Dear hannsf-ga;
Thank you for allowing me to answer your interesting question. I?m
afraid what you are looking for isn?t going to be nearly as easy as a
single table that lists the drying rates of all species of logs. There
are far too many variables to consider and one has to do some fancy
elbow work to come to the most accurate conclusion. Hopefully what I
have provided for you here will greatly decrease the amount of work
you have to do on your own to calculate the drying rates.
The equilibrium moisture content of living vs. non-living wood varies
from one another as much as it does from one species to another. The
type of cut, thickness, length, and circumference, etc. of the wood
will also play a major factor. More importantly, the environment in
which the wood is stored is a major factor as well, and will affect
the drying rate calculations of any species, cut, thickness or
viability (living vs. non-living) woods. The moisture content of wood
is directly related to the humidity and temperature of the surrounding
air so the drying time would depend on the environment as much (or
possibly more) as any other factor.
The best you can hope for in your search for a solution is an EMC
(equilibrium moisture content) calculator, mathematical formula and
shrinkage tables. Here is one such tool for non-living, (natural or
cut) wood. It was created using information obtained from the U.S.
Forest Products Laboratory:
Wood Equilibrium Moisture Content Table And Calculator
http://www.csgnetwork.com/emctablecalc.html
(The mathematical formula is included)
Here is another very similar one:
WOODBIN: COMPUTING MOISTURE CONTENT OF WOOD
http://www.woodbin.com/ref/wood/emc.htm
The rate of drying is also known as ?moisture loss per day?. This is
measured by ?shrinkage?. Here are some shrinkage tables in case they
are of any use to you also.
WOODBIN: SHRINKAGE CALCULATOR
http://www.woodbin.com/calcs/shrinkulator.htm
Domestic wood shrinkage values by species
http://www.geocities.com/windyhilllogworks/shrinkagevalues0001.JPG
Moisture content of green wood by species
http://www.geocities.com/windyhilllogworks/Shrinkage10001.JPG
You will also find some very interesting (and frankly, complicated)
mathematical wood drying formulas in this document from the US
Department of Agriculture. Also included are some very informative
tables related to EMC at various times of the year and in various
regions of the world:
EQUILIBRIUM MOISTURE CONTENT OF WOOD IN OUTDOOR LOCATIONS IN THE
UNITED STATES AND WORLDWIDE
http://www.timberframe.org/fileuploads/Equilibrium_Moisture_Content.pdf
Just when you think you might be on the right track to finding
valuable information, my goodness, it becomes complicated indeed. Here
are a number of tables that outline moisture contents by species, by
electrical resistance along the grain, and other factors courtesy of
Purdue University, Department of Forestry & Natural Resources.
FORESTRY AND NATURAL RESOURCES
http://www.ces.purdue.edu/extmedia/FNR/FNR-155.html
I hope you find that my research exceeds your expectations. If you
have any questions about my research please post a clarification
request prior to rating the answer. Otherwise I welcome your rating
and your final comments and I look forward to working with you again
in the near future. Thank you for bringing your question to us.
Best regards;
Tutuzdad-ga ? Google Answers Researcher
INFORMATION SOURCES
Defined above
SEARCH STRATEGY
SEARCH ENGINE USED:
Google ://www.google.com
SEARCH TERMS USED:
EQUILIBRIUM MOISTURE CONTENT
DRYING
LOGS
WOOD
SHRINKAGE
FORMULA
TABLE
CALCULATOR |
Request for Answer Clarification by
hannsf-ga
on
22 Apr 2005 09:41 PDT
Tutuzdad-ga:
Thank you for your rapid response to my question. Thank you for the
references and insight, however I note that your answer does not
address the problem which is; The drying rate between Green moisture
content and the Fibre Saturation Point and/or EMC. Your information
is great for calculating what the EMC will become, but doesn't tell me
the rate at which logs lose moisture from the green MC (sapwood can be
from 75% to over 125% MC) through the Fibre Saturation Point (~30%MC)
to finally achieve EMC.
Sorry, I should have made my initial request clearer.
