety of motors are possible in the "Thunder" sustainer. First flight was with an A8-3, and it partially tore the 18" Estes chute I used, due to early ejection. A B6-5 or C6-7 is the perfect sustainer motor for Cosmic Thunder, the latter giving a straight up and nearly out-of-sight boost to about 1400-1500 feet. I used a 14" LOC chute on later flights.

Summary:
This is one neat 2-stager, about the only "near" ARF (almost ready to fly) on the market (the two components, that is). The forward swept booster fins look cool (I think) and the thing is a little easier to see than a Mongoose or AZTEC in flight. And if you lose it -- hey, its an ARF, you're only $20 and 10 minutes work from another one.