AJH wrote:
On Fri, 28 Mar 2008 18:27:13 +0000, Andy Wade
wrote:

Most woods will float in water so the density must be less than
one tonne per m^3.

That's right for a solid cubic metre, chop it into a jumble of logs
and the bulk volume doubles.

IIRC for most species it's in the range 600 - 750
kg/m^3 - hardly "a few tonnes."

Green densities are around a tonne for a solid cubic metre for oak and
beech but that contains about 47% water.

At 20% MC your 500 litres comes down to
120 - 150 litres in reality.

As above, a 2 cubic metre heap of chopped, green logs will contain
about 500litres of water, you need to drop that to 25%mc wwb to avoid
most microbial activity, that's about 155 litres remaining. Aside from
any water formed by respiration of dry matter this 345 litres of water
has to leave carried away by air and that air has to provide the heat
to change the state of the water from liquid to vapour.

No heat is required: All that is required is that the air is not
saturated with water.

At 20C
saturated air can carry about 20 grammes of water per m^3, with
natural draught and our humidity I'll doubt you can get within half
that and a stack off logs won't have good circulation. It looks like
about 34k m^3 of air needs to move through the logs. Say the volume
passed by a psu fan for 33 days when humidity is low and temperatures
are above 20C. With the caveat that the logs have to be chopped small
enough for the interior to remain at equilibrium with the surface
during that time.

That doesn't happen. Logs dry out on the surface first, and then a
gradient is set up. The initial dry is quite rapid - days only..its
getting the core water out that takes the time, hence the need to plank
and stack.

All that is required really is to find a place where the air is
unsaturated, and stays that way. Kiln drying works to speed this up, but
its not essential, and arguably doesn't actually do any more than
rapidly reduce the overall humidity of the wood, the actual achievement
of equilibrium happens later over time. Fresh kiln dried wood is still
highly prone to movement afterwards.

For that reason its unlikely that unheated wood will dry properly in
less than a year or so, not for joinery purposes anyway.

At which point the required air movement is far far less.

AJH