How can you make a homemade spring tension rod that will handle 5 pounds of fabric over a span of 77 inches?

I am working at making a temporary window coverings for stained glass windows. I need to make decorative 'black out' type curtains and have chosen a heavy tapestry fabric to go with the period building. The windows need to be blacked out so that a projector screen is dark enough to be seen clearly and the flicker of light doesn't cause a visual strobbing distraction. When the weekly event is done, I need to quickly remove the curtains after the event and roll them up for storage the next week. Tension rods seemed to fit the need, but I can't seem to find them in the right length with enough strength to prevent sagging in the center, or outright falling down. I am not allowed to drill into the wood casement windows or in anyway mark them or the walls. Tension rods again seem the answer. I can only find Shower rods up to 72". Suggestions PLEASE!

sarajo7 years ago
What about trying the command adhesive hooks? Since you can't drill, they will stick to the wall and then you slip the rod into the hooks!