Manufacturer: | Scratch |
Brief:
I finally got around to building a Halloween themed rocket. This one
flies on two 24mm motors and is night-launch capable.
Construction:
The parts list:
I started by cutting a hole in the bottom of the pumpkin to fit a 2" tube. Because I wanted to make this night launch capable, I installed a piece of 2" clear mailing tube in the pumpkin. It hangs about 2" out of the bottom and is attached to the inside top surface with Gorilla glue. A short section of cardboard tube telescopes over this plastic tube and is attached with 2 small screws. These are actually hex standoffs -- I thought this gave it a 'Frankenstein' head bolted-on look. I made the shoulder out of a piece of the telescoping cardboard tube, a plywood bulkhead, and an eye-bolt. This too is held together with standoffs, which make the inside accessible so a lighting device can be installed. In fact, here is the cone section with a laser pointer installed as a demo (see picture). Finally, to accommodate the launch rod, I inserted a piece of Apogee 10.5mm tubing through the pumpkin. I decided on the tubing instead of just open holes since I wanted all the photons to come out of the jack-o-lantern face.
The motor mount is two pieces of 24mm tubing glued together. This pair slips nicely into the mailing tube. I made foamboard centering rings to keep the ejection charge in. These are more like half-rings since the motor tubes touch the inner wall. The upper surface of the top ring, and the bottom of the lower ring were covered with a thick layer of carpenter's glue.
I recycled a section of bungee from my now resurrected Public Enemy 3" Ultra Fatboy. This was epoxied to the inside of the tube just above the motor mount. To provide some protection, I glued in a small piece of car airbag material to cover the bottom four inches or so. I've never done this before but have a lot of odd scraps of this stuff.
The fins were inspired by the Rocket Team Vatsaas' Halloweener. They are foamboard trimmed with bamboo skewers. The skewers were covered with light spackling and a little Elmer's Fill 'n' Finish.
Finishing:
I left the surface of the fins quite rough. A bat's wing isn't that smooth
after all. The whole thing was covered with a coat of white primer and then
painted with Rustoleum black paint.
Does carving the pumpkin count as 'finishing'? The carving was actually performed at the start of the build.
Flight:
I friction fit the D12s, packed dog-barf wadding, and used the 18" nylon
chute from my
Semroc SLS Sky Hook. The winds were gusting to 15mph or so and there was a
little weather cocking. Ejection was just a little late. I will probably try a
three second delay on all but calm days. Unfortunately when it's that windy,
the rocket is more likely to land on its fins, even if they are swept forward
like the ones on Gone Batty. Two of the foam fins suffered some minor
damage.
Summary:
I have always loved this type of rocket but never found a foam jack-o-lantern
that was both on sale and looked the way I wanted it. The carvable pumpkin from
Michael's fit both these criteria (of course I had to make it look the way I
wanted it). The hollow pumpkin also had the advantage of being convertible for
night launches. I may actually make a flight at our club's next night launch!
The fins were easily fixed by filling the cracks with white glue. On one side of each, I spread the crack and worked in the glue. On the opposite side, there wasn't so much a crack but a buckle. I opened this with a hobby knife and filled the resulting gap with glue. In the morning, they seem as strong as the others. Some touch up paint and Gone Batty is good to go.
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