This was an enormous success. The darts now go 300-450 feet in the air. That's twice the published distance that the commercial Stomp Rockets (R) go!
Warning: this contraption can be very dangerous. Do not point it at anyone or anything you care for. The tips of the darts usually crumple upon impact with a hard surface, but can still go through cardboard and leave welts on skin. I am not responsible for damage resulting from or relating to the use of this idea.
Step 1: Gather Supplies
2 to 8 ft of 3/4" PVC pipe for the barrel. 2ft makes the dart go much slower than 8ft. Pictured is 4ft.
6 inches to 2 feet of 3/4" PVC pipe for the horizontal air pipe. Pictured is ~8in.
1 3/4in 90 degree elbow (PVC)
1 small paper bag, which forms the base for the stomp pad.
Several sheets of scrap computer paper (one for every dart you want plus one for the pad).
Masking tape, for the darts.
Duct tape, for reinforcing the stomp pad.
For choosing the barrel length:
2' shoots about 150ft up.
4' shoots about 300ft up.
6' shoots 350-400ft up.
8' shoots even higher.
Keep in mind that these heights are derived from measured hang times and the simple d=v*t-1/2g*t2 equation from Newtonian physics. They don't account for air resistance, and therefore are not completely accurate. They give a rough estimate.
Step 2: Apply First Layer of Duct Tape to the Bag
Step 3: Tape the Short Side of the Bag
Multiple layers of duct tape may seem silly - but believe me, they are necessary to keep it from ripping.
Step 4: Tape the Edges
Step 5: Add the Second Layer to the Sides
Step 6: Begin the Taper
Step 7: Finish Taper With Paper Cone
Add four pieces of tape starting an inch onto the pipe and ending three inches onto the bag. Add short cross pieces to cover the the remaining exposed paper and reinforce the taper.
Step 8: Launcher, Final Assembly
Step 9: Making the Paper Darts
Using this triangular shape, begin rolling the dart. Keep it very thin. At the half-way point, carefully insert the large end of the dart into the barrel. Relax your grip a bit the big end unrolls to fit snugly into the barrel.
Continue rolling right onto the tape. To finish up, trim the end of the dart until it slides smoothly, by gravity alone, through the barrel.
Step 10: Launch!
Make sure everyone is clear away from the business end and then stomp as hard as you can (with both feet) on the stomp pad. You have to hold the barrel upright while doing this. Make sure you are looking up - otherwise, you are likely not to see it go up and up and... out of sight. 5-15 seconds later (depending on ferocity of stomp and barrel length), there will be a thunk, and the dart will come down. I have only once spotted it on its descent.