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The pipe should be firm but wobbly when shaken. 1” to 1.5” diameter pipe works well. Using a saw, cut the pipe down to the length of the combined handle and sword blade. Think about whether or not you want the sword to be usable with two hands, or one-handed only. Cut a piece of closed-cell foam rubber (which comes in a cylindrical shape, with a hole for pipe in the center) down to the length of your sword plus a few inches. Slide the tube onto your PVC pipe. If you want to, add a crosspiece by sliding a four-way pipe fitting onto the hilt end of your main PVC piece. Cut two short pieces of PVC pipe, both the same length. Slide one piece into each open side of the fitting to create a crosspiece. Once you're happy with the width and positioning, use plastic cement to secure each piece in place. If you want, to make the sword safer to use, add small pieces of closed-cell foam to each end of the crosspiece and the base of the hilt. This has the added benefit of creating a “pommel” of sorts. Start by wrapping your grip in duct tape. Cut it when you reach the base of the crosspiece and smooth it flat. Next, wrap duct tape thickly around the base of each piece of foam rubber, helping secure it to the pipe. Add straps of duct tape pulled tightly around the foam to further secure it. Finally, wrap the entire foam blade in duct tape from bottom to top. The last few inches of the foam should extend past the PVC tip for safety; feel free to wrap this “soft tip” as well, closing off the hole in the top. Completely wrap any other pieces of foam you added with duct tape as well. The duct tape gives them a shiny metallic look, and protects the form from the elements. Once your weapon is finished, it can be used to stage fun sword fights with your boffer-wielding friends. The weapons are soft enough to prevent any serious injury, so have at it!

Summary:
Start with a length of PVC pipe. Wrap with foam rubber. Add a crosspiece. Add more foam. Unleash the duct tape. Wrap up and have fun.