I just built a "mother of the fermentation chiller" based on this design:
I deviated from the design somewhat ... Instead of the recommended 2" thick sheets, I used two 3/4" sheets glued together with a 1/4" air gap between them. And of course my cut tolerances aren't great. I plugged major leaks with caulk + liquid nails, but some small leaks remain.
The end result performed horribly! I could see an immediate drop in temp (~3 degrees) when I turn on the fan (PC chassis fan) but the chamber temp never got below 70 F. (Room temp is only 75 F). And the ice in the bottom section melted almost completely within an hour or two.
Maybe I'm not using enough ice, or blocks were too small?
Seals too leaky?
Fan too small?
Or too much heat generated from the initial fermentation couldn't be overcome?
Has anyone had success with this design?
On a different note ... my beer languished at 74 to 76 F for about 24 hours with vigorous fermentation before I moved it to the old fashion bucket + water + towel + fan method... Should I expect off flavors with this short high temp + very active fermentation?