Then, you'll simply connect the pipes using 4-way connectors, like these Zernmiarder 4-Way PVC Pipe Fittings, ... adding wood dowels across the arched portion, ...

Acquire an empty 5-gallon drywall bucket, 1- and 4-inch-diameter PVC pipe, a 4-inch flat PVC end cap, pipe fittings to reduce the 4-inch diameter down to 1 inch, a 1-inch tee fitting, PVC solvent ...