I've been doing some tests with the galvanized sheetmetal ducts
available
at
HomeDepot. They are not designed for wood stoves. If you put one
directly
above a cast iron stove it will get a deep red color if the flues are
open
and it is well stoked. The cheap ones are sold flat and you pop the
joint
together. A couple of 7" hose clamps would prevent it from popping open
from the heat change. When they cool back down the metal is discolored
white, no longer shiny. A significant amount of heat is left in the
room
from the chimney so I'm using thin, cheap material and trying to keep
the
combustion down in the stove.

The old time "stove pipes" were sheet metal with a interlocking joint
lengthwise. One end had a sort of corrugated pattern rolled into it to
make it small enough to slide into the next section. and they would
get red hot too, if you didn't know what you were doing.

The idea is to build a fire in the stove to warm things up, not large
enough to have flames shooting up the chimney.


Just doing tests. Got it nice and hot, then ran up to full heat with
hardwood slats. Flames were going up a couple of feet in the pipe.
Normal
use is with both dampers closed so I don't spend so much time with the
sawbuck. I ventilated the area when curing the stove and pipe. I've
heard
of zinc fume fever before. Used to cook over charcoal in galvanized
washtubs.

Those 6"dia. galvanized vent pipes are $8.20 for a 5' length and a couple
of
SS clamps are $1.98 ea.


Where can I find them? I could use about 12' and 2 right angles



That's standard Home Depot furnace duct. It sits flat on a shelf looking
like 2' X 5' galvanized sheet with the interlocking joint down one length.