Am going to be starting up a solar kiln for the first
time in a week or two, and have some general questions ...
The kiln is based on the Virginia Tech plans, and
has a 6 X 14 footprint.
From my reading of Gene's many articles/responses
on drying, the goal is to dry the lumber as
quickly as practical without exceeding the recommended
MC loss per day for the given species.
Typical pile I'll be working with will be 4 feet
wide and 8 or 10 long, with the height determined
by using an optimum board footage value to collector
size/ratio that will hit the target drying rate
for the given species.
There are three fans, with high/med/low settings.
My reading indicates that air movement has the
greatest effect during the early/high MC stage
of drying, which I read as meaning that the air
velocity is most effective when removing the
free water, and as the lumber approaches 30% to 20%
MC, the air velocity is far less important.
Assuming the above is true:
Question 1 - fan speed:
Is there any merit to running the fans at high until
the MC is below 30%, and then switching to low(er)
speeds, or should they just run on high all the time?
Question(s) 2 - setting vent openings:
How does the vent opening size come in to play?
Should the amount the vents are opened be determined
by monitoring MC loss? In other words, if the rate
of drying is happening too quickly, should the vents
be choked down to reduce the drying rate? Or ... is
the vent opening determined by outdoor temperature?
Wide open in hot months, choked down in cooler weather?
I have found very few references to how the vent
openings should be manipulated during the drying
process - any insights would be appreciated.
I have six vents - 3 upper, 3 lower, with each vent
providing a 1 sq/ft opening.
Question 3 - weighting the pile:
Is weighting the top of the pile as beneficial
when kiln drying as it is when air drying?
First load in the kiln will be 4/4 white ash.
The plan is to get the logs sawn and in the kiln
as quickly as practical after dropping the
tree(s) and end coating the logs.
The VT kiln documentation lists the max MC loss
per day for white ash at 10.4%. The collector area is
120 sq/ft, and my plan is to load the kiln with about
350-400 bd/ft and monitor. From the VTech literature,
and given that we're approaching the high temperature
and maximum sunlight period, it appears the this
load could be dried in somewhere between a
week or two.
All responses appreciated