Frank Colson on sat 2 jul 05
Downdraft kiln construction always appear to be a subject for
consideration. One basic factor about all downdraft kilns, is they require a
"stack". A stack, of course is the life pulse for creating a draft which
draws heat through that kiln.
In almost all cases when it comes to a decision for placing or making a
stack, be it brick by brick, or using fireplace liners, culverts, or
whatever, it ends up being a matter of simple brunt force the time of
installation . The higher the stack, the more effort is required.
I have stacked "stacks" on kilns from New Zealand, to Peru, Mexico,
Vancouver, and beyond; always with duress. However, I must confess,
that was many, many years ago.
Today, there exists stack units in 12" heights, with an ID (inside diameter)
of 12". Wall thickness is 1/2", and heat tolerance of these compressed
ceramic fiber cylinders, runs in excess of 2000 degrees F. This is with no
expansion or contraction . One unit weighs 3 pounds!
So, if I want a 10 foot high stack, I am dealing with a total of a little
more than 30 lbs. 60 lbs. for twice that height. Engineering the procedure
of installation and weather protection is extremely simple. I purchase a
roll of thin aluminum sheeting, one foot wide, cut lengths 1" longer than
the circumference of my cylinder OD (outside diameter). I make a 1/2" back
folded crease, at each end, lock the sheet into a sleeve which
is slid over the outside of each stack unit. Every unit now weights almost
3+ lbs with the weather protected aluminum sleeve . After placing each unit
ontop each other to the desired height, 10',12',15', whatever, a 2" wide
metal band is screwed around half of the bottom and top end of every
cylinder. Several of these bands have a tri-point (3 point triangle) screw
eye protruding outward from which a guide line is attached
and anchored to an extended hook several yards away. Think of it this way.
Sail boats have lines attached to the main sail from other areas on
the boat deck. One tip is to have the stabilizing lines a little slack, not
taunt. Another tip is to use sail boat stainless lines for anchoring the
stack. Last year we had not 3, but 4 hurricanes blow through Florida.
Never once did I lose the light weight stacks installed on my two
updraft kilns ! Those stacks have been in place for years!
Frank Colson
www.R2D2u.com
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