Donnie,
Is this for the TGA F-15 you have mentioned in previous posts? For a Byron fan the best way to go, by far, is with mylar. It is strong, light, fuel proof, and cuts easy with a scissors. You can get it at a drafting or a plastics supply store. If you don't have an old tube to use as a pattern just wrap one end around the fan, size the other end to the exit nozzle, trim it with a scissors, leave a half inch overlap seam, and glue it together with CA. Make sure the seam is at the top. I also wrapped mine on the outside a couple of places with fiberglass reinforced packaging tape.

Very easy and will last forever.

Joe