Even Boil

[1badsapper]

My pan is 24x48. I'm building a masonry arch with a fire brick liner. I plan on putting a sloped bottom in it like the factory models. The fire box will be 24" wide by 16" deep & 16" high. The sloped portion will start from that point. The total height of the arch is 32" Is the sloped bottom really necessary in an arch of this size ?

[Jec]

Yeah you will save wood and heat by directing the heat toward the bottom of the pan. That is what the slope does. But, what is better if you can slope then go parallel to the bottom of the pan. You will save even more heat like that.
Joey

[Rossell's Sugar Camp]

Fill your block with vermiculite. It will help your insulation. And the slope is necessary in any evaporator. It confines the heat to a certain area, the pans.