The PitCalc is really for reverse flow cookers. You don't need much for an insulated vertical. Make the firebox big enough to hold enough charcoal or wood. The chimney doesn't have to be any certain length but make sure you can close it off. The throat (opening between firebox and cook chamber) should be about 6" (15cm) square but you should have some way to adjust it for tweaking.
More info would help. I saw the fridge but don't know how you're intending to use it. Heat source, size, etc.
If it's tourist season, how come I can't shoot 'em?
I'm probably going to use gas for my fridge as the frame of the fridge is wood & this way I can control where the flames are, but I've already had a few people ask about UDS or water heater smoker builds for them, which is why I originally checked out the pitcalc in the first place to see if I got mine right.
The fridge section is 800 x 450 x 350 & the area underneath is 300 x 500 x 450(after I finish the mods) with a tapered top area to funnel the smoke up. The throat is about 150 x 200 & the chimney will be 50mm diameter & about 600-700 long with a cone shaped hat on the top. I'll look at putting a butterfly in the chimney.
Last edited by Squiggle on January 10th, 2016, 5:06 pm, edited 1 time in total.
You could probably make it into an insulated electric smoker as well. Just set a hotplate (single electric burner) on the bottom with some wood chunks in a small cast iron pan. Might be safer in what you've got than a gasser.
If it's tourist season, how come I can't shoot 'em?