I have a piece of Angle Iron that has to be bend to a Ring.

I need to know the flat dimension so it can be cut to size before rolling it to the right diameter.

I drew a circle and then used structural members to make it Angle Iron. (see attached picture).

How do I convert this to sheet metal so I can flatten it.

Thank you.

p.s. I understand I can draw the side profile of the angle Iron and then convert it to sheet metal but I would really like to use the structural member option for this.