jonathan byler on mon 30 aug 10
I was just reading in jack troy's "salt glazed ceramics" that "placing
the damper high helps assure heat staying in bottom of kiln."
Can someone explain why this is? why would it matter whether the
damper is 2 ft. above the exit flue at the bottom or a downdraught
kiln as opposed to 7 ft. above the exit flue?
Also, I am interested in learning a little more about chimney sizing
for wood kilns I read in olsen's book that the firebox floor should
be a minimum of 10 times larger than the chimney cross section. How
do you determine what the chimney cross sectional area should be for a
given kiln size (in my case about 40-60 cu ft.)? and isn't that area
also important in relation to stack height? in my case I will need to
go up at least 16 feet to clear an adjacent roof line anyway.
jonathan byler on tue 31 aug 10
Hi gary,
when you get a chance, I would love to know a little more about why
you want the damper above head height. is it because you are bumping
in to it or because it would fire better?
On Aug 31, 2010, at 6:18 PM, gary navarre wrote:
> Hey Jonathan,
>
> I think we also need to include the size of the entrance flue and
> the area of fire depending on the type of firebox.
>
> I don't agree with Olson especially when using the Bourry because it
> is more efficient than an updraft fire. Most of my proportions are
> based on a combination of the rough guide in "A Potters' Book" such
> that the chimney cross section past the exit flue is about the same
> size as the exit flue, the throat arch (entrance flue) is larger
> than the exit flue, and the Bourry hob opening is now quite a bit
> bigger than the throat arch. The actual measurements are buried in
> my recent albums somewhere. I might post them later.
>
> In retrospect I wish I had put the active damper above my head on
> the stack instead of belt high but I intend to make more use of the
> chimney cap and 4 passive damper holes up the stack but I'll get
> into that later too. Stay in there eh.
>
> Gary Navarre
> Navarre Pottery
> Navarre Enterprises
> Norway, Michigan, USA
> http://www.youtube.com/GindaUP
> http://public.fotki.com/GindaUP/
>
>
> --- On Mon, 8/30/10, jonathan byler wrote:
>
>> From: jonathan byler
>> Subject: [Clayart] damper placement/chimneys
>> To: Clayart@LSV.CERAMICS.ORG
>> Date: Monday, August 30, 2010, 6:00 PM
>> I was just reading in jack troy's
>> "salt glazed ceramics" that "placing
>> the damper high helps assure heat staying in bottom of
>> kiln."
>>
>> Can someone explain why this is? why would it matter
>> whether the
>> damper is 2 ft. above the exit flue at the bottom or a
>> downdraught
>> kiln as opposed to 7 ft. above the exit flue?
>>
>> Also, I am interested in learning a little more about
>> chimney sizing
>> for wood kilns I read in olsen's book that the
>> firebox floor should
>> be a minimum of 10 times larger than the chimney cross
>> section. How
>> do you determine what the chimney cross sectional area
>> should be for a
>> given kiln size (in my case about 40-60 cu ft.)? and
>> isn't that area
>> also important in relation to stack height? in my
>> case I will need to
>> go up at least 16 feet to clear an adjacent roof line
>> anyway.
>>
>
>
>
gary navarre on tue 31 aug 10
Hey Jonathan,=3D0A=3D0A I think we also need to include the size of the ent=
ranc=3D
e flue and the area of fire depending on the type of firebox. =3D0A=3D0A I =
don'=3D
t agree with Olson especially when using the Bourry because it is more effi=
=3D
cient than an updraft fire. Most of my proportions are based on a combinati=
=3D
on of the rough guide in "A Potters' Book" such that the chimney cross sect=
=3D
ion past the exit flue is about the same size as the exit flue, the throat =
=3D
arch (entrance flue) is larger than the exit flue, and the Bourry hob openi=
=3D
ng is now quite a bit bigger than the throat arch. The actual measurements =
=3D
are buried in my recent albums somewhere. I might post them later.=3D0A=3D0=
A In=3D
retrospect I wish I had put the active damper above my head on the stack i=
