I've been on the fence for awhile about whether to try this project or not, but decided to go for it. I want to say thank you to those that posted their own builds on this forum and freely shared their knowledge and time. Without you I wouldn't have even started this project.
After spending many hours on this forum, watching youtube videos, and searching online for parts to do a build, a kind of a funny thing happened that caused me to go for it. I needed a flat sheet of plastic for another project, and had some lengths of used 12" pvc pipe laying around and I got to wondering if I could cut up a section, heat it up and flatten it out. I gave it a try, and it worked out much better than I expected. After successfully flattening out several sheets, I realized I had the material to build a drum for an RDF.
I taped a piece of aluminum flashing around the pipe to use to mark a line to make a square cut.
I also marked both sides with a horizontal line so I could cut it in half lengthwise.
Made my cuts with a Skilsaw.
Loaded 1 at a time into my propane bbq. closed the lid and fired it up. I kept peeking every few minutes, and when the plastic started to slump, I removed it with a stick stuck through it, layed it out and flattened it on my steel table, put a sheet of 12G sheet metal over it with cinder blocks for weight, and let it cool.
Simple as that. I had my flat sheets of PVC. The thickness is just a hair over 5/16". Third of an inch. My BBQ limits the lengths to 22-5/8", and half the diameter of the pipe gave me a little over 18" wide. I didn't melt any of the pieces, but I did scorch the surface slightly a couple times. Worked out great.