Brief:
Unique tube-launched rocket with folding military surplus fin can.

Construction:
I had always wanted a FlippiFin -- the concept seemed interesting. I got one for my birthday a year ago, and only recently got around to building it. The components were basic Estes (plastic nose cone, paper body tube), with the exception of the recovery system and the unique folding fin can, which was military surplus. A nice waterslide decal was also included. For recovery, Bob supplied a generous length of fiberglass-reinforced Teflon for the shock cord, a length of Kevlar® to secure it to the motor mount, and an 18" military surplus chute to round out the theme.

The instructions were printed on two sheets of 8.5 x 11" paper, and were somewhat minimal, although this rocket was very easy to assemble. Two centering rings are installed onto the front of the 24mm motor mount, and two more centering rings must be built up out of masking tape to attach the fin can. You slide the fins on, and then everything is glued in place. I used 5-minute epoxy and carefully watched it cure to make sure none got in the delicate hinge assemblies. The shock cord is attached to a hook on the fin can with a Fisherman's knot, and the whole shebang is installed into the main body tube. A unique option was presented: simply friction fit the fin can into the tube, allowing for easy shock cord replacement. I elected to do this instead of epoxying the unit in. Finally, an anchor is bent out of a paper clip and installed into the nose cone, along with lead shot for balance weight. I added some PML expanding foam behind the shot for a little G-force protection.

Finishing:
I finished the rocket with one coat of Krylon white primer, and then proceeded to paint the rocket in Krylon gray and red. One thing about finishing is that you need to be careful not to get any paint in the hinges on the fin can. I colored the exposed motor tube black using a Sharpie pen. The waterslide decal completes the look.

Construction Rating: 4 out of 5

Flight:
The recommended motors were single use Aerotechs, none of which I had on hand. I instead elected to fly one of my year-old F24Ws. I built the motor and tape fitted it in tightly, not wanting to lose my precious case. Positive motor retention would be a nice feature. I loaded the front end of the rocket with wadding and the chute. It was a tight fit, but all the recovery did slide in. I strutted out to the pad and inserted the rocket in the breech launch tube. I constructed a special launch pad for my breech tube because I wasn't comfortable with just sticking it on a 3/16" launch rod as suggested in the instructions (though that would probably be fine). After hooking up one of my Igniterman igniters, I walked back to the range head and told the LCO to push the button. He gave a huge buildup and countdown, and hit it. The motor chuffed once. Twice. The third chuff was enough to send the rocket out of the tube, and then combustion stopped again. I thought the rocket was going to tip over and go into the crowd, but just as it was falling back down, the thing screamed into the sky, with a little wiggle. It looked very much like a cruise missile :). The chute ejected at apogee, and I went to recover it.

Recovery:
Descent was a little fast on the 18" chute, but no big deal, there was absolutely no damage. All I had to do was wipe the rocket down to get rid of the breech soot and it was ready to fly again. Too cool.

Flight Rating: 5 out of 5

Summary:
This rocket was easy to build and unique. The only problem that I have with it was that it has no positive motor retention, so I might lose my precious 24mm case. However, I would not hesitate to recommend it to anyone. Just make sure you have a nice hot igniter and scratch up the grain a bit if it's an old motor :) I'd love to fly this again on an F39T.

Overall Rating: 4 out of 5