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Clarification of Answer by
tutuzdad-ga
on
22 Apr 2005 10:32 PDT
Take a look at this document f rom the Oklahoma Cooperative Extension
Service. There are two tables about midway down the page that show the
average air drying time for various species (to achieve EMC) and a
relative humidity EMC values chart.
PRACTICALITIES IN DRYING LUMBER
http://pearl.agcomm.okstate.edu/forestry/general/f-5042.html
Let me know if this proves valuable to you.
tutuzdad-ga
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Request for Answer Clarification by
hannsf-ga
on
22 Apr 2005 11:51 PDT
Dear tutuzdad-ga:
Thanks for this, however it deals with air drying of lumber which is
quite different than logs, with bark on, in piles. Also, I'm not sure
if it is a straight line decrease in MC/time (I suspect that loss of
moisture is greater at start and then less as log approaches FSP). I
notice that many of the measurements, in table 1, vary by an order of
magnitude which doesn't help me much.
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Clarification of Answer by
tutuzdad-ga
on
22 Apr 2005 12:37 PDT
Wow. It may be that what you are looking for doesn't exists in the
broad spectrum. Maybe you can tell me what species and I will try and
find the rate for that particular wood.
tutuzdad-ga
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Clarification of Answer by
tutuzdad-ga
on
22 Apr 2005 12:43 PDT
For example:
ESTIMATING AIR DRYING TIMES OF SMALL-DIAMETER PONDEROSA PINE AND
DOUGLAS-FIR LOGS.
http://www.woodweb.com/knowledge_base/fpl_pdfs/fplrp613.pdf
tutuzdad-ga
|
Request for Answer Clarification by
hannsf-ga
on
22 Apr 2005 13:24 PDT
Dear tutuzdad-ga:
Your find on the air drying times of Ponderosa and Douglas-Fir logs is
right on the mark. This would be suitable for a 2 star rating. If it
is possible to find information, of the same type, on Aspen (I'm also
looking for info on Lodgepole Pine, Balsam, Basswood, Birch and
Tamarack = bonus) then I think this would be a 5 star answer, thanks!
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Clarification of Answer by
tutuzdad-ga
on
22 Apr 2005 13:51 PDT
Ok. Please allow me a bit to see what I can come up with.
Dad
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Clarification of Answer by
tutuzdad-ga
on
22 Apr 2005 18:24 PDT
Because, I suspect, of the abundant technology, there just doesn?t
seem to be a whole lot of information out there about air-drying
nowadays when kilns, microwave and solar devices are becoming more
popular.
One of the best ones I can manage to find is probably more relative to
lumber than poles, trees, or fresh felled timber, but it gives a great
idea of the drying times of various species of wood.
WOODWEB: ESTIMATES OF AIR DRYING TIMES -- FOR SEVERAL HARDWOODS AND SOFTWOODS
http://www.woodweb.com/knowledge_base_images/zp/estimates_of_air_drying_times.pdf
This one also pertains primarily to lumber but has some serious
mathematical equations that may be of interest to you and applicable
to timber.
METHOD FOR ESTIMATING AIR DRYING TIMES OF LUMBER
http://www.fpl.fs.fed.us/documnts/pdf2001/simps01c.pdf
( I found the article here: http://www.laymar-crafts.co.uk/linkr.htm )
Unfortunetly, search as I might, I have been unable to discover any
other documents similar to the one I provided you with earlier. Having
said that, I may have to accept whatever rating the information I have
supplied will earn me, though I have tried diligently for hours now to
find more satisfactory data.
I do think that you may have some success by contacting the AMERICAN
WOOD PRESERVERS ASSOCIATION as inquire with them about any published
data they may have on the subject. I cannot be certain but I suspect
that they may be able to help you further.
AMERICAN WOOD PRESERVERS ASSOCIATION
P.O. Box 388
Selma, AL
36702-0388
USA
Telephone: 334-874-9800
Facsimile: 334-874-9008
Email: mailto:email@awpa.com
Site: http://www.awpa.com/
I hope this earns a decent enough rating in spite of our mutual
disappointment in the lack of data available on the subject.
Regards;
Tutuzdad-ga
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