Can we learn from a Center Pivot?

Wonderful thing .. a center pivot .. by looking at the number of sections and wheels you can tell the number of acres being farmed .. and the sprays next to the center are very small while the sprays out on the end are moving much faster and very large.

So, why have the same six inch vent tube running the entire thirty to forty foot length of your cob mass?

If the center of a six inch vent is carrying a river of heat in the center and we are getting too much heat in the first ten feet and not enough in the last ten feet .. start off with a round eight .. then a round six .. then a flat six and then a flat eight? Round is a conduit and flat is a scrubber!

"Love the one your with." Use a round six all the way and use insulated cob in the first ten feet, less insulated cob in the next ten feet .. jump back to heavy insulated cob in the corners where you can't sit .. and engineer your insulation as you work out or double up.

Tapering the duct is how they teach in a sheet metal apprenticeship, a proper one. Good point, Dusty.

Also, just because a duct is purchased as a circle, might not necessarily mean it must remain a circle as-installed. Bending it into an ellipse would improve heat transfer to the cob, and allow for a more-constant flow due to thermal contraction of the gas.