How do you use a regular pipe bender to build a hoop house arch?

Hi, I know I can get the pre-made pipe bender online, but I wanted to know how I could do it with a regular pipe bender from Home Depot, Lowe's, or some place like that.  I've seen how so use a pipe bender (not done it), but I don't know what angles I would use or how difficult it would be.  I was looking at 12-16' wide.  That made me think the radius is 8', in a perfect circle, though I am wondering if it is more of an ellipse.  8' is high enough for me.

angle = 90 for one of the four quadrants of the sphere, one pole really.
radius is 8' (16' dia.)
Arc Length is 12.56637' (from an online calculator)

s=r(theta) or something.

But, how do I know how to bend the pipe at a certain angle to get those dimensions with a regular pipe bender?  Do I do 30 degrees, 27, 5.49939393, who knows?  I didn't want to buy the pipe bender just for a greenhouse, if I didn't have to.  No offense to you who sell them.  I wanted to learn to use a regular pipe bender.

I purchased commercial hoop benders that are made from galvanized fence top posts and bends the same top post.
Here is a fella making hoops from 1 inch conduit but I see no reason that you couldn't upscale the fixture for larger pipe.
https://www.bing.com/videos/search?q=greenhouse+hoop+bender&ru=%2fvideos%2fsearch%3fq%3dgreenhouse%2bhoop%2bbender%26FORM%3dHDRSC3&view=detail&mid=DA7345E57B38DF38A92EDA7345E57B38DF38A92E&rvsmid=F7818C70F426EF6DBC9EF7818C70F426EF6DBC9E&FORM=VDRVRV
I use conduit and a conduit bender over raised beds for netting and season extenders throughout the property

I used to use an electricians pipe bender day in and day out.
It is complicated enough that I cannot easily describe it.
You can learn to bend arches  with them, but that is some next level stuff that I never mastered.
Bending the pipe in three places could give you 1/2 of an octagon, thus emulating a half circle.
The best way to learn is to do, so I would advise getting a small 1/2" bender and sacrificial pipe.
For references, Uglys makes book on conduit bending that will be way too in depth, plus it covers electrical stuff you don't need to know.

This video  is a place to start:https://youtu.be/gaaz_Tu23eQ


If you want to see a home made version of an hoop bender, check this out:https://youtu.be/UR4GuQJgVrk