=3D
nstead of belt high but I intend to make more use of the chimney cap and 4 =
=3D
passive damper holes up the stack but I'll get into that later too. Stay in=
=3D
there eh.=3D0A=3D0AGary Navarre=3D0ANavarre Pottery=3D0ANavarre Enterprise=
s=3D0ANorw=3D
ay, Michigan, USA=3D0Ahttp://www.youtube.com/GindaUP=3D0Ahttp://public.fotk=
i.co=3D
m/GindaUP/=3D0A=3D0A=3D0A--- On Mon, 8/30/10, jonathan byler L.COM>=3D
wrote:=3D0A=3D0A> From: jonathan byler =3D0A> Subject:=
[Clay=3D
art] damper placement/chimneys=3D0A> To: Clayart@LSV.CERAMICS.ORG=3D0A> Dat=
e: M=3D
onday, August 30, 2010, 6:00 PM=3D0A> I was just reading in jack troy's=3D0=
A> "=3D
salt glazed ceramics" that "placing=3D0A> the damper high helps assure heat=
s=3D
taying in bottom of=3D0A> kiln."=3D0A> =3D0A> Can someone explain why this =
is?=3DA0=3D
why would it matter=3D0A> whether the=3D0A> damper is 2 ft. above the exit=
flu=3D
e at the bottom or a=3D0A> downdraught=3D0A> kiln as opposed to 7 ft. above=
the=3D
exit flue?=3D0A> =3D0A> Also, I am interested in learning a little more ab=
out=3D
=3D0A> chimney sizing=3D0A> for wood kilns=3DA0 I read in olsen's book that=
the=3D
=3D0A> firebox floor should=3D0A> be a minimum of 10 times larger than the =
chim=3D
ney cross=3D0A> section.=3DA0 How=3D0A> do you determine what the chimney c=
ross s=3D
ectional area=3D0A> should be for a=3D0A> given kiln size (in my case about=
40-=3D
60 cu ft.)?=3DA0 and=3D0A> isn't that area=3D0A> also important in relation=
to st=3D
ack height?=3DA0 in my=3D0A> case I will need to=3D0A> go up at least 16 fe=
et to =3D
clear an adjacent roof line=3D0A> anyway.=3D0A> =3D0A=3D0A=3D0A
douglas fur on sat 4 sep 10
Jonathan
"Also, I am interested in learning a little more about chimney sizing
for wood kilns"
I agree- Gary's post refers to Leach which is what Olsen uses. Leach gives
his source as an English engineer and Matsubayashi all of which is based on
dense fire brick. What should we use for IFB or Fiber? Olsen gives heat
requirements for IFB @ 10,000btuh/ cubic foot and DFB @ 15,000 btuh/Cu.Ft.
of kiln capacity. So would a IFB kiln need a chimly area 2/3 the cross
section recommended by Leaches DFB guidelines or 2/3 the height or 2/3 of
both dimensions.
I fired a sweet firing 27 cuft IFB kiln built by Bruce. Finch. It's chimney
section was 7.5"X7.5". The height was just to the top of the arch. In a
similar DFB kiln I'd expect to see a 9"X9" chimney at least 12 feet tall.
Which comes to a crossection size 69% of DFB and a height at about 50-60%.
DRB
Seola Creek
gary navarre on sun 5 sep 10
Hey All,=3D0A=3D0A I wasn't aware of the distinction between IFB and dense =
bric=3D
k in the rough guide by Leach but since my preference became hard brick it =
=3D
is useful to me to see that, according to Olson, I will need at least 15,00=
=3D
0 btu's/cu.ft. of chamber volume. My chamber is 65cu.ft. so does that mean =
=3D
I need to generate up to 975,000btu's over a certain amount time from the h=
=3D
obs opening area or at the throat arch, like it was a giant nozzle on an at=
=3D
mospheric gas burner? =3D0A=3D0A I just got it figured out that the area of=
my =3D
throat arch is 153sq." and the open area of the hobs above the ash pile is =
=3D
now 760sq.". The inside of the Bourry is 29" high by 26.5" long x36" wide s=
=3D
o it will hold about 16.5 cu.ft. of wood and now last a lot longer to where=
=3D
I can adjust the kiln to my sleep routine. What all the math means doesn't=
=3D
matter much because I did get the kiln real hot up front twice so the only=
=3D
problem is soaking the heat in front to back, or take the zones as they ar=
=3D
e and fire ^4-^6 in the tail, ^6-^8 in the mid-tail, and ^8-^10 in the mid-=
=3D
front. Glad I have a sack of Gerstly Borate to add to some glazes to knock =
=3D
them down a cone or two. =3D0A=3D0A If I did my exit flue math correct as i=
t le=3D
aves the chamber it is about 48sq." opening to a roughly 14"x17" collection=
=3D
area and tapering to 9"x9" at about 10" and on up to 14".=3D0A=3D0AGary Na=
varr=3D
