Naturally, then, when I started building a fleet of smaller bulbous rockets, a scaled-down version of The Rocket Formerly Known as Black couldn't be too far down the trail.

The first venture into the creation of a bevy of diminutive yet curvaceous beauties (yes, I did just apply that description to a rocket) was the spectrochromometrically disappointing Haliburton Marauder. I really like that rocket despite the unsatisfactory and substandard paint color. It was created from the pod molds that I created for the ill-fated DAJAT. If you want to learn more about those two projects, just follow the links.

Here is a photo of the complete TRFKAB 5.5, and the Haliburton Marauder lounging poolside. They both have a maximum diameter of 5.5 inches. The Haliburton Marauder is a rear ejection design which deploys a parachute by ejecting the entire motor mount assembly out the back of the rocket. TRFKAB 5.5 uses a traditional forward ejection with a removable nose cone.

As with any design, I start with creating a RockSim simulation. Funny thing - when I went to create the 5.5" version of this design, I found that the RockSim file already existed. I still can'r remember creating it, but it must have been around the time I was making DAJAT and I was curious about finding other uses for the pod mold.

Step One:
Glue together enough poplar to create a solid block.

Step Two:
rough cut away the excess on a bandsaw

Step Three: Mount the block on the lathe and remove the corners

Step Four: Continue to remove anything that does not look like a nose cone

Step Five: Take a picture next to a measuring tape.

Step Six: Sand, prime, and paint.

In most circumstances the work on the nose would be done at this point. However, I thought I might want to make more of these in the future - not as complete rockets, but perhaps as kits for my brothers or nephews. So I made a rubber mold. This allows me to cast them easily out of resin.

The RockSim simulation indicated that a farily significant nose weight would be required, so I hollowed out the shoulder with a 1.25" Forstner bit. I then drilled a 3/16" shoulder at the forward end of the shoulder and tapped it out with a 1/4" 20 threads per inch. I also recessed the location for the 1/4" nut.

I then stacked 1.25" fender washers on a 2.5" x 1/4" eye bolt. The advantage of the fender washers is that you can add or remove them as needed to balance the rocket.

After boring out the shoulder once, I realized just how much material I was wasting by casting a solid nose. So I later added a third part to the nose mold which gives me a hollow shoulder at the time I cast the part.

There was a second, unanticipated benefit to modifying the mold in this way: The hollow base also reduces the shrinkage of the curing resin, so the nose fits better when it comes out of the mold.

Notice the tape wrapped around the shoulder - the first parts I cast did not fit very well. If you look closely at the coloring of the resin part, you will notice that the upper tip is much lighter in color than the base. As the epoxy cured, the resin in the thicker section generated significantly more heat, which causes the darkening in the thicker section. I suspect is also the reason for the shrinkage. The parts I have cast with the hollow base are more consistent in coloration and also more consistent in size with the original part.

Speaking of the pod mold, here it is. In this case, the airframe mold.

I've tried many times to join the two halves while they are still in the mold, but it is not a simple process. Since I intend to cut the tips off anyway for these designs, I've found it is easier to remove the parts from the molds and use packing tape to temporarily hold the two halves together. I then join the two halves by applying 1" fiberglass tape to the inside of the joint.

First cut a piece of the 1" tape to length and roll it up tightly. Then I paint the joint with resin and unroll the tape along the joint, wetting the tape with more resin as I roll it out.

One of the most difficult (and critical) steps in making a bulbous rocket is marking straight lines along the curved airframe that are parallel to the center line of the rocket. There are no reference points to rely on, which makes it very easy to get a line crooked. Since these lines are used to align and cut the fin slots, a crooked line can result in a flight disaster.

I've tried of number of different techniques with varying success - everything from carpenter squares, improvised templates, and laser beams. With this project I decided that it would be better in the long run to just make a jig that I can use to clamp the airframe in place and draw straight lines in a repeatable fashion. This will be especially handy if I make more of these rockets or create kits of these rockets in the future.

To the right is a photo of an airframe inside the jig. The fin slot lines are drawn on with red Sharpie. If you are looking at the black line - no, I wasn't drunk when I drew it. That is the outline along the edge of one of the pieces of fiberglass cloth I traced and cut in the process of making the airframe.

I've found that the jigs and molds are really what make these particular designs possible. Unfortunately they take up nearly as much space as the rockets themselves -- and as I have documented before, storage space at my house is at a premium.

