This picture illustrates the wooden dowel that was inserted at the joint between the sections of our PVC mast pipe. It was required to provide a rigid joint and ease of connection. Without it, the joint folded with almost no pressure.
Note the yellow labels to designate joint number and the white marks to designate pipe position. Holes were drilled in the PVC pipe and dowel. Wood screws provided secure connection.
This picture shows a completed joint.