Public Enemy Ultra FatBoy (3)

Public Enemy - Ultra FatBoy (3)

Contributed by Dick Stafford

Manufacturer: Public Enemy
Rating
(Contributed - by Dick Stafford - 10/15/00)

Rocket PicBrief:
The 3" Ultra Fatboy was my first high power rocket and was purchased for my TRA Level-I certification. I picked this kit primarily because of its sleek design and capability to fly on mid-power motors (adapter not included). There are quite a few rockets fitting the latter requirement so looks were the major factor. This kit turned out to be easy to build and extremely tough. Although the 3" Ultra Fatboy is no longer in production, Public Enemy still makes a 4" version. I'm sure if you like what you read here, you will be happy with that kit.

Construction:
The airframe and motor tube are both paper. The four fins are plywood and extended through the airframe, the shoulder of the plastic boat-tail, and to the motor tube. Three fiber-board centering rings are provided. I don't know if I'd want this material on a large diameter kit but they worked fine in this application. The nose and tail cones are heavy-duty plastic. The recovery harness consists of a 2' section of flat nylon strap that is epoxied to the motor tube behind the forward centering ring. A 15' length of bungee is tied to a metal ring on the nylon strap and to the nosecone. The two 3/8" copper launch lugs are pre-cut at an angle. I don't remember the size chute that was provided as it has been assimilated into my range box. I remember thinking it was too small so I replaced it with a 36" chute from Giant Leap.

The instructions came on a single sheet but were sufficient for an experienced mid-power builder to follow without too much difficulty (hey - it was double sided). Being short and stubby, this rocket needs a lot of nose weight to fly safely. This was very clearly marked on the instructions and the CP/CG locations were provided. This was a big plus for the novice high power builder. As recommended, I filled the space between the motor tube and the tail cone with foam. This was a mess but ended up fine. The provided CP was at 22.75 inches. When run on Rocksim, I came up with 21.12 (Barrowman) and 22.25 (Rocksim). Being new to high power, I added resin, lead, nuts, bolts, etc. to the nose until I got the recommended one caliber of stability from the worst case figure of 21.12". I assumed the largest motor I anticipated using, an I211.

Finishing:
I simply gave it a coat of Krylon primer and 2 coats of a purple Krylon that I got on sale at the local hardware store. The kit came with lettering (Fatboy) and I added its name "Mini Mojo" which I cut out of silver metallic trim.

Construction Rating: 4 out of 5

Flight:
The recommended motors were basically any of the AT RMS 38 mm up to the J350, although the latter might require added reinforcement that I didn't provide. I used a Nomex® pad from Giant Leap in place of wadding and installed threaded bolts in the rear centering ring. I fabricated a motor retention hook from a coat-hanger and terminal lugs (normally used to terminate wire). My rocket flew twice on G80's and once on an H242-M for my Level-1 cert. The G80-7 makes for a relatively low, but straight flight. On the H242, it really moved out, with a predicted altitude of 2824'.

Recovery:
With the large amount of nose weight, my Mini-Mojo Fatboy weighs in at ~40 oz. It has recovered nicely from each flight. As mentioned earlier, I opted for a slightly larger chute than that which was provided. With the foam-filled boat tail impacting first, however, it would be hard to damage this tough little rocket. There is only one CON that I see. Although the provided bungee has survived several flights, it would probably be a good idea to replace it with tubular nylon.

Flight Rating: 4 out of 5

Summary:
This is a good looking, tough rocket. Its construction is straight-forward. As with any short high power rocket, you must be careful to add enough nose weight to make sure it is stable. If this one is damaged, eaten by trees, lost, etc., I will want to replace it with the 4" version.

Overall Rating: 4 out of 5

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