I was walking through a section of woods the other day and I found a bunch of piping that had floated down a nearby stream and washed up onto the bank from a construction site. I knew I could build something with it so I brought it back to my house. I noticed that there was a "Make it Fly" contest and I realized I could make a mortar tube to shoot custom water rockets.

Here is the list of materials:

- 4 by 10 PVC or some other similar material

- Lots of Duct Tape

- A 2 liter plastic seltzer or soda bottle

- A bike valve

- Plastic grocery or sandwich bags

- a nail

- A 4 - 5 inch diameter circular lid

- Dollar store plastic martini cups

- Styrofoam or plastic cups

Step 1: The Pokey Thingy...

Start by drilling a small hole into the end of the martini glass. Then insert a nail into the end and pull the tip through so that it sticks out 2-3 inches. Pour a copious amount of hot glue into the very end and completely cover the nail. After the glue has dried get the circular lid and glue the martini glass/nail onto it. After the glass and lid are firmly held by the glue, tape the whole thing onto the end of the PVC tube.

WARNING: Do not glue the lid to the tube because you might need to access the martini glass and nail later incase something breaks.

Step 2: The Stand

The stand is very simple. Just cut two boards until they are about 14 inches long and screw them together into a V. Then get a piece of PVC and screw the V firmly onto it.

Step 3: Finished Product

To assemble the mortar just put the stand against the mortar tube and tape it firmly together.

Step 4: The Mortar Shell

The mortar shell is just a 2 liter with a bike valve in the bottom and a hollowed out cap as the nozzle to direct the air and water fuel mixture when launched.

Step 5: The Seal

So to make the seal simply cut a 4 by 3 inch piece of thin plastic (i.e.. a grocery bag or sandwich bag) and fold it 2-3 times and place it on the top of the bottle. Then screw the cap down until very tight and you've just finished the perfect seal.

IMPORTANT: The number of times you fold the plastic changes the pressure the seal can handle. 1 to 2 folds can handle 20-30 psi, while 3 folds stays sealed at 40-50 psi.

Step 6: Loading and Firing

Loading:

To load the shell just fill it with about 1/4 to 1/2 cup of water and place the plastic over the opening of the bottle neck. Then screw the cap down very tightly. Go outside with a bike pump or compressor and fill the shell with 20 - 50 psi. After pressuring the shell place a styrofoam or plastic cup over the bike valve to protect it when the shell hits the ground.

Firing:

To fire just drop the shell down the tube and onto the nail, which punctures the plastic seal, which in turn launches the shell into the sky. The max range I have tested so far was over 175 feet.

P.S Vote for me in the Make It Fly and First Time Author Contest if you liked my intractable.