I have a hoop type thing, that holds a curtain (4 sides). I want the curtain to fall.

What are a few options for making this happen?

High tech (but reliable) , low tech.... both would be appreciated.

thanks

Low tech... Ripcord: Long tape with several pins or tabs, equally spaced along the length (or possibly just at the corners). They lock small loops into place, through grommets in the curtain, holding curtain to frame. One pull of about 3" pulls all pins simultaneously, releasing curtain. Same idea has been used for break-away costumes.

I'll second that.

The cord should not have any "give". You'll need lots of testing to get it right. Drill holes in the hoop, thread the cord to a central point and join them (outside) with your handle.

Metal which is extruded may a sharp ridge inside but you could always pour a thin coat of fiberglass through the interior to smooth it out or just use PVC for the tubing.