Are siege engines your thing? Do you love flinging things at high velocities? Well, then, this is the build for you! In this Instructable, you can learn how to build a Golf Ball Catapult with interchangeable arms that can shoot golf balls up to 80 feet! Just be careful, though! This build requires intermediate shop skills and a whole lotta' common sense. All right, let's get building now!

Step 1: Materials & Tools

To build your own golf ball catapult, you'll need quite a few materials that are very cheap and basic hand tools, and chances are you'll have some of them lying around the house.

Materials:

(10') 3/4'' PVC Pipe
(1) 3/4'' PVC End Cap
(1) Bottle Cap
(1) 5/16''x3'' Coarse Partially Threaded Bolt w/nut
(2'x2') 3/4'' Plywood
(1) Golf Ball
(1) 5-pound Brick
(5 1/2'') 5/16'' Wooden Dowel
(2) 5/16'' Metal Fender Washers
(16) 1/2'' Small Wood Screws
(4) 2 1/2'' Corner Braces

Tools:

(1) Jigsaw w/ coarse blade
(1) Drill w/ 5/16'' bit
(1) Screwdriver
(1) Bottle Wood glue
(1) Bottle Super glue
(1) Coping Saw

Step 2: Arms

I wanted to have arms of different lengths because I made this for a science fair project. For the lengths, cut the 3/4'' PVC pipe to lengths of 24'', 28'', 32'', and 36''. Then, drill a 5/16'' hole all the way through each of the arms exactly 6'' from an end of the arm. This is where the fulcrum will be. Then, on the PVC end cap, use a quarter-sized blob of Super glue to secure the bottle cap to it. Slide the PVC end cap onto the arm of your choice.

Step 3: Arm Supports

Cut the arm supports as shown. The only parts you need to cut are the arm supports. Cut off a bit of triangular excess, and the remnant is the base of the trebuchet - exactly 1'x2'. Drill a hole for the arm bolt as shown, with a 5/16'' bit. Once you've done that, you can test fit the arm and washers by layering them as shown. Once you put the other arm support on the other side, it should look like the final picture.

Step 4: Attachment & Base

Attach the arm supports as shown with corner braces and screws. Make sure that the arm can still swing freely with no resistance. Then drill a 1/2'' deep hole 2'' from the back and 6'' from each side below the arm and glue in the dowel. Let it dry for 4 hours.

Step 5: Counterweight

This catapult is going to be fired with a counterweight, so grab the 5 pound brick. Lift it up to 3', center it over the arm, and...

Step 6: Siege

To start world domination with your catapult, always go through this checklist before firing:

Arm laid back
Golf Ball loaded
Counterweight at proper height
Launch area free of animals and/or people

Once you've finished the boring part, just drop the brick and enjoy the smooth, long trajectory of the ball and arm. Thanks for your time reading this Instructable! I hope you enjoyed it. It was my biggest build I have ever done, and I have to admit, it was pretty awesome! Just a final note - if you do build this, be careful! During an early test when I didn't understand the power of this baby, I woke up 7 minutes later after having a dream that mikesaurus hit me on the head with a baseball bat. If you do build this, leave a comment and some pictures, too! I'd love to see how you did this. Just one last thought - this is great for defending your home from burglars! I currently have this positioned at my bedroom door, just in case. Well, thanks for your time!