This is our design for our launcher! We chose a ballista as we figured it would be the most efficient in short and long distances. The materials are listed below. All pictures will be in order according to what you are told to do. Dotted lines represent wood screws. Black lines represent rope.
You will first need to cut two of the 2 ft stud as seen in the picture above (the smaller side/side measuring 1.5 inches will face the front while the other side will face the sides). You will now attach them using wood screws (dotted line = screw) to one of the ends of the 6 ft stud (the 6 ft stud will have it's larger side/side measuring 3.5 inches facing up) but you need to leave 3.5 inches of space in-front of where ever you attach the 2 ft stud. That space will be for later when we start building the large part holding the rope. Once you are done it should look like the right side of the image.
Step 2: Torsion Mechanism
Attach 3 ft stud at the bottom of the 6 ft stud in front of the 2 ft studs you added last step using wood screws. Add the 1 ft studs at the sides of the 6 ft stud on top of the 3 ft stud and at the ends of the 3 ft stud. Once you have done so attach the second 3 ft stud on top of the 1 ft studs you just attached. Once you are done it should look like the 3 image.
Step 3: Torsion Mechanism Cont
You will want to make 2 holes for each 3 ft stud. You will want to put the holes 6 inches either end and 1 3/4 inches from the front. You will need to remove 3 ft of rope from the 50 ft this should leave you with 47 ft. The 3 ft of rope will be used in a later. Cut the 47 ft into two 23.5 ft pieces. Grab one of the 1 ft PVC pipes and tie one of the 23.5 ft ropes to it. Put the rope through the holes once you have done so put a second 1 ft PVC pipe on the other end and wrap it with rope by bringing it back and putting through each hole until the rope has gone through 3 times. Once done place the 3 ft PVC pipe in front of the 3 strings then pull the rope over the 3 ft pipe and through the hole where you will wrap the string around the 1 ft pipe by starting on the side where the 3 strings are you will then bring it through the hole once more and bring the rope to the side where the 3 strings wrap on the 3 ft pipe and finally through the second hole and wrap around the bottom of the 1 ft pipe (Almost like a figure 8). Continue to wrap the rope the same way (but now the rope will go on the opposite side you did the first time). Once the rope is short tie the remaining rope to the side of the pipe.You should have wrapped the 3 ft PVC pipe with rope (it should look something like the second image). Now repeat on the other side.
Step 4: Projectile Pouch
You will need to use electrical tape to make this pouch. It will practically be a tape cup holder. Make sure the pouch is longer than the cup itself as the cup will only use up half of that space while the rest will be used to attach it to the rope. Once you have finished the pouch insert the cup and tape it to the edge of the cup. Finally make 2 holes on each side at the back where you left some empty space in the pouch (try to leave as much space between each hole).
Step 5: Finish
You must now tie the 3 ft rope to one of the 3 ft PVC pipes. Attach the triangle made from the left over 2 ft stud with wood screws to the end of the 6 ft stud as seen above. Before tying the rope you must put the pouch you made last step. Put the rope through the holes you made. Once done it should look like the image above. Pull the rope around the triangle piece if it slips off you might want to make a small dent on the triangle large enough to hold on to the rope. Tie the rope to the other 3 ft PVC pipe. Make a a rope of tape (represented by the black line in the final image) and tie it to the rope this will allow us to pull on that tape and pull the rope over the triangle setting the whole thing off.