length of doorway and flu diameter?

[sonomacast]

Today I cut all the forms for a cast modular oven. I have decided to make it 1050mm (41") in diameter. 472mm dome height (18.5") with a door opening of 297mm (11.6") High. The doorway is a complete arch 558mm (22") wide. The vent landing is 610mm wide (24")
Basically the dome height is 90% of the radius of the oven floor and the door height is 63% of the dome height. All walls are 75mm thick (3").

Now my query is this. What diameter should my flu be for a 1050 (41") Oven and what would be the best length of the landing?

Thank you

[sonomacast]

Re: length of doorway and flu diameter?

Is it correct that the correct flue size is 10% of the door size squared.
eg, my door is 22" x 11.6" = 225.2"square. so my flue should be 22.5" square= a flue of 5".......................Is this correct?