Ya,
When I was 12 I built a rocket launcher out of some fencing tube I found in an old lot, all I had to do was attach a battery and switch. I used model rocket engines on custom lighter cardboard tubes and plastic spring out fins; shit would shoulder launch a rocket to about 1500 ft, and then it would parachute back down (or perhaps other, louder things, not involving m-80s of course :-).
12 was good times, and fencing is some useful stuff.