e=3D0ANavarre Pottery=3D0ANavarre Enterprises=3D0ANorway, Michigan, USA=3D0=
Ahttp://=3D
www.youtube.com/GindaUP=3D0Ahttp://public.fotki.com/GindaUP/=3D0A=3D0A=3D0A=
--- On S=3D
at, 9/4/10, douglas fur <23drb50@GMAIL.COM> wrote:=3D0A=3D0A> From: douglas=
fur=3D
<23drb50@GMAIL.COM>=3D0A> Subject: Re: [Clayart] damper placement/chimneys=
=3D
=3D0A> To: Clayart@LSV.CERAMICS.ORG=3D0A> Date: Saturday, September 4, 2010=
, 3:=3D
57 PM=3D0A> Jonathan=3D0A> "Also, I am interested in learning a little more=
abo=3D
ut=3D0A> chimney sizing=3D0A> for wood kilns"=3D0A> I agree-=3DA0 Gary's po=
st refer=3D
s to Leach which is what=3D0A> Olsen uses. Leach gives=3D0A> his source as =
an E=3D
nglish engineer and Matsubayashi all of=3D0A> which is based on=3D0A> dense=
fir=3D
e brick.=3DA0 What should we use for IFB or=3D0A> Fiber?=3DA0 Olsen gives h=
eat=3D0A=3D
> requirements for IFB @ 10,000btuh/ cubic foot and DFB @=3D0A> 15,000 btuh=
/C=3D
u.Ft.=3D0A> of kiln capacity.=3DA0 So would a IFB kiln need a chimly=3D0A> =
area 2=3D
/3 the cross=3D0A> section recommended by Leaches DFB guidelines or 2/3 the=
=3D
=3D0A> height or 2/3 of=3D0A> both dimensions.=3D0A> =3D0A> I fired a sweet=
firing =3D
27 cuft IFB kiln built by Bruce.=3D0A> Finch. It's chimney=3D0A> section wa=
s 7.=3D
5"X7.5". The height was just to the top of=3D0A> the arch.=3DA0 In a=3D0A> =
simila=3D
r DFB kiln=3DA0 I'd expect to see a 9"X9" chimney at=3D0A> least 12 feet ta=
ll.=3D
=3D0A> Which comes to a crossection size 69% of DFB and a height=3D0A> at a=
bout=3D
50-60%.=3D0A> =3D0A> =3D0A> =3D0A> DRB=3D0A> Seola Creek=3D0A> =3D0A=3D0A=
=3D0A
douglas fur on wed 15 sep 10
gary
My chamber is 65cu.ft. so does that mean I need to generate up to
975,000btu's
*yes but that number's more useful i fyer using gas or oil...*
**
What all the math means doesn't matter much
*true, it's the kiln ya gotta learn to live with but the numbers are useful
to compare your kiln with a theoretical kiln to see if anything stands out
as exceptional. I did the numbers (based on Leach and Cardew) for a
theoretical kiln about 4'-41/2" dia. The volume of the firebox, the area o=
f
the opening at the level of the hobs are good- bigger than theoretical. th=
e
throat area is right on the th.- considering the oversize of the above it
might want to be bigger. The chimney is shorter than theory- maybe an 8 ft=
.
piece of 10" dia culvert on top... but *
If I did my exit flue math correct as it leaves the chamber it is about
48sq
*This one sticks out. 48 si =3D6"x8" about 1/3 of theoretical I would expec=
t
more like 10"x 12" or 12.5" X 13.5"*
*Check it out*
*DRB*
*Seola Creek*
>
> Gary Navarre
> Navarre Pottery
> Navarre Enterprises
> Norway, Michigan, USA
> http://www.youtube.com/GindaUP
> http://public.fotki.com/GindaUP/
>
>
> --- On Sat, 9/4/10, douglas fur <23drb50@GMAIL.COM> wrote:
>
> > From: douglas fur <23drb50@GMAIL.COM>
> > Subject: Re: [Clayart] damper placement/chimneys
> > To: Clayart@LSV.CERAMICS.ORG
> > Date: Saturday, September 4, 2010, 3:57 PM
> > Jonathan
> > "Also, I am interested in learning a little more about
> > chimney sizing
> > for wood kilns"
> > I agree- Gary's post refers to Leach which is what
> > Olsen uses. Leach gives
> > his source as an English engineer and Matsubayashi all of
> > which is based on
> > dense fire brick. What should we use for IFB or
> > Fiber? Olsen gives heat
> > requirements for IFB @ 10,000btuh/ cubic foot and DFB @
> > 15,000 btuh/Cu.Ft.
> > of kiln capacity. So would a IFB kiln need a chimly
> > area 2/3 the cross
> > section recommended by Leaches DFB guidelines or 2/3 the
> > height or 2/3 of
> > both dimensions.
> >
> > I fired a sweet firing 27 cuft IFB kiln built by Bruce.
> > Finch. It's chimney
> > section was 7.5"X7.5". The height was just to the top of
> > the arch. In a
> > similar DFB kiln I'd expect to see a 9"X9" chimney at
> > least 12 feet tall.
> > Which comes to a crossection size 69% of DFB and a height
> > at about 50-60%.
> >
> >
> >
> > DRB
> > Seola Creek
> >
>
>
>
>
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