On a raised flue the bricking IS different from drop flue. Congratulations, I think you have chosen the more efficient design. To brick a raised flue you should consider using sheets of ceramic insulation first, glue it to the entire inside of the sheet metal (insulation will improve fire intensity and save wood every time you use it). Once this is done, do the fire box first by bricking against the insulation if you did that step or against the tin if you went with no insulation, laying the brick in any pattern that fits best and use a little refractory cement to hold in place as well as between the edges of the brick. At the rear of the firebox, biuld a wall up about 1/2 way to 2/3 in height. From there brick upward as you go back at about 40-50 degrees until you get up about 1/2" below the siderails where the pand will rest. If you have filling to do to get this angle use vermiculite, a pourable dry non combustable insulation ( available from nursery supply houses, be sure to get straight vermiculite without foam beads) Calculate the volumn and buy big bags, if you get it from someplace like Lowe's or such you will pay several times the price it is from nursery supply houses.) Pour the vermiculite in place and cover with firebrick or else the stack will suck it out in short order. From the rear of the ramp described above, fill the vermiculite to within a 1/2" after allowing for a layer of firebrick on top. This goes back until you get towards the rear where you must build a wall down to the bottom of the tin to allow for the exhaust to sweep down and curve up into the stack. This area should be just over the depth of the stack. For example, if you have an 8"x18" stack, make the chamber about 8-10" front to rear and full width. The idea is to force the heat up into the flues to get peak boil. Descussions were out when I bricked mine to run the rear firebox wall higher and the slope steeper. I found this to be too much and the boil was so intense at the ramp that I could not keep the sap in the flue pan, it jumped violently and every way I shielded it to channel the splashing, I still lost sap. I now lowered my rear wall as i suggested and went to the 40-50 degree angle and I can boil fast without loosing prescious sugar.
Good luck, If you have any further questions do not hesitate to ask.
Dave Klish, I recently ordered a 2x6 wood fired evaporator from A&A Sheet Metal which I will be converting to oil fired
Now have solar, 2x6 finish pan, 5 bank 7x7 filter press, large water jacketed bottler, and tankless water heater.
Recently bought another Gingerich RO, this one was a 125, but a second membrane was added thus is a 250, like I had.
After running a 2x3, a 2x6, 3x8 tapping from 79 taps up to 1320 all woodfired, now I'm going to a 2x6 oil fired and a 200-425 taps.
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