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double venturi flue box for wood fire ???

updated tue 8 jan 08


Mary & Wes Handrow on mon 7 jan 08

I built one using the dimensions that Nils talked about in his book for the
kiln in Alaska. For me it just didn't breathe. Opened up entrance to the
base of the chimney keeping the restriction at the base and losing the
venturi further up the stack and now it draws with a roar and I must use the
damper to keep my pots from going up the stack. You can just use the damper
further in for gas, which if you think about it kind of forms another
venturi since a venturi is nothing more than a restriction that creates a
low pressure area that increases the speed of flow at that point.

-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Robert
Sent: Sunday, January 06, 2008 8:23 PM
Subject: Double Venturi Flue Box for Woodfire ???

Hi Clayfolk,
I am building a 30 cu ft kiln from homemade castable. I have used/built
the double venturi flue box very successfully with propane kilns. My
last one was 85 cu ft and fired very efficiently with an outlet port of
only 32.5 sq in of cross sectional area. I am building this one as a
multi fuel kiln and the wood firing component will be a double bourrey
system parallel to the axis of the arch. I would like to use the double
venturi flue box ala nils lou/mft but expect to need a larger outlet
flue for wood than lp. I would like to cast the outlet flue to the
size need for wood firing and cast a separate insert for the gas
So the question is... Has anyone on the list used the double venturi
flue box on a wood kiln? with a bourrey box? If so any
observations related to flue sizing would be greatly appreciated.

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