Insulating a cylindrical forge

[al Raven]

I'm building my first forge its going to be cylindrical in shape 2 venturi burner. My questions are what's the best burner angle or position and what's the best insulation to use? I want to get it right the first time.

 

[Stacy E. Apelt - Bladesmith]

It is well covered in the stickys and many previous threads. The burners should be angled at about 20°. Most of use used to aim them from the back forward, but now we usually start at the front and aim them back at 20°. Placement of two burners should be at 25% and 65% back from the front. A rear port of about 2X3" is good. Front port of 3X4" is about right.