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updraft to downdraft - double venturi - mft style

updated wed 9 feb 05


Ben on mon 7 feb 05

Hi Folks,
Well much labor later, I've got the big kiln cut in half. Used big =
ratchet straps around the middle to keep the arch up when I cut the =
brace. Lots of temporary metal bracing. All went well. New framing's =
all in in both halves, mostly 3'" angle. Ugly welding (Sorry Mel - =
borrowed wire feed - I'm used to stick) but strong enough I expect. On =
one half I have the back wall back in. I used 50/50 fireclay and grog =
for mortar. Stuffs taking forever to dry, but I think that's good. =
The other half will have to wait til I can afford some more brick. I =
finished the cart and new burner ports today. Used the wedge idea from =
the MFT for the cart. Nice tight seal. I was pretty encouraged. Just =
have to change some of the plumbing and build the chimney. So, for =
those familiar with the MFT design, the question is.... given the =

Chamber size - 5' x 4'6" x 4'9" (w x d x h) roughly 80 cu ft.
Burners - 10 x 75k btu ceramic tip venturi burners. 750k total
Inlet flues - 10 x 2 1/2" round
Rear wall - 4 1/2" + (1" fiberboard at a later date). all other walls 4 =
1/2" + 1" fiber + transite..

Can I adjust the outlet flue to account for the fact the I don't have a =
soldier course but rather two rows (5" rather than 4 1/2")?

Right now I have the outlet port at 5" x 6 1/2" Slightly larger in area =
(32 1/2 sq. in.) than the 4 1/2" x 7"(31 1/2 sq. in.) Now is the time =
to change it if I'm going to.

My intention is to bring the first chimney course 7" wide by 5" high in =
front, with the rear bricks 9" wide by 5" high. Slightly different than =
spec'd in the book.

Does this seem good? Anyone done anything similar?

Is there any harm in running a few more courses of brick between the =
damper and the second venturi constriction?

I'm planning on using hardbrick for the chimney then 10 culvert. bueno =
/no bueno?

Any input greatly appreciated. It's amazing how much a little feedback =
can help crystallize your thinking. I appreciate those on this list who =
take the time to respond.

Take care,