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Once you know approximately how many beach balls and inner tubes you need, you can purchase your materials and get to work. You may want to purchase a couple of extra balls/tubes, because it may take some trial and error to get your arch just right. For this project, you’re going to need:  2 larger inner tubes An even number of smaller inner tubes An odd number of beach balls Latex glue (available at craft stores or online) An air pump to blow up balls and inner tubes Use an electric pump or hand pump to inflate all of your beach balls and inner tubes. Fill each item until it is firm to the touch. Full, firm inflatables will make a sturdy arch, but be careful not to overfill them. Otherwise, they might pop. Practice constructing the arch without glue, to make sure you like the design. You may need to enlist the assistance of a friend to hold the beach ball arch in place. Remember, the order goes: a large inner tube at the base (on each side), followed by pairs of beach balls and small inter tubes. For the construction of the arch, you will definitely need help from 1-2 friends. It is important to glue the pieces together with the arch standing up (as opposed to lying on the ground), in order for you to get the curvature just right.  Apply a thin layer of latex glue to the bottom base inner tube, and press 1 of your beach balls against it. Apply pressure for 20-30 seconds. Apply a thin layer of latex glue to the beach ball, and press 1 of your small inner tubes against it. Again, apply pressure for 20-30 seconds. Alternate between sides: do a few layers on the left, then a few layers on the right. Be sure to gentle curve the balls and inner tubes in the shape of an arch. Have your friends hold the arch in place as you connect the 2 sides. The top/center of the arch will need the most support. Be sure to glue the balls/tubes with the inflation tabs sticking out. This will allow you to add air as needed, and help with take down. Take turns holding the top/center of the arch for a minimum of 10-15 minutes (although longer is better), until the adhesive starts to set. Finally, leave the arch alone for several hours, to allow the adhesive to cure. If you have constructed your arch near a solid structure (like an existing doorway), you can use rope or twine to help secure the arch. Loop a length or rope or twine around the arch in the top middle, and find a place to attach it. Add another length of rope/twine on each side of the arch. This step is optional, but advisable, especially if your arch will be outdoors. Open the nozzles on all of the inflatables. Untie any rope or twine you used to secure it. Give the arch some time (an hour or 2) to deflate naturally. Squeeze the remaining air out, fold up the arch, and store it for future use. Next time you use the arch, you may need to use latex glue to re-secure any connection that may have come loose.
Purchase your materials. Blow up all inflatables. Practice stacking the inner tubes and beach balls without glue. Add adhesive to the beach balls to create your arch. Hold the arch in place for as long as you can. Add additional support. Take down your arch.