i made this rocket to use with the 12mm aluminium nozzle and closure i'd made,
and the mini paper-case motors it had spawned. i collected likely-looking stuff i had
lying about, including some fairly thick-walled PVC conduit, various seedling punnets,
a cat food tin and a stick that fell off the tree outside the shed. i decided to make it
different to my first one - popping apart in the middle instead
of at the nose. it would have 4 fins, a long nosecone, and be completely water-compliant.
the nose was fashioned from a piece of eucalyptus, drilled and pushed onto a metal rod, then turned in the drill press. after having a square bar clamped in the vice and the table rotated 90 degrees, it functioned as a vertical wood lathe.
the fins were thin, blue HDPE plastic from a rectangular seedling punnet, the outside stippled and the inside glossy. i cut them to a random but likely-looking shape and glued them into slots hacksawed into the end of the lower body tube with 5-minute epoxy, the type that smells horrible. as an afterthought i secured the tail of the tube with a short piece of PVC from the flared joiner-end of the conduit. the cat food tin formed a strong, minimal-thickness joiner between the two fuselage sections, glued to the top section and forced out of the bottom one with a little tethered piston. the overall design was similar to Richard Nakka's "SkyDart", if it was built by Hardie-Dux instead.
this is the tiny motor, with an outer diameter just smaller than the rocket's inner diameter. the casing was standard manila folder card, and the propellant was carefully formed inside a pre-made newspaper-and-epoxy inhibitor tube and cut into 3 roughly BATES-sized grains. i didnt bother with the delay grain inhibitor, i just glued it directly to the casing the same as the header and nozzle. im pretty proud of how well it went together. planning roxx!
the layout as shown below was arrived at by throwing the chute, attached to spanner, as high as i could and seeing how it unfurled. then i tried packing it, putting the fuselage together and pulling it apart again, waving the ends around at arms length to see how well it came out and opened. such a thin fuselage required the chute to be packed very tightly so that it would fall out easily at separation. then a positive release was required for the taught chute wrapper >< and i never got that bit really sorted, but just decided to light it up anyway =)
a comparison of the two rockets, both with motors and chutes awaiting launch. and some bananas, mm bananas.
it was launched on the next suitable day, after realising the tidal mudflat i've walked,
rode and driven past for 10 years, but never ventured onto, was at least 300m across and
therefore a perfect missile range. except for the sinking sand, the mudcrabs, and the damn salt water.
and my bro barely caught the liftoff because he was screwing around as usual.
oh well, he got this much:
though you cant see much, i estimated the altitude from the fall time to be about 60m. which is seriously not too bad for a first go, small motor, heavy rocket, miscellaneous excuses etc etc.
the ejection charge didnt fire so the front end dug deep into the sand, and then the booster end bounced off the coupling, bent it a bit, and plopped onto the sand.
but most annoyingly, the motor burnt through its casing just ahead of the nozzle, and torched a matching cavity straight out the side of the fuselage and through a fin.
could this be the beginning of the end for paper casings!? or just the end of the beginning!?!?
its the beginning of the end, as it turns out =(. this rocket will only be getting shorter once.
[GO BACK TO INDEX.HTML]
im a photographer, i have a lot of pictures to show you ok?