That is not what the paper is saying.
I understand that a piece of lumber once dried (from green to dry) and taken to my shop will then equalize (swell/shrink) to the relative humidity in my environment. If I use the USDA table from my post (#35) I can get at least a rough idea of the moisture change (%EMC) that that "dried" piece will undergo in one year at my location. The highest percent minus the lowest percent is the amount of annual change (Amc in the equation).
I'm sorry, I missed the link in that series of images. Yes, the paper is saying roughly what I am saying - that the green to dry figures (which ironically are listed in their appendix III) only imply the expected change in use of seasoned wood. At the bottom of page three, the author says "In the case of sugar maple, for example, a change of 6 percent in the moisture content may result in a dimensional change in a furniture part of about 2.5 percent."
If you looked at a green-dry table you would expect on the order of 5% to 9% the way most people seem to view these tables. The table is basically not reporting the EMC changes seen in typical use and people assume that you will see that full 5%-9% swing from summer rain season to winter dry season. The EMC is actually changing by only 10% or so at worst (also reported in the introduction of the article).
Maybe not exactly relating to the point, but why do you assume that we don't use green wood for furniture?
Yes, there is one specialized application in the entirety of the furniture trade over the centuries of history of making furniture. I don't know much about it because it is not much to my taste, and being a hobbyist I can happily ignore the stuff I don't much care for. Come to think of it, I think Windsor chairs also take advantage of the green to dry shrinking to hold spindles tight in the seat, but again I don't know much about it.
The seasonal differences shown in the USDA table (post #35) for "dried" wood are obviously less than the differences of green minus dry. The "Green to Oven Dry" differences are in fact shown in the table titled "Appendix III" (again post #35). Note that the main title is "Shrinkage Coefficients for Selected Woods". The appropriate value (SC) is selected and used in their equation to calculate the width change of a "dried" board.
I typically see people posting the green-dry type tables and saying something like "you'll see 5-10% dimensional change, according to the table" without realizing that the EMC of seasoned wood in use is a much smaller range and will show a much smaller dimensional change - on the order of 1-3%. Since you seem to get this, I kinda wonder what we are debating? You seem to understand here that they were using one metric to estimate another. I'm simply saying that this leads the casual viewer to mistake in his estimation because of the gritty details of mathematics one must go through are typically buried in an appendix somewhere.
BTW "furniture drawers that won't open in July" don't "go back to the proper size in the fall/winter". If they were the "proper" size to begin with they would operate smoothly year around.
Sure, perhaps I should have said "normal size" or "size as constructed". Proper in this case is not used to mean "correct" so much as "median" and is only a sloppy bit of idiomatic english intended to make the sentence read more easily. While a well constructed piece will not have this problem, it certainly is common enough that most people have experienced it (which is why I use it as an example).
First, is the Purdue University paper correct in calculating the "realistic" values you mention? If not then what is incorrect? The coefficients used, the equation? If you know the absolute correct way then please post.
Correct in what sense? Calculating an expected trend based on %RH alone, which is taken as an estimate for seasoned wood changes in general (as in not specific to grain orientation or species)? If so, then yes, it is correct.
The dimensional change figures quoted in the green to dry table are not used in the equation listed in appendix II - that one only has temperature and %RH as variables.
The equation is without a doubt determined through experimentation, but it is also only a general equation. A more interesting way to do it would be to measure changes by species and grain orientation and then derive new equations for each. I would guess that the general equation would remain the same, but the constants would vary. I have never seen it done this way (as I've said before), except in one case (on some other hobbyist's website) where I expect he did not allow sufficient time for equilibration.
Second, how would you construct the table? What would the row and column headings be?
Which table? The one in Appendix III? There is nothing wrong with it at all, it is simply concerned with a different topic than the one the author is discussing. He's not talking about dimensional changes green-dry, so the table is not relevant.
A relevant table would have the same rows and columns but the data & title would reflect the changes from about 6% EMC to 15% EMC. If I remember correctly, above 15-16% EMC you are actually getting free water back in the wood cells, as in you would have to soak it in water - which is a different environment that picking up atmospheric moisture from humid air.
