Originally this design was created for in-house use only. I work as a tech lab program lead for a youth center on the army base where I grew up. I teach science and technology and do assorted projects with middle school and high school students. When I first got started at the center I had missed the deadline for requesting materials and such so I had to be a little creative for those first few weeks. This was one of the projects I came up with on the fly.

I knew that I wanted to do a series of catapults with the kids but we didn't have the supplies on hand for the more advanced designs. This project was the result of a day's worth of trial and error. The only supplies I used were the ones I had on hand and the rubber bands I used even had to be scrounged up from other programs' supplies. I was surprised at how well it worked and the kids loved them.

So far we have successfully run the program with my older kids as well as the elementary age kids at one of our other centers. It takes about fifteen to twenty minutes for me to make one and about forty-ish minutes for the kids. (And if a project can keep a middle schooler's attention for that long you know it has to be good!) It takes longer depending on the size of the group, too.

Okay, on with the instructable!

Step 1: The Supplies

As I mentioned earlier, the supplies I used were just random things I could collect around the center. Customized pencils were in abundance and I was able to collect enough rubber bands to piece it all together. The only thing that needed to be bought for the project was the rubber bands since I had used the few we had on the prototypes.

You will need:
• 12+ rubber bands (three of which must be the same type)
• Duct tape for making the pouch
• 7 pencils
• Scissors (not pictured)
• Ammo (not pictured)

Step 2: The Base

The first part of making this slingshot catapult is the base. It's fairly simple to do. All you need to do is make a triangle out of the pencils.

You need to take:
• Three pencils
• Three rubber bands

You will take two of the pencils and use the rubber band to bind them together. A crisscross sort of pattern works best. Wrap the the rubber band tightly so the pencils don't slip. You will then repeat this step twice more to bind all three pencils together in a triangle shape. You will want to make a sort of cross bar at the front of the catapult so make sure to appoint one pencil as the "front pencil." You will want to make sure you bind the other two either on top of it or below it. It doesn't really matter if you put them on top or on bottom of that front pencil. Nor does it matter which of the pencils is on top when you bind the two support pencils together to finish the triangle.

Once you have successfully made the triangle you can move on to the next step.

Step 3: The Frame - Part 1

The next step is to create the first part of the full frame for firing.

You will need:
• Two pencils
• Three rubber bands

First you need to take one of the pencils and place the end of it between the two ends of the pencils on one side of the front of your base. You will then take a rubber band and wrap it around this new pencil as well as the other two. If you have a limited number of rubber bands or did not wrap the pencils on your base together tight enough you can instead pull the rubber band and squeeze the third pencil end in with the other two ends.

Repeat this step again with the second pencil and the other side of the front of the base. See the pictures for reference.

Once you have done this you will bring the two pencils together at the top and bind them together with another rubber band.

Step 4: The Frame - Part 2

The next part of the frame will provide support for the firing section.

You will need:
• Two additional pencils
• 3-4 rubber bands

This part was complicated for the kids but is not as hard as it may seem. All you need to do is take one of the pencils and tie the end close to the bottom of one of the pencils making up the front part of the frame. It needs to be down low to offer support but also not get in the way of where the firing pouch will be tied.

You will then take the other pencil and bind it to the other side. Make sure you bind it to the outside and not the inside or you limit your firing space.

When both support pencils are bound to the front of the frame take one to two more rubber bands and bind them in the back to the back cross-section of the triangular base.

Step 5: The Pouch

There are a lot of different ways to make the pouch. When I was coming up with the design it I made it out of duct tape because that was what I had on hand. But I suppose you could make it out of other stuff you have on hand. None of the other materials I tried worked as well.

You will need:
• Duct tape
• Scissors
• 3 rubber bands

What you need to do is cut or tear a strip of duct tape. The bigger you want the pouch, the bigger your strip should be. I should probably be around six inches max. Maybe closer to four. I've never really measured it to be honest. You'll take the piece of tape and sort of wrap it in on itself. Once you have a sort of cup you'll fill the interior with other strips of duct tape so the inside is no longer sticky.

Once the pouch is made you will need to cut three holes in the pouch near the edges. There should be as equal a distance between the three holes as possible.

You will then take your rubber hands and loop them through the holes. Pull them tight.

After you have gotten all three rubber bands secured through their respective holes you will take a few strips of additional duct tape and wrap them around the knots. This will keep them in place and also keep the rubber bands from ripping through the loop holes with excessive use.

Once your pouch is ready you can tie it to the frame as show in the final picture.

Step 6: The Ammo

Your catapult can effectively launch anything small enough to fit into the pouch. The original design shot rubber eraser ends but they tended to get lost too easily behind the computer desks in my lab. So when I made them with the kids we used some old ping pong balls.

The kids, of course, wanted to use thumb tacks and rocks so if you are doing this with kids you need to set ground rules early.

Step 7: The Finished Product!

Obviously, the design is fairly simple. There are a lot of ways to change it up and innovate. Once the kids got the hang of the basic design they went crazy and came up with all kinds of other little ways to tweak their catapults.

I included a couple pictures of the catapults we made as a group. The kids were great and they made some awesome catapults. I will try and update this later with some pictures the younger kids made if I can get one from the tech lab program lead over at their center.

We hope you enjoyed making these as much as we did. If you have any questions, suggestions, pictures of your own to pass on just let me know!