Arch Design

[woodsplumber]

I have a 3 X 12 raised flue(8' sap pan), with a 10 gph oil burner and a homemade arch. How can I get plans for the ideal arch configuration and insulation?

[Cider Hill Maple Farm]

I'm in the same boat woodsplumber, still doing research. I can design it after I know the best internal location and pitch for the ramp. Hopefully we get a few more replies!