need help with radius of arc

[davismetal]

I am building a sign and getting ready to order pre bent 3x2 tube steel.

they need to know the IR that i want.

I need 3 20 foot pieces that i will be putting 18 inch letters between in 2 rows.

i dont want a rainbow shape more of a minor arc. do i need a 18" ir?

[txcncman]

20' bent on an 18" radius will look like a cork screw when they are done. You need to think about cord length and then calculate the radius from that. And, all 3 pieces will need a different radius if you want to maintain the 18" spacing for the entire length. You said 2" X 3". I assume they are going to roll this for you on the 2" dimension. For an arc of 20 degrees for your length of 20' you will have inside radii of 687.5", 707.5" and 727.5". This allows for the 2" material with 18" in between. This gives you a rise in the center, when both ends are level, of about 10.5". See attachment.