Once the fin slot lines are drawn on the tube, there is a very important sequence of building steps to be followed:

1. Carefully trim both ends of the airframe to tightly fit a 54mm phenolic tube.
2. Cut a 54mm tube to 14" (this is slightly longer than the bulbous airframe, but there is a reason for it).
3. Mark the 54mm tube for three fins and a launch lug. The fins are 60° apart, and the launch lug line should be 30°, midway between two fins.
4. Epoxy the launch lug in place. I use a 5/16" aluminum that runs the entire length of the 54mm tube, 14" long.
5. Cut a 1/4" slot in the aft edge of the airframe to fit the launch lug. I use a Dremel tool, and I like to put this slot right on one of the two seams. Obvously this takes some care and skill, and it is easy to make the slot too big. I've done it. But I was able to easily repair my mistake with a slurry of epoxy resin and milled fiber filler, so it really wasn't a big deal. In fact, there will be a gap (small or big) no matter what, so there is always a space to fill
6. Slide the motor mount into place, aft to forward, until the edge of the launch lug butts against the inside of the frward airframe, all the while carefully aligning the fin lines on the motor tube with the fin lines on the airframe. Mark and cut the slot on the forward edge of the airframe.
7. Insert the 54mm tube inside the airframe, but don't epoxy in place until completing step 8.
8. This step requires careful alignment. With the nose in place inserted into the forward end of the 54mm tube, it is important to visually align the profile of the the nose curves with the profile of the airframe. There will be a gap at the end of the airframe to the edge of the 54mm tube that will be filled with epoxy or filler putty in order to create smooth, continuous curved transition between the airframe and the nose cone (see the illustration to the right, with arrows pointed at the gap to be filled). I take care to mark the final aligned position, then remove the nose and epoxy in place.

Once the 54mm tube is epoxied in place it is time for the filler. I use Elmer's Wood Filler because it ie easy to sand - and once the sanding is complete it can be treated with thin CyanoAcrylate for a rock-hard cure.

As shown in the photo, I put the nose in place, filled the gap with the Elmer's Wood Filler , then sanded it smooth.

In the spirit of conservation and to reduce my carbon footprint in my own personal battle against catastrophic climate change, I am recycling these next photos from the build of the Haliburton Marauder.

These are here to show how the launch lug is trimmed to blend into the airframe, both front and rear, then filled and sanded. As noted earlier, I align this with one of the airframe seams, since the seam needs to be filled and sanded anyway.

I used the same fin pattern as the full-sized TRFKAB and scaled it down. In fact, these fins are made pretty much the same as the full-sized fins with the exception of the materials. I used a 12 x 24 piece of 1/8 Birch plywood. I had to cut a total of nine pieces to make the fins, since the fins were constructed just like the big TRFKAB 3 layers. (The center layer is the fill-size piece, and the two outer layers are the smaller pattern.)

The fins are 3/8" thick once glued together. I did not glass my and they are plenty sturdy as-is for a midpower rocket. If I think about it, they could be a little thicker and still look cool. Sort of like how Muppet babies are squattier than just a scale-down of the adult version.

I used a 1.25 Forstner bit to cut the fin hole(s). When I got done they looked so cute. Like dollhouse furniture.

To install the fins, I measured the locations carefully (the distance from the base) and slotted the airframe along the predrawn lines with a Dremel. The fins are inserted through these slots and the root edges epoxied to the lines drawn on the 54mm tube. I used my airframe jig to secure the fins in place while they cured. This worked pretty well - at least as well as the fin alignment jigs that I used [HERE!], or [HERE!].

You can't get much simpler than this for a motor mount. A 29mm tube and a couple of centering rings.

The motor is retained with a screw and some screen door parts from Ace hardware.

In the photo you can also see the way the launch lug blends into the airframe.

The shock cord mount is picture hanger hardware, also from Ace Hardware. Read more about it [HERE!].

The first flight was on January 08, 2011 at Rainbow Valley, AZ. It flew beautifully on a G-64 White Lighning. Happily, this little runt flies just like its big brother. Very fun to watch!

Click [HERE!] for video of TRKAB 5.5's first flight! This was shot right next to the pad with a wide-angle lense - so the illusion is that it loops off away from the camera, when actually it was a very straight ascent.

(special thanks to Jasper Nance for the video!)

This rocket was the third of its kind - a 5.5" diameter bulbous rocket made from the molds I originally created to fabricate the pods for DAJAT. The first was the Haliburton Marauder, built by me, the fourth was the Dingleberry Shenanigans , also built by me, and the second was the Martian Maggot, built by my brother Mark (held below by his son Eli). Do me a favor and hold your breath until he creates a web page for it.