...So I made this rocket over the past few months, all while procrastinating on joining this forum.
Inspired by a finishing move from the anime Tengen Toppa Gurren Lagann, I decided to make an oddroc with the form of a spinning conical 'drill' which would be powered by a pair of canted green Aerotech G76 motors. It would have a hole through the center, allowing it to spin about a 1/2" rod when launched, and I wasn't sure how to recover it.
I figured this would be horribly unsafe, so I shelved the idea for a month until I realized that I could write a simulation for it, and even use that as a final project for one of my college classes. So, I started going through designs, trying to figure out how to get the rocket to eject a parachute large enough to support it, without risking tangles caused by the separation of two spinning parts.
I eventually selected rear-ejection: the motors sit diagonally in a 4-inch phenolic coupler tube that is 7 inches long, which contains a baffle system to prevent burning particles from poking holes in the parachute. You can see the internal structure here:
If you're wondering why the spin induced by the motors is in the opposite direction of the flutes on the drill, don't complain to me: they animated it that way. Also, on its first flight, I put some dog barf in just in case, and I plan to keep doing that. Better safe than sorry!
This slides into the body of the rocket, which is underpinned by an 11-inch-long piece of 4" tube, and has "centering rings" (I don't know if you can call them that) around it creating the conical profile of the rocket. At the front, inside a centering ring, is a 29mm phenolic tube that seals with the aluminum tube from the motor canister, preventing ejection gases from exhausting through the launch lugs in the top and the bottom. That centering ring has another pair of eyebolts matching the ones on the motor canister, to one of which the shock cord is tied. (Both are there for balance).
That leaves a donut-shaped space around the 29mm tube for a parachute to go, so I purchased a 48" Spherachute, which fit perfectly into the space available along with Kevlar shock cord, and matched the expected 5.5 pound weight of the rocket.
At the nose, I have a piece of nylon with a brass tube (.5 inch ID for a launch lug) press-fit into a hole bored through it, and the nylon was turned on a lathe to fit into the 29mm phenolic tube and have a conical surface lining up with the rest of the conical shape of the rocket.
For the skin, I epoxied two pieces of posterboard around the rocket, forming a conical surface. On top of this, I put a layer of 4-oz fiberglass, 2mm aero-mat (http://www.acpsales.com/Aero-Mat.html) foam for thickness, then two more layers of fiberglass. This I painted green and silver to match the Giga Drill Breaker concept that inspired the whole deal, and was finally finished.
Obligatory non-standard "dumb rocket picture":
I launched it at the February 2012 ROC launch, which was terribly windy, but I would not be stopped from launching my new rocket.
Well, here's how it went: