Want to launch tennis balls (or other similarly sized objects) at your friends? WITH SCIENCE?

Well, throughout history, people have been using a weapon called a staff sling to launch rocks, projectiles, and even grenades at their enemies, and it can easily be put to social responsible use keeping people entertained by launching tennis balls, water balloons, event t-shirts, or for other fun activities. A staff sling is incredibly easy to build, and can double as a walking stick.

Step 1: Materials and Tools

The materials for this project include:

-Two lengths of rope or paracord approximately 3 feet long

-A wooden dowel one inch in diameter and approximately six feet long

-A piece of fabric for the pouch measuring 8 x 5 inches. Denim, canvas, and leather are good choices.

-tape

-Water balloons

These tools are recommended to make the project easier:

-scissors

-ruler

-screwdriver

-pocketknife

-lighter

Step 2: Preparing the Cord

Cut two lengths of cord that are 3 feet long. If you choose to use synthetic cord such as paracord for the sling, I highly recommend melting the ends to prevent fraying. Use a lighter to heat up the end of the cord until it melts. Do this in a well ventilated area so that you don't need to breath the fumes.

Step 3: Creating the Pouch

To make the pouch for the sling first start with the chosen fabric and cut it to the proper dimension. Then fold the corners of the fabric over to create a diamond shape. Use scissors or a knife to cut off the corners.

Step 4: Finishing the Pouch

Next, use a knife to cut a small hole on either horizontal end of the pouch. The holes should be about 1 inch from the very edge of the fabric, and should have a diameter just large enough to pass the paracord string through. Finally, fold the pouch in half and tape the folded corners. This forms a cup when the pouch is open.

Step 5: Stringing the Pouch

Tie each length of cord through the holes in the pouch. Use square knots for an easy yet secure lashing.

Step 6: Stringing the Staff

Tie one cord of the sling to the staff about 3 inches from the end. Use a bowline knot for strength and resistance to slippage. Tie the cord of the opposite side above the first knot, but loosely. Tie the knot such that there is room to slip a pencil with the staff.

Step 7: Using the Staff Sling

A staff sling is used like a human powered trebuchet. After the tennis ball is placed in the pouch, swing the staff vertically from behind your body. The top loop of cord should detach at swing apogee, launching the ball a far distance. Enjoy!