In rec.crafts.metalworking, Bob Engelhardt wrote:
On 4/3/2021 10:38 PM, Linda Iverson wrote:
What if I just want to use black steel pipe as a curtain rod to hang heavy
velvet drapes spanning a window greater than 12 feet long without the need
for a center support?
If you specify the weight & the maximum sag acceptable, someone here
can tell you the pipe size to use. However, heavy drapes and a 12'
span mean that the sag will probably be unacceptable for anything but
a really big pipe.

Or hide the sag with a valance box.

Elijah
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as old fashioned as heavy velvet drapes