Monday, January 03, 2011

Review: FAT BOI-NK

The FAT BOI-NK is a scale version of a popular fat rocket. The body is made from foam rubber and the fins from foam poster board. I wanted to build something out of a pool noodle for a long time, and this contest finally inspired me to do so. The FAT-BOINK employs the patented boink recovery method. This was my winning entry in EMRR's "NAMSROF" (National Assn. of Modified Stomp Rocket Flyers) contest.



Components
1. 12" section of a 2" diameter, pink pool 'noodle'
2. Small chunk from a purple noodle to plug the forward hole and provide color contrast
3. Foam poster board
4. BT-20 motor tube
5. Spent 18mm engines for a motor plug and forward ballast
6. Clay for ballast
7. A pair of Matt's rail buttons

Construction
The noodle came with a center hole that fit an 18mm motor - it was a natural! To shape the nose, I wrapped tape around a large drill bit until it fit very snugly into the hole in the noodle. With the drill clamped in a vise, I shaped the end near the drill while stabilizing the far end by hand. I used a piece of coarse sandpaper from a belt sander to remove foam until it looked about right. I made a fin template from my assembled Fat Boy kit, and included a ½" tab. The body was slotted to accept these tabs. An engine consists of a section of BT-20 and the nozzle end of a spent casing. I cleaned the nozzle and plugged it with just a dab of epoxy clay. Hey, sometime you gotta use what you have on hand. The nose weight was made from a spent engine filled with clay. I used epoxy to glue in the engine tube, the nose weight, fins, and the rail buttons. The foam plug in the end of the nose is pressure fit.

Finishing
The colors are basically the natural colors of the materials. I drew the F A T letters on the fins with a permanent marker and made a FAT-BOI-NK label on my OfficeJet. This is pinned on for show but was removed for flight.

Flight
Launch Report #1 - I chose a B6 for the first flight. The launch rail was tilted about 10 degrees to ensure it cleared the launch area. The boost was nice and the motor ejected near apogee with a loud pop. BOINK! The FAT BOI-NK bounced several feet in the air and came to rest unharmed. However, it appears that both rail guides were stripped off, along with a small plug of foam.

Launch report #2 - After adding a standard lug glued to a fin/body joint, I tried a C6-5. I used an Igniterman igniter and taped it to the engine (a mistake). The alligator clips didn't want to let go and the FAT BOI-NK flopped around on the ground.

Launch report #3 - Well, after the previous fiasco I double-checked the CP/CG relationship and everything seemed OK. So, I went to a grassy area near the house and tried again. The FAT BOI-NK is redeemed!

* B6-2 - nominal flight
* A8-3 - good boost, boinked prior to ejection
* C6-3 - nice high flight

The latest flight was on another C6-3 at MDRA's ESL-146. What's to say? It went up, came down, and BOINKED!