Fisher catalyst mod

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albert_k

New Member
Dec 15, 2025
1
minneapolis
Hi gang!
i’ve got a Baby Bear in a Northern Minnesota cabin that’s about 320 ft.² and not terribly well insulated. As you expect, I struggle from burn times at night in this little stove. While installing the baffle upgrade last week, I came up with an idea for a removable catalyst, and I thought I would throw it by you. currently the baffle plate goes from below the rear exit, Slanted upward toward the rear upper joggle in the middle top plate. This allows the necessary 2+ inches of air gap for me. However, as I was thinking about it, I could cut a round hole in that plate toward the front of it and install a round catalyst. I can then install a second smaller plate (about 13” wide by 3” deep in front of it that acts as a bypass when tilted up, and closes of the 2” exhaust gap when down, forcing the exhaust through the catalyst when operated. The only exterior modification I would think I would have to do would be to drill a hole in the side of the stove, right where the low deck joggles to the high deck. install a small but heavy duty steel tube with a joggle bend on the inside to raise and lower the bypass plate when rotated. this tube would protrude a couple of inches out of the stove and have a handle.. the end of the tube sticking outside of the stove would be threaded and have a slot cut in it. A threaded knob would then be installed in the end of the tube. Similar to the front air inlet, as you unscrew the knob, more air gets into the catalyst. thoughts?