Here is the balance of the Chimney text:
Assembly:
I used the can cover to make a circle on scrap cardboard, drew in three one inch square tabs and cut line 5.25 inches from the bottom of the far tab. After three baffle pieces were cutout of the sheet metal using the pattern, the tabs were then all bent up at a 90 angle, completing the baffles. I then divided the height of the can into four equal sections, which yielded a measurement of 2 7/8 inches. Marks were made on the outside of the can at these intervals. A 2 inch diameter hole, centered in the bottom of the can, which now will become the top of the chimney, was cutout using a hole saw. The upper most baffle was then trimmed to friction fit into the can 8 5/8 inches from the open end (former top) and parallel to it. A hole was then drilled simultaneously into the can and tab on the baffle (eyeballing the tab location from the outside marks) while holding the tab in place with a small wood block to prevent the tab from bending while being drilled and to avoid drilling my fingers. A small and short sheet metal screw was then installed, securing the baffle tab to the can. This was repeated with the other tabs. The next baffle was then installed at 5 ¾ inches with the flat side 180 degrees to the first, using the same method. The final baffle was installed 2 7/8 inches from the bottom, again rotating the flat side 180 degrees relative to the second baffle. I now had a completed baffled chimney in less than an hour.
Performance:
Testing proved the effectiveness of the design. In winds that were between 8 to 10 mph, with much higher gusts, at an ambient temperature of 48 degrees, it took the smoker 33 minutes to achieve an internal temperature of 281 degrees. It took a total of 47 minutes to achieve 300 degrees. Not bad considering the wind velocity and temperature. Another test was conducted at an ambient temperature of 32 degrees. Winds were light and variable in the 3 to 5 mph range. It took the smoker 41 minutes to achieve 281 degrees. In either test, the stock heating element had no difficulty maintaining the set temperature once reached. Note that the biscuit heater was turned on in conjunction with the main element as a standard pre-heat procedure.
Design Overview:
The fundamental objective was to design an insulating wind resistant chimney based on a fully open smoker vent. (While not test proven, the temperature/wind resistance should theoretically increase with a partially closed vent.) Since the area of the fully open vent is approximately 3 square inches, that value was used to determine the size of the 2 inch diameter exit hole. (3.15 square inches). Since noise reduction was not required, the standard open area allowed by the flat end of each baffle is approximately two times the vent area. Given the air volume and movement restricted by the baffles, the insulation value of the chimney is approximately the same as a standard 2 x 4 wall (between R 8 - R13).
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